UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary 

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director 

Professional Paper 200 

GEOLOGY -AND ORE DEPOSITS OF THE 

MAGDALENA MINING DISTRICT, NEW MEXICO 

BY 

G. F. LOUGHLIN AND A. H. KOSCHMANN 

Prepared in cooperation with the 

STATE BUREAU OF MINES AND MINERAL RESOURCES 

~EW MEXICO SCHOOL OF MINES 

UNITED STATES 

GOVERNMENT PRINTING OFF{CE 

WASHINGTON : 1942 

For sale by the Superintendent of Documents, Washington, D. C. - - - - - - - - - - Price $2.00 
• 
-CONTENTS 

Abstract __________________________________________ _ 

Introduction __________________ ~--------------------

Field work and acknowledgments ________________ _ Bibliography ____ ______________________________ _ 

Geography ________________________ ____________ _ 

Location of the area ________________________ _ Relief ____________________________________ ~ 

Valleys and drainage _______________________ _ 

Climate __________________________________ _ 

Vegetation ________________________________ _ 

GeologY---------------------------- -------------- Pre-Cambrian rocks ____________________________ _ 

Argillite ("greenstone") and schist_ __________ _ 

Distribution and structure ______________ _ Lithology _____________________________ _ 

Gabbro____________________________________ • 

Distribution and occurrence ______________ _ 

Lithology ______________________ ________ _ 

Felsite __ ____________________________ ______ _ 

Distribution and occurrence _____________ _ . Ltlhology _____ __________ ______ ________ _ 

Granite ______________________________ ~ ____ _ 

Distribution and occurrence _____________ _ 

Lithology ___ .. _________________________ _ 

Chemical composition and classification ___ _ Diabase ____ ______ __________ __ _________ ____ _ 

Distribution and occurrence ___ __________ _ 

Lithology ________ _________ ___ ___ -' _____ _ 

Biotitization of the pre-Cambrian rocks ____ :_ __ _ Correia tion _______________________ ________ _ 

Carboniferous system, by V. T. Stringfield, A. H. 

Koschmann, and G. F. Loughlin _________ ______ _ 

Kelly limestone (Mississippian) ________ . _____ _ 

. Distribution ______ ,.. _________________ ___ _ 

Age and correlation ____________________ _ 

Magdalena group (Pennsylvanian) ___________ _ 

Sandia formation __________ ____________ _ 

Lower quartzite member ____________ _ 

Lower limestone member ___________ _ 

Middle quartzite member ___________ _ 

Shale member _______________ _____ _ _ 

Upper limestone member ________ .. __ _ 

Upper quartzite member ____________ _ 

Madera limestone _____ _________________ _ 

Age of the Magdalena group _____________ _ 

Abo sandstone (Permian) ___________________ ____ _ 

Tertiary (?) sedimentary rocks ______ ____________ _ 

Quaternary system _________________ ____________ _ 

Landslides __ _________________ ____ ___ ____ __ _ 

Alluvium __________ : ______________________ _ 

Talus_ t _______ . ___________________________ _ 

Tertiary (?) effusive igneous rocks _______________ _ 

General statement _________________________ _ 

Lower latite tuff _________________________ __ _ 

Lower andesite __________________________ __ _ 

Upperlatite ____________ __ _________________ _ 

Purple andesite __________ ~ ____________ ~ ____ _ 

Banded rhyolite ________________ ___________ _ 

Red andesite ______________________________ _ 

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Geology-Continued. 

Tertiary (?) effusive igneous rocks-Continued. 

Red rhyolite _____________________________ - _ 

Upper andesite __________ ~ _______ __________ _ 

Pink rhyolite ____________________ __________ _ 

White felsite tuff __________________________ _ 

Tertiary (?) intrusive igneous rocks ______________ _ 

General statement__. ______ -.- ______ _________ _ 

Latite porphyry ___________________________ _ 

Latite dikes _______ ~ _______________ - _- _--- _-

Rhyolite porphyry ___________________ - _- _---

Typical facies _____________ .. ___________ _ 

Magnetic facies ____________ ~ ________ - -· __ 

Hornblende andesite _______________________ _ 

Augite andesite ____________________________ _ 

Monzonite group __________________________ _ 

Typical facies ____________________ _____ _ 

Other facies ___________________ -_-------

Chemical com position and classification __ .. _ Tertiary (?) granite __________________ __ _____ _ 

Distribution and occurrence _____________ _ 

Lithology __________________ ____________ _ 

Aplite dikes ________________ ----- ---:..-------

Pegmatitic materiaL _______________________ _ 

Granophyre _______ __ ~--------- ------------

Hybrid granophyre _______ ______ -: _____ ~- ___ -

Pitchstone ________ ____ __ __________ ________ _ 

Lamprophyre dikes_ _ _ _ _ _ ___ _____ ____ - __ - -

White rhyolite ______ ______ ______ __________ _ 

Differentiation ______________ ______ ________ _ 

Rock alteration and its significance ____ -- _____ ___ _ 

Summary and conclusions __________________ -

Alteration near intrusive contacts __ __________ _ 

. Alteration of pre-Cambrian rocks _____ ____ _ 

Alteration of shale _____________________ _ 

Alteratior1 of limestone _________________ _ 

Marbleization ____________ _________ _ 

Silica tion _________________________ _ 

Alteration far from intrusive contacts __ :. _____ _ 

Alteration in the northern area __ _ -' ___ ~ __ _ 

Alteration in the southern area ______ ____ _ 

Silicification _______________________ _ 

Hematitization ___ · _______ __________ _ 

Alteration to clay minerals and celadonite------------------- ---- --- Structure ________________ ____________ _____________ _ 

Summary of deformation _______________________ _ 

Pre-Cambrian structure _______ ·-..: _______________ _ 

Paleozoic and Mesozoic s;tructure ____ ____________ _ 

Laramide and Tertiary structure __ .:_ ______________ _ Folds ___________ ___ _______ ________________ _ 

Faults ___ ____ _____ _ ·_______________________ _ 

Faults south of the Nitt stock ___________ _ 

East-dipping longitudinal faults _____ _ 

Germany fault zone ____________ _ 

Stonewall fault zone ____________ _ 

Crest fault ________ ~------------

Other east-dipping faults _______ _ 

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• 
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IV CONTENTS 

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Structure-Continued .. 

Laramide and Tertiary structure-Continued. 

Faults-Continued. 

Faults south of the Nitt stock-Continued. 

Vertical or steeply dipping longitudinal 

faults___________________________ 60 

Kelly-Graphic fault_____________ 60 

Mistletoe fault _________________ • 61 

Young America fault----~------- 61 

Grand Ledge fault______________ 61 

East Slope fault_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 61 

Waldo· fault_ ________________ ~__ 62 

Faults between Kelly and South 

Camp____________________ __ _ 62 

Transverse faults_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 62 

Bedding faults _________ _ . _ _ _ _ _ _ _ _ _ _ _ 63 

Faults north of the Nitt stock____________ 63 

Faults within Tertiary (?) granite____ 64 

Vindicator fault____________________ 64 

Stendel fault________ _______ ________ 64 

Faults in the Granite Mountain area______ 65 

Interpretation of L_aramide and Tertiary structure ____________________________________ .. 65 

Deformation before volcanic eruptions____ 66 

Deformation between the first and second 

stages of volcanic activity______________ 66 

Deformation after the second stage of volcanic activity ____ ._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 68 

Local faulting during the intrusion of stocks_ 69 

Minor adjustments after stock intrusion but 

before ore deposition______________ _ _ _ _ 71 

Minor a.dju,stments after ore deposition____ 73 

Physiographic development ____________________ _ .. 73 

0re deposits_______ _______ ___ __________ __ ____________ 75 

Historical sketch _________ ___ .... _________ __ ____ . _ _ 7 5 

Production_________ ____________ __ ______________ 82 

Minerals of the Magdalena district, by S. G. Lasky 

and G. F. Loughlin_______ _______ ______________ 87 

Iron minerals_______________ ___ ________ _____ 90 

Sulphide zone __ _ .________ __________ _ :.. _ _ _ 90 

Specularite and magnetite ____ __ -.-_ __ 90 

Pyrite________ _____________ __ ______ 91 

Pyrrhotite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 91 

Oxidized zone_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 91 

Limonite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 91 

Jarosite or natrojarosite _ _ _ _ _ _ _ _ _ _ _ _ _ 92 

Melanterite_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ __ _ _ 92 

Zinc minerals__________ ________ ___ ___________ 92 

Sulphide zone ___ ____________ . _ _ _ _ _ _ _ _ _ _ 92 

Sphalerite (zinc blende)_____ ________ _ 92 

Oxidized zone_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 92 

Smithsonite _______ __ . _____ . _ _ _ _ _ _ _ _ 92 

Hydrozincite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 93 

Aurichalcite___ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ 93 

Chalcophanite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 93 

Hemimorphite (calamine)___ _________ 94 

Willemite__ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ __ _ _ - 94 

Goslarite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 94 

Zinc-bearing clay or "tallow clay" ___ . 94 

Copper minerals____________________________ 94 

· Sulphide zone (hypogene)________________ 94 

Chalcopyrite ___ :_ ___________________ 94 

Bornite____________________________ 95 

Sulphide zone (supergene)_______________ 95 

Chalcocite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 95 

Covellite _____ .,____________________ _ 95 

Ore deposits-Continued. 

Minerals of the Magdalena district-Continued. 

Copper minerals-Continued. 

Oxidized zone _________________________ _ 

Malachite _________________________ _ 

Azurtte ___________________________ _ 

Chrysocolla _____________ .. ________ :. _ 

Native copper _______ : _____________ _ 

Cuprite ___________________________ _ 

Tenorite ______ _, ___________________ _ 

Chalcanthite ______ ________________ _ 

An tleri te ______ .. _________________ . __ 

Span go lite _____ ___ _____ ·- __________ _ 

Cyanotrichtte _______________ ------~-

Lead minerals ___________ - ___ - ___ --_- ___ - _---

Sulphide zone ___ .. _____ - _ .. __ .. - _ .. _- _--- - - Galena ___________________________ _ 

Oxidized zone _________________________ _ 

Anglesite _________________________ _ 

Cerussite _______________ - _________ -

Plumbojarosite __ __________________ _ 

Vanadinite ________________________ _ 

Silver minerals __________________________ - __ 

Sulphide zone (hypogene) ____ __ _________ _ 

Sulphide zone (supergene) _______ .. ______ _ 

Argentite (?) _______ ___ _____ ______ --

Native silver _______ ___ _______ _____ _ 

Oxidized zone ___________________ .. ____ .. 

Cerargyrite ___________ ________ . ____ _ 

Native gold __________ :_ ________ ______ ______ _ 

Manganese minerals _____ ___________ ____ ____ -

Sulphide zone _________________________ -

Oxidized zone _________________________ _ 

Pyrolusite, psilomelane, and wad .. ___ _ 

Cadmium mineral greenockite _______________ _ 

Gangue minerals __________ ___ __ ____ ________ _ 

Tourmaline _______________ . ___________ _ 

Wollastonite _____________ .. ____ __ ____ __ _ 

Andalusite _______________ - __ -- -- .. -------

Diopside ______________________________ _ 

Hedenbergite _________________________ --

Tremolite and actinolite ________________ _ Garnet _______________________________ _ 

Epidote ________________ -'·· _________ ~ __ _ 

Serpentine (antigorite) _________________ _ 

Quartz __ ~----------------------------- Serictte _______________________________ _ 

Chlorite ___ __ _______ ___ ___ _ ~ __________ . 

Thaumasite ______________ . _____ .. _______ _ 

Sidertte ____________ __ _______ ________ __ _ 

Dolomite ___________ .. ___ ___ ___ __ __ ____ _ 

Calctle _______________________________ _ 

}u·agonite _____________________________ _ 

Barite ___________________ _____________ _ 

Fluorspar_ _____________ ______ - -- __ --- --

Clay minerals ___________ _________ _____ _ 

Celadonite ___________________ __________ _ 

Distribution and classification of mineral -deposits __ _ 

Deposits formed at high temperatures _____ _______ _ 

Deposits formed at moderate temperatures _________ _ 

Large barren quartz veins in igneous rock ____ . _ 

Sulphide deposits __________________________ _ 

Hotter mesothermal ores ____________ . ___ _ 

Iron and copper (pyritic) ores ________ · 

Zinc blende, galena, and mixed sulphide ores ________________ ___________ _ _ 

Cooler mesothermal (leptothermal) ores __ _ 

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ILLUSTRATIONS 

Ore deposits-Continued. Mines-Continued. 

Deposits formed at low temperatures______________ 110 Mines m the main ore zQlle-Continued. 

Genesis of original (hypogene) ores ______ _________ . __ .. 111 ' Black Cloud and Mistletoe mines ____ .. _______ _ 

Processes in limestone __ ~____________________ 111 Young America, Imperial, and Enterprise claims_ 

Early, silicate-forming stages_________ __ _ 111 Linch burg tunneL ___________ .. _______ ______ _ 

Specularite-magnetite stage_ _ _ _ _ _ _ _ _ _ _ _ _ _ 111 Woodland mine __ ___ ______________ __ ___ .. ___ _ 

Ore-forming stages______________________ 112 Cavern and Grand Ledge mines _____ ________ _ 

Processes in igneous rocks_ ________________ _ _ _ 113 Connelly tunneL __________________ ~ _______ _ 

Oxidized ores_______ _____ ___ ___________________ 115 West Virginia tunnel _________ ___ __________ :... _ 

Oxidized iron and iron -manganese ores _____ .. _ _ 115 Victor tunneL ________________ __ __ ______ ___ _ 

Lead carbonate ores__ _____ ___ _______ _____ __ _ 116 Mines and prospects east of the main ore zone _____ _ 

Zinc carbonate ores_ ___ ___ ____ __ ___________ _ 116 

Oxidized copper ores __________ ~--- ------ ---- 117 

Sampson claim ______ __ ______ ____________ __ _ 

Grand Tower and Legal Tender claims ___ ___ _ _ 

Oxidized gold ore _____________ _____________ 117 Germany mines ___ _ . ___________ _ :. __________ . 

Oxidized silver ore ___ ___ .:. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 118 Little Loella claim _______ __ __ __ ____ _______ . _ 

Zones of alteration __________ ___ ________ __ _ _: _____ 118 Tip Top and Key mines ____________________ _ 

Processes of alteration____ __________ __________ ____ 120 Stonewall tunnels __________________________ _ 

Alteration of country rocks___ ____ ___________ 120 Ambrosia mine ______ :.. ____________________ . __ . 

Alteratioh of sulphide ores _______ · _____ ____ ___ · 121 Sleeper tunneL ___________________ · _________ _ 

Solution of primary sulphides ________ :...___ 121 Prospects west of the main ore zone _____________ _ _ 

Redeposition as products of oxidation ___ ... _ 121 Mines north of the N itt monzonite stock _________ _ 

Zinc carbonate stage________________ 121 Hardscrabble mine _________________________ _ 

Iron-manganese oxide stage__________ 122 Anchor mir.e __________________ ·- ___________ _ 

Lead carbonate stage________ ________ 122 Vindicator mine ___________________________ _ 

Final base-me~al stages____ _ _ _ _ _ _ _ _ _ _ 122 Outlying prospects _____________________________ _ 

Precious metal stage_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 123 Cavalier claiJ;n __ .. __________________________ _ 

Mines ____________ .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 123 Magnetite on Medley ranch _________________ _ 

Mines in the main ore zone______________________ 123 

Nitt mine ___ .._ ______ ---- -··---~--- ---- ------ 123 

Graphic-Waldo or Ozark mine ___ -------_____ 124 

Main workings--- ---------------------~ 126 

Small tunnels east of Graphic tunneL_ ____ 131 

Mitchell tunneL___________ ____________ _ 131 

Heister prospect ________ ___ __ -:- ____ -. ________ _ 

Future of the district ______________________ . ____ . ___ _ 

Main ore zone south of Nitt stock ____________ '- __ _ 

Area east of main ore zone ______________________ _ 

West ore zone ________________ ___ ..: _____ ________ _ 

Kelly mine_ ________________________________ 132 Ore zones north of Nitt stock ___________________ _ 

Juanita mine ________ __________ . -· _ _ _ _ _ _ _ _ _ _ 137 Granite Mountain area ____ ______ - __ ---_-- -_- ___ -

South Juanita (Juanita Extension) mine .______ 139 Index ______________________ ----~-------------------

ILLUSTRATIONS 

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PLATE 1. Map of region surrounding the Magdalena district, showing general geologic features __ _______ ·_------"- :. _-- __ - 8 

2. Geologic map of the Magdalena district, Socorro County, N. Mex _____________ _________________ -- __ --- _ _ In pocket 

3. A, Kelly, Magdalena Mountain, and Elephant Butte, looking west from dump of Juanita tunnel; B, Northern part 

of Magdalena Range, looking east from Magdalena Mountain _____________________ ~- ________ ---- --_______ 8 

4. Geologic cross sections of the Magdalena district______________________________________ _______________ In pocket 

5. A, Cliff of silicified Kelly limestone resting on argillite, which is cut by a granite dike; B, West slope of Magdalena 

Range, showing its relations to dips of sedimentary rocks ____________ :.. ~- ______________________ ~- -- __ __ _ 16 

6. A, Photomicrograph of pre-Cambrian granite; B: Pre-Cambrian gramte showing somewhat rounded quartz grains 

embayed by interstitial microperthite; C, Quartz vein cutting aplite, and in turn being replaced by an irregular 

veinlet of biotite and calcite (?) __ __ _ :... ______ ____ ________ -,- __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _ 17 

7. A, Lamellar structure in weathered latite tuff on the east slope of Granite Mountain; B, Photomicrograph of preCambrian granite, showing plagioclase and other salic minerals partly replaced by green biotite and hastingsite; 

C, Ramifying veinlets of biotite partly altered to chlorite and calcite replacing feldspar in pre-Cambrian 

granite ________ _________ ____________ -·- ____ ___ _______ ___ ________________ ____ _____ -'-____ ________ _____ 24 

8. Generalized columnar section of sedimentary rocks in Magdalena Range ___ ..,- __ __ -~_ _____________ ________ 24 

9. Columnar sections showing the va.riations in character and thickness of the Kelly limestone, the Sandia formation, 

and part of the Madera limestone _________________________________ ·-- ______ :. _____________________ .____ 24 

10. A, Photomicrograph of purple andesite, showing mesh of hematite, which probably represents resorbed and oxidized 

amphibole needles; B, Photomicrograph of purple andesite, showing hematite pseudomorphs after amphibole; C, 

Red andesite with groundmass thoroughly obscured by red iron oxide ___ ______ __ ____ ______ __ ______ ~- -·- _ · 40· 

_11. A, Upper andesite, showing relatively large phenocrysts of plagioclase and smaller phenocrysts of former hypersthene 

bordered by hematite and internally replaced by what appears to he a clay mineral; B, Red andesite, showing 

groundmass obscured by red iron oxide; C, Plagioclase phenocrysts .and microgeodes of a zeolite with opal or chalcedony core in glassy portion of upper andesite ______________ ··- ______ ..... ___________________________ -- _ 40 
VI ILLUSTRATIONS 

Pa~ 

PLATE 12. A, Vitrophyre in upper andesite, showing celadonite as vermiculate traces and ringlets around zeolite blebs; B, 

Typical rhyolite porphyry, showing partly resorbed ·phenocrysts of quartz and feldspar; C, Photomicrograph of 

typical magnetic rhyolite porphyry; D, Photomicrograph of magnetic porphyry____________ ________________ 40 

13. A, Intrusive augite andesite with phenocrysts of altered plagioclase and augite; B, Typical hornblende andesite; 

C, Photomicrograph of magnetic porphyry from lower part of the formation_______________ __ __ ___ __ __ __ __ _ 40 

14. A, Micrographic intergrowth of augite and magnetite with a border of augite and a core of magnetite; B, Monzonite 

showing graphic intergrowth of orthoclase and quartz in sharp contact with orthoclase; C, Typical monzonite____ 40 

15. A and B, Intergrowths of orthoclase and quartz with numerous hornblende fibers; C, Photomicrograph of mixed 

rock from a contact between pre-Cambrian gabbro and monzonite; D, An enlargement of the fine-grained rna trix in C _________________ ______________ .... _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 40 

16. A, Photomicrograph of norite from the apophysis on Stendel Ridge; B, Photomicrograph of monzonite from west 

side of mass northwest of Stendel Ridge; C, Photomicrograph of facies of typical monzonite from the 'west side 

of the mass northwest of Stendel Ridge; D, Fibrous hornblende impregnating epidote_ ___________ ____ ______ 40 

17. A, Outcrop of pre-Cambrian granite on north end of Magdalena Range east of Anchor Canyon; B, Outcrop of 

Tertiary (?) granophyre northwest of Stendel Ridge_ _______ ____ _________________________________ _______ 40 

18. A, Polished surface of Tertiary (?) granite; B, Photomicrograph of "granophyre" from mass west of Granite 

Mountain; C, Photomicrograph of Tertiary (?) granite________ ______ ______ ___ ____________ _____________ _ 40 

19. A, Photomicrograph of metamorphosed sandstone from a inclusion in granite west of Granite Mountain; B, 

Photomicrograph of Tertiary (?) sandstone west of Granite Mountain partly replaced by a micrographic intergrowth of orthoclase and quartz; C, Photomicrograph of Tertiary (?) sandstone from mass west of Granite 

Mountain partly replaced by orthoclase _______ ____________________________________ · _____ _____ __ ~______ 41 

20. Map showing distribution of faults___ __________________________________________ _______ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 72 

21. Topographic map showing the limits of pediment B and the approximate limits of the older dissected pediments C to H___ ___ _____ ______ ___ ___ ____ _____ _________ ______ _______ ____ _______ __ __ ___ _____ ___ __ __________ 72 

22. A, Foothills of Magdalena Range, looking north from low rhyolite hill three-quarters of a mile west of Kelly; 

B, Upper Patterson Canyon, looking west_ _______________ _______ ______ __________ __________ ___ ____ ___ _ 72 

23. A, Magnetite encasing specularite; B, Specularite-magnetite aggregate, showing partial replacement of specularite by magnetite; C, Magnetite pseudomorphs after specularite; D, Magnetite and partly replaced sheaf of 

specularite _blades in a polished crystal face of pyrite__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 96 

24. A, Banded mixed-sulphide ore from Kelly mine; B, Enlargement of part of A; C, Interfingering pyrite and 

specularite with sphalerite in a carbonate gangue; D, Pyrite crystals and specularite-magnetite blades in quartz 

gangue_ ___ _____ ___ ___ ____ ____ ____________________________________________________________________ 96 

25. A, Pyrite crystal with a zone of small specularite blades; B, Cellular smithsonite ("dry bone ore"); C, Massive 

zinc carbonate that has replaced the "silver pipe" bed of the Kelly ,limestone ___ __________________ _________ 96 

·26. A, Crustiform fibrous smithsonite; B, Concentric amethystine, white, and yellow layers of smithsonite surrounding a cellular mixture composed mainly of brown iron oxide, green malachite, and white smithsonite; C, Photomicrograph of ore from Stonewall mine _____ _____ ____ ___________ ____________ ___ _________ _______ ·____ ___ 96 

27. A, Chalcopyrite interstitial to light-gray blades of specularite and partly replaced by dark-gray covellite; B, Inclusions of chalcopyrite in sphalerite segregated near contacts with specularite (Nitt mine); C, Inclusions of 

chalcopyrite in sphalerite segregated near and parallel to contact with a continuous area of chalcopyrite; D, Inclusions of chalcopyrite in-sphalerite parallel to its contacts with galena and quartz_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 96 

28. A, Parallel banded silicified Kelly limestone; B, Brecciated silicified Kelly limestone recemented by later milky 

quartz_ .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 104 

29. A, Photomicrograph of ore from Graphic-Waldo mine; B, Photomicrograph of metamorphic limestone from a bed 

in the shale member of the Sandia formation east of Granite Mountain_____ _______________________ _______ 105 

30. Map showing disfribution, sizes, and forms of ore bodies mined south of the Nitt monzonite stock ____ ________ _ In pocket 

31. Plan of Graphic-Waldo and Nitt mines, showing geologic features and stopes ____ ______ _____ ___ ____________ In pocket 

32. Cross section of the Ida Hill, Waldo, and Graphic workings, looking N. 77° E---- ------------- -- ---- ----~- 128 

33. Plan, longitudinal profile, and cross sections of main ore shoot north of Waldo tunnel, Graphic-Waldo mine____ 128 

· 34. Geologic sketch of 200- and 275-foot levels of the Nitt mine__ _____ __ _________________ _____________________ 128 

35. Surface plant of Kelly mine in 1916, looking north _____ ____ ·_____ ________ ______ ______ ________________ __ ___ 136 

36. Geologic map and workings of the Kelly and Juanita mines __________ ___ __ _________ _______ ______ ____ _____ _ In pocket 

37. Plan and longitudinal profile of South Juanita (Juanita Extension) mine__ ___________ __ _________________ ____ 144 

38. Geologic map of the Hardscrabble mine ___ ___ ~__ ___________ ___________ __ __ _____ ____ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 160 

FIGURE 1. Columnar sections showing variations in character and thickness of the Kelly limestone __ ___ ~__ ______________ 15 

2. Sequence of effusive igneous rocks and associated rhyolite sills in the Magdalena district___ _____ _____________ 23 

3. Bedding faults in Graphic-Waldo mine___ ______________ _________ __ _______________ _________________ _____ 63 

4. Diagrammatic interpretations of structural development in the vicinity of the Stendel and Vindicator faults____ 65 

5. Diagram showing interpreted relations of east-dipping and vertical faults to relative uplift in the main Magdalena 

Ra:p.ge, and beneath the valley surface between the main range and Magdalena Mountain __ ________________ 67 

6. Diagram of Kelly fault block_ .:. ________________ __ _____ _______ ___ ________ ____ __ :: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 72 

7. Diagram showing the Roll fault and an associated bedding fault along the "silver pipe" bed_ -------------------_ 72 

8. Profiles showing concordant altitudes of spurs and foothills interpreted as dissected pediments _____ -_ - - - _ - _ - _- _- _ 7 4 

9. Generalized section in Graphic-Waldo mine showing relation~ of specularite-magnetite aggregates to sulphide ore 

andgangue ______ ·- ----------------------------------- ------------------- --------- ------------- ---- 90 

10. ''Tallow clay" replaci~g limestone along a fissure beneath a cap of siliCified limestone and passing downward into 

black manganese-sta1ned material. _________________________ ~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 94 
ILLUSTRATIONS 

FIGURE 11. Microdrawing showing four distinct stages of growth of a quartz crystal in a drusy cavity in jasperoid __________ _ 

12. Generalized cross section through Nitt mine _____________________________ ~ _____________________________ _ 

13. Geologic section along Mitchell tunneL _____________________ ______ ___________________________________ _ 

14. Cross section through Traylor shaft of Kelly mine _____________________________________________________ _ 

15. ·cross section along level 10 of Kelly mine ___________________________________________________________ _ 

16. Cross section through middle part of Kelly mine __________________ ----------~--------------------------

17. Cross section of South Juanita (Juanita Extension) mine _________________________________________________ _ 

18. Map of Linch burg tunnel and shallow workings in the Young America, Imperial, and Enterprise claims _________ _ 

19. Section through main raise near breast of Linchburg tunneL ________________________________ ____________ _ _ 

20. Plan and cross section of Cavern and Grand Ledge tunnels _____________________________________________ _ .:. _ 21. Plan of Grand Tower mine _________________ __________ __________________________ _____ ______________ _ 

22. Section from the Germany fault through the Grand Tower shaft, looking N. 7 4 ° E _____________ _______ _______ _ 

23. Map of the Germany mines showing geology of accessible parts _________ ___ __ _____ _____ ________ ____ ___ - ___ _ 

24. Geologic map of Tip Top and Key mines and adjacent Stonewall tunnels _____________________ -_-_-----------

25. Vertical projection of Stonewall tunnels ________________________________________________ _______________ _ 

26. Geologic map of Sleeper tunnel workings ______________________________________________________________ _ 

27. Plan and profile of part of Anchor mine ______________ ___ ______ ________________________________________ _ 

28. Geologic map and cross section of Vindicator mine, looking S. 77° W __________________ _______ ___________ ___ _ 

VII 

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. 154 

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162 

GEOLOGY AND ORE DEPOSITS OF ~HE MAGDALENA MINING DISTRICT, 

NEW MEXICO 

By G. F. LouGHLIN and A. H. KoscHMANN 

/ 

ABSTRACT 

The Magdalena district, in 8ocorro County, central New 

Mexico, is about 65 miles south of Albuquerque and 28 miles 

west of Socorro. It comprises Granite 1\t!ountain and the 

northern part of the Magdalena Range. It has been one oE -

the more productive mining districts i~ the State, but owing 

to declining prices in lead and zinc and the depletion of the 

largest developed ore bodies, its largest mines have been closed 

or worked on a small to moderate scale by lessees since 1930. 

Its early production was chiefly of lead and silver,_ but since 

the discovery of zinc carbonate ore in 1903 and the erection of 

mills to treat sulphide ore a few years later, zinc ore has been 

the most valuable product. 

Geology.-The Magdalena Range and Granite Mountain are 

of the Basin and Range type. They consist of westward-tilted 

and faulted Carboniferous sedimentary rocks that lie on a . 

basement of pre-Cambrian rocks· and are covered with volcanie 

rocks in part if not wholly of Tertiary age. 

The oldest pre-Cambrian formations are argillite and schist. 

They were invaded successively in pre-Cambrian time by 

masses of gabbro and felsite, ·a granite batholith, and many 

diabase dikes. 

From the end of pre-Cambrian igneous activity until Missis--

sippian time the region was subjected to erosion, which exposed 

the granite batholith. On this erosion surface the Kelly limestone, of Mississippian age, was deposited. This formation, 

which is 130 feet thick, is the principal ore-bearing, formation 

of the district. The Sandia formation, of Pennsylvanian age. 

with a total thickness of about 550 feet, overlies the Kelly 

limestone in apparent conformity, although the two formations 

do not represent successive periods of time. The Madera limestone, also of Pennsylvanian age, overlies the Sandia formation 

in apparent conformity. During Permian time the Abo sandstone was deposited on the Madera limestone, without conspicuous angular unconformity, although its basal beds; locally 

contain Madera pebbles, and it is known that some interval 

elapsed between Madera and Abo time. 

No Mesozoic rocks are present. 

Tertiary ( ?) rocks are represented almost entirely by flows, 

tuffs, and breccias of latite, andesite, and rhyolite, stocks of 

granite and monzonite, and dikes of lamprophyre and white 

rhyolite. The volcanic rocks within the district are divisible 

into two groups, separated by an unconformity. The lower 

gt'Oup comprises relatively local basal members of latite and 

andesite, which overlap the sedimentary rocks unconformably 

and are overlain by a persistent flow of banded rhyolite, which 

in the southern part of the district is overlain by more andesite 

and rhyolite. Northwest of the district the banded rhyolite 

overlies a Tertiary ( ? ) saqdstone and may divide the lower 

group into two subgroups. The upper group within the district 

includes andesite and a pink rhyolite whicb are promin~nt in 

the hills west of the main Magdalena Range. South of Kelly 

the lower group is cut by a sill of latite porphyry, whose _rela~ 

tion to the upper group is not known. Both groups are cut 

by sill-like masses and dikes of a rhyolite porpH-yry that is 

considered the youngest member of the upper group, as it is 

separated from the intrusive stocks by a period of pronounced 

faulting. 

The main granite stock is at the north end of the main range. 

As it is almost entirely surrounded by pre-Cambrian rocks 

and Quaternary alluvium, its relations to the monzonite stocks 

and to structural features are not clear. The sedimentary rocks 

are flexed along its concealed western margin, but as they 

were somewhat flexed and eroded before the first volcanic 

period there is no evidence that the intrusion of the granite 

was accompanied by thrusting. It is more likely that intrusion 

took place along a zone of weakness related to earlier flexing. 

The main stock o{ monzonite, the Nitt stock, is of irregular 

form, and its general position indicates that it was intruded 

along a zone weakened by intersecting :r.najor faults. Minor 

stocks, in and beyond· the northwestern part of the district,· 

are arranged in a zone ·of north-northwesterly trend in line 

with the principal zone of faults along which ore-forming solutions rose. The later facies of monzonite are feldspathic 

and gran~tic, and one or the ~maHer monzonite stocks is cut 

by a granite dike. This evidence suggests that the granite 

as a whole is later than the monzonite, but there is no direct 

evidence to determine the relative ages of the main s_tocks of 

granite and monzonite. 

The lamprophyre and white rhyolite dikes, like the monzonite 

stocks, also lie for the most part along the structural zone 

of north-northwesterly trend. 

Rock alteration .. -Rock alteration is extensive and of different grades. Pure limestone, particularly the Kelly, adjacent 

to the stocks has been replaced by such silicate minerals as 

wollastonite, diopside, and garnet (grossularite), which may 

ha:ve been formed during the late, feldspathic stage of monzonite intrusion; somewhat farther away, along ore zones, 

the limestone has been replaced by hedenbergite, garnet (andradite), and platy calcite; and still farther away by immense 

masses of jasperoid, which are regarded as equivalent to the 

silicates in time but which formed below silicate-forming temperatures. Limestone containing hedenbergite and andradite 

was later replaced by specularite and magnetite, and still later 

_ by sulphide ore, which extends far from any intrusive stocks 

or centers of mineralization. 

Siliceous rocks, both sedimentary and igneous, contain a 

little tourmaline and andalusite close to. the ~tocks and much 

epidote farther away. Impure limestone is also epidotized. 

The siliceous rocks are cut by a few large quartz veins, which are · 

thought to be equivalent to the jasperoid masses in limestone. Epidotized volcanic rocks are conspicuous in the northern and central parts of the district. The epidote varies :ln 

quantity and is accompanied by varying amounts of chlorite, sericite, and calcite. Sericitized rock is most conspicuous wher~ the 

1 
2 MAGDALENA MINING DIStrRICT, NEW MEXICO 

rocks are veined or impregnated with sulphides. In the southern part of the district the volcanic rocks are impregnated 

with much red hematite, and some of them contain conspicuous 

amounts of chalcedonic geodes and quartz veinlets. A few 

contain small amounts of clay minerals and celadonite, which 

are believed to have been formed by rising hot water. 

Structure.-Tbe principal structural features-homoclinal 

faulted masses-were formed in Laramide time. Deformation 

began with flexing, expressed by a change of strike from N. 

15° W. in the Magdalena Range to N. 30° E. in the Granite 

Mountain area. Flexing was accompanied by minor reverse 

faulting and followed by the initiation of normal longitudinal 

and transverse faulting through gravitative adjustment. The 

major longitudinal faults dip eastward. Movement along them 

produced essentially vertical faults on their hanging-wall sides 

and permit ed the settling of intervening wedge-shaped blocks. 

The transverse faults mark the north and south boundaries of 

subsided blocks. Renewed movement accompanied by pronounced tilting took place along the east-dipping faults after 

the first period of volcanic eruption. The second period of 

eruption was followed by vertical faulting ulong well-defined 

zones, especially on the west slope of the main range, and 

caused renewed movement along vertical faults and associated 

east-dipping and transverse faults. The valley west of the 

main range was depressed at this time. This stage of vertical 

faulting was followed by the intrusion of stocks. The monzonite stocks especially were guided by fault intersections along 

the main zone. Subsequent recurrent movements within the 

district were small. They afforded openmgs for the intrusion 

of lamprophyre and white rhyolite and the deposition of ore. 

Movement within the district since ore deposition was trivial, 

but it was more conspicuous along the northeast base of the 

range. 

Physiographic development.-Physiographic development of 

the Magdalena Range took place in as many as eight stages 

of erosion, each defined clearly or obscurely by remnants of 

rock pediments. Three stages, better defined than the others, 

are represented by the alluvium-covered pediment at the base 

of the range, alluvium-covered and other benches about 200 

feet higher, and relatively long spurs and summits about 

200 feel still higher, including those on Stendel Ridge. The 

second of these three stages was the one in which practically 

all of the oxidation of ore took place. Restoration of the 

surface that represents the oldest of these three stages shows 

that the main Magdalena Range was then continuous with 

Granite Mountain, whose summit had just begun to appear 

above the pediment. Drainage from the west slope of the 

range may once have been into a closed basin, but rapid 

erosion of the soft volcanic rocks that filled the valley between 

the main range and Granite Mountain permitted the heads of 

tributaries of the Rio Grande system to cut westward and 

divert drainage from the west slope into its present form. 

The different stages of erosion may be correlated with the 

varying rates at which the principal tributaries to the Rio 

Grande cut their channels through volcanic flows and tuffs 

of different hardness; t.ut the youngest pediment and its 

pr~sent dissection may be related to a recent fault along 

the northeast base of the range. 

Economic geology.-Ore was discovered in the Magdalena 

district in 1866, but so far as known very little ore or bullion was shipped before 1881. From that year to 1939, inclusive, the total value of shipments from Socorro County, which 

were mainly from the Magdalena district, was $29·,410,112. 

Until 1900 the output of the district consisted of lead, with 

subordinate silver and a little gold. Then copper became the 

principal metal until 1903, when the zinc-carbonate ores were 

first recognized. Zinc then became the dominant metal, coming mainly from carbonate ore until 1908 and thereafter 

mainly from complex ~1,1lphide ore. The metal output of 

Socorro County from 1881 to 1939 comprised $1,690,096· in 

gold, 4,039,459 ounces of silver valued at $3,532,705, 11,632,843 

pounds of copper valued at $2,292,217, 88,548,427 pounds of 

lead valued at $4,513,649, and 233,701,399 pounds of zinc 

valued at $17,381,445. Practically all of the lead and zinc 

and most of the copper have ·come from the Magdalena district, but most of the silver before 1903 and of the gold 

before 1911 came from elsewhere. The district was especially 

active during the first World War, reaching its peak of production in 1916. Operations almost ceased during the depression of 1921, and since then the district has been a minor 

producer, at times practically dormant. The largest· developed 

deposits appear to be practically exhausted, but some unexplored ground awaits attention whenever economic conditions 

justify it. 

The mines and prospects lie mainly in three general zones 

that trend southward from the principal monzonite stock, but 

the output has come almost entirely from replacement deposits in the Kelly limestone in: the central or main zone. A 

small quantity has come from replacement deposits in other 

limestones and very little from veins in siliceous rocks. 

The primary minerals were deposited at temperatures that 

ranged from high to ratller low. The high-temperature minerals are represented by "contact-metamorphic" silicates that 

are present in areas adjacent to intrusive stocks and by 

specularite-magnetite aggregates that are closely associated 

with minerals form~d later at moderate temperatures. The 

moderate-temperature minerals are represented by the sulphide ores, which are divisible into two groups of deposits 

that represent the hotter and cooler parts of the mesothermal 

range. The first group is characterized by massive sulphides 

with siliceous gangue. It includes the largest ore bodies and 

lies mostly along the northern part of the Kelly-Graphic fault 

zone, which is also the main ore zone; but other members of 

the same group are present in the southern part of the same 

zone, along the Waldo ftlult of the western zone, and in the 

limestone inclusion in . the Tertiary ( ?) granite at the Hardscrabble mine. . The second group, Characterized by barite 

and fluorite accompanying massive to disseminated sulphides, 

includes all the other deposits of the main zone and the ores 

or all the other zones, both in limestones and siliceous rocks. 

It is largely associated with enormous masses of barren jasperoid, which replaced limestone during a presulphide stage 

of deposition and may be an outlying equivalent of the hightemperature or contact-metamorphic silicates. 

The three ore zones south of the main monzonite stoc~, 

correspond to major zones or groups of faults. Deposits in 

other parts of the district are too small and scattered to be 

correlated with well-defined zones. The largest deposits have 

replaced limestone, mainly along networks of minor faults, 

fissures, and bedding planes that have been subjected to tensional movements in the main ore zone. The smaller deposits 

have similar structural relations, although those in siliceous 

rocks have replaced only the immediate walls of fissures and 

therefore maintain a veinlike rather than blanketlike form. 

The original ores are classified according to · mineral composition as pyritic (of no present value)·, pyritic copper, zinc, 

lead, and mixed sulphide or zinc-lead. The. pyritic copper ores 

are practically confined to the basal members of the Kelly 

limestone in the Nitt, Graphic-Waldo (Ozark), and Kelly 

mines. The reason for this restricted distribution is not clear. · 

The zinc, lead, and mixed-sulphide ores are present throughout the Kelly limestone but mainly above the basal members. 

The mixed ores predominate, and the zinc ores, which differ 

from them mainly in the ratio of zinc blende to galena, form 

local lenticular shoots, some close to the main monzonite stock 

and otbers far from it. The lead ores in part form similar but 
INTRODUCTION 3 

much smaller shoots and in part larger masses of originally 

mixed sulphide ore from which the zinc blende and part or 

all of the pyrite and chalcopyrite have been leached. Chalcopyrite also forms small streaks of high-grade ore that has 

little value except as the original sources' of certain oxidized 

copper ores. The silver and gold contents of unenriched sulphide ores are very small, and enriched sulphides ih shoots 

approaching commercial size are exceptional. 

The ores are believed to have been derived from the same 

deep sources as the intrusive stocks and the later lamprophyre 

dikes. Three local centers of mineralization along the main ore 

zone are recognized-the Graphic fault block, the northeastern 

part of the Kelly block, and the Young America and adjoining faults in the southern part of the district. The first two 

account for the bulk of the district's output. Other centers 

in the main Magdalena Range are indicated along the Waldo 

fault west of the Graphic block, the Vindicator fault, which is 

a continuation of the main ore zone north of the main monzonite stock, and the Hardscrabble mine. Another center, east 

of Granite Mountain, is obscurely indicated by the presence of 

high-temperature minerals. 

Processes of oxidation haye produced iron and ironmanganese oxides in small to rather large masses but of no 

commercial value; oxidized copper ores, some of unusually high 

grade, and associated enriched sulphide ore; lead carbonate 

and zinc carbonate, which constituted the main output of the 

district until 1906; and gold and silver ores in a few highgrade bunches. As the processes of oxidation and sulphide 

enrichment were generally similar to those of the Leadville 

district, Colo., which have been fully described/ only a summary . 

account of them is presented in this report. 

Oxidation and enrichment took place, for the most p:trt, during the development of an old pediment surface, called pediment D in the section on physiographic development. They 

were limited by local ground-water tables, which in turn were 

controlled ·by major faults that served as barriers to 

underground cifculation. 

Mines accessible to the authors are described in as much 

detail as_ available data permit. Although the principal mines 

of the district have been practically exhausted under present 

economic conditions, it is understood that an appreciable reserve of mill ore is still available whenever the outlook for the 

zinc market is sufficiently favorable. There is also a considerable undeveloped area in the southern part o-f the distr~ct, where the Kelly limestone along the west side of the main 

fault zone deserves exploration. The future of the district is 

largely dependent on the results of such exploration. 

The ground beneath Hardscrabble Valley, north of the main 

monzonite stock, is also entitled to furtber consideration, as 

the ground-water level there is remarkably deep and the Kelly 

limestone, if adequately replaced by ore, can be mined without _ 

excessive pumping. West of the Waldo fault the Kelly limestone is so deeply buried and the probable quantity of water 

to be handled so great that there is little to encourage deep 

development. In the Granite Mountain area also, the shallow 

ground-water level and the small size of tile scattered prospects 

offer little promise of important discoveries. 

INTRO_DUCTION 

FIELD WORK AND ACKNOWLEDGMENTS 

Subsequent to the publication in 1910 of Professional 

Paper 68, The ore deposits of New Mexico, the United 

States Geological Survey had planned a detailed study 

1 Emmou~. K I!"'., In-ing-, J·. D., aud Loughlin, G. F., Geology and ore 

deposits of the LeadYille· district, Colo:: U. S. Geol. Survey Prof. Paper 

)48, pp. 248-272, 1927. 

of the Magdalena district, and G. F. Loughlin was 

assigned to the work. In the fa'll of 1915 he made a 

preliminary visit to the district, mainly to study mine 

'~;Torkings that were soon likely to become inaccessible. 

A year later he began a detailed study" of the district, 

but the war activities of the Geological Survey and 

the consequent shifting of its personnel during -and 

after 1917 made it necessary to tran:sfe~r.-Loughlin t~ . 

to administrative work, where the demands upon his 

6me prevented his completing the report on the 

district. · 

In 1928 the newly organized New Mexico Bureau of 

1\fines and Mineral Resources undertook to finish the 

work. Activity in the district had greatly declined, 

but the complexity of the geology and its bearing on \ 

possible ore reserves justified the completion of the 

work for both scientific and commercial purposes. 

During July and August of that year Mess'rs. A. H. 

Koschmann and V. T. Stringfield, then connected with 

that org~nization, restudied the area mapped by Mr. 

Loughlin, whose maps and other data were placed at 

their disposal. During June and July 1929 Mr. 

Koschmann, assisted by Merz Black and Gordon Wells, 

mapped the geology of the area north of parallel 34° 

07' and the strip west of meridian 107° 13', and Black 

nlapped the topography of this area. Mr. Loughlin 

spent about 3 weeks in the field during 1928 and 1929 

with the members of the State Bureau reviewing the 

essential features of the geology. 

During the field season of 1916 W. 0. Hotchkiss 

8pent 3 weeks in the district tracing formation contacts underneath the alluvium, especially that of the 

monzonite, by means of the dip needle. In the summer of 1928 Messrs. Don E. Wilson and F. G. Boucher, 

of the State Bureau, checked a few topographic details, 

and Messrs. Koschmann and Stringfield revisited the 

field several times after the regular field seasons of 

1928 and 1929 to check questionable points in geology 

as the report progressed. S. G. Lasky, then of the 

State Bureau, studied the Nitt mine in 1929 and spent. 

the winter of 1929-30 in Washington assisting Mr. 

Loughlin in the study of ores and the preparation of 

mine maps and descriptions. Several chemical analyses were made by the State Bureau and are duly 

accredited in the text. 

Help of various kinds has been received from several 

persons both in the field and in the office, and the authors are indeed grateful for this assistance. They are 

especially indebted to the late C. T. Brown and Philip 

B. Argall, and to J. A. Macdonald, John A. Weir, Paul 

B. Moore, Ian D. Mactavish, V. Carl Grubnau, F. H. 

Gordon, Sim Exter, B. A. Statz, G. L. Brooks, and Roy 

8tendel, who generously gave of their time and supplied many of the mine maps; also to C. M. Glasgow, 

superintendent in 1915-16 of the Kelly mine and Mr. 

Pressler, superintenden in 1915 and Philip H. Argall, 
4 MAGDALENA MININ·G DISfl'RICT, NEW MEXICO 

superintendent in 1916 and later, of the Graphic-Waldo 

(Ozark) mine; also to C. S. Ross, W. T. Schaller, C. F. 

Park, Jr., and M. N. Short, of the United States Geological Survey, who kindly determined several minerals, 

djscussed some of the problems involved, and critically 

read parts of the manuscript, and to T. B. Nolan, who 

critically read the entire manuscript. 

BIBLIOGRAPHY 

Very little detailed geologic work has ·previously 

been done in the district, and the literature pertaining 

t.o the area consists chiefly of brief articles on smne 

mine or some special problem of geology of the region. 

In the list of publications below only those articles are 

given that contain information on the district; articles 

dealing with adjoining areas or related problems are 

duly recognized in the footnotes at appropriate places 

within tlie text. This bibliography is in part taken 

from that of Gordon,2 and brought up to date. 

1882. SilLIMAN, BENJAMIN, JR., Mineral regions of southern 

New Mexico: Am. Inst. Min. Met. Eng. Trans., vol. 10, 

pp. 424-444; Eng. and Min. Jour., vol. 34, pp. 199-200, 

212-219. Describes the geology of the region west of 

the Rio Grande from Socorro southward and comments on the ore and minerals found. 

1897. HERRICK, C. L., The geology of a typical mining camp in 

New Mexico : Am. Geologist, vol. 19, pp. 256-262. Describes the general geologic features of the M_agdalena 

Range and the fault phenomena of the region. 

1898. HERRICK, C. L., Papers on the geology of New Mexico: 

Denison Univ. Sci. · Lab. Bull., vol. 11, pp. 87-92; re · 

print, New Mexico Univ. Bull., vol. 1, 1899, pp. 87-92 

Describes the geology of Magdalena Mountain and includes an account of the basic eruptions of the Magdalena district. 

1901. HERRICK, C. L., Applications of geology to economic pr·oblems in New Mexico: Internat. Min. Cong. Proc., 4th 

sess., pp. ~1-64. De~ci'ibes some of the geologic features and the occurrence of economic minerals. 

1903. JoHNSON, D. W., Block mountains in New Mexico. Am. 

Geologist, vol. 31, pp. 135- 139. Discusses the phenomena of block faulting and · dt>scribes the occurrence of 

examples of this type of structure in the central New 

Mexico region. 

1904. HERRICK, C. L., Laws of formation of Ne·w Mexico mountain ranges: Am. Geologist, vol. 33, pp. 301--312, 393. 

Describes the geologic structure and physiographic features of several mountain ranges of New Mexico. 

KEYES, C. R., Note on block mountains in New Mexico : 

Am. Geologist, vol. 33, pp. 19-23. Believes the block 

mountains of central New Mexico to be the result 

chiefly of one great fault along a single plane. 

KEYES, C. R., Remarkable occurrence of aurichalcite: 

Iowa Acad. Sci. Proc., vol. 11, p. 253. Describes an 

occurrence of aurichalcite in the Magdalena district. 

JoNES, F. A., New Mexico mines and minerals: (World's 

Fair Ed.) Santa Fe, N. Mex., 349 pp. Includes a brief 

account of the general geology and observations on the 

occurrence, geologic relations, and character of ore 

deposits, and mining - and production of minerals. 

Gives a list of minera)s occurring in New Mexico. 

2 Lindgren, Waldem~r, Graton, L. C., and Gordon, C. H., The . ore deposits of New Mexico: U. S. Geol. Survey Prof. Paper 68, pp. 214-217, 

1910. 

1905. KEYEs, C. R., Zinc-carbonate ores of the Magdalena Moulltains: Mining Mag., vol. 12, pp. 109-114. Describes 

the geology of the range and the occurrence and relations of the zinc ore deposits. 

KEYES, C. R., Northward extension of the Lake Valley 

limestone: Iowa Acad. Sci. Proc., vol. 12, pp. 169-171. 

Mentions the occurrence of Lake Valley limestone in 

several ranges north of the Lake Valley area and 

gives a section of the Carboniferous formations in 

the Magdalena Range. 

1906. BRINSMADE, R. B., ' Kelly, New Mexico.-,.-A zinc camp 

whose ores have been made available by modern 

metallurgical methods: Mines and Minerals, vol. 27, 

pp. 49-53. Gives an interesting historical sketch and 

brief descriptions of the geology, mine workings, and 

mining and milling operations; discusses the nature, 

occurrence, and origin of the ores. Regards the intrusive rhyolite porphyry as the source rock. 

HADDON, R. W. Zinc mining in New Mexico : Eng. and Min. 

Jour., vol. 81, pp. 845-846. Briefly summarizes geology 

and descriptions of mineral deposits. 

LINDGREN, WALDEMAR, and GRATON, L. C., A reconnaissance 

of the mineral deposits of New Mexico: U. S. Geol. 

Survey Bull. 285, pp. 74-86. Briefly describes the general geology and structure of the State and then outlines the ore deposits, giving their geographic and 

geologic distribution. The most productive deposits are 

post-Cretaceous, and are correlated with an earlier series of intrusions of possibly early Tertiary and a later 

epoch of effus:on of middle or late Tertiary age. 

1907. GoRDON, C. H., Notes on the Pennsylvania formations in 

the Rio Grande Valley, New Mexico: Jour. Geology 

vol. 15, pp. 805-816. Discusses the character and classification of the Pennsylvanian formations in the Rio 

Grande Valley, with special reference to the lower 

division, for which the name Magdalena group is 

proposed. 

GoRDON, C. H., Mississippian (:Lower Carboniferous) formations in the Rio Grande Valley, New Mexico: Am. 

Jour. Sci., 4th ser., vol. 24, pp. 58-64. Describes the 

occurrence of Mississippian rocks at Lake Valley, Hillsboro, Kingston, and Cooks Peak, and gives lists of the 

fossils found in them. The name Graphic-Kelly applied 

by Herrick to these rocks in the Magdalena district is 

changed to Kelly limestone. 

JoHNSTON, W. M., The Kelly mine, New Mexico, and 

treatment of its ores: Min. World, voi. 27, pp. 267- 269. 

A brief description, with emphasis on the character 

of ore, which was mostly carbonate but passed into 

the sulphide zone. 

I 1908. ARGALL, P. B., The ore deposits of Magdalena, New Mexico: Eng. and Min. Jour., vol. 86, pp. 366-370. Discusses chiefly the relationship of the ore to the geology, 

its character and origin. 

1910. LINDGREN, WALDEMAR, GRATON, L. C., and GORDON, 0. H ., 

The ore deposits of New Mexico: U. S. Geol. Survey. 

Prof. Paper 68, 361 pp. A summary account of the ore 

deposits of the State, giving the general geologic features and generalizations concerning the ore deposits, 

followed by a more or less detailed description of the 

mining districts. 

1911. KEYES, C. R., Sulphide ore bodies in oxidized zones: Eng. 

and Min. Jour., vol. 92, pp. 793-794. Discusses origin 

of sulphide bodies and argues that they are not remnants of primary deposits but that they are "largely 

of vadose origin-contemporaneous with the oxidic 

ores."'- The ores at Magdalena are given as an example. 
GEOGRAPHY 5 

1912. Tu'ITLE, E. G., The Magdalena mmmg district, New · 

Mexico : Mines and Minerals, vol. 33, pp. 275-:-277. A 

brief historical review of the district, followed by · a 

brief description of the geology and the six most im-

_portant ore horizons. 

STATz, B. A., Geology of the Magdalena district, New 

Mexico : 1\;[in. Sci., vol. 66, pp. 406-407 . . A very brief 

summary of the geology a·nd origin of the ores. 

1915. JoNES, F. A., The mineral resources of New Mexico: New 

Mexico School of Mines, Min. Res. Survey, Bull. 1, 77 

pp. Very briefly describes the distribution of commercial minerals in the State with their geologic 

occurrence, character, and · production; a catalog of 

all minerals found in the State and their location is 

appended at end. 

1916. RICKARD, T. A., Philip Argall and metallurgical progr~s 

(an interview) : Min. and Sci. Press, vol. 112, pp. 119~ 

131. Metallurgical problems of Magdalena ore are 

mentioned on pp. 12..9-130. 

1917. DARTON, N. H., A comparison of Paleozoic sections in 

southern New Mexico: U. S. Geol. Survey Prof. Paper 

108-0, pp. 31-55. Gives the distribution and a comparison of the Paleozoic formations in the southern 

part of the State. 

1922. FINLAY, J. R., Report of appraisal of mining properties 

of New Mexico: New Mexico State Tax Commission, 

1921-22, pp. 52-54. Gives brief general comment and information regarding the Empire Zinc Co. (Kelly mine), 

Ozark Smelting & Mining Co. (Graphic mine), Mines 

& Metals Co. (Ambrosia and Juanita mines.), and TriBullion Smelting & Development Co. (Nitt mine). 

1923. HoTCHKISS, W. 0., Magnetic methods for explorati()n and 

geologic work : Am. lnst. Min. Met. Eng. Trans., vol. 

69, pp. 36-47. Discusses general pripciples of magnetic 

methods and then gives instances of practical application in the. field, including results obtained in the Magdalena district. 

KEYEs, C. R., Brass ore in nature: Pan-Ain. Geologist, vol. 

39, pp. 75-76. A popular brief description of aurichalcite in the Graphic mine. 

1928. DARTON, N. H., "Red beds'' and associated formations in 

New Mexico: U. S. Geol. Survey Bpll. 794, 356 pp. 

Discusses first the general stratigraphy of the State 

and then the local geology of many areas. 

1933. ScHMIT.T, HARRISON, Structural associations of certain 

metalliferous deposits in southwestern United States 

and northern Mexico: ·Am. lust. Min. Met. Eng. Contr. 

38 (Class I, Mining Geology), ·February 19B3. . Contains 

a short paragraph attributing localization of ore to 

replacement along auxiliary faults cutting Kelly limestone 'on the hanging-wall side of a master fault of 

east-northeast trend and south-southeast dip. 

GEOGRAPHY 

LOCATION OF THE AREA 

The Magdalena district lies in Socorro County in 

the central part of New Mexico about 65 miles south 

of Albuquerque and 28 miles west of Socorro (see pl. 

1). It ·possesses features typical of the Basin and 

Range province and lies in the southeast extension of 

that province.3 The area incluQ_ed within the district 

that has been mapped in detaii (pl. 2) contains the 

north end of the main Magdalena ~ange and, to the 

3 Fenneman, N. M., Physical divisions of the United States, map published by U.S. Geol. Survey, ed. 1930. 

northward, Granite Mountain and its eastern foothills. 

A western member of the range, separated from . the 

main part by a broad valley of northerly trend, lies 

about 2 miles west of the area anP, includes Magdalena 

Mountain (pl. 3, A). This is also called Picture 

Mountain, becau.se the distribution of talus and brush 

on its northeast slope resembles the profile of a human 

head. The area studied is about 7.2 miles long and 

ranges in width from 2.7 miles in the north-central 

part to 2.17 miles in the northern and southern parts, 

thus covering about 17 square miles. 

The main productive area is on the west slope of 

the main range, but considerable prospecting has also 

been done in the outlying northern and northwestern 

parts of the district in the Grani.te Mountain area. 

The principal mines are in an area of about 8 square 

miles in which the town of Kelly, near the base of the ·. 

range, is centrally located. South of the main producing area the Magdalena district adjoins the Water 

Canyon and Hop Canyon districts, from which small 

intermittent shipments have been n1ade. 

Magdalena, the principal settlement, lies about 3 

miles northwest of Kelly and about 2 miles west of 

the area mapped, on the east-west State' highway that 

leads ~estward from Socorro across the San Agustin 

Plains and Datil Mountains. The terminus of a 

branch of the Atch{son, Topeka & Santa Fe Railroad 

that leaves the main Albuquerque-El Paso line at 

· Socorro, Magdalena constitutes the main shipping 

point for ore as well as for .cattle and sheep from a~ 

extensive grazing country. A spur track from this 

branch extends to a loading point for ore nearly ll/2 

miles due west of Kelly. 

RELIEF 

The major features of relief are the Magdalena 

Range (pl. 3, B) and Granite Mountain, which are 

bounded by bedrock floors (pediments) and alluvial 

plains on the east and west. 

The Magdalena R~tnge, like typical ranges of the 

Great Basin, has a northward trend an<!_ consists of 

tilt~d and faulted sedimentary and volcanic ·rocks on 

a pre-Cambrian basement. · The stratified rocks as a 

whole form the western slope of the range, and their 

westerly dip largely determines the western slope of 

the range, as shown in plates 4 and 5, B. The eastern 

side of th~ range consists mainly of pre-Cambrian 

granite. Its slopes are decidedly more steep and 

rugged and are cut by gulches that head abruptly 

along the crest of . the range. The mapped area 

ranges in altitude from 6,025 feet at its northeast 

corner, along La Jenze Creek, to 9,650 feet at the 

southeast corner on the crest of the range, but summits of volcanic rock beyond .the south limit of the 

area are considerably higher. The crest of the range, 

characterized largely by cliffs of silicified limestone, is 
6 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

gently undulating. The upper western slope is also 

comparatively gentle in the southern part of the area 

mapped, owing to the low angle of dip of the strata, 

and is good · grazing land; but the lower slopes are 

deeply cut by dry gulches. 

Directly north of the Magdalena Range, but separated from it by a hroad gap, is Granite Mountain, 

which reaches an altitude of 7,200 feet. Its crest is 

composed of rhyolite porphyry and latite and at the 

highest point intrusive andesite. The Paleozoic sedimentary rocks with some volcanic rocks form the low 

foothills to the east, and intrusive and extrusive rocks 

with some Tertiary ( ~) sandstone form the low hills on 

the west. 

VALLEYS AND DRAINAGE 

The la~gest valley within the area studied is the 

transverse valley of northeasterly trend that separates 

the main range from Granite Mountain and connects 

the broad low lands to the west and east of the district, as shown on plate 1. South branches of this . 

transverse valley include the valley between the main 

range and Stendel Ridge, ·which will hereafter be referred to as Hardscrabble Valley after the abandoned 

Hardscrabble Camp which is located in it (:pl. 2), 

and the longitudinal valley that separates the main 

range from Magdalena Mountain and is mostly just 

west of the area mapped. Both of these valleys are 

in downfaulted areas. 

There are no· permanent streams in the area mapped. 

Runoff from rains and cloudbursts in excess of that 

which is absorbed by the alluvium is disposed of by 

La J enze Creek (pis. 1 and 2) . This creek heads in 

the southern part of the Gallina Mountains, in general 

flows eastward, passing north of Granite Mountain, . 

and enters the Rio Salado, which is in turn tributary 

to the Rio Grande. Its chief tributary wit4in the 

district is the arroyo that extends along the south and 

east sides of the Granite Mountain area and has one 

branch heading at the south end of Harscrabble 

Valley. 

Although there are no permanent streams in the 

area, the abundant shaly beds and volcanic rocks · 

maintain a shallow circulation of ground water that 

emerges in intermittent springs either at the outcrop 

of some impervious bed or where a fault along the 

western foothills affords escape to water that has 

traveled downward along westward}-dipping beds. 

North Camp was favored by a permanent spring that 

rose along a large though obscure fault until the tapping of the fault on level 10 of the Kelly mine diverted the flow. Springs at the head of Patterson 

Canyon are sufficient to maintain a small stream for 

a considerable part of the year, and in Hop Canyon? 

south of the area mapped, water is · sufficient to supply Magdalena, except in prolonged dry seasons, as 

in the·early summer of 1928, when the town had to depend upon water pumped from the lower levels of the 

Graphic-Waldo (Ozark) mine. Kelly obtains · its 

water from the extensive workings of the Germany 

mme. 

CLIMATE 

The climate of the district is rather mild and is 

very pleasant during the summer. The following table 

summarizes the climatic conditions at Magdalena. 

Temperature and precipitation at Magdalena, N. Mex. 1 

[Altitude at Magdalena, 6,556 feet] 

Length 

ofrecord January (years) 

Febru- March 

ary April May June July Year 

--- ----------------------------------- ----------------

Temperature (° F.): 

Average _ 51.2 ------------------------ 20 33. 5 37.2 43.0 49.2 53.0 67. 8 70.4 67.9 62.1 52.3 41.1 32.4 Average maximum ___ __ ___ ______ 20 46.8 51.0 57. 6 64.8 74.2 84.2 83.9 81.5 76.3 66.9 55.5 44.7 65.6 Average minimum _______ _______ _ 20 20.2 23.3 28.4 33.7 41.8 51.5 56.9 54.3 47. 9 37. 7 26.7 20. 2 36.9 Highest _____ _________ ________ --_- 20 70 78 84 89 91 102 102 95 93 86 78 68 102 Lowest_ _____ _____ ________ _______ 20 -5 -3 0 1 19 22 45 34 20 11 -4 -21 -21 

Precipitation (inches): 2 Average snowfall ___ ______ ____ ____ 22 3.1 4.8 2. 7 1.1 . 1 6. 2 21.1 . 0 .0 .0 . 0 .6 2.5 

Average rainfalL-----:--------- ___ 28 .60 .44 .61 1.02 .53 .73 2. 90 2. 58 1.28 .88 .62 .65 12.84 

t U. 8. Dept. Agr., Weather Bur., Climatic summary of the United States [from the establishment of station to 1930, inclusive], sec. 27, Northwestern New Mexico, pp. 12 17, 18-19, 1933. . 2 Maximum annual precipitation, 23.84 inches in 1914; minimum annual precipitation, 4.25 inches in 1922; maximum monthly precipitation, 11.70 inches in July 1914. 

Extreme temperatures . are unusual, and the daily 

and seasonal variations are moderate. The relative 

humidity is low and, with the aid of an occasional 

gentle breeze, mitigates the heat of the few hot days. 

The evenings are usually cool and pleasant. As in 

other parts of the Rocky Mountain belt, relatively 

strong winds prevail :for about 6 to 8 weeks in spring. 

The ·precipitation is not abundant, but this region 

has a well-defined rainy season, which usually comes 

in July and August. During this season daily showers 

at noon and early in the afternoon are common. On 

the west slope of the range precipitation is probably 

greater than that shown in the table. The temperature in winter is sufficiently low for snow to cover the 

range, and the upper northern and protected slopes 

may be white from early fall to late spring. 
PRE-CAMBRIAN ROCKS 7 

VEGETATION 

The upper slopes support small clusters of yellow 

pine, which attain heights of 30 feet or more, but the 

most abundant trees are the pi:fion or nut pine, the 

Rocky Mountain juniper or "cedar," the alligator 

juniper, and mountain mahogany. The alligator juniper attain_s a maximum diameter of 3 feet and · a height 

or more than 15 feet, and the mountain mahogany in 

favored places also attains a height of 15 feet. Tall 

aspens and other trees are thickly clustered in Patterson Canyon near the spring. The upper, northern and . 

more moist slop((S are thickly covered with oak brush 

and "thorn bushes'' or with short grass, which affords 

grazing, especially on shaly ground. On the lower, 

more arid slopes sagebrush and cactus, including the 

cane cactus, and species of flat-leaved and melon-shaped 

prickly pear are prominent, together with Spanish 

bayonet and soapweed. 

GEOLOGY 

The geologic formations of the district cmnprise 

four main groups-sedimentary and igneous rocks of 

· pre-Cambrian age; limestones, shales, and quartzites 

of Carboniferous age; extrusive and intrusive igneous 

rocks probably of early and middle Tertiary age; and 

landslides and alluvial deposits of Pleistocene to ~ecent 

age. A little Tertiary ( ~) sandstone is present southwest of Granite Mountain. The bedrock formations 

have been tilted and thoroughly broken into fault 

blocks, and their surface distribution is accordingly 

complex in detail. But with few exceptions the preCambrian rocks form the . east slope of the main Magdalena Range and a few small areas on the west slope, 

the Carboniferous sedimentary rocks cover most of the 

main west slope, and the Tertiary ( ~) igneous rocks 

form the foothills as well as the lower western slope 

in the south part of the district. Farther south the 

Tertiary ( ~) rocks extend eastward across the summit 

of the range. In the Granite Mountain area· in the 

northern part of the district pre-Cambrian rocks are 

limited to a few small outcrops at the eastern end of 

the exposed bedrock, the Carboniferous rocks are confined to the low hills farther west, and the Tertiary ( ~) 

rocks. form the higher hills in the central and western 

part, including Granite Mountain itself. 

PRE-CAMBRIAN ROCKS 

Pre-Cambrian rocks form the basement of the district. As the oldest rocks that overlie them in the 

district are of Mississippian age, their pre-Cambrian 

age cannot be proved, but it is inferred because of 

their general structural similarity to pre-Cambrian 

rocks elsewhere in the State. They include in the 

order of relative age, argillit~ and schist, early gabbro 

or diabase, felsite or aporhyolite, granite, and late 

diabase. Of these the granite is exposed over the 

greatest area. An outstanding feature of th~se rocks 

is their regional impregnation by green biotite associated with smaller amounts of chlorite, hastingsite, 

epidote, zircon, allanite, apatite, and magnetite and 

rarely with fluorite. Solutions depositing these minerals mark the final episode of pre-Cambrian activity 

in the district and will be discussed at the end of this 

section. 

ARGILLITE ("GREENSTONE") AND SCHIST 

DISTRIBUTION AND STRUCTURE 

The rocks included under the heading "argillite and 

schist" on plate 2 comprise argillite and hornblende 

and mica schists. These rocks and the early gabbro, 

which is intrusive into them, have been locally called 

"greenstone" and have been described by Gordon as 

"greenstone schi~ts." 4 The argillite forms several 

small to fair-sized areas c)J.iefly on the west slope in 

the· main range from the vicinity of the Hardscrabble 

mine to the southeast corner of the district. All these 

areas represent upthrown fault blocks, although this 

. relation is not so evident in the northernmost area as 

in the others. Gordon states 5 that "greenstone" is also 

exposed north of Water Canyon on the east slope of 

the range, beyond the south limit of the area 1napped. 

The mica and hornblende schists crop out on the 

north end of the Magdalena Range and on the east 

side of the Granite Mountain area. They are also 

found as small inclusions in the granite. Their relations with the more abund-antly exposed argillite have 

not been determined, but it seems reasonable to r;egard 

them as roughly equivalent · in age. The argillite and 

schist are clearly the oldest rocks of the district, as· 

they are cut by all the pre-Cambrian igneous rocks, 

which also contain many inclusions of argillite and 

schists. Such inclusions are well-shown in both the 

gabbro and granite east of Kelly. 

·The argillite in general strikes northward and dips 

vertically or steeply to the east. In the southernmost 

exposure it strikes N. 20° E., in the exposure northeast 

of Kelly N. 25° W., at the Graphic tunnel N. 2°-16°. W., 

and east of Hardscrabble Camp N. 25°-30° E. There 

is no evidence of local folding, and the different exposures are regarded as parts of. one thick formation, 

neither the top nor the bottom of which is defined. The 

thickness exposed in any one area may be as much as 

2,000 feet. 

Where considerably sheared along premineral faults, 

the argillite is converted into sericite schist. The best 

exposures of schist, however, are at the north base of 

the main range and across the valley at the east end of 

the.bedrock exposures in the northern or Granite Mountain area. At both places the schist is similar in atti4 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore deposits of New Mexico · U. S. Geol. Survey Prof. Paper 68, pp. 243-245, 

1910. 11 Idem, p. 245, 
8 MAGDALENA MININ·G DISfrRICT, NEW MEXICO 

tude to the argillite; in the first exposure it strikes 

N. 25° E. and dips 87° E., and in the second it strikes 

N. 3° W. and dips 43° E. The schist, like the argillite, 

is cut by granite, pegmatite, and diabase~ but the exposures are too few to permit a clear explanation of its 

higher degree of metamorphism. It is also locally 

sheared and faulted. 

LITHOLOGY 

The typical argillite is prevailingly rather light 

greenish gray, fine-grained to microgranular, a:hd rather 

thin bedded. Local varieties are dark gray. Weathered surfaces show distinct banding of relatively light 

and dark layers, mostly less than an inch thick. Cross 

bedding on a small scale is commonly present. The 

mineral grains are too S'mall to be identified without a 

miscroscope, but the rock has a distinctly siliceous appearance in contrast with the darker-green gabbro and 

diabase. It is free from cleavage but full of small 

intersecting fractures, and thus weathers into small 

angular blocks. At the southern exposure, where shattering along a strong fault zone is excessive, these 

blocks are so small that the local talus resembles 

crushed stone. Much of the argillite in this area is 

bleached and silicified and . forms . cliffs and pinnacles. 

The argillite close to the monzonite contact near the 

Graphic tunnel is also bleached and has the appearance 

of hornfels. 

Microscopic study indicates that the principal minerals are quartz and sericite, with smaller amounts of 

orthoclase, green biotite, and chlorite. In so;me specimens clear quartz and feldspar in irregnlar grains are 

. as much as 0.00 millimeter in diameter; but in others, 

which contain less mica, they are only 0.01 milli·meter 

in diameter, indicating that the larger size is probably 

a result of recrystallization. Some quartz and orthoclase grains are clear, but other orthoclase grains and 

even some of the quartz grains are largely or even 

wholly replaced by sericite. Biotite and chlorite that 

is probably derived from biotite form evenly dis- . 

tributed small flakes and, together with a little epidote, 

also form ve.inlets, which will be discussed later. The 

minor constituents are magnetite, plagioclase, apatite, 

zircon, and locally calcite that forms small irregular 

patches. 

The schist, which is micaceous with the exception of 

a small inclusion of hornblende schist In granite near 

the Anchor •mine, ranges from banded siliceous rock in 

the exposure on the north end of Magdalena Range to a 

very schistose sericitic rock in the Granite Mountain 

area. The siliceous variety consists of alternating lightgray layers one-fourth of an inch thick and thinner 

brown and green layers. Its weathered surfaces show 

distinct cross bedding. · In thin section it consists 

mainly of quartz, orthoclase, chlorite, and muscovite, 

with minor amounts of magnetite, zircon, and rutile. 

The quartz and orthoclase grains ~.re irregular and 

interl0cked and have a maximum diameter of 0.02 millimeter but average much less. The quartz grains are 

free from strain. The orthoclase grains are in part 

clear and in part sericitized. Chlorite and muscovite 

with associated magnetite are segregated in rather 

poorly defined bands and account for the brown and 

green layers of the rocks. The zircon grains are rather 

abundant and well-rounded. Rutile forms· radiating 

needles in chlorite. 

The sericitic schist is silvery gray and finely foliated. Quartz grains are visi~le on surfaces across the 

foliation. In thin section irregular interlocking 

grains of quartz with oriented muscovite predominate, 

and biotite, magnetite, chlorite, apatite, and rutile are 

accessory: The quartz has strain shadows, which indicate shearing subsequent to the crystallization of the 

schist. · · 

GABBRO 

DISTRIBUTION AND OCCURRENCE 

Altered gabbro or coarse-grained diabase that is intrusive into the argillite but older than the granite has 

been mapped in several areas. The largest -mass and 

the one showing age relations best is that just northeast 

of Kelly. This ·mass is bounded in part by faults, so 

its original outline cannot be readily · interpreted; but 

its ~estern boundary, __ which roughly parallels the 

strike of the argillite, and its northerly trend suggests 

that it is a sill-like mass intruded before the argiliite 

was upturned. It is doubtless continuous beneath the 

overlying rocks with the smaller areas on the slope to 

the east. The exposure 2,000 feet northeast of the 

Graphic tunnel is an altered dike 250 feet thick, of 

northwest trend. It is cut off on the northwest by 

monzonit~ and on the southeast by faults, but it may 

be continuous underneath the Pennsylvanian formations with the remnant of a much larger dike exposed 

just east of the crest of the range. 

LITHOLOGY 

The gabbro · is very similar, except in coarseness of 

grain, to the diabase that forms dikes in granite. On 

fresh surfaces it is dark green to black but on weathered 

surfaces is bleached to gray. Cleavage surfaces of a 

dark prismatic mineral can be recognized. A thin 

section of the altered gabbro dike northeast of the 

Graphic tunnel shows a co~fusing mass of plagioclase 

and uralitic hornblende with accessory green biotite, 

magnetite, leucoxene, apatite, chlorite, epidote, and 

some calcite. The plagioclase forms about 70 to 90 

percent of the rock and consists of microgranular 

oligoclase in laths 2 to 3 millimeters long Much of it 

is untwinned, but some grains still show twinning and 

zoning of the original more calcic plagioclase, which 

~as been altered to oligoclase. Much of the oligoclase 

is peppered with fine-grained magnetite, which may 

represent iron enclosed in the original plagioclase or 
GE OLOGICAL SURVEY 

108° 

Afte r geo logic map of New M ex ico, by N. I{ Darfon, U.S.Geol. Survey 1928 

except f or det a i ls around Magda len 

PLAINS OF SAN AGUSTIN Q.a l 

w 

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10 () 

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MAP OF REGION URROUNDJ1 ~ TUE M GDALE 

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PROFE SlONAL PAPER 200 PLATE 1 

EXPLANATION 

D . 

. 

L basalt a rrert:ie:ryto Qua: rnru:y) 

LZIJ w een an . Phocen.e sedim 1.ts 

In rocks (T r tia:ry(r' l) 

.r t:aJ eous ~ and. Tertiruy 

volcanics 

arboniferous and Mesozoi 

edim. nts 

Pr -Cmnbri 

~ g.rani and gillit 

METERS 

3 ,000 

2,000 

Oat for sectionA- 'from Magdalena Range 

eas w ard rn1 d byKirk Bryan 

Fl!:AT R 

ln11et 11b wa the location in ew .Me:rioo of 1be area represented by plate l. In aeclioo A- A', p represents pr - amLriun; , a rh nifcr .. ,. s1ra1:1; Tv, Ter1iary volcani · rocl• ; Tr, a r ilistant pink rhyolili' ; T f, lhe 

an Fe furm lion; Qal, l'leiat t- n toN nt alluviu111 . 9--42 (F a p. 8) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 3 

A. KELLY, MAGDALENA MOUNTAIN, AND ELEPHANT BUTTE, LOOKING WEST FROM DUMP OF JUANITA TUNNEL . 

. Magdalena Mountain, in right middle ground, is also called Picture Mountain because the round patch of talus surrounded by brush on the northeast slope resembles the profile of a human head. The mountain is eapped with pink rhyolite, which merges into the dike that forms the high cliff on the east slope. The dike strikes north, parallel to the plane of the picture. The horizontal layers to the left of the dike represent the glassy 

top of the upper andesite. The same formations constitute Elephant Butte, on the extreme left, and the hill in the southwest corner of the distt·ict (see pl. 2). The low mounds in the valley between Magdalena 

Mountain and Elephant Butte arc remnantA of pediments equivalent to the lower pediments within the district. 

B. NORTHERN PART OF MAGDALENA RANGE, LOOKING EAST FROM MAGDALENA MOUNTAIN. 

Shows west-sloping spurs and foothills with a broad alluvium-covered rock plain or pediment in the foreground. Town of Kelly in center. 
,.· 

I 
PRE-CAMBRIAN :ROCKS 

introduced during alteration. The uralitic hornblende -

forms roughly rectangular grains as much as 2 millimeters in length and, together with enclosed g~ains oi 

magnetite, may be secondary after augite. Much 

hornblende is also found in microscopic needles that 

. impregnate the plagioclase. Leucoxene forms irregular grains as much as 2 millimeters long and evidently 

represents original grains of ilmenite. 

FELSITE 

DISTRIBUTION AND OCCURRENCE 

Felsite (aporhyolite) is found principa~ly in. a triangular area east of Hardscrabble Camp, but small 

areas -of it are also found just northeast of Oak Spring 

and near the extreme southeast corner of the district ; 

and a few dikes, or faulted parts of one dike, cut the 

argillite and gabbro ·near the Gern1any mines, east of . 

Kelly. The southernmost mass is too poorly exposed 

to deserve further attention. 

The two northernmost masses are evidently parts of 

an intrusive plug in argillite partly concealed by a 

cover of Kelly li~estone, which there, as elsewhere, 

rests on a nearly plane erosion surface. The contact 

of this plug with argillite is nearly vertical, and 1ts 

intrusive character is best shown near the 7,700-foot 

contour where small obscure felsite dikes of east-northeast trend, too small to be shown on plate 2, cut the 

argillite. Inclusions of argillite, sorne of considerable 

size, are found near the tunnel at the 7,600-foot contour 

in t~e west-central part of the felsite mass, and other 

remnants of argillite are found close to the contact · 

with overlying limestone along its south boundary. 

The main felsite mass is cut off on . the east by preCambrian granite, which is clearly intrusive into the 

felsite, although the contact is nearly horizontal. The 

northernmost part of the felsite is cut by Tertiary ( ? ) 

granite, and along the southwest it is cut by Tertiary 

( ? ) monzonite. 

As the steep to vertical contacts between the felsite 

mass and argillite are nearly at right angles to the 

strike. of the upturned argillite beds, the sequence of 

the .felsite intrusion and of the upturning is obscure; 

but, as the relations of felsite and argillite to the preCambrian granit~ are identical, the intrusion of the 

felsite before upturning seems likely. 

LITHOLOGY 

The fresh felsite is· dark purplish to black, dense to 

extremely fine grained, and finely porphyritic; but 

along the veins on the 8,721-foot summit north of the 

Ambrosia mine it is bleached almost white. On 

weathered surfaces it bleaches to light gray and locally 

to pale pink. Its appearance on both fresh -and weathered surfaces is much like the argillite; but it can be 

distinguished by its porphyritic texture and bv the 

absence of banding, which is usually present i~ the 

200889-42-2 • 

argillite., Its phenocrysts· are feldspar and quartz in 

·grains as large as 3· millimeters in diameter. 

Thin sections show phenocrysts of quartz, oligoclase~ 

and perthitic orthoclase embedded in a microgranular 

groundmass of feldspar and quartz. The quartz 

phenocrysts are in general well-rounded by resorption 

and show embaym~nts a~d reaction rims. They are 

also much · fractured and are sealed with fine-grained 

quartz. They show strain shadows, and in some sections the greater part of the quartz phenocrysts ha vt~ 

been · recrystallized into mosaics. The oligoclase is 

much sericitized in most sections an£1 is the only feldspar present among the phenocrysts in some sections. 

In others orthoclase, clouded with dustlike particles and 

less sericitized than the plagioclase, is the only feldspar. 

The groundmass is a very fine grained mosaic. The 

principal minerals are qua.rtz and feldspar with accessory apatite, ilmenite, magnetite, and very little zircon. 

In some sections the groundmass is much sericitized 

and silicified. It is crisscrossed by many veinlets that 

contain green biotite, chlorite, iron oxide, apatite, and 

SBricite. Green biotite is also disseminated and in local 

segregations. Apatite forms irregular grains assocjated with green biotite and magnetite and is distinctly 

secondary. · Epidoteis very scarce. -

The local dominance of plagioclase phenocrysts :mg~ 

gests that the original rock was da_cite, at least in part; 

but the uncertainty as to whether, most of the irun, 

magnesia, and: titanium, as well as some silica, have 

been largely introduced or merely rearranged renders 

an exact classification :ln1possible.. So the rock is designated by the. field name felsite rather than aporhyolite 

or apodacite. 

GRANITE 

DISTRIBUTION AND OCCURRENCE 

The pre-Cambrian granite covers the largest surface 

of any fonnation in the district and closely resembles 

-pre-Cambrian granite found elsewhere in New Mexico.6 

It forms the east slope of the main Magdalena Range 

from the extreme north end southward beyond the 

limit~ shown on plate 2, and small patches of it have 

been uncovered in fault blocks on the west slope by 

erosion ot" the Carboniferous rocks. The westernmost 

exposure is near the Germany mines, east of Kelly. 

None is found in the Granite Mountain area. 

The relations of the granite to argillite, schist, gabbro, and felsite are shown to be intrusive, although 

locally . the presence of fine-grained granite near the 

finely granular facies of the felsite at first gives the 

impression that the two rocks grade into each other. 

The northern outcrop of schist is cut by a poorly exposed pegmatite dike composed of white albite, quartz, 

and small flakes of mica, the only granite pegmatite 

found in the district. Aplitic stringers cut the gabbro 

dike northeast of the Graphic tunnel, and inclusons of 

6 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore de~ 

posits of New Mexico: U. S. Geol. Survey Prof. Paper 68, p. 247, 1910. . I 
10 MAGDALENA MININO DISTRICT, NEW MEXICO 

argillite and gabbro are found in the granite that 

forms part of the pre-Cambrian block east of Kelly. 

Small dikes of granite, one of which is shown on 

plate 5, A, cut the argillite in the southeastern part of 

the district and are cut off sharply at the basal contact 

of the Kelly limestone. These dikes are relatively 

coarse grained, some grains being as much as 6 millimeters inJ diameter. The dikes have a maximum width 

of 4 feet, but most of them are only a few inches wide 

and are parallel-to the banding in the argillite. South 

of the Germany mines a dike of fine-grained granite 

or aplite about 40;. feet thick extends beside a diabase 

dike in gabbro. 

The contact of the granite with the older rocks is 

remarkably regular on the whole, although many ·short 

apophyses extend upward from its general level. 

Along the northern part of the range the contact along 

the east edge of the felsite is nearly horizontal, and 

scattered exposures of the contact with older rocks on 

the west slope near Kelly and in the southern part of 

the district indicate a westerly slope approximating the 

dip of the younger sedimentary rocks. (See pls. 4 

and 5, A.) 

The abundant fractures in the _granite belong to 

three principal sets-one of northerly trend, one of 

northeasterly trend, and one about parallel to the upper 

contact. The more conspicuous fractures of the northtrending set dip east, about normal to the upper granite contract, and in many places they are so closely 

spaced as to form sheeted zones, which when viewed 

from a neighboring spur strongly resemble an eastdipping stratified rock. The plane to slightly curving 

steep, east slopes of spurs in the ·main granite area 

have resulted from erosion along these fractures. The 

more conspicuous, fractures of the northeast-trending 

set dip steeply to moderately northwestward, .but fractures with southeasterly dips are conspicuous in places. 

Gulches of northeasterly trend have been formed by 

erosion along this set. The set parallel to the upper 

contact is not so conspicuous on the east side of the 

range, as it has large angles to most of the slopes and 

is obscured by debris; but some of the slopes on the 

east sides of north-trending gulches are evidently controlled by it. Fractures of westerly and northwesterly 

trends are also present and coincide with the prevailing 

trends of pre-Cambrian diabase dikes and some of the 

transverse gulches. Besides these sets there are many 

minor fractures that break the granite into small blocks 

of various shapes. 

Some fra9turing obviously took place in pre-Cam- · 

brian time, as some fractures are filled with pre-Cambrian diabase dikes; ·but intense fracturing also took 

place during the disturbances that produced faults in 

Laramide and Tertiary (?)time (pp. 57-73). Many of 

the more conspicuous fractures are so closely associated 

with clearly · defined faults cutting the Carboniferous 

rocks that they are consistently correlated with those 

faults. The set that parallels the top of the granite~ 

however, suggests that it may have been formed in preCambrian time in the same way as the nearly horizontal 

fractures ir:t granit.e quarries-by expansion in response 

to the decrFase of load through erosion or in response 

to superficial temperature changes. Erosion along 

such fractures may account for the smooth granite surface on which the Kelly limestone rests. The minor 

fractures, rhich have no apparent relation to fractures 

in overlying limestone,, suggest at once that the granite 

surface was much fractured before the limestone was 

deposited; but deformation of massive granite may 

produce m~nor fr~ctures that do not extend into adjacent bedded limestone. In short,- the only. fractures 

that ca~ be1 called pre-Cambrian with any assurance are 

those that contain diabase dikes and veinlets of minerals attributed to deposition at the end of pre-Cambrian igneous activity (see pp. 12--13) . . 

This failure to recognize different fracture sets of 

pre-Cambrian age, especially any that have been called 

primary joints by Cloos 7 adds to the difficulty of recognizing the form of the granite mass and the process 

of its intrupion. Its contacts with older pre-Cambrian 

rocks imply that the upper surface of the granite was 

determined by fractures (the "Q" joints of Cloos 8 ) 

nearly at right angles to the upturned bedding of the 

argillite. ffhis regularity of contact, together with the 

scarcity of granite dikes or apophyses that extend up~ 

ward into the older rocks, suggest that the granite has 

a sill~like or tack-shaped form; 9 but the failure to 

find a floor\ to the granite mass weakens this suggestion. 

As the granite mass, so far as known, forms the entire 

east slope of the range, it is apparently very thick; but, 

owing to steplike downfaulting to the east; its apparent thickness is somewha_t exaggerated. Further 

specl.Jlation should be deferred until a much larger area 

has been carefully studied. 

LITHOLOGY 

The pre-Cambrian granite is prevailingly pink and 

fine g'rain~d, even a long way from its intrusive contacts, although it contains some small, rather coarse 

grained patches near those contacts. On . the lower 

slopes eas~ and southeast of Tip Top Mountain its 

grain is n9t quite so fine. On weathered surfaces it 

has faded 1 to pinkish gray and may even be stained 

yellow and buff, and some weathered surfaces ha.ve a 

resemblande to feldspathic sandstone. It consists 

essentially I of pink feldspar and colorless quartz with 

small to negligible amounts of biotite in small, dark, 

T Cloos, Ernst, in Balk, RoQert, Primary structure ]n granite massives: 

Geol. Soc. A.m~rica Bull., vol. 36, pp. 679-696, 1925. 

s Idem, p. 6B6. 

9 Chamberlin, R. T., Whittling down the batholiths: Geol. Soc. America 

Bull., vol. 38,) p. 109, 1927; Pan-Am. Geologist, vol. 47, p. 65, 1927. 

Chamberlin, R. T., and Link, T. A., The theory_ of laterally spread]ng 

batholiths: Jqur. Geology, vol. 35, pp. 319-352, 1927. 
PRE-CAMBRIAN ROCKS 11 

knotty aggregates. Biotite is almost entirely absent 

at the north ena of the range, . where the granite exposed is dose to its pre-Cambrian roof, but is more 

conspicuous in the central part of the district, where 

the roof and uppermost part of the granite have been 

removed. Because of the fineness of grain, scarcity ·of 

biotite, and abundance of fractures, the granite characteristically weathers into sharply angular blocks, in 

marked contrast with the coarser-grained Tertiary (?) 

granite, which weathers into spheroidal blocks, as 

shown on plate 17. On the lower, eastern slopes, where 

the pre-Cambrian granite is not so fine grained, its · 

·\veathered fragments have somewhat rounded corners 

but still maintain a marked contrast with the 

weathered Tertiary ( ? ) granite. 

The microscope shows the essential constitutents to 

be quartz and microperthitic orthoclase, in large part 

micrographically i11tergrown~ as shown on pla.te 6, A. 

Albite-oligoclase amounts to less than 5 percent of the 

rock. Conspicuous in the rock are secondary green 

biotite and several minor minerals, which are discussed 

below. 

Only a few quartz and microperthite grains are free 

from micrographic intergrowth. The independent 

quartz grains are irregular ·to rounded, 1 millimeter 

and less in diameter, and n1any have undulatory extinction. In places quartz forms clusters, as if remnants 

of quartzite. Quartz is apparently the earliest of the 

minerals. It forms rounded inclusions in the albiteoligoclase as well as in the microperthite; and in the 

quartz clusters the grains are commonly separated and 

some are even cut and partly replaced by interstitial 

microperthite, as shown on plate 6, B. The amount of 

replacement in this granite is not evident. Graphic 

intergrowths of quartz and albite are believed · by 

Gilluly 10 to be a product of replacement in the albite 

granite near Sparta, Oreg., and the clusters of quartz 

v;ith interstitial microperthite likewise suggest that the 

pre-Cambrian granite at Magdal~na is a product in 

part at least of replacement of some earlier quartzose 

rock. No such rock, however, was recognized in the 

pre-Cambrian rocks within the district. 

A striking feature of the granite is the secondary 

green biotite, which occurs disseminated, in clusters of 

small flakes, in veinlets, and in stringers that are interstitial to quartz and feldsparA In only one section 

vms pale-brown biotite found, and it also occurs in 

clusters. Many of the clusters grade into veinlets. 

Biotite is commonly in association with magnetite, 

and some clusters and veinlets also contain one or n1ore 

of the following minerals : hastingsite, apatite, zircon, 

epidote, allanite, calcite, and fluorite. Hastingsite is 

commonly present though scant. Tlie mode of occurrence of biotite and its associates in veinlets and clusters and the absence of any trace of a former ferroto Gilluly, James, Replacement origin of the albite granite near Sparta, 

Oreg. : .u. S. Geol. Survey Prof. Paper 175-C, pp. 72-73, 1933. 

magnesian mineral , show that they are secondary 

rather than original constituents. One thin section 

showed a cluster of biotite flakes replaced by a network 

of iron oxide and muscovite. 

A thin section from an aplite dike shows the aplite 

to be similar to t.he main mass of granite and to consist chiefly of quartz in irregular grains and in poorly 

developed graphic. intergrowth wth microperthite. 

llowever, the primary minerals have been largely re-

·placed by secondary quartz, which forms rosettes of 

radiating structure and has produced a well-developed 

micrographic intergrowth of quartz and ·feldspar that 

now predominates throughout the rock. The radial 

quartz is · accompanied by green biotite and a small 

amount of calcite. A quartz veinlet that cuts the 

rosettes has been itself fractured and recemented by 

biotite and a noteworthy amount of calcite. (See pl. 

6, 0.) Sericite is present only in negligible quantities. 

The replacement of quartz by feldspars, the pres- · 

ence of clusters and veinlets of green biotite, hastingsite, epidote, allanite, calcite, and apatite, and the replacement of aplite by quartz, largely grouped in 

rosettes, whic}f in turn were subsequently fractured 

and recemented .by biotite and calcite, are clear evidence of partial replacement and probably profound 

alteration of the original granite. The clusters and 

/ veinlets of green biotite and associated minerals in 

the argillite and felsite, and, to anticipate, in the diabase dikes that cut ·the granite, as well as in the granite, show that this kind of hydrothermal alteration 

was regional rather than formational. This regional 

alteration will be discussed after the diabase has been 

described. 

CHEMICAL COMPOSITION AND . CLASSIFICATION 

A chemical analysis of a sample of the pre-Cambrian 

granite from the head of Anchor Canyon, south of its 

contact with the Tertiary ( ? ) granite, is recorded 

below. In the quantitative classification · it corresponds to 1.3.1.2., but the amount of secondary changes 

in the rock prevents a definite classification. The high 

silica content is expressed mineralogically by the unusually large amount of quartz·, and the large an1ount 

of ferric iron is accounted for by the green biotite and 

associated magnetite. The titania (Ti02) is also probably present chiefly in the biotite. The high ratio 

of potash tb soda reflects the marked predominance 

o:f orthoclase microperthite over albite-oUgoclase. 

Analysis of pre-Cambrian granite 

[A. R. Ferguson, analyst, New Mexico School of Mines, 1929] 

Si02-- ________ -- -- ---

· AiaOs- ------------ ---

Fe203 ___ -- -- -- -- -- -- -

FeO __________ -- -- -- -

. MgO _______ -- -- -- -- - cao _____ _: __ ________ _ 

Na20- __ -------------

75 .. 73 

11. 93 

2. 19 

. 67 

.29 

. 83 

2. 57 

K20. ___ -- __ -- -- -- ---

H20-_- -------------

H20+ __ -- -- -- -- -- --- Ti02- _____ -·- ________ _ 

C02 ________________ _ 

4.79 

. 05 

• 43 

. 50 

. 05 

100. 03 
12 MAGDALENA MiNING DiSfl'RICT, NEW MEX1C0 

DIABASE 

DISTRIBUTION AND OCCURRENCE 

A large group of diabase dikes with a general westerly trend is present on the east slope of the range and 

also in t.he small areas of pre-Cambrian rocks east of 

I\:elly. There are other small groups with dominant 

westerly trends near the Hardscrabble mine, in the 

north end of the range, and near the southeast corner of 

the district. Diabase that cuts schist is exposed in the 

arroyo on the east side of the Granite Mountain area. 

The main group of dikes lies transversely to the strike 

of the argillite and presumably to the major axis of 

the domed or upwarped area from which the preCambrian cover of the granite was largely removed 

before the deposition of Carboniferous rocks. 

The prevalence of debris in the pre-Cambrian areas 

renders it difficult to trace the diabase dikes for any 

considerable. distance, or te correlate exposures on opposite sides of faults; nevertheless, the discontinuity of 

some of the larger dikes is remarkable, especially that 

of the largest dike found. This dike is about 4,000 

feet south-southeast of Tip Top Mountain. It is 200 

feet thick and can be traced eastward for a few hundred feet from its contact with the overlying Kelly 

lhnestone without appreciably diminishing its width, 

but all · traces of it abruptly disappear. Its possible 

westward continuation through granite on the west 

slope of the range may be concealed by debris, and it 

may be represented by the remnants of dikes in the 

small pre-Cambrian areas east and northeast of Kelly. 

·Such a correlation would help to show the amounts 

of heave or horizontal offset along intervening faults, 

but the evidence is too meager to be reliable. 

LITHOLOGY 

The diabase comprises coarse-grained and finegrained varieties, both of which in a few dikes have 

been sheared into chlorite schist. Both varieties form 

small as well . as large dikes and have no apparent 

regularity in .distribution. The coarse-grained diabase 

is dark greenish gTay, and none o:f its minerals are 

identifiable megascopically on unweathered surfac~s, 

although dark-green prismatic cleavage surfaces of a 

Jwrnblendic mineral are conspicuous. On weathered 

surfaces the bleaching of altered or replaced feldspar 

brings out the diabasic texture except where alteration 

is extreme. The fine-grained variety is grayish black 

to greenish gray, and the darker facies shows minute 

glistening cleavage surfaces of biotite. 

Thin sections show that the dikes arc. almost completely altered. In the speci~en apparently least altered, collected on the blunt east spur of the peali eastsoutheast of Tip Top Mountain, the microscopic diabasic texture is distinct; but plagioclase is represented 

mainly by albite-oligoclase in well-developed twinned 

laths up to 2 millimeters long. It is intercrystallized 

with hornblende and in part replaced by it; the hornblende in turn is in part chloritized. ~lore commonly 

the diabase consists of a confusing mass of green hornblende, with smaller amounts of chlorite, epidote, ~nd 

zoisite, granular aggregates and ramifying veinlets of 

albite, and leucoxene. The diabase shows only small 

scattered remnants of the original pyroxene and ilmenite and the usual unaffected crystals of apatite and zircon. Sericite was prominent in only one· thin section. 

Green biotite, similar to that in the other pre-Cambrian 

rocks, was present in another. The. thoroughly sheared 

dikes consist 1nainly of chlorite, with irregular stringers 

of sericite and quartz. Impregnating grains and veinlets of quartz and calcite have been noted in some thin 

sections. A thin section of the grayish-black, finegrained diabase consists essentially of zoisite, green 

biotite, chlorite, hornblende, and epidote, with only a 

scattering of granular feldspar, probably albite, ilmenite replaced .by lelicoxene, and probably quartz. 

This rock is distinctly different both megascopically 

and m.icroscopiciDlly from the diabase dikes and. ma.y be 

an altered pre-Cambrian lamprophyre dike. 

The green biotite in these rocks is also of interest. 

It is disseminated in two of the specimens studied and 

shows no evidence of its age r<;].ations to the other 

minerals; but its green color is indicative of its relationship to the green biotite found in the other preCambrian rocks and, in view of the association of epidote with the biotite in the granite, it is probable that 

the epidote and zoisite in the diabase, as well as the 

general alteration of the diabase, are contemporaneous 

with the biotite. 

BIOTITIZATION OF THE PRE-CAMBRIAN .ROCKS 

A striking feature of the pre-Cambrian rocks of the 

district is the general presence of green biotite in veinlets as well as in disseminated grains. rrhe biotite and 

associated minerals are probably secondary in origin. 

The presence of this biotite in all of the pre-Cambrian 

rocks and its absence from the Paleozoic and Tertiary ( ~) formations show that it was :formed in preCambrian time, and its unusual but uniform character 

points to its probable development at one time, after 

the intrusion of diabase. It is ;most commonly associated directly with magnetite, but in the granite it is 

also accompanied bY. hastingsite, epidote, zircon, allanite, and apatite and rarely by fluorite. Apatite 

associated with green biotite and magnetite was unusually abundant in one section of felsite. Chlorite, 

which is also abundant in the felsite and argillite, may 

represent altered biotite. In the argillite and felsite 

·the especially common mineral is sericite, and in the 

gabbro and diabase the common secondary products 

are epidote and zoisite. 

Development of green biotite in so many different 

kinds of rock evidently required ~niformity of temper~ture, pressure, and composition of the sour~e rna-
PRE-CAMBRIAN ROCKS 13 

terial. These rocks in general show no signs of 

dynamic metamorphis.m, other than the conversion of 

a few diabase dikes into chlorite schist; the biotite is 

therefore to be attributed to solutions that acted under 

uniform physical conditions throughout the area. To 

the unaided eye the granite and felsite appear unaltered except along Tertiary . ( ? ) veins. Allanite, 

hastingsite, zircon, apatite, and fluorite in association 

with biotite are co:rrullonly ascribed to a higher temperature of deposition than the common hydrothermal 

minerals. Biotitization is one of the common modes 

of rock alteration in the Engels mining district, California,11 and its origin is similarly as.cribed. Knopf 

and Anderson 12 point out that rocks in which biotite, 

actinolite, and plagioclase have formed metasomatically "are bound to look fresh and unaltered." Judging from the wide distribution of the green biotite in 

the Magdalena district, these high-te,mperature solutions unde·r great pressure permeated even ·the most 

minute cracks and thoroughly soaked.the country rock. 

The biotite and associated minerals are therefore found 

in veinlets, clusters with small apophyses. and disseminated grai'ns that have replaced the primary minerals. 

F'urthermore, the distribution of the disseminated and 

clustered biotite is _ _irregular (pis. 7, B, 0) and · in 

marked contrast to the primary biotite of · ordinary 

granite. ·Now here in the granite was residual material 

such as spongy ·iron oxide found to show the former 

presence of original ferfomagnesian minerals, and it. is 

not very likely that residual iron oxide could have been 

completely removed. The evidence as a whole, therefore, clearly indicates the secondary origin of the green 

biotite and associated minerals. 

Whether other secondary minerals disseminated 

through the rocks, but n~t found with the bi~tite in 

veins and clusters, are contemporaneous with the bio.:. 

tite is not certain. It seems probable that the composition of the solutions that first deposited the veinlets 

and clusters of biotite and associated minerals was 

sufficiently changed by reaction with the original rock 

minerals to produce different groups of disseminated 

secondary minerals, depending upon the character of 

the permeated country · rock; thus in argillite and 

felsite the most abundant disseminated secondary mineral is sericite, whereas in the gabbro and diabase the 

most abundant are epidote and zoisite . . These disseminated minerals may also be interpreted as the products of an earlier stage of hydrothermal alteration 

from that represented by the biotite. The evidence 

of their relations to the biotite is not conclusive, but 

the association of epidote with the biotite in veins at 

least suggests that the silicate veinlets and the disseminated secondary minerals are contemporaneous. 

u Knopf, Adolph, and Anderson, C. A., The Engels copper deposits, 

California: Econ. Geology, vol. 25, pp. 14-35, 1930. 13 Idem, p. 33. 

In th~ gabbro and diabase it was evidently hornblende, i:h which the biotite is enclosed, and chlorite 

that furnished most of the constituents for the development of biotite except potash, which must have been 

introduced; in the granite, and perh~ps in the argillite 

and felsite also, the bulk of all the constituents of 

biotite must have been introduced. The presence of 

hastingsite and of the quartz rosettes and veinlets in 

the aplite dikes indicates that the high-temperature 

solutions introducing these constituents probably represented the-final stage of the pre-Cambrian igneous 

activity. 

CORRELATION 

The pre-Cambrian rocks and their succession in the 

Magdalena Range are so' similar, except perhaps in degree of metamorphism, to those found in other parts 

of the State and in the Front Range of Colorado that 

there can be little question of their direct correlation. 

Lindgren, Grato:n, and Gordon 13 found in their investigation covering the State that the oldest rocks everywhere are sedimentary and include quartzite, mica 

schist, limestone, and slate. They also t'eport 14 that 

some of the "greenstone. schist" · or argillite in the 

Magdalena district was "derived from apparently tuffaceous" sediments, but in our microscopic work ~e 

have not recognized pre-Cambrian rocks of tuffaceous 

origin. They suggested correlation with the quartzitTc 

Pinal schists of southeastern Arizona. Tentative correlation may also be made with the Idaho Springs 

formation of the Front Range of Colorado/5 which 

has a similar range in composition. 

The early gabbro of the Magdalena district may 

correspond in age to ·the Swandyke hornblende gneiss 

of Colorado/ 6 which, according to Lovering, represents originally gabbroic and basaltic rocks in part at 

least intrusive into the Idaho Springs formation, although it may ~lso represent originally calcareous· 

, sedimentary rocks. The felsite is not so readily correlated. Metamorphosed volcanic rocks of rhyolitic 

character are present in the Gunnison River series of 

Colorado, but they are older than the basic rocks of. 

the series, whereas the reverse order holds at 

Magdalena. 

Regional metamorphism in Colorado was accompanied by the early stages of granitic intrusion, which 

was followed in turn by the main batholithic intrusion 

of Pike's Peak and equivalent granites and later more 

local granites.17 On the basis of general structural 

13 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore deposits of New Mexico: U. S. Geol. Survey Prof. Paper 68, pp. 26-29, 

1910. 

14 Idem, p. 245. 15 Lovering, T. S., The geologic history ' of the Front Range, Colo. : 

Cqlorado Sci. Soc. Proc., vol. 12, No.4; pp. 64-65., 1929. 16 I.Jovering, T. S., op. cit., pp. 65-66 ; Geolog.y and ore deposits of the 

Montezuma quadrangle, Colo. : U. S. Geol. Survey Prof. P~per 178, pp. 

10-11, 1935. Colorado geologic map, U. S. Geol. Survey, 1935. 

n Lovering, T. S., The geologic history of the Front Range, ColQ. ; 

Colorado Sci. Soc. Proc., vol. 12,' No. 4, pp. 67-74, 1929, 
14 MAGDALENA MINING Dlsri'RICT, NEW MEXICO 

evidence, the granite at Magdalena is more nearly 

equivalent to these local granites, which were intruded 

in the zone of fracture after regional metamorphism 

had ceased, although they contributed in some degree 

to the injection of the older rocks with granitic material. The almost negligible amount of typical schist 

in the :.Magdalena district implies that the district 

could _have been only on the outskirts of an area of 

intense regional metamorphism. 

Diabase dikes with structural relations similar to 

those in the Mftgdalena district are :found in the 

Cripple Creek district of Colorado,t8 and Gruner 19 

reports late "basic" dikes intruding the pre-Cambrian 

granite in the southern part o:f the Taos Range, 

N.Mex. 

The metamorphosing influence o:f the granite was 

not extreme and may have been masked in part by 

later mBtamorphism. Only in the northern part of 

the district, where the argillite has been converted 

into schist and cut by pegmatite, has .pre-Cambrian 

metamorphism been strong. Comparison with other 

pre-Cambria areas, notably the Front Range o:f Colorado,20 suggests that the local granite intruded into 

the zone of fracture represents the latest stage o:f a 

complex cycle o:f metamorphism. and batholithic intru-. 

sion. Final adjustments after the granite intrusion 

produced profound fractures normal to the top of the 

granite and admitted the diabase dikes. The subsequent biotitization of all pre-Cambrian rocks marked 

the latest expression of pre-Cambrian activity. 

CARBONIFEROUS SYSTEM 

By V. T. STRINGFIELD, A. H . KOSCHM:ANN, and G. F. LOUGHLIN 

Although older Paleozoic sedimentary rocks are 

widespread in southern New Mexico, only the Carboniferous system is represented in the Magdalena district. During pre-Carboniferous time the surrounding 

regi9n was evidently subjected to continuous erosion; 

and the pre-Cambrian rocks were worn down to a 

nearly level surface, upon which the Carboniferous 

rocks were deposited. These rocks comprise four 

formations-the Kelly limestone, o:f Mississippian age; 

the Sandia formation and Madera limestone, of Pennsylvanian age; and the Abo sandstone, of Permian age 

(pl. 8). 

KELLY LIMESTONE (MISSISSIPPIAN) 

The Kelly limestone, originally called the "GraphicKelly limestone" by Herrick,21 after the two leading 

18 Lindgren, Waldemar, and Ransome, }j .... L., Geology and gold deposits 

of the Cripple Creek district, Colo. : U. S. Geol. Survey Prof. Paper 54, 

p, 56, 1906. 19 Gruner, J. W., Geologic reconnaissance of the southern part of 

the Taos Range, N. Mex.: Jour. Geology, vol. 28, pp. 731- 742, 1920. 20 Lovering, T. S., op. cit., pp. 61-74. 21 Herrick, C. L., Laws of formation of New Mexico mountain ranges: 

Am. Geologist, vol. 33, p. 311, :t,9Qi. 

mines of the district, was later renamed the Kelly 

limestone by Gordqn,22 after the town of Kelly. It is 

by far the most productive ore zone in the district: 

It is from 9o to 135 feet thick, but this variation in 

thickness-is due, in large part at least, to bedding faults 

that commonly escape recognition except in mine workings. The Kelly limestone rests directly upon the very 

gently undulating pre-Cambrian surface, as shown in 

figurer. 

DISTRIBUTION 

The Kelly limestone is exposed almost continuously 

in two narrow sinuous bands along the crest and the 

upper western slope of the Magdalena Range from the 

southeast corner of the district to the Ambrosia mine, 

near the north end of the range. Where the overlying 

rocks have been removed these bands broaden into dipslope areas of considerable width. A shorter broken 

band crops out in the group o£ small down£aulted 

blocks in the upper eastern slope due east o£ Kelly; 

and _small exposures, which represent the most productive part o£ the £ormation, are scattered along the 

western slope between the Juanita and Graphic-Waldo 

mines. A large metamo:rphosed block is enclosed in 

Tertiary ( ?) granite at the Hardscrabble mine, and 

one rather large mass is poorly exposed near the east 

side o:f the Granite Mountain area. 

The Kelly limestone £or the most part is a light 

bluish-gray, medium- to coarse-grained, thick-bedded, 

high-calcium limestone with a persistent bed of dense 

argillaceous limestone in its middle part known as the 

"silver pipe" or "indicator," because o£-its close association with ore shoots. The name has also come to 

signify a dense or microgranular texture and has been 

applied to thinner, less persistent beds both above and 

helow the original "silver pipe." The importance o£ 

the Kelly limestone as an ore zone has led to its subdivision into beds that m.ay be readily recognized and 

followed underground, within a; single mine, . though 

some may not persist £rom one mine to another. 

These subdivisions are represented. in figure 1. Although the Kelly limestone ranges £rom 90 to 135 feet 

in thickness, in most places it exceeds 110 feet. The 

unusually reduced thickness o:f 90 feet in the Traylor 

shaft reported by C. M. Glasgow, superintendent o:f 

the Kelly mine in 1916, may be related to a bedding 

:fault. The basal beds, £rom 6 to 16 feet in aggregate 

thickness, are characterized by grains and small pebbles mostly of quartz, with some o£ pink feldspar, 

argillite, and gabbro or diabase. In places they contain sufficient detrital epidote to have a distinct green 

color. They are best exposed along the crest o£ the 

range east and northeast o£ Kelly, where the very 

base, ·which rests on granite and locally on diabase 

dikes is commonly represented by a bed o£ pink 

22 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore 

deposits of New Mexico ; U. S. Geol. Survey Prof. Paper 68, p. 229, 

1910; Am. Joqr. Sci., 4t:P ser., vol. 24, pp. 62-63, 807, 1907. 
CARBONIFEROUS SYSTEM 15 

Traylor shaft 

Kelly mine 

AfterC.M.Giasgow 

~~~Upper crystalline 

1300'E.of 

TipTop tunnel 

~~"Sil~rpip-;' -~~~~--

~~~ Lowercrystalline 

Marbleized 

1:2:i::;:2l Pinto 

SE.of 

TipTop peak 

E.slope 

E.of Kelly 

Upper"silver pipe" =...__/ 

----'--D- ~ 

~= 

~ 

~ 

Lower'silver pipe" =__...... 

Limestone Shaly limestone Arkose and 

pebbly limestone 

Quartzite 

Vertical scale 

50 0 IOOFeet 

FIGURE 1.-Colnmnar sections showing variations in character and thickness of the Kelly limestone. 

felspathic sandstone 3 or 4 feet thick overlain by a 

greenish to dark-gray bed 2 feet thick. Thin beds of 

limestone alternate with sandy or pebbly beds between 

these very basal beds and the overlying continuous 

limestone. At some places, notably the 9,389-foot peak 

in t:Q.e southeastern part of the area and at Oak Spri-ng, 

in the northern part of the range, the basal beds are 

almost pure limestone; but in the Nitt n1ine the basal 

bed is quartzite from 2 to 6 feet thick. In the principal mines of the district the basal beds rest on argillite, but where the basal beds are dark gray and 

fine-grained the contact with argillite is obscure; The 

constituents of the basal beds are not of strictly local 

origin, as large fragments of pink feldspar, characteristic of coarse-grained or porphyritic granite, and 

pebbles of argillite and diabase have been found directly above fine-grained granite, and fragments of 

dark-colored rock may be absent directly above 

argillite, gabbro, and diabase. 

The limestone above the basal beds is mainly bluish 

gray and mediu~-grained and is sometimes called the 

''lower crystalline" limestone. Beds with conspicuous 

crinoid stems and chert lenses are exceptional. In the 

Kelly mine (fig. 1) the typical "lower crystalline" limestone is immediately underlain by a nearly white finegrained bed called the "marbleized lime,'' which contains scattered glistening calcite grains, and this in 

turn by a discolored bed called the "pinto lime." The 

'"lower crystalline" limestone also commonly contains 

in its lower part one or more dense, lithographic lenticular beds, sometimes called "lower silver pipe " The 

"lower crystalline" limestone is over lain by the main 

"sHver 'Pipe," which is of similar dense texture and 

from 4 to 8 feet thick. The lower two-thirds of the 

"silver pipe" is dark gray to nearly black but weathers 

nearly white or buff; the upper third is light gray to 

white on .both fresh and weathered surfaces. Single 

layers range from a few inches to 2 feet in thickness. 

Locally the dense, lithographic texture is not well-developed, but on the whole the "silver pipe" is the most 

reliable- horizon marker in the district, especially underground. The "upper crystalline" limestone, above 

'the "silver pipe," is bluish gray, prevailingly medimnto coarse-grained, and cherty. The coarser-grained 

beds consist .largely of fragments of crinoid stems, and 

the upp.ermost of them are remarkably thin, giving 

weathered outcrops a platy appearance. This platy 

structure has ren:dered the uppermos~ beds_ especially 

permeable and replaceable by gangue and ore minerals. 

Single beds range from an inch to 2 feet in thickness, 

and the chert lenses and nodules are as much as 6 inches 

thick and several feet long. This upper member.also 

contains thin lenticular beds of dense limestone, which 

are sometimes called 'the "upper si:lver pipe.'' 
16 MAGDALENA · MININ·G DISTRICT, NEW MEXICO 

From Tip Top Mountain southward the Kelly limestone has been extensively silicified (see pl. 28, A and 

B, and pp. 53-54). Silicification is most persistent in the 

upper beds but, may also be present just. below the 

'"silver pipe" and in a :few places near the base. At 

a :few places near the southeast corner o:f the district 

practically the entire thickness is silicified. 

The lower half o:f the Kelly limestone mass enclosed 

in Tertiary ( ? ) granite at the I-Iardscrabble mine has 

been bleached, thoroughly recrystallized, and in part 

replaced by garnet and other silicates. It is also replaced by silicates in the vicinity o:f Oak Spring, near 

the east contact o:f the main monzonite mass, and above 

the breast o:f the Linchburg tunnel, south o:f Kelly. 

The one exposure in the Granite Mountain area is 

obscured by :faulting and a thin covering o:f weathered 

debris. TI1e "silver pipe" is exposed in a trench near 

the north end o:f the outcrop, and the silicified basal 

heds are doubtfully recognized along the contact with 

pre-Cambrian schist. 

The Kelly limestone throughout the· area, except the 

layers known locally as "silver pipe," appears to beessentially a calcareous :formation with little or no dolornite present and a very little insoluble residue. Microscopic study o:f the residue :from the "upper crystalline" limestone member :from the Stonewall tunnel 

shows it to consist o:f minute doubly terminated quartz 

crystals; and the residue :from an unreplaced remnant 

from the third level o:f the Kelly mine consists o:f 

ka.olinic material, irregular quartz grains, sericite, and 

pyrite. All these minerals are attributable to mineralizing solutions and are o:f no value in stratigraphic 

correlation. Chemical tests of the "silver pipe" and 

microscopic study o:f its insoluble residue show it to 

be an impure dolomitie limestone containing considerable claylike material. 

AGE AND CORRELATION 

Although :fragments o:f crinoid stems are abundant 

in some beds and small :fragments o:f other fossils are 

numerous in places, identifiable index :fossils in the 

l(elly limestone are disappointingly :few.· One s1nall 

poorly preserved lot, :from the very base o:f the limestone was tentatively regarded by the late Dr. G. H. 

Girty as early Mississippian. Another lot, also poorly 

preserved, :from the top o:f the limestone was insuffieient to show whether the upper part was o:f the same 

age or appreciably younger. The :fossils listed below · 

have been identified by Dr. Girty. 

Lot 6817. Base of Kelly limestone close by fault, southeast 

of Young America mine: 

Stenopora? sp. 

Schizophoria? sp. 

Schuchertella aff. S. chemungensis 

Camarotoechia aff. C. chouteauensis 

Spirifer sp. 

Composita? sp. 

Leptodesma? sp. 

Myalina? sp. 

Naticopsis aff. N. carleyana 

Lot 6818. Top of Kelly limestone, ·crest of main ridge, 1,200 

feet south-southeast of Tip Top Mountain: 

Triplophyllum sp. I Spirifer aff. S. pellaensis 

Cyathaxonia? sp. Spirifer aff. S. missouriensis 

Rhipidomella aff. R. dubia Composita? sp. 

O:f these Dr. Girty says: 

The faunas as represented by these two small lots are markedly unlike, thus suggesting a marked difference in age. These 

faunas contain so little that is identifiable or distinctive that a 

definite correlation cannot be made with known Mississippian 

faunas of the West. Thus, their relative ages in geologic time 

cannot be determined by reference to other faunas that are 

better known. Incidentally, as just implied, neither 'of these 

faunas-is closely related to that of the Lake Val~ey limestone, 

which they might be expected to resemble. Indeed, from our 

present inadequate knowledge, the fauna of the Kelly limestone 

is rather strikingly different from the fauna of the Lake Valley 

limestone, though it is not necessarily of a different geologic age. 

One :fossil plant (lot 7984) was collected :fro;m the 

sinuous band o:f Kelly limestone east o:f the Germany 

mine and was determined by the late Dr. David White 

as Asterroo.alamites scrobioulatus, a Mississippian species. 

MAGDALENA GROUP (PENNSYLVANIAN) 

The nan1e Magdalena group was introduced by 

Gordon 23 in 1907 to represent the Pennsylvanian ro'cks 

in the Magdalena Mountains. 

These rocks, ·which comprise limestones, shales, and 

quartzites, have an average total thicknes8 o:f about 850 

:feet, although the thickness of single 1nembers varies 

considerably, as shown on plate 9. They rest upon the 

Kelly limestone with apparent conformity but are very 

probably separated :from the Kelly by a considerable 

interval o:f late Mississippian time. They are unconformably overlain by the Abo sandstone, o:f Permian 

age,24 throughout much o:f New Mexico, although no 

good exposure o:f an angular unconformity has been 

formd in the Magdalena district. 

The Magdalena group is divided into two :formations, 

the Sandia :formation below and the Madera limestone 

above. 

SANDIA FORMATION 

The Sandia :formation was named by Herrick 25 in 

1900, after the Sandia Mountains, Bernalillo County, 

N. Mex., where it was first studied. The name was 

applied to the shale~, limestones, and sandstones that 

constitute- approximately the lower half o:f the Magda23 Gordon, C. H., Jour. Geology, vol. 15, pp. 8M-816, 1907; op. cit. 

(Prof. Paper 68), p. 231. 

2' Lee, W. 'T., and Girty, G. H., The Manzano group of the Rio Grande 

Valley, N. Mex. : U. S. Geol. ·survey Bull. 389, p. 13, 1909. Lee, W. T., 

General stratigraphic break between Pennsylvanian and Permian in 

western America: Geol. Soc. America Bull., vol. 28, pp. 169-170, 1917; 

Notes on Manzano group: Am. Jour. Sci., 5th ser., vol. 4, p. 325, 1920. 

.. Darton, N. H., "Red Beds" and associated formations in New Mexico: 

u: S. Geol. Survey Bull. 794, pp. 20--28, 1928. 

25 Herrick, C. L., The geology of the white sands of New Mexico, 

Jour. Geology, vol. 8, p. 115, 1900; The Coal Measure forest near Socorro, New Mexico, vol .. 12, pp. 237-251, 1904; Laws of formation of 

New Mexico mountain ranges, Am. Geolo-gist, vol. 33, p. 310, 1904. 

Herrick, C. L., and Bendrat, T. A., Identification of an Ohio coal measures horizon in New Mexico: Am. Geologist, vol. 25, p. 235, 1900. Gordon, C. H., in op. cit. (Prof. Paper 68), pp. 232, 234, 235. 
GEOLOGICAL SUHVEY PROFESSIONAL PAPER ~ PLATE 5 

1 . CLIFF OF SILICIFIED KELLY LIMESTO~E RESTING ON ARGILLITE, WI-IICI-1 IS CUT BY A GRA:'IIITE O[KE. 

The dike. shown beside man in lower left corner, is cut oii abruptly by the limestone. Head of north branch of Patterson Canyon. 

B. WEST SLOPE OF MAGDALENA RANGE, SHOWil\G ITS RELATIONS TO DIPS OF SEDIMENTARY ROCKS. 

Pre-Cambrian granite in foreground overlain by west-dipping Kelly limestone (light-gray). East slope of western ridge consists of Sandia formation; its crest anti wesl slope 

consist of west-dipping Madera limestone. ·Looking north from crest of range N. 80° E. from Kelly. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 6 

A. PHOTOMICROGRAPH OF PRE-CAMBIUAN GRANITE. 

'r'bc rock cou~ist~ essentially of quartz (q) and micropcrthitic orthoclase (or), which arc in large part micrographically inLcrgrown. Green biotite, with magnetite, apatite, 

zircon, allanite, epidote, hastingsite, calcite, and fluorite, is present in certain black areas. Crossed nicols. 

B. PRE-CAMBRIAN GRANITE SHOWING SOMEWHAT ROUNDED 

QUARTZ GRAINS EMBAYED BY INTERSTITIAL MICROPERTHITE. 

Plagioclase with included quartz remnants is shown in lower left corner. 

Crossed nicols. 

C. QUARTZ VEIN CUTTING APLITE, AND IN TURN BEING REPLACED 

BY AN IRREGULAR VEINLET OF BIOTITE AND CALCITE (?). 

Plain light. 
CARBONIFEROUS, SYSTEM 17 

lena group in Socorro and Bernalillo Counties. Although the formation consists largely of shale, several 

members of limestone and quartzite are present. 

The forrpation is exposed along the crest and upper 

west slope of the Magdalena Range in a broad belt 

that extends northward from the south boundary of 

the district to a point half a mile south of the Hardscrabble mine. Faulted outliers of this belt are prominent along the lower west slope between the Kelly and 

the Graphic tunnels, and isolated outcrops are present 

at the east base of Stendel Ridge and at the Vindicator 

mine. A shorter belt on the east slope of the range, 

due east of Kelly, represents the most complete and 

diversified, though not the thickest, section of the 

formation in the district. The Sandia also forms the 

low hills in the eastern part of the G;ranite Mountain 

area. Gordon 26 gives the a pproxim~te thickness as 

600 feet, which accords closely with our mea '3urements 

in the main range; but in the Granite Mountain area, 

oniy 3 miles away, the apparent thickness, which is 

doubtless considerably exaggerated by strike faults·, is 

about 2,300 . feet. The exposures there are poor and 

afford little opportunity to estimate the amount of 

faulting, but different members of the formation are 

clearly much thicker than in the main range. The 

features described below indicate that sedimentation 

during Sandia time took place under near-shore conditions, which favored the thickening and thinning of 

beds within short dist~nces. 

We have divided the formation into six members, 

which, beginning with the oldest, are designa-ted lower 

quartzite, lower limestone, middle qtl.artzite, shale, 

upper limestone, and upper quartzite. The members 

vary considerably in thickness, and the smaller of 

them are lenticular and locally absent. The geologic 

age of the Sandia formation and the overlying Madera 

limestone is discussed on pages 19-20. 

Lower quartzite member.-The lower quartzite is a 

p~rsistent member of the formation in the main range, 

but in the Granite Mountain area it is either -absent 

or has been concealed by strike faults. It consists of 

gray, greenish-gray, and brown quartzite with subordinate interbedded shale and limestone. It is. for the 

most part, about 90 feet thick, but the exposu;e on the 

east slope is apparently 165 feet,. although concealed 

strike faults may reduce that total to 130 feet. Its 

character varies considerably as shown on plate 9. 

In- some outcrops it appears to be almost entirely 

quartzite, as shaly beds are cE>ncealed beneath quartzite 

debris, but where exposures are most continuous considerable shale is i~terbedded with quartzite, and in 

some places thin limestone beds are present. The shale 

and _limestone beds are locally silicified. 

The quartzite beds range in texture from fine to 

coarse-grained and in places become conglomreratic 

28 Gordon, C, H., in op. cit. (Prof, Paper 68), p. 246. 

and contain many pebbles of quartz as much as an inch 

in diameter. Their cementing material is in part calcareous and in part siliceous. In general they have a 

greater ·color variation than th~ quartzite beds in 

higher members of the formation. They are notably 

resistant to erosion and tend to form ridges and dip 

slopes. · · 

The only fossils found in . the quartzite beds of this 

member are a few plant remains (lot 7985). They 

were determined by Dr. David White to be the species 

Lepidodendron clypeatwm, which he described as a 

"Pottsville species and essentially confined to the middle ard upper Pottsville." Invertebrate fossils (lot 

6804) collected ·from a shaly bed near the top of the 

lower quartzite south of Tip Top tunnel were · determined by Dr. Girty and are shown in the list on 

page 20. 

Lower limestone member.-The lower limestone 

member, which persists throughout the extent of the 

formation except where eroded in the southeast part 

of the district, is predgminantly medium-grained 

bluish-gray argillaceous limestone with subordinate 

amounts of shale and quartzite (pl. 9). Typical vari-

~ties of limestone are nodular or lenticularly banded 

with. mottled weathered surfaces, rather coarse grained 

with many fossil fragments, and thin-bedded with thin 

layers and partings of black shale. West of the Ambrosia mine, where the coarser-grained variety has 

been metamorphosed to a white crystallin~ limestone, 

it close,ly resembles· the si~ilarly altered Kelly limestone nearby. The approximate total thickness of this 

member is 65 feet throughout much of the range but 

exceeds 80 feet near the head of Kelly Gulch, south 

of Tip Top Mountain. In l(elly Gulch and on the 

east slope of the range the contact of the lower limestone with the lower quartzite appears unconformable, 

as the contact is undulating; but the bedding is not 

sufficiently distinct to show its true relation to the 

undulating contact. 

The lower part of the limestone especially is also 

characterized by thin, very fossilliferous, shaly beds, 

in which species of Prodructus are prominent. Fossils 

from this member have been identified by Dr. Girty 

and are listed on page 20. 

Middle-quartzite member.-In some places a brown 

to gray, medium- to coarse-grained, lenticular bed of 

quartzite -with a maximum .thickness of about 18 feet 

separates the lower lirpestone member from the shale 

above. It has been mapped, wherever distinct~ as th~ 

middle quartzite member. One lens about 100 feet 

wide in the outcrop an.d 1,000 feet long is exposed 

near Tip Top tunnel. Near its south end it is separated from shale by a thin limestone bed that farther 

south and in the K;elly mine cannot be separated from the lower limestone. Another quartzite 

lens caps the range between two faults near the south-
18 MAGDALENA MINING DISTRICT, NEW MEXICO 

east corner of the district. Its outcrop is approximately 1,000 :feet long and 500 feet wide. There are 

other exposures on the east side o:£ the range and on 

the west slope about 1,000 :feet southwest o:£ the Mistletoe mine and about 1,500 :feet southeast o:£ the Graphic 

tunnel. No co responding quartzite has been found 

in the Granite Mountain area. 

Siwle member.-The shale member, which constitutes more than half o:£ the· Sandia formation, is about 

300 feet thick in the main range, and about 1,100 :feet 

thick in the Granite Mountain are~. It is overlain 

either by the upper limestone or upper quartzite members or, where these. are missing, by the Madera limestone. It is predominantly blue or black and in part 

highly carbonaceous, with several interbedded layers 

o:£ limestone and quartzite. On the east slope o:£ the 

range its upper 100 :feet consists dominantly o:£ thinbedded limestone, whose quantity elsewhere may have 

been underestimated because. o:£ poor exposure. The 

quartzite beds are fine-grained to pebbly and some are 

cross-bedded and ripple-marked. In the Granite 

Mountain area the shale appears to be more siliceous 

than in the main range but has :fewer beds o:£ coarsegrained quartzite and limestone. Sections of the shale 

member are given on plate 9. The bleached metamor-· 

phosed shale near the Sleeper tunnel so closely resembles the bleached pre-Cambrian argillite, against 

which it is faulted, that the two are not readily 

distinguished. 

Fossils collected from the shale member and identified 

by G. H. Girty are listed on page 20. 

Stein and Ringlund 27 report the following plant 

fossils from the shale, which were identified by David 

White: · 

N europteris aldrichi (Lesquereux) ; ferns represented by rachises, species not determinable; Lepiaophyllrum luoidu1n (Lesquereux) ; Sigillaria sp. ; 0 ordaite8 sp. Concerning the age o:£ these, David White 

stated: 28 "The forms represented are characteristic o:£ 

the Pottsville group and leave no doubt as to the age 

of the beds from which they were obtained." · 

V pper limestone member.-The upper limestone 

member, which is bluish-gray and medium-grained, is 

lenticular. It has been mapped in only four placesjust north of Kelly, 1,000 :feet southeast o:£ the Young 

America mine, on the east slope of the main range, 

and in the Granite Mountain area. North of Kelly the 

bed reaches a thickness of 30 :feet and is characterized 

by spherical concentric algal growths as much as 2 

inches in diameter. West of the Paschal shaft it lies 

on shale, ·but to the north and south it forms lenses 

in the upper quartzite. A thin bed o:£ it forms a dip 

slope southeast of the Young .America mille. Fossils 

collected from it and' identified by G. H. Girty are 

21 Stein, Paul, and Ringlund, Soren, Geology and ore deposits of Kelly, 

N. Mex., unpublished thesis, New Mexico School of Mines, 1913. 28 Idem. 

listed on page 20. .A little further south algal limestone similar to that north of Kelly is present in the 

upper quartzite member along the Water Canyon trail 

jnst northeast of the Grand Ledge tunnel. The algal 

limestone appears to have originally contained small 

limestone pebbles, around which the algal growths deYeloped in concretionary fashion. This concretionary 

structure has not been found in other parts of the 

district. 

The upper limestone member on the east slope is 

thin-bedded, and its lower boundary and total thickness must be arbitrarily determined. About 70 feet 

below its top, which is marked by quartzite, it is cut by 

a fault with a dip-slip of 35 feet, which exaggerates its 

thickness by that amount. The thin-bedded limestone 

is under lain by 26 feet of alternating beds o:£ shale and 

limestone, 3 feet of pebbly quartzite, and 100 :feet of 

thin-bedded black limestone that appears to be locally 

equivalent to the upper part of the shale member. The 

entire thickness of 200 :feet or more could be as consjstently mapped in a unit as some o:£ the other members have been, but the drawing of the boundary 70 to 

100 feet below the top maintains a more uniform thickness for the shale member. 

The bed in the Granite Mountain area has an 

apparent thickness of more than 400 :feet. 

Upper qu4rtzite member.-The upper quartzite member, composed of gray quartzite beds with interbedded 

shale and limestone, is also lenticular and has a maximum thickness of about 65 feet in the main range. 

It appears to rest unconformably on the upper limestone in some places and should perhaps be regarded 

as the basal member of the overlying Madera limet.tone; but, because of the numerous thin quartzite beds 

that characterize the Sandia formation, this quartzit~ 

member is also included in it. The quartzite beds are 

thicker near the base and upper part o:£ the member; 

they constitute about 30 feet of the total . thickness of 

the member, each stratum having a thickness of about 

15 feet. 

In the Granite Mountain area the upper quartzite, 

like the lower members, has an abnormal thickness .. It 

is cream-colored to white and well-sorted in contrast 

to the less pure beds in the main range. 

MADERA LIMESTONE 

The Madera limestone is evidently named after the 

town of La Madera, on the east slope of the Sandia 

Mountains. Herrick 29 states that the town "seems to 

be upon a plateau of limestone," but he did not definitely 

name the formation. Keyes 30 was the first to apply 

the name to the "upper part of the great limestone 

formation-the blue to gray beds," in the Sandia Moun29 Herrick, C. L. , The Geology of the San Peflro and Albuquerque dis- . 

tricts: New Mexico Univ. Bull., vol. 1, p. 104, 1899. 

•80 Keyes, C. R., Geology and underground water conditions of the Jornado Del Muerto, N. Mex.: U. S. Geol. Survey Water-Supply Paper 123, 

p. 22, 1905. 
,l 

CARBONIFEROUS SiY.S'l'EM 19 

tains, but he went no further in defining it. Later 

Gordon 31 adopted the name and says that ."overlying 

the Sandia beds in Socorro and Berpali1lo Counties is 

a dark-blue limestone, for the most part in thick beds 

alternating with other thin shaly beds and blue shale." 

The Madera limestone is almost continuously presep.t 

on the upper west slope of the range from the south 

end of the district as far north as the Ambrosia mine. 

Between Kelly and the Nitt mine it is the ·most prominent rock along the lower slope, and farther north it 

is exposed along the east edge of the valley at ·Hardscrabble Camp. It also forms a prominent band along 

the higher foothills of the Granite Mountain area. Exposures near the Nitt mine and at Hardscrabble Camp 

are considerably metamorphosed; but those near the 

Nitt mine are continuous with the ·unaltered rock, and 

some of the less altered beds near Hardscrabble Camp 

are identified by the presence of Fusulina. 

The limestone includes two members that have not 

been separated on the geologic map. Approximately 

the lower 300 feet consists of relatively thin bedded 

bluish-black limestone with some thin beds of bluishgray fissile shale and gray, medium-grained quartzite. 

These lower beds are somewhat similar in general character to those of the Sandia formation and could consistently be included in that formation, but, ·as limestone beds dominate and are continuous upward with 

a much greater thickness of limestone, they have been 

assigned to the Madera limestone ; furthermore, the 

upper quartzite memb~r of the Sandia formation marks 

a convenient horizon for the arbitrary drawing of the · 

formation boundary. The gradational relations of the 

two formations accord with those elsewhere in central 

New Mexico. The dominant, upper member, at least 

300 feet thick, is characterized by bluish-gray fine to 

rather coarse grained, ,massive limestone beds, which 

form cliffs as high as 10 feet. The irregular grain of 

some of its beds is caused by patches and veinlets of 

dolomite. Other beds have streaks and lenticular bands 

of yellow argillaceous material, and a few contain gray 

to black cheTt nodules as much as 8 inches in diameter. 

These cliff-forming beds alternate with subordinate 

thin-bedded, mottled, shaly limestone and a few thin 

lenses of gray shale, gray to brown quartzite, and limestone conglomerate. Prominent lenses of limestone 

conglomerate as much as 500 feet in length and 15 . feet 

in thickness have been · mapped near the base of this 

member at three places north and northeast of Kelly. I 

They contain pebbles of quartzite and Madera limestone and grade ·into thin quartzite beds. They lie 

in distinct unconformity on typical Madera li,mestone 

beds and evidently mark epeated uplift and erosion 

between stages of limestone deposition. In the southernn1ost part of the district the highest beds are mottled 

and shaly and are stained reddish by II!-aterial derived 

31 Gordon, C. H., Notes on the Pennsylvanian formations in the Rio 

Grande Valley, N. Mex.: Jour. Geoiog.y, vol. 15, pp. 805-816, 1907. 

from the over lying Abo sandstone. Where metamorphqsed near the monzonite stock, the Madera li·mestone is either colored green by diopside and epidote 

or is bleached to a white crystalline rock not distinguishable from other metamorphic lirilestone in the 

district. 

The true thickness of the Madera limestone cannot 

be determined within the district, and a composite 

estimate may be. misleading because of faults and the 

unconformable contact with the overlying Abo sandstone. The top of the limestone has been eroded north 

of Kelly. To the south it is marked by a sill of 

latite-porphyry intruded between it and the Abo sandstone, with only a few small scattered patches of the -

sandstone on the underside of the sill. on·e of these 

is at Kelly, where the base of the limestone is ·also 

.exposed, and the cal.culated thickness is about 360 feet 

without allowance for possible minor faults. The base 

and top are both. exposed just south of Chihuahua 

Gulch, but the irregularity of·the dip and the presence 

of faults would render an estimate of thickness still 

more uncertain. Its thickness is apparently between 

200 and 400 feet. The mass on Tip Top Mountain, 

even though its top has been removed, apparently exceeds 600 feet in thickness and may be as much as 

1,000 feet thick, but the apparent thickness there is 

probably exaggerated by concealed strike faults. 

Fossils collected at several places in the Madera 

limestone have been determined by G. H. Girty and are 

listed on page 20. 

AGE OF THE MAGDALENA GROUP 

Fossil plant remains (lot 7985) found in the lower 

quartzite member of the Sandia formation were determined by David White to be the species Lepidodendron clypeatum, which he describes as a "PottsvilJe 

species and essentially confined to the middle and 

upper Pottsville." Plant remains were also found in 

the shale member by Stein and Ringlund 32 which 

David White determined as "N europteris aldricki 

(Lesquereux) ; ferns represented by rachises, species not 

determinable; LejJidophyllru1n lucid1JJm (Lesquereux) ; 

· Sigillaria sp.; Cordaites sp." Also, according to 

White, these fossils are "characteristic of. the Pottsville group and leave no doubt as. to the age of the 

beds from which they were obtained." 

With the exception of the fusulinids the invertebrate 

fossils listed on page 20 afford little basis for separating the Madera and Sandia formations. According to 

G. H. Girty : 

Lot 6800 stands out as something rather distinct from the 

other collections made in the Madera limestone and scarcely 

more distinct from the collections having their source in the 

Sandia formation. Apart from this lot, which colors the composite fauna, the Madeta limestone apparently does not differ . . ' B2 Stein, Paul, and Ringlund, Soren, Geology and ore deposits of Kelly, _ 

N. Mex., unpublished thesis, New Mexicq Schaol of Mines, 1913. 
20 MAGDALENA MINING DISTRICT, NEW MEXICO 

much in its fauna from the Sandia formation. A few species 

in each formation are peculiar to it, so far as our records go, 

but not many of these are suggestive of an older age for the 

Sandia and a younger age for the Madera, though such suggestion is not wholly wanting. I am tentatively regarding 

the Sandia formation as of Pottsville age, but I am tentatively 

regarding the Madera limestone as post-Pottsville, although 

this last needs corroboration. 

Specimens of fusulinids from the upper Madera 

strata were submitted to Mr. John W. Skinner,33 who 

has determined them as an 

"undescribed species of Tritioites which show a close relationship to Tritioites ventrioosus (Meek and Hayden). Their general aspect is suggestive of upper Pennsylvanian age, probably 

upper Wabaunsee." 

Invm·tebrate fossils in the Sandlia formation and Madera 

Umestone 

[Numbers re.fer to different lots collected at places s~own below] -

Sandia formation 

Fossils Lower 

quartzite 

Lower 

limestone Shale 

Upper 

limestone 

Madera 

limestone 

Fusulinid,genusnndetermined .. ___ __ ____ __________ ______ ____ __________ 17,22 

Triplophyllum sp ______________ ---------- ----· ·---- __________ __________ 18 Cyathophyllumsubcacspitosum? --------·- __________ __________ __________ 17 J,ophophyllum pro.fundum. _ __ _ I __ _ __ _ _ __ _ 12 __ __ _ _ _ _ _ _ 15 Campophyllum torquium .. ... _ _ _ _ __ _ __ __ _ ___ __ __ _ _ _ _ ______ _ _ _ _ ____ _ _ _ _ 16, 19. 21 

Campophyllum torquium? ______ ______ ____ 5 ____ ______ ---------· 18 Campophyllum? sp____________ __________ __________ __________ _______ __ 17 Clisiophyllum sp ... __ __ ___ __ _ __ __ ___ _ ____ _ _ _____ _ __ ________ _ _ ____ __ _ __ _ 17 

~:~~~~~~;; ;;~~~==== =======~= ========== ========== ------- ~~- ========== --------18 Aulopora? sp __________ -------- __ __ ______ _ ______ ___ _ ________ _ ___ __ _ ____ 17 

Michelinia euqeneae____ ________ __________ 3 ·--------- ___________________ _ Hydreionocrinusacanthophorus? __________ 6 _____________________________ _ 

Fistulipora sp_ _ _ _ _ __ ___ _ __ ___ _ __ ____ __ __ 7 9 _ -----··- ____ . ______ _ 

Anisotrypa?sp____ ____________ __ ________ 6 ---------· __________ --- ·- ---- Tabulipora aff. T. carbonarin .. _ _ __ ____ _ __ __ ________ 12 ___________ .... ____ __ 

~~~~:trz?~~~~=== ============== ========== 3, ~: ~: ~ -------·9- ========== ========== 

~:~¥~;~~a ~p= =---==== = === ======= = === ====== ~~ :'i~ ~· . --------9- ========= = ==== = ===== Rhombopora sp _____ _ ___ _ __ _ __ _ 1 8 9 __ ... _______ . _. ____ _ Prismopora? sp_______ ______ ___ __ ________ 6 __________ __________ _____ __ Crystodictya sp________________ __________ 6 _______ ___ ______________ _ __ _ Orthotetes sp __________________ . ____ __ _ ___ 6 ____________________________ __ 

Derbya crassa______ ____ _ ___ __ __ _ _ _ _ _ _ __ __ 5 . __ ____ __ _ . _________ . _______ _ 

Derbya crassa?_________________ 1 9 __________ ·--------- Chonetesaff. C. arkansanus ___ _ ________ __ 6 ______ ____ ·------·-- ·-- --- ---- Chonetes mesolobus _ ----- ______ __ _________ . ________ 11 • ___ __ _ ___ 19 Chonetes sp__ ______________ ____ 1 4 ________ __ _________ _ ________ __ 

Productus (Linoproduct?ts) 

p~~"d~i:iU8!11i: P.'FnitaiU8==== === ___ ___ __ 5

' li, 

7

' ~ -~ ~~~~-~~ _ ========== ________ ~ Productus coloradoensis________ 1 __________ ---~----·-- 14 18,20 Productus coloradoensis? __ __ __ _ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ __ _ __ _ _ _ _ __ _ _ __ __ _ _ __ _ _ 17 

Productus nolani? _ ------------ 1 __________ 9 ___ ________________ _ Pro1uctus semistriatus? __ ______ _ _______ __ 5 ___________________ __ ________ _ 

Productus semireticulatus _______ . _ _ _ _ _ _ __ 8 14 19 Productus semireticulatus? _ __ _ _ __ __ _ ___ __ s· __ ___ _____________ ___________ _ Productusaff. P.gallatinensis .. __________ 3. --·-------- __________ ---- ·-- --- Productusaff. P. morrowensis .. __________ 3 ---- ·----- ___________________ _ Productus sp_ ___ ____ ____ _ _ ____ 1 3, 4, 5 Productus n. sp _______ ___________ ________ _________ _ 11 19 

12 ---------- ------ ---- Productus n. sp.? _____________________ __ 13 ---------- 1.5 Prodw;tus (Juresania) nebms- . kenSIS .. _ --------------- ____ __ ------- __ Productus (Juresania) nebra.!- kensis var _____________________ .. _____ _ 

Productus (Juresania) nebras- kensis? _________________ . __ __ ______ ___ _ 11 ---------- -- -- ,_ __ __ Productus (Pustula) aff. P . 

P~d~~c~~(~ii siuia) n:si>_-_-_·_·: ~=: ~ == == ~= . _ ---- ~· ~== =====~= ====~==~== --------i9 Productus (Avoni't) sp. ___ __ __ _ ___ __ _ ____ 4 ___________ __ ____________ ... __ Marginiferaingrata_ ___ ________ __________ __________ 11 ___________________ _ 

Marginifera splendens _________ ______________________________ --------· · 17 Marginifera murica/a __________ . _________ __________ ·--- . ___ __ . -----·--- 17 

Marginifera mmicata? _____________ __ ___ ---------- 12.13 17 

Margini[era n. sp. aff. M. 

splende.ns. ·----------------- __________ _________ _ 12,13 _________ _ 15 Marginifera? sp_______________ __________ 3 __________________________ __ __ 

~hrf~~c7ria f1i:S. tex~na_·_==== =========~ --------6- ::======== ~~===:==== ---- ~~~~~ 

~~l~i}:~ ~~~:~~~:?:: ~==:====~= :===~==== = =========~· 11, 12,1~ -- ----- ~~ ======= =:: Spirifer aff. S. goreL__ ________ __________ 6 __________ _____ ____ _ 

Spirifer opimus var. occidm· talis _______ ___ ______________ _ ___ ___ __ _ . 5, 6 12,13 15, 16 

33 Personal communication. 

lnvm·tebrate fossils in the Sandia formation and Made'ra 

limestone-Continued 

Fossils Lower 

quartzite 

Sandia formation 

Lower 

limestone Shale 

Upper 

limestone 

Madera 

limestone 

-------------·- -----------------

Spinier rockymontan·u8 var.:___ 1 4, 7 9 ---------- 20 Spirifer rockymontanus _______ • ____ _____ _ 3 11 _______________ ___ _ _ Spirifn triplicatus ____________ • __ ________ __________ __________ __________ 19.21 

~~l~~;~. ~!~~~~~~~~~~~~ : ::=: ::~ ~- ~ === = =:====: = = ~~~~~~~ ~~ ~ :::::::::: = ::: ~ === ~~ Spirifer ~P ---- _. _________ :__ ___ . _ _ ___ ___ _ _ _ _______ _ _ _ ___ _ ____ 18 

Punctisptrifer aff. P. trans- versus . . --- ------------------ 1 3 ----~---- __________ ---------- Punctispirifer kP-ntuckyensis .. .. ___ . . __ ___ 6 __________ ___________ . ____ __ __ Punctispirifer nt uckyen.~is? ___ _ _ _ _ __ _ __ _ __ __ _ _ _ _ _ _ 9 ____ __ ___ _________ __ Punctispirifer ~P -- ------------- __________ __________ ________ __ _______ __ _ 17 Squamularia perplexa__________ _____ _____ __________ _____ ____ _ __________ l!i, 17,19 

Composita subtilifa______ _____ __ 1 3,4, 5, 6 12,1::1 ·--------- {15• ~~i Composita sp ____ __ ______ ______ __________ fl __ ____________ ______ __ ______ __ 

Cleiothyridina pecosi. _________ • 1 4, 6 12,13 _________ _ Hustedia aff. H. miseri_________ ___ _______ 3 ____ ________ ____ ___ _______ ___ __ 

Hustedia mormoni_____________ _________ _ 3 ___________ _________ ----------

Hustedia n. sp. ? --------------- ---------· 6 ______ ______________ ---·------ Edmondia? sp____ _____________ l _____ ______ ___________________ __ ______ __ 

Leda aff. L. mukana_ __ ________ ____ ______ 3 ___ ____________ ____ _ -- --------

fJ;~~~~~~~~JM~is? Amculopecten sp_______________ :========= :===~==== 2 3 ~ ~===~===== ________ __ __________ ===~== ===~ ===~= ----------===== Aviculcpecten n. sp ___ __ _______ ·--------- 3 _________________ ___ ----------

Deltopecten occidentalis? --·----- 1 ________________ ___ _ ---------- -------- -- Streblo-pteria sp .. _______________ . _ _ _ _ _ _ _ __ 5 _________ _____ ___ _______ ------

Lima SP-------··--------------- ___ _______ __________ 11 __________ ---------- Lima? sp ___ _______ ------------- . _ ____ ___ _ 6 ______ ______________ ________ __ Astartella sp_______ _____ ______ __ _____ __ ___ 3 _____ __ _____ ________ ----------

Pleurophorus? sp______________ ________ __ _ 6 12 _____ ___ __ ----,------ Pleurotomaria sp. ------------- ____ _____ 3 ____ __________________ -~- ___ _ Pleurotomaria? sp_____________ _ _______ _ 5 ___ ____ ___ __ ____ _________ ____ _ Bucanopsis sp_______ ___ _ _ _ __ ___ _ _ ____ __ _ 3 ______ __ _________ ____________ _ Pate.llot:tittm sp ... ______________ .. ____ _ _ _ _ _ _ ________ 12 _____ ____ _ _______ __ _ 

Euphemites carbonarius. ____ ___________________ ___ ·--------- __ __ ____ __ 15 

~~f~:sTo~~ ~~~?zfr:t;Ie~~~~ ~~===~ ·==~ ====== ~ :=:======= =~=== ===== == == == == := 

IJ.J:l!c~C:~~t~";~ Naticopsis? sp_~-e~~~e_n_~~~ _______ _________ = :~ == = : 

__=== ________ =~: = == :: :=: =: = 5 == _

~==:::: __________ ==: ===: ____== __= ::: 

__________ i~ __ Meekospira? sp__ _ _ _ _ _________ _ _____ _____ 3 ___________________________ __ _ 

Platyceras occidentale __________ -"-------- ________ __ 12 ____ _____ _____ ___ __ _ Platyceras occidentale?____ _____ __________ 6 _______ _____________________ . _ Eotrochus sp_____ _ _ _ ____ __ _ _ _ _ _ _ __ _ _ _ __ _ _ _ __ _ _ __ _ _ ____ __ __ __ ___ _ ____ __ 19 Griffith ides sp ·--__ ~ ____________ . _____ __ __ 3 ________________ __ ___________ _ 

1. Lot 680~l, from a shaly bed near top of the lower quartzite 

member south of Tip Top tunnel. 

2. Lot 6805, about 100 feet east of Woodland mine. 

3. Lots 6904, 6906, and 6907, east of Mistletoe tunnel on west 

side of range. 

4. Lot 6811, about 1,000 feet northeast of Cimarron tunnel. 

5. Lot 6825, about 700 feet northeast of Cimarron tunnel. 

6. Lots 6828 and 6829, about 700 to 1,000 feet south of Tip 

Top tunnel on west side of gulch. 

7. Lot 6810, on spur with saddle on east slope of range east 

of Kelly. 

8. Lot 680'T, near north end of lower limestone exposure on east slope of range due east of Kelly. 

9. Lot 6809, just east of Paschal shaft. 

10. Lot 6816, from thin-bedded limestone just below quartzite 

bed at first bend in road southwest of fork in Tip Top 

road. 

11. Lot 6808, west of Young .America mine. 

12. Lots 6820 and 6823, west and north of Tri-Bullion mill. 

13. Lot 682'i', 500 to 800 feet southwest of Tip Top tunnel. 

14. Lot 680B, 1,000 feet southeast of Young America mine. 

15. Lot 6822, Basal shaly bed in gulch 700 feet west of Paschal 

shaft. 

16. Lot 6824, 500 feet north of Cimarron tunnel. 

17. Lot 6800, 800 to 1,000 feet northwest of Tri-Bullion mill. 

18. Lot 6802, 600 to 700 feet west of Tri-Bullion milL 

19. Lot 6821, 700 feet west-northwest of Tri-Bullion mill. 

20. Lots 6812 and 6815, west-southwest of Grand Ledge tunnel. 

21. Lot 6826, . 800 feet- west of Tip Top tunnel. 

22. Lot 6905, about 100 feet north of Mistletoe tunnel. 

ABO SANDSTONE (PERMIAN) 

The youngest Paleozoic formation in the Magdalena 

djstrict is the Abo sandstone, the lowest member of the 
ABO SAND<SfrONE (PERM!AN) 21 

Manzano group., of Permian age.34 It unconformably 

overlies the Madera limestone. Although the Abo and 

1\'Iid.era formations are in contact at only a few places, 

because of faults and of. the intervening sili ·of porphyritic latite, there i~ apparently little angular discordance between them. The unconformable relation 

if:: most strongly suggested near the south boundary of 

the district, where the Abo sandstone overlies a beveled 

surface of the Madera limestone that slopes 24° W., 

whereas the Madera strata dip 17° W. The unconformity has been recognized in other parts of the 

State. 35 Darton 36 states that "in most places the Abo 

formation appears to lie unconformably on the lYiagdalena group, but the nature, duration, and extent of the 

hiatus are not known." The Abo, in turn, is unconformably overlain by Tertiary volcanic rocks. 

Section of Abo sandstone south of the old aerial tramway 

· near Patterson Canyon---Continued 

Pebbly sandstone containing fragments of the light and 

dark-red members up to 4 inches- in diameter; weathers 

to irregular surface __________________________________ _ 

Sandstone, red, coarse-grained, micaceous, with calcite 

veinlets ___________________________ ~ _____ .:_ ____________ _ 

Sandstone, red to brown, wea_thers to thin irregular beds ; 

l!'eet 

6 

2 

grades into a red arenaceous shale ___________________ :__ 15 

72 

The age of the Abo sandstone was formerly believed 

to be Pennsylvanian,37 although Herrick 38 originally 

believed the lower member of the Manzano group to be 

Permian and the upper members younger. Its age is 

now established as Permian. 39 

The following fossils from. the Abo sandstone have 

been identified by Dr. Girty : The Abo sandstone, which is exposed at intervals 

from Kelly southward, consi~ts of dark-red to locally Lot 6801. On trail just south of district close to basal 

gray fine- to coarse-grained shaly sandstone beds, contact: 

mostly less than a foot thick, which alternate with Fusulina secalica. 

dark-brown to red or locally green sandy shales. The Derbya aff. D. multistriata. 

red color is bleached to light gray along quartz veins · Marginifera splendens. 

and to gray or greenish gray in occasional baked inclu- , Pustula symmetrica? 

sions in the adjoining sill of potphy!'itic latite. In Composita subtilita. 

some places the sandstone grades into sandy shale Of these, Dr. Girty makeS: the following comme~t: 

along the bedding. Cross bedding, ripple marks, and Qualified by the fact that this lot contains only 5 species, this 

mud cracks are common. Locally the basal bed is a fauna marks a distinct departure from the Madera collections, 

limestone conglomerate, the limestone pebbles of which though perhaps no more of a departure than lot 6800, which 

were apparently derived from the underlying Madera is proper to the Madera. Its stratigraphic position together 

limestone. However, near the south end of the district with certain suggestions contained in the fauna itself seem to 

make it advisable to class the horizon of lot 6801 as basal 

the basal bed is arkose with prominent pink feldspar Red Beds. 

gra1ns. 

- The maximum thickness of the Abo sandstone within 

the district is about 175 feet, but most of the sections 

studied are less than 100 feet thick. The thickest is at 

the 7,800-foot hill just south of Mistletoe Gulch. One 

of the best exposures, just south of the old aerial 

tramway near Patterson Canyon, is represented below; 

however, it is in fault contact with porphyritic latite 

and the basal beds are not exposed. 

Section of Abo sandstone south of the old aerial tramway 

near Patterson Oanyon 

Feet 

Sandstone, pale red; overlain unconformably by andesite__ 25 

Sandstone, red, fine-grained, with fragments of light-green and gray sandstone___________________________________ 6 

Sandstone, red, ferruginous, micaceous ; irregular bedding 

planes 2 to 4 feet apart, partly weathered to thinly bedded 

material. Cross bedding on large and small scale______ 18 

u Herrick, C. L., Geology of the white sands of .New Mexico: · Jour. 

Geology, vol. 8, pp. 112-128, 1900; also New Mexico Univ. Bull., vol. 2, 

pp. 1-17, 1900. Lee, W. T., and Girty, G. H, The Manzano group of the 

Rio Grande Valley: U. S. Geol. Survey Bull. 389, pp. 10-13, 1909. 311 Herrick, C. -L., .A coal-measure forest near Socorro, New Mexico : 

Jour. Geology, vol. 12, p. 244, 1904; Lee, W. T., Note on the Red Beds 

of the Rio Grande region in central New Mexico: Jour. Geology, vol. 15, 

pp. 52-58, 1907 ; Lee, W. T., and Girty, G. H., The Manzano group of 

the Rio Grande Valley, ~ew Mexico: U. S. Geol. Survey Bull. 389, pp. 

12-13, and 39, 1909. 

ll6 Darton, N. H., "Red Beds" and associated ·rormations in New Mexico: U. S. Geol. Survey Bull. 794, p. 20, 1928. 

A fossil plant horizon was found in the saddle just 

north of the old aerial tramway. Probably the same 

stratigraphic horizon is exposed to the northwest in 

the southeast corner of sec. 1, T. 3 S., R. 4 W. 

Specimens in lot 7983 were determined by David White 

as species of "W alchia, intermediate between W alchia 

pinifor-rnis and W alohia hypnoides''; another species 

of "W alchia that is probably undescribed," and "a 

small fragment that is possib.ly referable to W alchia 

pimiformis." Darton. 40 reports that G. E. Anderson 

"collected a slab of red sandstone 41 that showed a fine 

impression of a plant, on which David White has 

furnished the following report : 

The fossil plant on the slab of red sandstone from the Abo 

formation near Kelly, N. Mex., was considerably worn and 

slightly macerated before fossilization, and some of the criteria 

essential for its absolute paleontologic determination are lacking. However, it appears to be a representative of the Callipteris 

a1 Lee, W. T., and Girty, G. H., op. cit., pp. 12, 16-17. 88 Herrick, C. L., op cit. (Jour Geology), pp 112-128 and (New Mexico 

Univ. BulL) pp. 1-17. 39 Lee, W. T., General stratigraphic break between Pennsylvanian and 

Permian in western America: Geol. Soc. America Bull., voL 28, pp. 169-

170, 1917; Notes on Manzano group: .Am. Jour. Sci., 5th ser., vol. 4, 

p. 325, 1920. Darton, N. H., "Red Beds" and associated formations in 

New Mexico : U. S. Geol. Survey Bull. 794, pp. 16-28, 1928. 

4Q Darton, N H., op. cit., p. 137. 41 Lost in the New Mexico School of Mines fire in 1928. 
22 MAGDALENA MINING DISTRICT, NEW MEXICO 

group, of distinctly Permian type, and probably belongs to the 

genus Glenopteris, described from the Wellington shale, which · 

in Kansas is considerably above the base of the Permian. 

'!'hough the evidence is not conclusive, because the identification 

is somewhat uncertain, it is probable that this is a Permian 

plant. 

TERTIARY (1) SEDIMENTARY ROCKS 

Along the west edge of the Granite Mountain area 

are a few small exposures of gray fine- to nlediumgrained sandstone of probable Tertiary age. Similar 

sandstone, however, has been found, by reconnaissance, 

to be rather extensively distributed in the Bear ~fountains to the west and north of the area. There are 

n1any inclusions of it, ranging from an inch to tens of 

feet in diameter, in the adjoining Tertiary ( ~) granite. 

The prevailing gray color is locally modified by buff 

and brown banding, especially next to joints. The 

constituent grains are well-rounded to subangular and 

consist almost entirely of quartz. They are poorly 

cemented in the unaltered rock, but the inclusions in 

the granite and the sandstone near the contact have been 

hardened an'd in part converted into quartzite. 

In general the sandstone is much fractured so that 

its bedd.ing and structure are obscured, but an exposure in the arroyo about 3,200 feet east and 600 feet 

south of the northwest corner of sec. 14, T. 2 S., R. 4 

vV., shows it to have at least locally a strike of N. 7o 

,V. and a dip of 62° W. This steep dip, which is much 

greater than the general dip of the underlying volcanic 

rocks, is undoubtedly due to local drag produced by 

faulting, which may also account for the excessive 

fracturing of the sandstone. 

The age of the sandstone cannot be closely defined. 

It is older than the granite, as shown by the numerous 

inclusions in the granite, but nowhere within the disti~ict is it in contact with the volcanic rocks. Just 

northwest of the district, however, it is clearly overlain 

by banded rhyolite, and as it dips westward it apparently overlies the older volcanic rocks, which also dip 

westward. Winchester 42 described a formation in the 

Alamosa Creek Valley about 12 miles northwest of the 

district as "consisting of a series of tuffs, rhyolites, sandstones, and conglomerates, which is probably of late 

Tertiary age, although no fossils were found that lend 

evidence for this assumption." This formation he 

named the Datil formation, as it is the most prominent 

component of the Datil Mountains, in the southern 

part of the region that he studied. It seems probable 

that the sandstone in the northwest corner of the Magdalena district is to be correlated with the sedimentary 

members of the Datil formation, as it is similarly associated with volcanic formations and is found in hills 

that are the southern extension of· the Bear Mountains 

o:f the Alamosa district. 

4.2 Winchester, D. E., Geology of Alamosa Creek Valley, Socorro 

County, N. Mex. : U. S. Geol. Survey Bull. 716, p. 4, 1921. 

QUATERNARY SYSTEM 

The Quaternary formations of the district include 

landslides, alluviu.m, and talus. The oldest of them 

may be of Pleistocene or even Pliocene age, but there 

is no basis for distinguishing between Pleistocene and 

Hecent deposits. 

LANDSLIDES 

The landslides, reduced to mere remnants by erosion, 

are mainly confined to the southern part of the district, 

where they cap a few spurs and upper slopes of sedimentary and volcanic rocks. The most pronounced 

areas are immediately north and south of the Young 

America mine. One just south of Patterson Canyon 

is almost surrounded by a high bench of alluvium. 

The landslides consist of Carboniferous debris. The 

one south of Patterson Canyon is made up essentially 

of large blocks of Madera limestone and Abo sandbtone, but those :farther up the slope to the east contain also blocks from the Sandia and Kelly formations. 

Some boulders are as much as 100 feet long and 25 feet 

thick, and some may be even larger. A prospect shaft 

30 feet deep has been sunk in a block of cherty Kelly 

limestone, and about 4,000 feet east of South Camp a 

1,200-foot tunnel has been driven in landslide material. 

A small amount of ore was mined by F. A. Gordon 

from a block · in the slide south of Patterson Canyon. 

Scars indicating the breaking away of a landslide 

are still recognizable near the crest of the range, 

especially in the Kelly limesto:J!e in the vicinity of the 

Young America and Woodland mines. The landslides 

probably took place during a period when relief was 

greater than at present and undercutting and oversteepening were prevalent. It is quite probable that 

the erosion of downfaulted shale beds west of those 

mjnes permitted rocks to the east of the main fault zone 

to break away and to slide down the dips of shale layers 

at the base and top of the Kelly limestone. Subsequent 

erosion has deepened the transverse gulches, leaving 

landslide debris as caps to the spurs, but has not reproduced conditions favorable to the recurrence of 

appreciable landslides. 

ALLUVIUM 

Alluvium flanks the western slope of the range and 

completely surrounds the Granite Mountain area. 

Within the district it is represented by fans that 

spread over a gentle rock slope and grade into valley 

fill. The covering of the rock slope ranges in thickness from a veneer, as is well shown just west of 

Kelly and south of Stendel Ridge, to 125 :feet or more. 

It consists of angular to rounded pebbles, cobbles, and 

small bould~rs that have accumulated intermittently 

over a considerable time. The older accumulations, . 

which range in altitude from 7,225 to 7,850 feet on 

the west slope of the range and from 7,900 to 8,275 

feet on the east slope, have been considerably eroded 
TER'l'IARY ( ? ) EFFUSIVE IGNEOUS ROCKS 23 

and in places only remnants of them are left; but 

where they have been protected from .erosion they 

grade imperceptibly into the more recent accumulations. An attempt to show them separately on the 

map has therefore been abandoned. 

TALUS 

The only areas of talus shown on the geologic map 

are those on the east slope of Granite Mountain, where 

the talus is sufficient to conceal considerable bedrock 

and thereby seriously interferes with the interpretation 

of local structural features. The talus, where not in 

contact with exposed bedrock, grades into alluvium, 

and its boundaries have therefore been drawn rather 

arbitrarily. 

TERTIARY (1) EFFUSIVE IGNEOUS ROCKS 

GENERAL STATEMENT 

The effusive rocks of the district-latites, andesites, 

and rhyolites-are found in the foothills and lower 

slopes on the west side of the main range of the b-elt 

of Paleozoic sedimentary formations. In the Granite 

Mountain area they predominate, but here also they are 

found west of the sedimentary formations. , 

N. 

The different formations represented on the geologic 

map can in general be distinguished by their characteristic colors or textures and have been named ac~ordingly. They trend northward and have a general dip 

of 25°-30° W., but locally they dip as much as 50° W. 

or, as shown by the pink rhyolite, as little as 10° W. 

Figure 2 shows the sequence and relative ages of 

the formations in each part of the district. It also 

expresses the restricted distribution and probable interfingering and overlapping of the lower formations, 

which were derived from at least two centers of eruption probably beyond the limits of the area studied. 

It is only by means of the banded rhyolite, which is 

present throughout the district, that the sequences in 

different parts of the district have been correlated. 

The earliest eruptions evidently took place in the 

northern part of the region. The large volume of pyroclastic material shows that the eruptions were chiefly 

violent, but the mode of extrusion, whether by fissure 

or by central eruption, is nowhere shown within the 

district. 

The volcanic rocks, on the. basis of local geologic 

structure, are divisible into an earlier and a later group, 

whos~ eruptions were separated by a period of faults. GRANITE MOUNTAIN AREA STENDEL RIDGE AND WEST SOUTH AN 0 WEST OF KELLY 

........ 

b 

>-

0:: 

<( 

~ a:: 

w 

1-

( 

Rhyolite porp 

(Sill and dikes) 

I$~$~~ Upper andesite 

(Ficiws) 

~~~$::1..-::_0N~;O~I''O-;~.f/TY(.") 

Red rhyolite 

(Flows) 

/ 

Red andesite 

(Flows and tuffs) 

Banded rhyolite 

Abo sandstone 

(Permian) 

* Banded rlyol/te extensive west of' area mapped, 

thickness unknown 

* * Continues west or area, thickness unknown 

Vertical scale 

50EO~CEOC====50EO~~l~,Oc00====~~2pooFEET 

FIGURE 2.-Sequence or effusive igneous rocks and associated rhyolite sills in the Magdalena district. 
24 MAGDALENA :M1N1NG DISfl'RIC'r, NEW :M:ffi:XlCO 

ing, tilting, and erosion, but the earlier group may be 

divided into two subgroups separated by a stage of 

erosion and sedimentation. Rocks of the earlier group 

include the latites, lower andesites·, and the banded 

and red rhyolites. The lower members of this group 

ov~rl~pped southward on an irregular erosion surface 

of somewhat deformed Carboniferous rocks, and south 

of Kelly they interfinger with or are overlain by the 

/ purple andesite, which was evidently erupted from a 

different center. In the Granite Mountain area the 

eruption of upper latite was separated from that of 

banded rhyolite by a substage of erosion and sedimentation represented by Tertiary ( ~) sandstone which is 

well-exposed west of Granite Mountain beyond the 

area represented on plate ·2. Winchester 4 3 describes 

interbedded sedimentary and volcanic rocks in the valley of Alamosa Creek to the northwest, where the 

sedimentary rock is more prominent and may represent 

a greater interruption to the volcanic sequence than it 

does in the Magdalena district. In the southernmost 

part of the district, however, the banded rhyolite and 

the underlying andesites are in apparent conformity. 

The members of the earlier group, both below and 

above ~he sandstone horizon, dip from 30° to 50° westward and appear to be conformable throughout, but any 

angular djscordance in dip that might be correlated 

with this substage is obscured by a large sill of rhyolite porphyry that was introduced along the contact 

between the upper latite and the overlying rocks. 

South of Kelly the rocks of the earlier group are cut 

by a sill of latite porphyry. 

Men1bers of the later group include white felsite tuffs 

in the Granite Mountain area and the upper andesite 

and pink rhyolite south and west of Kelly. These 

members dip westward- at very low angles and overlie 

members of the older group unconformably. The unconformity in the Granite Mountain area is distinct. 

In the southwest part of the district the pink rhyolite 

overlaps the upper andesite eastward and northward 

onto the more steeply dipping red andesite and red 

rhyolite, but the relation between the upper andesite 

and the older volcanic rocks is obscure. 

The later group also is cut by sill-l~ke masses and 

dikes of rhyolite porphyry identical with that in the 

large sill within the earlier group. This porphyry, 

therefore, is ,clearly the latest member of the volcanic 

series, but it may conveniently be included in the later 

group, as it was intruded before the major period of 

disturbance that separated the volcanic period as a 

whole from the later periods during which stocks of 

granite and monzonite were intruded and ore deposits 

were formed. · 

The volcanic rocks of the main Magdalena Range are 

limited to the lower western slope. They gradually 

43 Winchester, D. E., Geolog.y of Alamosa Creek Valley, Socorro 

County, N. Mex. : U. S. Geol. Survey Bull. 716, pp. 4-5 and 9-10, 1921. 

extend up the slope as they are followed southward, 

1·eaching the crest a little beyond the south boundary of 

the district;. and from there they cover the entire range 

for a distance of 20 miles.44 This distribution, together with the thickness and dips of the volcanic rocks 

within the district, leaves no doubt that the ·volcanic 

rocks at least of the first stage once covered the entire 

district. 

The volcanic rocks are considerably altered, and the 

original character in some has been destroyed. Insofar as possible, however, the original minerals are 

noted. Because of the altered character of the rocks 

the classification of each must necessarily be based on a 

microscopic study. The alteration products are included in the rock descriptions, but the interpretation 

and significance of the alterations are discussed in the 

section on rock alteration. . 

LOWER LATITE TUFF · 

The lower latite, the oldest and least extensive of the 

Tertiary ( ~) volcanic rocks, marks the beginning of 

volcanism within the district. It .is found only east 

of Granite Mountain in a narrow irregular band of 

northerly trend that covers about 20 acres; It rests 

unconformably on the Madera limestone, with the exception of its southernmost outcrop, which overlies 

shale of the Sandia formation. Its exposures are so 

poor that nowhere can its strike and dip or thickness 

be accurately determined, but as the overlying andesite 

dips about 30° w., the dip of the latite is inferred to 

be similar; and its thickness is estimated to be about 

500 feet. 

The rock is greenish gray and appears minutely 

porphyritic because of the abundant 'grains of white 

and pale-pink feldspar, which average about 1 millimeter in diameter, and the green specks of epidote. 

No dark mineral can be recognized. Crystal fragnlents, as shown in thin section, are estimated to constitute from 50 to 70 percent of the rock. Their diameters attain · a maximum of 2 millimeters but are 

n10re commonly 1 millimeter or less. They have the 

random distribution characteristic of a crystal tuff 

and are embedded in a matrix too fine grained to be 

positively identified. Most of the fragments are plagioclase and orthoclase, but a few are felsite. Quartz 

forms small irregular grains and scattered bunches that 

are probably secondary. Typical grains of magnetite, 

apatite, and zircon are also present. Ferromagnesian 

n1inerals are now represented by chlorite full of finegrained magnetite. 

Other secondary products are epidote and calcite, 

and in one section sericite. Orthoclase, which appears 

as typical microperthite, and plagioclase are partly 

"Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore deposits of New Mexico: U. S. Geol. Survey Prof .. Paper 68, p. 248, 1910. 

Darton, N. H., "Red beds" and associated formations in New Mexico : 

U. S. Geol. Survey Bull. 794, p. 136, 1928; Geologic map of New Mexico; 

U. S. Geol. Survey, 1928. · 
GEOLOGI CAL S URVE Y PHOFESSIONAL PAPER 200 PLATE 

A . LAMELLAR STRUCTURE IN WEATHERED LATITE TUFF ON THE EAST SLOPE OF GRANITE MOUNTAIN. 

The he tin ~ dips ahout 10° W., whe rea s joints dip steeply to the ea st. La Jenze Creek is seen on t.he ri~ht. N ipple Mountain, Lo the north, lies outside t.lte area mapped . 

B. PHOTOMICROGRAPH OF PRE-CAMBRIAN GRANITE. SHOWING 

PLAGIOCLASE - AND OTHER SALIC MINERALS PARTLY HEPLACED BY GREEN BIOTITE AND HASTINGSITE (DARK 

AREAS). 

Crossed nicols. 

C. RAMIFYING VEINLETS OF BIOTITE PARTLY ALTERED TO 

CHLORITE (DARK AREAS) AND CALCITE REPLACING FELDSPAR 

IN PRE-CAMBRIAN GRANITE. 

Minute veinlets are especially common along cleavage cracks in :feldspar. Plain li ght. 

OEOLOOlCAL S R EY 

System rles Group 

Quaternary. 

Tertiary (7). 

Permian. Monzano. 

Ponosylvanian. 

Mississippian. 

Pre-Cambrian. 

Formation 

Datil ( ?). 

Abo saodstooo. 

1 tlcra lim tono. 

pper quartzite. 

Upper limestone. 

Section or rocb 

.. ... 

rifiti,·f~i# 1:·:-:-:·:·:-:-:·:-::.:.:.:.:: .. :,:.;;:;:,?~·-·. : .. ~·.':.,;;; 

1:-:7-.::::?.>?:7(:~?::;·:·:: ·:-::::: ·.-:::-: .. :::·:·::.:: ··:~:::.;._: -"'T- =-=r 

·.-!' 

=- ~~ l 

.- l 

r I T 

[::;:.::>:~· :· . .~-:': -:::;..;;:.:·.>? ... '' ::J 

lf ~- . .-;::;.,·. 

~- :~ c:-r-j 

Thickness 

(feet) 

PROFESSIONAL PAPER 200 PLATE 8 

Character or rock 

G-IOO+ AJiuvlum, talus, and landslide material; cbJefly coarse and angular. 

o-IOO± 

0-175± 

GOO± 

upper latite and overlain by banded rh yolite. Found only in ranite Mountain arna . 

biofly red sandston with some interbeddC<l red sbal sandstone and red sandy shale. 

Massive limestone, rather thin bedded in low r part, with some interbedded shal and quartz· ite, especially near base; also contain a few lenses of limestone conglomerato. 

Quartzite with interbedded shale and limestone. 

Limestone. 

bale.IIII.II II·~··20± ·- al lt terbed ed imesto ~ and quartzite. 

---- ~ ---==-- --=----::-.:...~A -~- ------------ - 0 I Qu rtrfto. ------

66± Lim t ne with int rb dded shal nd quarttit . 

Quartdt with lnterbcddod sh lo. 

-\ 

Kelly lime tone. 1:10± Gray crystalliuo limestone wltb "sllvor pipe" nnar middle; congl morato at baso in places. 

Argillite, schist, felalte, gabbro, and granite, cut by diabase dikes. 

GENERALIZED COLUMNAR SECTION OF SEDIMENTARY ROCKS IN MAGDALENA RANGE. 200889--42 (lo"aco p. 24) 
OF:Of"'OOJC.A TJ BUR VI'.lT 

I 

GULCH J UST NORTHWEST 

OF PASCHAL SHAFT 

/ 

lLJ 

:z 

0 

1-

r.n 

lLJ 

~< 

-' 

<( 

a:: 

lLJ 

Cl 

<( 

~ 

/ 

~uartzr te wrth t~l rbedded 

shale a nd limesto11e 

Dark-blue massive limestone 

Conceale d 

"'M·gral ned blue-black h . · (Fvau lirt4) 

Conceal ed (shale!) 

Blue-blat k fossiliferous Is. 

Conceal ed tshale?) 

Blue-blac k fossiliferous limestone 

Conceale d (shale?) 

Blue-blac k fossiliferous Is. 

Conceale d (shale?) 

·BJue-bla ck fossiliferous Is. 

· Shale 

. Blue-blac k thin Is. 

Shale 

Dark lim estone Blue tlssl le ~hale 

Thin-bedd 

.. Biue-blac 

~~Uil~ fo~ 

ed fossiliferous Is. 

k fissile shale 

iliferous shale 

Blue-blac k limestone 

""' Conceale d (shale?)........._ 

-lf'"i!,\1'{· ·.£· :),: Quartzite """ ........... 

3 

K ELLY GULCH 

J UST NORTH OF 

T IP TOP TUNNEL 

~=r:::r~ Massive, dense blue limestone 

g~~~ Lime~tone conglomerate 

Concealed (shale?) 

S;:2:):S:S2J Massive, dense blue limestone 

Concealed I shale ?) 

Shale 

Limeston 

pebbles 

"""- tSS~~ Upper IO'massi ~e e conglomerate. ""' ~ ! covered in part) 

w1th concretionary borders ........._ '':>t5;~~5:J 

z 

0 

f= 

<( 

~ 

<( 

0 

z 

r.n 

< 

Blue-blac ~ crystall ine Is. 

Quart zr te 

Blue loss 11iferous sha le 

u•u~ lime stone 

Blue ti ssi l e shale 

Fossillfer ous shale 

Gr ay loss ililerous shale 

Fissile sh ale 

·'·1/ 'i\" r!z e 

Blue fissi 

-=:::::3 

2 

KELLY G ULCH 

NEAR TRAIL 

___...,... 

/ 

. 'Ripple.ma rked (?) U NCONFORMITY (? ) 

ft~.:\J+:P .. Concealed 

Conceale 

1¥ ·...6·~~ ~ - ~:~··1~ - r:~n<??Y·I -- ---------- - Kelly lime stone 

~~ ~-=-=- ---------

Green fossrhfer u> hmestont 

---------

K ELL Y GULCH 

NEAR 

Tl? TOP T U EL 

------? ·----- ----

5 

!EAR HEAD OF 

KELLY GULCH, 

TIP T OP MTN 

Dark-blue fossrhferous crystalhne Is_. _ _ ____ -------:,. ,. .. ·:.: .. :: -

.f~HfP~ ;S;a~n~d ~m~:c;~cde o:u:s sngh::a :~::::~~l> \~J¥@ \'f, UNCONFOR""' ' " i'''i COo~ ~~ ~ f1K:·.:?.f.''.'·0'7::: Fine-grained greenish quartzite ;~L.' '~ ';{;;i~~~l Q.uartzit 

Concealed (shale?) 

Concealed tshale ?) _________ --· ___ ---___ --------_____ _ 

IE;5:;:=:Qrf- Upper .. silver pipe" 

Siliceous 

~~~~ "Silver p1pe" 

EXPLANATION 

-. 

Shale Umestone 

~artzite Shal y sandstone 

-

-

Shaly limestone 

~#~~t~Mj Arkose and 

pebbly tluartzite Conglomtfltl 

Vertical SC1le 

~=c~~~cE==========~ ==========='oo~==========3'so~~rr 

---

ttZ1le---

---

---

6 

C REST OF SPU R 

EAST S LOPE 

O F RANGE 

Fault 

Rusty quartz rte 

Thin-bedded limestone 

Fault 

Impure quartzrte 

Thin-bedded lrmestone 

Quar zr e 

Th~n bedded hmes one 

Pebbly quar zite 

PROFESSIONAL PAPER 200 P LATE ll 

est ne 

Brown striped, shaly quartzrte, 

Massive, coa rse-grained quartzite 

~~~~ Cherty Srlicified hme.:;Jone and pia y Is. 

Massive, medrum o coarse Is. 

1

---=._ --::__---::=:--=: " Silver prp ·· 

Silicified limestone 

Lower .. srlver pipe .. 

,,. :~:·:··~\ ~ Arkose 

PreC 

CREST OF SPU R 

AST SLOPE OF R G E 

E ST OF KELLY 

COL MNAR ECTIO HOWl G THE AR JATIO S l CHARACTER AND THlCKNE F THE KELLY LIME TONE, TnE \ , 'Dl F RMATION, AND P RT OF TRE MADER LIME TONE. 

200889-4.2 (Face p. 24) 
TERTIARY (?) EFFUSIVE IGNEOUS ROCKS 25 

replaced with irregular blebs of albite. The al:mndant 

epidote, which accounts for the greenish color of the 

rock, forms irregular grains or radiating bunches up 

to 2 millimeters in diameter and occasional well-formed 

crystals. It indiscriminately replaces both the crystal 

fragments and matrix. Calcite in irregular masses up 

to 5 1nillimeters in diameter is found mainly in the 

matrix, but it also replaces in part some crystal fragments. Sericite 'partly replaces the feldspar. The 

matrix m.ay consist in part of quartz and other secondary products. 

LOWER .ANDESITE -

The lower andesite, like the lower latite tuff, is found 

only in the low hills east of Granite Mountain, where 

it covers about 70 acres. Its northernmost exposure is 

west of its general trend and has evidently been offset 

along concealed :faults, as suggested on phite 2. The 

northernmost part lies on the lower latite tuff, but the 

southernmost part overlaps onto shale of the Sandia 

:formation. In places white rhyolite has been intruded 

along the lower contact, probably in the :form of sills. 

The lower andesite is overlain by the ·upper latite. It 

consists chiefly of tuff with a :few interbedded flows or 

sills and is about 750 feet thick. The tuff is sheeted, 

whereas the flows or sills are massive and are 2 to 3 

feet thick. The tuffs and flows strike a little west of 

.north and dip about 30() W. The dip is considerably 

less than that of the limestone and shale to the east 

and clearly marks an angular unconformity. 

The lower andesite as a whole is more variable in 

appearance than the latites both below and above it. 

The tuffs are dark . green and differ in color from all 

the other andesites of the district. Only occasional 

:fragments can be seen with the unaided eye. Some of 

the flows also are green and resemble the nonporphyritic lamprophyre dikes, but others near the middle of 

the :formation are dark purple where :fresh and dark 

gray where weathered. The texture of the flows 

ranges :from :rionporphyritic in the green to decidedly 

porphyritic in the dark-purple flows, whose prismatic· 

phenocrysts, which are as much as 7 millimeters in 

length, are altered to a black material embedded in a 

dense groundmass. Green specks· of epidote are 

common. 

The tuffs, as seen in thin section, consist chiefly of 

. two kinds of rock fragments, a small amount of interstitial epidote and calcite, and smaller amounts of 

quartz and chlorite. The most common :fragments are 

andesite with rare altered :feldspar phenocrysts in a 

:felty, very fine grained groundmass. They are only 

slightly replaced by epidote and calcite. Less common are somewhat coarser and more altered fragments 

that consist of an intimate intergrowth of altered feld-

. spar, quartz, epidote, calcit~, and chlorite. _ A few 

:fragments of altered hornblende are present and are 

now represented by chlorite,, quartz, and calcite. 

200889-42- -3 

..__ . The purple r9ck, as shown in thin section, originally 

consisted of brown hornblende phenocrysts in a n1icrogranular groundmass of pl~gioclase' laths and is therefore called hornblende andesite. The hornblende 

phenocrysts have· been in part replaced by chlorite and 

in part by pseudomorphous rims of fine-grained hematite with cores of calcite, chlorite, and quartz, and 

represent the black prismatic phenocrysts seen megascopically. The plagioclase l~ths in the groundmass 

are considerably altered to sericite and calcite. Small 

aggregates of secondary quartz ·and abunda1itly scattered grains of hematite, epidote, and chlorite are also 

present. 

UPPER L.A TITE 

The upper latite :forms the east slope of Granite 

Mountain, where it rests on the lower andesite, and 

the eastern portion and crest of Stendel Ridge, where 

its rests uncom:formably on shale on the Sandia formation. It is overlain by the rhyolite porphyry sill, 

which so closely resembles the·latite on weathered surfaces that it can be distinguished only by its abundance 

of large ·quartz phenocrysts. -For this reason the contact between the upper latite and rhyolite porphyry 

is somewhat arbitrary where exposures are poor. The 

upper latite consists mainly of tuffs and breccias, with 

a massive, interbedded flow near the top of the :formation on Stendel Ridge. This flow and a mass of coarse, 

purple breccia on Granite Mountain have been mapped 

as distinct members of the :formation. The . upper 

latite is probably the oldest volcanic :formation in the 

main range, but its ag.e relation to the purple andesite to the south is not known (see fig. 2). Its average 

dip is about 30° W., and its minimum calculated thickness is 1;200 :feet on , Granite ¥ountain and 1,200 to 

1.400 feet on Stendel Ridge. The flow and the tuffs 

are not easily distinguished :from each other on fresh 

surfaces, but in weathered outcrops the tuffs and breccias show a distinct htmellar structure (pl. 7, A) in 

which individual layers are an inch or more thick, 

whereas the flows are massive. 

Tuff a;nd breccia.-On Stendel . Ridge the basal 15 

:feet consists chiefly of angular and some rounded 

fragments of the underlying limestone, shale, quartzite.,. 

and grains of feldspar and quartz derived :from preCambrian granite. These grains locally give this basal 

bed the appearance of rhyolite tuff. The matrix of 

this bed consists of tuff, which in places has been so 

much altered to epidote that it is yellowish green. 

Above this basal b~d 'is a massive gi·ay tuff, whi~h is 

. greenish on a weathered surface, has a uniform texture, 

and is so crowded with crystals that it appears more 

like a. fine-grained crystalline rock. It probably represents a sorted material :from which the finer ash particles were removed either by wind action . during the 

eruption or by the more rapid descent of the heavier 

crystal :fragments. The ,crystals consist chiefly of 
26 MAGDALENA MININ·G DISfl'RICT, NEW MEXICO 

white plagioclase with an occasional pink orthoclase 

grain and scattered -little specks of a black mineral. 

Most of the tuffs of the upper latite are purplish 

gray, with a greenish tone on altered surfaces. At 

the 7,4.10-foot peak on Stendel Ridge they are bleached 

white. They resemble porphyry but their fragmental 

character can be recognized by the large number of 

chilled latite fragments, and their tuffaceous character 

is especially shown by their lamellar structure on a 

weathered surface and locally by beds or lenses of 

breccia. The crystal fragments are mostly less than 

3 millimeters in diameter but may be as much as 7 

millimeters. They consist of white plagioclase and pink 

orthoclase and a black ferromagnesian mineral. 

The purple breccia member is well exposed on the 

south slope of Granite Mountain. This apparently 

thick zone can be traced to the north for only a short 

distance before it pinches out. Farther north just to 

the east of the peak are two horizons of purple breccia 

with a few scattered quartzite fragments, and similar 

rock is exposed on the northeast side of the mountain. 

These exposures are very probably local lenses, for 

none can be traced very far; yet locally they have a 

thickness of 25 feet and more, and because of their 

color are striking features. The breccia consists of 

fragments up to 2 inches in diameter, many of which 

are well-rounded, and simulates a conglomerate. The 

fragments consist of whitish felsitic fragments embedded in a purple to blue ·matrix. 

One thin section of the lower tuff consists of about 

70 percent of feldspar fragments, many of which have 

partial crystal outlines, and only a few fragments of 

latite. The feldspar fragments consist largely of 

oligoclase-andesine and a few grains of orthoclase and 

are considerably replaced by sericite and calcite. The 

original matrix, which consisted of extremely finegrained material, is now largely replaced by chlorite, 

sericite, and calcite. Most of the chlorite contains 

small magnetite grains, especially. around the borders. 

A few small detrital grains of quartz, apatite, magnetite, and zircon are present, together with a little 

secondary quartz. 

Thin sections show most of the tuffs to consist approximately of 30 to 40 percent of crystal fragments 

and 60 to 70 percent of matrix. The fragments are 

predominantly of plagioclase, but a few are of orthoclase, and some are "ghosts'' of a ferromagnesian mineral. The plagioclase (oligoclase-andesine) forms 

rectangular to irregular grains· and is somewhat replaced by sericite, calcite, and some epidote. The 

original ferromagnesian minerals, chiefly biotite but 

probably also hornblende, are now marked by local 

segregations of fine-grained iron oxide with chlorite 

and sericite. Quartz is partly in single grains about 

1 millimeter in diameter, but most of it forms scattered 

fine-grained aggregates up to 0.3 millimeter in diameter, which show undulatory extinction and are probably secondary. Magnetite, apatite, and zircon are 

the minor accessory minerals. The matrix consists of 

a light-brownish microfelsitic material of low birefringence that seems to be chiefly orthoclase. Calcite 

associated with secondary quartz forms irregular 

patches 2 millimeters in diameter that are irregularly 

scattered through the matrix. 

Flow.-The latite flow on Stendel Ridge is dark 

purplish where fresh, but more commonly it is altered 

to .gray or greenish gray. It is porphyritic and resembles the rhyolite porphyry of the intrusive rocks, 

but quartz phenocrysts are absent. Feldspar, in crystals mostly less than 2 millimeters in diameter, is the 

predominant mineral; but a smaller amount· of altered 

biotite is also present, some grains of which are dull, 

scaly, and of hexagonal outline. The groundmass is 

dense and flintlike. 

Thin sections show the flow to be very porphyritic. 

The phenocrysts constitute from 30 to 40 percent of 

the rock, and of these the feldspars constitute about 75 

percent and biotite, augite, and a little hornblende 

about 25 percent. The feldspar is chiefly oligoclaseandesine, with an occasional grain of orthoclase. The 

oligoclase-andesine forms rectangular to irregular 

grains, many of which are rounded and ~mbayed owing 

to resorption. A few grains are zoned, and others 

have been in part replaced by a later feldspar of l-ower 

refringence, probably albite, which forms veinlets and 

irregular stringers in these plagioclase grains. In 

most sections the feldspar is slightly altered to sericite 

and calcite and has occasional epidote grains, but in a 

specimen collected from the small outcrop .south of the 

Waldo tunnel the plagioclase has been almost completely replaced by sericite and calcite. One section 

had a few rounded and embayed orthoclase grains. 

Biotite is the most common of the ferromagnesium 

minerals. It is partly or completely resorbed and is 

thus not readily recognized megascopically. The partly 

resorbed crystals contain fine-grained magnetite along 

their borders and cleavage planes, and those completely 

resorbed are represented chiefly by pseudomorphous 

areas of fine-grained magnetite with interspersed chlorite, quartz, and epidote, and in one section by muscovite. Augite, like the other phenocrysts, has undergone 

partial resorption. and replacelllt~nt by callcite and 

quartz. Some grains are clouded with dustlike inclusions of iron oxide. Hornblende is absent in most 

sections, but a little brown hornblende is present in a 

specimen taken near the crest of the 7,562-foot hill on 

Stendel Ridge. Magnetite, apatite, and titanite are 

the minor accessory minerals. The groundmass is 

cryptocrystalline to micro granular, unlike that typical 

of andesite, and probably contains considerable orthoclase. On the basis of the texture the rock is classed 

as a latite. 
TERTIARY ( ? ) EFFUSIVE IGNEOUS ROCKS 27 

PURPLE ANDESITE 

The purple andesite forms the basal volcanic formation south of Kelly. In most places it lies on the Abo 

sandstone, in others on the Madera limestone, and in 

stiil others it is separated from the sedimentary rocks 

by the latite porphyry sill that extends southward from 

Kelly. It is overlain by the banded rhyolite at the 

south end of the district, where its contact is well-exposed; but i~ the low hills ~etween Patterson Canyon 

and Kelly it is in fault contact with some of the younger 

volcanic rocks. It consists chiefly of tuffs and breccias 

with some flow material near th~ top. The lower portion is a · rather coarse breccia, locally cohtaining many 

well-rounded fragments of the Madera and Abo formations as much as 5 inches in diameter and well-rounded 

fragments of andesite, some of which are a foot in 

diameter. The coarse layers are lenticular and are interbedded with layers of tuff. The formation has an 

estimated thickness of 1,200 feet. 

The. purple andesite presents some variations in appearance, but with few exceptions its purple color is 

characteristic. Locally its color may grade into a lavender or bluish tint, and at the contact with the Abo 

Bandstone it is red. The flow material near the top . 

of the formation is gray. Texturally the rock appears 

porphyritic with white tabular plagioclase crystals, 

most of which are less than 3 ;millimeters in diameter, 

and a less prominent black prismatic mineral embedded 

in a dense purple matrix. 

Thin sections of the flow material are variable. The 

phenocrysts constitute as much as 30 percent of the 

rock and consist of plagioclase and an altered feiromagnesian mineral. The plagioclase ranges from sqdic 

oligoclase to andesine. It is partly replaced by calcite 

in most sections and by albite in others. The ferro- · 

magnesian mineral has been completely a.ltered to finegrained pseudomorphous iron oxide, ·which retains the 

original mineral outline and suggests hornblende (pl. 

10, B). The cores of the pseudomorphs may consist of 

calcite and quartz impregnated with iron oxide. Augite has been observed in only one thin section and is 

partly replaced by calcite and quartz. The groundmass 

in some varieties is cryptocrystalline, showing microspherulites and a mesh of hematite needles (pl. 10, A), 

which probably represent resorbed and oxidized amphibole. This mesh does not penetrate thephenocrysts : 

but is distinctly limited to the: groundmass. In other-· 

varieties the groundmass is trachytic, and in still others · 

it is microgranular and consists of short plagioclase , 

laths bordered and in part replaced by albite. Secondary iron oxides disseminated through the groundmass 

somewhat obscure it. Aggregates of quartz (all prob- · 

. ably secondary), varying amounts of calcite, epidote, 

and an occasional small flake of pale-green ·chlorite are 

also present. Apatite and zircon are the minor accessory minerals. 

The tuffs, as seen in thin section, consist of andesite 

fragments and crystal fragments which are chiefly of 

oligoclase and an altered ferromagnesian mineral, with 

minor amounts of orthoclase, embedded in an extremely 

fine grained matrix. The. character of the matrix is 

obscured somewhat by calcite and: by iron oxide, which 

is especially common along the borders of the fragments. 

The oligoclase fragments are only slightly replaced by 

sericite and calcite, but the original ferromagnesian 

mineral whose outlines are like those of hornblende 

is now represented only by aggregates composed of a 

chloritic mineral, with or without sericite, calcite, and 

quartz with a border of hematite. Quartz is variable 

in amount, and most of it is probably secondary. It 

occurs in small grains 1 millimeter in diameter, but more 

commonly it forms mosaics with undulatory extinction 

or irregular chalcedonic patches. Apatite, magnetite, 

and zircon are the mino·r accessory minerals. 

The andesite fragments are commonly unaltered and 

are in sharp contrast with the altered tuffaceous 

matrix. They consist of porphyritic andesite with a 

felty to trachytic groundmass. The phenocrysts are 

plagioclase crystals as much as 1.2 millimeters in length 

and ferromagnesian minerals now completely altered to 

muscovite with or without calcite and smaller amounts 

of quartz ; but their original outlines, marked by iron 

oxide, resemble those of biotite, hornblende, and less 

cl~arly augite. COl 

. BANDED RHYOLITE ~ 

The banded rhyolite, th~ only prominent banded vol- ~ 

canic rock in the district, is the most widely distributed 

of the effusive rocks. It forms a discontinuous narrow 

band about 4 miles long and is the only formation that 

extends from the south end of the district into the central area and thus permits the determination of the 

relative age · of the formations in the two parts of ·the 

district · with respect to each other (fig. 2). A small 

exposure occurs at the north base of the range just east 

of Anchor Canyon and 2 miles northeast of the main 

,mass, and extensive masses are found west of the Granite 

Mountain area and in the hills north of La J enze Creek. 

West of Granite Mountain it overlies the Tertiary ( ~) 

sandstone unconformably. In the central part of the 

district it is separated from underlying latite or andesite 

by the sill of rhyolite porphyry, and in the southern 

part it overlies the purple andesite. The strike of its 

banding in general conforms to the strike of the region. 

The angle of dip is approximately 30° to 40° ~ but 

locally, as west of Kelly, it may be 50°. The thickness 

of the formation ranges between 250 and 400 feet in 

the southern part of the region and apparently between 675 and 875 feet west of Stenael Ridge, although 

the thickness may be exaggerated by concealed faults. 

The banded rhyolite consists almost entirely of flow 

material characterized by alternating layers or thin 

lenses of hard dark-colored and soft light-colored finely 
28 MAGDALENA MININ-G Disri'RICT, NEW MEXICO 

porphyritic rhyolite. Its prevailing colors are shades 

of gray and pink, but at the south end of the district it 

is purplish red and becomes redder toward its contact 

with the overlying red andesite. The layers consist of 

dense flintlike groundmasses containing thinly scattered crystals of orthoclase, biotite, and a little quartz 

mostly less than 2 millimeters in diameter. The banding is intensified, especially in the southern area, by 

thin lenses of gray finely granular quartz up to 5 inches 

in length. In the gray facies in general, and in the 

upper portion of the red facies, these lenses are mostly 

less than a quarter of an inch long and give the 

weathered urface a "knotty" appearance. 

In thin section the rock is variable. The red facies 

with a number of "knots" shows only a few phenocrysts 

of orthoclase, which have been partly replaced by 

mosaics of quartz. Quartz phenocrysts are rare and 

small, usually less than 0.1 1nillimeter in diameter. 

They are irregularly distributed and are embayed by 

pa.rtial resorption. Remains of probable biotite are 

marked by a few fine-grained aggregates of quartz 

surrounded by rims of iron oxide. The lenses and 

knots consist of very fine grained quartz, which is free 

from the iron oxide ·dust that clouds the matrix ·and 

accounts for its red color. Several lenses and stringers 

consist of radial growths of brownish cryptocrystallii1e 

material. These radial growths have an index o:f 

· refraction less than that o:f Canada balsam and probably are intergrowths of potash :feldspar and cristohalite. 4 5 They usually contain crystallize9. quartz at 

the center and occasionally at the edge. It is evident 

that the lenses are secondary and probably fill vesicles 

of an original pumice. The groundmass is microfelsitic to glassy and is streaked by the' unequal distribution 

of iron-oxide dust. 

The gray :facies north of Kelly co.nsists.of a slightly 

porphyritic rock containing a :few phenocrysts of 

clouded orthoclase and partly resorbed biotite. Flow 

structure is well-developed in the cryptocrystalline to 

microgranular groundmass sprinkled with iron-oxide 

·dust. Irregular streaks and aggregates of fine-grained 

quartz are common. Included in the rock are several 

finely sericitized rhyolite fragments that contain quartz 

and orthoclase phenocrysts. Apatite and zircon are 

rninor accessory minerals. 

The tuff at the base of the banded rhyolite is stratifled and has the general appearance of a sedimentary 

rock. It is whitish to yellowish gray and in places is 

streaked and banded by limonite stains. It ranges in 

texture from fine-grained and chalky to distinctly 

fragmental. Quartz and orthoclase with chalcedony 

and opal are the only recognizable minerals. They are 

accompanied by fragments of a whitish-gray to green 

felsitic rock as much as half an inch ·in diameter. 

Under the microscope the fine-grained tuff does not 

45 Ross, C. S .• oral communication. 

appear very different frmn the gray flow rock except 

for the absence of banding and the presence of considerable sericite. Fron1 a rock composed chiefly of 

small glass fragments in a 1ninutely granular matrix 

the tuff grades into one in which :fragments o:f rhyolite 

and orthoclase constitute approximately 35 percent. 

Plagioclase was noted in only one thin section. Biotite 

is extremely scarce. Secondary minerals are most common in the more pseudoporphyritic and fragmental 

varieties. The principal secondary minerals are sericite and quartz, accompanied by considerable calcite in 

one thin section and by veinlets of quartz in others. 

Li:monite pseudomorphs a:fter pyrite are disseminated 

through only one section, although limonite staining is 

present in others. . · 

RED ANDESITE 

The red andesite, which is restricted to the area south 

of Kelly, directly overlies the banded rhyolite near the 

Eouthwest corner of the district. In the :foothills south 

of Kelly it has been so faulted against older rocks or 

partly covered by alluvium that its lower contact is 

not exposed. It is in general overlain by the pink 

rhyolite, the youngest of the effusive rocks in the southern part o:f the district, but in the .foothills just north 

o£ South camp it is apparently conformably overlain 

by the red rhyolite. However, the contact is not extensive and is in general so obscured by debris that the 

relation is indefinite. South o:f South Camp the red 

andesite and the upper andesite form opposite banks 

of a gully, but their contact is concealed by debris. It 

is regarded, however, as an unconformity and is more 

:fully discussed on page 29. The red andesite consists 

of interbedded flows and tuffs, although the tuffs are 

found chieflly at its base. One of the basal beds 4 

to 6 feet thick is whitish gray. The formation dips 

30° or less westward, and it ranges in thickness from 

a bout 500 to 800 feet. 

The red andesite presents considerable. variation in 

appearance. The type rock has the appearance of red 

hematite, and its texture is thoroughly dense or only 

sHgh~ly porphyritic. It grades into a reddish-gray or 

a purplish-gray :facies, in which black altered phenocrysts are :few and a v.erage about 1 millimeter in diameter. Some of t~e flows are dark gray and scoriaceous 

at the top, and where their smaller vesicles are filled 

with calcite or chalcedony they are distinctly amygdaloidal. 

In thin section the typical red nonporphyritic andesite (pl. 10, 0) consists mainly of small lath-shaped 

andesine crystals in a dark-red matrix thoroughly impregnated with iron oxide. It also contains many 

small round cavities, most of them less than 0.1 millimeter in diameter, that are filled with chalcedony, but 

some are filled mainly with calcite and .o~hers with 

quartz mosaics. The largest vesicles (pl. 11, B) are 

filled with calcite and lined with chalcedony from 
TER'l'IARY ( ? ) EFFUSIVE IGNEOtJS ROCKS 29 

which a few prismatic quartz crystals have grown inward. Calcite may also· form irregular streaks and 

patches. Phenocrysts of a ferromagnesian mineralaugite or hornblende-have been altered and are now 

l'e'Presented by pseudomorphs of red iron oxide and 

chalcedony. 

In the porphyritic facies the original phenocrysts 

whose outlines suggest hornblende are represented by 

shells of iron oxide filled with chalcedony. They are 

most common in the sc;oriaceous facies, but even there 

they constitute less than 5 percent of the rock. The 

groundmass is felty to trachytic and consists of plagioclase laths 0.2 millimeter and less ih length. Minute 

grains of iron oxide are peppered through the groundmass. The trachytic variety is much silicified with 

fine-grained quartz mosaics interstitial to the feldspar 

laths. In an andesite near the top of the formation 

secondary calcite is bordered by a green mineral, probably celadonite. This mineral, which is better developed 

in the upper andesite, is described on page 30. 

RED RHYOLITE 

An altered rock, tentatively determined as 1;ed rhyolite, is confined to three low hills north of South 

Camp. It somewhat resembles the red andesite but 

is paler and more purp1ish red and . is more distinctly 

silicified. It contains 'thinly scattered phenocrysts of 

feldspar and biotite less than 1 millimeter in diameter . 

but no phenocrysts of quartz, although smalf cavity 

fillings of quartz resemble phenocrysts. It is much 

fractured and re'cemented by quartz veinlets in places, 

and some of the quartz crystals that line cavities are 

topped by small, tabular barite crystals. Quartz veinlets lined with red iron oxide are also conspicuous. 

In some thin sections phenocrysts· of orthoclase and 

biotite are practically absent and in others they constitute as much as 20 percent of the rock. The orthoclase is unaltered in part, . but some crystals are 

considerably replaced by a clay mineral of the montmorillonite-beidellite . group. Some grains of similar 

outline but completely repl,aced by a clay "mineral ·and 

qua~tz may represent plagioclase. Some biotite shreds 

are slightly resorbed and have the usual border of 

iron oxide. In some places ghosts of former crystals 

whose outlines suggest hornblende have been completely altered to a mixture of yellow or brown clay 

and chalcedony coated with iron oxide. 

The groundmass ranges from glassy to granular and 

is usually clouded with "dust," the larger particles of 

which are recognizable as iron oxide. In the coarsergrained varieties. orthoclase can be recognized. Quartz 

veinlets are common, and quartz also occurs in small 

aggregates and disseminated irregular grains, som~ of 

which appear to be secondary and some primary. The 

tentative recognition of primary quartz together with 

the dominance of orthoclase among the phenocrysts 

justifies the field -designation of the rock as rhyolite, 

although identity is obscured by the amount of 

secondary quartz. 

The red rhyolite evidenpy overlies the red andesite 

in essential conformity and is cappe~ in one place by 

the pink rhyolite. Although its relations to the pink 

rhyolite are obscured to some extent by faulting, the 

red rhyolite was evidently beveled by erosion before 

the eruption of the pink rhyolite, which rests <?n red 

andesite a short distance east and north of the larger 

exposure of red rhyolite. No contact between the red 

rhyolite and the upper andesite is exposed, but the red 

rhyolite is believed to be the older, because of its conformable relation with the red andesite, which, as 

shown below, appears to be unconformably overlain by 

the upper andesite. 

The thickness of the red rhyolite is not determinable, 

for nowhere in the district is its upper and lower contact eX:posed in the same outcrop; nor is its angle of 

dip known. But assuming an angle of dip of 30°, 

shown by the red andesite to the south, the red rhyolite has a minimum thickness of 400 feet. 

UPPER ANDESITE 

The upper andesite, which is exposed in the extreme 

southwest cor1~er of the district, extends a considerable 

distance to the west and northwest and constitutes the 

lower parts of Magdalena Mountain and Elephant 

Butte (pl. 3, .A), just beyond the west boundary of the 

district. It is also red but distinctly different from 

the red andesite previously described, as it contains 

abundant well-defined phenocrysts of plagioclase, 

biotite, and augite. 

The upper andesite consists chiefly of flow material 

but includes some tuff. In the extreme southwest corner of the district the upper andesite has a platy or 

lamellar structure similar to that in the tuffs of the 

other formations in the district . . Its minimum thick- . 

ness is estim~ted at 300 feet, but its maximum thickness . 

is probably much greater. 

The structural relations of the upper andesite are. in 

part obscure. The eastern boundary discordantly cuts 

off the adjacent banded rhyolite and red andesite along, 

a gulch bottom and is so nearly straight as to suggest 

a fault, but at no place was the contact with these rocks . 

actually seen. At' the head of this gulch, however, the 

pink rhyolite conformably overlies the glassy top of the 

upper andesite and continues eastward over the red 

andesite without being displaced. If, therefore, a fault 

could have separat~d the upper andesite from the older 

rocks, it .must ha.ve formed before the eruption of the 

p!nkrhyolite. It shquld have dropped the glas$y top 

of ~he upper andesite to the west, and erosion should 

then have completely removed the upper andesite from 

the area east of the supposed fault without removing 

. even the glassy top on the west. An alternative view 
30 MAGDALENA MININ-G DISII'RICT, NEW MEXICO 

js that the red andesite and banded rhyolite had been 

previously eroded to a steep slope, perhaps along a 

fault, and that the upper andesite later banked up 

against the slope. The pink rhyolite was erupted so 

soon afterwards that it flowed conformably over the 

glassy top of the upper andesite, overlapping eastward 

onto the erosion surface of the red andesite. This 

interpretation is illustrated in plate 4 (sec. G-G'). 

The upper andesite varies somewhat in appearance. 

The type rock is light brick red, " si·milar to the red 

andesite, but is distinguished by abundant phenocrysts 

of glassy to white plagioclase, 2 to 4 millimeters long, 

black biotite, and pyroxene crystals 1.5 millimeters in 

diameter. Furthermore, it is characterized by an 

abundance of chalcedony geodes from a fraction of an 

inch to 3 inches in diameter, fragments of which form 

a distinctive feature of the weathered surface. Although its megascopic appearance and its content of ferromagnesian minerals differ so.mewhat from place to 

place, the upper andesite is not readily divisible in the 

field into separate flows. 

As seen in thin section the upper andesite ranges from 

a hypersthene andesite to a hypersthene-augite andesite, 

and in the glassy top of the :formation biotite and brown 

hornblende are also present. Phenocrysts form as much 

as 25 percent of the rock, and of these the most common is plagioclase (labradorite), which occurs in wellformed and tabular crystals conspicuously larger than 

the ferromagnesian phenocrysts (see pl. 11, A). · The 

feldspar phenocrysts are zoned and compar~tively 

clear, but many are in part replaced by calcite and by 

stringers of a pale-brown mineral of the montmorillonite-beidellite group, which lie along cleavage cracks and 

also form central blotches. This mineral will be discussed more fully below. 

The .most common of the ferromagnesian minerals 

has been completely replaced by fine-grained aggregates 

of celadonite with borders of hematite, but the outlines 

of the original crystals are well-defined and their square 

cross sections with truncated corners strongly suggest 

that the original mineral was hypersthene. Few of 

them are more than 5 millimeters long. 

In the lower part of the formation the alte·red hypersthene was the only primary ferromagnesian mineral 

represented, but in the middle and upper part augite 

is also present. In contrast to the other pyroxene it 

is unaltered and forms crystals up to 1 millimeter in 

length. Still higher, in the glassy facies just below 

the pink rhyolite, deep-brown and reddish-brown biotite is present. In one thin section·iron oxide associated 

with secondary quartz may represent resorbed biotite or 

hornblende. Bunches and streaks of fine-grained secondary quartz and geodes of chalcedony are common in 

so.me places. The minor accessory minerals are magnetite and apatite. 

The groundmass is trachytic ap_d coneists of small 

feldspar laths in a brown glassy to cryptocrystalline 

matrix. Minute grains of red iron -oxide are disseminated through the groundmass. 

The eastern part of the upper andesite just below the 

vink rhyolite is a gray porphyritic glass of pitchstone, 

in places somewhat devitrified, with phenocrysts of 

glassy plagioclase (andesine), biotite, brown hornblende, 

and less commonly augite and altered hypersthene. 

Similar rock is abundantly exposed at the top of the 

andesite in Elephant Butte, just to the west of the district, and black andesite obsid~an occupies the same 

position in Magdalena Mountain, just to the north of 

Elephant Butte. The glassy groundmass of the gray 

pitchstone shows perlitic cracks, and that of the black 

rock at Magdalena Mountain is full of radiating 

trichites. Irregular patches and microgeodes of zeolites with cores of opal and some chalcedony are common in the gray pitchstone (pl. 11, 0). 

Alteration products that are conspicuous microscopic 

features of the upper andesite and are present to a minor 

· degree in the underlying volcanic rocks deserve special 

comment. The most abundant of these have the general properties of the montmorillonit~-beidellite group 

of minerals. The mineral replacing the plagioclase is 

pale coffee brown and forms micaceous and exceedingly 

fine grained aggregates. The same or a similar mineral 

has also replaced some of the feldspar and hornblende 

( ?) phenocrysts in the red rhyolite. In some thin sections hypersthene also has been replaced by a darkbrown, 1ibrous mineral of strong pleochroism, whose 

indices of refra-ction range from about 1.52 to 1.58. 

Intergrown with the brown fibers is a very small amount 

of green fibers, suggesting the possibility that the aggregate consists of two minerals with birefringences less 

than those recorded. 

Other thin sections show a ·mineral that is si;milar, 

but it is pale green and slightly pleochroic. The habit 

of the aggregates is that of serpentine, but the birefringence suggests clay minerals, probably rich in the 

nontronite. molecule.46 

The dark-green mineral with fibrous habit that replaces hypersthene a short distance below the top of 

the upper andesite has indices of re.fraction, moderately high birefringence, and pleochroism that agree 

YTith those of celadonite. Some hypersthene crystals 

are entirely replaced by this mineral, whereas in others 

hematite fills the · original transverse cracks and the 

celadonite fibers or plates lie on both sides normal te; 

the hematite-filled crack. In still others the celadonitic material encloses a pale coffee-brown opal whose 

index of refraction is 1A20. Besides forming pseudomorphs after hypersthene, the celadonitic material also 

forms ringlets (pl. 12, -:4.) and wormlike streaks in the 

groundmasses of both the upper and the red andesites. 

In the glassy top of the upper andesite it also surrounds small growths of zeolites and opal, and in the 

46 Ross, C. S., and Kerr, P. F., The clay minerals and their identity: 

Jour. Sed. Petrology, vol. 1, p. 60, 1931. 
TERTIARY (?) EFFUSIVE IGNEOUS ROCKS 31 

cryst~lline groundmass it surrounds calcite and inelusions of groundmass in calcite. 

These replacement minerals are the result of a selective process, for although hypersthene has been completely replaced and plagioclase partly replaced, augite 

and biotite remain unaltered. These minerals are 

usually regarded as the products of normal weathering, 

but, as the groundmass is fresh and the rock does not 

show the usual signs of weathering, they are believed to 

· be a product of hot solutions. 

The two partial chemical analyses presented in colurns 1 and 2 below express the results of alteration. 

The high silica content, com.pared with that of the 

average andesite in column 3, may be attributed to the 

development of quartz. The high content of ferric 

oxide and almost negligible amount of ferrous oxide 

express the development of hematite, and perhaps 

celadonite and nontronite, at the expense of hypersthene. The low content of magnesia also reflects the 

replacement of hypersthene. The percentages of lime 

. are not indicative, as the deposition of calcite tends 

to offset any removal of lime during alteration of 

plagioclase to montmorillonite or similar minerals. 

Partial; analyses of upper andesite and average andesite 

Si02 _______ :____________________ 64.93 

Fe20a - __ ____________ _____ - _- _- _ 5. 42 

FeO _____________ ___ __ ___ -- _ _ _ _ . 49 

MgO -------------------------- ·. 95 CaO _____________ _ ..: ___________ _ · 3. 64 

2 

63. 41 

4. 63 

. 41 

. 36 

4. 21 

59. 59 

3. 33 

3. 13 

2. 75 

5. 80 

1. Upper andesite 2,000 feet due south of South Camp; A. R. 

Ferguson, analyst. 

2. Upper andesite from extreme southwest corner of district; 

A. R. Ferguson, analyst. 

3. Average of 87 samples of andesite; Daly, R. A., Igneous 

rocks and their origin, p. 26, New York, 1914. 

PINK RHYOLITE 

The pink rhyolite forms the crest of the high spur· 

in the southwest corner of the district and caps smne 

of the low hills south and west of Kelly. It also caps 

Elephant Butte and Magdalena Mountain, west of the 

area mapped. At Magdalena Mountain (pl. 3, A) the 

capping flow connects with a dike of northerly trend 

that forms the east cliff face of the mountain. 'For 

the most part the pink rhyolite lies directly on the 

red andesite, but at South Camp it caps the red rhyolite and in the extreme southwest corner it covers the 

upper andesite. These relations together with its 

relativeiy low angle of dip-about 10° W.-indicate 

an unconformity at its base. Bleached tuffs at the 

base of the pink rhyolite on the low isolated hill west 

of Kelly have an abnormal dip of 65° W. The thickness of the · pink rhyolite within the district is about 

400 feet, but its total thickness may be much greater. 

The pink rhyolite is the youngest of the effusive rocks 

• 

I ' 

with the possible exception of the white felsite tuffs 

' in the northwest part of the district. It is cut, however, in the low hills southwest of Kelly by the rhyolite porphyry, which is among the oldest of the 

Tertiary ( ?) intrusive rocks. 

The pink rhyolite comprises a lower member of tuff 

and a dominant upper member of one or more flows. 

Unquestioned tuff is found in the low isolated hill 

west-northwest of Kelly. Its lower portion is wellbedded and resembles cream-colored sandstone where 

not appreciably altered, but the greater part of it is 

bleached and peppered with rust spots. Where fresh 

· the flows are massive, but where considerably weathered 

they have a pronounced platy structure; and in places 

they contain so many inclusions they are not readily ' 

distinguished from tuff. In the extreme south end of 

the district the rhyolite contains many elongated cavities up to 2 inches in length. The cavities have their 

long axes uniformly oriented, giving the rock a somewhat banded appearance, but marked flow structure 

is absent. , 

The type rock of the flows where fresh is mostly 

pink or purplish pink and locally red, but weathered 

surfaces are somewhat faded. It has a dense to finely 

porous groundmass with thil).ly scattered phenocrysts 

of orthoclase, quartz, and very little biotite that constitute 5 to 10 percent of the rock. The orthoclase 

phenocrysts are white to glassy and are as much as 

2 millimeters in length. The quartz phenocrysts, 

which are thinly scattered colorless to smoky grains 

about 1 millimeter in diameter, distinguish the pink 

rock from the other effusive rocks, although minute 

aggregates of secondary quartz in the red rhyolite so 

resemble the quartz phenocrysts in the pink rhyolite as 

to be misleading. 

In thin section the phenocrysts of orthoclase and 

quartz are shown to be commonly rounded and resorbed. The orthoclase is locally a little sericitized 

along cleavage cracks. A few shreds of unaltered 

biotite are present, but the biotite is mainly altered to 

pseudomorphic areas of fine-grained . quartz and 

sericite. 

The groundmass is cryptocrystalline to very finely 

crystalline and somewhat vesicular. Iri places it is 

partly impregnated with secondary quartz and 

chalcedony. Cryptocrystalline. to fibrous chalcedony 

commonly fills or lines vesicles, and fine aggregates im-

. pregnate the groundmass. 

The typical tuff consists of crystal fragments of 

quartz, orthoclase; a few plagioclase grains, and fragments of rhyolite embedded in a very fine grained matrix 

whose low birefringence corresponds to that of quartz 

and orthoclase. The crystal fragments average ab<;mt 

1 millimeter in diameter. The tuff is roughly stratified, 

fragments being more common in some layers than in 

others. The more lamellar beds are seen in thin section 
32 MAGDALENA MINING DISTRICT, NEW MEXICO 

to consist of dark br~wn pumice fragments of rounded 

and cusplike outlines and a few crystal fragments in an 

extremely fine grained sericitized matrix. 

WHITE FELSITE TUFF 

Remnants of bleached sheeted tuff beds flank the 

north end of the lower andesite hills east of Granite 

Mountain. They are light greenish gray and weather 

to light gray or white.· They contain thinly scattered 

fragments of feldspar up to 4 millimeters· in diameter 

and conspicuous fragments of dull-green material. 

In thin section the tuff is seen to consist mainly of 

altered glass fragments, many of which are crescentic 

and cuspate. Crystal fragments of albite-oligoclase, a 

few orthoclase grains, a few minute crystals of zircon, 

and altered rock fragments are also present. The crescentic and cuspate fragments are now replaced by minerals of the montmorillonite-beidellite group. The 

matrix appears microfelsitic and locally contains considerable chalcedony. Because of alteration and the 

large amount of original glass fragments the true character of the rock is unknown, and it is therefore given 

the noncommittal name felsite. tuff. 

The tuff dips at very low angles and is separated 

from the underlying effusive rocks by a considerable 

angular unconformity. It therefore corresponds in its 

structural relations to the bleached tuff at the base of 

the pink rhyolite; but it is too isolated and too different in composition to be correlated with it. Its color 

also suggests a close relation to the white rhyolite 

dikes, the youngest intrusive rock in the district, but -

it differs from them in containing a preponderance of 

plagioclase and no quartz fragments. Its distribution 

on an erosion surface of relatively low altitude suggests that it was extruded after the other volcanic rocks 

had been tilted and eroded to the extent that the relief 

of the Granite Mountain area. was almost as moderate 

as it is at present. It may be; therefore, that the white 

felsite tuff is the youngest igneous rock in the district. 

TERTIARY (1) INTRUSIVE IGNEOUS ROCKS 

GENERAL STATEMENT 

The Tertiary ( ~) intrusive igneous rocks, insofar as 

relative ages can be determined within the district, 

are younger than all the effusive rocks, with the possible exception of the felsite tuff, and are divisible into 

three groups. The earliest group comprises sills and 

dikes of latite poryphyry and rhyolite porphyry, which 

were intrpded before the main period of faulting and 

are therefore closely related in time to the effusive 

rocks. The second group includes stocks-of monzonite 

and granite, which followed the main period of faulting, and may have been localized at the intersections ofmain fault systems. The small stocks of andesite on 

Granite Mountain and the sill-like mass on Stendel 

Ridge may also belong to this group. The third group 

includes dikes of lamprophyre and white rhyolite, 

which cut the stocks and older rocks and are the most 

closely related in time and structural relations to the 

ore deposits of the district. The rhyolite porphyry 

of the first group and the members of the third group 

extend throughout the length of the district, although 

they are most conspicuous north of Kelly and in the 

Granite Mountain area. The stocks are in the main 

range north of Kelly and at Granite Mountain. _The 

stocks of monzonite and granite in the main range are 

in contact locally with metamorphosed limestone. Although no stocks are exposed south of Kelly, the presence of metamorphic minerals ~n limestone along a 

major fault zone in the Linchburg tunnel2 mil~s south 

of Kelly suggests that there be another stock in that 

vicinity at no great depth. Mm)zonite is also exposed 

at the north base of Magdalena Mountain, but its 

extent has not been. determined. 

The relative ages of members of any one group cannot all be determined; for example, the latite porphyry 

and rhyolite porphyry of the first group have not been 

found in contact, nor has the main monzonite stock 

been found in contact with the granite stock, although 

a dike of granite cuts typical monzonite in a minor 

stock. The presence of late granitic facies in the monzonite also suggests that the granite stock -may be 

relatively late. The andesite stock at Granite Mountain cuts the rhyolite porphyry of the first group, and 

the sill-like mass at Stendel Ridge is cut by monzonite; 

but the relt}tions of either andesite body to the main 

period of faulting have not been determined, and it 

therefore is not definitely known whether these intrusive andesites are the youngest members of the first 

group or the oldest members of the second. In the 

third group the dikes of lamprophyre are cut by those 

of white rhyolite, which therefore is the youngest 

igneous rock in the district with the possible exception 

of the felsite tuff. 

LATITE PORPHYRY 

The latite porphyry occurs almost entirely .as a 

much-faulted sill that extends southward from Kelly 

beyond the south limit of the district. It separates 

the Madera limestone from the Abo sandstone or from 

the purple andesite where · the sandstone is locally absent. The small areas surrounded by sandstone near 

the Linchburg tunnel evidently represent the top of 

this sill, and the still smaller areas a little farther 

north incude a short dike that has branched from the 

top of the sill. Along Mistletoe Gulch west of the 

sandstone area a small dike has intruded the ov~rlying 

purple andesite, and a little farther west another 

mass that is poorly exposed appears to represent a 

s.econd sill intruded within or at the base of the red 

andesite. A small dike was also found in the southernmost workings of the South Juanita mine. · The main 

sill varies in thickness. Just south of the Mistletoe · 

mill it is only about 30 feet thick, although. its broad 

• 
TERTIARY (?) EFF-USIVE IGNEOUS ROCKS 33 

exposures nearly parallel to its dip give the impression 

of a much greater thickness; a little farther west down 

J\1istletoe Gulch· its thickness exceeds 100 feet, and near 

the south end of the district it apparently exceeds 300 

feet. 

The latite porphyry is greenish gray with local 

darker-gray, purplish, and pinkish colors. ·· Its more 

weathered outcrops are stained brown and are pitted 

from the weathering out of biotite phenocrysts. It has 

a dense groundmass with 10 to 20 percent of phenocrysts, chiefly of plagioclase and biotite. A few microphenocrysts of orthoclase and quartz, rather conspicuous apatite crystals associated with biotite and magnetite, and a few zircon crystals are identifiable in thin 

section. 'I'he plagioclase (albite-oligoclase) is so 

thoroughly replaced by sericite, calcite, and a probable 

clay mineral that its original composition can only 

rarely be determined. The biotite has been bleached 

and is partly replaced by calcite and chlorite impregnated with iron-oxide specks and rutile needles or, in 

some places, with calcite, sericite, and . _chlorite. The 

extremely fine grained groundmass probably consists of 

orthoclase, plagioclase, and quartz, but it is impregnated with calcite, sericite, quart-z, and brown specks 

of iron oxide. 

LATITE DIKES 

Besides the main sill and associated dikes of latite 

porphyry, a few dikes of similar but not identical composition have been noted. · They have not been correlated with any of the larger intrusive masses. Only 

three have been mapped~one in argillite southwest 

of the Sleeper tunnel, one in argillite and gabbro southwest of the Germany mines, and one in the latite on . 

Stendel Ridge. They are greenish gray, fine-grained, 

and porphyritic. Their phenocrysts, which are about 

1 millimeter in length and constitute about 30 percent 

uf the whole, include altered plagioclase and chloritized 

1ninerals. In thin section the plagioclase is considerably replaced by aggregates of sericite, epidote, calcite, 

and chlorite. The original ferromagnesian minerals, 

whose outlines imply hornblende and probably biotite, 

have been entirely changed to chlorite or aggregates 

of chlorite, epidote, calcite, and hematite. The 

groundmass consists of a felty to microgranular mass 

of feldspar prisms and itregular grains 0.1 millimeter 

long, small irregular elongate grains of chlorite, and 

interstitial quartz. Quartz also forms aggregates that 

are clearly secondary. Hematite, apatite, and zircon 

are the minor minerals. 

RHYOLITE PORPHYRY 

TYPICAL FACIES 

The rhyolite porphyry, called granite porphyry by 

Gordon,47 is the most widely distributed of the Tertiary 

( ? ) formations in the district. It is present at inter4'1' Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., ·The ore deposits of New Mexico: U. S. Geol. Survey Prof. Paper 68, p. 248, 1910. 

vn-ls along a broken belt of northm;ly trend on the west 

foothills of the main range and the upper slopes of 

Granite Mountain and continues at least 2 miles farther 

north. Most of ·its exposures are probably parts of 

one originally continuous sill-like mass, which lies between the ·upper latite and the banded rhyolite, but the 

smaller exposures south of Kelly include a dike and a · 

sill-like mass in pink rhyolite. Identical rhyolite 

porphyry also occurs extensively in the Lemitar Mountajns about 12 miles to the east. A magnetic variety 

caps three conical summits on Stendel Ridge, two at 

ihe southeast end and one at the northwest end. Because of their magnetic properties, which may interfere with surveying, and because of their alteration, 

which has obscured their identity, these three masses 

are separately indicated on the mrup and will be describ~d separately after the description of the normal 

rhyolite. 

The sill-like character of the main mass is best shown 

around North. Camp and on Stendel Ridge. Near 

North Camp the top of the . sill cuts across the flow 

structure of the overlying banded rhyolites at very small 

angles, although the sill has a gentle westerly dip similar 

to that of the flow. Its base is concealed by faults and 

_ alluvium at North Camp but is approximately indicated 

by the small outcrop of underlying latite in the first 

gulch south of North Camp. On Stendel Ridge the 

base cuts across the platy layers of the underlying.latite 

tuff at small angles, although the contact is not clearly 

defined. On Granite Mountain, which has apparently 

derived its name erroneously from the rhyolite porphyry, the relations are very obscure. The rough 

banding there even suggests an effusive origin, although 

the poorly defined sheeted structure accords with a silllike form. There is no sharp line of demarcation here 

between the rhyolite porphyry and the upper latite, as 

the occurrence of quartz in the upper part of the upper 

latite gives an apparent gradational effect. The structural position of the rhyolite porphiry, however, between the latite and the banded rhyolite that is just 

west of Granite Mountain is the s~me as it is farther 

south, and adequate exposures would probably prove its 

intrusive character. 

The rhyolite porphyry sill has a minimum thickness 

of about 400 feet at the North Camp, 800 feet on Stendel . 

Ridge, and about 1,400 feet on Granite Mountain~ but 

at no place is the full thickness exposed. 

The rhyolite porphyry is purplish red on the whole, 

but fresh va:rleties with a glassy to microcrystalline 

groundmass are deep purple to blue. Where it is hy-

-drothermally altered its weathered surfaces are gray 

and pitted and irregularly stained by iron oxide. Its 

groundmass is dense or microgranular, and phenocrysts 

of plagioclase, orthoclase, quartz, and biotite constitute 

30 or 40 percent of it. Abundant large ·phenocrysts of 

clear to smoky quartz as much as 3 millimeters in diameter distinguish this rock from all others of the dis-
34 MAGDALENA MINING DISTRICT, NEW MEXICO 

trict. Pink orthocla13e, though variable in quantity, is 

the dominant feldspar, and with white to gray plagioclase it forms crystals up to 5 millimeters in length. 

Biotite, though subordinate, is conspicuous, especially 

just north of the railroad, where it occurs in abundant 

well-formed six-sided plates, which have weathered to 

a bronze color. The rhyolite porphyry contains many 

fragments of dark-purple, dense rock that are thought 

to represent an early, quickly chilled variety of the 

same intrusive mass. 

In thin section the phenocrysts are all appreciably 

resorbed (pl. 12, B). Thin shreds of biotite are largely 

replaced by dustlike aggregates of hematite, and the 

larger biotite grains are fringed with hematite which 

·in the more altered grains is accompanied by chlorite, 

quartz, and rarely muscovite. The oligoclase-andesine 

is most commonly unaltered, but in places it is largely 

replaced by albite and sericite. The orthoclase, which 

is somewhat microperthitic, is little altered. The 

groundmass is microfelsitic to microgranular and in 

places has a faint flow structure. It consists essentially 

of untwinned :feldspar, probably orthoclase, and quartz 

and in the altered facies may be considerably impregnated by calcite, which is scarce in the phenocrysts. 

Secondary quartz forms small aggregates in the groundmass of the more altered varieties. The minor accessories are magnetite, apatite, titanite, and zircon. 

According to Gordon 48 "a partial analysis of this 

rock was made in the laboratory of the Survey by 

George Steiger, with the following results: Si02 , 69.32; 

CaO, 0.53; N a20, 2.45; K 20, 5.54." The rock is rather 

typical of rhyolite, although the ratio of potash to soda 

is a little higher than in the average rhyolite. 

MAGNETIC FACIES 

The three masses of rhyolite porphyry that cap summits on Stendel Ridge largely resemble the neighboring rhyolite porphyry, but rock that more closely resembles monzonite is intimately associated with them. 

They differ from typical rhyolite porphyry or monzonite in their ability to deflect a compass needle. Compass 

readings made from these summits and checked by foresights and backsights were from 6° to 10° too far to 

the east. Fragments on the surfaces of the summits 

commonly have a polarity, one end attracting and the 

other repelling the compass needle. Notwithstanding 

this magnetic property, there is nothing in the mineral 

composition of the rock to account for it, and it may be 

attributable to some local abnormality in the earth's 

magnetic lines. Some fragments on these summits, 

however, are not magnetic but resemble the rhyolite 

poryhyry and feldspathic and porphyritic facies of 

monzonite so closely that near the northwest end of 

Stendel Ridge,. where these rocks adjoin the magnetic 

rock, only arbitrary boundaries can be drawn. At sev48 Lindgren, Waldemar, Graton, t. C., and Gordon, C. H., The ore 

deposits of New Mexico: U. S. Geol. Survey Prof. Paper 68, p. 248, 1910. 

eral places typical monzonite and magnetic porphyry 

seem to grade texturally and mineralogically into each 

other, although their exact relations are obscured by 

debris. 

The two masses of magnetic cap rock at the southeast end of Stendel Ridge have striking resemblances, 

and the westerly slope of their lower contacts prompts 

the suggestion that they are isolated remnants of the 

rhyolite porphyry sill that has been somewhat invaded 

by dikelets of feldspathic monzonite porphyry. The 

underlying monzonite has a fine-grained or chilled 

facies at its contact with the cap rock and is therefore 

regarded as the younger of the two. Both the monzonite and the cap rock contain dikelets and irregular 

"patches" of feldspathic monzonite or monzonite porphyry, but structural details are obscured by debris. 

If the magnetic cap rock is tentatively correlated with 

the rhyolite porphyry, the main mass of monzonite may 

be regarded as having been intruded along or parallel 

to the base of the sill; but the contact of the two 

magnetic masses with members of the upper latite 

is too steep to indicate a sill-like relation, and the mass 

is so far east of the main sill of rhyolite porphyry 

that such a correlation would require an offset of 

800 to 1,000 feet along a fault that was later obliterated by the intruding monzonite. Such an interpretation, though obviously very speculative, is consistent 

with structural evidence as a whole, which indicates 

that a former major transverse fault zone crossed the 

area now occupied by the monzonite. Little or no 

faulting would be required to account for the rhyolitic 

facies of the magnetic rock at the north end of the 

ridge. 

From what we know both of local evidence and of 

the processes involved in the intrusion of the mon_ 

zonitic stocks of the district, we interpret the origin 

of the magnetic cap rock as follows : The rhyolite porphyry was first cut by the monzonite stock. Late in-

~rusions and emanations from the stock formed feldspathic dikelets and impregnated both rocks near their 

mutual contact with monzonitic material, so that the 

original contact in most places was obscured if not 

destroyed. Several facies without clear-cut relations 

were formed that range from the original normal rocks 

to such uncommon extremes as feldspathic quartz monzonite porphyry and a porphyritic granophyre containing plagioclase phenocrysts. 

In appearance the. magnetic rock is much like the rhyolite porphyry except that large quartz grains are less 

conspicuous. It ranges in' color from a light gray, which 

is the more common, to a dark bluish gray. It is distinctly porphyritic, with a dense microgranular groundmass; but in places it is so crowded with crystals that 

it appears granular. This rather typical facies grades 

into a less porphyritic rock and, apparently at least, 

into nonporphyritic monzonite. White to gray plagio-
r.rER'.I'IARY (?) EFFUSIVE IGNEOUS ROCKS 35 

clase, pink orthoclase, thinly scattered quartz, a few 

grains of bronze-colored mica, and specks of a black 

mineral can be recognized. Dense, dark-purple inclusions similar to those in the rhyolite porphyry are 

common in some places. 

The magnetic rock varies considerably both in composition and texture, as seen under the microscope. 

In general it is distinctly porphyritic (pl. 12, 0). 

Some thin sections show the phenocrysts to b~ so 

abundant that the groundmass is merely interstitial, 

whereas others show them to form less than 50 percent 

of the rock. The phenocrysts in general show con- · 

siderable resorption. Those in specimens collected 

at the south end of Stendel Ridge consist of calcic 

andesine, orthoclase, augite, and biotite, with a little 

irregularly scattered quartz. Andesine in irregular 

and rectangular grains up to 2 millimeters long predominates over orthoclase, and in one thin section no 

orthoclase was noted. The plagioclase phenocrysts in 

the lower part of the formation are commonly 

zoned; in many thin sections the plagioclase is bordered by narrow rims of orthoclase (pl. 12, D) and in 

part irregularly replaced by orthoclase. Orthoclase 

forms irregular grains up to 3 millimeters in length. 

It is commonly clouded along its borders and cleavage 

cracks, but its cores are clear, suggesting that the 

clouding is a secondary feature. Quartz phenocrysts 

are rare. 

The .ferromagnesian minerals vary in amount and 

kind. They comprise augite, biotite, and locally a 

little hornblende. No hypersthene was found. Thin 

sections from the upper part of the formation have 

only a few scattered flakes of partly to completely resorbed biotite with very few or no augite phenocrysts. 

Fresh, pale-brown, fine-grained biotite is locally present in patches of micropegmatite and is believed to be 

later than the other ferromagnesian' minerals. . Lower 

in the formation augite is the dominant ferromagnesian mineral, and it occurs both as phenocrysts up 

to 0.7 millimeter in length and as microlites in the 

groundmass. Biotite, where partly resorbed, is marked 

by a border of segregated magnetite and augite microlites (pl. 13, 0) or, where completely resorbed, by 

pseudomorphous areas of magnetite and fine-grained 

augite, with untwinned feldspar. The microlites, besides being especially bunched along the borders of 

partly resorbed biotite flakes where they are associated 

with fine-grained magnetite, are scattered throughout 

the groundmass. Whether or not all this .granular 

augite in the groundmass is a result of the resorption 

of· biotite, as is believed of the augite microlites in the · 

groundmass of some andesites,49 is not certain; but 

there can be little question concerning that bordering 

and replacing biotite. Primary hornblende is s~a,rce 

49 Washington, H. S., The magmatic alteration of hornblende and biotite: Jour. Geology, vol. 4, pp. 270-276, 1896. 

and is very pale brown. Magnetite, apatite, and zircon, which are the accessory minerals, occur in typical 

crystals. In one ·thin section from the southernmost 

exposure what appears to be a secondary green to 

orange pleochroic serpentine is sparingly scattered in 

small irregular grains and shreds and pseudomorphs 

through the rock, and some of it partly surrounds 

augite. 

The groundmass is microgranular and consists 

chiefly of orthoclase with smaller amounts of quartz 

and the augite microlites already mentioned. In some 

thin sections quartz is very scarce an1d in others is 

present only in small amounts of micropegmatite. 

The magnetic rhyolite porphyry from the north 

summit of Stendel Ridge is dominantly a feldspathic 

facies. It consists -chiefly of cloudy microperthite 

phenocrysts with some oligoclase and an interstitial 

groundmass that is partly micrographic. Calcite and 

chlorite are relatively abund'ant in the interstitial 

material. Aggregates of finely graimlar magnetite 

with some chlorite suggests resorbed and altered biotite. The feldspar phenocrysts are slightly sericitized. 

Th!s rock approaches the Tertiary ( ~) granite in 

mineralogical composition and texture. 

HORNBLENDE ANDESITE 

The hornblende andesite is found on Stendel Ridge, 

where it forms three small outcrops-one' a small oval 

mass that is apparently intrusive into the rhyolite 

porphyry, another a sill intruded into latite tuff, and 

the third a small triangular block with obscure relations but evidently younger than the latite flow and 

older than the monzonite. The third exposure- may 

be a part of the sill; if so, it was detached and lifted 

during the intrusion of the moRzonite. 

The hornblende andesite is dark purple with a dense 

to glassy groundmass in which small phenocrysts of 

white to colorless plagioclase and hornblende pseudomorphs are thickly distributed (pl. 13, B). The plagioclase (andesine) crystals-in .general less than 1 

millimeter and rarely as much as 2 millimeters longare only slightly sericitized. The brown hornblende 

crystals, as much as 3 millimeters in length, have been 

largely replaced by aggregates of colorless amphibole, 

sericite, quartz, calcite, and chlorite, with rims of 

fine-grained iron oxide. Apatite, most of which is 

included in the replaced hornblende, and ~agnetite 

are t1he only minor accessory minerals. The groundmass, which shows distinct flow structure, consists of 

small plagioclase laths in a glassy base, veined and 

spotted with gray cryptocrystalline material. It is 

free from alteration, excepting S<?me Scattered calcite. 

AUGITE ANDESITE 

Augite andesite is present on the eastern slope of 

Stendel Ridge, the crest of Granite Mountain, and the 
36 MAGDALENA MINING DISrrRICT, NEW MEXICO 

low hills north of the district. The largest mass on 

Stendel Ridge has an irregular sill-like form and 

covers about 15 acres. A few small dikes are in line 

with its tapering south end. It. cuts the upper latite 

tuff and is cut by a dike of fine-grained monzonite, 

but its relations to the adjacent magnetic rhyolite 

porphyry are obscure. The mass orr Granite Mountain 

is small stock or plug with a surface area of about 30 

acres. It is clearly intrusive into the rhyolite porphyry and upper latlte. None of these masses are in 

contact with major faults. It is not known, therefore, 

whether they are more closely related in time to the 

effusive rocks that preceded the major period of faulting or to the monzonite and granite stocks that 

followed it. 

The augite andesite is dark gray where least altered 

and greenish gray elsewhere and has a fine-grained 

to microgran~lar porphyritic texture. The phenocrysts, which are as much as 1 millimeter long, are 

white ,plagiOclase -and blaQJr augite and constitute 

from 10 to 20 percent of the rock. 

In thin section (pl. 13, A) the phenocrysts are seen 

to consist of plagioclase (oligoclase-andesine to calcic 

andesine) ' augite, minor amounts of brown hornblende, 

and another ferromagilesian mineral now represented 

by chlorite. Those of plagioclase are partly replaced 

by epidote, calcite, and sericite. Those of augite predominate over plagioclase and are unaltered even 

where the plagioclase and hornblende are altered. 

Brown hornblende, sparingly present, is bordered by 

reaction rims of iron oxide, and many completely resorbed grains are represented by aggregates of iron 

oxide, calcite, and quartz that are pseudomorphous 

after hornblende. Chlorite (penninite ?) that represents another ferromag\nesian mineral whose outlines 

suggest a pyroxene is present in appreciable amounts. 

Some of these grains are bordered by magnetite and 

a few by augite. Microphenocrysts of magnetite and 

apatite are thinly scattered through the groundmass. 

The groundmass is trachytic and consists of twinned 

plagioclase laths intercrystallized with small amounts 

of obscure and irregular grains that are probably 

orthoclase and scattered magnetite grains. It contains 

a sprinkling of epidote, calcite, and sericite, but is 

much less altered than the plagioclase and hornblende 

phenocrysts. · 

MONZONITE GROUP 

Four stocks of monzonitic and granitic rock are 

found within the boundaries of the district. The largest of these is a stock of granite that underlies an area 

of about 2 square miles on the north end of the Magdalena Range. As it is cut by Anchor Canyon, it will be 

called the Anchor Canyon stock. Next in size is the 

stock of typical monzonite north of the Nitt and 

Graphic-Waldo mines, here designated the Nitt stock. 

It underlies a known area of at·least 11-h square miles 

but is partly covered by alluvium and may be continuous with a small stock noFthwest of Stendel Ridge 

as well as with monzonite exposed in the low hills 

south of the town of Magdalena. The stock northwest 

of Stendel Ridge, however, .is conveniently described 

separately because of the diversity of its component 

rocks, which include monzonite and granophyre. The · 

fourth stock is on the southwest side of Granite Mountain .and includes monzonite and granite. There is a 

fifth stock of monzonite and allied rocks about a mile 

northwest of La Jenze Creek beyond the limits of the 

area. 

The last three stocks and part of the Nitt stock 

have a northerly alinement over an area about 5 miles 

long_ and hal:f a mile wide. This relatively long and 

narrow group suggests intrusion from a common .reservoir at favorable places along a structurally weak zone 

which, as will be shown on page 69, is probably a major 

fault zone. 

The Anchor Canyon stock is the exception to this 

zonal distribution of the stocks, but its position, which 

accords with the axis of a broad flexure along the valley 

that separates the Magdalena Range from Granite 

Mountain, implies intrusion along another weak zone. 

The rectangular southeastern part of the Nitt stock 

with its steep and regular northern and southern contacts accords with an ·old transverse fault, which is 

expressed by the discordant relations of both sedimentary and volcanic rocks to the north and south of the 

monzonite; indeed this part of the stock has the outline 

of an unusually thick dike of east-northeast trend. 

These stocks, with the exception of the Anchor Canyon stock, are clearly younger than the rhyolite porphyry and augite andesite and are probably the 

youngest of all the Tertiary ( ? ) igneous rocks except 

the dikes of lamprophyre and white rhyolite, and presumably the felsite tuffs, which may be even younger 

than these dikes. The Anchor Canyon stock is intruded chiefly into pre-Cambrian and Paleozoic forma'" 

tions, and its only contact with the volcanic rocks, at 

the n~rth base of the range, is too obscure to prove 

its intrusive relation. A.s the granite in this stock, 

however, is identical with that of the Granite Mountain 

stock, it is correlated with that stock and is therefore 

inferred to be of probable Tertiary age. 

There is no direct evidence for the closer dating of 

the intrusions. As the Datil formation, which evidently includes at least the older of the local volcanic 

rocks, is tentatively regarded as Tertiary by Winchester,50 and as the major period of faulting intervened between the surface eruptions and the stock 

intrusions, the stocks could be late Tertiary; but sush 

an interpretation cannot be reconciled with the large 

amount of erosion that has taken place subsequent to 

so Winchester, D. E., Geology of Alamosa Creek Valley, Socorro 

County, N. Mex. : U. S. Geol. Survey Bull. 716-A, p. 9, 1920. 
TERTIARY ( ? ) EFFUSIVE IGNEOUS ROCKS 37 

the intrusion ·of the stocks. In the San Juan 51 and 

Front Range 52 regions of Colorado volcanic eruptions, 

closely followed by the intrusion of monzonitic stocks 

and related masses and deposition ol ore, took place in 

both Eocene and Miocene time; and the monzonitic 

stocks at Magdalena could be tentatively assigned to 

either epoch, but until much more is known of the intervening region no attempt to assign a more definite 

age to the stocks is justified. 

The depth of intrusion of the monzonitic stocks can 

be only roughly estimated until more definite information becomes available on the geology and physiographic history of the entire province. The volcanic 

rocks at one time undoubtedly covered the range within 

the district as shown on page 24. According to estimates already presented, the volcanic flows and sills had 

an aggregate thickness of 2,000 · feet or more and fur- . 

nished a cover sufficient to permit the monzonitic rocks 

to cool slowly and develop their gramilar texture. 

TYPICAL FACIES 

The monzonite has an unequal distribution in the 

different stocks. The Nitt stock is composed almost 

entirely of monzonite, but the small stock northwest of 

Stendel Ridge is largely granite and only its eastern 

part is equivalent texturally and mineralogically to the 

monzonite of the Nitt stock. The stock on the west 

side of Granite Mountain is also mostly granitic, with 

a southern margin of monzonite. From this stock and 

also from the northwestern part of the Nitt stock on 

Stendel Ridge apophyses extend from the main mass. 

The apophysis on Stendel Rid~e, however, is gabbroic, 

and the transition into the monzonite of the main stock 

takes place within about 10 feet. 

One characteristic feature of the monzonite is its 

magnetic property, which has permitted the tracing of, 

its contact beneath a cover of alluvium by means of 

a dip needle. W. 0. Hotchkiss, who spent 2' weeks in 

the field with Loughlin in 1916 testing the usefulness 

of the dip needle in the location of ore bodies and in 

geologic mapping, was able to trace the monzonite 

contact underneath the alluvium to the west edge of 

the district and beyond.53 (See pl. 2.) The tracing 

of an apparent apophysis to the south, however, led 

to a small exposure of lamprophyre, which was as magnetic as the monzonite, on the low rhyolite hill half a 

mile west of Kelly. 

The typical color of the Nitt monzonite is medium 

gray, but it becomes darker as the texture becomes finer; 

the fine-grained marginal facies is considerably darker 

and in places has a purplish tint. On weathered surfaces 

51 Burbank, W. S., Revision of geologic structure and stratigraphy in 

the Ouray district of Colorado, and its bearing on ore deposition : Colorado Sci. Soc., vol. 12, No. 6, pp. 184-232, 1930. 

r>2 Lovering, T. S., Geologic history of the Front Range, Colo.: Colorado Sci. Soc., vol. 12, No. 6, pp. 92-109, 1929. · 68 Hotchkiss, W. 0., Magnetic methods for exploration and geologic 

work : Am. Inst. Men. Met. Eng. Trans., vol. 69, p. 41>, 1923. 

the. color is predominantly rusty brown. The rock is 

essentially fine-grained and nonporphyritic, the average 

grain being .less than 1 millimeter in diameter. Light" 

gray glassy feldspar is its chief constituent, but glistening specks of biotite and augite are thickly 

disseminated. The chilled facies, such as is found in 

the apophysis near the north end o:f Stendel Ridge, is 

very fine grained and slightly porphyritic. 

Thin sections of .the typical monzonite (pl. 14, 0) 

show an uneven granular texture. Some of the grains 

are rather well formed but most of them are very 

irregular, interlocking, and without sharply defined 

boundaries. The component minerals are feldspars 

about 75 percent, with plagioclase slightly in excess 

of orthoclase; quartz 2 percent; pyroxenes 14 percent, 

with augite somewhat in exces·s of hypersthene; biotite 7 percent; hornblende 1 percent, magnetite as much 

as 3 percent; and apatite and zircon in minute quantities. Graphic intergrowths of orthoclase and quartz 

with hornblende fibers are present in variable amounts, 

and a few grains of epidote were found in one thin 

section. The most common alteration product is a 

yellow· to green material derived from hypersthene. 

Some of it appears to be merely a discoloration caused 

by oxidation, but some is fibrous and resembles serpentine. Incipient chloritization of biotite and sericitization of the feldspar were also noted in a few sections. 

Plagioclase (andesine) is pre~ent in irregular and 

elongate zoned grains up to 1.5 millimeters in length. 

Most of the grains have been partly and irregularly 

replaced by more sodic plagioclase and thtJs have a 

spotted ·appearance and shadowy extinction. The 

transitional ·contacts with orthoclase largely account 

for the confusing appearance illustrated on plate 14, 0. 

Orthoclase most commonly forms irregular grains up 

to 0.75 millimeter in diameter and is poikilitic but is, 

with quartz, in part interstitial to the other minerals. 

Augite forms ·irregular to rectangular grains 0.75 

millimeter in diameter, a few of which are twinned. 

It is mostly fresh. Hypersthene likewise forms rect-. 

angular to irregular . grains, which are in general 

.somewhat smaller than those of augite. Schiller structure in fresh .grains is common but not pronounced. 

The augite is essentially unaltered, but incipient alteration has begun along cleavage cracks in a few grains. 

. The pyroxenes are commonly associated with biotite, 

hornblende, and magnetite, as well as with apatite 

and zircon, and form clusters with them. Some pyroxene grains are micrographically intergrown ,with 

magnetite. (Pl. 14, .A..) 

The graphic intergrowths of orthoclase and quartz 

are believed to be secondary and comparable to the 

typical myrmekitic intergrowth of plagioclase and 

vermicular quartz as described by Seder holm. 54 Many 

w Sederholm, J J., On synantetic minerals and related phenomena: 

Com. Geol. Finlande Bull., No. 48, pp. 1-148, 1916. 
38 MAGDALEN A MINING DISfrRICT, NEW MEXICO 

orthoclase grains are entirely free from vermicular 

quart~ (pl. 14, B), whereas others have graphic cores, 

and still others have graphic zones without definite 

arrangement. Again, an irregular zone of the intergrowth may cross several adjoining orthoclase grains 

irrespective of boundaries. These relations as a whole 

clearly indicate that the intergrowths were developed 

later than the original crystals, and they are therefore 

believed to have resulted from a selective replacement 

of the orthoclase by vermicular quartz. Simple orthoclase grains adjoining graphic grains were probably 

not replaced because of unfavorable orientation. Associated with the graphic intergrowths and not found 

elsewhere are groups of d.elicate green amphibole crystals (pis. 15 A, B), which are exceedingly numerous in 

some places and very scarce in others. They are most 

commonly oriented in one or two directions, but, some 

grains lie at random. Their arrangement together 

with their association with the intergrowths of orthoclase and quartz show them also to be secondary. 

OTHER FACIES 

There are many variations of the monzonite, especially along the margins of the stocks. The fine-grained 

chilled rock in an apophysis near the northwest end 

of Stendel Ridge is finely porphyritic, with phenocrysts of sodic · labradorite, augite, and hypersthene 

as much as 1 millim)eter long in a mic.Togranular 

groundmass. Its composition approaches that of 

norite rather than monzonite. The labradorite is 

strongly zoned and commonly bordered by a narrow 

fringe of orthoclase. The cores of some grains are 

full of aug'ite granules. Hornblende is· absent, and 

biotite, which forms an essential constituent in the 

typical monzonite, forms only narrow fringes around 

a few magnetite and pyroxene grains. It is relatively 

pale and may be secondary. 

The groundmass of this apophysis consists of irregular granules of augite, plagioclase, and orthoclase. 

·Those of pyroxene especially range in size from mere 

~pecks · to well-defined grains and grade into the 

smaller phenocrysts (pl. 16, A). Quartz occurs in 

very small amounts interstitial to the feldspar, and 

magnetite and a . few apatite grains form 'the minor 

accessory minerals. 

Aboqt 1,000 feet north of the Graphic tunnel, a finegrained noritic rock forms a narrow border facies 

between the typical monzonite and a large inclusion 

of pre-Cambrian gabbro (pl. 2). The contact is marked 

by a banded rock (pl. 15, 0) composed of thin layers 

and streaks of the relatively coarse grained preCambrian rock separated by lenses of the intrusive 

rock. The pre-Cambrian gabbro, whose grains are as 

much as 0.75 millimeter in diall}eter, consists essentially of . labradorite and . of pale-green hornblende 

whose borders have · partly changed to augite, evidently owing to the heat of the invading rock. The , 

norite, whose grains are irregular and in general less 

than 0.1 millimeter in diameter, consists essentially of 

labradorite, augite, and hypersthene (pl. 15, D), with 

a few grains of biotite, magnetite, and zircon. The 

augite and hypersthene are more abundant than in 

the norite apophysis on Stendel Ridge and n1ay h~ve 

been derived in part by reaction between the intrusive 

magma and the hornblende of the pre-Cambrian gabbro. Such a reaction, as suggested by Bowen,55 should 

cause deposition of the "heat equivalent of the member 

of the series with which the liquid is saturated.'' 

Between the monzonite and gran~phyre in, the stock 

just west of the banded rhyolite in the hills northwest 

of Stendel Ridge, there is a medium-grained rock 

richer in orthoclase than the monzonite. The orthoclase grains are as much as 2 millimeters in diameter 

and are poikilitic (pl. 16, Oh enolosing andesine, 

pyroxenes, and accessory minerals. Hypersthene and 

augite here also are the dominant ferromagnesian 

minerals. Biotite, in part resorbed and in part of 

pale-brown color, forms only irregular small shreds 

and fringes artJund magnetite and the pyroxenes. 

Apatite is much more common than in the typical 

monzonite. Quartz in this facies occurs only in interstitial micrographic intergrowths with clouded orthoclase and some pale·-yellow to orange biotite. 1 

About 200 feet west of the outcrop just described the 

rock is more feldspathic and quartzose, but it is still 

medium-grained. Orthoclase and andesine form its 

bulk, but the orthoclase is not poikilitic. It is much 

clouded, except in the cores of some of the larger grains. 

Augite is the common, ferromagnesian mineral, and · 

hypersthene is rare. A very pale brown to yellow 

hornblende, which is green where altered, is present in 

minor amounts. Biotite, which is also present in minor 

amounts, is of two varieties. One consists of large 

yellow to deep reddi~h-brown flakes, which are largely 

resorbed and are now marked by a few remnants surrounded by fine-grained aggregates of magnetite, 

augite, and untwinned plagioclase·. It is associated 

with apatite and altered pyroxene (probably· hypersthene) and · is evidently primary. The other variety, 

probably later, is orange to pale yellow, fonns only 

small irregular shreds, and occurs with quartz in the 

interstitial micrographic intergrowths, which are believed to . be secondary. A striking fea~ure of this 

facies of monzonite is the relatively large content 

of graphically intergrown orthoclase and quartz 

(pl. 16, B). 

Biotite-hornblende monzonite with poikilitic ortho.-

elase is also exposed about a mile northeast of the 

Graphic tunnel along the Sleeper tunnel road. Biotite, 

in crystals as much as 2 millimeters ·in diameter, is 

115 Bowen, N. L., The evolution ef igneous rocks, Princeton University 

Press, p. 221, 1928. 
TE'RTIARY (?) INTRUSIVE IGNEOUS ROCKS 39 

conspicuous in specimens, but in thin section pale-green 

hornblende, slightly altered to chlorite, is the dominant 

ferromagnesian mineral. Augite is accessory only and 

with some andesine is enclosed in the orthoclase. 

Epidote, .a few grains of ·titanite, and allanite are 

probably secondary minerals. 

A more salic facies, and one very similar to the 

Tertiary ( ? ) granite, is represented by an apophysis 

cutting argillite northeast of Oak Spring. It c~nsists 

essentially of orthoclase, andesine, quartz, and biotite. 

Epidote, chlorite, and allanite are the secondary minerals. Dikelets that are still more feldspathic cut the 

monzonite near its contact north of-Oak Spring and 

on the south end of Stendel Ridge. The plagioclase in 

these · dikelets is albite-oligoclase. Grains of biotite, 

hornblende and augite are scarce; but chlorite and 

epidote are common. Epidote, with large irregular 

grains of titanite up to 1 millimeter long, is even more 

common in a salic facies exposed in a small prospect on 

the northern spur of the monzonite' east of Hardscrabble Valley. In one thin section a late bluish-green 

fibrous hornblende was found replacing epidote (pl. 16, 

D). The epidote is apparently a late product of 

crystallization and not an alteration product of 

feldspar, but the fibrous hornblende is probably 

hydrothermal in origin. 

The more conspicuous development of orthoclase and 

biotite and especially of epidote and titanite near the 

contact and in dikelets in the monzonite is believed to 

imply concentration of salic and volatile constituents, 

a lowering of temperature in the monzonite mass, and 

a transition from strictly igneous to hydrothermal 

conditions. 

CHEMICAL COMPOSITION AND CLASSIFICATION 

The chemical analysis in column 1 of the following 

table represents the typical monzonite taken about 3,500 

feet southeast of Hardscrabble Camp. A partial analy-

~is of the same rock is given' in column 2, and the 

average of 12 monzonites is given in column 3. 

A comparison of the typical monzonite of the district 

with the average monzonite shows a close agreement in 

most oxides excepting the alumina and to a smaller 

degree the lime, which are below the average, and · 

reflect. the more sodic character of the plagioclase and 

the relatively high pyroxene content. The total 

amounts of i~on oxides in each rock are almost identical, but the local monzonite is richer in ferrous iron 

· and lower in ferric than the average monzonite. The 

water, in view of · the practical absence of secondary 

minerals, is probably largely present in biotite and 

hornblende; the titanium may be present chiefly in the 

magnetite, and to a small extent in biotite and pyroxenes; sulphur may be present in negligible quantities 

of finely dispersed sulphides; and barium· is probably 

a constituent of the feldspar. 

Si02---- - Ah0a----- Fe20a- _-- FeO ___ -- MgQ ____ _ 

CaO ___ _ _ 

Na20 - _- _ 

K20 - _- - - H20 - __ _ 

H20+ - -- Ti02- __ - -

co2------ P2o5----- F ____ ___ _ s ______ _ _ V20 a--- -- MnO __ __ _ BaO __ _ / __ Sro __ ___ _ 

Analyses of monzonites 

Analyses 

2 3 

57. 06 57. 67 55. 25 . 14. 60 16. 53 

2.46 3. 03 

5. 02 4. 37 

4. 21 4. 20 

6. 26 5. 89 _7. 19 

3. 45 a 47 a 48 

4. 04 3. 54 4. 11 Trace? _ _ _ _ _ _ _ _ _____ _ 

. 53 ----- -- . 66 

1. 59 - - - - - - - . 60 Trace? ________ _____ _ 

. 60 - - - - - - - . 43 Trace? _ _ _ _ _ _ _ _ _____ _ 

. 03 - - - - - - - - - - - - - - . 06 - - - - - - - - - - - - - - None ___ ___ _ . 15 

. 20 - - - - - - - - - - - - - - Trace? _ _ _ _ _ _ _ _ ____ _ _ 

100. 11 100 

_ Mode of No.1 

2. 5} 33 75. 5 

40 

Quartz ___ __ _ _ 

Orthoclase ___ _ Plagioclase __ _ 

14 } 7 24. 5 

3. 5 

Pyroxenes ___ _ Biotite ___ ___ _ 

Accessory __ _ .., 

SymboL . II.5.3.3 

shonose. 

100. 0 

Sho1. Monzonite, 3,500 feet southeast of Hardscrabble Camp, 

Magdalena district, New Mexico; J. G. Fairchild, analyst. 

2. Partial analysis of monzonite, northeast of Graphic tun- nel, Magdalena district, New Mexico; George Steiger, analyst: 

U. S. Geol. Survey Prof. Paper 68, pp. 39 and 247, 1910. 

3. Average analysis of monzonite; Daly, R. A., Igneous 

rocks and their origin, p. 23, New York, 1914. 

TERTIARY (?) GRANITE 

Distribution and occurrence.-The Tertiary (?) granite is exposed in two stocks and covers a larger area 

than the monzonite. Similar rock, not indicated on 

plat13 2 (see above), occurs just north and northeast 

of Oak Spring as a local differentiate of monzonite 

and .in dikelets that cut the pre-Cambrian formations. 

On the north end of Stendel Ridge a dike of the granite 

cuts typical monzonite. The larger of the stocks fornis 

the north end of the ~1:agdalena Range east and west 

of Anchor Canyon. Its northern limit is concealed 

beneath alluvium, but the presence of such contact" 

metamorphic minerals as magnetite, garnet, and serpentine on two prospect dumps in the upper part of the 

Sandia formation north of the railroad suggests that 

granite or monzonite may extend nearly _that far north. 

Granite also constitutes most. of the stock on the west 

side of Granite Mountain. There it is bordered on the 

SOl!theast and south by monzonite and on the northWest by hybrid rock that simulates granophyre. 

The Tertiary ( ? ) granite, as well as the monzonite 

and granophyre, weathers characteristically into subdued slopes covered by rounded boulders in marked 

-contrast to the pre-Cambrian granite, which weathers 

into angular cliffs bordered by angular fragments. 

This contrast is shown on plate 17. In Anchor Canyon 

the Tertiary ( ? ) granite has disintegrated into soil 

from 7 to 10 feet deep, whereas little or no residual 

soil covers the surrounding pre-Cambrian· granite. The 

tendency of the Tertiary ( ? ) granite in this vicinity 
40 MAGDALENA MINING Disri'RICT, NEW MEXICO 

to be eroded into valleys rnay at first give the impression that it represents a coarse-grained facies of the 

pre-Cambrian granite and grades upw~rd into the 

finer-grained facies; but close examination reveals the 

Tertiary .( ~) granite in sharp contact with the 

pre-Cambrian granite. 

Lithology.-The Tertiary ( n granite is light pinkish 

gray but some of its more weathered surfaces are brown. 

In general it is medium-grained and somewhat porphyritic (pl. 18, A), with the scattered phenocrysts of 

white to glassy plagioclase rarely more than 5 milli-

. meters long in a groundmass of pink orthoclase, quartz, 

and biotite, whose average diameter of grain is between 

1 and 2 millimeters. A somewhat finer-grained and 

practically nonporphyritic facies is found along the 

trail to the Hardscrabble mine, but its distribution relative to the coarser-grained facies is uncertain. Its 

average grain lS .about 1 millimeter in diameter. 

The more distinct phenocrysts consist of plagioclase 

and amount to only 1 percent or less of the rock, but 

aggregates of opalescent white plagioclase with some 

orthoclase accentuate the porphyritic appearance, 

especially where weathered. Plagioclase is relatively 

resistant to weathering, for unaltered opalescent plagioclase is a characteristic constituent even in the thoroughly disintegrated rock. Quartz is not conspicuous 

but appears rather abundant under close inspection. 

Brown specks of titanite are common. 

In thin section the thinly scattered plagioclase phenocrysts are embedded in a groundmass consisting largely 

of ·irregular feldspar grains and interstitial quartz (pl. 

18, 0). The minerals, in order . of abundance, are 

microperthitic orthoclase 50 to 65 percent, plagioclase 

15 to 20 percent, quartz 15 to 20 percent, biotite about 

5 percent, with smaller amounts of hornblende. The 

ratio of orthoclase to plagioclase classifies the rock as 

granite rather than quartz monzonite, as it was called 

by Gordon.56 The minor accessory minerals are titanite, magnetite, apatite, and zircon. Secondary minerals 

are epidote, sericite, chlorite, and calcite. 

The microperthitic orthoclase forms irregular grains 

some of which are 1.5 millimeters or more in length but 

most of which are less than 1 millimeter. Some, in 

. micrographic intergrowth with quartz, is interstitial 

among the larger mineral grains. This orthoclase is 

characteristically clouded by minute dustlike inclusions 

which in some thin sections give it a brownish-gray 

appearance in transmitted light. In the larger grains 

the inclusions are found at the borders or next to 

cleavage cracks, teaving the core clear, but illj the smaller 

grains they are evenly distributed throughout. Some 

of the inclusions have a higher index of refraction than 

the feldspar and may be sericite, and judging from the 

pink color of the feldspar some must be hematite; 

66 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore depos1ts of New Mexico: U. S. Geol. Survey Prof. Paper 68, pp 36-39 and 

247, 1910. 

others have a lower refractive index and are probably 

liquid- or gas-filled caviti~s. 

The plagioclase is slightly sericitized oligoclase and 

forms both phenocrysts ai).d irregular grains in the 

groundmass. Disseminated sericite in the p!agioclase, 

though commonly scant, is more conspicuous than in 

the orthoclase, and in a few grains only is it sufficient 

to obscure the identity of the original plagioclase. 

The sericite is locally accompanied by a pale-brown 

mineral with low index of refraction and moderate 

birefringence, which is evidently of the montmorillonite-beidellite group. 

Quartz forms irregular grains mostly less than 1 

millin1eter in diameter. It is almost entirely interstitial, forming continuous aggregates that closely 

interlock with irregular orthoclase grains and are in 

part graphically intergrown with them. Some grains 

appear to be earlier than at least a part of the orthoclase. 

Biotite and hornblende tend to form clusters with 

the accessory minerals. Biotite is the more abundant, 

constituting 3 to 5 percent of the rock. It shows pale · 

yellow to dark reddish-brown pleochroism, and some 

grains are altered to chlorite on the edges or next to 

cleavage cracksA Hornblende forms a few scattered 

grains up to 1.25 millimeters long, but it varies in 

amount and may locally exceed biotite. Its derivation 

from original augite is indicated by an occasional core 

of augite. · Magnetite in irregular grains up to 0.5 

millimeter in diameter is associated with the dark 

minerals~ Titanite in wedge-shap~d and irregular 

grains is relatively abundant. It is most commonly 

associated with biotite and hornblende and tends . to 

form .partial borders around magnetite grains. Apatite in its usual hexagonal crystals, and in shapeless 

grains, is also common. Zircon is relatively rare. 

Secondary minerals, other than sericite, montmorillonite-beidellite, and chlorite, are calcite and epidote. 

Calcite is rare, and the few irregular grains present are 

interstitial. Epidote is present in variable amounts. 

It is very abundant in some thin sections and rare in 

others, but in only one section is it entirely absent. 

Allani~e was found in one thin section . 

A thin section of the nonporphyritic facies of the 

granite shows that facies to consist mainly of orthoclase (70 to 75 percent) and quartz (20 to 25 percent). 

Plagioclase and ferromagnesian minerals are accessory, . 

but in' other respects this rock is siniilar to the typical 

porphyritic facies. 

APLITE DIKES 

Besides the small dikes and patches of granitic 

aplite in the Tertiary ( ~) granite west of Anchor 

Canyon, a few dikes have been noted in the monzonite, 

and one, 2,000 feet north of the Graphic tunnel, has 

been mapped. The dikes attain a maximum length of 

about 400 feet, but most of them are only about 20 to 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 10 

A. PHOTOMICROGRAPH OF PURPLE ANDESITE, SHOWING MESH OF HEMATITE, WHICH PROBABLY REPRESENTS RESORBED 

AND OXIDIZED AMPHIBOLE NEEDLES. 

The mesh does not penetrate the phenocrysts. Plain li ght. 

11. PHOTOMICROGRAPH OF PURPLE ANDESITE, SHOWING HEMATITE 

PSEUDOMORPHS AFTER AMPHIBOLE. 

A large amount of finely flivided hematite is also preRent in the grounflmass. 

Plain light. 

C. RED ANDESITE WITH GROUNDMASS THOROUGHLY OllSC'uRED 

BY RED IRON OXIDE. 

White lath-shaped crystals are feldspar. The smaller round lo irregular areas are 

vesicles filled with chalcedony; the larger ones contain calcite and mosaic quartz. Plain light. 
GEOLOGICAL SURVEY PH.OFESSIONAL PAPER 200 PLATE 11 

A. UPPER ANDESITE, SHOWING RELATIVELY LARGE PHENOCRYSTS O.F PLAGIOCLASE AND SMALLER PHENOCRYSTS O.F .FORMER 

HYPERSTHENE BORDERED BY HEMATlJ'E ANp INTERNALLY REPLACED BY WHAT APPEARS TO BE A CLAY MINERAL. 

Crossed nicols. 

IJ. HED ANDESITE, SHOWING GROUNDMASS OBSCURED BY RED IRON 

OXIDE. 

The large irregular areas are vesicles filled with calcite (gray) and lined with chalce- dony (clear)_ Small white hexagonal areas in the calcite are cross sections of quartz 

crystals projecting from the chalcedony borders. Plain light. 

C. PLAGIOCLASE PHENOCRYSTS AND MICROGEODES O.F A ZEOUTE 

WITH OPAL OR CHALCEDONY CORE IN GLASSY PORTION O.F UPPER 

ANDESITE. 

Considerable red iron oxide obscures the groundmass. Plain light. 
GEOLOGICAL SURVEY 

A. VITROPHYRE IN UPPER ANDESITE, SHOWING CELADONITE 

AS VERMICULATE TRACES AND RINGLETS AROUND ZEOLITE 

BI.EBS. 

Hypersthene also h'ls been partly replaced by celadonite. Plain light. 

C. PHOTOMICROGRAPH OF TYPICAL MAGNETIC RHYOLITE 

PORPHYRY. 

Phenocrysts consist of more or less rounded plagioclase and orthoclase grains 

with an occasional magnetite grain, embedded in a microgranular groundmass with some micropegmatite. Crossed nicols. 

PROFESSIONAL PAPER. 200 PLA'l'E 12 

B. TYPICAL RHYOLITE PORPHYRY, SHOWING PARTLY RE· 

SORBED PHENOCRYSTS OF QUARTZ AND FELDSPAR. 

The small amount of biotite present is also partly resorbed and is 

partly replace by hematite. Crossed nicols. 

D. PHOTOMICROGRAPH OF MAGNETIC PORPHYRY, SHOWING CO· 

RONAS OF ORTHOCLASE AROUND PLAGIOCLASE PHENOCRYSTS. 

Groundmass is microgranular. Crossed nicols. 
GEOLOGICAL SUPVEY 

A. INTRUSIVE AUGITE ANDESITE WITH PHENOCRYSTS OF 

ALTERED PLAGIOCLASE AND AUGITE. 

The groundmass contains considerable hematite. Plain light. 

PHOFESSlONAL PAPER 200 PLA'l'E 13 

B. TYPICAL HORNBLENDE ANDESITE. 

Hornblende phenocrysts are numerous but have been largely replaced by 

aggregates of colorless amphibole, sericite, quartz, calcite, and chlorite, and 

rims of fine-grained iron oxide. Plagioclase phenocrysts are andesine. 

The groundmass is glassy to cryptocrystalline and contains dark glassy 

blotches veined and enclosed by gray cryptocrystalline material. Plain light. 

C. PHOTOMICROGRAPH OF MAGNETIC PORPHYRY FROM LOWER PART OF THE FORMATION, SHOWING PARTLY RESORBED BIOTITE 

PHENOCRYSTS WHICH ARE SURROUNDED BY AUGITE MICROLITES; THE AUGITE PHENOCRYSTS ARE UNAFFECTED. 

The feldspar phenocrysts have also been partly resorbed. Plain light. 
GEOLOGICAL SUFVE Y 

A. MICROGHAPHIC INTERGROWTH OF AUGITE AND MAGNETITE 

WITH A BORDEH OF AUGITE AND A CORE OF MAGNETITE. 

In monzonite. Plain light. 

PHOF'ESSIONAL PAPEH 200 PLATE 14 

B. MONZONITE SHOWING GRAPHIC INTERGROWTH (I) OF ORTHOCLASE AND QUARTZ IN SHARP CONTACT WITH ORTHOCLASE (or). 

Crossed nicols. 

C. TYPICAL MONZONITE. 

The essential constituents are plagioclase, orthoclase, and pyroxene; biotite and quartz are accessory. The rather confusing appearance is due to the irregular feldspar grains and the apparent transition of one feldspar grain into another. Crossed nicols. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER. 200 PLATE 15 

A, B. INTERGROWTHS OF ORTHOCLASE AND QUARTZ WITH NUMEROUS HORNBLENDE FIBERS WHICH MAY PENETRATE 

ADJOINING GRAINS BUT DO NOT EXTEND FAR BEYOND THE BOUNDARIES OF THE INTERGROW'l''HS. 

Most of the fibers are parallel but some have a random orientation. Plain ligbt. 

C. PHOTOMICROGRAPH OF MIXED ROCK FROM A CONTACT BETWEEN PRE-CAMBRIAN GABBRO AND MONZONITE. 

The coarse-grained gray bands and lenses consist chiefly of green hornblende, 

augite, and labradorite, whereas the light-colored matrix is gabbroic, consist- ing chiefly of labradorite, augite, and hypersthene microlites. Plain light. 

D. AN ENLARGEMENT OF THE FINE-GRAINED MATRIX IN C, 

APPROXIMATELY SHOWN IN RECTANGLE. 

The light material conRists of labradorite with disseminated augite and hypersthene microlites. Plain light. 
GEOLOGICAL SURVEY 

A. PHOTOMICROGRAPH OF NORITE FROM THE APOPHYSIS ON 

STENDEL RIDGE. 

The rock consists essentially of plagioclase, augite, and hypersthene. The 

phenocrysts grade in size into the groundmass. Plain light. 

C. PHOTOMICROGRAPH OF FACIES OF TYPICAL MONZONITE FROM 

THE WEST SIDE OF THE MASS NORTHWEST OF STENDEL RIDGE, 

SHOWING LARGE POIKILITIC ORTHOCLASE WITH INCLUSIONS 

OF PYROXENE, PLAGIOCLASE, AND MAGNETITE. 

Some orthoclase grains have peripheral inclusions only. Crossed nicols. 

PROFESSIONAL PAPER 200 PLATE Hi 

B. PHOTOMICROGRAPH OF MONZONITE FROM WEST SIDE OF 

MASS NORTHWEST OF STENDEL RIDGE, SHOWING INTERSTITIAL MICROGRAPHIC INTERGROWTHS OF QUARTZ AND 

"DUSTED" ORTHOCLASE. 

Plain lighL 

D. FIBROUS HORNBLENDE IMPREGNATING EPIDOTE IN EPIDOTIC 

MONZONITE FROM THE NORTH SLOPE OF THE MAIN MONZONITE HILI" EAST OF HARDSCRABBLE VALLEY. 

Plain light. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE l'i 

A. OUTCROP OF PRE-CAMBRIAN GRANITE ON NORTH END OF MAGDALENA RANGE EAST OF ANCHOR CANYON, 

SHOWING ANGULAR OUTLINE AND BOLD CLIFFS. 

H. OUTCROP OF 'J'ERTIARY (?) GRANOPHYRE NOilTHWEST OF STENDEL RIDGE, SHOWING 

SPHEROIDAL WEATHERING AND SUBDlJEl) SLOPES . 

• 
GEOLOGICAL SURVEY 

A. POLISHED SURFACE OF TERTIARY (?) GRANITE. 

The chief constituents are orthoclase, quartz, and biotite, with subordinate 

oligoclase. Phenocrysts are rare, but local segregations of feldspars, as seen on the lower right, tend to produce a porphyritic appearance. 

PROFESSIOKAL PAPER 200 PLATE 18 

B. PHOTOMICROGRAPH OF "GRANOPHYRE" FROM MASS 

WEST OF GRANITE MOUNTAIN. 

It shows an extreme development of micrographic intergrowth with cores 

of cloudy orthoclase. Mafic minerals are negligible. Crossed nicols. 

C. PHOTOMICROGRAPH OF TERTIARY (?) GRANITE, SHOWING CLOUDED ORTHOCLASE, BIOTITE, INTERSTITIAL QUARTZ, 

AND A LARGE CLEAR GRAIN OF OLIGOCLASE IN THE UPPER RIGHT CORNER. 

Many of the orthoclase grains are especially cloudy near their borders and cleavage cracks but have clear centers, 

whereas others are cloudy throughout. Plain light. 
GEOLOGICAL SURVEY 

A. PHOTOM~CROGRAPH OF METAMORPHOSED SANDSTONE FROM 

AN INCLUSION IN GRANITE WEST OF G-RANITE MOUNTAIN. 

The larger quartz grains have been replaced along their margins by concentric rows of specks .consisting of sericite and liquid-filled cavities; the smallest grains have been more completely replaced. Detailed study shows the edges of the quartz 

grains to be irregular and scalloped. The interstitial material consists of sericite and clouded orthoclase with some iron oxide. Plain light. 

PROFESSIONAL PAPER 200 PLATE 19 

B. PHOTOMICROGRAPH OF TERTIARY (?) SANDSTONE WEST OF 

GRANITE MOUNTAIN PARTLY REPLACED BY A MICROGRAPHIC 

' INTERGROWTH OF ORTH9CLASE AND QUARTZ. 

The outlines of quartz grains are faintly shown. ote the scalloped edge between quartz and orthoclase along the lower contact. A biotite flake crosses the inter· growth and is very pr.ohably later. From the same thin section as C. Plain light. 

C. PHOTOMICROGRAPH OF TERTIARY(?) SANDSTONE FROM MASS WEST OF GRANITE MOUNTAI 

The replacement has progressed irrespective of the boundaries of the quartz grain. The border of the advancing orthoclase is dark and cloudy, whereas the inner portion, which consists in part of oligoclase, is clear. The dark border may represent more thorough impregnation of the quartz than the marginal specks in A. It is prob- able that replacement advanced by diffusion and that the dark border is an exceedinglv fine intergrowth of quartz and orthoclase, not resolvable under the micro- scope. Much of the orthoclase shows micrographic intergrowth with quartz. Plain light. 
. TE1

RTIARY (?) [NTRUSIVE IGNEOUS · ROCKS 41 . 

60 feet long. The aplite is light pinkish gray and 

very fine even grained. Quartz and • feldspar are 

recognizable as the ~hief -constituents, and some dikes 

also contain small scal~s of pale biotite. Those without biotite resemble the fine-grained feldspathized 

quartzite (hybrid granophyre) on Granite Mountain. 

In thin section the aplite dike in monzonite resembles 

closely the fine-grained Tertiary ( ? ) granite in texture 

and composition. Its grains are irregular in shape 

and have an average size of 0.4 millimeter.! It consists 

of 85 percent of cloudy microperthitic orthoclase, 10 

percent of interstitial quartz, with sodic oligoclase, 

biotite, pale-green hornblende, magnetite, zircon, apatite, titanite, and allanite constituting the remaining 

5 percent. The feldspars are slightly sericitized and 

epidotized, and a few grains of biotite have been partly 

or completely altered to chlorite. Rosettes of tour- . 

maline 3 millimeters in diameter are present on fractured surfaces, but none are intergrown with the 

minerals of the rock. Tourmaline similarly occurs in 

monzonite, felsite, and argillite to the north, especially 

near the large quartz vein shown on plate 2. 

The aplite in Tertiary ( ?.) granite in thin section 

shows a distinctly granitic texture with an average 

grain diameter of about 0.6 millimeter. It consists of 

clouded microperthitic orthoclase, quartz, sodic oligoclase, and a few grains of magnetite and zircon. The 

feldspars are partly to completely sericitized. Orthoclase is in part distinctly interstitial to quartz, and 

many corroded grains of quartz included in orthoclase 

indicate partial replacement of quartz by orthoclase. 

PEGMATITIC MATERIAL 

Although no pegmatite dikes have been found in 

the Tertiary (?) intrusive rocks, the Tertiary (?) 

granite east of the Hardscrabble mine is pegmatitic 

in places along its contact. On the crest of the ridge 

east of Anchor Canyon, near the east boundary of the 

Tertiary ( ? ) granite, the pre-Cambrian granite is cut 

by a short veinlet about an inch thick containing black 

tourmaline, feldspar, and quartz that may represent 

pegmatitic material from the Tertiary (?) granite. 

GRANOPHYRE 

Granophyre constit-utes the greater part of the. small 

stock just northwest of Stendel Ridge. It is bordered 

on the east by monzonite, into which it grades rather 

abruptly, but its other limits are concealed beneath 

alluvium. The hybrid rock west -of the granite on 

Granite Mountain simulates granophyre, but from 

field and microscopic evidence _presented below it is 

inferred to be a transformed sandstone. It should 

logically be described in the section on igneous metamorphism, but, because of its similarity to granophyre 

and the light that it sheds on the origin of some grano200889-42--4 

phyre, its description follows that of the granophyre 

\Vest of Stendel Ridge. 

The granophyr~ is fine-grained and resembles aplite. 

It is most commonly pinkish gray, but some is dark 

gray. It consists of pink · orthoclase and quartz with 

scattered biotite. 

Its mineral composition, estimated in thin section, 

is orthoclase 70 to 90 percent, quartz 7 to 20 percent, 

sodic andesine as much as 7 percent, biotite with a little 

augite and hornblende 2 or 3 percent, magnetite, apatite, and zircon about 1 percent. The outstanding 

microscopic feature, which also characterizes the rock 

west of Granite Mountain, is the development of 

micr9graphic intergre>wths of orthoclase and quartz 

around well-formed crystals of microperthitic orthoclase and rarely of irregular to well-formed grains of 

oligoclase and quartz. The orthoclase is much clouded 

with dustlike particles but is only slightly sericitized. 

A few of the quartz grains are embayed as if partly 

replaced by orthoclase. The biotite is similar to that in 

the -adjacent monzonite and is accompanied in part by 

the other minor minerals. Magnetite, zircon, and apatite occur mostly in irregular grains. Titanite, which 

is a conspicuous minor mineral in the Tertiary (?) granite, is absent. The granophyre also differs from the 

granite in its finer texture, in the presence of micropegmatite, and in the somewhat more calcic plagioclase. 

HYBRID GRANOPHYRE 

A hybrid rock that simulates granophyre occurs west 

of Granite Mountain, where it is bordered by granite 

on the north and east and by Tertiary. ( ? ) sandstone 

on the west beyond the area mapped. A. brief reconnaissance trip into the low hills west of Granite Mountain showed ·local ·patches of this hybrid rock in the 

sandstone. Many inclusions of the sandstone partly 

to completely replaced . are pr~sent in the granite on 

Granite Mountain, but only the largest is shown on 

plate 2. There is a rather abrupt transition from the 

granite into the hybrid rock, so that the boundary 

line between them can be closely approximated. The 

hybrid rock is brown to buff, and in both it and the 

adjacent sandstone are abundant rusty stains and spots. 

Megascopically feldspar and quartz can be recognized. 

Under the microscope the outstanding feature in this 

rock, as in the typical granophyre, is the development 

of micrographic intergrowth of orthoclase and quartz 

(pl. 18, B), which borders crystals of orthoclase. A 

few scattered grains of sodic oligoclase and · muscovite 

are present. The feldspars are greatly altered to sericite, which is accompanied by n1inute flakes and 

sheaflike clusters of biotite. Much of the rock is 

rust-stained. 

That this rock is a transformed sandstone and not 

of direct igneous origin is suggested by its similarity 

to the altered sandstone inclusions in the granite as 

. well as by its field relations. . 
42 MAGDALENA MI~ING DISITRICT, NEW MEXICO 

The sandstone inclusions in granite range from 

sandy to aplitic in appearance. The aplitic variety 

consists of quartz grains in a micrographic matrix that 

has partly to completely replaced the original matrix 

and quartz grains of the sandstone. The earlier stage 

of the replacement process is shown by a specimen 

from the large sandstone inclusion a few feet from its 

contact with granophyre. Its general color is red but 

it contains white and gray spots about a quarter of an 

inch in diameter. Upon weathering the red material 

is first removed, leaving the gray and white areas in 

relief. In thin section (pl. 19, A) · it consists of a 

mosaic of angular to rounded quartz grains with interstitial sericite, orthoclase, and chlorite, and some iron 

oxide. Some quartz grains have ·scalloped outlines 

owing to repla.cement by sericite and orthoclase, but 

the most noteworthy feature is the impregnation of the 

·grains along their borders and fractures by minute 

dark specks. These specks form rows that parallel 

the outlines of the larger grains, but they have no 

apparent arrangement in the smaller ones. In some 

of the larger grains also specks occur in a line crossing 

the grain. The larger specks comprise sericite and 

distinct liquid-filled cavities along whose walls films 

of iron oxide have been deposited. 

A more aplitic specimen from a point near the 

~arne contact represents a more advanced stage of 

replacement of somewhat different type. It consists 

of 'interlocking grains of quartz (pl. 19, 0) partly 

replaced by extremely fine-grained micrographic orthoclase and quartz, with minor amounts of oligoclase, 

iron oxide, sericite, green mica, and chlorite. The 

interlocking quartz grains presumably represent a 

quartzitic facies of the sandstone. This hybrid granophyre is invaded by darkly clouqed orthoclase, which 

evidently penetrated along grain boundaries and fractures and replaced the quartz grains so completely 

that very few of them remain even as corroded inclusions. The replaced silica evidently recrystallized in 

part in the micrographic intergrowths but was largely 

removed. In places (pl. 19, B) the micrographic 

intergrowth is coarser-grained and more distinct. 

Very pale green mica and sericite partly replace the 

orthoclase and evidently represent a waning stage of 

replacement. 

The essential identity of the replaced parts of sandstone inclusions and the hybrid granophyre, both in 

texture and mineral composition, leads to the inference that the granophyre on Granite Mountain is 

largely or wholly the result of replacement of sandstone by hydrothermal solutions rich in potash and 

alumina. The position of the granophyre, which caps 

a low spur bounded on three sides by granite, suggests 

that it is a replaced roof pendant and therefore accords 

with this inference, although it would also accord 

with the inference that the granophyr€ was simply a 

product of gravitative differentiation at the uppermost part of the granite. 

The origin of granophyre in .general has been a 

subject of considerable discussion. In many places it 

occurs along the upper contacts of diabase, gabbro, or 

norite sills in siliceous sedimentary rocks and has 

usually raised the question of whether the gabbroic 

magma has assimilated enough roof rock to promote 

the separation of a granophyric differentiate or 

whether the original magma differentiated thus without reaction with the sedimentary rock.57 

The occurrence at Granite Mountain, described 

above, offers strong evidence that granophyre may be 

formed by the reaction of siliceous sedimentary rock, 

and perhaps of siliceous igneous rock as well, with 

solutions rich in potash and alumina that accompany 

or closely follow the intrusion of granitic and monzonitic magma. 

There is no direct evidence from which to interpret 

the origin of the granophyre near Stendel Ridge. Its 

relations to adjacent rocks suggest that it may represent a similar replacement of either feldspathic monzonite or banded rhyolite or both. Its association with 

monzonite instead of granite . favors such an origin 

rather than · simple differentiation, which should have 

produced the same results at Stendel Ridge as at 

Granite Mountain, where monzonite passes into granite and granite into granophyre. On the other hand, 

although petrographic evidence shows that it differs 

from th~ granite in its finer texture, in the presence of 

micropegmatite, and in the somewhat more calcic plagioclase, it likewise differs from the granophyre on 

Granite Mountain in the more abundant and more 

calcic r-lagioclase, presence of brown biotite, and less 

micrographic orthoc~ase and quartz. The nature of 

the problem was not fully appreciated when the rocks 

were ~napped. A careful review in the field, supple-

. men ted by more microscopic study, would doubtless 

throw more light on the problem. 

PITCHSTONE 

Two small dikes of pitchstone are exposed in prospect holes in the Madera limestone east of Granite 

Mountain. The rock is glassy and breaks with a 

conchoidal fracture. It is green on a weathered surface but brown where unaltered. It cannot be traced 

along the strike, and it has not been found in any 

other formation; therefore its age relation to the other 

igneous formations is unknown. 

51 Bowen, N. L., The evolution of the igneous rocks, Princeton University Press, pp. 90-91, 1928. Daly, R. A., Geology of the North American 

cordillera at the fort.y-ninth parallel: Canadian Geol. Survey Mem. 38, 

pp. 221-255, 1912; Igneous rocks and the depths of the earth, ,New York, 

McGraw-Hill Book Co., pp. 428-436, 1933. Schofield, S. J., Origin of 

granite in the Purcell sills : Canadian Dept. Mines, Mus. Bull. 2, 1914. 
TE1

RTIARY (?) , 1INTRUSIVE IGNEOUS R01CKS 43 

LAMPROPHYRE DIKES 

The rocks mapped as lamprophyres include the basic 

dikes that were intruded after the emplacement of the 

Tertiary ( ? ) stocks. These dikes are distributed 

thr:oughout the district except in the extreme southern 

part but are most abundant within and near the monzonitic stocks in the central and northwestern parts. 

There they are associated with later white rhyolite 

dikes, some o:f which lie alongside or in direct contact 

with them. The lamprophyre dikes range in length 

from a few feet, too small to be mapped, up · to 1,900 

feet. Their widths are generally from 5 to . 20 feet 

and probably do not exceed 30 feet. In Madera lime-· 

stone southeast of North Camp a lamprophyre sill has 

been mapped. Other sills have -been noted in the upper 

Sandia formation on the southwest slope of Tip Top 

Mountain and at the southeast end of the Granite 

Mountain area, but they are too small to be mapped. 

In color and general appearance these dikes vary 

greatly. The least altered rocks are blackish gray a:t;1d 

of basaltic appearance, but those that have been considerably chloritized • are green. The texture, too, 

varies. Some varieties are porphyritic and others nonporphyritic with very fine grained groundmass; and 

still others are slightly porphyritic with ·a fine~ unevengrained ·groundmass. The phenocrysts, which most 

commonly constitute less than t) ·percent of the rock, 

consist chiefly of irregular white plagioclase grains as 

much as 5 millimeters in length. In the green facies, 

especially in the dikes west of · Stendel Ridge, ·darkgreen specks of chlorite are conspicuous; and, together 

with the white plagioclas~, give a speckled appearance. 

Grains and clusters o:f calcite can be recognized in some 

dikes. · 

The dikes also vary considerably in primary and 

secondary 1nineral composition. Some minerals are 

only slightly altered, but most of them are considerably altered to calcite, chlorite, epidote, quartz, and 

sericite, but in varying proportions in different dikes. 

These differences are illustrated by brief descriptions 

of six varieties of dikes. 

1. The only unaltered lamprophyre was obtained 

from a dike in granophyre northwest of Stendel Ridge. 

In thin section it proved to be nonporphyritic and finegrained with a minor amount. of microfelsitic material. 

The gr~nular constituents are augite, hornblende, and 

andesine in about equal parts, with minor amounts of 

magnetite, biotite, and apatite. Hornblende is of the 

brown variety but of relatively low birefringence. 

2. Another variety, which is only slightly altered, 

consists chiefly of an ophitic intergrowth of labradorite 

laths as much as 2 millimeters long and augite, with 

some chlorite and calcite, the whole peppered with iron 

oxide. 

3. Some of the por:phyritic dikes consist of calcite 

pseudomorphs after hornblende ( ? ) in a groundmass 

composed largely of andesine laths 1 millimeter or less 

in length, accompanied in one specimen by interstitial 

chertlike quartz but more commonly by calcite, with 

some chlorite, sericite, and quartz. Iron oxide is relatively abundant. Scattered through the rock are small 

shreds of brown biot.ite, which :was apparently the last 

mineral to form. 

4. A fourth variety consists of andesine phenocrysts, 

somewhat replaced by calcite and sericite; and augite 

( ? ) phenocrysts cbmpletely replaced by chlorite, in a 

groundmass composed of andesine laths considerably 

replaced by calcite, sericite, chlorite, and scattered · 

shreds of biotite. Iron oxide and apatite ar.e the 

accessory minerals. .. · 

5. A fifth variety consists of albite-oligoclase phenocrysts, in part replaced by sericite and calcite, a few 

scattered horn.blende pheiwcrysts, in part altered to 

~hlorite, and a much altered groundmass of plagioclase 

laths and interstitial quartz, largely replaced by chlorite, calcite, quartz,. and some epidote. Iron oxide and 

apatite are common. 

6. A sixth group may or may not contain phenocrysts of plagioclase and chlotitized hornblende. The 

matrix consists of ·albite laths, uralitic hornblende, and 

some quartz. :r'he albite is partly replaced by epidote 

and cal cit e. In one section of a porphyritic variety 

the plagioclase phenocrysts are considerably sericitized, 

and the hornblende is replaced by chlorite and epidote. 

Like the other varieties, this rock also has considerable 

iro)l oxide and some apatite~ 

To summarize, the dominant feature of the lamprophyres is the groundmass, which consists chiefly of a felty aggregate of plagioclase. The plagioclase ra1\ges from 

labrodorite to albite, with characteristic and relativ~ly 

abundant well-formed crystals of iron oxide. With 

few exceptions, the dikes also contain abundant secondary minerals, among which calcite, chlorite, epidote; or 

sericite predominates. Some of the dikes also contain 

abundant quartz, most of which is probably secondary. 

Brown biotite is oneof the unusual secondary minerals, 

which was no~ found among the secondary minerals in 

the other rocks. Insofar as their primary mineral composition can be . inferred, most of the dikes may be 

classified as spessartite, but those with an excess o£ 

hornblende are more appropriately called camptonite. 

WHITE RHYOLITE 

The white rhyolite dikes, the· young~st .of the. igneous 

rocks, are found mainly in two zones of 1iortherly 

trend. One, comparatively narrow, is in and near the 

granitic stock on the west slope of Granite l\fountain 

and continues for at least 2 miles northward beyond 

the area mapped~ .The other, · much broader, is in 

and near the Anchor Canyon granite stock. Other 

comparatively isolated dikes have been. mapped 3,500 

feet east-northeast of Tip Top· Mountain and in ·the 
44 MAGDALENA MINING DISrTRICT, NEW MEXICO 

Grand Ledge tunnel in the southeastern part of the 

district. Those east of Tip Top Mountain are presumably end members of the broad zone, and a careful 

search for dikes to the north of them. would probably 

prove them to be less isolated. The dike in the Grand 

Ledge tunnel lies along a mineralized fault zone that 

extends northward through the Linchburg workings, 

where the presence of garnetized Kelly limestone suggests metamorphism near a concealed monzonitic or 

granitic stock to which the dike also may be related. 

Most of the dikes, which are conspicuous because 

of their white color, range in true width from 10 to 

25 feet, and few exceed 50 feet ; b1;1.t, because of their 

banded or sheet structure parallel to the walls, they 

weather into thin slabby fragments that have crept 

down slopes for considerable distances from the outcrops. The lengths of single dikes followed con tinuously without a break range from a f.ew tens of feet 

to 6,300 feet. Most of the dikes end rather abruptly, · 

and one dike may be followed by another in steplike 

succession a few tens of feet away. Although these 

interruptions Inay appear at first like obscure faults, 

no faults offsetting the dikes have been found ; on the 

other hand, some of the dikes have been intruded along 

faults. The maximum aggregate length of a steplike 

group of dikes is about 9,000 feet. The dikes dip in 

different directions, most of them very steeply or 

vertically, but some-notably those west of the Hardscrabble mine and west of Anchor Canyon-dip eastward at angles of only 35° or 40°, and their outcrops 

across the steeper spurs therefore follow very undulating courses. The white rhyolite also forms sills in the 

effusive rocks, especially in the lower andesite, east of 

Granite Mountain. 

Although the rhyolite is light pinkish gray on fresh 

fractures, its exposed surfaces are grayish white. It 

consists of quartz and dull, white feldspar phenocrysts 

up to 3 millimeters in 'diameter, in a dense appearing 

groundmass criss-crossed by hair like veinlets of quartz. 

The dikes in and near the Anchor Canyon stock are 

impregnated with pyrite cubes largely altered to limonite. Most of them are less than 3 millimeters in 

diameter, but some are as much as 5 millimeters. 

In thin section the rock appears roughly banded 

because of alternating coarser- and finer-grained layers 

in the groundmass. The quartz and orthoclase phenocrysts are in about equal amounts and constitute less 

than 10 percent of the ·rock. Quartz forms irregular 

grains. It has been considerably resorbed and is bordered by reaction rims. Orthoclase, somewhat clouded, 

occurs in single well-formed crystals and in clusters 

of rectangular to irregular grains. It is usually unaltered, but it may contain local bunches of sericite. 

vVhat probably were scattered biotite grains are now 

marked by pseudomorphous quartz and limonite, with 

or without a few shreds of muscovite. No other traces 

of ferromagnesian minerals are present. Apatite and 

zircon grains are very scarce. 

The groundmass consists of microgranular untwinned 

feldspar and quartz in poorly defined grains as much 

as 0.2 millimeter in diameter. It is thoroughly impregnated with sericite and some secondary quartz, 

which obscure it and help to account for the dense 

appearance of the surface. The coarser bands are less 

sericitized than the finer. 

. The partial analysis given below ·is of ~ typical 

sample taken about 1,000 feet southwest of the Hardscrabble mine. The outstanding feature of this analysis is the relatively high content of silica and potash, 

which is in keeping with the prominence of q:uartz 

and orthoclase phenocrysts and the .siliceous sericitized 

groundmass. The low lime and soda contents support 

the microscopic evidence of little or no plagioclase. 

The soda still present may be in the orthoclase. 

Pw·tial analysis of white rhyolite 

[A. R. Ferguson, analyst] 

8102------------------ 7~42 

Al20:1-------------- --- - 14. 17 

Na~O~--- -- --------- -- 0. 73 K2o____________ ____ ___ 6. 29 

Fe20a 1 -------- --- ------ • 79 

cao ____ ._ ______ ___ __ __ . 50 97.90 

1 All iron determined as Fe20 3 , although it is present mainly as pyrite. 

DIFFERENTIATION 

A comprehensive consideration of the origin and 

differentiation of the Tertiary ( ? ) igneous rocks would 

be lengthy and on the whole inconclusive, especially 

for the volcanic rocks. Certain features of the monzonite and granite stocks, however, are worthy of brief 

attention, particularly those that emphasize the influence of liquid or gaseous solutions during and after 

the closing stages of intrusion. 

The differences in sequence of the volcanic rocks in 

various parts of the district point to several centers 

of eruption, none ot which have been found within the 

district; indeed, the interlayered rocks even in the same 

part of the district may have come from more than 

one center. Until these centers throughout the region 

can be recognized and the rocks erupted from each center within single periods can be studied, the volcanic 

rocks will contribute nothing definite to present speculative ideas about differentiation. 

The intrusive masses of augite and hornblende andesites have little or no variation in composition and bear 

no significant relations to the monzonite group in mineral composition. The augite andesite, consisting 

essentially of andesine and augite, and the hornblende 

andesite, consisting chiefly of andesine and hornblende, 

are clearly not basic portions of the monzonite-granite 

magma,, 'vhose most basic facies is the gabbroic apophysis composed of labradorite, augite, hypersthene, and 

biotite on Stendel Ridge. The accessory minerals likewise point to a lack of relationship. Magnetite is rela-
' 

TE:RTIARY (?) ·INTRUSIVE IGNEOUS . RO'CKS 45 

tively scarce in the andesites, although common in the 

gabbroic apophysis and monzonite, and apatite is common in the gabbro and monzonite but absent or scarce 

in the andesites. The intrusive andesites therefore cannot be regarded as products of the essentially continuous process of differentiation that ga v.e rise to the 

monzonitic and granitic facies in the stocks. 

The stocks of monzonite and granite are of more 

interest, as they have not only certain features in common but also considerable diversity in structure and 

composition ; but even with them a vailahle data are 

iiisufficient to warrant more than tentative conclusions. 

Of the two usual concepts-that differentiation takes 

place either by gravitative changes within a molten 

mass after intrusion and during crystallization or by 

deeper-seated changes betiveen s11ccessive stages of intrusion-the first finds little or no support in . the district ; the second is the more favored of the two but is 

obscured by the positive evidence of qhanges caused by 

liquid or gaseous solutions reacting with these rocks 

during and after the closing stages of consolidation. 

These changes also· leave much for speculation, but they 

are of interest in their bearing on the derivation of 

ore-forming solutions, and the discussion that follows 

. will, therefore, be focussed on them. 

The evidence, presented on page 69, that the Nitt 

stock has oblitered a trans~erse fault zone and the 

Anchor Canyon stock lies along the axis of a mild flexure implies that the magmas that formed . these stocks 

and the volatile materials that accompanied or followed · 

their intrusion rose rather directly from a deep source 

through ground weakened by disturbance. The fact 

that each of these two stocks in the main range is 

largely homogeneous in composition but is completely 

separated from the other at the surface leaves doubt 

as to their relative ages, and therefore, as to the major 

process of differentiation that gave rise to them. The 

distribution of facies in the smaller composite stocks as 

well as the presence of small feldspathic and granitic 

dikes in the Nitt stock implies that the granite was later 

than the monzonite; but whether this conclusion can be 

applied to the large granite stock whose composition is 

essentially uniform over an area of 2lj2 square miles 

and through a vertical range of 1,700 feet may be open 

to question. · 

There is no consistent evidence that the magmas 

forming the stocks were appreciably affected in composition by the rocks that they invaded. The large 

granite stock, where exposed, is in contact with either 

pre-Cambrian granite or argillite and contains a large 

inclusion of Kelly-limestone, but no local variation in 

the granite was found to indicate contamination by 

either of these rocks. The Nitt stock is in contact with 

pre-Cambrian felsite and argillite, Paleozoic limestone, 

shale, and quartzite, and Tertiary ( ? ) volcanic rocks, 

but none of its variations. in composition show any consistent relations to these rocks. Hypersthene in granitic 

rocks is interpreted by some 58 to indicate that the in-

. truding magmas may have been contaminated by 

assimilation of aluminous sediments, and the presence 

of hypersthene in the monzonite at Magdalena may be 

regarded as the result of such contamination; but direct 

evidence in support of such contention was not found. 

The Nitt stock, as shown by its southern contact, invaded an unknown thickness of the pre-Cambrian 

argillite and the whole thickness of the Kelly and 

Sandia formations, but it is not known to what extent 

these rocks were assimilated by the magma. The Nitt 

stock shows minor variations along Stend,el Ridge, and 

the typical monzonite nbrth of the Graphic tunnel (see 

p. 38) has a narrow zone of norite or hypersthene 

gabbro adjacent to the inclusion of the pre-Cambrian 

gabbro, but in general the variations are unrelated to 

the host rock. Nor is the evidence afforded by the composite stocks northwest of Stendel Ridge and southwest 

of Granite Mountain indicative of contamination by 

exposed wall rocks, for on Granite Mountain both the 

monzonite and the granite are bounded by I;hyolite 

porphyry and latite and northwest of Stendel Ridge 

the monzonite is bounded by the banded rhyolite. The 

replacement of the Tertiary ( ? ) sandstone by grano-

. phyre is attributable to hydrothermal after-effects 

rather than to an attack by the original molten 

monzonite or granite. 

Such changes in mineral composition as have been 

noted are in general agreement with the reaction series 

in consolidating magmas as proposed by Bowen. 59 , The 

noritic or gabbroic facies, which, according to this idea, 

crystallized at the highest relative temperature, is 

represented by the dike that branches eastward from 

the Nitt stock on the northern part of Stendel Ridge 

and by the narrow border of'norite around the altered 

gabbro inclusion north of the Graphic tunnel. The 

noritic border around the inclusion of altered preCambrian gabbro is clearly a local reaction between the 

monzonite magma and the hornblende and feldspar of 

the gabbro. Such a reaction as suggested by Bowen,60 

should cause deposition of the "heat equivalent of 

the member of the series with which the liquid is saturated." The dike on Stendel Ridge, however, evidently 

marked the first stage of crystallization. It crystallized 

rather rapidly and was not penetrated later by liquid 

or volatile constituents of the magma. The same calcic 

· plagioclase and hypersthene that constitute the .dike 

may have crystallized · throughout the greater part of 

· the Nitt stock during this early stage, but, as the temperature of the magma declined and its fluid part became depleted in calcium, magnesium, and iron, these 

· early minerals tended to react with the· still molten 

68 Bowen, N. L., The evolution of 'the igneous rocks, Princeton Univer-

·, sity Press, pp. 207-214, 1928. ' · 

~9 Idem, pp. 55-62. 60 Idem, p. 221. 
46 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

material to fonn less calcic plagioclase and augite. 

The zonal character of the plagioclase and the lack of · 

sharp boundaries between many mineral grains favor 

this interpretation. 

Further decline in temperature eventually permitted 

the crystallization of sodic plagioclase, orthoclase, and 

quartz, the last two of which filled interstices among 

the earlier minerals. Concentration of water and other 

volatile materials during the later stages permitted the 

formation of biotite instead of the pyroxenes. . Further 

concentration of alkalies, silica, and volatile matter, 

together with local fracturing, accounted for the small 

feldspathic and granitic dikes that are found in the 

upper part of the Nitt stock along Stendel Ridge and 

along its margin in the vicinity of Oak Spring. 

Similar concentrations evidently took place deeper 

in the stocks after the upper part had become sufficiently 

crystallized to be subjected to fracturing, as is shown 

by the granite dike that branches from the Granite 

Mountain stock and contains rounded fragments of 

monzonite. The rounded rather than angular inclusions suggest either that the monzonite had not become 

well solidified before it was invaded by the granite or . 

that the corners and edges of the fragments were 

resorbed by granite. Both conditions may have existed. 

An extreme result of such concentrations is evi- ' 

dently represented on the west side of the Granite 

Mountain stock where hybrid granophyre is believed 

to have. replaced Tertiary ( ~) sandstone (pp. 41-42) 

whose position implies that the replacement took place 

along the roof of the stock. 

The fact that some stocks in the district are nearly 

homogeneous, whereas others are composite, discourages any idea of differentiation by crystal settling 

within the stock. On the basis of differentiation 

within a stock it is also difficult to explain just why 

one stock was arrested at the monzonite stage, whereas 

another was qontinued to 'the granite stage. The 

arrangement of the different facies on the present 

surface might suggest that the composite intrusive 

masses were of sill-like rather than stocklike form and 

were inclined westward and that the monzonite, the 

heaviest and the earliest of the facies, lay along the 

footw~ll, whereas the granophyre, the lightest facies, 

lay along the hanging wall; but the intrusive contacts 

as a whole do not suggest sill-like forms, although 

the hybrid granophyre west of Granite Mountain and 

the southernmost mass of magnetic rhyolite porphyry 

on Stendel Ridge are believed to be remnants of roof 

rock whose contacts with the intrusive rock conformed 

approximately to the general dip of the surrounding 

formations. It might be suggested also that the granite is an intermediate product of slow differentiation 

and that its presence at Granite Mountain indicates 

an arrested process, whereas its absence at the northwest base of Stendel Ridge indicates completion of 

the process. The comparatively large Nitt stock, however, whose rootlike contact at the south end of Stendel 

Ridge has already been noted, has little or no granite 

or granophyre in the upper ~ part, where the only indication of differentiation is the presence of the small 

feldspathic dikes and segregations within the typical 

monzonite and in the local ca;p rock of magnetic 

rhyolite porphyry. If crystal set.tling played any conspicuous part in differentiation, therefore, the magmas 

that forilled the stocks must have had different compositions before they were intrud~d. Such an inference would imply that the magmas were differentiated 

in a deep-seated reservoir and that monzonitic and 

granitic magmas were intruded at different times. If 

so, the granitic magma did not have access to all the 

channels followed by the monzonite and therefore left 

some monzonite masses intact, while it formed composite stocks with others and also formed independent 

stocks. If the granophyre northwest of Stendel Ridge 

were to be regarded as of direct igneous and not hydrothermal origin, it was presumably intruded last 

and was similarly selective, as it. is in contact with 

monzonite at only one place. No sharp contacts between the different facies have been found, partly 

because· the contacts ·are largely concealed beneath 

debris, and . the idea of successive intrusions of the 

different facies therefore lacks proof. It is conceivable 

that a late facies intruding an earlier one that was not 

thoroughly solid could form a gradational contact, as 

maintained by Daly 61 and Camsell.62 Such a concept 

may apply to the granite, but the clearly definite 

replacement of sandstone by granophyre west of Granite Mountain and the relatively inconspicuous evidence 

of replacement of monzonite by granitic material raise 

the question of how extensive replace!llent could have 

. been throughout the stocks. 

The local concentration of volatile materials during 

consolidation of the monzonite has already been considered. Small fe1dspathic or granitic dikes and 

·segregations within the upper part of a monzonite 

mass may readily be attributed to such concentration~ 

but the large granite masses, if attributed to a similar 

process, call for the concentration of an immense 

amount of volatile matter, which would be possible 

only in or below the deeper part of a monzonite mass. 

Localization, at least of the larger stocks, along intersections of. fauit zones or zones of structural weakness 

has been cited, and recurrences of movement after the 

consolidation of both monzonite and granite stocks 

(p. 70) have been recognized. It is therefore reasonable to infer that movements took · place during the 

period of intrusion. Some movements would allow 

accumulated volatile material to ri~e and permeate the 

61 Daly, R. A., The Okanagan batholith of the Cascade Mountain system: Geol. Soc. America Bull., vol. 17, pp. 351 and 353', 1905. 

02 Camsell, C, Geology and ore deposits of the Hedley district, B. C. : 

Canadian Geol. Survey Mem. 2, p. 88, 19.1 0. 
ROCK ALTERATION AND ITS SIGNIFICANCE 47 

uew ly formed rock along and near reopened fault 

zones and to replace its original minerals with later 

minerals in the reaction series.· M.onzonite not subjected to permeation at this stage of the intrusion 

would escape granitization. Microscopic evidence of 

such replacement has been found throughout the monzonite, but although it can readily account for the 

incipient alteration that produced the graphic intergrowths or orthoclase and quartz with hornblende 

fibers and locally small patches of partly to completely 

granitized rock, considerable imagination is required 

to picture such thorough diffusion through a stock of 

monzonite as to convert it entirely into a granite mass 

of uniform composition. The fact that granophyre is 

the evident end product of this replacement process 

would make it the more remarkable that the process 

in general was arrested at the granite stage. 

The granophyre at Granite Mountain represents the 

product of a· solution that was active after the· crystallization of the granite. Such a solution may have had 

only slight reacting power on the granite, whose composition is close to that of granopi1yre, but may 

have had appreciable influence on permeable rocks of 

different composition, such as sandstone and monzonite. 

It may also have been able to replace or at least recrystallize the glassy or microcrystalline groundmass of the 

banded rhyolite. 

Regardless of the extent to which residual solutions 

were effective in the development of different rock 

facies, the part played by liquid or volatile constituents 

during and after the consolidation of the monzonite 

deserves recognition and is discussed in the following 

section. In addition to . the small feldspathic and 

granitic facies already cited, the small veins composed 

of quartz, orthoclase, and epidote, near the monzonite 

contact at Oak Spring (p. 39) are of special interest, 

as they are intermediate between mineral aggregates 

characteristic of ·recognized igneous rocks and those 

of hydrothermal deposits. They may be regarded as 

representing temperatures below the stability range of -

the anorthite molecule of plagioclase, whose place has 

been taken by epidote, whether or not the calcium was 

derived from the monzonite or from limestone that 

had been invaded by the monzonite. They are closely 

associated with metamorphosed sedimentary rocks, the 

more siliceous of which contaip. considerable epidote, 

and thus support the idea that metamorphism ·was 

brouglit about by m~terials that in part escaped-from 

the crystallizing stocks and in part rose through them 

soon after consolidation wherever fracturing. or minor 

faulting peqnitted. \ 

The role played by lamprophyres in differentiation 

has never been adequately explained, and as any ideas 

that we might add regarding it would be purely speculative we shall content ourselves here with emphasizing 

the position of the lamprophyres and the still later 

white rhyolite dikes in the general sequence of events 

and the consequent necessity of looking for their source 

not in the visible intrusive stocks but .in a deep reservoir 

from which the stocks and the lamprophyre and rhyolite 

dikes as well as the ore deposits originated. 

ROCK ALTERATION AND ITS SIGNIFICANCE 

SUMMARY AND CONCLUSIONS 

The t~rm "rock alteration" as here used includes the 

chemical, mineralogical, and textural changes that have 

affected the sedimentary rocks after their deposition 

and consolidation and the igneous rocks after their 

crystallization from a magma. The degree and kinds 

of alteration were not uniform over the entire district. 

The products o£ alteration, therefore, differ from place 

to place in the district, and in any one place they differ 

according to the original composition and permeability 

of the altered rock and according to proximity to intrusive contacts and to the main , channels along which 

mineralizing solutions circulated. The evidence presented below shows a variety of processes that may 

have been active in some degree throughout the pe~iods 

of volcanic eruption; but it is believed that the more 

conspicuous effects of alteration may be attributed to 

processes that were active in successive stageS during 

and after the crystallization of the intrusive stocks. 

Early alteration may have been produced to some 

extent by escaping liquids and gases, during and after · 

each volcanic eruption, as is shown by phenocrysts 

with reaction rims, but its effects are relatively insignificant. Reaction rims around such minerals as hornblende or biotite are widespread and are recognizable 

even where the volcanic . rocks are least altered, but 

the effects of more intense alteration that has replaced 

the cores of these minerals with chlorite or with epidote, · sericite, calcite, or quartz, are prominent in 

certain areas and are clearly later than the reaction 

rims. Early alteration may also include the replacement of moderately calcic plagioplase by epidote, calcite, and less commonly albite. Secondary quartz in 

irregular grains and clusters is present in all the 

altered rocks, and some of it is unquestionably a byproduct of the early alteration of primary minerals; 

but its abundance in different areas and in different 

kinds of rocks, especially along and near faults, indicates that it has also been introduced by solutions that 

were distinct~y later than the volcanic eruptions and 

the subsequent intrusions of stocks . 

. The alteration that accompanied or foilowed the intrusion of the stocks resulted in recrystallization of the 

) argillite and rhyolite porphyry and the marbleization 

and silication of the adjacent limestone. The argillite 

and rhyolite porphyry are close to the monzonite contacts. Only; one exposure of argillite was found that 

clearly. indicated the infiltration of monzonitic material .. whereas most of the argillite nearby had been 
48 MAGDALENA MINING DISfi'RICT, NEW MEXICO 

converted into hornfels. Marbleized and bleached 

llmestones are found as much as 1,500 feet from the · 

contact, but such relatively high temperature ~inerals 

as wollastonite, tremolite, diopside, and garnet (grossularite) in silica ted limestone and andalusite in 

altered shale, with two exceptions, have not been found 

at a distance greater than about 200 feet. Garnet 

(andradite) and hedenbergite, associated with magnetite and sulphide minerals, occur at greater distances, 

notably along the main ore zones of the GraphicWaldo and Kelly mines and also in the Linch burg 

tunnel about 12,0.00 feet south of the monzonite contact. This exceptional occurrence in the Linchburg 

tunnel suggests the presence of a concealed stock, or 

at least a center of mineralization, at no great depth. 

Similarly, grossularite, magnetite, serpentine, chlorite, 

and bladed calcite, found on a prospect du~p on the 

south edge of the sedimentary area east of Granite 

Mountain, suggest that the Tertiary (?) granite, concealed by alluvium, extends northward from the main 

range to this vicinity. The relations of this group of 

secondary minerals in limestone to the stocks clearly 

indicate that these minerals belong to a period of 

alteration that began contemporaneously with or even 

subsequent to the crystallization of the stocks and, as 

will be shown later, continued through the different 

stages of ore deposition. 

In the shale, quartzite, and volcanic rock adjacent to 

limestone that contains these high-temperature minerals are conspicuous amounts of epidote muscovite 

h . ' ' c lonte, sepentine, calcite, and quartz. This mineral 

assemblage is also found much farther from intrusive 

contacts. It is distributed throughout the northern 

and central parts of the district and is present to different degrees in ahnost all the formations on Stendel 

Ridge and qranite Mountain. It is very . conspicuous 

in the more permeable tuffs. The intensity of alteration in these areas if;) greatest near fissure zones or along 

the contacts bet~een the sedimentary and volcanic 

rocks, for example on the southeast slope and northern 

foothills of Stendel Ridge. There the rocks, regard-

-less· of their original composition, are thoroughly 

bleached and have been converted into fine-grained aggregates of quartz and sericite with a little pyrite. 

Farther away they are less thoroughly replaced, have 

greenish colors, and contain much disseminated epidote, 

chlorite, and calcite, as well as sericite and quartz. 

The relative abundance of these minerals also depends on the composition of the host rock. In general 

the less pure limestone and calcareous shales and the 

igneous rocks that contain relatively large amounts of 

original calcic minerals have developed larger amounts 

of epidote and calcite, whereas those with more magnesian minerals have developed corresponding amounts 

of chlorite. 

The distribution of these secondary minerals points 

to their derivation from the hot solutions that permeated the district soon after the intrusion of the stocks 

and became cooler and weaker the farther they moved 

from the stocks; but the presence of some of these 

minerals also in lamprophyre and white rhyolite dikes, 

which cut the stocks and extend throughout,the district, 

indicates . that they were formed at least in part distinctly later than the consolidation of the stocks. The 

evidence as a whole; as will be shown, indicates that 

stocks, dikes, and mineralizing solutions were all introduced along zones of structural weakness and were 

derived from the same general .source. 

The chief process of alteration in the sedimentary 

rocks of the southern part of the district was the replacement of. the Kelly limestone and locally the preCambrian argillite along the upper part of the range 

by immense amounts of j asperoid. Large masses of 

jasperoid are also present east of Granite Mountain. 

Fractures and other openings in the j asperoid are filled 

or lined with vuggy quartz. Locally barite accompanies quartz in the vugs, and both minerals are coated 

in places by black mangenese oxides and green copper 

carbonate. Barite is also present in metalliferous veins 

that cut the jasperoid and indicate that silicification 

preceded ore deposition. The thorough silicification of 

the argillite aloJfg the Grand Ledge fault east of Patterson Canyon implies that there was a local source 

of silica supply nearby, either the same source that 

supplied the high-temperature ~p.inerals in the Linchburg tunnel or one stjll farther south. The fact that 

this extensive silicification took place before ore deposition correlates it with the formation of silicates 

farther north. It is thought, therefore, that both 

processes took place at the same general time but that 

the solutions in the southern area traveled so far before reaching limestone that they had been cooled below 

the temperatures at which silicates could be formed. 

The chief processes of alteration in the volcanic 

rocks in the southern area were hematitization and 

silicification. Only the purple andesite and latite 

porphyry, which were subject to permeation by solutions that spread along the Kelly-Graphic and Waldo 

fault zones, have been appreciably altered to sericite, 

epidote, chlorite, and calcite. · · 

Hematitization has imparted red and pink colors to 

the rocks and where these colors are most intense they 

have formed at the expense of the groundmass. Silicification in the volcanic rocks is most pronounced in 

the upper andesite, which contains many geodes or 

small spherical and irregular masses of chalcedony, 

the larger of which have replaced the red groundmass, 

and in the adjacent red rhyolite, which is crisscrossed 

by many quartz veinlets. Small lenses, veinlets, and 

grains of secondary quartz and chalcedony are also 

found in the banded rhyolite. The interiors of some 

of the larger geodes have been filled with calcite. 
ROCK ALTERATION AND ITS SIGNIFICANCE 49 

~Vhere the reddish rocks are cut by quartz-baritecalcite-sulphide veins they have been bleached to light 

gray, showing that the hematitization originated before 

the veins. The relations between these veins and the 

silicification in the volcanic rocks just cited is not 

clear. The presence of calcite in the .central parts of 

geodes could suggest that they ~ere formed by the . 

same solutions that deposited the veins, but ·the uniform distribution of geodes and the restricted distribution of the veins does not support the suggestion. 

Clay minerals and celadonite occur as minor alteration products in the upper andesite and to a smaller 

extent in the red andesite and red rhyolite. These 

minerals, together with the calcite that fills the chalcedonic geodes, were very probably formed during a late 

stage, when the temperature was comparatively low 

and the solutions had bee:n practically depleted of acid 

constituents but could still produce hydration. 

An outstanding feature of alteration throughout the 

district is the wide areal extent of the altered rocks in 

contrast to the localization of the ore deposits, which 

are confined to the immediate vicinity of fault zones. 

The alteration, therefore, evidently took place under a 

pressure sufficient to force solutions _through the heated 

rocks for these relatively great distances. Ore deposition is believed to have taken place at a later time after 

the renewal of fissuring or minor faulting had given 

opportunity for new supplies of liquid and volatile 

material to rise from great depth, in part through the 

igneous stocks themselves but mostly along fault zones 

in the surrounding rocks. 

In the following detailed descriptions the secondary 

minerals fo.und at and near intrusiye contacts and 

commonly called contact-metamorphic will be grouped, 

and those not definitely found at or near contacts will 

be described by areas. The alteration of the preCambrian rocks prior to the intrusion of the Tertiary 

( ~) stocks has already been discussed, and only the 

alteration attributed to Tertiary processes will be included here. The alteration of the rhyolite porphyry 

on Stendel Ridge and that of the Tertiary ( ~) sandstone west of Granite Mountain into hybrid granophyre also have already been fully described (pp. 

34 and 41) because of t?eir bearing on the origin of 

certain facies of igneous rocks. _These processes n1ay 

have been equivalent in time to those that produced 

anhydrous silicates in limestone, as both preceded any 

processes that produced similar results in both igneous 

rocks and limestones, as well as in shale and quartzite. 

ALTERATION NEAR INTRUSIVE CONTACTS 

ALTERATION OF PRE-CAMBRIAN ROCKS 

f 

Alteration of the pre-Cambrian rocks induced by the 

Tertiary ( ~ l intrusions is slight and in most places 

absent. Thus the contact between the pre-Cambrian 

granite and the Tertiary ( ~) granite is well exposed at 

several places and for varying distances in Anchor 

Canyon, yet no evidence of . alteration was found, except small seams of epidote, chlorite, specularite, and 

quartz~ which may have been formed either in preCambrian time or subsequent to th;e intrusion of the 

Tertiary ( ~) granite. The usually dark pre-Cambrian 

felsite locally may be bleached nearly white; but the 

bleached rock is adjacent to veins, for example north 

of Ambrosia Peak, and the bleaching has undoubtedly 

been produced by solutions spreading from vein fis-. 

sures and not by the intruding granite. The intrusion 

of the Tertiary ( ~) granite into argillite produced no 

noteworthy alteration, but the intrusion of the Ni.tt 

monzonite stock converted argillite into hybrid rock 

and hornfels near the Graphic tunnel. Tufts of tourmaline are found on fracture surfaces in the argillite 

and felsite, but they do not penetrate either rock. 

They also coat fracture surfaces in the monzonite and 

are present in aplite dikes south of Hardscrabble 

Camp. They are therefore clearly related to the Tertiary ( ~) intrusions. 

Hybrid rock between monzonite and argillite is 

found on the spur north of the Graphic tunnel . and 

just east of the roa'd leading to the Sleeper tunnel. 

It ·was unquestionably produced · by the monzonite 

intrusion. This zone of mixed rock is about 20 to 30 

feet wide and grades into the unaltered argillite. It 

is a rather light colored, banded rock and appears as 

though the argillite had become plastic and was then 

squeezed into bands. A thin section of this mixed 

rock shows much the same mineral composition as 

the argillite, but the constituents have recrystallized 

to a coarser grain. Quartz, muscbvite, chlorite, and 

biotite are the principal minerals, and orthocl:;tse, magnetite, and zircon are subordinate. The micas are 

pseudoporphyritic, an_d each tends to form relatively 

pure bands of uniformly oriented grains. Much of 

the colorless mica still is sericite, but most of it forms 

large :flakes.of muscovite up to 0.4 millimeter in diameter. Chlorite is of two varieties. The more common 

variety is green and contains rosettes and fine rods of 

a dark mineral with rather high birefringence, probably rutile. The other variety, regarded . by Ross 63 

as an . unusual species of chlorite, is yellow and its 

birefringence is as great as that seen in some of the 

green chlorite .. It is biaxial, but its optical character 

could not definitely be determined although it seems to 

be negative. A few crystals have good cleavage and 

parallel extinction, but t);le prevaping absence of any 

observable cleavage is unusual for either mica or 

chlorite. It usually forms poikilitic grains up to 0.75 

millimeter long with many quartz inclusions. It is 

practically all bordered by a very narrow margin of 

sericite, into which it appears to grade. 

Some of the gabbro and diabase dikes, which were 

63 Ross, C. S., oral communication. 
50 MAGDALENA MINING DI&TRICT, NEW MEXICO 

altered in pre-Cambrian time, show a late development 

of epidote and clinozoisite superimposed on the earlier 

alteration products, particularly uralite. The outstanding example ·is the wide dike northwest . of the 

Sleeper tunnel. This dike is in an area of hornfels 

and marbleized limestone near the monzonite contact. , 

Its late alteration products, which are similar to those 

ill shale and impure limestone described below, are 

attributed to emanations that accompanied or followed 

the latest stages of monzonite intrusion. 

ALTERATION OF SHALE 

An impure sandy shale, now metamorphosed into ,a 

dark-green hornfels, is found on the west side of the 

Kelly limestone at the Hardscrabble mine and is beljeved to represent the base of the Sandia formation. 

In thin section Jit is seen to consist essentially of subangular quartz grains with interstitial sericite, which 

has replaced part of the quartz. Scattered through 

the rock are large optically continuous areas of chlorite 

that enclose quartz grains. Andalusite forms a few 

scattered grains associated with the sericite and chlorite. This rock probably represents the most intense 

alteration of shale in the district. 

Northeast of Oak Spring an impure shaly bed of 

the lower quartzite about 75 feet east of the contact 

between monzonite and the quartzite of the Sandia 

formation is altered to a dark-green mass. A thin 

section shows this to consist largely of epidote, both 

as minute grains and as large optically continuous 

areas enclosing calcite, quartz, and chlorite. Some of 

the ~alcite appears fibrous and is probably the hightemperature variety. 

A shaly bed at the base of the lower quartzite just 

southeast of Oak Spring has been altered into a banded 

shale with green layers typical of this bed near the_ 

monzonite. A thin section shows this rock to consist 

of alternating layers of undeterminable claylike material with an· occasional quartz and chlorite grain 

and irregular blotches of apatite alternating with 

layers composed of numerous quartz grains embedded 

in dark bluish-green chlorite with relatively high birefringence. Occasional epidote grains are present. 

Alteration seems to have been confined to the quartzose 

layers, which were probably more permeable. The 

quartz grains themselves may be slightly corroded but 

in general have not been affected. 

ALTERATION OF LIMESTONE 

Marbleization.-White marbleized limestone is mostly 

confined to a zone within 300 /feet of the monzonite 

contact, but isolated local areas may be found 1,500 

feet from the contact. The Kelly limestone, which is 

predominantly a gray medium- to coarse-grained crystalline limestone throughout the area, has· been 

bleached and thoroughly recrystallized to a marble in 

a few places next to the contact. Its most intense recrystallization, accompanied by a minor development of 

silicates, took place in the inclusion in Tertiary ( ? ) 

granite at the Hardscrabble mine and along the east 

margin of the monzonite near Oak Spring. Both limestone and shale members of the Sandia formation have 

been so recrystallized and bleached in the area between 

Oak Spring and the Sleeper tunnel that the structure 

and stratigraphy are much obscured~ The Madera 

limestone is marbleized in the vicinity of the Nitt mine 

and near Hardscrabble Camp. 

Silication.-High-temperature silicate minerals are 

present at or near the ·contacts ·of the marbleized limestones with the Tertiary ( ? ) intrusive stocks. They 

include wollastonite, diopside, garnet, hedenbergite, 

tremolite, muscovite, sanidine, titanite, epidote, chlorite, 

and serpentine. They are mostly found within 500 

feet of the exposed contacts, and wollastonite and 

diopside are probably within 200 feet of them; but 

striking exceptions are the occurrence of garnet 

in the Linchburg tunnel and in the Granite Mountain area. In the Linchburg tunnel, about 12,000 

feet south of the nearest exposed monzonite contact, 

garnet (andradite) and hedenbergite are present in 

association with specularite, magnetite, and sulphides 

along the main mineralized fault zone. They suggest 

the presence of a concealed stock of monzonite, or at 

least 3: center of mineralization similar to those closely 

associated with monzonite, at no great depth. The 

grossularite in the altered limestone east of the Granite 

Mountain area suggests that the concealed north 

boundary of the Tertiary . (?) granite stock is nearby. 

The Kelly limestone contains more wollastonite, 

diopside, garnet, and hedenbergite than the other limestones, which for the most part are colored green by 

.epidote and chlorite; but the Madera limestone and 

the limestone members of the Sandia formation are 

bleached and partly replaced by silicates east of Oak 

Spring, near the Nitt mine, and east of Granite Mountain. The more intensive alteration of the Kelly limestone is attributed to its permeability and the scarcity 

of shaly beds to prevent circulation within it; furthermore, as it was the lowest of the limestones, it was the 

first to be reached by rising solutions, which were deflected into it by the overlying impervious shales. 

The best development and greatest number of silicate 

minerals in the Kelly limestone has been found near 

Oak Spring~ The thoroughly silicated limestone is 

white and consists of a very fine grained matrix with 

specks and streaks of a greenish prismatic mineral cut 

by thin veinlets of calcite. Its contact with the 

monzonite is very sharp. 

Microscopically the rock consists of an indeterminate 

dark-gray slightly pleochroic porcelain-like matrix, 

which encloses specks and areas of wollastonite and 

greenish diopside. Some garnet (grossularite) and 
ROCK ALTERATION AND ITS SIGNIFICANCE 51 

occasional flakes of 1nuscovite are also present~ A thin 

section of a specimen taken 'from the dump near Oak 

Spring shows tremolite, sanidine, and titanite in addition to those already mentioned. Tremolite is less 

common than wollastonite and is found in small blades 

within wollastonite and very probably replacing it. The 

prevailing purity of the original Kelly limestone implies that the constituents• of these silicates, with the 

exception of calcium, were introduced during metamorphism; but the magnesia and any alumina in them 

may have been derived from the "silver pipe" beds. 

The lower limestone member of the Sandia formation, east and northeast of Oak Spring, also contains 

areas that are colored .green by epidote or fine-grained 

pyroxene, both of which evidently represent recrystallization of the original rock with little or no addition 

of material except water. 

The Kelly limestone enclosed ' in Tertiary ( ? ) granite at the Hardscrabble mine contains masses -of pure 

wollastonite. The big caved stope east of the north 

glory hole is filled with blocks composed of altern'ating 

layers of white coarse- and fine-grained sugary wollastonite. The coaser-grained material consists of 

larger tablets of wollastonite in· a calcite matrix. 

Near the north end of the Hardscrabble workings, 

where the marbleized Kelly limestone is in contact 

with hornfels, a calcareous layer in the hornfels is 

composed of quartz, garnet (grossularite), and pyrite, 

with minor quantities of epidote, secondary calcite, 

and chloritic material. Aggregates of these minerals 

are interstitial to the quartz grains, which have very 

irregular interlocking contacts and may represent 

either introduced silica or original quartz thoroughly 

recrystallized. 

. Blocks ·of silicated limestone enclosed in monzonite 

close to its contact are exposed on the Nj tt 300-foot 

level. . Their positions imply that they belong to the 

. upper part of the Sandia formation or the lower part 

of the Madera limestone. One of these blocks is now 

a medium-grained" rock composed entirely of granular 

diopside in a subordinate matrix of recrystallized calcite. Here also the constituents of the silicates, except 

the magnesia of the diopside, can have been derived 

from the original rock, although here and elsewhere 

local transfer of material must be inferred to account 

for nearly pure masses of such silicates as diopside 

or epidote. · 

In the Granite Mountain area rock fragme~ts on 

two dumps along limestone layers within the upper 

quartzite member of the Sandia formation contain 

silicates, which suggest that the concealed north contact of the Tertiary (?) granite stock is nearby. One 

of these prospects is about 550 feet west. and 300 feet 

north of the southeast corner of sec. 12, T. 2 S., R. 4 

W.; the other is about 450 feet farther southwest. 

The fragments consist of pale-green dense serpentinechlorite rock banded with black layers of magnetite ~s 

much as one-eighth of an inch thick The serpentine 

predominates and is intimately intergrown with chlorite. Magnetite is present in large grains and as 

minute specks in the chlorite and serpentine. Associated with the minute magnetite grains are minute 

microlites of a transparent highly birefringent mineral resembling diopside. Neither the serpentine nor 

the chlorite show any evidence of derivation from some 

other silicate such as diopside. 

' Fragments of silicate rock -either from the lower 

limestone member of the Sandia formation or from a 

limestone layer in the shale member are found on a 

sm~ll dump 1,150 feet east of the southwest corner 

of sec. 7, T. 2 S., R. 3 W. These fragments at first 

glance r'esemble a coarse-grained granitic rock, but 

they consist of intergrown calcite, chlorite, quartz, 

epidote, garnet (grossularite), and diopside, listed in 

the order of their abundance. The calcite is bladed 

and is the high-temperature variety. Chlorite is for 

the mo~t part interstitial to th~ bladed calcite, but in 

. places lobes of it penetrate the blades. The lobate 

structure of the chlorite implieS" direct deposition from 

hydrothermal solutions and not derivation from some 

other silicate. Epidote is mostly associated with the 

quartz and chlorite, very little being present in the 

calcite. The few small scattered grains of garnet, 

which contain small remnants of partly replaced diopside, are most common in the calcite. These relations 

indicate the deposition first of diopside and then of 

garnet. Whether the bladed calcite was deposited 

with or after either of these silicates is not clear. It 

was followed by the deposition of chlorite, which was 

presumably formed at the same time as epidote and 

quartz. 

An inclusion of limestone in monzonite about 800 

feet northeast of the Graphic mine consists chiefly of 

calcite and diopside, with some sericitic aggregates and 

· a little garnet. The garnet forms narrow borders 

surrom:iding both calcite and diopside grains and 

partly replacing. both. · 

_ALTERATION FAR FROM INTRUSIVE CONTACTS 

ALTERATION IN THE NORTHERN AREA 

The rock alteration centering around Stendel Ridge 

and that · around Granite Mountain are similar, but 

they differ from that in the _southern part of the district south of Kelly. In the northern area the secondary minerals are epidote, chlorite, and sericite, 

accompanied by quartz and calcite. Though any one 

or more of these minerals 1nay predominate locally, 

none predominates over the entire region. In the 

southern part of the district these secondary minerals 

are present in appreciable amou)1ts only in the purple 

andesite and latite porphyry, and if they once existed 

in the upper volcanic rocks they were later destroyed 
52 MAGDALENA MINING DIS'l'RICT, NEW MEXICO 

by the solutions that silicified and hematitized these 

rocks. 

· Chlorite is common in the igneous rocks in the 

northern area and locally in altered shale and impure 

limestone. It is also a gangue mineral in the pyritic 

deposits of the Graphic-Waldo mine. In the effusive 

rocks it is an alteration product of hornblende, biotite, 

and less commonly augite, and it is enclosed in pseudomorphous rims of hematite. However, · some chlorite 

entirely free from hematite is so irregularly distributed through the ground masses of these rocks that it 

is evidently a direct precipitate from solution and not 

a direct alteration product of ferromagnesium minerals. The chlorite is commonly accompanied by epidote, calcite, sericite, and quartz. 

Epidote is probably the most abundant of the 

secondary silicates. It is an alteration product of ferromagnesian minerals and pl~gioclase of the igneous 

rocks. It is also widely distributed as veinlets and 

disseminated grains in the sedimentary roqks·. In 

addition to these obviously secondary modes of occurrence, epidote is a prominent and evidently primary 

constituent of feldspathic dikes and apophyses related 

to the Nitt monzonite stock; and it may be inferred that 

· the magmatic solutions that formed these apophyses 

aided in the formation of epidote in· both the igneous 

and sedimentary rocks nearby. 

Epidote is especially abundant in the basal tuff and 

·in the shale member of the Sandia formation on Stendel 

Ridge, in the thinly bedded sedimentary rocks in the 

ghlch south of the Vindicator shaft, and in the lower 

latite, lower andesite, and adjacent sedjmentary rocks 

in the Granite Mountain area. It is also abundant in 

the lamprophyre dikes, some of which owe their greenish color to it. It is only sparingly present as a gangtle 

mineral in ore bodies. · 

Limestone interbedded with the shales at the east 

base of Stendel Ridge is in places green with epidote. 

In the coarse breccia at the base of the overlying latite · 

the fragments of shale, limestone, and quartzite are 

impregnated and the tuffaceous matrix is largely replaced by epidote. Thin limestone beds alternating 

with the shale and quartzite beds of the Madera limestone in the gulch just to the south of the Vindicator 

shaft are partly replaced by epidote, and the green 

color in some of the shale beds may be due to the 

presence of epidote and chlorite. Impure limestone at 

the head of the draw east of the Waldo shaft contains 

streaks and layers colored green with epidote. 

The limestone and calcareous shale beds in the southeastern part of the Granite Mountain area are now so 

epidotized that the rock is green and is extremely vuggy 

and "knotty," owing to areas of epidote that stand 

in relief on weathered surfaces. A thin section of this 

.. vuggy rock reveals an intimate intergrowth of epidote 

and quartz with smaller amounts of calcite and chlorite. 

' 

I . 

Occasional tufts of sericite have replaced sorne quartz, 

and a little magnetite is also present. 

The occurrences of epidote in the · Stendel Ridge area 

are so related to the Nitt monzonite stock and 1ts late 

feldspathic dikes and apophyses that they are most 

reasonably attributed to solutions that emanated from 

the stock and moved along the more permeable parts 

of both sedimentary and vofcanic rocks. The relations 

of epidotized rock to the monzonitic stock of Granite 

Mountain are not so clear, but a similar interpretation 

of them is reasonable. The closing stage of stock intrusion, therefore, is regarded as the time when most 

of the epidote was formed, but minor quantities may 

have been formed by emanations that accompanied or 

closely followed any or all of the volcanic eruptions, 

and the epidote in the lamprophyre dikes, which cut 

the different varieties of monzonite, was formed at a 

later time, probably by water concentrated in the lamprophyre magma during its crystallization. 

Sericite is most abundantly developed in the white 

rhyolite dikes and along the late quartz veins, but even 

in the slightly altered rocks tufts of sericite impregnate 

the feldspar. Sericite is common in the magnetic 

rhyolite porphyry on the north end of Stendel Ridge, 

and locally it is common in the latite tuffs and the tuffs 

of the banded rhyolite west of Stendel Ridge. The 

extreme development of sericite in some of the quartz 

veinlets in the Tertiary ( ~) granite indicates that the 

main period of sericitization followed that of stock 

intrusion. Some quartz veinlets are now represented 

by a porous mass of quartz with films of sericite. One 

thin section shows quartz intercrystallized with fluorite 

and a few zircon grains. Both the quartz and the 

fluorite are extensively .replaced by sericite, which 

therefore is a comparatively late vein mineral. 

Secondary quartz is most conspicuous in veins and in 

one mass of j asperoid. It also forms irregular grains. 

and clusters in altered ig·neous rocks throughout the · 

district, but it is far less common in the northern and 

central parts than in the southern part (p. 53). Much 

of it is unquestionably a byproduct of the alteration 

of the primary minerals, but some may also have been 

introduced by permeating solutions. A thin section of 

a quartz vein in the Tertiary ( ~) granite contains 

abundant fluorite and pyrite, several zircon grains, and 

a few small allanite grains, all apparently contemporaneous, and sericite, which is interstitial to the quartz 

and apparently has replaced quartz and fluorite. 

Quartz forms the walls of the Anchor vein, and barite 

and fluorite form the middle. In the veins in monzonite and in the ore bodies nearby much of the quartz 

-was deposited with specularite and magnetite and also 

with the later pyrite,. whereas small amounts accompanied and followed the later sulphides. Thus, the 

evidence as a whole indicates that vein quartz was 
ROCK ALTERATION AND ITS SIGNIFIC'ANCE 53 

dep9sited over a long period but mainly ·before the 

deposition of ore minerals. 

The jasperoid mass, which replaced the basal part 

of the Kelly limestone 11j2 miles east of Granite Mountain, was also formed before the ore minerals. Its 

features are similar to ·those of the extensive jasperoid 

masses in the southern area, which are described on 

this page. 

Calcite in variable a;.mounts is present in all the formations, though very little has been found in the 

rhyolites. It is very common in the epidotized rocks, 

but it is also moderately common in rocks that have 

no epidote. Some of the much-altered lamprophyre 

dikes contain veinlets and pseudophenocrysts of calcite, 

and some · of the latite and andesite tuffs also contain 

ra.ther large quantities. Its ge~eral absence from the 

rhyolites implies that the calcite in general has been 

derived from such minerals as plagioclase, augite, and 

hornblende, which characterize the andesites, latites, 

monzonites, and lamprophyres, and that it belongs to 

tl~e same stages of alteration as chlorite, epidote, and 

sericite. The bladed calcite in silicated limestone 

(p. 102) was deposited during the high-temperature 

stage of alteration,- and the scalenohedral calcite (p. 

103) marked the closing stage of ore deposition. In 

short, the deposition of calcite in one form or another 

took place throughout the general period of rock alteration and ore deposition. 

ALTERATION IN THE SOUTHERN AREA 

The most common processes of alteration in the 

southern part of the district were ~ilicification of the 

Kelly limestone and hematitization of the volcanic 

rocks. Less commonly the hornblende, pyroxene, and 

biotite in the volcanic rocks were altered to minerals of 

the montmorillonite-beidellite group and cela¢lonite. 

Only the purple andesite and latite porphyry were 

appreciably altered to epidote, chlorite, and sericite. 

The purple andesite was also extensively altered to 

calcite, which partly replaced both phenocrysts and 

groundmass. The sedimentary rocks, other than the 

Kelly limestone, were not conspicuously altered, but the 

red A.bo sandstone, as well as the red volcanic rocks, 

has been bleached to light gray along the margins of 

veins that contain small amounts of sulphides. 

Silicification.-Silicification was the most. widespread 

process of alteration in the southern area. It profoundly affected \he Kelly limestone and locally the 

argillite, and its effects are represented to some degree 

in all the volcanic rocks by irregular· areas of chalcedony, bunches of mosaic quartz, and ·quartz veinlets. 

However, the largest amount of quartz in the entire 

district occurs as light-gray, yellowish, and brownish 

jasperoid, which has replaced a large part of the Kelly 

limestone from Tip Top Mountain to the south end 

of the district (pl. 2) and has even replaced the preCambrian argillite just southeast of the Grand Ledge 

tunnel. The jasperoid commonly contains lenticular and 

irregular vugs as much as 5 feet long. The presence of 

limestone remnants in the jasperoid suggests that at least 

the largest vugs represent similar remnants that have 

been removed by the solvent action of ground water or 

by surface weathering. Some of the sn1aller vugs, however, are clearly a result of brecciation of the jasperoid. 

The vugs are mostly parallel to the bedding and are 

lined with quartz crystals as much as half an inch 

long- and a quarter of an inch thick. In places the 

uppermost, platy layers of Kelly limestone have been 

replaced by thin bands of j asperoid separated by 

crystal-lined openings that represent original bedding 

p1 anes (see pl. 28, A) . 

Silicification evidently took place in two stages, 

·which were separated by a period ofshattering. These 

are indicated\ in places by the brecciated jasperoid (pl. 

28, B) and its re~ementation by clean, white, vuggy 

quartz aggregates, which are in marked contrast with 

the gray, yellowish, or· brownish jasperoid. Some small 

veins and vugs in the jasperoid, especially along or 

near mineralized faults, contain quartz and barite with 

small amc,unts of sulphides or their oxidation products. 

These veins, which fill distinct fractures in the jasperoid, are identical in mineral composition and structural relations with ore bodies that have been worked 

iu the vicinity and prove that the extensive replacement. by j asperoid preceded that stage of ore d~position. 

The boundaries between the limestone and j asperoid 

are_ sharp, like those in the Black Hills, South D< -

kota,64 and the Tintic,65 Stockton, and Fairfield districts,66 Utah, and field evidence therefore suggests the 

same explanation-that silification advanced as a wave . 

from fissures of access, replacing all the rock as .it 

progressed and maintaining al). abrupt contact until 

the impulse was exhausted; but thin sections show 

that, in son1e places at least, well-formed quartz crystals grew in advance of the main mass of jasperoid 

(see p. 101). · 

In· a few places, particularly along minor faults, both 

the lmver and upper parts of the Kelly limestone have. 

been thoroughly replaced, whereas the intervening 

"silver-pipe" bed has been only slightly affected; but 

only tLe uppermost thin platy beds have been replaced 

throughout the jasparoid area. A.s the relatively impervious limestones of Sandia and Madera formations, 

however, have escaped appreciable silicification, even 

along 'faults, it is concluded that the solutions depositing the j asperoid rose along premineral fissures until 

M Irving, J . D., Replacement ore bodies ; their characteristics and the 

criteria by means of which they may be recognized: Econ. Geology, 

vol. 6, pp. 556-558, 1911. 

66 Lindgren, Waldemar, and Loughlin; G. F., The geology and ore deposits of the Tintic mining district, Utah: U. S. Geol. Survey Prof. 

Paper 107, pp. 154- 158, 1919. 

66 Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quadrangles, Utah : U. S. Geol. Survey Prof. Paper 173, p, 98, 1932. 
54 MAGDALENA MINING DIS'l'RICT, NEW MEXICO 

they reached the shale at the base of the Sandia formation; they were then deflected along bedding planes and 

other openings in the Kelly limestone, particularly its 

uppermost beds, and replaced it with jasperoid. 

The maxim·um degree of silicification, in argillite as 

well as limestone, is along the Grand Ledge :fault zone. 

It is therefore concluded that this fault zone was the 

main conduit along which the silicifying solutions 

rose, and that bedding planes and transverse and longitudinal faults nearby served as branch conduits that 

permitted permeation of the limestone throughout the 

southern area. As the same fault zones later served as 

conduits for the solutions that deposited sulphides, the 

silicifying solutions were closely related in time with 

those that formed the silicates hedenbergite and andradite ..along the main conduits; furthermore, as the 

silicified rocks are far :from any recognized centers of 

high-temperature mineralization, it may be inferred 

that the solutions that formed them had traveled so 

far through underlying siliceous rocks that, by the time 

they reached the limestone, they had cooled below the 

temperature at which the silicates could :form . . In 

short, the silicified limestone is the equivalent o:f silicated limestone, but farther :from the sources of 

mineralization. 

Although silicification in the volcanic rocks is -much 

less intensive than in the Kelly limestone, it is rather 

widespread. It is most conspicuous in the red andesite 

and upper andesite. The scoriaceous parts of the red 

andesite contain vugs lined with chalcedony and centrally filled with calcite. The upper andesite conta.ins 

many geodes of chalcedony, and its weathered surface 

also is strewn with many residual fragments of the 

geodes. The largest geodes have replaced the reddish 

groundmass. The red rhyolite has a rather glassy 

luster, caused by the silicification of its groundmass, 

and is crisscrossed by many white quartz veinlets. The 

·more porous layers in the banded and the pink rhyolites 

contain small openings partly or completely filled with 

quartz. The other volcanic rocks of the area, as shown 

by thin sections, have been only slightly silicified. 

The process of silicification is most conveniently considered with that of hematitization,. which follows. 

H ematitization.-The most striking product of alteration in the volcanic rocks of the southern area is 

• hematite, which has given red, pink, and purple colors 

to all varieties except the relatively impermeable 

vitrophyre at the top of the upper andesite~ . 

The hematite in the redder rocks is of two varieties. 

When examined under the binocular microscope in 

reflected light, hematite in the resorbed phenocrysts is 

bluish-black and appears granular to micaceous. This 

. variety is evidently specular hematite and is proba-bly 

a high-temperature product of resorption. The other 

variety, which is exceedingly fine grained and is scattered through the groundmass, is red in reflected light 

and. accounts for the reddish color of the rocks. 

The finely divided hematite in the reddish rocks for 

the most part represents complete oxidation and in 

part redistribution of the original iron content, although some of it may represent iron that was introduced. Most of the red andesites probably had sufficient iron originally to account for their present content of hematite, but at least part of the hematite in 

the banded rhyolite was evidently introduced from 

another source. In the central area and west of Granite Mountain, :for example, the banded rhyolite is pale 

gray and thin sections of .it show insufficient iron oxide 

or :ferromagnesian material to account :for all thehematite that the same rock contains in the southern 

area. The excess may ·have been derived from the 

andesites. 

Although some hematitization may have been effected 

by gases and liquids that escaped from each flow as 

it solidified, as is believed to have happened in the 

upper part of flows in the Michigan copper country 67 

and in some flows in south-central Oregon,68 hematitization at Magdalena has taken place throughout entire flows and in such great degree that any hematite 

:formed during the different eruptions has evidently 

been supplemented by deposition from solutions that 

permeated all the flows subsequent to eruption. 

The coextensiveness of both red hematite and chalcedony strongly i:pdicates that both were :formed by 

solutions :from the same .general source. The :fact that 

the red groundmass of the upper andesite has been 

replaced by chalc~dony geodes shows that concentration of silica into geodes took place after hematitization, although silicification and hematitization of the 

groundmass as a whole, as in the red rhyolite, may 

have been parts of one general process. Gruner's 

experiments 69 show that magnetite and presumably 

ferrous silicates can . be oxidized by steam at a temperature as low as 200° C. and that oxidation is accelerated by the addition of a small amount of hydrochloric acid. · 

Similar results can be produced by the presence of 

small amounts. of sulphuric acid, as shown by Day 

and Allen,70 and by Burbank,71 who has applied the 

findings of Day and Allen to the altered rocks of the 

Bonanza district, Colorado. The degree of this kind 

61 Butler, B. S., and Burbank, W. S., The copper deposits of Michigan : 

U. S. Geol. Survey Prof. Paper 144, pp. 34-45, 1929. 68 Fuller, R. E., The mode or origin of the color of certain varicolored 

obsidians: Jour. Geology, vol. 35, pp. 570-573, 1927. 09 Gruner, J. W.,· Hydrothermal oxidation and leaching experiments; 

their bearing on the origin of Lake Superior hematite-limonite ores: 

Econ. Geology, vol. 25, pp. 697-717 and 837-867, 1930. 70 Day, A. L., and Allen, E. T., The volcanic activity and hot springs 

of Lassen Peak: Carnegie lust. Washington Pub. 360, pp. 113, 140-145, 

1925. Allen, E. T., and Day, A. L., Steam wells and other thermal activity at "The Geysers," California: Carnegie lust. Washington Pub. 378, 

pp. 45-50, 1927. 

n Burbank, W. S., Geology and ore deposits of the Bonanza mining 

district, Colorado : U. S. Geol. Survey Prof. Paper 169, pp. 80-85, 1932. 
S.TRUCTURE 55 

of alteration at Magdalena is less than . at Bonanza, 

where the reddened rocks were much silicified and the 

greatest amount of alteration was more clearly assoc]ated with mineralized fissures. 

' It may be inferred, however, that volcanic exhalations, which commonly consist mainly of steam with 

some hydrochloric acid, hydrogen sulphide, or sulphuric acid and carbon dioxide, produced both silicification and hematitization in the southern part of the 

district; furthermore, that during ·the process the 

silica tended to move into cracks and other openings, 

forming veins and geodes and replacing small amounts 

of the adjacent rock. It is also conceivable that small 

quantities of silica were introduced after hematitization. 

As the reddened volcanic rocks have been bleached 

along the margins of quartz-sulphide veins, hematitization must have preceded ore deposition and therefore ' 

may have taken place at the same general time as 

silicification in the limestone. If both processes are 

attributed to the same solution, the solution must have 

been largely depleted of silica before it permeated the 

volcanic rocks. 

Alteration to clay minerals and celadonite.___;_The 

origin of two more alteration products in the upper 

and red andesites and the red rhyolite deserve attention. These are the fibrous mineral of the montmorillonite-beidellite series and celadonite. 

The montmorillonite-beidellite partly to completely 

replaces hypersthene and is also found in plagioclase 

phenocrysts as blotches not related to cleavage cracks. 

Its most common variety is pale green. But another 

variety, which is coffee brown though like the green 

variety in its other properties, in places grades into 

the green variety, suggesting that both are of the same 

group and suggesting also that the green variety may 

have a higher content of the nontronite molecu]e.72 

Hypersthene in the upper vitrophyric part of the 

upper andesite is partly replaced by a .mineral that 

has a distinct bright-green to yellowish-green pleochroism and appears to be optically identical with 

celadonite.73 Augite and biotite in the same rock are 

unaltered. The smaller hypersthene phenocrysts are 

completely replaced by the celadonite, but the larger 

ones are replaced by it only along transverse cleavage 

cracks whereas their remainders now consist of a 

brownish isotropic substance or a brown fibrous material of very low birefringence. The celadonite also 

forms nan·ow borders around chalcedony and calcite 

grains and forms wormlike traces in the red and upper 

andesites (pl. 12, A). These relations show it to be 

· of late origin and apparently contemporaneous with 

72 Ross, C. S., and Kerr, P. F., The clay minerals and their identity: · 

Jour. Sed. Petrolo'gy, vol. 1, No. 1, p. 58, 1931. 

'7a Von Giimbel, C. W., Ueber die Griinerde vom Monte Baldo: K. bayer. 

Akad. Wiss. Sitzungsber., vol. 26, p. 548, 1896. Clarke, F. w·., The data 

of geochemistry : U. S. Geol. Survey Bull. 770, pp. 520-521, 1924. Ross, 

C. S., The optical properties and chemical composition of glauconite: 

U. S. Nat Mus. Proc., vol. 69, Art, 2, p. 15, 1926. 

the silicification and calcitization or even later. 

Neither the origin of the montmorillonite-beidellite 

minerals nor that of the celadonite is clear. Both 

minerals are usually regarded as products of normal 

surface alteration, but, as the groundmass of the host 

rock shows none of the usual signs of general alteration 

or weathering, they are believed to have been deposited 

by hot solutions. Although it has been impossible to 

separate these alteration products cleanly for chemical 

analysis the ·recorded compositions of montmorillonite, 

beidellite, and celadonite suggest that th~ less stable 

minerals of the andesite were attacked by water containing potash, which could react with hypersthene and 

form celadonite ··and the potash-magnesia,.bearing type 

of montmorillonite and could convert plagioclase also 

into montmorillonite. That these products were 

formed instead of sericite and chlorite implies that 

alteration took place close to the surface at moderately 

low temperature. 

STRUCTURE 

SUMMARY OF DEFORMATION 

The outstanding structural features ·of the district 

are the faulted homoclinal masses that constitute the 

mapped part of the Magdalena Range and the Granite 

Mountain are~. Their development, as shown by local 

evidence, has been rather complex, and as the forces 

involved must have _been active throughout a large 

region, interpretation of them should be based on 

detailed studies at several places; but such detailed 

studies outside of the Magdalena district ·have been 

few, and in much of the region structural features 

are so thoroughly concealed that any interpretation 

must be partly conjectural. Structural features will 

be considered in chronologie order, and conclusions regarding processes of deformation and their practical 

significance will be drawn with full realization that 

they have still to be subjected to regional correlation. 

A general summary of the major events of deformation will first be given. Descriptions of local structural 

features will then be given, and they will be followed by 

an interpretation of the Laramide and later deformation that produced the principal structural features of 

the district. Plates 2, 4, and 20 will be found useful in 

following the discussion. 

Pre-Cambrian deformation included the tilting or 

isoclinal folding of the argillite and successive . intrusions of gabbro, felsite, granite, and diabase dikes. 

Many minor fractures in the pre-Cambrian rocks do 

not continue into the overlying Kelly limestone, thus 

sugge~ting that they are of pre-Cambrian age; but the 

only pre-Cambrian fractures that can be recognized 

with any assurance are those that contain pre-Cambrian 

dikes and veins. Insofar as fractures in the pre-Cam-

. brian coincide with those in younger formations they 

. may be younger than the pre-Cambrian, or the pre-
56 MAGDALENA MINING DISfrRICT, NEW MEJX!CO 

Cambrian structure may have influenced fracturing of 

the younger rocks. 

Structural features formed in Paleozoic time are not 

conspicuous. They include only local minor folds and 

minor erosional unconformities within the Sandia 

formation and betwe~n the Madera limestone and Abo 

sandstone. Their influence on present structure, if 

any, is slight. As no Mesozoic formations are present 

within the district, no record of deformation during 

this era is available. 

During 'the Laramide revolution, when folding and 

overthrusting were taking place in the surrounding 

region, the sedimentary and underlying pre-Cambrian 

rocks were subjected to easterly compression, which 

produced a gentle flexure and some minor reverse and 

bedding faults, initiated major longitudinal and 

transverse faults, and elevated and tilted the whole 

district represented . by the .main Magdalena Range and 

Granite Mountain. After this compressive movement 

subsided, the uplifted mass was subjected to the first 

stage of gravitative adjustment, during which the first 

major movement occurred along the east-dipping faults. 

The sliding of blocks along these faults involved additional westerly tilting. Where movement along them 

was rapid, subsidiary faults with nearly vertical dips 

were formed ; and the blocks between them and the 

related east-dipping faults sank below the surrounding . 

blocks. The adjustment also involved movements 

along major transverse faults. During and after this 

early period of deformation the country was subjected 

to erosion, the tilted formations were beveled, and the . 

surface was reduced to one of low relief. 

The first period o:f volcanic eruptions, represented by 

the latites, lower andesites, banded rhyolite, and red 

andesite, followed; and lavas and tuffs unconformably 

covered the sedimentary rocks. · 

The major stage of tilting followed, and the Magdalbna Range was evidently uplifted and tilted westward, 

presumably along a profound longitudinal fault east 

of the area mapped. Tilting was presumably accompanied or closely followed by collapse along east-dipping faults. Great slabs settled eastward and became 

still more steeply tilted along the east-dipping faults 

within the range. The rocks of the second volcanic period, represented mainly by the upper andesite and pink 

rhyolite, were deposited unconformably on the older 

volcanic rocks. The second volcanic period ended with 

the intrusion of rhyolite porphyry. 

The principal stage of vertical faulting followed 

the second volcanic period and probably intensified 

sume of the earlier movements. Tilting, however, was 

slight during this stage of deformation. It was accompanied by production or further depression of local 

downfaulted blocks. Downfaulting also took place 

between favorably situated transverse faults. By far 

the greatest amount of downfaulting involved the 

western part of the present Magdalena Range and the 

valley west of it. 

The intrusion of the monzonite and granite stocks 

that followed took advantage of fault intersections, 

particularly along the margins of the .great downfaulted area. Subsequent movement was small. Soon 

after emplacement of the stocks, settling of the major 

fault blocks locally reopened the faults along their 

margins and opened fissures or minor faults within 

them, which permitted the intrusion of lamprophyre 

dikes. Somewhat later, further adjustment was accompanied by movement along bedding planes, which 

locally offset the lamprophyre dikes. The white rhyolite dikes were intruded after those of lamprophyre, 

but their relations to these bedding faults have not 

been determined. Still further adjustments, particularly along the vertical fault zones that border the 

greatest depressed areas and along subsidiary oblique 

and transverse faults, gave access to ore-forming 

solutions. 

Faulting again took place after ore deposition. This 

latest stage of faulting, expressed by at least one fault 

scarp along the northeast base of the range, involved 

only trivial movements and caused the fracturing and 

slickensiding of ore deposits within the district. The 

dominant .geologic process since ore deposition has been 

erosion, which will be considered on pages 73-75. 

PRE-CAMBRIAN STRUCTURE 

The deformation in pre-Cambrian time was conveniently considered in the descriptions of the preCambrian formations. It involved the tilting or close 

folding of the argillite, the intrusion of gabbro and 

felsite, the subsequent intrusion of granite whose upper 

surface was about normal to the dip of the argillite, 

the fissuring of the granite and older rocks, the intrusion of diabase dikes, and the erosion to a surface of 

low relief. The pre-Cambrian rocks are much fractured, but the only fractures that can be assigned to 

pre-Cambrian deformation with any assurance are 

those filled. by pre-Cambrian dikes and by veinlets of 

minerals attributed to deposition at the close of preCambrian igneous activity. To what extent pre-Cambrian structure may have influenced lat-er deformation 

is not clear. 

PALEOZOIC AND MESOZOIC STRUCTURE 

Structural features formed in Paleozoic and Meso~ 

zoic time are not conspicuous and have been conveniently considered in the description of sedimentary 

rocks. They include minor unconformities in the 

Sandia formation, which are largely results of sedimentation, although a little deformation may also 

have been involved. The unconformity between the 

Mad era limestone and the Abo sandstone more clearly 

indicates some deformation, which is also suggested 
LARAMIDE AND TERTIARY STRUCTURE 57 

by the fact that local minor folds or undulations 

shown in the Madera limestone south of Chihuahua 

Gulch are not represented in the Abo sandstone close 

by. These folds, however, are too local to be satisfactorily interpreted, as any development of them prior 

to deposition of the Abo sandstone may have been 

modified. by subsequent warping and . faulting. Thy 

lower Sandia beds in the long, slightly downthrown 

block near the southeast corner of the district suggest 

a minor anticline with a southerly pitch, but 'vhether 

this deformation was earlier or later than the deposition of the Abo sandstone is not known. . 

As no Mesozo~c formations have been found within 

the district, there is no record of deformation since 

the deposition of the Abo sandstone and before the 

great Laramide upheaval that marked the transition 

from Mesozoic to Cenozoic time. Any minor movements, like those cited in the preceding paragraph, 

may have contributed slightly' t9 the present structure, 

but their effects have been completely masked by later 

tllting, faulting, and local crumpling. 

LARAMIDE AND TERTIARY STRUCTURE 

The principal structural features of the district are 

referred to Laramide and Tertiary time, during which 

deformation too)r place on a large scale throughout the 

West; but inability to determine precisely the age of 

any of the post-Permian formations prevents the 

assignment of local deformation to any definite period. 

The most conspicuous structural features are the homoclinal fault blocks that compose the Magdalena Range, 

shown by the discordant relations of the formations ; 

but the distribution and trends . of the sedimentary 

rocks and the unconformities that separate thmn from 

the volcanic rocks indicate that some doming or folding 

preceded the principal stages of faulting. 

FOLDS 

No clearly defined folds are present within the dis-

- trict, and minor undulations that have been noted may 

have been formed in Paleozoic rather than Laramide 

time (p. 56) ; but the entire district may represent part 

of a major fold. 

Volcanic rocks rest upon Abo sandstone south of 

Kelly, but farther north along the east base of Stendel 

Ridge they rest upon the Sandia formation. The base 

of the volcanic rocks in the intervening area has been 

concealed by faulting, but, as the Madera limestone is 

present there, it is evident that the volcanic rocks overlapped northward m a beveled ero.sion surface and 

that more prevolcap.ic erosion had taken place at Stendel Ridge than farther south. In the Granite Mountain area the basal volcanic rocks overlap southward 

fron1 Madera limestone onto the Sandia formation, and 

prevolcanic erosion must have been grea_ter in the 

southern part than in the northern part of that area. 

200889-42-5 

These differences in the amount of erosion, together 

with the general strike of the sedimentary rocks, which 

changes from about N. 15° W. in the main range to 

N. 30° E. in the Granite Mountain area, indicate that 

the rocks had been ·arched or bowed and that the cen-

- tral part of the bo~ had been beveled by erosion in 

prevolcanic time. · · ' 

This arch has been obscured by faulting, by erosion 

of the sedimentary rocks from . the eastern part of the 

district, and by a cover of volcanic formations and 

alluvial deposits, which have concealed the sedimentary rocks in much of the western and northern 

parts of the district. 

Farther northeast two of the three small outcrops in 

the arroyo just south of La Jertze Creek, near the northeast corner of the district, strike eastw~rd and dip north-

. ward. This strike and dip show a .marked increase in 

the curvature of the formations and suggest that the 

nortliern end of the Granite Mountain area is the 

porthward plunging nose of an anticli~e; but the relations of these outcrops to one another and to those· in 

the main Granite Mount~in area, evidently because of 

faulting, are too discordant to be used as a reliable 

basis for the interpretation of structure. In fact, the 

prevolcanic structure here is even more obscure than 

in the district as a whole.· In spite of this obscurity, 

however, the available local evidence, together with 

our know ledge of the surrounding region, is in keeping 

with the suggestion that the prevolcanic rocks were 

arched into an elongated dome or anticline of northerly 

trend, only the westerly, bow-shaped limb of which is 

within the area mapped. Similar anticlines are present , 

in many parts of the State and are typified by the 

Sandia Mountains. 74 The positions and attitudes of 

certain local faults, to be described later, suggest that 

these faults were produced by the same forces that 

produced the folds, although later recurrent movements have taken place along some of them. 

FAULTS 

Faults of' mode~ate to vertical dip that crosscut sedimentary and adjacent igneous rocks are shown on 

plates 2 and 20. Most of these are normal faults, .but 

some are reverse. There are also many faults along 

the bedding and at least a few reverse faults with moderate dips that are difficult to recognize except in mine 

workings. The crosscutting faults form two main 

groups-longitudial 'faults with northerly trends and 

transverse faults with northeasterly to easterly and exceptionally southeasterly trends. Each group is divisible into two subgroups, which dip ·in different 

directions. There are doubtless many representatives 

of each subgroup within the ·more extensive igneous 

forinations, especially the volcanic rocks, but only those 

actually recognized are shown on plate 2. The few 

7' Darton, N. H., Tectonics of Arizona and New Mexico [abstract] : 

Geol. Soc. America Bull., vol. 39, p. 182, 1928. 

I' 
58 MAGDALENA MINING DISTRICT, NEW MEXICO 

reverse faults that are definitely known have dip slips 

of only 50 or 60 feet and may be related to certain bedding faults whose attitudes suggest a reverse movement. 

The bedding faults, where recognized, however, afford 

little or no opportunity to appreciate the amount of 

displacement along them, except in those mine workings where they have offset dikes, and there the movement has been normal. In some places, however, they 

have exerted an appreciable control over ore deposition. 

The relations of the different groups are such that it 

is best to base descriptions primarily on areas and secondarily on groups of faults. Certain major and minor 

faults and fault blocks are conveniently referred to 

by appropriate names. 

FAULTS SOUTH OF THE NITT STOCK 

The longitudinal faults south cf the Nitt stock 

comprise two sets, one dipping eastward at moderate 

angles and the other dipping vertically or very steeply 

to the west or east. · As a whole they lie mainly in a 

broad zone that appears to diverge northward from 

an area south of the district; the apparent divergence 

in trend is partly caused by the angles at which faults 

with moderate dips meet the sloping surface and partly 

by the widening belt of sedimentary formations, in 

which faults are more easily recognized than in the 

volcanic formations. 

The transverse faults also comprise two sets, one 

dipping southward and the other northward. The 

largest of them lie west of the diverging zone of longitudinal faults, but a conspicuous group has been 

mapped on the southwest slope of Tip Top Mountain 

within the most divergent part of the longitudinal 

zone. Others of small to considerable extent lie east 

of the longitudinal zone and within it. 

Some of the minor transverse faults end against 

longitudinal faults and are so -related to curves in the 

longitudinal faults as to be attributed to local strains 

induced by movement along them. 75 Some longitudinal faults, however, regardless of their dips, terminate 

against transverse faults or are interrupted by them. 

A study of the faults as a whole forces the conclusion 

that they were formed chiefly in three well-defined 

stages before the intrusion of the stocks. East-dipping 

longitudinal faults dominated in certain places, steeply 

dipping or vertical faults in others, and transverse 

faults in still others. At a few places, particularly 

near the southern contact of the Nitt stock, longitudinal 

faults appear to be offset by transverse faults. This 

suggests a later, relatively local disturbance during 

which movement along the transverse faults dominated. As the movement in general involved adjustments of the different major and minor blocks, the 

amount of slip along any major fault commonly 

'15 Lasky, S. G., Transverse fractures as coordinate structures: .Am. 

Jour. Sci., 5th ser., vol. 19, pp. 451-462, 1930. 

changed at intersection with other major or minor 

faults. The movements were dominantly down the 

dips of the fauJts, but movement down moderately 

dipping faults involved an appreciable amount of 

movement along the strike of relatively transverse 

faults. 

EAST-DIPPING LONGITUDINAL FAULTS 

The east-dipping longitudinal faults or fault zones 

form a group with an imperfect steplike or en echelon 

arrangement, which is obscured by terminations against 

major transverse faults. The three members of this 

group that are ·most clearly defined on plates 2 and 

20 are the Germany, Stonewall, and Crest fault zones. ·· · 

West of the Germany fault zone are other east-dipping 

faults, identified only in mine workings, whose positions accord with the steplike arrangement insofar as 

they are exposed, but they may have been formed 

wholly or in part during later disturbances than those 

that formed the well-defined zones. North of the Nitt 

stock the Stendel fault, which has been partly obliterated by the monzonite intrusion and is partly concealed beneath alluvium, evidently dips eastward also 

and may conform to this steplike arrangement. 

Gerrrnany fault zone.-The Germany fault zone includes the Germany fault and its branches and a group 

of faults that is approximately in line with it as far 

north as Oa,k Spring. These faults collectively form a 

zone whose members are connected by transverse faults 

and show a marked downthrow to the east. The connection, however, is locally obscured by vertical longitudinal faults with downthrow to the west. 

The Germany fault itself, which is cut by the lower 

Germany tunnel, is the most conspicuous of the major 

faults that dip eastward at mo<Jerate angles. It forms 

the e~st boundary of the relatively uplifted block of 

pre-Cambrian rocks east of Kelly, and the easterly 

dip along most of its course is clearly expressed by 

its outcrop on the sloping surface. The dip in the 

lower Germany tunnel is 40° E. Its maximum amount 

of displacement is along its southernmost part just 

north of Chihuahua Gulch, where the Madera limestone lies opposite pre-Cambrian argillite. The fault, 

, .. however, ends abruptly against a concealed transverse 

fault at Chihuahua Gulch. Only a minor fault with 

clownthrow on the west lies along the southward projected course of the Germany fault. 

North of Chihuahua Gulch the amount of displacement along the Germany fault decreases progressively 

at intersections with minor transverse faults. At the 

Germany mine, where a local minimum of displacement is shown, the strike of the fault changes from 

north to north-northwest, but the amount of change 

is exaggerated by the topography. At Kelly Gulch the 

fault branches into a diverging group of step faults, 

but near the Grand Tower mine, between the main fault 
LARAMIDE AND TERTIA'RY STRUCTURE 59 

and its nearest branch, local dropping of a block within · 

a network of minor faults has brought Madera limestone opposite Kelly limestone. A little farther north 

the downthrow is small, and beyond the junction with 

a short cross fault, at the Tip Top road, the true Ger- · 

many fault cannot be recognized. The fault dir~ctly . 

in line with it, and therefore likely. to be regarded at 

first as a part of it, is one of the vertical or steeply dipping set. It forms the east boundary of a downfaulted 

block in which the actual continuation of the Germany 

fault may be concealed. 

About 800 feet to the northwest, however, the Madera 

limestone forms the east wall of a fault that separates 

Madera from the lower part of the Sandia formation. 

This fault, where cut by the Mitchell tunnel, dips 32° 

E. and records a marked drop to the east corresponding 

to that along the Gei~many fault. It ends abruptly, 

both to the south and the north, against major transverse faults, but an equivalent fault to the northeast, 

interrupted by transverse faults; separates Sandia and 

Madera beds from argillite. Minor branches of it 

extend northward into the argillite, but the outcrop 

of the main fault curves rather sharply down the slope 

to the Sleeper tunnel, near which it shifts to the east 

along another transverse fault and continues to a point 

northeast of Oak Spring. From there northward it 

rapidly diminishes and becomes lost in the large area 

of felsite. 

A ·major branch of the Germany fault, named the 

Sampson fault, extends northward through the Grand 

Tower and Sampson claims. Opposite the intersection 

of the Germany fault with the Tip Top road, where 

the throw along the Germany fault is negligible, the 

throw along the Sampson fault increases markedly at 

its junction with a transverse fault. North of the 

Sampson claim the Sampson fault curves westward 

and is concealed beneath a considerable area of debris. 

· It may follow the lower quartzite member of the Sandia 

formation down the slope, or it may trend northward 

and merge into a transverse northward-dipping fault 

that is obscured by the debris-covered surface but that 

extends northwestward down the slope for 1,000 feet 

and joins the northerly continuation of the Germany 

fault. Both suggestions are indicated on plate 2. 

Stonewall fawlt zone.-The Stonewall fault zone includes the Stonewall and South Stonewall faults i nd. 

associated transverse faults, two of which connect the 

zone with the Germany fault zone. It roughly parallels the main Germany fault but is obscured where it 

changes from a northeasterly to a northwesterly course. 

Displacement along it is much less than along the Germany fault. The South Stonewall fault dies out 

southward near the Mistletoe mine and half a mile 

southeast of the south end of the Genpany fault. 

From its south end it trends north-northeastward 

nearly to the crest of the range, and its dip slip gradually attains a maximum of 150 feet or more where the 

lower quartzite of the Sandia formation is faulted 

against pre-Cambrian granite. This displacement is 

abruptly increased between two rather closely spaced 

transverse faults that cross the crest of the range and 

enclose a small downfaulted block. Beyond this small 

block the fault has been obscured· by the removal of the 

sedimentary rocks, but it may coincide in part with the 

steep upper east slope of the Magdalena Range, and it ' 

may also have been shifted eastward along one of the 

transverse faults, as shown on plates 2 and 20. The 

Stonewall fault begins about 800 feet farther north, 

at another cross fault. A little farther on it is joined 

without deflection by a south-dipping cross fault that 

trends southwestward down the west slope and either 

joins another east-dipping longitudinal fault or curves 

into a longitudinal position. This longitudinal fault 

ends against one of the transverse 1nembers of the 

Germany zone· and forms a connecting link . between 

the Germany and Stonewall zones. 

The Stonewall fault zone, which decreases abruptly 

in dip slip beyond its junctions· with the transverse 

faults on its east side, curves to a northerly course, as 

shown by its exposure in the Stonewall workings. 

There its dip is 45° E. and its dip slip is no more than 

100 feet, but the only accessible place in the district 

where enriched gold ore has been mined is in a winze 

along a minor member of this fault zone. Beyond the 

next transverse fault the dip slip increases to about 

350 feet, and a little farther north the Stonewall fault 

becomes lost in the transverse fault zone of Tip Top 

Mountain. This transverse zone has a north downthrow and may extend westward to the junction of the 

Sampson fault with the northern part of the. Germany 

fault zone, but it has not been traced throughout this 

distance because of vegetation, debris covering, and 

the absence of distinctive beds in the Madera limestone. 

Crest fault.-The Crest fault extends along the crest 

of the range for nearly 4,000 fe~t, east of the Black 

Cloud and Mistletoe mines, and its northern continuation has been traced along the east slope for nearly a 

mile, to a point where it _passes beyond the east 

boundary of the area mapped. The Crest fault, like 

the South Stone~all fault, dies out southward, but at 

a place about. 1,500 feet farther southeast. The south 

ends of these two faults and the Germany fault li~ 

almost in a straight line that trends N. 45° W. 

The dip of the Crest ·fault, as shown by the peculiar. 

abrupt bend in its course east of the Mistletoe mine, 

is about 25° E., and the footwall of the fault coincides 

with the presBf!t east-sloping granite surface. The dip 

slip, which is very small to the south of the bend, is 

abruptly increased to 450 feet or more at the transverse 

fault just to the north. It diminishes considerably at 

the second transverse fault, increases agahi to about 
60 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

650 feet at the fourth, and increases about 150 feet more 

at the fifth fault. Between the last two of these faults 

the crest of the range turns slightly westward, and the 

gently dipping Crest fault extends northeastward down 

the east slope. Displaced diabase dikes along its 

northernmost part indicate dip slips of 150 feet or more. 

The Crest fault is flanked on the east by several short 

east-dipping faults that end against the transver~e 

faults. ~ 

Other east-dippvng fmults.-Besides the three major 

fault zones described above, there are many other eastdipping faults of small to moderate size that have 

escaped detection on the surface but are shown by 

different mine crosscuts. Level 10 of the Kelly mine 

(fig. 15) shows four between tlle Traylor shaft and the 

Waldo fault within a distance of 1,100 feet; and higher 

workings between the Traylor shaft and the KellyGraphic fault show four more. These faults, all within 

the Kelly fault block, have downthrows to the east 

and evidently end northward against the Kelly-Graphic 

cross fault, whose throw, accordingly, diminishes w~stward and becomes small or negligible before the Waldo 

fault is reached. The larger of these east-dipping 

faults may have originated at the same time as the 

major east-dipping faults, but some of them at least 

appear to be local and to have been formed by adjustment of the Kelly fault block along the major faults 

that bound it. Similar east-dipping faults are exposed 

in the Graphic-Waldo mine (pls. 31 and 32) and · 

others in the Mistletoe and Linch burg tunnels (fig. 

18). They are normal faults, with few exceptions to 

be considered presently, and although they are of premineral origin, very little ore has been found along 

them; however, the main ore body of the Grapic-Waldo 

mine lies along one of them, ca.lled the "roll" fault, 

which was evidently formed by adjustments within 

the Graphic block. These adjustments will be considered later. 

The distribution of the· three major zones. of eastdipping faults in the main range justifies the opinion 

that there may be other faults of similar size, but less 

readily recognized or traced, farther east in the granite 

area. Interpretation of the structure must, therefore, 

be based on very incomplete evidence. Bryan 76 reports 

a fault scarp along the east base of the Magdalena 

Range, presumably with easterly dip, where rather 

recent uplift has taken place; but no noteworthy movement since ore deposition has been noted along any of 

the eastward-dipping faults within the Magdalena 

district. 

VERTICAL OR STEEPLY DIPPING LONGITUDINAL FAULTS 

Kelly-G-1v;r;phic fmult.-The Kelly-Graphic fault, 

which forms the approximate east limit of explored 

ground in the Kelly and Graphic-Waldo mines, is the 

16 Br.yan, Kirk, oral information, 1933. 

most familiar of any ·of the faults in the district. It 

belongs to a steplike and branching group of faults 

in a zone that extends southward beyond the south end 

of the district and coincides with the main ore zone. 

Mineralized faults throughout this zone have been 

referred to by some as the Kelly-Graphic fault, but 

structural relations are such that it is more consistent 

to restrict that name to the fault that forms the east 

. wall of the Kelly and Juanita ore bodies and to apply 

local names to the other faults of the zone. The zone 

as a whole, however, is conveniently designated the 

Kelly-Graphic fault zone, after the two largest mines 

along it. It coincides with the main ore zone of the 

district. 

The Kelly-Graphic fault has an average strike of 

N. 20° W., and its dip where exposed ranges from 

vertical to 80° E. Its northernmost part curves to a 

northerly course and even branches to the northnortheast, but because of the scarcity of mine workings 

here its relations to other faults are obscure. At the 

Tip Top road it joins a short transverse fault that 

forms the south boundary of a downfaulted block and 

connects with the Germany fault. This transverse 

fault evidently marks an abrupt easterly deflection of 

movement, which resumed its northward course along 

the fault with west downthrow that is in line with the 

Germany fault and is exposed underground near the 

breast of the Mitchell tunnel. If the. Kelly-Graphic 

fault continues northward without deflection beyond 

the transverse fault it is lost in the shale member of 

the Sandia formation. Beyond the shale and in line 

with the Kelly-Graphic fault there is a fault that 

separates Madera limestone from the lower limestone 

member of the Sandia formation, but it has a much 

greater throw than the Kelly-Graphic fault and ends 

to both the north and the south against transverse 

faults. 

In the Kelly mine the Kelly-Graphic fault is flanked 

on the west by two nearly parallel faults that dip 

steeply west. The longer of these, called the Brown 

fault, and the Kelly-Graphic fault converge southward; 

but the Brown fault practically- ends against a transverse fault that is concealed by alluvium. It also 

curves to a northerly course, along which mine development has been discouraging, and becomes lost in shale. 

Movement along it may have been absorbed by the 

flexible shale; if not, the Brown fault ends against the 

major transverse fault known as the Kelly-Graphic 

cross fault. Beyond this the east-dipping fault cut by 

the Mitchell tunnel and regarded as a part of the Germany fault zone is approximately in line with the Brown 

fault. 

- The Kelly-Graphic and Brown faults as seen underground are connected by a few minor transverse faults 

or fissures that have aided in the thorough replacement 

of limestone by the ore in the Kelly mine. These do 
·, 

I LARAMIDE AND TERTIARY STRUCTURE 61 

not appear in plates 2 or 20 but are shown on the map . 

of the Kelly mine (pl. 36). Another mino:r :fault, 

almost in line with the Brown fault, is exposed to the 

south in the Juanita tunnel but has escaped notice on ' 

the surface, where both of its walls are quartzite. It 

also is connected with the main Kelley-Graphic fault 

by mineralized cross faults, one of which has brought 

the Kelly limestone to the surface along its south wall. 

Farther south two other transverse faults, but with 

downthrow to the south, extend westward from the 

Kelly-Graphic fault, whose throw is accordingly 

increased. · 

South of these faults-well-shown in the South 

Juanita mine but not so well-shown on the surfacethe Kelly-Graphic fault curves to a more southeasterly 

course and evidently abuts against the Germany fault. 

M i8tletoe · fault.-South of Chihuahu,a Gulch the 

principal fault of the Kelly-Graphic or main ore zone 

is cut near the face of the Mistletoe tunnel and is therefore called the Mistletoe fault. The westerly dip of 

this fault is shown by its curving course down the slopes 

of Chihuahua Gulch. North of the gulch it is somewhat obscured because both of its _ walls are in the 

quartzite members of the Sandia formation, and be-

,yond its junction with a cross fault of northeast trend 

it is entirely within the lower quartzite Inember. 

The principal amount of downthrow shifts to the cross 

fault that extends westward from the Mistletoe fault 

to the Germany fault. I~ short, the downthrown 

ground just north of Chihuahua Gulch forms a reentrant angle bounded by the Germany fault, the cross 

fault of northeast trend, and the Mistletoe fault. 

A little south of Chihuahua Gulch the downthrow 

along the Mistletoe fault is lessened as much as 150 feet 

by uplift along the south side of a short cross fault if 

the quartzite exposed at the junction of the two faults 

marks the top of the Sadia formation; but the exact 

stratigraphic position of the quartzite has not been 

proved. Farther south the fault splits into three parts 

along which the western downthrow is about equally 

distri.buted. The western fork, which most nearly 

maintains the course of the fault, is flanked on the 

west by southward converging faults that recall the · 

Brown fault in the Kelly mine. It is apparently offset by a transverse fault, south of which its downthrow 

is so· increased that purple andesite lies against ~ladera 

limestone. Farther south, just east of the Linchburg 

tunnel, the principal displacement is shift~d eastw~rd 

along two short cross faults to a spur of the middle 

~ork, but the southerly- continuation of the west fork 

is in part represented by a fault in steplike relation 

· that extends beyond the south boundary of the district. 

The continuation is somewhat obscured because the 

northern part of this fault consists of t,wo members 

that enclose an uplifted wedge-shaped block. 

The middle fork of the fault is partly concealed by 

landslide material, beneath which it may be deflected 

by concealed cross faults; but it also has a markedly 

curved course. South of the junction of its spur with 

the two short cross faults mentioned above it is concealed by more landslide material, beneath . which it 

either curves sharply eastward or is deflected by a concealed cross fault. It reappears for a short distance 

south of the landslide, where it separates andesite from 

latite porphyry and is followed by a low -grade vein. 

It evidently ends southward against a cross fault along 

which the ·displacement is in part deflected eastward to 

the Grand Ledge fault; but displacement was in part 

deflected westward also and continued southward along 

a fault between Ma:dera limestone and latite porphyry. 

Young America fault.-The east fork of the Mistletoe fault is conveniently called the Young America 

fault, from the mine whose workings lie along and 

east of it. It is also cut by -the Linchburg tunnel, 

which exposes the base- of the Kelly limestone just 

west of it and therefore shows that the downthrow on 

the west is about 480 feet. The fault is largely covered 

with landslide debris, but its course where exposed is 

about S. 20° E. . South of the Young America m.ine it 

curves southeastward and joins the Grand Ledge fault. 

Grand Led_qe fmvlt.-The. movements that were dispersed southward along the Mistletoe and Young 

America faults became largely concentrated again along 

the Grand Ledge fault, whose northern end is concealed 

beneath landslide material northeast of the Young 

America 1nine. North of its junction with the Young 

America fault its throw is about 150 feet, but south 

of th'e junction it is 400 or 500 feet. A little farther 

south, where · the Grand Ledge fault curves southwestward and is probably joined by a concealed cross 

fault that connects with the middle fork of the Mistletoe 

fault, its throw is 550 feet or more, which brings the 

base of the Madera limestone opposite · the top of the 

Kelly limestone. At the· Grand Ledge tunnel it resumes a southerly course, and beyond the next west 

cross fault its throw has increased to about 900 feet. 

South of tl~e Connelly tunnel it curves to a southsoutheast course, and the principal displacement shifts 

first eastward along a short cross fault and then southsoutheastward again along a reverse fault that dips 

60° e~st-northeast where exposed in the West Virginia 

tunnel. · This distinctly reverse attitude of the fault 

zone is exceptional and is thought to be a local 

irregularity. 

East . Slope fault.-.The East Slope fault crosses the 

crest of the range near the southeast corner of the 

district. It converges southward with the Grand 

Ledge fault and the two may joi~ beyond the south 

boundary of the district. · If so the East · Slope fault 

!nay be regarded as a branch from the Kelly-Graphic 

fault zone. It extends. northward along the upper east 

slope for a long distance and has a west downthrow. 
62 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

which increases or decreases somewhat at its intersections with minor cross faults. Its relation to the 

southern part of the east-dipping Crest fault is like 

that of the Mistletoe fault to the southern part of the 

Germany fault, the two . pairs of faults bounding 

broken, down thrown blocks; furthermore, the two 

faults with west downthrow extend much :farther 

south than those with east dowhthrow. 

Waldo fafUlt.-The Waldo fault, cut by the Waldo 

tunnel, is the principal representative of· a zone here 

called the Waldo fault zone that lies west of the 

Kelly-Graphic or 1nain fault zone and coincides with 

the little developed n1ineralized zone that extends along 

the base of the range as far as South Camp. This 

west fault zone and the Kelly-Graphic zone converge 

slightly to the north and are evidently connected by 

cross faults, the most clearly defined of which is the 

Kelly-Graphic cross fault. · 

As the Waldo fault separates intrusive rhyolite porphyry :from the Madera limestone, it was :formerly 

regarded as an intrusive contact along which a rather 

'vide zone of shattering had developed. The fact that 

dikes of monzonite and late white rhyolite had been 

intruded along it helped to ob~ure its dimensions. 

The driving of the west crosscut on level 10 of the 

Keily mine in 1916, however, disclosed purple andesite 

cut by white rhyolite along the west side of the :fault; 

and core drilling farther north by the Ozark Mining 

& Milling Co. in 1928 showed that the rhyolite porphyry was underlain by latite, which verified the identity of the small outcrop of latite in the gulch 1,200 

:feet southeast of North Camp. The rhyolite porphyry 

along the Waldo fault, therefore, is not an essentially 

vertical or dikelike mass, as had been supposed by 

some, but a west-dipping sill intruded between a roof 

of banded rhyolite and a floor o:f latite and andesite. 

Its upper contact is well-exposed on the low hills 

around North Camp and its lower contact along the 

'"est slope of Stendel Ridge. I£ the entire thickness 

of the underlying volcanic rocks on Stendel Ridge is 

also present beneath the rhyolite porphyry along the 

fault, the throw along the Waldo fault may exceed 

1,200 feet but, owing to the unconformity at the base 

of the volcanic rocks, as well as changes in thickness 

of the volcanic members, this figure expresses only a 

rough estimate. 

The Waldo fault zone is easily traced from the Nitt 

stock, against which it ends abruptly, to. the low saddle 

southeast of North Camp; but its relations to the westernmost part of the Kelly-Graphic cross fault .are 

concealed. As stated on page 60, however, the displacement along this part of the cross fault may be 

small or negligible. In the next gulch to the south the 

fault is clearly exposed, between rhyolite porphyry and 

steeply dipping Madera limestone, but farther south 

where banded rhyolite is in conta~t with the limestone 

the surface is so covered with debris and soil that the 

presence of the fault was not suspected at first. Its dip 

where exposed, either at the surface or underground, 

ranges from vertical to 85° E. 

The fault may be cut beneath the alluvium of Kelly 

Gulch by workings from the Contact shaft, which has 

been inaccessible to us, and it evidently ends against a 

concealed cross fault along which downthrow on the 

south is shown by the discordant relations of the rocks 

on opposite sides of lower Kelly Gulch. Another 

fault must separate the isolated hill just west of Kelly 

from the rhyolites-/west of the Waldo fault, but it is 

uncertain whether it is a cross fault with downthrow to 

the northeast, opposite to that of the fi:mlt beneath 

lower Kelly Gulch, or a longitudinal fault with downthrow to the east, as shown tentatively on plates 2 and 

20. I£ it is longitudinal it may be one o:f the eastdipping faults and may form the west boundary of a 

downfaulted block that is bounded on the east by the 

"\V'aldo fault. 

F~ts between Kelly and South Oamp.-The princi-

·pal fault south of Kelly and due south of the Waldo 

fault separates purple andesite from younger volcanic 

rocks and has a downthrow of 500 to 1,000 feet on the 

west. It is joined and interrupted by conGealed cross 

faults, whose influence on differences in throw is not 

clear. It is also paralleled by at least two poorly exposed longitudinal faults with downthrow to the east 

and presumably with east dip. Only one, a minor 

transverse fault, has bee~ identified south of South 

Camp, although others undoubtedly are present; but 

the irregularities in :formation poundaries there apparently represent unconformable contacts. 

The low rhyolite hill a quarter of a mile west of 

Kelly is evidently separated from the rhyolite area 

nortii:east of it by a vertical or steeply dipping fault. 

This hill may also be separated from the next hill to 

the west by a similar fault, but the thicknesses and succession of the local volcanic rocks are too little known 

to afford estimates of the amount of faulting. There 

must, however, be a major fault between the most westerly of these hills and ~{agdalena Mountain, which is 

1 ~% miles beyond the west ·boundary of the district, as 

each hill is capped with the pink rhyolite and the vertical difference between their altitudes, as determined by 

aneroid, is about 900 feet. Allowance for the westerly 

dip of the rhyolite on the low hill would imply an 

actual displacement of as much as 4,000 feet, although 

the displacement may be distributed and compensated 

to some extent along several faults concealed beneath 

alluvium, as suggested in figure 5. 

TRANSVERSE FAULTS 

Transverse or cross faults have already received somuch consideration in the descriptions of the longitudinal faults that further reference to them may seem 
LARAMIDE AND TERTIARY STRUCTURE 63 

superflous. Attention, however, is called to the distri-' 

bution and throw of the larger ones. The fault zone 

along the west slope of Tip Top Mountain, with a cumulative downthrow of about 500 feet to the north, forms 

· the south bound'ary of a large depressed block, conveniently called the Tip Top block. In contrast the fault 

almost in line with it, which curves northwestward by 

the Graphic tunn~l, has a downthrow of unknown but 

probably -small amount on its southern side and forms 

the south boundary of a block whose relative. uplift is 

the highest in the ,district. To the south the KellyGraphic cross fault and unnamed faults bound blocks 

that are successively downfaulted as far as South Camp, 

beyond which the volcanic rocks are upfaulted. They 

form a series of steps intermediate in altitude between 

the blocks east of the Kelly-Graphic zone and those 

west of the Waldo zone, which are in the large downfaulted area that extends westward to Magdalena 

Mountain. The blocks separated by the transverse 

faults, therefore, may be regarded as the easternmost 

parts of the large downfaulted area. 

BEDDING FAULTS 

Bedding faults have been noted at sever~l horizons 

in mine workings and are doubtless present at several 

others. The most conspicuous is along the "silver 

pipe" bed of the Kelly limestone, which is followed by 

more mine workings than any other horizon. Others 

have been noted along the shale bed at the base of the 

Sandia formation and at several places within the large 

shale member of the formation. Some, so far as exposed, lie along a single bedding plane an'd might have 

been overlooked if they had not offset dikes that lie 

about normal to the bedding. Such faulted dikes, seen 

in the Kelly and Graphic-Waldo mines, are offset as 

much as 40 feet along the dip of the bedding (frgs. 

6 and 7), the upper, or hanging-wall, part of the dike 

moving down dip. Other faults in the ·same mines 

locally swerve from the lower to the upper contact. of 

the "silver pipe" bed and give the ·impression of overthrusts, as if the hanging wall had moved upward, 

although their direction of movement cannot be proved. 

In the southern part of the Graphic-Waldo mine, on 

level 9, a bedding fault (fig. 3) has swerved from the 

base of the Sandia formation down to the top of the 

"silver pipe" bed, thus locally eliminating the entire 

upper Kelly limestone. In the Tip Top-Key mine 

(p. 153) a small reverse offset along the "silver pipe" 

bed is clearly exposed. Bedding faults within the shale 

member of the Sandia formation are well-exposed in 

the Waldo tunnel (fig. 3) and the Ida Hill tunnel: 

Their influence on local differences in thickness of the 

formations is obvious. They also suggest movement 

analogous to local overthrusting. The contrast betwe-en 

apparent overthrusting and proved normal movement 

along bedding faults suggests different directions of 

'II· 

A 

E. 

10 0 20Feet 

FIGURE 3.-Bedding faults in Graphic-Waldo mine. A., Bedding fault at 

top of "silver pipe" · bed, south end oil level 9. Direction of movement 

not clear. B, Sketch of branching fault approximately along bedding 

in shale member of Sandia formation. North wall of Waldo tunnel, 

350 feet east of Waldo shaft. 

movement at different times. This will be discussed 

under the heading "Interpretation of Laramide and 

Tertiary-structure" (pp. 66-72). · 

The distinct reverse faults that crosscut the bedding 

at small to moderate angles are too few and scattered 

to be very significant. Some dip west from 55° to 70°, 

as shown on level 10 of the Kelly mine, and others may 

dip at lower angles. Their dip slips range only from 

about 50 to 70 feet, and it is not known whether they 

represent overthrusting and are to be correlated with 

the inferred overthrusting along bedding planes or 

with the n1argins of blocks to which strike slip along 

the faults has given a reverse aspect. In the Nitt mine, 

where a group of minor northeast-dipping faults is 

normal as a whole, one fault within the group is 

reverse and is attributed ' to such a strike slip. The 

reverse faults that dip 50° or less to the west, however, seem mor.e reasonably regarded as minor results 

of overthrusting; and it may be that if followed they 

would be found to grade upward. into bedding faults. 

FAULTS NORTH OF THE NITT STOCK 

Very few faults have been recognized north of the 

Nitt stock, mainly because the contacts· between formations are largely concealed and because formations 

of uniform character, in which faults are not readily 

recognized, cover relatively large areas; furthermore, 

. the Tertiary · ( ? ) granite and Nitt monzonite stocks 

ar:,e thought to have been intruded in places weakened 

by intersecting fault zones and to have obliterated 

several major and minor faults. If so, the faults 

that cut the Tertiary (?) granite (pl. 2) and doubtless 

the monzonite also, represent moderately late disturbances equivalent to mild renewals of movement along 

the faults and to the development of the "roll" and 

other minor . faults south of the Nitt stock. . Some of 
64 MAGDALENA MINING DISITRICT, NEW MEXICO 

these movements followed the intrusion of lamprophyre dikes; some preceded and others followed the 

intrusion of white rhyolite dikes, and some renewal 

of movement followed the deposition of ore. 

Faults within Tertiary ( ?) granite.-The white 

rhyolite dike that has been traced southward through 

Tertiary ( ? ) granite and monzonite to Oak Sp.ring 

dips east at a moderate angle and is in line with the 

Germany fault zone. Whether it fills a fault or only 

a fissure along which no appreciable movement has 

taken place is not known, but its alinement with the 

Germany fault zone implies at least a slight renewal 

of . the disturbance that produced the east-dipping 

faults. The Hardscrabble fault with northeast trend 

and southeast dip is obliquely trensverse to the white 

rhyolite dike and may have the same relation to the 

dike fissure that the transverse faults elsewhere have 

to the east-dipping faults against which they end. 

Another white rhyolite dike east of Anchor Canyon 

is broken by a pair of cross faults, between which the 

west-dipping dike has been relatively depressed. The 

trend of the dike parallels that of tbe Anchor vein, 

which however, fills an east-dipping fault or fissure. 

Farther north a northwest-trending fault., whose 'dip 

and amount of displacement have not been determined, 

cuts off an aplite dike. 

Older faults· obliterated by the intrusion of Tertiary 

( ~) granite are suggested by the small exposures of 

banded rhyolite northeast of Anchor Canyon. One of 

these faults, of northerly trend, evidently separated 

the rhyolite from. the pre-Cambrian argillite and granite east of it; others of easterly trend separated the 

rhyolite from the pre-Cambrian and Carboniferous formations across the valley to the north. 

Vindicator fault.-The Vindicator fault separates 

I'ertiary ( ? ) granite on the east frmn ~ladera limestone on the west. It is followed by a white rhyolite 

dike and a sulphide vein, has a vertical or steep easterly dip, and is similar in structural relations to faults 

in the l{elly -Graphic and "\~T aldo zones. Its south ward 

continuation is represented by a pyritized fissure zone 

in monzonite along upper Hardscrabble Valley. It 

forms the east boundary of a narrow relatively downthrown block that is largely concealed by alluvium. 

Displacement along the fault cannot be determined 

because no sedimentary rocks are present along its 

east wall. If the pre-Cambrian argillite and felsite 

a short distance to the southeast approximately represent the floor upon which the Kelly limestone was 

deposited, the Madera limestone west of the Vindicator 

fault has dropped 500 feet or more; but this amount 

of displacement, rna y have taken place along a transverse fault that has been destroyed by the granite 

intrusion. The only movements along the Vindicator 

fault for which there is direct evidence obviously took 

place after the intrusion of the Tertiary (?) granite 

stock and before ore deposition and are comparable in 

time to minor recurrences of movement along the KellyGraphic and Waldo faults; however, as both of these 

faults were mainly developed before the intrusion of 

the Nitt monzonite stock, similarity in attitude and 

trend suggests that the Vindicator fault also may have 

originated before the intrusion of the stocks and may 

therefore acount, in part at least, for the subsidence in 

preintrusion time of the block between it an·d the Stendel fault. If so, the western edge of the intruding 

granite stock must have followed the original fault 

Yery closely, as no granite has been found on the west 

side of the present fault, either at the surface or 

underground. 

Stendel fault.-The Stendel fault is completely concealed by the alluvium of Hardscrabble Valley, but its 

presence. is indicated by the discordance between the 

west-dipping altered shale member of the Sandia formation along the east base of Stendel Ridge and the 

Madera limestone near the Vindicator mine. There 

may be a zone of two or more parallel faults instead 

of a single fault. The easterly downthrow suggests 

that this fault or fault zone is one of the east-dipping 

group and forms, with the Vindicator fault, a troughlike structure broken by transverse faults si1nilar to 

that between the Germany and Mistletoe faults. The 

degree of dip, however, and the depth at which the 

Stendel and Vindicator faults meet can be determined 

only by drilling or underground exploration and must 

be considered in the planning of any deep development 

work in this part of the district. The . steep dips 

(55°-70° W.) in the lower Madera strata just west of 

the Vindicator fault and the presence of shale beds of 

the Sandia . formation west of the Stendel fault would 

imply an aggregate dip slip of 1,000 to 1,500 feet along 

the Stendel zone; but dips along the Vindicator fault 

may be partly due to dr~ag, which would decrease the 

displacement correspondingly. 

The thick covering of volcanic rocks that now con· 

stitutes much of Stendel Ridge must have extended far 

to the east and covered the block that is now downfaulted. There may be a remnant of it, concealed by 

alluvium, in the west part of the downfaulted block, as 

suggested on plate 4 (sec. C-C') and figure 4, 0. It is 

possible that some tilting and movement along the Stendel fault began before the volcanic eruptions took place 

and that the fault was covered with volcanic rock, as 

shown in figure 4, A. If so, the erosion interval between 

early faulting and volcanic eruption was sufficient to . 

remove the Madera limestone from the relatively up- . 

lifted area west of the Stendel fault. An alternative 

juterpretation proposes that the volcanic rocks were 

spread over an erosion surface, from the western part 

9f which the Madera .limestone had been removed before any faulting had taken place, and that the Stendel 

fault was formed later near the west limit of the 
LARAMIDE AND TER'I'IARY S'l'RUCTURE 65 

c FIGURE 4._:._Diagrammatic interpretations of structural development in the vicinity of the Stendel and Vindicator faults. Arg, Pre-Cambrian 

argillite; Ck, Kelly limestone; Cslq, lower quartzite, Csll, lower lime stone, Css, shale, members of the Sandia formation; Cm, Madera limestone; Tul, upper latite tuff with Tulf, latite flow; Tgr, Tertiary ( ?) granite; Twr, white rhyolite. dike; Qal, alluvium. 

A. Supposed prevolcanic faulting followed by erosion and later by deposition of volcanic tuffs over the erosion surface, covering a fault 

between the Sandia and Madera formations. 

B. Volcanic tuffs overlapping an unfaulted erosion surf~ce of the Sandia and Madera formations. 

C. Tilting and downfaulting of either A or B followed by the intrusion of Tertiary ( ?) granite arid white rhyolite and by erosion to the 

present surface. Compare plate 4, sec. C-C'. 

' Madera limestone, as suggested in figure 4, B. The 

second interpretation would avoid the necessity of inferring a prevolcanic period of faulting but would depend on the coincidence that faulting happened to take 

place close to the boundary of an eroded formation. 

There is no reason for objecting to a prevolcanic period 

of faulting, although no stronger suggestion of it has 

been found in the main Magdalena Range. Other suggestions of prevolcanic faulting, however, are present 

in the Granite Mountain area. 

FAULTS IN THE GRANITE MOUNTAIN AREA 

Faults in the. low hills east of Granite Mountain are 

clearly exposed for only very short distances. Strike 

faults have been noted at many of the prospect holes, 

. but they are traceable for only a few feet and are 

therefore not shown on plate 2. It is not known 

whether they dip along or across the bedding. One of 

them is within the ICelly limestone near a group of old 

shafts and prospect holes. Another between the Kelly 

limestone and the lower limestone member of the Sandia 

formation is suggested by the absence of the lower 

quartzite member, which intervenes elsewhere, but the 

quartzite member may have thinned m1t between this 

area and its northernmost exposure, which is at Oak 

Spring, nearly 3 miles to the south. Many faults are 

exposed in the shale member of the Sandia formation, 

but none of them can be traced more than a few feet. 

They suggest that the extraordinary thickness of th~ 

shale may have been caused in part by duplication 

of its beds along either bedding faults or crosscutting 

strike faults; however, the relatively great but true 

thicknesses of the , upper limestone and quartzite 

members of the formation suggest that the thickness 

of the shale also may be mainly the result of original 

deposition. 

At least two major transverse fault"i of west-northwest trend and northerly downthrow, though concealed by alluvium, are implied by the discordant posi-· 

tions of the Madera limestone and the upper members 

of the Sandia formation to the southeast of Granite 

Mountain. The fact that neither the lovyer latite, 

·w·hich unconformably overlies both formations, nor the 

volcanic rocks adjacent to it show any corresponding 

offsets indicates that these transverse faults were 

formed before the beginning of volcanic eruptions, as 

was suggested for the Stendel fault. Three other ,concealed faults-two transverse with northeasterly strike 

and one longitudinal with north-northwest strike-are 

implied by the discordant relations between the lower 

andesite and the upper latite at the north end of Granite Mo,untain. These faults are not reflected in the 

rhyolite porphyry on the west and appear therefore 

to be older than the rhyolite porphyry and to ~long to 

the stage of deformation that occurred between the first 

and second volcanic periods. A younger transverse 

fault of east-northeast trend has Qffset the contact 

.-- between rhyolite porphyry and upper latite tuff on 

the north ·slope of Granite Mountain, but no longitudinal faults in the volcanic and intrus~ve rocks of 

the area have been noted. 

INTERPRETATION OF THE LARAMIDE AND TERTIARY 

STRUCTURE 

The wide distribution of the major faults and their 

different relations to rock formations leaves no room 

to. doubt that they were produced by recurrent regional 

disturbances; on the other hand the relations of certain . 

of the minor faults point to local origin during late 

stages of structural development of the district. The 

difficulty of interpretation is increased by the facts 

that faults formed at different times have similar 

trends and dips and that movements along a single 

fault recurred at different times and perhaps in different directions. A general interpretation -of faulting 

therefore can be most consistently presented by reviewing the different stages of regional and local deformation in the order of development; but conclusions regarding .regional mov~ments must necessarily be tentative until a much larger area has been investigated. 
66 MAGDALENA MINING DISfl'RIC'l', NEW MEXICO 

Such a review can also point out the conditions that 

favored or hindered the circulation of ore-forming 

solutions along the differe11t sets of faults. The principal stages of deformation ~o be reviewed involve ( 1) 

folding or doming accompanied by faulting and followed by partial collapse before ·volcanic eruptions 

began, (2) major tilting, and presumably faulting also, 

between the first and second stages of v.olcanic activity, 

(3) major vertical faulting after the second stage of 

volcanic activity, ( 4) local faulting during the intrusion of igneous stocks, ( 5) minor adjustments after 

intrusion but before ore deposition, and ( 6) minor 

adjustments after ore deposition. 

DEFORMATION BEFORE VOLCANIC ERUPTIONS 

It is generally agreed that the different significant 

stages of tilting and faulting in New Mexico and 

adjacent parts of Texas, Colorado, and Arizona took 

place · during and immediately after the Laramide 

revolution, which marked the transition from Cretaceous to Tertiary time. 77 Only 20 miles northwest of 

the district Winchester 78 found that Cretaceous rocks 

were moderately folded and faulted, whereas the Tertiary J)atil formation which unconformably overlies the 

Cretaceous, is practically horizontal 79 though faulted. 

The different kinds and degrees of deformation in 

neighboring parts of New Mexico are illustrated by 

Darton.80 Gentle and sharp folds, overthrusts, transverse or tear faults, and longitudinal normal faults 

were produced. The absence of well-defined folds and 

overthrusts in the Magdalena district is an obstacle to 

thorough correlation, but as they were produced in surrounding areas it may be inferred that the compressive 

forces that produced them were active to some degree 

during the earliest stages of deformation in the 

Magdalena district. · 

Mild folding in the district during prevolcanic time 

is suggested by the northwesterly strike of the sedimentary formations in the main range and their northeasterly strike in the Granite Mountain area and by 

the beveled erosion surface on which the oldest volcanic 

rocks lie. 

The westerly tilting of the sedimentary rocks presumably began during the early stage of compression, 

and the minor west-dipping reverse faults, as well as 

11 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., op. cit., pp. 

32-33, 1910. Ross, C. P., Aravaipa and Stanley mining districts, Ariz. : 

U. S. Geol. Survey Bull. 763, pp. 40-41, 51, 1925. Lovering, T. S., 

Geologic history of the Colorado Front Range : Colorado Sci. Soc. Proc., 

vol. 12, pp. 93-94, 1929. Burbank, W. S., Revision of geologic structure 

and stratigraphy in the Ouray district of Colorado and its bearing on 

ore deposition : Colorado Sci. Soc. Proc., vol. 12, p. 209, 1930. Burbank, 

W. S., and Goddard, E. N., Problems of structure and stratigraphy in 

the Sangre de Cristo Range, Colo. [abstract] : Geol. Soc. America Bull., 

vol. 43, p. 168, 1932. King, P. B., oral information regarding Marathon 

Basin, Tex., 1933. Richardson, G. B., U. S. Geol. Survey Atlas, El Paso -

folio (No. 166), p. 9, 1909. 

1s Winchester, D. E., Geology of Alamosa Creek Valley, Socorro 

County, N. Mex. : U. S. Geol. Survey Bull. 716, pp. 4-5, 9, 1920. 19 Idem, p. 9. 80 Darton, N. H., "Red beds" and associated formations in New Mexico: U. S. Geol. Survey Bull. 794, 356 pp., 1928. 

some bedding faults and transverse faults, could have 

developed .at the same time. If so, the rocks within 

the district formed only a small part of an anticlinal 

structure that extended beyond the limits of the present 

mountain range. At the end of the period of .compression a general collapse of the anticline took place and 

the east-dipping :~fOrmal faults were initiated. The 

movement along them involved westward tilting, as 

shown in figure 5. Some faults died out in one or both 

directions, whereas others stopped at one or both ends 

against older transverse faults. 

It may be argued that the influence of early compression is not necessary to explain the faulting and 

that the tilting of strata and the formation of transverse faults and longitudinal east-dipping faults may 

be attributed entirely to local uplift accompanied or 

closely followed by colhtpse and adjustments within 

the major blocks. We have no serious objection to the 

interpretation, although t.he minor west-dipping reverse 

faults are not so ·readily explained. According to 

either interpretation, the collapse involved the relative 

dropping of a large mass east of the district, and probably east of the range, and the eastward slumping of 

the range itself along the east-dipping fault&;, as shown 

in figure 5. Owing to the moderate to low angles of 

dip along these faults, gravity must have pressed their 

hanging walls tightly against their footwalls. 

If this interpretation is extended to include faults as 

far west as Magdalena Mountain it may imply that the 

mass comprising the present main Magdalena Range 

and the valley west of it were tilted in one direction 

and that the tilting was accompanied or closely followed by faulting. 

That some transverse and perhaps longitudinal faulting took place before volcanic eruptions began is 

strongly suggested by the transverse faults concealed 

by alluvium southeast of Granite Mountain, where 

large displacements of sedimentary rocks are not reflected in the adjoining oldest members of the volcanic 

group. Prevolcanic faulting in the main range is suggested less strongly by the Stendel fault. The greater 

dips of sedimentary rocks than of adjacent volcanic 

rocks and the general unconformity at the base of the 

volcanic group throughout the district also point to 

some tilting, as well as faulting, before volcanic eruptions began. More must be known about the area north 

of the main range and east of Granite Mountain before 

any further inferences regarding prevolcanic folding, 

tilting, faulting, and erosion are justified. 

DEFORMATION BETWEEN THE FIRST AND SECOND STAGES OF 

VOLCANIC ACTIVITY 

The major amount of tilting occurred between the 

first and the second stages of volcanic activity. It was 

doubtless accompanied by faulting, as faults that offset 

the older but not the younger volcanic rocks are indicated north of Granite Mountain; but no such faults 
LARAMIDE AND TERTIIARY STRUCTURE 

have been recognized within the main range. The volcanic rocks of the first stage, represented by the latites, 

lower andesites, and banded rhyolite in general, dip 

at angles ranging from 30° to 40°, whereas the rocks 

of the second stage, represented mainly by the upper 

andesite and pink rhyolite, are nearly horizontal. The 

dips of the sedimentary rocks commonly range from 

30° to 55°, though local dips may be smaller or greater, 

indicating that the amount of tilting at the beginning 

of volcanic activity was probably small, locally not 

more than 10° to 20° (pl. 4, sec. C--C'). 

Just what structural features resulted from this 

intravolcanic deformation-whether asymmetric folds 

or uplift along major faults east of the area-is not 

known. The greater part of the east slope of the 

:Magdalena Range falls outside of the area mapped·, 

and relatively little is known of this part of the range; 

but, because of its importance relative to the structure 

and origin of the range, the information at hand will 

be discussed here. The east slope of the range east · 

of the area mapped is composed almost entirely of 

pre-Cambrian rocks, chiefly granite, except where Carboniferous formations are present in local downfault 

blocks. The Carboniferous formations found on the 

east side of the crest have the normal regional westerly 

dip and give no indication that the east slope may be 

the east 'limb of an anticline. This westerly dip continues for at least .3 miles beyond the southeast corner 

of the district. There, in the Water Canyon district, 

as shown by Lasky,81 the Mississippian and Pennsylvanian strata and the overlying volcanic rocks rather 

well down the east slope of the range also dip ·westward. 

Lasky made no reference to folds and attributed the 

tilted blocks to faulting. Wells 82 reported that although the formationsin the vicinity of Water.Canyon 

are tilted to the west, those in the southern part of the 

range are tilted to the east. This statement suggests 

that folding like that in the Sandia Range 83 may 

have taken place, · but no information is available regarding the extent or structural details of the eastward-tilted rocks. The meager data available on the 

northern part of the range give no indication of 

eastward-dipping sedimentary rocks. If, therefore, 

the structure of the range is that of an anticline or 

elongate dome, the sedimentary rocks have been thoroughly removed from the east side. 

Th~ general absence of the Carboniferous formations on the east slope, except in local west-dipping 

81 Lasky, S. G., The ore deposits of Socorro County, N. Mex.; New 

Mexico School of Mines, State Bur. Mines and Mineral Resources, Bull. 

8, pp. 46-47, 1932. 82 Wells, E. H., Manganese in New Mexico: New Mexico State School 

of Mines Bull. 2, p. 71, 1918. 

ss Darton, N. H., Tectonics of Arizona and New Mexico [abstract] : 

Geol. Soc. America Bull., vol. 39, p. 182, 1928. 

I 

I 

I 

\ 

Ill\ 

{,, 

'C. I «I 

\ ,_, 

'?. , 

to\ 

/ 

/ 

/ 

I 

I 

Q_ 

0 

0 

0 

g 

0 

0 

0 

9 

c I ., 

::; I i;; 

~ I ~ I X 

/ 

l.y~--

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67 

/ 
68 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

fault blocks, implies that the range is bounded on the 

east by a major east-dipping or vertical fault. Recently Bryan 84 has reported a young fault scarp along 

the northeast base of the Magdalena Range and thus 

partly supports the thesis of a fault or fault zone along 

the east front. The difference in altitude between the 

plain to the east and the top of the peaks covered 

with sedimentary rocks on the crest is about 4,000 

feet, but the amount of faulting along the east front 

would appear much greater if the dip of the Carboniferous rocks were to be projected eastward to their 

intersection with an upward projection of the fault. · 

It is not clear from available· information whether the 

east slope, as a whole, has resulted from movement 

along a single major fault or a set of distributive or 

step faults, as is ~uggested near the crest of the range 

east of Kelly. · 

As the uplift and tilting of the Magdalena Range 

involved east-west arching or elongate doming of the 

. region as a whole and removal of support to the east, 

lurge blocks or slabs would tend to settle eastward 

along the east-dipping faults that eompensated for the 

uplift. 

Some north-south stretching and local collapse also 

took place, which produced the depressed or steppedclown blocks between major transverse faults that dip 

towards each other, as is illustrated by the Tip Top 

block. Although southward tilting of the bedded rocks 

is not pronounced, these downfaulted blocks, or groups 

of blocks, within the district were most depressed near 

their southern ends. 

Minor vertical faults, subsidiary to the east-dipping 

faults, are probably contemporaneous with them and 

related in origin. Where the movement was most 

pronounced and the east-dipping faults had rather 

low angle dips, the overhanging parts of the slabs 

became unsupported, broke along vertical longitudinal 

faults, and settled as faulting progressed, forming 

local downfaulted blocks. This subsidiary movement 

is most clearly represented by the minor fault that 

parallels the southern part of the South Stonewall fault 

(pl. 20). Similar faults subsidiary to the mafor transverse faults are present at several places within the 

district. This mode of origin, together with their 

·vertical to steep easterly dip, would tend to keep these 

faults more open than those with moderate to lowangle easterly dips. It is significant that most of the 

ore bodies in the district are closely associated with 

vertical faults. 

DEFORMATION AFTER THE SECOND STAGE OF VOLCANIC 

ACTIVITY 

A large amount of faulting also took place after the 

second stage of volcanic activity but before the stage 

of stock intrusion that followed. The intrusive rhyo84 Bryan, Kirk, written communication, December 1931. 

lite porphyry, the youngest member of the second volcanic group, is cut by faults that have been partly 

obliterated by the stocks. Most of the movement in 

this stage took place along the vertical and transverse 

faults west of the zone of pre-Cambrian outcrops along 

the west slope of the range. Faults in and west of the 

vertical Waldo fault zone offset the rhyolite porphyry, 

and faults of the Kelly-Graphic or main ore zone, as 

well as adjoining transverse faults, cut the older volcanic rocks (pl. 4 and fig. 5). Possibly movement was 

renewed also along some of the earlier faults. The 

faults with east downthrow between Magdalena Mountain and the Waldo fault are of this age, but no information on their dip is available. 

The origin of the major vertical faults cannot be 

finally determined without thorough study of a much 

larger area. Whether their origin was the same as that 

of the minor vertical faults east of the horsts . is questionable, for they are probably much younger than the 

east-dipping faults. The north extension of the KellyGraphic fault, for example, is younger thap. the eastdipping fault west of it. The south end of the KellyGraphic fault, which dips very steeply eastward and 

curves into the Germany fault, suggests that it is subsidiary to east-dipping faults, but no major east-dipping 

fault has been found near it on the west that would 

strongly support the suggestion. The larger of the 

east-dipping faults within the Kelly fault block (fig. 5) 

may be older than the Kelly-Graphic fault, but they 

cannot be distinguished from parallel faults that developed later and are subsidiary to the Kelly-Graphic 

fault. Movement along the northern part of the 

Mistletoe fault evidently corresponds to a renewal of 

movement along the southern pa;rt of the Germany 

fault, bpt the Mistletoe fault as a whole and the broad 

zone of vertical faults in general alinement with it 

farther south are not related to any neighboring major 

east-dipping fault. Similarly, the depressed blocks 

·between the Crest fault and the vertical fault east of 

it fit this explanation, but the vertical fault continues 

much farther south than the Crest fault and appears 

to converge with the broad zone of vertical faults. 

No major east-dipping faults intervene between the 

vertical Kelly-Graphic fault zone and the Waldo fault 

zone, which is also vertical and has a large west downthrow northwest of Kelly, whereas the Kelly-Graphic 

zone has a larger downthrow southeast of Kelly. The 

principal downthrow is shifted from one to the other 

along cross faults, particularly the fault concealed beneath Chihuahua Gulch. The two vertical fault zones, 

therefore, may be regarded as members of a composite 

zone. 'Vest of this composite zone the only known 

fault or fault zone that has a large east downthrow 

is the one that underlies the broad valley between Magdalena Mountain and the low hill capped with pink 

rhyolite half a mile west of Kelly, but its direction and 
LARAMIDE AND TE'RT>IARY STRUCTURE 69 

amount of dip are not known. This fault zone (fig. 5) 

apparently marks the west boundary of the composite 

tilted block that forms at least the northern part of 

the main range, but, even if a rather low angle easterly 

dip is assumed, it is too far from the Waldo and KellyGraphic fault zones for them to be regarded as directly 

subsidiary to it. 

An alternative suggestion and the one preferred by 

us is that· these major vertical faults were formed during subsidence of the western part of the range and the 

adjoining valley area subsequent to the extrusion of 

the late group of volcanic rocks but prior to the intrusion of stocks; · in other words, that the vertical faults 

are major faults separating depressed areas from relatively elevated areas. If so, a considerable amount of 

subsidence took place in the valley area west of South 

Camp, and the most depressed block is concealed beneath alluvium. The neighboring fault blocks that are 

bounded on the east and west by the Waldo and KellyGraphic fault zones and descend in steplike succession 

from the Nitt stock to South Camp form intermediate 

benches between the depressed valley block and the 

main part of the range. The southerly increase in displacement along the Kelly-Graphic zone at the south 

end of the district suggests that there may be another 

center of principal subsidence farther south. As this 

general subsidence took place after the period of volcanic eruptions, it could be regarded as a compensation 

for the large amount of volcanic material removed 

from below and piled upon the undermined surface; 

but, as the principal volcanic vents or conduits have 

not definitely been located, their relations to areas of 

sunken blocks remain to be determined. 

Burbank,8 5 in the Bonanza district, found that ten-

. sion faults dip towards the centers of maximum collapse, 

and workers in the Tertiary .igneous areas of Scotland 

have shown, as summarized by Richey,86 that ring dikes, 

which occupy faults, are steeply inclined outward from 

the centers of reservoirs. Kingsley,87 however, states 

that the dike occupying the boundary fault that outlines 

the Ossipee Mountain cauldron in New Hampshire is 

vertical. It is probably that, even though the Waldo 

•and Kelly-Graphic faults are vertical or dip steeply 

eastward, they were formed along the east boundary 

of an area of subsidence over an area of volcanic reservoirs and, as shown in the following paragraphs, they 

extended so deeply that they exerted considerable 

influence on the intrusion of stocks. 

The. horsts or relatively uplifted blocks of pre-Cambrian rocks, which form a diagonal zone of southeast 

trend on the west slope of the main Magdalena Range, · 

have apparent major structural significance. In genso Burbank, W. S., Geology and ore deposits of the Bonanza district, 

Colorado: U.S. Geol. Survey Prof. Paper 169, p. 55, 1932. 

86 Richey, J. E., Tertiary ring structures in Britain: Geol. Soc. Glasgow Trans., vol. 19, pp. 42- 140, 1932. 

sT Kingsley, Louise, Cauldron subsidence of the Ossipee Mountains: 

Am. Jour. Sci., 5th ser., .vol. 22, pp. 145-146, 1931. 

eral, the recognized 1najor faults east of this zone dip 

eastward at moderate angles and those west of this zone · 

are nearly vertical (fig. 5). The general uniformity in 

direction of dip on either side of the horsts could suggest that they mark ' an axis of early uplift, that the 

faults originally dipped away from the horsts at high 

angles, and that subsequent uplift and westward tilting 

of the range as a whole decreased the angle of dip 

of the faults east of the horsts but increased the angle 

of those to the west. The fault pattern, however, is 

more complex than this suggestion would imply and, as 

already pointed out, not all of the faults on either side 

of the horsts are of the same age. If the horsts mar ked 

the core of an early flexure which subsequently collapsed, it would be expected that the faults on either 

side of the axis should be symmetrically arranged 

around them, l;mt they are not. Furthermore, faults on 

the same side of a zone of horsts dip in opposite directions and complicate the structural picture. 

In the zone of vertical and west~dipping faults, only 

local and mi.nor east-dipping faults occur, which, like 

the vertical faults in the east zone (p. 68), evidently 

have resulted from the settling of overhanging or unsupported parts of blocks bounded by major vertical 

faults. 

-The foregoing discussion clearly indicates that the 

horsts were not the controlling factor in the complex 

structure pattern of the main range but rather the 

product. They marli: the boundary between the east:-

dipping normal faults of the second stage of deformation and the vertical or steep faults of the third or 

postvolcanic stage of deformation. 

LOCAL FAULTING DURING THE INTRUSION OF STOCKS 

The intrusion of stocks, which followed the principal 

stage of faulting, was evidently guided by the most open 

fault zones and zories of weakness. The relation of 

intrusive stocks to faults is most strpngly suggested by 

the Nitt stock. One of these faults was in the transverse fault zone that separated the Stendel Ridge block 

from the Graphic block and extended westward into 

. or along the north boundary of the large downfaulted 

blocks in the valley area. Its intersection with longitudinal faults is suggested by the sharp bends in the 

outline of the Nitt stock along the west slope of Stendel 

Ridge and beneath the alluvium of the valley, where the 

monzonite boundary was determined by a dip-needle 

survey; also by the dike of monzonite porphyry exposed 

underground along the Waldo fault, and by the details 

of the monzonite contact in the vicinity of Oak Spring. 

The possible relations of the other stocks to faults 

·are obscure. The Tertiary ( ? ) granite stock is partly 

concealed by alluvium and elsewhere is bounded by preCambrian rocks in which faults, even though proved to 

exist, are not readily traceable. 'fhe position of the 

banded rhyolite east of the mouth of Anchor Canyon, 
70 MAGDALENA MININ-G DISrTRIGT, NEW MEXICO 

however, suggests the former presence of longitudinal 

and transverse faults that have been obliterated by 

the intrusion. Probably of equal or greater importance 

in the emplacement of the Anchqr Canyon stock is its 

position along the axis of the mild flexure affecting 

both the main range and Granite Mountain (pp. 36, 57). 

The small stocks in the Granite Mountain area and 

farther north are also so inadequately exposed that 

mapping around them has been insufficient to indicate 

their possible relations to faults. The general alinement of the stocks, however, in a north-northwest direction, essentially coincident with the trend of the KellyGraphic and Waldo fault zones suggests that the intrusions took place along an extensive fault zone of northnorthwest trend, especially at points favored by 

junctions with cross fault zones. 

Whether the process of intrusion was mainly passive 

or produced movements in aqjacent fault blocks is 

uncertain. If only strictly local evidence were being 

considered, the fact" that the Graphic block and the 

block northeast of it, both of which lie along the 

southeast boundary of the Nitt stock, are relatively 

higher than any others would suggest uplift by intruding monzonite; but to what extent this apparent uplift 

is the result of the intrusion and to what extent the 

result of earlier regional movement cannot be determined. The same uncertainty applies to the smaller 

blocks just east of the monzonite. As the faults bounding these blocks are all normal or essentially vertical, 

~ny appreciable uplift of the Graphic and adjacent 

blocks by intruding monzonite must have been sufficient 

to thrust the surrounding blocks aside, as is suggested 

by the offsets of the east-dipping longitudinal faults 

by certain of the transverse faults along the east margins of the blocks. 

The Graphic block, however, is cut by one or more 

dikes of monzonite that follow fractures of northwest 

trend and northeast dip. These fractures may be 

regarded as the result of local tension produced after 

upthrust by the intruding monzonite had subsided but 

before the main part of the stock had become solid. 

The dike along the Waldo fault could also have followed such an uplift. 

Although the monzonite stock has a dominant southwesterly trend, this evidence of uplift is confined to 

its southeast side. Some uplift of the Stendel block 

on the opposite side of the fault could be imagined, 

but to a much less degree, as the position of the rhyolite porphyry sill there is essentially accordant with 

that to the south on the down thrown side of the Waldo 

fault. To explain the extremely localized uplift~ 

therefore, some unsupported assumptions would be 

necessary; for example, that .the obliterated transverse 

fault along which the intrusion may have taken place 

dipped southward and the uplifting force was concentrated on its hanging · wall; also that the regional 

movement was still in progress and produced sufficient 

tension along the Germany fault zone to render uplift 

of the Graphic and adjacent blocks easy. It would 

then, however, be difficult to account for the absence 

of dikes along the major transverse faults. It is less 

awkward to conclude that the present arrangement of 

major :fault blocks was essentially the same before 

intrusion as it is now and that uplifting by the intrudi11g monzonite was very subordinate. · 

The relatively uplifted blocks along the KellyGraphic fault zone but away from the Nitt stock must 

also be consid,ered. The largest of these uplifted 

blocks lie along the east side of the Kelly-Graphic 

fault zone, which is the main ore zone of the district, 

and are separated or broken by depressed blocks . . The 

fact that ore bodies that were formed at relatively 

high temperatures lie along the west side of these 

blocks in the Kelly mine and even in the Linchburg 

tunnel, which is 12,000 feet away from the nearest 

exposed intrusive stock, prompts the suggestion that 

these ore bodies may he underlain by other stocks at 

rather shallow depth along the zone and that the force 

of their intrusion was sufficient to uplift the blocks. 

This suggestion accords with the idea that intrusion 

took place along fault zones or their intersections and 

implies that the faults had already been formed and 

that the force of intrusion only produced later modifications in the amount and perhaps the direction of 

faulting. The assumed thrusting action that would 

have forced we.dgelike blocks upward would also have 

extended compressive action along both the east-dipping and the vertical faults, , but there is no evidence 

of upward drag, which should be especially evident 

along the hanging walls of the east-dipping faults. 

If any such upthrust took place, therefore, it must 

have been too little to counteract the evidence of 

settling that took place prior to the stock intrusions 

or to persist during any minor settling subsequent to 

the intrusions. 

On the whole, therefore, it appears that the intruding 

Nitt stock was not a primary cause of uplift but that 

it worked its way upward along the margin of the great 

sunken block west of the range. This relation recalls 

the distributi~n of stocks along the margins of the great 

sunken block in the Silverton district of Colorado, as 

shown by Burbank,88 who also shows that the metalliferous veins of that district are systematically arranged along and around the same sunken block. 

Whether the Nitt and other stocks in and near the. 

Magdalena district maintain a similar structural setting 

can be determined only by a much more extensive areal 

study. The north-northwest alinement of the stocks 

suggests such a structural control, as does the arrangess Burbank, W. S., Vein systems of the Arrastre Basin and regional 

geologic structure in the Silverton and Telluride quadrangles, Colorado : 

Colorado Sci. Soc. Proc., vol. 13, pp. 174-181, 1933. 
LARAMIDE AND TERTIARY STRUCTURE 71 

ment·of- the major ore bodies along the fault zones that 

border the sunken valley block; but the complete dimensions of .the sunken block are far from being -known. 

A thorough test of this relation would involve detailed 

studies to the south, west, and north of the Magdalena 

district. , 

MINOR ADJUSTMENTS AFTER STOCK INTRUSION BUT BEFORE 

ORE DEPOSITION 

One of the few monzonite dikes that have been found 

follows a principal vertical fault, but the others follow 

subordinate oblique faults and fissures that reflect the 

settling and expansion rather than compression of major 

fault blocks. It could be assumed that some relaxation 

followed the upthrust after the form of the stock had 

been essentially established but before the monzonite 

had completely contracted through crystallization. 

The numerous lamprophyre dikes, which were intruded 

· subsequent to the stocks and dikes of monzonite, also 

follow major faults in a few places, but in the GraphicWaldo and Kelly mines most of them follow minor 

transverse and oblique faults and fissures that reflect 

continued settling of the major fault blocks. 

The dikes of white rhyolite, which were intruded 

later than those of lamprophyre, are scarce in mine 

workings and therefore show no definite relation , to 

these minor faults; but their presence along some of 

the . major vertical faults, notably the Vindicator, 

Waldo, and Grand Ledge faults, indicate the reopening 

of these faults without any noteworthy 'renewal of 

displacement. The east-dipping dike that cuts Tertiary ( ~) . granite, approximately in line with the 

Germany fault zone, suggests similar reopening of 

east-dipping faults. This confinement to major fault 

zones also suggests that the intrusion of the dikes 

accompanied rather than followed the reopening, and 

thereby counteracted subsidiary movements along the 

minor faults within the major blocks. Subsequent to 

the intrusion of these dikes, however, minor adjustments were resumed along both major and mi:dor 

faults, and some new minor faults were formed. These 

adjustments involved further reopening of the vertical 

longitudinal faults and the settling of rock towards 

them along favorably situated minor faults and bedd~ng. In the Kelly fault block, for example, the movement, though small, was similar to that which took 

place during the major' prevolcanic faulting. The 

block, freed on its east and west sides, tended to settle 

along the Kelly-Graphic cross fault, as shown in 

figure 6. Its northeast corner, where this fault converged with the Kelly-Graphic longitudinal fault, was 

pressed tightly against the fault walls; but a little 

farther south, where the longitudinal fault curved· 

slightly eastward, an appreciable open space began to · 

develop. A similar open. space began to develop along 

the Brown fault, a parallel subsidiary of the main 

longitudinal fault. The wedge-shaped blocks .between 

these faults and the eastward-dipping faults of northerly to north~esterly strikes were left . unsupported 

and settled toward the vertical faults, tending to press 

tightly against the east-dipping faults and the KellyGraphic cross fault but less tightly against the vertical 

longitudinal faults. The movement also tended to 

open minor transverse fractures or faults, particularly 

in the slab between the two vertical faults, owing to 

drag along the main cross fault. Longitudinal tension 

cracks dipping toward either vertical fault also prevailed- in the same slab. In short, this slab ·was 

rendered especially permeable to ore-forming solutions, 

and the . open bedding planes in the Kelly limestone 

increased permeability near the cracks and faults. 

Tension cracks could allow some westward spreading 

of solutions into the wedge-shaped blocks, which had · 

settled so tightly against the east-dipping faults as to 

reduce permeability on the whole. 

·structure in the Graphic block was more complex 

than that in the Kelly block. The Graphic block is 

bound~d on the south by the Kelly-Graphic cross fault, 

on the west by the Waldo fault, on the northeast by 

the cross fault of northwesterly trend whose western 

part has been obliterated by the intrusion of the Nitt 

stock, and on the east by an east-dipping fault with 

a l;langing wall of Madera limestone. Simultaneous 

movements down the northeast boundary fault and 

along the west and east boundary faults shifted the 

block downward and southwarP. and tended to open 

fissures or minor faults of northerly or northwesterly 

trend within the block. Those with easterly and northeasterly dips were most subject to opening. Transverse 

fractures between these minor faults also tended to 

open, and local movements of minor blocks between 

pairs of northeast-dipping faults opened tension fractures of northerly and northeasterly trends and steep 

to vertical dips. Settlip.g along the hanging walls of 

these fa~lts and fractures counteracted their opening 

to some degree and produced the Roll fault (fig. 7) and 

similar rolls-along other faults; but openings available 

for circulation developed along ·fault intersections, 

and the west-dipping bedding planes were opened by 

tension movements along these faults beneath the rolls. 

As a result, the principal channels for circulation of 

rising ore-forming solutions were along the Roll fault 

and other faults of northeast and east _dip and also 

a]ong the intervening cross faults and vertical tension 

fractures of northerly trend. 

The east boundary fault of the Graphic block is 

compound and of low easterly dip with a tight hanging / 

wall composed at the surface principally of Madera 

limestone and shale. Shearing along this fault tended 

to open minor steeply dipping or vertical faults to the 

west · of it, as shown in the Mitchell tunnel (fig. 13) , 

but these minor faults evidently · died downward, as 

tension decreased away from the main fault. These 
72 MAGDALENA MINING DISITRICT, NEW MEXICO 

FIGURE 6.-Diagram of Kelly fault block, showing decrease in throw 

along Kelly-Graphic cross fault at its junctions with minor eastdipping faults, the relatively open parts of longitudinal vertical faults 

and the transverse faults between them, and a dike offset along a 

bedding fault. 

faults, .as well as the east-dipping fault, have been 

weakly mineralized, not from below but by sohiti'ons 

that escaped eastward along transverse fractures from 

the principal channels in the Graphic block. 

· East of the east-dipping boundary fault there is a 

north-trending fault zone with prevailing steep 

westerly dip and a net downthrow to the west. This 

zone inay be the northward continuation of the 

1\::elly-Graphic fault zone. It connects with the eastward continuation of the northwest-trending fault 

FIGURE 7.-Diagram showing the 

Roll fault and an associated 

bedding fault along the "silver 

pipe" bed in the GraphicWaldo mine. The Roll fault 

dips 45° NE. and passes upward into a roll in shale. 

50 

that forms the northeastern limit of the ore zone 

in the Graphic block, but it also shows only 

weak effects of mineralization, and it appears as if the 

squeezed shale in the downfaulted wedge between it 

and the east-dipping fault prevented ore-forming solutions from reaching it in any considerable quantity. 

Some may have regarded this fault zone instead o'f the 

east-dipping fault as the east boundary of the Graphic 

block, and insofar as minor movements before ore 

deposition are concerned, it may be; but the east-dipping fault has the greater throw and more nearly 

defines the east limit of productive ground. 

The opening of the Waldo fault, which forms the 

west boundary of the Kelly and Graphic blocks, must 

have induced settling towards it, especially down the 

dip of bedding planes. Irregularities a.long the major 

cross fault that bounds the Graphic block on the northeast and , along the Kelly~Graphic cross fault also 

favored supplementary raulting along bedding planes 

but mainly in the direction of strike; and a combination of the two movements doubtless resulted in an 

oblique movement. The positions of the east-dipping 

minor faults and the west-dipping beds (fig. 7) also 

favored simultaneous movements along faults and bedding planes owing to the downward pressure of overlying rock. The outstanding examples of these simultaneous movements are the "roll" fault in the Graphic 

mine and the associated bedding faults along the top 

and "silver pipe" beds of the Kelly limestone. 

The Roll fault strikes northwest and dips about 45° 

NE. Its dip slip is clearly expressed in the Kelly limestone, but for the most part the fault passes upward 

into a small monocline or roll in the basal shale bed of 

the Sandia formation. Where the dip slip in the limestone is greatest-as much as 30 feet-the shale in the 

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:MAP SHOWING DISTRIBUTIO OF FAULTS, DIR£CTIO S AND APPROXIMATE AMOUNTS OF MOVEMENT ALONG SOME, AND 'LATIONS TO TERTIARY (?)STOCKS. 

200889-42 (Face p. 72) 
GEOLOGICAL SURVEY 

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PROFESSIONAL PAPER 200 PLATE 21 

107 11 

TOPOGRAPHIC MAP SHOWING THE LIMITS OF PEDIMENT B AND THE APPROXIMATE LIMITS OF THE OLDER DISSECTED PEDIMENTS C TO H. 

20088~ (Face 1). 72) 
GEOLOGICAL SURVEY PROI<,ESSIONAL PAPER 200 PLATE 22 

A. FOOTHILLS OF MAGDALENA RANGE, LOOKING NORTH FROM LOW RHYOLITE HILL THREE-QUARTERS OF A MILE WEST OF KELI.Y. 

Waldo tunnel and dump in right middle ground and Waldo shaft and dump at extreme right. The wooded alluvial slope in the left middle ground is cut by shallow gullies 

that expose the\hedrock of pediment B. The low spur behind the dump of the Waldo tunnel is correlated with pediment D . Stendel Ridge in the middle back- ground is correlated with pediment F . 

B. UPPER PATTERSON CANYON, LOOKING WEST. 

The light-colored bench between the upper and lower shaded slopes in the foreground is covered with al!uvium and represents pediment D. 

PHYSIOGRAPHIC DEVELOPMEN'l' 73 

roll has also been displaced for 15 feet down the dip of 

the fault. Movement along the "silver pipe" bedding 

fault is indicated by the offset of a monzonite dike for 

about 40 feet, the part .above the bedding fault moving 

down the dip. At one place, on level10 of the GraphicWaldo mine, the bedding fault was seen to curve sharply into the Roll fault, showing that there must have 

been a rather large component of movement along the 

junction, which pitched north-northwest at a rather· 

small angle. As the trend of the dike is oblique to the 

strike of the bedding, southward movement of the 

upper part of the dike could produce an effect, as seen 

in cross section, similar to a movement directly down 

the dip. The relative amounts of strike slip and dip 

slip have not been determined. To ma]?:e room for the 

roll in the shale the ,Kelly limestone beds above the 

"silver pipe''' bed must have been pushed directly or 

obliquely down the dip of the bedding fault a corresponding distance. At the same time the bedding 

planes in the limestone on both sides of the Roll fault 

were in position to be opened, as tension cracks by 

. shearing along that fault, and their perme~bility to 

ore-forming solutions was thereby increased. Minor 

transverse faults and fissures connected the Roll fault 

with the longitudinal faults along the Graphic tunnel 

and aided in promoting circulation along both faults. 

This relation of late bedding faults to eastward- or 

northeastward-dipping faults is doubtless common 

throughout the district. · Lamprophyre dikes offset in 

the same general direction and by the same amount as 

the monzonite dike just cited have been mapped in the 

extreme southeastern part of the Graphic-Waldo mine 

and in the Kelly mine, and one part of another dike 

beneath a bedding fault was found in the Juanita mine. 

Where no dikes are exposed along bedding faults, how-

'ever; it has not been possible to distinguish between 

early reverse movements tl}.at accompanied regional. 

folding and tilting and the later normal movements 

that accompanied the different stages of faulting since 

the eruption of the volcanic rocks. 

The movements that took place in the intrusive stockR 

between the periods of dike intrusion and ore deposition are not clearly shown, as the rocks at the surface 

are largely reduced to residual boulders and very few 

mine workings penetrate stocks. In the Nitt mine !1 

few dikes branching from the monzonite 'stock are exposed and are much shattered, but no definite trends of 

major fracture_s are shown. The mineralized fractures 

to the north along .Hardscrabble Valley, however, indi- · 

cate fissuring in a northerly dl'rection. They suggest 

that a major zone of fissuring in monzonite underlies 

the upper part of the valley and is in line with the 

Vindicator fault, along which some movement .took 

place after the intrusion of the Tertiary ( ? ) granite 

stock and also after that of the white rhyolite dike that 

occupies the fault. The Hardscrabble workings also 

20081'!9-42-6 

show that some shearing has taken place in Tertiary ( ~) 

granite along a transverse fault of southwest trend and 

-that where this fault meets a fault or fissure zo:p.e o£ 

northeasterly trend, the granite is thoroughly -shattered. 

No measurable amount of . displacement along either 

fault could be determined. This evidence, though too 

small and scattered to be very significant, is in keeping 

with the idea of n1inor adjustments along faults 

throughout the region. 

MINO~ ADJUSTMENTS AFTER ORE DEPOSITION 

Faulting subsequent to ore deposition is negligible 

within the district. A little evidence of shattering was 

noted in a v~inlet along the Kelly-Graphic cross fault, 

and some slickensides were seen in ·ore along fractures 

in the Kelly-Graphic fault zone; but no measurable 

amount of offset was found. Bryan,89 however, has 

called attention to a recent fault scarp along the north-

. eastern base of the Magdalena Range and has suggested 

thaf the relative uplift that it -signifies has influenced 

the subsequent topographic development of the range. 

The part of the range within the district, howevet, including the valley between the main range and Magdalena Mountain, has acted essentially as a structural 

unit, although trivial adjustments have doubtless taken 

place throughout it. 

PHYSIOGRAPHIC DEVEL.QPM:ENT ~ 

The present topographic features have resulted from 

several stages of erosion, all of which are later than the 

main stage of faulting and the intrusion of the monzonite and granite stocks. From the correspondence in 

altitude of the tops of some o~ the spurs with remnants 

of alluvium well above the general alluvial slopes it is 

conCluded that the spurs mark the positions of older 

bedrock floors, h~re called rock pediments. The altitudes of other spurs are so related as to indicate still 

higher pediments. The recognition of these pediments 

(pl. 21 and fig: 8) throws considerable light on the erosion history of the district, which we have discussed at 

some length elsewhere 90 and shall only briefly review 

here. As the stages of erosion have ·been traced from 

the most recent to the earliest that can be recognized, 

the youngest, represented by the present arroyos, is 

designated A, and the successively older are B to H, 

H being the oldest that is at all definable. 

The most recent pediments, designated B on plate 21, 

are well represented on the slope just west of the Nitt 

mine, i:q the floor 9f Anchor . Canyon, and at several 

places in lower Hardscrabble Valley and around Granite Mountain, where bedrock beneath veneers of alluvium is exposed in gulleys and shallow prospect pits. 

The pediment west of the Nitt mine (pl. 22, .A) slopes 

B9 Br.yan, Kirk, written communication, 1933. 90 Koschmann, A. H., and Loughlin, G. F., Dissected pediments in the 

Magdalena di~trict, New Mexico: Geol. Soc. America Bull., vol. 45, pp. 

463..:.478, '1934. .j ' 
74 MAGDALENA MININ·G DISTRICT, NEW MEXICO 

about 600 feet to the mile, whereas the alluvial veneer 

above it slopes 500 feet to the mile. Both pediment and 

alluvial veneer slope away from the mountain -front 

and in the main directions of drainage. Pediment C, 

which antedates pediment B, is well represented in the 

vicinity of South Camp by low spurs and hills of pink 

rhyolite and silicified andesite. North of Kelly and in 

Granite Mountain area, where erosion has been greater, 

pediment C is not so well represented. 

The most clearly defined of ,the older, dissected pediments is D, which is represented by a sloping alluviumcovered bench (pl. 22, B) along the southwest side of 

Patterson Canyon between altitudes of 7,725 and 7,875 

feet. The north end of the bench is a landslide remnant that has been planed off to conform to the pediment slope. The gentle westerly slope just south of 

Chihuahua Gulch is also covered, but less conspicuously, 

with remnants of alluvium between t;he same altitudes 

and is evidently another representative of pediment D, 

although the D stage of erosion there cannot be sharply 

distinguished from the E and C stages. The intervening spurs and hills that conform to pediment D are 

shown on plate 21. 

The saddle that con~ects Stendel Ridge with the main 

Magdalena Range has an alluvial cover distinctly 

higher than the adjacent part of pediment B, though 

not isolated from it by exposures of bedrock. The saddle conforms in altitude with pediment D but consists 

of distintegrated monzonite that is so readily and uniformely eroded that 1t does not maintain steep slopes 

but has allowed the alluvium of pediment D to slump 

down onto that of pediment B. Its slope shows that 

its alluvial cover was formed by drai~age from the east, 

A 

c 

J) 

Tm 

D 

but the present drainage from the east is diverted northward down Hardscrabble Valley. This valley is so 

much more directly connected with the trunk drainage 

channel of the district than is the slope west of the 

saddle that erosion was correspondingly more rapid 

and extended the valley headward until it tapped the 

westward-sloping gulches and diverted their drainage 

from the adjacent part of pediment D. 

Hills and spurs on the north slope of Stendel Ridge 

that correspond to pediment D are between altitudes 

_ of 6,800 and 7,000 feet. Those with altitudes near 

6,500 feet in the Granite Mountain area are also tentatively assigned to pediment D because of their comparable size and their heights above pediment B. They 

are about 100 feet above the present valley bottom. 

Pediment D corresponds closely in altitude to the 

bottom of the thoroughly oxidized ore in the Kelly and 

Graphic-Waldo mines. It appears that erosion of the 

thick shale member of the Sandia formation from the 

main fault zone and the lowering of the ground-water 

level during this stage of erosion favored rapid circulation and oxidation. Erosion during later, comparatively short stages has not been sufficient to lower the 

water level in the different fault blocks below that of 

stage D. . 

No remnants of alluvium above pediment D are preserved, but spurs are so grouped at certain altitudes 

that, with proper allowance for westerly and northerly 

slopes, they indicate at least four pediments, which are 

designated E, F, G, and H on plate 21. The most distinct of these is pediment F, along which two beveled 

masses of landslid~ material remain. It wa:s evidently 

J!. __ _ Qal 

-------

\~Tip 

\ 

\ 

Tpa 

Tpa 

c' Tra Tbr ·-

Tpa 

e.ooo' 

7,500' 

7,000 

~\ I 

I 

7.soo' 

n· 

Tpa a,ooo' 

7,500' 

Horizontal scale 

Ve if4 Y2 3/.., 1 Mile 

FIGURE 8.-Profiles showing concordant altitudes of spurs and foothills interpreted as dissected pediments. Lines of profiles are shown on 

plate 21. .. Quaternary: Qal, alluvium; Qls, landslide. Tertiary: Tm, mozouite.; Trp. rhyolite porphyry; Tip, latite porphyry; Tpr. pink rhyolite; Trr. 

red rhyolite; Tua, upper ande~ite; Ti~ .. red 11-ndesite; Tbr, banded rhyolite; Tpa purple andesite, Carboniferous; Ca, Abo sandstone; Cm, 

Madera limestone; Csuq ·(upper quartzite), Css (shale), and Cslq (lower limestone), members of Sandia formation; Ck, Kelly limestone. 

Pre-Cambrian, pC (chiefly argillite, felsite, and granite). · 
ORE DEPOSITS 75 

during the early part of st'age F that rapid erosion of 

shale along the west side of 'the Young Aiherica and 

adjoip.ing faults of the Kelly:.Graphic zone (pl. 2) developed an oversteepened scarp. This scarp, together 

with the west dip of the sedimentary rocks and the 

west-dipping fractures in the· underlying granite, led 

to the formation of the landslides, whose scars are still 

distinct east of the fault zone from the vicinity of 

the Young America mine southward. 

In tr.acing the spurs that accord with pediment F, it 

is found that the present summits on Stendel Ridge 

also accord with it approximately. These summits imply that the valley floor west and north of the ridge 

sloped gradually away from them during stage F. The 

valley north of the ridge had an inferred altitude of 

about 7,000 feet, so the summit of Granite Mountain, 

therefore, must have been barely exposed ab?ve tl_le 

general slope of pedin1ent F. The volcanic rocks that 

once covered the northern part of the main range extended beneath this old pediment and were continuous 

with those of the Granite Mountain area, although 

broken by fault zones. During still earlier stages of -

erosion, when the pediments and valley floors were 

still higher, the main range must have sloped gradually 

northward to the Granite Mountain 'area and beyond. 

When the erosion cycle began, the northern part of 

the main range had a volcanic cover 2,000 feet thick 

(pp. 23, 37). Nothing is known of the corresponding 

cover over Magdalena Mountain, as the formations that 

once overlay its present cap of pink rhyolite all lie west 

of the area studied. There must have been sm:p.e topographic relief as a result of the faulting, and the earliest 

stages of postvolcanic erosion must have been guide by it. 

The downfaulting of the area between the mam 

range and Magdalena Mountain may have formed a 

closed basin; but if so, it was doubtless filled at an 

early stage, and then, owing to the high barrier that 

the main range formed at the time, the drainage may 

have been westward. 

The principal drainage of the surrounding region, 

however, was along the Rio Grande. As its western 

tributaries had relatively short, steep courses mainly 

through volcanic rocks, the country east of the Magdalena Range was lowered more rapidly than the western 

slope. The relative downfaulting of the Granite Moun-

. tain area, whose more resistant rocks were mainly 

below the earlier pediment levels, permitted erosion to 

develop much more rapidly than in the main range. 

As the more resistant rocks became exposed during apd 

after stage F, erosion became confined to the great 

-transverse fault zones and the adjoining easily eroded 

stock of Tertiary ( ~) granite. The courses of La 

J enze Creek and its southern tributary became established, Granite Mountain became separated from the 

main range, and Stendel Ridge began to develop as a 

spur of the main range. 

As the transverse valley between Granite Mountain 

and Stendel Ridge deepened, drainage from the valley 

west of the main range became diverted through it, 

and the topography of the district became much as it 

is today, except for ·the subsequent gradual deepening 

of the valley and the corresponding deepening of the 

adjoining gulches. 

So great an ainount of erosion implies a large 

amount of relativ'e uplift of the range since the main 

period of' faulting that is recorded within the district; 

furthermore, the more distinct pediments, F and D, 

imply halts in the uplift sufficiently long for the 

valleys in and adjoining the district to broaden and 

establish temporary base levels." During this intermit-

•tent uplift the mass that includes the main range, 

Granite Mountain, and Magdalena Mountain acted as 

a unit. Too little is known of physiographic development in the surrounding region to co'rrelate these 

principal pediments with any definite stages of regional erosion, but the pediments are believed to be 

related to the varying rates at which Rio Salado and 

its tributary La Jenze Creek cut their channels downward through the volcanic flows and tuffs that lie 

· east and northeast of the Magdalena Range. The 

, present continuation of this processis apparent along 

! the road between Socorro and Magdalena, where allu-

: vial slopes belonging to one of the more recent stages 

, of erosion are protected by hard rock in some places 

r.nd are largely removed in others. Bryan,91 on. the 

basis ·of his physiographic studies in the Socorro re-

, gion, states that pediment B of the Magdalena Range 

is in perfect adjustment to Snake Ranch Flats (pl. 1), 

'vhose S\}rface corresponds to the older of two distinct 

erosion surfaces on the east side of the Socorro Mountains; 92 also that the slight dissection of pediment B 

may be attributed to climatic causes or to the recent 

uplift of the Magdalena Range that corresponds to the 

frtult scarps along the northeast base of the range. 

ORE DEPOSITS 

HISTORICAL SKETCH 

The historical sketch presented below has ·been compiled mainly from statistical reports by Raymond,93 

Mint reports by Burchardt" annual "Mineral Resources" 

reports by Henderson,95 and short papers by several 

a:uthors cited in the bibliography (pp. 4-5). 

91 Br.yan, Kirk, written communication, January 1934. 92 Bryan, Kirk, Pediments developed in basins with through drainage 

as illustrated by the Socorro area, New Mexico [abstract] : Geol. Soc. 

America Bull., vol. 43, pp. 128-129, 1932 . . 

.. 9a Raymond, R. W., Statistics of mines and mining in the States and 

Territories west of the Rocky Mountains (1869, p, 4;1?; and 1872,· p. 

313) : U. S. Treas .. Dept., 1870 and 1873. 

"Burchard, H. C., Report of the Director of the Mint upon the production of precious metals in the United States (in 1881, pp. 327, 340-

341; in 1882, pp. 340, 376-379) : U. S. Treas. Dept., 1882 and 1883. 

96 Henderson, C. W., A:n,nual chapters on New Mexico in Mineral Resources U. S., U. S. Geol Survey, 1908-24 ; U. S. Bur. Mines, 1925 31 ; 

Minerals Yearbook, U. S. Bur: Mines, 1932-35. · 

,_ 
76 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

According to Raymond 96 a California miner found 

a very rich piece of silver ore in the Magdalena Range · 

in 1866, "and subsequent prospecting expeditions resulted in the discovery of many lodes, most of them 

small but rich in copper and silver." They were found 

on the summit and western slope of the range, mainly 

in its northern part. Raymond gave brief notes on 

the "Washington lode" and the "Chavez," its south ex:-

tension, located near the north end of the summit, dipping 35° W., and containing copper, lead, silver, and 

gold. He also described the Santa Juliana lode, at the 

base of the western slope, as a large vein from 10 to 20 

feet wide, traceable for a long distance and containing 

lead carbonate with some copper, silver, and gold. 

These three names are not mentioned in any other reports, but the Washington lode and the Chavez may 

correspond to claims between the Ambrosia and Stonewall, and the Santa Juliana to the Juanita, Graphic, 

or some intervening claim in the main ore zone. 

According to Brinsmade,97 Gordon,98 and others, Col. 

J. Hutchison (or Hutchason ~) discovered lead ore at 

Kelly and located the Juanita and Graphic claims in 

the spring of 1866 while looking for rich silver ore said 

to have been found in that part of New Mexico a short 

time before. According to records of the General 

Land Office, however, the Juanita claim was not located 

until1875 and the Graphic claim until1879. Hutchison 

and his partner, Pete Kinsinger, smelted the ore in 

adobe furnaces and shipped the bullion to St. Louis as 

return freight for the bull teams then hauling out supplies for the region over the Santa Fe Trail. Pig lead 

was then 12¥2 cents a pound at St. Louis, but its continued fall in price finally made shipments unprofitable, 

and mining languished for several years. 

Raymond 99 in 1872 mentioned the Grand Tower, Poor 

Man's, Little Fanny, Pony, Alpine, Washoe, Sucker, 

Wolverine, and Sterling as the most prominent carbonate lodes, but of these only the Grand Tower w~s 

recorded on Herrick's claim map, compiled in 1910. 

The Grand Tower claim, according to Burchard,t was 

worked about 1872 

by a party of adventurous miners and the ore smelted in rude 

adobe furnaces, and after being taken to St. Louis via the old 

Santa Fe Trail, was sold simply as lead, no returns being made 

for the 10 to 30 ounces of silver per ton it carries. 

It may be that this shipment is the same as that credited above to Hutchison and Kinsinger, although the 

claims mentioned are different. The Grand Tower 

claim, according to the records of the General Land 

Office, Washington, D. C., was not located until September 20, 1879, and was patented January 25, 188'7. 

~ Raymond, R. W., op. cit. for 1869, p. 413, 1870. 97 Brinsmade, R. B., Kelly, N. Mex.-A zinc camp whose ores have 

been made available by modern metallurgical methods: Mines and Minerals, vol. 27, p. 49, 1906. 98 Lindgren, ·waldemar, Graton, L. C., and Gordon, C. H., Ore deposits 

of New Mexico : U. ·S. Geol. Survey Prof. Paper 68, p. 241, 1910. 

99 Raymond, R. W., op. cit. for 1872, p. 313, 1873. 1 Burchard, H. C., op. cit. for 1882, p, 377, 1883. 

The Poor Man's and Little Fanny · deposits were described as from 30 to 60 feet wide and rich in ' lead but 

with "little over $30 per ton in silver." Raymond also 

referred to "a fe,v experiments" that had been made to 

reduce the ore, which was "carbonate of lead, bearing 

silver at the rate of $30 to $600 per ton, · and sulphuret 

of copper also rich in silver." George Way & Co. had 

tried to reduce ore from the Little Fannie in a small 

reverberatory furnace, and had produced "1,839~2 

pounds of lead containing 66.7 ounces of silver, but 

much of the lead was lost in the slag." J.D. Baker and 

brother, after unsuccessful attempts with a reverbera.-

tory furnace, built a small cupola furnace and supplied 

the blast by hand bellOi\vs. It was more successful than 

the reverberatory furnace but was too small to be 

operated to advantage. 

Brinsmade 2 states that in 1876, ·when prices had somewhat recovered after the panic of 1873, "Col. E. W. 

Eaton acquired the Juanita claim and smelted its ore 

for 4 years in an adobe furnace at Kelly or Middle 

Camp." About 1880 he bought the adobe smelter of 

Shaw and Ales at South Camp and, changing it to a 

water-jacketed blast furnace, kept it in blast for several years on lead ore from the Imperial and adjoining 

claims. This may be the same smelter with a capacity 

of 40 tons but "out of blast for some time," mentioned 

by Burchard in his report for 1881 3 as connected with 

the Iron Mask mine, which was then full of water. 

The large ore bodies in the Kelly and Graphic claims 

were discovered, according to Philip ~· Argall, in 

1878-79, "when it might be said the district took its 

first boom." The Graphic claim was purchased £or 

$30,000 by Hanson and Dawsey, and the Kelly for 

$45,000 by Gustav Billings. According to the General 

Land Office records many of the claims in the district 

were located in 1879-81, including the Alhambra, Ambrosia, Anchor, Cimarron, Graphic, Grand Tower, · 

Hardscrabble, Iron Mask, Juanita Extension, Kelly, 

Legal Tender, Little Loella, Review, Sampson, 

Stonewall, and Waldo. · 

Billings built the Rio Grande smelter at Socorro in 

1881. This smelter was operated steadily for several 

years, using the lead carbonate ores of the Kelly mine, 

which were low in silver, to flux the siliceous ores from 

the Socorro and other districts tributary to the Atchison, Topeka & Santa Fe Railway system. This.period 

was essentially one of silver mining, as shown by the 

production for the years 1881-87 in the accompanying 

table of metal output in Socorro County; there was 

little demand for base metals. The district was said 

by Burchard in 1881 4 to he "next to Socorr_o in point 

of importance." He also said that the ore was principally galena, which occurred in large quantities; it was 

accompanied in some of the mines by considerable co~-

ll Brinsmade, R. B., op. cit., p. 49. 3 Burchard, H. C., op. cit. for 1881, p. 340, 1882. 

4 Idem, pp. 340-341. 
ORE DEPOSITS 77 

per and in others by zinc, which rendered the ore 

refractory. Evidently some essentially unaltered sulphide ore had already been found. Burchard continues: 

The North and Middle Camps of the district contain the 

leads most extensively worked in the past, and the ruins of 

old smelters are still to be seen. It was believed that this 

galena carried large or at least paying' quantities of silver, and 

shipments to the St. Louis Smelting Works, some years since, 

aggregating 20,000,000 pounds, yielded something over $20,000 

worth of silver. It would seem, with present railroad facilities for the transportation, that mines producing ores of this 

value could be made to pay, but for some cause work is suspended, and the machinery left to decay. 

He referred specifically to the Iron Mask mine and 

smelter, which were then owned by a company in 

Toledo, Ohio. The Iron Mask and the adjoining Lungren claims contained "exceedingly high grade ore." 

The Juniata (juanita n was the best-developed and 

most productive mine, and the Imperial, whose ore 

unfortunately contained zinc blende, was next in importance. The Graphic mine , then had three shafts, 

each in ore "composed principallly of lead in different 

forms, iron, and a small amount of silver." The ores 

mined were reported to be sold to the Cerrillos Smelting Co., for fluxing purposes, the company paying for 

12 ounces of silver to the ton. He also referred to the 

Mammoth claim as on an undeveloped bold outcrop of 

white quartz over 2,000 feet long and contait1ing "many 

small veins of rich silver ore." This description could 

apply either to the vei~ in felsite east of Hardscrabble 

Camp or to the long ledges,of silicified Kelly limestone 

along the summit of the range east and southeast of 

l{elly. The district was then connected with Socorro 

"by an excellent natural road," and the railroad that 

was then planned to "intersect the richest part of the 

Magdalenas:' was expected to make a "vast quantity 

of low- and medium-grade ores of the district * * * 

valuable." Billings was later ·instrumental in having 

a branch of the Atchison, Topeka & Santa Fe Railway, 

which was surveyed and constructed in central and 

southern New ~fexico in the period 1879-82, extenQ.ed 

from Socorro to ~fagdalena. 

Burchard in 1882 5 said that the Juanita, with much · 

less development than the Kelly, in 1882, was reported 

to show a large body of lead carbonates. The lode was 

then said to be located aJld opened up at points for a 

distance of about 3 miles, "invariably rewarding development by showing a good vein of ore near surface." 

In other words the main ore zone as defined in this · 

present report ·had been prospected throughout ·the 

extent of the main range shown on plate 2. 

The veins along the upper slope and top of the range , 

had also been well prospected, and, though the. silver 

content of the ores was not high, it was sufficient to 

make them desirable as flux for smelters treating 

5 Burchard, H. C., op. c.it. for 1882, p. 376, 1883. 

richer but more refractory ores; for example, ore containing galena and valued at $40 a tori was mined in 

the North and South Imperial claims, which eiidently 

included the present Young America. A small body 

of copper ore was mined at the bottom of a 120-foot 

shaft in the Young America claim. 

The Hardscrabble and the adjoining Belcher claims 

were being steadily worked in 1882. Twenty-five tons 

of the Hardscrabble ore, shipped to the Cerrillos 

smelter, gave a return of 25 percent of lead and 33 

ounces of silver to the ton. 

.The Victor and Great Western claims, owned by the 

~fagdalena Mining Co., which also owned the Iron 

Mask, were both being worked f9r lead carbonate ores, 

whose respective assays showed 50 percent of lead and 

16 ounces of silver to the ton and 62 percent of lead 

and 17 oup.ces of silver. These claims evidently included the unpatented Victor claim, which, according 

to W. H. Herrick's claim map, compiled in 1910, 

adjoins the Oak Forest claim ~ust beyond the southeast 

. corner _of the district. On the Josephine claim, leased 

to the same company, a 57foot ledge of quartz assaying 

50 ounces of silver to the ton was being developed, and 

the Raven claim, recently purchased for its fluxing ore, 

~lso proved to be of value as a silv-er-lead property. 

The iron ore included magnetite and also hematite, 

which ·contained 23 ounces of silver "to the ton. The 

Raven claim may have been, on the present Medley 

Ranch, west of Magdalena Mountain, from which magnetic iron . ore was said to have been shipped to the 

South Camp smelter in 1882 (see p. 163). 

The Kelly ·· was proving to be a valuable mine. It 

was developed by a tunnel then more than 200 feet long, 

presumably one of those along the Kelly-Graphic fault, 

and by connected drifts, crosscuts, and inclines. The 

ore was "low-grade sand carbonate" containing some 

galena, averaging between 50 and 60 percent of lead,· 

about 10 ounces of silver to the ton, and showing a little 

copper. The ore was being mined at a rate of 35 tons 

a day, at an average cost of about $1 a ton, and was 

"bought directly on the dump of the mine by the [ore 

purchaser of the] American Mining Co.'s smelter." 

This was evidently the name of the Billings company. 

According to Kirchoff 6 the ore from the Kelly mine 

together with custom ore [including lead ore from other 

counties] t:J;eated in, Billings' smelter at Socorro accounted for the bulk of the lead produced in New Mexico 

during the next few years. He estimated the total lead 

produced in New Mexico at 2,400 tons in 1883, 6,000 tons 

in 1884, and less than 5,000 tons in 1885, when the Billings smelter produced 4,651 -tons of base bullion containing 909,652 ounces of silver and 3,926 ounces of 

gold. Production did n_ot increase in 1886, although 

in addition to lead produced by the Billings smelter, 

6 Kirchoff, C., Jr., Lead: Mineral Resources U. S. 1882, p. 313 ; 1883-4, .. 

p. 425 ; 1885, p. 258. • 
78 MAGDALENA MINING DISfl'RICT, NEW ME.XICO 

which continued to be the principal smelter in the Territory, the Graphic smelting works produced lead from 

Magdalena ores. The two smelters produced 7,325 tons 

of lead in 1887, in spite of the fact that the Kelly mine 

was at one time thought to be exhausted. Its lower 

levels had entered sulphide ore, but the discovery of n, 

new ore body by a lessee restored the mine to its old 

rank for a short time. In 1888 the Graphic mine was 

closed for a considerable period "because the affairs of 

the property were much involved," and the output of 

the Kelly mine decreased in that year and the following 

year, partly because "dead work" in the spring of 1889 

stopped the work of les~ees. A small concentrator to 

treat low-grade ores was operated-"in a very .desultory 

manner." The lead produced from ore mined in Socorro County, practically all from the Magdalena district, amounted to 1,187 short tons in 1889,7 but the 

agent for the Director of the Mint gives 1,708 tons. 

Other mines that were reported to be produdive prior 

to 1890 were the Juanita, Hardscrabble, Cavern, and 

Grand Ledge. 

No reference to the district or to Socorro County 

was made by Kirchoff in the "Mineral Resources" volumes for 1891-1904, but Brinsmade 8 and Argall 9 state 

that the Rio Grande [Billings] smelter was operated 

steadily until 1893, and thereby imply that the Kelly 

mine and doubtless others were active during that 

period. The Rio Grande smelter, according to Tuttle,10 

was handicapped in 1890, when the Windom bill went 

into effect, increasing duties on certain grades of leadsilver ores coming from Mexico. Then followed the 

establishment of larger smelting plants in Mexico and 

at El Paso, which together with high freight rates, 

the depression of 1893, and the apparent exhaustion of 

lead carbonate ore in the Kelly and Graphic mines, 

forced the Rio Grande smelter to close permanently. 

The plant had been employing from 500 to 1,000 men, 

and when it closed in 1893 Socorro became nearly 

deserted. In 1901 it was purchased and dismantled 

by the American Smelting & Refining Co., which also 

purchased the El Paso smelter and enlarged it to 

permit the handling of copper ores. Since then lead 

and copper ores from the Magdalena district have been 

shipped to El Paso. Slag from the smelter dump at 

Socorro, because of its metal content and fluxing value, 

has also been shipped to El Paso. 

Between 1894 and 1902 the mines were worked in 

desultory fashion, while the lead carbonate ores, the 

only ores of shipping grade, were approaching exhaustion.- In 1896 n the Graphic smelter, of 100 tons daily 

capacity, was erected 1¥2 miles west of Kelly,. It is 

'I Kirchoff, C., Jr., op. cit. for 1886, p. 146; 1887, p. 110; 1888, p. 89; 

1889-90, p. 80. 

s Brinsmade, R. B., op. cit., p. 49: 

• Argall; Philip B., op. cit., p. 366. 

10 Tuttle, E. G., The Magdalena mining district, New Mexico : Mines . 

and Minerals; vol. 33, p. 275, 1912. 

• 11 Brinsmade, R. B., op. cit., p, 49. Argall, Pbilip B., op. cit., p. 366. 

not to be confused with the smelter casually mentioned 

by Kirchoff in 1886 and 1887.7 _ It was operated 

intermittently until 1902, when the: lead carbonate ore 

of the Graphic mine was largely exhausted. ~ It was 

handicapped by the shortage of . local siliceous ' ore 

and by high freight rates on · ore, ·- fuel, and supplies 

from elsewhere. In 1902 a 50-ton water-jacketed stack 

was erected half a mile south of the Graphic smelter 

by B. A. Statz, of Albuquerque, who was connected 

with the Cavern and Grand Ledge mines, but it was 

never blown in. The closing of the Graphic smelter 

marked the end of the lead carbonate period of the 

district, when mining practically came to a standstill. 

Production of zinc in the western states had been 

negligible until 1898, partly because the oxidized lead 

ores, which had greatly predominated, had been essen-: 

tionally free from zinc and partly because metallurgists had not been successful in separating zinc from 

lead in sulphide ores; but the large bodies of zinc-lead 

sulphide ore found below the oxidized zone in the 

principal lead-mining districts induced successful 

efforts at separation. The earliest production of zinc 

from sulphide ores in the Magdalena district, however, 

was overshadowed by the discovery of high-grade zinc 

carbonate ore in the Graphic mine. 

In this mine the oxidized lead shoots that extended 

from the northern part of the third or main . tunnel 

level down to level 5 had been practically worked out 

by 1892, and the mine was believed exhausted; but it 

was sold for $90,000 to A. Bement, of Terre Haute, 

Ind., for whom it was managed by J. B. Fitch. Fitch 

found a 20,000-ton shoot of oxidized lead ore at the 

south end of level 3 but had mined it all by 1902, 

when he and C. T. Brown took a bond and lease on 

the mine. They discovered zinc carbonate beneath this 

shoot in 1903 and completed the purchase.12 

They took a sample to southwest Missouri, where it 

so impressed the operators of the Joplin smelter that 

a large shipment was ordered and the district's zinc 

period began. Other shipments were made to Wisconsin, where zinc carbonate ores were also in high 

favor with zinc-pigment manufacturers. Heretofore 

large quantities of zinc carbonate, whether recognized 

or not had been removed as waste and thrown over the 

' dumps; but now large bodies of these ores began to 

, bt:' worked in the Kelly and Graphic mines, and smaller 

~ bodies, doubtless, in several other mines. Zinc oper-

' ators generally became interested. In 1904 the Sherwin Williams :{>aint Co. purchased the Graphic mine 

from Fitch and Bro~n for $150;000 and organized 

, the Graphic Lead ' & Zinc Mining Co. to operate it. 

The name '\VaS changed a year or two later. to the 

: Ozark Smelting & Mining Co., which is th~ present 

owner. Later in 1904 the Tri-Bullion - Smelting ·& 

u Brown, C. T., oral information, 1915. 
ORE DEPOSITS 79 

Development Co., of Chicago, bought the Kelly mine 

from Mrs. Gustav Billings of Cincinnati for a priGe 

reported to be $200,000, and the Empire Zinc Co. 

bought the Lillie group, which lay west of the Kelly 

mine.13 Large shipments were made, _in part from 

dumps, but mainly from underground bodies that 

already were largely blocked out and could be mined 

and shipped with a minimum of time and labor.14 

Zinc recover·ed from ore shipped amounted to 1,856,297 

pounds in 1903 and 17,991,780 pounds in 1904. The 

district became the leading zinc producer of New 

:Mexico and retained its rank until 1920. New Mexico 

became one 'of the five leading western states in zinc 

production. According to Haddon/ 5 the zinc carbonate 

ore from Kelly averaged more than 40 percent of zinc 

and brought $15 a ton at the mine on a 35-percent 

basis with $1 per unit variation. 

Haddon also calls attention to minor shipments of 

high-grade copper ore, carload lots from the Young 

America "having averaged as high as 13.5 percent." 

Rich ore containing cuprite and native copper was 

opened in the Graphic mine in 1905 in a structural 

trough at the bottom of the oxidized zone, and "40 or 

50 cars of this ore" .in unsorted lots "netted the company an average of $1,500 per car." 

The zinc carbonate, which for the most part underlu,y the lead carbonate ore shoots, passed downward 

in part into mixed sulphide ore. Rather large ship-

. ments of sulphide ore were made from the Kelly mine 

in 1906, and the Ozark Smelting & Mining Co. was 

said to have developed about 100,000 tons of ore too 

low in grade to be shipped as zinc ore without milling. 

The Key mine in the san1e year had opened a stope 

along the "silver pipe" bed. 

The sulphide ore shipped in 1904-6 contained about 

21 to 26 percent of zinc, 12 percent of lead, 15 percent 

of iron, 1 to 3 percent of copper, 1 to 5 ounces of silver 

to the ton, a trace of gold, and 10 percent of silica. 

Oxidized lead ore shipped contained 20 percent or more 

of lead ~nd 2 to, 5 ounces of silver to the ton. The 

oxidized zinc ore contained 25 percent or more of zinc 

nnd as much as 3 ounces of silver to the ton, which _was 

uot recovered. Some siliceous ore, containing 15 to 30 

ounces of silver to the ton, evidently from the uppermost part of the Kelly limestone, was shipped from 

the Juanita mine, and one. car of ore from the Young 

America mine assayed 1 ounce of gold to the ton, 

although gold rar~ly exceeded 0.05 ounce to the ton 

in the ores shipped from the district. 

. The Waldo tunnel, driven for abo'?-t 1,700 feet to 

connect with the silver pipe bed on level 9 of the 

Graphic-Waldo mine, was completed in June 1906. 

u Statz, B. A., Geology of the Magdalena district, New Mexico: Min. 

Sci., vol. 66, p. 407, 1912. 

14 Brinsmade, R. B., op. cit., p. 49. 15 Haddon, R. W., Zinc mining in New Mexico: Eng. and Min. Jour., 

vol. 81, p. 845, 1906. 

Ore from this mine was then being dumped below the 

Waldo adit and run to the railroad terminal at the 

Graphic smelter on a 36-inch tram, and the empty 

cars were hauled back by horses. Ore frmn other 

mines was hauled in 4-horse, 5-ton wagons to the same 

terminal. Brinsmade in 1906 also mentioned the 50-ton 

Cavern mill, "the only wet concentrator in the camp" 

as having been built a few years earlier "at a cost of 

about $25,000 to clean low-grade lead carbonate ore. 

Water for power and washing was supplied fron;t a 

spring on the Cavern claims." The mill was connected 

with the mine by an inclined tramroad. He also mentjons the Hardscrabble tramroad and "the unused 

Woodland aerial ropeway." 

In 1906, 11,700 tons of zinc-lead sulphide ore was 

shipped, along with 23,000 tons of zinc carbonate, 500 

tons of lead carbonate, and 300 tons· of copper and 

siliceous .ores. The output of the Kelly mine was 

greatly increased, as was that of the Juanita, whose 

shipments included a small amount of high-grade 

siliceous silver ore, whereas that of the Graphic-Waldo . 

mine decreased. The Mistletoe mine (formerly the · • Enterprise) was being developed by the Ark Mining 

& Smelting Co., and the Cavern mine had blocked out 

a considerable tonnage of ore containing lead, copper, 

and a little gold. The Wheel of Fortune mine, in the 

adjoining Hop Canyon district to the south, was being 

developed. 

The years 1907 and 1.908 were marked by a general 

industrial depression, but the great decrease in zinc 

production in the district in 1907 was attributed ' to 

the large amount of development work and surface 

improvement by the larger companies. At the Kelly 

mine the Tri-Bullion Smelting & Development Co. 

erected a new surface plant and did 2,783 feet of 

development work. The Traylor shaft of the Kelly 

mine by that time had released a large flow of water 

that would supply its mill. The same company was 

sinking the Nitt shaft, and the Graphic mine was 

being developed from the Waldo tu11.nel. The Germany 

Mining Co. was developing the Germany and Alhambra properties and was reported to have exposed considerable low-grade ore. The Mine Development Co., 

which had been developing the Tip Top mine since 

1900, had connected the Tip Top with th,e Key 'workings, and had exposed three stopes. It had also 

completed the road from Kelly to the mine, built its 

ore bins, and begun shipping ore.16 The Magdalena 

Tunnel Co., evidently affiliated with the Mistletoe Mining Co., had purchased the Utica Nos. 1, 2, and 3 

cl~ims in the vicinity of Mistletoe Gulch. ·These companies, under management of Wm. F.Gordon, formerly 

manager of the Ozark Zinc Oxide Co., spent the entire 

year in development work, drove their main or Gordon 

1o Late new~ · from mining~· camps: The Mining World, vol. 27, pp. ·.as 

and 576, 1907. · · 
80 MAGDALENA MINING DISITRICT, NEW MEXICO 

tunnel practically to completion, and reported the 

finding of a new ore shoot. 

Mineral production in 1908 was far belo~ the average for 1904-6, but the output of zinc represented 93 

percent of New Mexico's total. The new work done 

by the Ozark Smelting & Mining Co. in the Graphic 

mine and in the Ida Hill group, which it had also 

acquired, now amounted to 6,837 feet of tunnels, drifts, 

crosscuts, and raises. The old workings of these mines 

totaled about 7 miles. The zinc and zinc-lead ores 

were sent to the company's zinc oxide plant at Coffeyville, Kans. The Tri-Bullion Smelting & Development 

Co. operated the Kelly mine for about 6 n1onths of the 

year and shipped a large tonnage of zinc ore and 

concentrates to smelters. The company's concentrating 

plant had a capacity of 100 tons a day. Zinc carbonate 

ore was shipped from the Juanita mine. The Mine 

Development Co. on the Key group shipped a few 

cars of oxidized lead-silver ore and reported a considerable tonnage as blocked out and awaiting better 

prices, evidently an over-optimistic report. The Mistletoe & Magdalena Tunnel Co., evidently a consolidation of the two companies active in 1907, had completed 

a pneumatic concentrator which operated for a while. 

In 1909 the Tri-Bullion Smelt~ng & Develop1nent Co. 

began operating its wet concentration plant with roasters and magnetic separators. The Ozark mill was 

closed in that year, while experiments were being made 

with the then new flotation process. 

In 1909 and 1910 the production of zinc approached 

its record for 1904-6 and that of lead exceeded the records for those years. Seven mines produced in 1909, 

including the Hardscrabble, Key, Old Soldier (in the 

Hop Canyon district), and the Germany, which was 

a new producer. 

The annual report of the Tri-Bullion Smelting & Development'Co. for the fiscal year ending October 31, 1910, 

stated that ores mined and milled from the Tri-Bullion 

(Kelly) group aggregated about 20,000 tons, of which 

the shipments aggregated 14,645 tons of crude ore, 

zinc and lead concentrates, and iron middlings. C. T. 

Brown, then lessee on the upper levels of the Kelly 

mine, shipped an additional 15,074 tons, and the company's net income from all ore shipped was $270,285.36. 

The milling of sulphide ores by this company began in 

January 1910, and the last crude sulphide shipped 

was billed ·January 14. The company's wet mill was 

. reported successful in the separation of lead from 

zinc and its magnetic mill in the separation of zinc 

. blende from pyrite. The mills were equipped with eight 

Traylor tables, two Deister slime tables for separating 

lead from zinc, and four Dean magnetic separators. 

The combined capacity of the mills was about 1,800 

tons per month. The Ozark Smelting & Mining Co., 

.besides shipping zinc sulphide. ore to its oxide plant 

'at ·Coffeyville, Kans., continued experiments with the 

flotation process. The Mistletoe & Magdalena Tunnel 

Go., besides ,its mine development, experimentally 

treated lead-zinc carbonate ore in a 50-ton concentrator, 

equipped with Sutton and Steele dry tables~ 

Production was much less in 1911 and 1912. The. 

Tri-Bullion Smelting & Development Co. continued to 

be the chief producer, operating in conjunction with 

lessees. Its mill in 1911 produced 7,710 tons of zinc 

concentrates, 1,404 tons of lead concentrates, 4,525 tons 

of iron middlings, and 232 tons of zinc carbonate. 

Its net income from company operation and royalties 

was $271,739. Lessees on the upper levels of tlie Kelly 

mine stopped operations in September 1911. 

The Ozark Smelting & Mining. Co. shipped lead and 

zinc carbonates to smelters, but its production of sulphide ore was evidently curtailed, pending completion 

of a new mill that was being built in 1912. The Mistletoe mill was idle. A considerable tonnage was reported 

to have been developed in the Germany mine, and 

several shipments of zinc and lead carbonate ores were 

made in 1912. The Juanita mine, which submitted no 

reports of activity to the U. S. Geological Survey in 

1909 and 1910, made large shipments of zinc and lead 

carbonate ores in 1912. 

The vears 1913-16 were marked by a great advance 

in the production of zinc, whicl;l reached a maximum 

in 1916. Production of lead and copper fluctuated 

but increased markedly on the whole and reached maximums in 1917. The increase is attributed in part to the 

Ozark mill, completed in February 1913, and to the 

demand for metals, created by the World War, which 

followed the minor depression of 1914. The Ozark 

Smelting & Mining Co., which became the leading producer in 1913, made a big increase in output in 1915. 

Its 150-ton concentration mill was operated continuously and attained a daily output of 125 tons. Its zinc 

concentrates were shipped to smelters and zinc oxide 

plants; The company also shipped crude copper sulphide, lead sulphide, zinc sulphide, zinc-lead carbonate, 

and zinc carbonate ores. · 

The.. Tri-Bullion Smelting & Development Co. operated the Kelly mine and its combination mill for only 

6 months in 1913, shipping .lead, iron, and zinc concentrates, crude zinc carbonate, lead carbonate, and 

copper sulphide ores. Shipments, according to the 

company's annual report for 1913, included 2,572 tons 

of zinc concentrates, 1,467 tons of lead concentrates, 

2,096 tons of iron middlings, 1,505 tons of copper ore, 

417 tons of zinc carbonate ore, 137 tons of zinc sulphide 

ore, and 45 tons of lead carbonate ore. The smelter 

returns on these shipments amounted to $153,861, but 

after deduction of operating costs the net loss amounted 

to $21,678. The cost of development work at Kelly 

amounted to an additional $28,208. Late in 1913 the 

Kelly mine and the mill were purchased :for $87,500 

by the Empire Zinc Co., which made several changes 
ORE' DEPOSITS 81 

in the mill. The Tri-Bullion Smelting & Development 

Co., however, retained ownership of the Nitt and adjoining claims, which adjoined the Ozark Smelting & 

Mining Co.'s ground on the north. 

In 1914 the Ozark Co.'s production came not only 

from the Graphic but also from the Waldo workings, 

which included the downward and northward contintiation of the southern shoots in the Graphic 1nine, as 

well as a smaller shoot along the Waldo fault farther 

west. A 500-foot vertical shaft was started near the 

fault. The Nitt group, which contained the northern 

ends of both ore zones, was leased to the Ozark Co .. 

by the Tri-Bullion Co. in 1914 or 1910. The Ozark 

mill was destroyed by fire on August 10, 1916, and its 

reconstruct_ion was begun soon afterwards. 

Zinc carbonate was. shipped from the Kelly mine in 

1914, but its mill underwent remodeling and did not 

resume operation until 1915. The mill was . then 

equipped with several units for the magnetic separation of magn:etite-specularite and ferruginous zinc 

blende and gravity separation of pyrite and galena; 

but the magnetic process was successful only in separating the highly magnetic magnetite-specularite, as 

there was sufficient iron in gangue material to prevent 

its electromagnetic separation from the zinc blende. 

'l'he main shoot of sulphide ore in the Kelly mine was · 

pproaching exhaustion toward the end of 1916, and 

development work had failed ' to disclose 1nore than 

small bunches of ore elsewhere. The Juanita, Gern1any, and Ambrosia mines were .minor producers during the period 1913-16. The H'ardscrabble mine, which 

had been idle since 1909, resumed production in 1916; . 

and the Black Cloud mine, adjoining the Mistletoe, also · 

began operation in that year, after building a 40-ton 

concentration mill, but it was active for only a short 

time. 

The decline in 1917 and 1918 of the war demand for 

zinc was followed by the depressions of 1919 anc~ 1921. 

In 1921 zinc production throughout the West was 

almost entirely suspended. The Ozark Smelting & 

Mining Co. was active throughout the period, shipping 

its usual variety of ores. Its mill resumed operations 

in March 1917, being equipped with a Blake crusher, 

rolls, Chilean mill, tube mill, Janney flotation ~achines, Ovoca classifiers, and Oliver filters, and continued until late in 1918. During 1919 and 1920 it 

was operated only for short periods, largely for testing 

purposes. The concentrates accumulated in 1918 and 

1919 were shipped in 1920. 

The Kelly mine and mjll were operated in 1917, but 

the magnetic mill was not operated thereafter, and 

the output of zinc carbonate ore declined. · In 1920 

several cars of zinc carbonate but only two cars of 

lead-silver ore was shipped, and the mine was idle 

throughout 1921. Other mines £rom which shipments 

were reported during the period 1917-20 were the 

Juanita, South Juanita (in 1919 only), Hardscrabble. 

Germany; and Ambrosia (l916 and 1918). The 

Graphic-Waldo, operated by the Ozark Smelting & 

Mining Co., was the only mine active in 1921. 

As the largest developed ore shoots in the Graphic-

\Valdo, as well as in the Kelly mine, had been exhaust~d at about the time of the 1921 depression, the 

district's output never closely approached the tonnage 

of the war period, even though the period 1922-29 was 

prosperous in the western mining filtates as a whole. 

The Graphic-Waldo mine was operated only by lessees 

from 1922 to 1925, and its mill remained idle. The 

Kelly mine remained idle in 1922, its milf was dismantled, and the magnetic machinery was moved to 

the Empire Zinc Co.'s plant at Canyon City, Colo. 

During the rest of the period it was worked by lessees. 

The Juanita mine was operated during every year of 

, this period by lessees, who shipped lead and zinc-lead 

sulphides, as well as the usual oxidized ores. The 

South Juanita was productive in 1927-29 and the Black 

Cloud in 1923-28. A few shipments were made from 

the Germany and the Vindicator in 1929. Slag with 

a sufficient lead-silver content to be used as flux was 

shipped from the old Graphic smelter dump at Magdttlena in 1925 and from the old dump at South Camp 

in 1926. 

The Nitt mine, which had been leased to the Ozark 

Smelting & Mi,ning Co. from 1914 to 1922, was leased 

to J. A. Macdonald of Kelly in 1923. It continued 

production for several years, although the lack of mill 

facilities restricted its operations to the selective mining of ore that could be shipped crude to smelters. 

The years 1926 and 1927 w.ere marked by brief 

rene,ved milling operations. The Ozark mill, idle 

since 1921, was set in operation on February '15, 1926, 

and was· operated at the rate of about 125 tons daily 

on low -grade zinc ore from the Graphic-Waldo mine. 

The concentrate, with a ratio to crude ore of 4.7 to 1 

and a content of 48 pe~cent of zinc, was exported to 

Belgium. The mill was remodeled in 1927 and operated from January to August. The Chilean mill was 

replaced with a ball mill, ana the Janney flotation 

machines were replaced with mineral separation machines, which together with finer grinding raised the 

grade of zinc concentrates from 48 to 52 percent. 

The ore was ground to pass completely through a 

65-mesh and 80 percent through a 200-mesh screen. 

The crude zinc sulphide ore contained 1 to 3 percent of 

lead, which was separated from the zinc-lead flotation 

product by tabling. The mill has been idle since 1927. 

The Black Cloud mill, which was operated in 1927 

and 192,8, produced several hundred tons of 45-percent 

lead concentrate from lead carbonate ore. The ore, 

which a1so contained some galena, anglesite, quartz, 

and iron oxide, was sulphidized in a 5-foot agitator,' 

tabled, and floated. At the Kelly mine (Hughes lease) · 
I 

r 

82 MAGDALENA MINING DIS'l'RICT, NEW MEXICO 

lead carbonate ore was tabled during the first quarter year. In 1939 the Oro Alto Mining Co. shipped goldof 1927 and made a 43-percent concentrate. Shipments silver-lead-copper ore from a property south of Kelly, 

were made by R. R. Foster from the Bla<6k Cloud tail- and small shipments of smelting ore were reported 

ings pile, the Juanita mine dump, and the slag dumps from other properties. Several lots of silver-lead ore 

of the old Kelly (Graphic~) .and Socorro smelters. were shipped from dumps during the period 1934-39. 

The output of the district was less in 1928 than in In the Water Canyon district the Open Cut mine 

any previous · year for which records are available, was active during 1935, 1937, and 1939, arid experiexcept the depression years of 1907 and 1921. Lead mental concentrations of its gold -silver ore were underore dominated in 1928 and 1929, and the output of taken. Small shipments of silver-lead and high-grade 

gold was more than usual in 1928. The Waldo work- gold ore were made from the Queen property in 1935, 

ings below the tunnel level, which had been allowed to 1936, and 1937, and a 4-ton shipment of lead ore was 

fill ~ith water in 1928, were unwatered in 1929 but, made from the Balakohna No. 1 claim in 1937. 

owing to the outlook of the zinc market, were allowed It thus appears that the Magdalena district and the 

to fill again. The mine then remained idle until April adjacent areas will continue to be small producers until 

1937, although some dump ore was shipped by lessees. the demand for zinc justifies the resumption of milling 

The Nitt and Juanita mines continued to be operated . and of developments in relatively little explored parts 

by lessees in 1928-30, and occasional shipments were of the district. As shown elsewhere, there is reason 

made by the South Juanita in 1927-28 and by the to expect substantial reserves of zinc-lead sulphide ore 

Germany and Vindicator in 1929. in at least three mines-the Graphic-Waldo, LinchThe district had thus become essentially dormant burg, and Grand Ledge-Cavern-but production from 

before the beginning of the great depression in the fall them must await times that will justify the necessary 

of 1929. Only one carload of ore was reported from ·reclamation of flooded and caved workings and the 

the district in 1931, and the 804 tons reported in 1932 explor~tion of promising undeveloped ground. 

probably consisted largely of gold ore, with probably · 

small amounts of silver, lead, and lead-zinc ore. 

Some recovery was made in 1933 and 1934, and 

annual shipments from then until 1939 fluctuated between 1,110 and 5,525 tons. The Kelly mine was 

worked intermittently under the Hughes lease from 

1928 until 1939. Its output was mainly zinc-lead sulphide ore, which was shipped to Coffeyville, Kans., 

whereas its silver-lead-copper ore was shipped to El 

Paso. The Graphic-Waldo mine was reopened in April 

1937 and was active until Februa:ry 1938, and again 

during the last quarter of 1939. Zinc and zinc-lead 

ores mined by the company and lessees were shipped to 

Coffeyville, Kans. Other mines active during the interval 1934-39 were the Morning Star, which made 

small shipments, chiefly of gold ore, to the El . Paso 

smelter in 1934-36, and the Mistletoe mine, which was 

active during part of 1938 and produced most of the 

gold-silver-lead ore shipped from the district in that 

PRODUCTION 

Events cited in the foregoing pages are summarized 

in the accompanying table (pp. 84-85) which shows the 

output of. Socorro County froni 1881 to 1940 and that 

of the Magdalena district from. 1903 to 1940. Figures 

for the years 1881-1902 in the table were compiled by 

F. B. Blackson, under the direction of C. W. Henderson, 

of the United States Bureau of Mines, from records of 

the United States Mint at·Denver, Colo. Collecting of 

detailed records of ore and metal output was begun by 

the Division of Mineral Resources, United States Geological Survey, in 1903 and continued until 1924, when 

that division was transferred to the United States Bureau of Mines, which has continued the work. The 

'records for New Mexico have been compiled for both 

bureaus since 1907 by C. '\V. Henderson, who has kindly 

supplied all the data tabulated in this report. 

S?corro Coun~y was organized about 1881, and any 
PRODUCTION 83 

metal produced before ·that year may have been credited to Grant County. 17 Socorro County at first included also the present Sierra and Catron Counties,18 

but in the accompanying table the output of those 

counties has been deducted by Henderson, so the figures 

represent only production within the present area of 

Socorro County. 

Steady production in the Magdalena district probably began in 1881, when Gustav Billings began to 

operate the Kelly mine. The lead output in Socorro 

County from 1881 and the zinc output from 1900 to 

the present time have been entirely from the Magdalena district, with the exception of a few trivial amounts 

of lead noted in the table. Comparison of the ratios 

of gold and silver to lead in the earlier years with 

those in the years when separate figures were tabulated 

for the Magdalena district shows that the output of 

gold and silver in the county came largely from other 

districts until 1900. No estimate of the Magdalena 

output of gold and silver for the early years is worth 

attempting, however, as some of the oxidized lead ore 

mined then was evidently rather rich in silver and a· 

few small shipments of siliceous and copper ores were 

unusu~lly rich in gold. The other districts continued 

t9 contribute to the gold and silver output of the 

county until 1914 and made minor contributions to the . 

copper output until 1917, but the total metal output 

of the county since 1902 is only little greater than that 

of the Magdalena district. 

The total value of the Magdalena output to 1904 was 

estimated by Jones 19 to be $8,700,000, of which 

$5,800,000 was credited to the Kelly and Graphic mines. 

11 Burchard, H. C., op. cit. for 1881, pp. 339- 340, 1882. 18 Burchard, H. C., op. cit. for 1883, p. 601, 1884. 19 Jones, F . A., New Mexico mines and minerals, p. 119, Santa Fe, 

N. l\Iex., 1904. 

Brinsmade 20 estimated the total value. to be $6,600,000, 

to which the Kelly and Graphic mines contributed 90 

percent. The accompanying table, which makes no 

allowance for any small shipments between 1866 and 

1880, shows a total value of $6,548,068 for the output of 

the entire county from 1881 to 1903 inclusive and therefore agrees closely with Brinsmade's, estimate. The 

small extent of the workings, other than those of the 

Kelly and Graphic mines, and the little success experienced in early efforts to treat the ore implies that 

the quantity of unaccounted ore could not have been 

very great, and the rounded figure of $6,600,000, therefore, appears to be essentially accurate. 

The bulk of the output of all the metals recorded 

has come from the Kelly and Graphic-Waldo-Nitt ore 

bodies. From 1903 to 1939, inclusive; these. mines 

accounted for 87 percent of the ore mined, 22 percent 

of the gold, 76 percent of the silver, 98 percent of the 

copper, 98 percent of the lead, and 99 percent of, the 

zinc recorded. The Juanita mine contributed 2.7 percent of the ore mined and the remainder comprised 

small shipments from the other mines listed in the 

table on page 86. Shipments made in 1904 and later 

years are tabulated or quoted in the mine descriptions 

on pages 124-158. 

The figures for the Magdalena district, w hi_ch are 

quoted from Henderson's annual chapters in · Mineral 

Resources of the United States and the Minerals Yearbook, include small -shipments f~om the adjoining 

vV ater Canyon and Hop Canyon · districts and from 

othlr claims in the vicinity whose locations have not 

been definitely given. All of these shipments that have. 

been reported from 1905 to 1939 are recorded in the 

table on page 86. For the most part they appear to 

20 Brinsmade, R. B., op. cit., p. 49, 1906. 
84 MAGDALENA MINING DISrrRICT, NEW MEXICO 

Production of metals in Socorro County and Magdalena mining 

[Compiled under direction of C. W. Henderson, Geological Survey 

Year 

Ore sold or treated 

(short tons) 

Gold 

Fine ounces 

Silver 

Value Fine ounces Value 

---------~------- --------.---------l---------~-------1------------------- -------~--------·--------

County District County District County District County District Average County District 

------------------ ----- ----------·-----11------·1-·- ------------ 1881_ __________ ____ ______ __ ------------ ----- ------- 48.37 $1,000 ------------ 53, 097 ------------ $1.13 $60,000 ------------ 1882 _____ ·---------------- - ------------ ------------ 145, 13 3, 000 -- -- -- ------ 301,755 ------------ 1.14 344, 001 ------------ 1883_ ---------------------- -------- ---- ------------ 188. 63 3,900 ------------ 262,562 ------------ 1.11 291,444 ------------ 65,500 ------------ 439,440 ------ -·- ---- 1.11 487. 779 ------------ 147,500 ------------ 46R,829 ,_ ___ _____ ___ 1. 07 501,647 ------------ 1884_ ---------------------- ------------ ------------ 3, 168. 84 1885 ___ -------------------- ------- ----- ------- - ---- 7, 135.94 

1886_ ---- ------ ------------ ------------ ------------ 2, 822. 64 58,344 ------------ 221,643 ------ ------ 0 97 214,. 994 ------------ 1887 _______________________ -------- ---- ---- -- ------ 3, 564.58 73,680 ------------ 220,555 ------------ 0 98 216, 144 ------------ 1888 __ --------------------- ------------ ------------ 2, 278. 32 47,000 ------------ 15,820 ------------ 0 94 14,871 -·----------- 144,500 ------------ 25,065 ------------ 0 94 23,561 ------------ 1.800 ------------ 123, 551 ------ ------ 1. 05 129,729 ------------ 1889 __ --------------------- . ---.------- --------- --- 6, 990. 80 

1890 ___ -------------------- ------------ ------------ 87.08 1891_ _________ ____ _________ ------------ ------------ 2, 007. 74 41,500 ------------ 64,572 ------------ 0 99 64,025 ------------ 1892 _____ ------------------ ----- ------- ------------ 1, 731.97 35,800 ------------ 32,287 ------ ------ .87 28,090 ------------ 1893 _______________________ ------------ ------ ------ 2, 418. 96 50,000 ------------ 12,970 ------------ 0 78 10,116 ------------ 46,450 ------------ 25,238 ---- -------- 0 63 15, 900 ------------ 110,000 ------------ 64, 176 ------------ 0 65 41,714 -- ---------- 117,600 ------------ 70,794 ------------ .68 48, 140 ------------

1894 _______________________ ----- -- ----- ·----------- 2, 249.63 1895 ________ _______________ ------------ ------------ 5, 321. 72 

1896_------------- --------- ------------ ------------ 5, 689. 40 1897 _________________ -- ---- ------------ --- --------- 6. 0~2. 24 125,700 ------------ 141, 732 ------------ 0 60 85,039 ------------ 103, ~20 -------- ---=- 179,011 ------------ . 59 105, 616 ------------ 116,680 ------------ 187,788 ------------ 0 60 112,673 I . 

~~gg=====~·= ==~====~~~~~~~~= ~=~~~~=====~ ===~=~·~=~= ~= ~: :~: ~~ ------------ 36,549 ------------ 47,969 ------ ------ 0 62 29,741 ------------ 19,057 ------------ 66,278 

~~~~~~~~~~~~/ .60 39,767 ------------ 42,056 ----------- 146,503 0 53 77,647 ------------

1900 ___ -------- ------------ ------ ------ ------------ 1, 768. 21 1901_ ____ ______ ____________ ------------ ------------ 921.96 

1902_ ------------ ---------- ------------ ------------ 2, 034. 63 

1, 391,436 ----------- 3, 171, 735 ------ ------ -------- -- 2, 942,638 ------------ ---===-======= ==== Total, 1881-1902_ __ __ __ _ ___ ___ _ __ __ __ __ ___ ___ 67, 324. 90 

=======:======!========!====== 1903 (3) (3) 234.20 4. 5 4, 841 $93 58,805 34,504 0 54 31, 755 $18,632 

1904-= ~ ~ ~ = = = = ~ ~ = = = = = = = = = = ~ = 33,789 27,998 1, 920. 27 7.44 39,692 154 6, 457 5,024 0 58 . 3, 745 2, 914 

1905.------------.--------- 33,913 30,411 980.97 ------------ 20, 277 ------------ 4, 810 4,800 0 61 2, 934 2, 928 1906 ___________ ____________ 35,478 35, 47~ ------------- . ----------- ·------- ----- - ------------ 2, 515 2, 515 .68 1, 710 1, 710 

1907----------- -------: ---- 3, 776 3, 630 0 63 0 63 13 13 4, 406 4, 406 .66 2, 90~ 2, 908 1908 ___ ________________ ·--- 9, 302 11, 319 990.42 3. 48 20,472 72 1, 152 460 .53 610 244 1909 _____ ------------0----- 35,1141 30,724 1, 211. 17 21.04 25, 035 435 19,648 17,925 0 52 10,217 9, 321 1910 ___ ___ ___ ____ _______ __ _ 43, 52~ 42, 232 334. 01 22.64 6, 904 468 66,331 65,880 .54 35, 819 35,575 1911 _________________ ------ 211,330 2-5,1140 140.05 17.08 2, 895 353 42,907 42,773 .53 22, 741 22,670 1912 _______________ -------- 22,659 22, 590 37.30 36.09 771 746 33,271 32,792 0 615 20,462 20,167 1913 _______________________ 47, 6116 47, 1147 192.06 190. 7l 3, 970 3, 942 40,394 40,212 0 604 24,398 24,288 

1914_-- -------------------- 51,595 51, 5!l5 109.58 109.58 2, 265 2, 265 14,436 14,436 0 553 7, 983 7, 983 

191!i_-- ------------------- - 7!\, 463 75,401 23.61 23. 61 488 488 56,941 56,897 0 507 28,869 28,847 1916 _______________________ 78,766 ,78, 1169 P9. 58 98. !iS 2, 058 2, 0311 73,228 72,887 0 658 48, 184 47,960 

1917------------- ---------- 100, 795 100,709 105. 76 105.76 2,186 2,186 137, 250 137, 114 .824 113, 094 112,982 

1918 __ --------------------- 511,495 56.295 20.80 20.80 430 430 49,976 49,835 1.00 49,976 49,835 

1919_ ---------------------- 13, P38 13, 938 .48 0 48 10 10 30, 117 30, 117 1.12 33, 731 33,731 

1920_ ---------------------- 17, 235 17; 235 -------------- ------------ ------ -------- --- -------- 18,367 18,367 1.09 20,020 20,020 

1921_ ---- -- ------ -- ------ -- 412 . 412 ------- ------ . ----------- ---- ---------- ----------- 155 155 1.00 155 155 

1922_---------------------- ~. 304 R, 304 10.01 10.01 207 207 6, 156 6, 156 1. 00 6,156 6,156 

1923 ___ -------------------- 10,117 10, 117 22.01 22.01 455 455 15, 721 15, 721 .82 12,891 12,891 

1924_- --------------------- 11, 12R 11, 128 9. 63 9. 63 199 199 10,643 10, 643 0 67 7, 131 7, 131 1925 _____ ___________ . _ -- -- -- 12,398 12,356 5.5. 83 55.83 1,154 1, 154 25,182 25,073 .694 17,476 17,401 

.111_-:E __ : ~:-~~~-! 43,414 43,414 29.32 29. 32 e.o6 1101\ 14, 575 14, 57fi 0 f\24 9,095 9, 095 

41, 702 41,702 37. 49 37.49 775 775 70,478 .70, 478 0 567 39, 961 39,961 

6. 798 6, 798 95.78 95.78 1, 980 1, 980 16, 183 16, 183 0 585 9, 467 9,467 

5, 762 5, 726 13.98 13.79 289 285 15, 060 15, 032 0 533 8,027 8, 027 

5, 947 5. 805 5. 46 5. 26 113 109 7, 426 7, 808 0 385 2,859 3. 006 193L _________________ ___ __ 38 Nove None None None None 62 None 0 290 18 None 1932 ________________ ___ ____ 804 1'44 77.75 22. 69 1, 607 469 1, 500 142 0 282 423 40 

1933_ ---------------------- 5,529 5. 525 6. 92 0 92 143 1!) 120 117 0 350 42 40 

1934_- --------------------- 3, 640 3,161 161.00 6. 30 5, 627 221 1, 949 61 0 646 1, 260 39 1935 ______________________ _ 6, 676 2,115 550.89 60. 80 19,281 2,128 5, 938 911 .717+ 4, 268 655 

1936_---------------------- 20, 018 1, 664 1, 812.40 34.07 63,434 1, 192 5, 791 317 0 7745 4, 485 246 

1937---------------------- - 35,757 5, 151 I, 758. 00 39.17 61,530 1, 371 7, 219 3, 969 0 7735 5, 584 3,070 1938 __________ _______ __ ____ 1, 239 1,110 108.80 61.20 3, 808 2,142 268 149 .646+ 173 96 

1939_ ---------------------- 2, 559 2, 015 147.00 79. 00 5, 145 2, 765 1, 905 937 .678+ 1, 293 636 

1940_ ---------------------- ------------ ------------ -------------- ------------ -------------- ------------ -------------- ------------ ---------- -------------- ------------

::::~ :::: -:: ~<:::;;! :: :: :::::: :::: :::::::::::::::::::: 1: ::::: :::::::: :::::::: :~::;; ::: : ::1::::~:::::: ---------- -------------- ------------

-------------- ------------

t Practically no zinc. 2 Small shipments of zinc . 3 500 pounds valued at $72 mined outside Magdalena district. s 44,563 pounds valued at $3,164 came from outside Magdalena district. 6 10,000 pounds valued at $870 mined outside Magdalena district. 7 23,700 pounds valued at $1,185 mined outside Magdalena district. 4 1,136 pounds valued at $50 came from outside Magdalena district. 
PRODUC'riON 

district, New Mexico, 1881-19.1,0, in terms of recovered metals 

and Bureau of Mines, U.S. Department of the Interior, Denver, Colo.] 

Copper Lead 

85 

Zinc 

-----------------------------------------------------------------1 Total value 

· ~ounds Value Pounds Value Pounds Value 

-------.---------1----~-----.-----1·------ -----------------------------------

County District Average County District County and 

district Average County and district 

County and 

district Average County and 

district County District 

-----------------------1------:------------------1----------·-1·-----1'-----·1---------

-------------- ------------ ------- --- -- ------------ ------------ -------------- ---------- -------------- --- --------.,.. -- - --- ----- - ---- ------- $61' 000 ------ ... ----- -------------- ------------ --- ------- -------------- ------------ -------------- ---------- -------------- ------- ------------ ----- -- --- --------- 347,001 ------------ -------------- ------------ ---------- -------------- --- --------- 1, 764,864 $0. 043 $75, 889 ----------- -- - --- ---- -- - ------ -------- 371, 233 ------------

-------------- ------------ ---------- -------------- ------------ 4/ 204, 200 . 037 155, 5t15 -------- ~- --- ---------- -------------- 708,834 ------------

= = = = = = = = ===== = = = == === = === = = == = == == == = = === = = = = = = = == == = = == = == = == ~; ~~~; ~gg : g:~ i~~; ~~i = = = = =·= == = == = =: = == = = = = = = = = == = = = == = == = = = ~~~; ~g~ = == = == =: =: = = -------------- ------------ ------- --- ------ -------- ------------ 5, 132, 628 ". 045 230, 968 - ------------- -------- --]-·----- _. __ ----- 520, 792 ------- ---- -

-------------- ------------ ---------- -------------- ------------ -------------- ------ ---- -------------- -------------- ---- - ----- - -- ----------- 61,871 ------------ -------------- ! ___________ ------- - -- -------------- -----~------ 3,415, 790 .039 133,216 -------------- ------------------------ 301,277 ------------ -------------- ------------ ---------- -------------- ------------ 935,162 . 045 42,082 ------- --- --- ---------- -------------- 173,611 ------------

-------------- ------------ ---- ~ ----- -------------- ------------ 511, 694 . 043 22, 003 ------ ----- .. -- ---------- -- - - ---------- 127, 528 ------------

-------------- ------------ . ------ -- - --- - ---------- ------------ 2, 125,000 . 040 85, 000 -------------- ---------- -------------- 148, 890 ------ - -----

-------------- ------------ - ----- ---·- -------------- --- -------- - 1, 250,000 . 037 46, 250 --------- ----- -- - ---- --- -------------- 106, 366 --------- - --

-------------- ------------ - -- -- - -- - - - ------------- ------------ 833,334 .033 27,500 -------------- ---------- -------------- 89,850 ------------

-------------- ------------ ---------- -------------- ------------- ------------ ---------- -------------- ----------------- ------ - -------------- 151,714 ------------ -------------- ------------ ---------- -------------- ------------ 1,813, 772 .030 54,413 (1) ---------- --- ----- -----~ 220,153 ------------ -- --------------------------- - -- - ----------------------------- 4,483,294 .036 161,.399 (1) ------------------------ 372,138 ------------

-------------- ------------. ---------- -------------- ------------ 2, 501,828 . 038 95, 069 (1) -- -------- ---------.---- 304,505 ------- -----

------8ii; i35- ===== === ==== -$6~ iiiii- -----$134; ii4R- ======== ==== 

2

' ~~~; ~~~ I : g:~ ~~; ~~~ ------(2

) ------ : === === === ====== =======: ~~5; ~~~ ========== == 727,273 ---------~-- .167 121,455 --- -------- - 534,884 . 043 23,000 (2) -- -- - ----- -------------- 203,279 ------------

540,000 ------------ .122 65,880 ----------- - 1,189,004 .041 48,749 (?) ------------------------ ---~_i332 ~~ 

_ _:~8, 40~ -=-=~-=-=-=-= -=-=-=-=-=-=-=-=-=-= --~1, 98~ -=-==-=-=-=-=-=-=-=-=-= =!~~~~~~-=-=-=-=-=-=-=-=-=-= ---~~~ 875 -=-=-=-=-=-=-=-=~-=-= ~-=-=-=-=-=-=~-=-=-=-=-=-=-=-=-=-= --~~ 932 -=-=--=-=-=-=-=-=-=-=-=-= --6oo, ooO ~=== --~7 --82,200 ~=-~~~ --1;050,00o --~042 ---4~1oo --~856, 297 -$0.054 --$Ioo:-240 ---ia,-136 - $16a:065 

3, 200 ' 3, 200 . 128 410 . $410 688, 209 . 043 2!l, 593 13,493, 835 . 051 688, 186 761, 626 721,257 

320,000 320,000 .156 49, 920 49,920 390,000 . 047 18,330 14,-630,051 . 059 863, 173 954,634 934,351 

64, 560 64, 560 .193 12,460 12,460 238,088 . 057 13, 571 17,044, 163 . 061 1, 039, 694 1, 067,435 1, 067,435 

38, 645 24, 045 . 200 7, 729 4, 809 707, 981 ' . 053 37, 523 676, 356 . 059 39, 905 88, 078 85, 158 19, 462 2, 605 . 132 2, 569 344 16, 073 . 042 675 3, 325, 446 . 047 156, 296 180, 622 157, 631 170,792 170,792 . 130 22, 203 22, 203 3, 085, 279 . 043 132,667 12,878,241: . 054 695,425 885, 547 860,051 

152, 284 152, 181 . 127 19,340 19,327 4 3, 4ij2, 364 . 044 4 151, 904 16,727,870 . 054 903, 305 1, 117, 272 1, 110, 529 77, 448 77, 448 . 125 9, 681 9, 681 2, 123, 039 . 04-~ 95, 537 9, 930, 281 . 057 566, 026 696, 880 694, 267 89, 592 69, 532 . 165 14, 783 11, 473 2, 192, 792 . 045 98, 676 9, 962, 478 . 069 687, 411 822, 103 818, 473 285, 148 278, 252 . 1.55 44, 198 43, 129 2, 198,030 . . 044 96, 713 13,267,811 . 056 742,997 912,276 911,069 

214,722 214, 722 . 133 28, 558 28, 558 674, 205 . 039 26, 294 13,,Z85, 17& . 051 703,044 768, 144 768, 144 1,416,098 1,406,789 .175 247,817 246,188 2,031,297 .047 95,471 18,437,218 .124 2,286,215 2,658,860 2,657,209 

1, 012,406 993, 199 . 246 249,052 244,327 4, 421, 290 . 069 305, Ofi9 1g., 312, 179-- . 134 2, 587,832 · 3, 192, 195 3, 187,226 

2, 699, 333 2, 690,381 . 273 736,918 734,474 4, 885, 210 . 086 420, 128 14,716, 74fj . 102 1, 501, 108 2, 773,434 2, 770,878 

585,482 585,482 . 247 144,614 144,614 53, 078,098 . 071 6 218, 545 11, 501, 879' . 091 1, 046,671 1, 460, 236 1, 456,931 

599, 382 599, 382 . 186 111, 485 111, 485 ' 819, 566 . 053 43, 437 2, 995, 740 . 073 218, 689 407, 352 407, 352 311, 663 311, 663 . 184 57, 346 57, 346 ..... 873, 012 . 080 69, 841 3, 764, 235' . 081 304, 903 452, 110 452, 110 None None - None None 60, 7U . 045 2, 732 133,000 . 050 6, 650 9, 537 9, 537 8, 063 8, 063 . 135 1, 088 1, 088 923, 541 . 055 50, 795 3, 119,298 . 057 177,800 236,046 236,046 

50;388 50, 388 .147 7, 407 7, 407 l, 506, 829 . 070 105,478 3, 421,000 . 068 232, 628 358,859 358,859 

94,626 94,626 .131 12, 396 12,396 1, 636, 825 . 080 130,946 3, 823-;800 '065 248, 547 399, 219 399, 219 83, 300 82,800 .142 11,757 11,829 6 2, 44~ 600 . 087 6 212,680 3, 170,000 . 076 240, 920 484,059 483, 042 56, 714 56,714 .140 7, 940 7, 940 . 1, 400, 200 • 080 112,016 8, 013, 300 f • 075 600, 997 730,654 730, 654 173,817 173,817 .131 22,770 22,770 1, 637,667 . 063 . 103, 173 4, 430,000 . 064 283,520 450, 199 450, 199 128, 327 128, 327 .144 18,479 18,479 991, 207 . 058 57,490 339,000 . 061 20,679 108, 095 108,095 

174,483 174,483 .176 32,469 32,469 961,270 . 063 60,560 254,000 . 066 16,764 118,109 • 118.105 72, 900 .52, 100 . 130 9, 477 6, 513 7 982, 300 . 050 7 49, 115 1, 470, 000 . 048 70, 560 132, 271 127, 971 

20,000 None . 091 1, 820 None s 8, 700 . 037 ' 322 -------------- ---------- -------------- 2, 160 ' None -------------- ------------ ---------- -------------- ------------ 113-,000 . 030 3, 390 233,000 . . 030 6, 990 12,410 10,889 -------------- ------------ ---------- -------------- ------------ 92/f, 000 . 037 34,225 2, 012,000 . 042 84,504 118,914 118,788 

7, 600 None . 080 608 None 9 458, 300 . 037 9 16, 957 1, 132, 000 . 043 48, 676 73, 128 65, 719 1, 000 1, 000 . 083 83 83 10 277,200 . 040 10 11, 088 701,000 . 044 30,844 65, 564 44,266 

1, 000 1, 000 . 092 92 92 211, 500 . 046 9, 729 566,000 . 050 28,300 106,040 39, 559 12,300 6, 300 . 121 1, 488 762 11 287,300 . 059 11 16, 951 1, 510,000 . 065 98, 150 183,703 119,950 700 150 . 098 69 15 12 14, 200 . 046 12 653 435, 000 . 048 20, 880 25, 583 23, 648 9, 000 4, 600 . 104 936 478 13 200, 000 . 047 13 9, 400 633, 000 . 052 32, 916 49, 690 45, 518 

-------------- ----.-------- ---------- -------------- ------------ -------------- ---------.- -------------- -------------- ---------- -------------- -------------- ------------

=== == =====~~==~A~~~~;;l;~~=~~=~~: :::::::: :::::::: :::: ::::::::: ::::1::::::: :::: s 8, 700 pounds valued at $322 mined outside Magdalena district. u 4,700 pounds valued at $174 mined outside Magdalena district. 

1014,300 pounds valued at $572 mined outside Magdalena district. 

11 6,000 pounds valued at $354 mined outside Magdalena district. 12 3,000 pounds valued at $138 mined outside Magda-lena district. 13 14,400 pounds valued at $677 mined outside. Magdalena district. 
86 

Year 

MAGDALENA MINING DISfl'RICT, NEW MEXICO 

Ore shipped from small properties, mostly in outlying districts, 1905-39,1 and gross metal content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of Mines, U : S. Department of the Interior, Denver, Colo.] 

Shipper Mine or claim District Ore (short tons) 

Gold, Silver Copper Lead Zinc (ounces) (ounces) (pounds) (pounds) (pounds) 

--------·----------l---------·----·l---------1-------------------------

1905 D. de Grazia __________ _______ _____ ____ Wall Street_ _______ ___________ __ _ Water Canyon _______ _ 60 

1 

3 

25 

48 

13 

1o. OO 10 --- ------- -.-----c--- ---------- 1907 R. E. Johnson _____ ___ ____ ___________ ________ _____ ___ ___ ___ ________ _____ _ (?)_ ----- -- ------------

1908 t == = = = = === = == = = === === = == = == = = == = === = = = = ~~~~1° o~p;~~f~ne~ = = == = == = = == = == = 

Water Canyon _______ _ Mill Canyon _________ _ 1909 

1910 

1911 

1912 

1913 

1915 

1916 

1917 

1918 

1919 

1922 

1923 

1924 

1925 

1926 

1927 

1928 

1929 

1930 

1932 

1933 

1934 

1935 

1936 

1937 

1938 

1939 

__ __ _______ ____ ·_ __ _ __ _ _ __ ___ _ __ _ _ __ _ _ __ _ Old Soldier. ___ __ ________________ _ . __ .. do ..... .. __________ _ 

{~·- Walker ~~ ~~~~ ~~~ ~- ~~-~,~~~~~--========= -aoi<i-:Doilar============ ===== ===== _ ~~~~~ -~~~- ~~)-===== === & Schneider. ______________________ ________ _______ _______ _____________ .do ___ _____________ _ W. H. Brittemtein ------ --- -~------ ----------- ------------------------ __ ___ rlo ________________ _ _____ ___ _ __ _ _ ______ ______ ___ _______ _ ___ Pueblo Springs ______ _______ _____ . Water Canyon (?) ____ _ 

1

-------------------------------------.. . Wheel of Fortune ____ _______ _____ Mill Canyon _________ _ 

'L." 'R." "Bai)cork: = == = = = == = === ==== ==== === . ~~~ = = ~ ~ ~ ~ = ~ = = ~ ~ ~ == ~~ ~ = ~ ~= = = ~ == _ ~o~ ~~~ _ ~~)-= == = = == = 

{~~~~w;i~~-~~~~~~-~ ~~~1-t~~~ ~~= = <?>~=== == == == ==== === == == === ==== ~>~-~~~~~~~========= 

l~'?·~tttm HiH & Hedrlerman ____ _-m= ---------------_iiH~J~j~;£1~~n·~= -- __ _ _ ___ _ ___ _ ___ ___ =~___ -==__ __= _____:===i_===J~~b~J:lJ~ ____ (?) . _______ -------~- -~=- ----

= = == === = = ==: = == = == = === = = == ==== == = = == == = -~~~~~~!~~~:~~~= ==== = =: == = =====: -~~:~~ ~a~~~~~~~= ==: I' Silver Mountain Mining Co ... -------- ----------------- ------------------ Water Canyon ___ __ __ _ --------------------------------------- Wheel of Fortune ____ ___ _________ Mill Canyon _________ _ --------------------------------------- Gold King (Maggie Merchant) ___ Water Canyon __ __ __ _ _ Pederson & Gilbert____ ______ ____ _____ __ ___ _ _______ _______ _ __ _ ___ _ ___ ____ (?) ___ ___ ____ _____ ____ _ North Star Mining Co. __ ___ ---------- _____ _ _ ___ ___ _ __ _ _ __ _ ___ _______ ___ _ (?) _______ __ ____ ___ __ _ _ 

G. H. O'Brien ___ ___ __ ------------------------------------ ____ __ ______ ___ ------------------------ -_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ ____ _ _ _ ___ ___ _ _ __ _ Sampson._____ ____ __________ _____ Magdalena __ __ _______ _ 

l~~~;~~~J'?~: ~: :~~:: =~:= =~~~ :::~ -;;ii;'~,~~~~~~~: =~: ~ :~: :: ~: ~- -~i~d~~;~~:~ ~: ~ ~: ~ ~: Copper Belt Silver & Copper Co___ ___ Chief group___ __ ________ __ _______ North Magdalena ____ _ 

~~.~~~f~~~~~~~ ~~~ ~::: ~:: ~ ~::: ~ ~ _ ~·~~~ng; st~ ; in::: :: ::=~~ ~~ ~:::: :j:~~~i,) ::: ~ ~ ~: ; Ian MacTavish.---------------------- Anchor (?) -- ---- --- -------- ------ Magdalena __ __ _______ _ {W. R. Dobson. _____ _ ----------------- (?) _____ __ ------~--- ---- ----- _____ do, _______________ _ \.Alta Vista Co___ ____ ______ ______ ______ Smelter slag ______ ---------------- __ __ _ do ____ __ ____ ______ _ 

{~m~foF~t:~~zc_==~ = = = == = = === == = == === m~~~- ~:~! === = ==== = ========== === ~-~~~ ~~~- ~~~ = = ===== = 

1 ~l:~::;~ -= ~= ~ ~ ~~ ~ ~:: ~= ~ ~ ~ ~~ ~ ~ ~ _ r~:~~~; ~=~~ ~ ~ ~ =: ~ ~ ~~ ~ : ~:: ~ ~[\~~ii~~~= = ~ ~ ~ ~ ~= el_t~~~s_t~ ~~======= ====== == == == == == ~~l~t~~:1Maggie :Merciia'llt)-_== ~:f!a~~~Y'oii ======= 

{~~~ _V:.~ ~_e_r_-====== === ==== ==== ==== === a<>i<i Killi (Maggie-:Mercila'llt)-_ ~ Wa.fer-caiiyoii====== == 

{'R:'f ~Wfl(Ie_r __ ==== === ==== = === ==== = === == == == = ---== == === === = ========= ===== -(?)= ~-~---==== ===== == :: == 

1

------------_ -------------------- ____ __ Gold King ______ _________ ____ ___ _ Water Canyon ____ ___ _ 

~~~:~i~:~:~~~l~~~~ ========= = ==== === m = === =========== === = === ======= == -~~:~1~~:~~~~======== {= = === == == ======== === = ==== ====== ==== ==== ~t~~d~i~~e~~~(-~-~- -~~ -~~~~~~~= == == = ~~========= ======== 

1 ~~~~~~~~~ih:==::: ~ ~ :: ~~ ::::: :~ ~ . *~J~~.n~~; -~ ~ ~: ~: ~ ~ ~: ~::- ::-:: : ~:&~~~~: ~;~: ~ ~=~ ~:~ 

m~~~~~ti;~~.fHh~~~i =~ ~~i~~UH~~~~~// <~t~~~~.n~===~~= {~~l~~:~i~~d~-===================== McCarthy & Phillips.---------------- ~¥~~~-~;~~~=-~~================ (?) ________________ ______ ______________ :i!i:~~~~~~======== do ________________ _ Cleto Tafaya________________ __________ New State group _____________ ________ _ do ______________ ·--1 • . __ .do _____________ _________________________ do ______________ __ _____________ ___ .do ________________ _ J.D. Torres _________ __________________ (?) ________________________ _______ Magdalena(?) _______ _ Hey Hall_____ ______ __ _____ ____________ Balakohna. _ _ _ ___ _ __ _ __ __ __ _ _ ___ _ Water Canyon. ______ _ MacTavish & StendeL.-- --- ---- -- Stendel open cut ______________________ do ___ ------------- York Sales Co_________________________ Plata____________________ ___ ____ __ Magdalena ___________ _ Victor Pappy __ ----------------------- Queen_____________________ _____ __ Water Canyon. ______ _ 

I~:~~i~I~~~-~=: ~ ~~~= ~ ~ ~ ~ = = ~ ~ ~ ~ ~ ~~~~EJ,~-~ ~~~ ~ ~ ~ = =: ~: = = = = i~~ ~ = -~;t~~~~-~ \ ~ ~ ~ i i-

{

Roy StendeL _______________________ __ Stendel open cut.·---- -- ------- Water Canyon _______ _ 

~~ri~~es~ ==== ============= === ==== ~:t~ ~~~~t~t~~~s)~~~~ ~======== =====~g================= 

2 

5 

205 

11 

14 

16 

4 

20 

16 

9 ~ 46 

151 

21 

18 

88 

11 

22 

13 

9 

44 

2 

21 

30 

.33 

53 

34 

29 

10 

3 

17 

1 

4 

2 

35 

143 

324 

2,106 4 13,790 2 3,121 23 1,028 9 

166 

23 

6 

118 

21 (3) 

(3) 

(3) 

14 

4 

5 

2 

13 

17 

19 

40 

71 

11 

19 

17 

240 

34 

59 

66 

3 

4 

9 

27 

4 

13 

6 

6 

12 

3 

4 

67 

30 

62 

20 

t No ore shipped in 1914, 1920, 1921, and 1931. l Credited to Magdalena by smelter. 

3 75 ----- ----- ---------- 11 157 2,186 ---------- 3.50 350 3,288 -------------------- 1.00 124 19,258 ---------- 2.47 1,013 1,585 5,359 ---- c-----

1.20 50 ---------- ---------- ---------- 14 162 2,389 ------ ----

---------- ---------- ---------- ---------- 357,854 1.19 135 942 ---------- ---- ------ ---------- ---------- ---------- ---------- 10.959 --------- .. ------- --- ---------- ---------- 11,040 20.66 30 ---------- ---------- ---------- 258 2,813 ---------- ---------- 119 8, 544 ---------- 60 80 3, 739 ---------- 1.00 134 1,277 21,082 ----------

-- -------- ------- --- ------ ---- ---------- 91,718 l. 00 104 1, 837 5, 506 ----------

30 924 . --------- ---------- ---------- ---------- ---------- ---------- 54,560 .34 14 3,587 ----------

.22 241 948 ---------- ---------- 1.00 219 896 4,480 -- --------

.01 12 742 ---------- ---------- 368 4, 331 ---------- ---------- 22 97 ---------- ---------- .11 21 210 ---------- ---------- 15 5, 950 ----------

------- --- --- ------- ----- ---- - 1,108 16,681 LOO 148 5,907 ------------- ------- 1.00 182 ---------- ---------- ---------- 61 882 ---------- ---------- 1. 00 147 1,262 ---------- ---------- 149 1,138 ---------- ---------- 138 1, 273 4,412 ---------- 10.00 18 ---------- ---------- ---------- 12 18 1,105 ---------- 2.20 22 130 45 ---------- 1.40 414 910 22,424 ----------

---------- ---------- ---------- ---------- 90,650 19.60 8,743 15,875 .55,440 ----------

2. 00 

.20 

3.80 

----.--~io

1.60 

.20 

.30 

1.20 

8.10 

14.60 

1.65 

. 72 

6.04 

2.30 

5.80 

.50 

1.10 

1.00 

58.00 

. 70 20.41 

28.20 

5.87 

2.40 

.60 

.10 

18; 00 

.10 

6. 48 

·13. 63 

.50 

.90 

17.47 

21.76 

43.24 

1,209 13,413 ---------- 243,587 89 815 28,089 72,427 499,611 27 2,145 

9, 086 33, 584 250, 987 49 164 3,833 

2, 829 5, 219 42,917 32 148 6,029 

494 9, 829 ---------- ---------- 36 181 9, 870 ---------- 19 ---------- 3,417' -----·----- 500 13,327 ------ ---- ------ ---- 121 175 8, 627 ----------

3 ---------- ---------- ---------- 18 20 ---------- ---------- ---------- ---------- ---------- ---------- 45 106 4,568 ---------- 3 ---------- ---------- ---------- 2 ---------- ---------- ---------- 21 27 1,847 ---------- 3 ---·------ ---------- 38 70 5,398 408 805 5, 219 356 64 1, 361 32 248 1, 049 30 284 1,049 25 84 15,422 85 194 12,413 15 6 9 11 37 ---------- -----·----- 306 1,429 41,477 115 705 26,709 ---------- 12 194 1, 718 ---------- 2 5 1,007 -----·---- 11 398 18 ---------- 9 282 ---------- ---------- 6 1, 536 ---------- 12 13 9 ---------- 16 51 1, 735 ---------- 6 6 ---------- ---------- 12 42 ---------- ---------- 7 41 2,375 ---------- 1 13 73 ---------- 2 3 ---------- ---------- 12 74 21 25 36 104 248 2,811 2,801 16 156 2,498 

a Less than half a ton. 
Zon 

Iron 

Limonite (goehite) . H ema ~e . 

Jaro it . 1elan ri t 

Man an 

P rolu it . P ilomelan 

Wad. 

halcophanit 

Jlineral of th e or d po it 

rC' min raJ 

Zin L al opp r ilvcr 

1-----------1------- --------1 

/JJ 

-;a 

Mild temperat ur (lept o h rmal) .2 

100°-200° 

Pyrit . 

~ ------------------1---------------1 

·a Pyrite. 

P. rrhoti (?) . 

p cularit . 

Magn it . 

In ar ntif r u. gal na. In . .ili 011 or . 

1 hal ri ( zin 

blend hi h in Gal na. iron). 

-------------1--------

Gold 

Kat ive gold. 

::\ativ old. 

. -a t iv old (?). 

iJicate of lime, mag- n ia, iron, and man ane e 

Gangue mineral 

ilica 

pal(?). 

hale don '(?) . 

Quar z. 

Aluminum ili ates 

arbonat , ulphat , and fluorid 

alit.. 

Arag ni 

Thaum itc. 

--1---~=------- Montmorilloni e (?) . 

lad ui e. 

in 

• pidote. Garn t (andradit 

gro ularit ) . 

Hed nber it . 

Actinolit (?). 

Tremoli e (?) . 

Diop ide. \-\ oll onite. 

arl nat . 

Quar z. r -

ul a ri t ). 

of the We t ro. tat(' (Lindgr n \"Oium ) , pp. 1 l- 19i, Am. I n t. . 1in. ~! t. Eng., 1 33. 

20 - 4- Fa p. 
MINERALS OF THE MAGDALENA DISTRICT 87 

represent ore mined during prospecting and development. Most of the properties represented were reported active for only a few years, but some at least 

received assessment work throughout most of the 

period. It is noteworthy that little or no output has 

been reported from several claims that were active in 

the early 'SO's, and perhaps in the '90's as well. Some 

of these claims, for example, the Young America and 

Sampson, which later were taken over by th~ large 

companies, are known to have been worked on a small 

seale by lessees during the world-war period, but their 

outputs were evidently included in those of the controlling companies. 

During the lead period, 1882-1903, the price of lead 

ranged from 3 to 4.6 cents a pound, but fluctuations in 

price do not appear to have had much effect on the 

quantity of lead produced, which was evidently gov~ 

erned mainly by the availability of ore. The steady 

decline in the price of silver from 1891 to 1894 is not 

reflected in the quantity of lead produced, as the ore 

was prevailingly low in silver. 

The complete records of output, from 1904 to the 

present, began just as the oxidized zinc ores of the 

district were attaining full development. The output 

of these oxidized zinc ores attained its maximum just 

before the Nation-wide depression of 1907-8, during 

which the development and treatment of complex 

sulphide ores in the two principal mines became welladvanced. ':fhe prices of lead and zinc were fairly 

steady from .1904 to 1913, that of lead averaging about 

4.6 cents a pound · and that of zinc about 5.7 cents. 

Fluctuations in output during tliat period coincided 

with difficulties in milling, which, so far as can be inferred from the annual chapters in Mineral Resources 

of the United States, rendered the production rather 

unprofitable; but thereafter the annual output of ore, 

stimulated by World War prices, increased. to a maximum in 1917 (although the maximum value had been 

reached in 1916), and operations were profitable. By 

1918, however, an oversupply of zinc had accumulated 

in the United States, and a decrease in output followed, 

especially during the dull post-war year of 1919 and 

again in 1921, when very little zmc was produced 

throughout the country. The decrease in the Magdalena district is also accounted for by the practical 

exhaustion of the principal sulphide ore bodies in both 

the Kelly and Graphic-Waldo mines. Between 1921 

and the depression that began in 1929 the prices of 

zinc and lead averaged higher than in the pre-war 

period, and the Ozark mill was put in operation in 

1926 and 1927. The Graphic-Waldo mine was partly 

unwatered in 1928, but its discontinuance, together 

with the fact that any mill ore above water-level was 

not worked or develope,d in either the Graphic-Waldo 

or Linchburg mines suggests that current prices were 

not sufficiently encouraging to warrant activity. Since 

1927 the entire output of the district has been made 

by lessees. No ore was shipped from the district · in 

1931, but substantial outputs were made in 1933, 1934, 

and 1937, principally from the Kelly mine. As many 

ores in the undeveloped areas. referred to later as deserving attention are likely to be similar in grade and 

composition to those already produced and to involve 

similar problems of treatment, the foregoing review 

and the tabulated data may serve as a basis for judging 

market conditions that would favor a renewal of 

activity. 

MINERALS OF THE MAGDALENA DISTRICT 

By S. G. LAsKY and G. F. LoUGHLIN 

As an appreciation of the significance of minerals 

that constitute the ore deposits. of the district is essential to a consideration of the character, distribution, and 

origin of the ores, descriptions of these minerals are 

presented in considerable detail. Most of the minerals 

described were studied in the field and collected by 

Loughlin in 1916 and were studied in the laboratory by 

Lasky in 1929 and 1930. We are indebted to W. T. 

Schaller, of the Geological Survey, for the critical 

reading of these descriptions, for the investigation of 

the cadmium content of smithsonite, and for the descriptions of a few unusual minerals; also to Herman 

Wuestner, of Cincinnati, Ohio, who had made an 

extensive collection of minerals in the Magdalena district and supplied some of the unusual specimens 

studied by Schaller. 
88 MAGDALEN A MINING DISrr'RICT, NE"\V• MEXICO 

An alphabetical list of the ore and gangue minerals 

occurring in the district is given below. Original rockforming minerals and their .alteration products, are not 

included, even though they constitute gangue in some 

ores, as they are of no fundamental importance in the 

interpretation of ore-forming processes. 

The minerals in this list include those formed by 

ascending ore-forming solutions (hypogene minerals) 

and other minerals derived from them by the action of 

descending waters (supergene minerals). All minerals 

o:f the list are arranged in the accompanying table 

according to ' the principal metals they contain, and 

those of the hypogene group are subdivided according 

to the relative temperatures at which they were 

deposited. A few minerals, either because they were . . I 

deposited through a great range of temperature or 

A lphabeticalli stot mi nerals in the Magdalena district 

Name mjc l composition 

Actinolite 1__ __ _ _ _ _ _ _ (Mg,Fe)oCa2H2(Si03

) 8 _ _ _ _ _____ _ 

Allophane____ _ _ _ _ _ _ _ Al2SiOs.nH20 ___________ _____ _ _ 

Amphibole _____ ~__ _ Complex group of silicates of 

magnesium, iron, and calci- um, with other elements. See 

actinolite and tremolite. • Anglesite _ _ _ _ ___ _ _ _ _ PbS04------- ___________ _____ _ Andradite_______ ____ Ca3Fe2(Si04)3 ___ .:. _____________ _ Andalusite _ _ _ _ _ _ _ _ _ _ Al2Si 0 5 __ _ ___ _________________ _ 

Antigorite____ __ ___ __ H4Mg3Si209 _____________ · _____ _ Antlerite z__ __ _ _ _ _ _ _ _ CuS04.2Cu(OH)z _______ __ ____ _ Aragonite_________ _ _ CaC03 ___________________ ___ _ Argentite___ __ ______ AgzS ___________________ -~ ___ _ 

Aurichalcite__ _ __ __ __ 2(Zn,Cu)C03.3(Zn,Cu) (OH)z __ _: 

Azurite__ _________ __ 2CuCOa.Cu(OH)z ____________ _ _ 

Barite _____ _______ _ _ BaS04- __________________ ____ _ 

Beidellite(?) 2 _ __ _ _ _ _ _ (Al,Fe"'h Si30 9.nH20 _________ _ Bornite 1_ _ _ _ _ _ _ _ _ _ _ _ Cu5

FeS4- ____________________ _ 

Calamine ___________ See hemimorphite ____ ____ ____ _ Calcite _____________ CaC03- _____________________ _ 

Celadonite_ _ _ _ _ _ _ _ _ _ Hydrous silicate of aluminum, 

iron, magnesium, and potassium. 

Cerussite____ ________ PbC03 ___________ ____ __ __ ___ _ Cerargyrite_ _ _ _ _ _ _ _ _ _ AgCL ______________________ _ 

Chalcanthite _ _ _ _ _ _ _ _ CuS04.5H20 _____________ .:_ ___ _ Clialcedony 3 _ _ _ _ _ _ _ _ Si02------ ___________________ _ Chalcocite _ _ _ _ _ _ _ _ _ _ Cu2S- _______________________ _ 

Chalcophanite 3 __ ____ (Mn,Zn)0.2Mn02.2H20 ________ _ Chalcopyrite_ _______ CuFeS2 __ _ _____________ _ _ __ __ _ 

Chlorite __ __ ________ Complex group of hydrous silicates of iron, magnesium, and 

aluminum. 

Chrysocolla _ _ _ _ _ _ _ _ _ CuSi 0 3. nH20 ___________ ______ _ 

Copper (native) ____ __ Cu __ ________________________ _ Covellite___ _ _ _ _ _ _ _ _ _ CuS ____ ________________ ____ _ Cuprite 3 __ _ _ _ _ _ _ _ _ _ _ Cu2

0 _______________ _____ ____ _ 

Cyanotrichite 2 _ _ _ _ _ _ Cu4A 12S010.8H20 _____________ _ 

Diopside___ _ _ _ _ _ _ _ _ _ Ca(Mg,Fe) (Si03

) 2 ____________ _ 

Dolomite__ _________ CaMg(C03h - _______ __ _______ _ 

Epidote __ __________ HCa2(Al,Fe)aSi301a-- _______ ___ _ 

Fluorite_ ________ ___ CaF2 _ _______________________ _ 

Galena_ _ _ _ _ _ _ _ _ _ _ _ _ PbS ___________________ ___ __ _ 

Garnet_ _ _ _ _ _ _ _ _ _ _ _ _ See andradite and grossularite __ Gold (native) __ _____ Au __ ____ _______ ____ ____ _____ _ 

Goslarite___ ____ _ __ __ ZnS04.7H20 __ ____________ ___ _ GreenockUe _________ CdS __________________ __ ____ _ 

Grossularite_____ __ _ _ Ca3Al2 (Si04) 3 _______ ___ _____ _ _ 

Halloysite _ _ _ _ _ _ _ _ _ _ Alz03.2Si02.nH20 __ ___________ _ Hedenbergite__ __ _ _ _ _ Ca(Fe,Mg) (Si03)z __ ___ ______ _ _ 

Page on which 

detailed 

description is to be found 

Name_ Chemical composition 

100 Hematite ________ ___ Fez03- _____ __ __ ____ __ _______ _ 

103 Hemimorphite___ _ _ _ _ (ZnOH) 2Si03--- __ ___ ___ ___ ___ _ 100 Hydrozincite _ _ _ _ _ _ _ _ 2ZnC03.3Zn(OH)z _______ ___ __ _ 

Jarosite____ ___ ____ __ KzFe6(0H)t2(S04)4- ________ ___ ~ 

97 Kaolinite ___ __ ______ H4Al2Si2 0 9 __ ___ __ ___ _______ __ _ 

100 

9 9 Limonite __ _ _ _ _ _ _ _ _ _ Fe20a, with varying amounts of 

101 water. 

96 

103 Magnetite___ ___ ____ Fe304- _____ _____ ___ _ .:. _______ _ 98 Malachite_ __ __ ___ __ _ CuC03. Cu(OH)z ____ __ _______ _ 93 Melanterite _ _ _ _ _ _ _ _ _ FeS04. 7Hz0 ___ ____ __ ___ ______ _ 

96 Montmorillonite(?) __ (Alz0a,Mg0).2(Si02).H20 __ __ ___ _ 

103 

103 

95 

94 

102 

104 

97 

98 

96 

101 

95 

93 

94 

102 

96 

96 

95 

96 

96 

99 

102 

100 

103 

. 97 

100 

99 

94 

99 

100 

103- 100 

OpaL_ ___ __________ Si02.nHzO __ _______ __________ _ 

Psilomelane_ _ _ _ _ _ _ _ _ MnOz.nHzO __ __ _____ _________ _ 

Pyrite ___ ____ _____ __ FeS2------ - --------- - - ------- Pyrolusite _ _ _ _ _ _ _ _ _ _ MnOz _____ ___ ___ ___ __ _______ _ 

_Pyroxene__ ______ __ _ Complex group of silicates of 

magnesium, iron, calcium, and 

other elements. See diopside 

and hedenbergite. Pyrrhotite (?) 4____ _ _ _ FenSnt - - - _ -- ___ -- __ _____ __ - - - Plumbojarosite_ _ _ _ _ _ PbFe6(0H) !2(S04)4--- ___ __ __ __ _ 

Quartz _ _ _ _ _ _ _ _ _ _ _ _ _ Si 0 2 

_ __ _ ___ _ _____ _ ______ __ _ _ _ 

Sericite ____________ _ Serpentine __ _______ _ 

Siderite (manganoan)_ Silver _______ __ ___ _ _ 

Smithsonite ________ _ 

Smithsonite, ferroan __ Spangolite 2 __ _ _ ____ _ 

Sphalerite __ _______ _ _ 

Sphalerite, ferroan __ _ 

Specularite (hematite). 

"Tallow clay" ______ _ Tenorite 1 __ _ ____ _ __ _ 

Thaumasite ________ _ Tourmaline ______ __ _ 

Tremolite s ___ ___ ___ _ 

(H, K)A1Si04 ___ ____ __ _ ___ __ _ _ 

H4MgaSi209_----- ---- --------- (Fe, Mn) COa-- _----- --------- Ag _______________ _____ ______ _ 

Zn CO a __ ___ ________ ____ ____ _ _ 

(Zn, Fe)COa- ____ - ------ ------ Cu6AlClSOto.9H20- _____ ____ - _- ZnS ___ ___ ___ __ _______ ______ _ _ 

(Zn, Fe)S ___ ____ _____ -~ ______ _ 

Fe20a----- --------- - --- -- - - --

Zinc-copper clay ___ __ ___ ____ __ _ CuQ __ _____ ____ ___ ___ __ _____ _ 

CaS04.CaCOa.CaSiOa.15H20 ___ _ Complex group of hydrous borosilicates of aluminum, magnesium, iron, and alkalies. 

MgsCazH2(~iOa)s ---- -- ----

Vanadinite__ _ _ __ _ __ _ (PbCl)Pb4(V04)a ____ _____ ____ _ 

Wad __________ _____ Mixture of oxides, chiefly of 

manganese. Willemite_ _ _ _ _ _ _ _ _ _ _ ZnzSi04- __ ___ ______ _________ _ 

Wollastonite____ ____ CaSi03 ___ ___ _ ________ _ __ _ __ _ _ 

1 Report~d in Wuestner, Herman, A check list of minerals from Kelly, N.Mex. Rocks and Minerals, vol. 5, pp. 127-130,1930. 2 Determmed by W. T. Schaller, U.S. Geological Survey, 1937. 3 Reported by C. H. Gordon in U. S. Geol. Survey Prof. Paper 68, p. 253, 1910, and by Wuestner, Herman, op. cit., pp. 127-130. : Reported by Philip Argall, M in. nd Sci. Press, vol. 112, pp. 129-130, 1916. Reported by C. H. Gordon, op. Cit., p. 253. · 

Page on which 

detailed 

description is to be found 

90 

94 

93 

92 

10;3 

91 

90 

96 

92 

103 

101 

91) 

91 

99 

91 -

97 

101 

102 

101 

102 

98 

92 

92 

96 

92 

92 

90 

94 

96 

102 

99 

100 

98 

99 

94 

99 
MINERALS OF THE MAGDAL.EN A DISTRICT 89 

b~cause they contain more than one metal, are repre- 1 

sented in more than one place. 

The subdivisions are based on relative temperatures. 

they follow Lindgren's classification, which was first 

proposed in 1907 21 and was supplemented by Graton 

in 1933.22 Neither this nor any other arrangement is 

perfectly consistent, as some minerals, notably pyrite, 

quartz, calcite, sericite, and epidote, may form throughout a great range of temperature and may depend on 

the compositions of reacting solutions and rocks -rather 

than on temperature; but the arrangement adopted 

emphasizes the characteristic positions of the minerals 

in the deposits of the district and therefore their 

significance in the interpretation of the deposits and 

in the pr ctical problem of ore hunting. Very few 

definite experimental data are available regarding the 

temperatures at which the different minerals can form 

under anything like natural conditions, and the grouping of the minerals is therefore largely relative. Of 

the mi~erals formed by replacement of limestone, wollastonite can be formed in the laboratory between 

temperatures of 400° 23 and 1,500°,24 and its occurrence 

at Magdalena is such as1 to suggest that it formed near 

the lower end of this range. The magnetic specularite 

may indicate a temperature between 300° and 500° C. 

(See p. 90.) Data on the other silicate minerals listed 

in the high-temperature group are not so definite, 

but field relations show that most or all of them were 

formed at lower temperatures than wollastonite, though 

still during the earliest stage of mineral deposition. 

Specularite and magnetite. are closely associated · with 

these . silicates but . were deposited -later and evidently 

at still lower temperatures. 

The sulphide minerals, particularly pyrite, are also 

closely associated with silicate minerals and especia1ly 

with the iron oxides specularite and magnetite, but in 

view of experimental and microsccpic evidence it is 

. most likely that pyrite began to .form as the iron 

oxides ceased to form. Thi~ change may conveniently 

be regarded as marking the boundary between the 

high-temperature and moderate-temperature minerals 

in the Magdalena deposits formed by the replacement 

of limestone, though the boundary is not sharply defined. (See p. 91.) Under different conditions pyrite 

may form at higher temperatures. Sphalerite with a 

high co!ltent of iron followed the main deposition of 

21 Lindgren, Waldemar, The relations of ore deposition to physical 

conditions : Econ. Geology, vol. 2, pp. 105-127, 1907; A suggestion for 

the terminology of certain · mineral deposits: op. ca., vol. 17, pp. 2!)2--

294, 1922. 

22 Graton, L. C., The d(:'pth zo1ies in ore deposition : Rcon. Geology, 

vol. 28, pp. 513- 555, 1933 ; '.rhe hydrothermal depth zones : Ore dPposits 

of the Western States (Lindgl"en volume), pp. 181- 197, Am. In st .. Min. 

Met. Eng., 1933. 2': Allen, E. T., and White, W. P., On wollastonite and pl';f'uflo-y·ollastonite-polymorphic forms of calcium metasilicate: Am. Jour. Sci., 4th 

ser., vol. 21, p. 89, 1906. · 

24 Bowen, N. L., Schairer, J. F., and Posnjak, Eugene, The system, 

Ca0-Fe0-Si02 : Am. Jour. Sci., 5th ser., vol. 26, p. 207, 1933. 

200889-42--7 

pyrite, and galena and ch~lcopyrite followed the main 

deposition of sphalerite. As all these minerals were 

formed for the most part by the . replacement of limestone, any un:replaced remnants of limestone beside or 

within masses of the high-temperature minerals were 

subject to replacement later by m~derate-temperature 

minerals, resulting in a confusing association of minerals at some places. 

On the basis of mineral association and proximity 

· to exposed igneous stocks, there might be some justification for classifying the sulphides as high-temperature minerals. On the whole, however, the sulphide 

minerals, which crystallized distinctly later than the 

silicates and, the iron o:xides, extend farther from the 

stocks and farther from the main fissures along which 

mineralizing solutions were introduced. They are 

therefore consistently assigned to the moderate-temper-

. ature class. 

Barite and fluorite are abundant only in places well 

removed from the centers of mineralization, and are 

therefore the n1ost characteristic minerals ot the out--

lying deposits, which were necessarily formed at rela'" 

tively mild temperatures. The sphalerite associated 

with conspicuous amounts of barite is commonly lower 

in iron than that near the high-temperature centers, 

but no comparative analyses bearing on this difference 

have been made. 

Calcite represents a wide range in temperature. Its 

long pointed crystals or scalenohedrons represent a 

stage later than the barite and fluorite, but other forms . 

Tepresent hotter or earlier-stages. , A conspicuous fea-

·ture of some of the mixed oxide-sulphide ores is the 

presence of radiating aggregates of platy calcite crystals that may be :rn.istaken underground for tr~molite 

or some similar silicate. These crystals have in part 

replaced silicates and in turn have been ~eplaced by 

specularite and sulphides, or they may represent limestone that recrystallized during impregnation by spec~­

larite ; but either ' suggestion irr{plies formation at a 

temperature above that at which the iron-rich sphalerite 

formed. 

Quartz also represents a wide range in temperature, · 

as it is associated with characteristic mine~als of most ' 

of the different groups; however, it is inost abundant 

in the outlying parts· of the district, esp~cially the 

southern part, where it forms the immense masses of 

fine-grained to dense jasperoid that have replaced _ · 

limestone. These masses in tunLare cut by veins con- · 

t3ining barite, quartz, and sulphides and evidently 

represent an outlying, milder temperature facies of 

the early stage of mineral deposition. In othe_1:· words, 

the early . siliceous solutions from_ a deep source in the 

southern part of the district became cooled below the 

.silicate-forming range while rising, through the sili-
90 MAGDALEN A MINING DISfrRICT, NEW MEXICO 

ceous pre-Cambrian rocks and on reaching the overlying Kelly limestone were only able to replace it 

with silica. 

Of the minerals that have replaced siliceous rocks, 

the only mineral commonly regarded as indica~ive only 

of high temperature is tourmaline, which is confined to 

pegmatite stringers in Tertiary ( ~ ) granite and to 

minor cracks in aplite, monzonite, felsite, and argillite 

near the Tertiary (?) granite stock east of Hardscrabble Camp (see pp. 41, 49). Its relation to other ore 

or gangue minerals is too obscure to warrant further 

comment here. The most characteristic gangue minerals in the siliceous rocks are quartz, sericite, epidote, 

chlorite, and calcite. The epidote with quartz, feldspar, and -calcite is present in a few veinlets in monzonite near contacts with high-temperature silicate 

deposits in limestone and evidently indicates deposition 

at a relatively high temperature; but sericite, quartz, 

epidote, and chlorite are closely associated with 

sulphides in partly replaced monzonite, granite, and 

volcanic rock and evidently represent deposition at a 

moderate temperature for the most part. 

IRON MINERALS 

SULPHIDE ZONE 

SPECULARITE AND MAGNETITE 

Of the two high-temperature iron oxides, specularite 

and magnetite, specularite is by far the more widely 

distributed. It forms bladelike crystals in radiating 

sheaves and interlacing mats. Single blades average 

about 1 millimeter in length, and few exceed 2 millimeters. Practically all the specularite seems to be 

magnetic. Most of it contains admixed magnetite, but 

some that appears free from magnetite even at a magnification of 385 diameters is also magnetic. 

This magnetism may be due to submicroscopic 

particles of magnetite, or it may be a property of the 

w. 

3 

10 5 0 10 20 30 40 so Feet 

specularite itself; for recent experiments 25 show tpa.t 

Fe20a oxidized from Fea04 is magnetic between temperatures of 300° and 500° C. If such magnetic Fe20a 

(magnetic specularite) is formed in nature 26 and if the 

magnetism is retained as the mineral cools down 

through geologic time, magnetic specularite would 

constitute a good geologic thermometer. 

Magnetite commonly forms irregular grains and 

aggregates interstitial to the specularite blades or coating them. (See pl. 23, A.) It also forms minute 

grains within specularite (see pl. 23, B) that locally 

are predominant .and ·even form complete pseudomorphs after specularite. (See pl. 23, 0.) In some 

places the magnetite forms octahedra as much as 0.5 

millimeter in diameter, and in a few places it is cut 

by veinlets of crystalline though non bladed hematite. 

These different relations imply slight oscillations in the 

physical conditions that controlled the deposition of 

the two minerals. 

The specularite-magnetite aggregates form masses 

several feet in diameter along the main ore zone in the 

northern part of the Graphic-Waldo mine rather near 

the Nitt 1nonzonite stock, but small masses or layers 

in sulphide and partly oxidized ores have been seen in 

the southern part of that mine and in the Kelly mine 

as far south as the Big Twenty stope, 3,300 feet from 

the stock. A typical occurrence in sulphide ore is 

shown in figure 9. Specularite and magnetite in nearly 

equal proportions are also present in the ore of the 

Hardscrabble mine 2,200 feet north of the Nitt monzonite but close by the Tertiary ( ~) granite stock. 

The magnetite there forms distinct octahedra as much 

as 0.5 millimeter in diameter. 

l!5 Gotoh, Yuuichi, On the reduction of ferric oxide by hydrogen and 

oxidation of metallic iron reduced from ferric oxide : Inouye commemoration volume, Ryojun College Eng. Mem., pp. 393-413, 1934. 

20 Winchell, A. N., Maghemite or oxymagnite: Am. Mineralogist, vol. 

16, pp. 270-271, 1931. 

E. 

Lead-zinc sulphides 

Magnetite, 

specula rite, 

' and pla!:J' calcite 

EJ 

Replacement quartz 

FIGURE 9.-Generalized section through 

top of raise 'No. 1, level 7, GraphicWaldo mine, 1,100 feet south of NHt 

monzonite stock, showing relation of 

specularite-magnetite aggregates to 

sulphide ore and gangue. Looking 

south. (1) 7 feet of lead-zinc sulphides 

accompanied by magnetite and specularite. The iron oxides tend to form 

layers in the zinc f'lnlphide. (2) 7 feet 

of limestone, partly bleached and recrystallized to siderite ( ?). (3) 21 feet 

of zinc lead sulphide ore, which passes 

into platy calcite, specularite, and magnetite on the hanging-wall side. This 

aggregate is followed successively by 

a thin layer of replacement quartz and 

crystalline limestone. 

\ 
~-

MINERALS OF THEI MAGDALENA DISTRICT 91 

~1agnetite and probably specularite were :found as-· 

·sociated with serpentine and chlorite on the dumps o:f 

pits southeast o:f Granite Mountain. No intrusive 

contacts are exposed nearby, but the Tertiary ( ~) 

granite stock is probably present underneath the 

alluvium a short distance to the south. 

The specularite-magnetite aggregates are everywhere accompanied by pyrite and in most places by 

ferroan sphalerite (marmatite). The sulphides commonly contain inclusions o:f the oxides, which they 

have corroded or replaced to some degree. (See pl. 

23, D.) . Some small crystals o:f specularite (pl. 24, A) 

appear to have been completely replaced by pseudomorphs o:f pyrite. In some partly leached ore galena 

is the only sulphide now associated with the two oxides, 

but the large amount of limonite also present implies 

the former presence o:f pyrite and doubtless sphalerite. 

PYRITE 

Pyrite occurs in sulphide deposits throughout the district and for the most part is the earliest . of the 

sulphides, as shown by inclusions o:f pyrite in the other 

sulphides; but small amounts of fine-grained pyrite 

with quartz or calcite form veinlets that cut the other 

sulphides in places. Pyrite is also commonly present 

in altered country rock. It :forms large coarsely 

crystalline masses that have replaced Kelly limestone 

in the Nitt mine, and . it is the dominant sulphide in 

the "copper shoot" along the eastern part o:f the main 

ore zone in the Nitt and Graphic-Waldo mines, where 

it is accompanied by interstitial chalcopyrite. It also 

:forms lenses and layers in specularite-magnetite 

masses. It tends to :form well-shaped crystals up to 

three-quarters o:f an inch in diameter, both in pyritic 

and mixed sulphide masses. The common crystal 

:forms are combinations of the cube and pyritohedron. 

Some grains are microscopic intergrowths of isotrop~c 

and weakly anisotropic pynte. 

The relations o:f pyrite to specularite and magnetite 

show that on the whole the pyrite was :formed later, 

although there was evidently a little oscillation o:f conditions during the change from the early oxide to the 

later sulphide stage. Plate 24, 0, shows pyrite interfingering with blades o:f specularite and partly replacing them. Such interfingering pyrite locally passes 

into pyrite crystals that are partly surrounded with 

gangue and so have been able to grow in part without 

interference from the older specularite. Pyrite, with 

well-defined crystal boundaries where in contact with 

gangue but with irregular boundaries where in contact 

with specularite, is shown on plate 24, D. Much of the 

pyrite contains inclusions o:f slightly corroded iron 

oxides~ and minute pyrite rods, apparently pseudomorphs after specularite (pl. 24, B), have bee:h noted 

that merge into pyrite crystals with inclusions o:f 

specularite. 

Alt4ough the foregoing relations show that pyrite 

on the whole was deposited later than the iron oxides, 

there . are minor exceptions. Coarse-grained cubic 

crystals o:f pyrite from level 10 o:f the Graphic-Waldo 

mine contain minute inclusions of specularite in zonal 

arrangement, as shown on plate 25, A, which hardly 

seems attributable· to the simple engulfment illustrated 

above. Such an arrangement implies either a brief 

interruption to the growth of pyrite and an· intervening growth of specularite or, less likely, an impregnation of pyrite by specularite along one or more 

especially susceptible zones. Either suggestion implies 

a slight reversal of the general change in conditions 

of normal mineral deposition and practically no appreciable interval o:f time between the specularitemagnetite and the pyrite stages. 

The most conspicuous pyritic 'impregnation of 

country rock is ·in the altered monzonite along the 

upper part of Hardscrabble Valley, where the rock, 

though in too small quantity to be of commercial interest, has the general character of disseminated pyritic 

copper ore. Disseminated pyrite grains or limonite 

pseudomorphs after theJ;Il are conspicuous in some 

white rhyolite dikes in the Tertiary ( ~) granite. 

PYRRHOTITE 

Pyrrhotite was incidentally mentioned by Philip 

Argall as a constituent o:f the ores o:f the G-raphicWaldo mine. 27 None was :found· by us. · 

OXIDIZED ZONE 

LIMONITE 

Limonite, . here used as a field name :for fine-grained 

aggregates of ferric oxide that ;contain varying 

amounts of water,28 :forms a large part of the oxidized 

ores. It has resulted chiefly from the oxidation o:f 

pyrite . and ferroan sphalerite. Small quant,ities maJ 

have been derived from siderite, manganosiderite, 

• 1nanganiferous calcite, and jarosite, all ~ut the last of 

which are described under gangue minerals~ It is 

commonly yellow , brown or reddish and earthy. In 

some places it is mixed with manganese oxides and 

grades into wad. The shiny, brown-black, fibrous variety is· :found in a few places, and boxwork varieties 

that represent incomplete replacement of sulphide ore 

or limestone have been found in several mines. Pseudomorphs of limonite after pyrite are conspicuous in 

some o:f the white rhyolite dikes. 

27 Rickard, T. A., Philip Argall and metallurgical progress : Min. and 

Sci. Press., vol. 112, pp. 129-130, 1916. 28 Posnjak, Eugen, and Merwin, H. K, The hydrated ferric oxides: 

Am. Jour. Sci., 4th ser., vol. 47, pp. 311-348, 1919. 
92 MAGDALENA MINING DISffRICT, NEW MEXICO 

,JAROSITE OR N A TROJ AROSITE 

Jarosite, a hydrous sulphate of ferric i~on and 

potash, or its soda equivalent, natrojarosite, has been 

noted at several places throughout the district in the 

upper part of the oxidized zone. It is conspicuous 

in the outcrop at the south side of the main glory hole 

of the Hardscrabble mine, in the Tabaschi tunnel of 

the Graphic-Waldo mine, and in the outcrop of the 

Black Cloud ore body. It is also conspicuous at the 

Papa prospect (Queen group) in the 'Vater Canyon 

district just south of the Magdalena district. 29 At the 

Hardscrabble mine and the Papa prospect it was found 

associated with plumbojarosite. It is soft, earthy, and 

ocherous yellow to yellowish brown; and in its darker 

shades resembles light-colored l'imonite. Only at the 

Papa prospect was jarosite visibly crystalline. No 

analyses of the mineral from any of these places have 

been made, and it is therefore not known whether the I 

mineral is jarosite or natrojarosite. Perhaps both are 

present. 

MELANTERITE 

Wuestner 30 reports that melanterite occurs locally 

with goslarite and chalcanthite incrustations on the 

walls of mine workings, apparently where the rate of 

evaporation of sulphate waters has exceeded the rate 

of oxidation of the contained iron. 

ZINC MINERALS 

SULPHIDE ZONE 

S~HALERITE (ZINC BLENDE) 

Sphalerite, or zinc blend~, is the most abundant sulphide in the Magdalena ores with the possible exception of pyrite. It ~orms irregular grains in the dominant mixed sulphide ores and also ocqurs as massive 

. aggregates of high-grade zinc ore in ,which only small 

amounts of pyrite and galena are present. Some of 

these high-grade masses are near the contact of the 

Nitt monzonite stock, where specularite-magnetite and 

pyritic masses dominate, and others are considerable 

distances from it. Although most of the sulphide ores 

have been of sufficiently coarse .grain to permit separation into zinc and other concentrates, some, for example on level 6 of the Graphic-Waldo mine, have 

been such fine-grained mixtures of sphalerite and galena 

that they have been utilized only by oxide plants tor 

the n1anufacture of zinc-lead pigments. In the Germany mine some sphalerite forms botryoidal crusts, and 

smne polished specimens of ore from the same mine 

show sphalerite crystals surrounded with galena. 

Nearly all the sphalerite mined has been dark brown 

to black and has contained considerable iron, though 

no chemical analyses of it are available;... but in mar28 Lasky, S. G., The ore deposits of Socorro County, N. Me~.: New 

1\Iexico State Bur. Mines Bull. _8, p. 54, 1932. 30 Wnestner, Herman, op. cit., p. 130. 

ginal parts of the main ore shoot in the Kelly mine a 

lighter-brown or resinous variety has been found, and 

in the outer parts of the district some of it is clear 

yellow and comparatively low in iron. The sphalerite 

examined microscopically contains minute inclusions of 

chalcopyriate (see ;p. 95) . 

OXIDIZED ZONE 

SM:ITHSONITE 

Smithsonite, the principal constituent of the oxidized 

zinc ores, occurs in a variety of forms and colors. 

The most common variety is gray to buff and finegrained to dense (pl. 25, 0) and has replaced the 

"silver pipe" and other limestone beds. It is so easily 

mistaken for limestone that much of it was thrown 

over the dump during the early or lead carbonate stage 

of the district's history. This variety contains considerable iron, sufficient for the smithsonite, in part 

at least, to be classed as the monheimite variety. It 

turnf) brown on oxidation, and may be partly coated 

with black dendritic stains of manganese oxide. Another common variety (pl. 25, B) is the cellular to 

layered smithsonite or "dry bone." Some is intermediate in texture between the compact and cellular 

varieties and is pink to reddish brown. The larger 

round to irregular cavities in cellular smithsonite 

doubtless represent dissolved remnants of unreplaced 

limestone, but the parallel openings in layered smithsonite, which so far as seen has replaced limestone 

along the walls of fissures and bedding pla~es, are 

original features and are believed to result from rhythmic replacement and to represent the large amount of 

shrinkage due to a simple reaction between zinc sulphate solution and the calcium carbonate of limestone. 

A more striking variety than the others (pl. 26, A) is 

the stalactitic, botryoidal, or crustified smithsmiitR 

whose color is commonly bluish green and less commonly brown, purple, yellow, and white. One or more 

of these colors may be present in a single specimen. 

The chemical analysis of the green smithsonite quoted 

below 31 shows the presence of considerable copper. 

Chemical analysis of green smithsonite from 

Magdalena, N. Mex. 

ZnO ___________________ 60. 97 

CuO~------------- ---- 3. 48 

CdO_____________ ______ . 16 

FeO, PbO, MnO ___ ___ Traces 

cao___________________ 0. 44 

002--------------------- 35. 12 

100.17 

Two specimens of yellow smithsonite, ·designated A 

and B, from the Kelly mine were analyzed by W. T. 

Schaller, J. G. Fairchild, and George Steiger, of the 

U.S. Geological Survey, to determine the quantity and 

distribution of any cadmium present, and Schaller has 

contributed the remaining paragraphs on smithsonite. 

81 Argall, Philip B., The ore deposits of Magdalena, N. Mex. : Eng. 

and Min. Jour., vol. 86, p. 369, 1908. 
MINERALS OF THE' MAGDALENA DISTRICT 93 

A polished surface, specimen B (pl. 26, B) shows that the 

variously colored smithsonite forms regular concentric layers, 

each from 2 to 5 millimeters wide, surrounding a central 

cellular mixture composed mainly of brown iron oxide with 

green malachite and . white smithsonite. From the center 'outward the layers are brownish amesthystine (analysis 5) , milky 

white (analysis 4), yellow (analysis 3), and finally white with 

several thin brown band,s of iron oxide. 

Parts of both specimens A and B were crushed and the 

fragments hand-sorted, those of specimen A into (1) yellow 

and (2) milky white fractions and those of specimen B into (3) 

yellow, (4) milky white, and (5) brownish amethystine. 

Amethystine smithsonite is also present in specimen A, but it 

was not separated. The fractions were partially analyzed with 

the following results : 

Partial chemical analyses of hand-sorted fractions of smithsonite from banded specimens, Kelly mine, Magdalena mining 

district, Socorro County, N.Mex. 

A B 

~------ ----------~-----

Yellow 

2 

Milky 

white Yellow Milky 

white 

5 

Brownish 

amethys- tine 

---------------------------------- -~---

Cadmium (Cd)t __ ___ _____ _____ 0. 57 0.39 0. 56 0. 43 0.40 

Manganese oxide (Mn0)2 _____ . 34 . 58 . 34 . 56 .57 Ferrous oxide (Fe0)3 ______ ____ 1.56 (4) 1. 31 1. 03 1.46 

Lead oxide (PbO).I_ --------- Trace (4) Trace .33 (4) 

Insoluble in hydrochloric acid3 _ .02 . 01 . 01 .01 .04 

'No.1, average of 0.56 (Fairchild) and 0.58 (Schaller); No.2, determined by W. 'r. 

Schaller; No.3, average of 0 .. 58 (Fairchild) and 0.58 and 0.51 (Schaller); No.4, average of 0.45 (Fai~child) and 0.45 and 0.39 (Schaller); No.5, determined by W. T. Schaller. 2 Determmed by George Steiger. 3 Determined by W. T. Schaller. 4 Present but not determined. 6 Determined by J. G. Fairchild. 

Qualitative tests for sulphide, as H2S, evolved by treatment 

with hydrochloric acid and testing with moist lead acetate paper, 

which turns black if H2S is present, indicated sulphide as follows: (1) Yellow, strong; (2:) Milky white, weak; (3) Yellow, 

strong; ( 4) Milky white, trace; (5) Brownish amethystine, trace. 

As 1 and 3 are yellow smithsonite and give· a strong test for 

H2S, it seems that cadmium is present as sulphide. But as 

samples 2, 4, and 5, which are not yellow and which give only 

a faint to weak test for H2S, nev~rtheless contain, on an average, 

72 percent of the total cadmium content of the yellow smithsonHe, it would seem that most of the cadmium in these differently 

colored varieties of smithsonite is present as cadmium carbonate 

and that only a minor quantity is present in the yellow smitp.-

sonite as sulphide. 

cadmium may be more generally present in smithsonite than 

has commonly been realized. Apparently only a few tenths 

of a percent of yellow cadmium sulphide is sufficient to color 

smithsonite yellow. 

Spectrographic tests for Ag, As, Be, Bi, Ga, Ge, Zn, Re, Sb, 

Sn, and Tl, made by George Steiger, gave no evidence of their 

presence in any of the five samples tested. 

HYDROZINCITE 

Hydrozincite, a basic zinc _carbonate, typically occurs 

as thin white chalky . or earthy layers between th~cker 

layers of fibrous. botryoidal or crustiform smithsonite 

(pl. 26, A) and is probably present in some of the 

whiter varieties of massive smithsonite. Some hydrozincite is very pale green as if impregnated with small 

amounts of green copper carbonate or with aurichalcite. 

The association of the hydrozincite with botryoi~al 

smithsonite implies alternating changes 1n the 

composition of descending waters. 

AURICHALCITE 

Aurichalcite, a basic zinc-copper carbonate, corresponds chemically to hydrozincit.e with part o£ the 

zinc replaced by copper. The pure mineral, according to Penfield,33 contains from 53 to 54.4 percent of 

zinc and 20 to 21.2 percent of copper, but different 

chemical analyses show from 50 to 59 percent of zinc 

and from 15 to 22 percent of copper. 34 The zinccopper ratio ranges from 2 : 1 to 1 : 2, according to 

Biehl.35 

It occurs in minor quantities throughout the district 

but is ·nowhere of economic importance. It is pale 

green to blue green and is silky and fibrous or scaly. 

. It forms layers in crustiform and botryoidal smithsonite (pl. 26, A), coats drusy cavities, and forms little 

spherulitic tufts on smithsonite and associated minerals. Keyes 36 describes an occurrence from the old 

Graphic workings in which the aurichalcite is 

enveloped in crystals of calcite, which are thus colored 

a beautiful green. 

CHALCOPHANITE 

Chalcophanite, like aurichalcite, 1s widespread in 

very small quantities.37 It occurs 1n steel-blue 

aggregates 38 and crusts of radiate structure 39 \ on 

smithsonite. One brown-black botryoidal crust on 

That cadmium is present in two forms in yellow smithsonite 

is also suggested by the analysis of a bright yellow variety 

from Marion County, Ark., for H. N. Stokes reports 32 in his 

analysis 0.63 percent of CdO and 0.25 percent of CdS, confirming the conclusion, reached as a result of the determinations on 

the smithsonites from the Kelly mine, that most of the cadmium 33 Penfield, S. L., On the chemical composition of aurichalcite : Am. 

• 11 'th 't · th b Jour. Sci., 3d ser., vol. 41, pp. 106, 108, 1891. m ye ow sm1 som e IS present as e car onate. It also follows 34 Emmons, s. F., Irving, J. D., and Loughlin, G. F., Geology and ore 

that the lack of a yellow color in any smithsquite is no indica-. deposits of the Leadville mining district, Colo. : U. s. Geol. Survey Prof. 

t"ion of the absence of cadmium. rrhe yellow layer contains a Paper, H8; p. 157, 1927. 

ruuximum of cadmium and ·a minimum of manganese and lead, _ . 35 Bieh.l, F. K., Mineral abstracts 1, p. 203, 1921. Cited py Winchell, 

N. H., and Winchell, A. N., Elements of optical mineralogy, pt. 2 (dewhereas the white smithsonite contains less cadmium but more scription of minerals), p. 85, John Wiley & Sons, Inc., 1927. 

manganese and lead. The content of iron shows no regular 36 Keyes, c. R., Remarkable occurrence of aurichalcite: Iowa Acad. 

Yariation. Sci. Proc., vol. 11, p. 253, 1904. 

The quantities of cadmium in the milky white and brownish · 37 Brinsmade, R. B., Kelly, N. Mex., a zinc camp whose ores have 

been made available by modern metallurgical methods: Mines and Minamethystine varietif's are unexpectedly high and are evidently erals, vol. 27, pp. 51_53, 1906. 

present in the form of white carbonate·. They suggest that as Lindgren, Waldemar, Graton,. L. C., and . Gordon, C. H. Ore deposit_s 

33 Dana, E. S., System of mineralogy, 6th ed.; p. 279; 1892. , 

of Ne~ Mexico: U. S. Geol. Survey Prof. Paper 68, p. 253, 1910. 39 Wuestner, f{erman, .op; cit., p. 128. 
94 MAGDALENA MINING DISTRICT, NEW MEXICO 

smithsonite resembled chalcophanite but was found to 

contain not only zinc but also considerable copper. 

HEMIMORPHITE (CALAMINE) 

Hemimorphite (H2Zn2 Si05 ), the hydrous zinc silicate, occurs typically as aggregates of elongated crystals, hardly more than 2 or 3 millimeters long, in 

drusy cavities in smithsonite and locally with associated limonite and clayey material. It is in places 

coated with colorless flat calcite rhombs, notably in the 

Ida Hill tunnel, where it occurs in pockets in the ore 

m considerable quantities. 

WILLEMITE 

Willemite, the rare anhydrous silicate of zinc, has 

been found at o_nly one place in the Magdalena districtin the Stonewall mine, along the incline on the Stonewall fault. The ore in this incline consists essentially 

of specks of native gold with cerussite and willemite 

in a gangue of silicified limestone and a little microscopic barite. The willemite occurs in abundant, small 

to microscopic rosettes or spherulites of stubby prismatic crystals (see pl. 26, 0). 

GOSLARITE 

Goslarite, the water-soluble hydrated zinc sulphate, 

is, like melanterite (p. 92), found only as coatings on 

the walls of mine workings where water that has 

leached zinc from sulphide ore has evaporated. Goslarite forms white fibrous masses and silky tufts as 

much as 4 inches long, but they are so delicate that 

good specimens ·cannot be obtained. 

ZINC-BEARING CLAY OR "TALLOW CLAY" 

The "tallow clay" of the Magdalena district resembles the "tallow clay" of the Mississippi Valley leadzinc deposits, which when moist has much the 

appearance of chocolate-brown tallow. It is regarded 

by the miners in the Magdalena district as a good 

guide to zinc carbonate ore. The most distinct occurrence noted is in the Black Cloud mine, where the clay 

has replaced limestone along a nearly vertical fissure 

(see fig. 10). An analysis of this material by J. fl. 

Fairchild shows it to contain only 0.5 percent of zinc 

and an estimated 0.5 percent of copper. The "tallow . 

clay" of Arkansas ranges from 10.6 to 30.2 percent 

of zinc, which is believed by Branner 40 to be present 

as the silicate hemimorphite (calamine). Similar clay 

at Leadv~lle contains from.- 18 to 35 percent of zinc, 

the percentage of zinc varying inversely as that of 

alumina.41 

.w Branner, J. C., Zinc and lead region of North Arkansas: Arkansas 

Geol. Survey Ann. Rept. for 18!:12, vol. 5, pp. 198, 266. 41 Loughlin, G. F., The oxidized zinc ores of Leadville, Colo. : U. S. 

Geol. Survey Bull. 681, pp. 24-28, 1918. Emmons, S. F., Irving, J. D., 

and Loughlin, G. F., Geology and ore deposits of the Leadville mining 

district, Colo.: U. S. Geol. Survey Prof. Paper 148, pp. 160-162, 1927. 

0 5 Feet 

FIGURE 10.-"Tallow clay" replacing limestone along a fissure beneath 

a cap of silicified limestone and passing downward into black manganese-stained material. It shows fine horizontal banding. The 

transition zone between it and limestone is only an inch thick. Black 

Cloud mine, tu:1nel level. 

The "tallow clay" of the Magdalena district is attributed mainly to the replace1nent of limestone ·along 

fractures by alumina, silica, and small quantities of 

zinc, carried by descending water in colloidal solution 

and probably in fine suspension also. The process is 

comparable to the treatment of slimes by lime in oredressing operations. The flocculating action of lime on 

colloids is well known, and the flocculated material 

may even repiace the precipitating agent. 

COPPER MINERALS 

SULPHIDE ZONE (HYPOGENE) 

CHALCOPYRITE 

Chalcopyrite, the commqn sulphide of copper and 

iron, is the only original copper mineral that we found 

in the district. It occurs in two forms: (1) Visible 

irregular bright yellow to tarnished grains, commonly 

very small, but in places as much as an inch in diameter; (2) minute to microscopic specks, blebs, and 

ljnear forms enclosed in sphalerite. The first variety 

forms inconspicuous interstitial grains in the pyritic 

copper ore iD the basal part of the Kelly limestone, 

especially in the Graphic-Waldo and Nitt mines. It is 

present ·in the pyritized monzonite north of the Nitt 

mine, and also forms large irregular grains or lumps, 

commonly associated with sphalerite and galena, in 

remnants of sulphide ore in 'outlying parts of the 

district. The largest lump noted-an inch in diameter-was in galena ore from the Black Cloud mine, 

but some of the cavities lined or filled with limonite 

in partly leached ore may represent still larger lumps . 

It is not known that any copper sulphide ore cmnposed 

mainly of these lumps has been shipped, but they have 

undoubtedly been the source of ·some small bodies of 
MINERALS OF THE' M~GDALENA DISTRICT 95 

rich oxidized ore, notably in the Young America mine. 

Under the microscope the boundaries between this 

variety of chalcopyrite and sphalerite commonly appear straight and smooth without clear evidence of 

relative age, but close examination usually shows that 

they connect with veinlets of chalcopyrite in sphalerite 

and therefore appear to be ~t least in part the younger. 

V einlet~ of chalcopyrite cut pyrite, and chalcopyrite 

is also interstitial to specularite (see pl. 27, A). Chalcopyrite is cut by veinlets of galena, but in one sp~cimen found in the office of the Graphic-Waldo mine, ' r chalcopyrite is interstitial to galena: 

The microscopic specks and other forms in the 

sphalerite are illustrated on plate 27, B, 0, and D. 

They have been regarded by some as products of U_!lmixing from a solid solution and by others as products of replacement effected by infiltrating solutions. 

Our microscopic investigations and a _ few experiments, 

though inconclusive, lead us to favor the replacement 

theory and to infer that the iron in the chalcopyrite may 

have been derived from that in the replaced sphalerite. 

The chalcopyrite specks, except those in the smallest 

sphalerite grains, are commonly arranged in rows or 

zones parallel to the edges of the enclosing grains and 

near to them. The border of clear sphalerite is 1 characteristic. Where large grains of chalcopyrite S~re in 

contact with sphalerite the inclusions tend to concentrate along this contact in preference to others, but inclusions are likewise clustered alorig contaqts with 

other ore and gangue minerals and along incipient 

veinlets (see pl. 27, D). Rarely a few minute incl¥-

sions of galeha and pyrite are found associated with 

those of chalcopyrite, and galena and chalcopyrite may 

both be present in a single inclusion. . 

A thorough discussion of the subject is too long for 

presentation here but it may be pointed out that the 

restriction of the chalcopyrite ·specks to zones within 

the outer parts of sphalerite grains hardly conforms 

• to what would be .expected if the specks had 'formed 

by the unmixing of a solid solution, unless it is assumed 

that the solid solution evolved only during a late but 

not the latest stage in the growth of' the sphalerite. 

It could also be suggested that the zonally arrang~d 

chalcopyrite specks, like the minute blades of specularite in pyrite, represent slight oscillations in ·chemical 

equilibrium during transition from the sphalerite to 

the chalcopyrite stage of deposition; but the al'inement 

of chalcopyrite specks along veinlets in sphalerite (pl. . 

27, D) implies deposition subsequent to the crystallizing and later fracturing of the sphalerite. A copper 

solution seeping along fractures and grain boundaries 

could penetrate sphalerite along cleavage planes, react 

with minute quantities of its iron and sulphur, and, 

when ~aturated, could deposit the specks of chalcopyrite. The parallel rows suggest a rhythmic process 

analogous to the ~ormation of diffusion rings in gels. 

BORNITE 

We found no bornite in the district, but Wuestner 42 

states that it is sparingly present. 

SULPHIDE ZONE (SUPERGEI;iE) 

CHALCOCITE 

Chalcocite or copper alance, the richest of the cop- ' b . 

per sulphides, is not abundant at Ma~dalena: This 

scarcity is probably due. to the ease with whiCh ~he 

oxidation products of chalcopyrite react promptly with 

the limestone wall rocks to form copper carbonates. 

Where the ore is encased in silicified limestone or in 

other siliceous rocks, however' and the liberated copper 

can be carried in solution into the sulphide zone, chalcocite has had rriore opportunity to form. This condition applies especially to the copper sulphide ?re 

shoot in the Graphic-Waldo mine, which is floored With 

· araillite and walled with siliceous and metamorphosed 

beds of the lower Kelly limestone. There sooty, black 

chalcocite fills cracks and small cavities, ,especially in 

chalcopyrite and pyrite, and coats them :Vith bl~ck 

films. It has replaced chalcopyrite along minute veinlets the middles of which are filled with carbonates. 

Th~ deepest point at which chalcocite has been found 

in the Graphic-Waldo mine is on level 10, about 290 

feet below the bottom of the thoroughly oxidized zone. 

There -it is associated with coarse-grained pyrite in a 

chloritic gangue. ;_ 

Crystalline chalcocite is present in the Stonewall 

and doubtless other mines on the upper slope of the 

range, where the ore bodies are overlain with silicified 

limestone; and very small quantities ,of chalcocite have 

been noted in the pyritized monzonite north of the 

Nitt mine. At the Iron Mask mine in South Camp 

massive crystalline chalcocite intergrown with argentite ( ~) is present in a vein that cuts highly oxidiz_ed 

silicified red rhyolite. Rounded fragments of pyrite 

are the only representatives of origin~l ore minerals 

in the-vein. .Alteration of the chalcocite through covellite to malachite is well advanced. 

COVELLITE 

Covellite a ·dark-blue copper sulphide, is about as ' . generally distributed as chalcocite and, like chalcocite, 

occur's as minute to microscpic grains in close association with chalcopyrite, galena, and chalcocite. It 

has replace chalcopyrite to a considerable degr~e, 

notably in the copper shoot of the . Graphic-Waldo 

mine (pl. 27, A) ; but it has replaced galena along 

grain boundaries and cracks to a greater degree. Q'ovellite and anglesite, clearly visible to .the unaided 

eye~ occur together where galena is associated ·. with 

much chalcopyrite, suggesting that cupric sulphate, 

· derived by the oxidation of chalcopyrite, has reacted 

42 Wuestner, Herman, op. cit., p. 128. 
96 MAGDALENA MINING DISfrRICT, NEW MEXICO 

with the adjacent galena to produce cupric sulphide 

( covellite) and lead sulphate ( anglesite). 

At the Iron l\1:ask mine covellite is the first product 

of the oxidation of chalcocite. \ As seen under the 

microscope, it penetrates the chalcocite and is bordered 

or penetrated in turn by the products of further oxidation-native copper, cuprite, and copper carbonates. 

OXIDIZED ZONE 

MALACHITE 

Malachite, the green basic copper carbonate, is a 

common minor constituent of oxidized ore throughout 

the district and corresponds in quantity and distribution to chalcopyrite in the sulphide ores. It forms 

films, crusts, and crystalline aggregates and is present 

along the edges of worked-out stopes. Wuestner says 

that it has replaced azurite and has formed pseudomorphs after crinoid stems and after small octahedra 

of cuprite, some of which have been changed to an 

unidentified white mineral.43 He also says that it has 

altered to aurichalcite. 

AZURITE 

Azurite, the blue basic copper carbonate, is ·rnore 

prominent than malachite, though not necessarily more 

abundant. A common mode of its occurrence is as 

balls and knobs composed of innumerable flat plates. 

It is found in cavities in cellular smithsonite and · on 

crusts of clayey material, malachite, aurichalcite, 

hydrozincite, allophane, and oxides of manganese and 

iron. On a specimen of secondary minerals from the 

Juanita mine, azurite has altered in varying degrees 

to an undetermined white mineral of a radiate fibrous 

structure resembling that of the hydrous copper silicate bisbeeite; but the mineral, according to spectrographic tests by George Steiger, is a silicate of alumrnum and magnesium. 

CHR.YSOCOLLA 

The hydrous copper silicate chrysocolla is rare in 

the limestone areas of the Magdalena district, but it 

is common in veins in andesite in the area adjoining 

the main district to the west and northwest. 44 The 

blue allophane that is common in the oxidized ·ores 

contains copper that is supposed to be prese~t as 

chrysocolla. 

NATIVE COPPER 

Native copper is common, according to Brinsmade,45 

as "thin leaves or as l'liggerheads." It also occurs in 

arborescent forms, embedded in cuprite,46 and as crusty 

scales and veinlets in limestone that has been partly 

replaced by zinc carbonate. An ore body said to contain "lumps of native copper too big for two men to 

4

3 Wuestner, Herman, op. cit., p. 128. 

44 Lasky, ,s. G., op. cit., p. 38. 45 Brinsmade, R. B., op. cit., p. ·50. 

;~.a Wuestner, Herman, op. cit., p. 130. 

lift" 47 was stoped in the southern part of the GraphicWaldo mine between levels 5 and 6. 

CUPRITE 

Cuprite, the red oxide of copper, occurs 48 in masses 

that here and there contain native copper and as beau- · 

tifully crystallized, highly modified cubes and dodecahedrons that fill cavities in the massive material. Very 

small octahedrons, altered to malachite or rarely to 

azurite, are also present. 

TENORITE 

Thin scales of tenorite, the black cupric oxide, fill 

cavities in native copper.49 

CHALOANTHITE 

Chalcanthite, a hydrous copper sulphate, commonly 

known as "blue vitriol," occurs sparingly in old workings and open fissures where it has been formed. by 

evaporation of copper sulphate solutions. 

ANTLERITE 

Very small quantities of antlerite, CuS04.2Cu(OH) 2 , 

associated with spangolite and azurite, are present on a 

specimen of cuprite kindly furnished by Wuestner. The 

optical properties were determined by W. T. Schaller as 

follows: Orthorhombic, biaxial, positive. Obtuse bisectrix normal to cleavage, 2V (acute) medium large, dispersion r<v. Refractive indices: a(yellowish green)= 

1.725±0.003, fi=l.735±0.003, y(green) =1.785±0.005. 

SPANGOLITE . 

The same cuprite specimen that contains antlerite contains larger quantities of a green mineral with a bluish 

tinge, which was identified by W. T. Schaller as spangolite, Cu6AlClS010.9H20. This is the mineral provisionally referred to as gerhardtite by Wuestner. The 

presence of chloride, sulphate, aluminum, and abundant 

copper was verified by qualitative chemical tests. The • 

mineral has a perfect basal cleavage on which are produced readily the triangular etch figures 50 with dilute 

sulphuric acid (1: 50), so characteristic of spangolite. 

The optical properties of the spangolite from the 

Magdalena district are: Uniaxial, negative. €(nearly 

colorless in very thin pieces)= 1.630, w (green, with a 

bluish tinge) = 1.678. These indices of refraction are 

slightly lower than those previously determined on 

spangolite from Arizona, namely, €=1.641, w=1.694. 

CYANOTRICHITE 

Deep-blue compact masses of radiating fibers, about a 

millimeter thick, are sparsely present in a s.econd small 

47 Brown, C. T., oral information, l915. 

48 Wuestner, Herman, op. cit., p. 130. 4 o Idem, p. 128. 00 Dana, J. D. and E. S., System of mineralogy, 6th ed., p. 920, figs. 4 

and 5a, 1909. 
GEOLOGICAL SURVEY 

A. MAGNETITE (m) ENCASING SPECULARITE (spe). 

Edges and cgpecially ends of specularite blades are ragged, as if 

parlly replaced hy magnetite. Black is quarlz. Graphic-Waldo mine. 

C MAGNETITE PSEUDOMORPHS (m) AFTER 

SPECULARITE. 

Dark area includes quartz and hedenbergite. From same specimen as plate 29, A. Graphic-Waldo mine. 

PROFESSIONAL PAPER 200 PLATE :!3 

B. SPECULARITE-MAGNETITE AGGREGATE, SHOWING 

PARTIAL REPLACEMENT OF SPECULARITE (spe) BY 

MAGNETITE (m). 

Black comprises quartz and calcite. Nitt mine. 

D. MAGNETITE (m) AND PARTLY REPLACED SHEAF OF 

SPECULARJTE BLADES (spe} IN A POLISHED CRYSTAL 

T•'ACE OF PYRITE. 

Black areas arc cavities. Graphic-Waldo' mine. 
GEOLOGICAL SURVEY 

A. BANDED MIXED-SULPHIDE ORE FROM KELLY MINE. 

(1) Specularite (spe) 'and pyri'te (py) in a calcite-qnartz-chlorite 

matrix; (2) sphalerite (sp) and galena (g) replacing calcite, quart7, 

and chlorite; (3) calcite and quartz, continuous with band 2 ani! 

grading into band 4; (4) limestone; (5) late calcite-pyrite vein. 

· ;:~ C. INTERFINGERING PYRITE lpy) AND SPECULARITE 

(spe) WITH SPHALERITE (sp) IN A CARBONATE GANGUE. 

·white dots in sphalerite are inclusions of cl~al opyri •·. Nitt mine. 

PROFESSIONAL PAPER 200 PLATE 21 

B. ENLARGEMENT OF PART OF A. 

Shows small pyrite pseudomorphs (ps) after specularite and inclusions 

of specularite (spe) in pyrite. 

D. PYRITE CRYSTALS (py) AND SPECULARITE-MAGNETITE BLADES (spe} IN QUARTZ GANGUE. 

Pyrite shows crystal boundaries against the gangue hut irregular 

boundaries caused by growth against the earlier specularitemagnetite blades. The pyrite crystal near the .lower left corner has 

grown around one of these blades. Black area s are pits. Kelly mine. 
GEOLOGICAL SURVEY 

A. PYRITE CRYSTAL (pyJ WITH A ZONE OF SMALL SPECULARITE BLADES (spe). 

Black areas are pit~ from which specularite bas been removed during 

polishing. r.angue is chlorite. Graphic-Waldo mine. 

PROFESSIONAL PAPER 200 PLATE 25 

/1. CELLULAR SMITHSONITE ("DRY BONE ORE"). 

C. MASSIVE ZINC CARBONATE THAT HAS REPLACED THE "SII.VER PIPE" BED OF THE KELLY LIMESTONE. 

rn, Manganese oxides. Kelly mine. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 26 

A. CRUSTIFORM FIBROuS SMlTHSONITE. 

(sJ Bluish-green translucent smitheonite, (h) hydrozincite, (fs) ferroan smithsonite, (a) aurichaleil c. 

11. CONCENTRIC AMETHYSTINE, WHITE, AND YELLOW LAYERS OF SMITHSONITE SURROUNDING A CELLULAR MIXTURE COMPOSED MAINLY 

OF BROWN IRON OXIDE, GREEN MAI,ACHITE, AND WHITE SMITHSONITE. 

C. PUOTOJ\UCROGRAPH OF ORE FROM STONEWALL MINE. SHOWING LATH-SHAPED CRYSTALS OF BARITE (1,) AND ROSETTES OF WlLLEMITE (w) 

IN A MATRIX OF CERUSSITE AND CALCITE. 
GEOLOGICAL SURVEY 

A. CHALCOPYRITE (cp) INTERSTITIAL TO LIGHT.GRAY 

BLADES OF SPECULA RITE (spe) AND PARTLY REPLACED 

llY DARK-GRAY COVELLITE (cv J. 

Large white crystals in lower part of illustration are pyrite (py). 

Stope below level 5, Graphic-Wahlo mine. 

C. INCLUSIONS OF CHALCOPYRITE IN SPHALERITE tsp) 

SEGREGATED NEAR AND PARALLEL TO CONTACT 

WITH A CONTINUOUS AREA OF CHALCOPYRITE (cp). 

Note narrow, clear border of the sphalerite and the tendency to linear arrangement of the chalcopyr:te inclusions. Grand Tower mine. 

PROFESSIONAL PAPER 200 PLA'fE 2i 

B. INCLUSIONS OF CHALCOPYRITE (WHITE DOTS) IN 

SPHALERITE (sp) SEGREGATED NEAR CONTACTS WITH 

SPECULARITE (spc). 

Dark borders along the · specularite blades seem to be either smith- sonite or siderite. Irregular inclusions of magnetite (m) in the large specularite crystal at right edge. Nitt mine. 

D. INCLUSIONS OF CHALCOPYRITE IN SPHALERITE (sp) 

PARALLEL TO ITS CONTACTS WITH GALENA (gn) AND 

QUARTZ (q). 

The deviation of the chalcopyrite from visible boundaries in left central part is inferred to conform to invisible grain boundaries within a sphalerite aggregate; likewise the roughly circular cluster of inclusions in the upper grain of this aggregate is thought to represent a 'surface near the original surface of the grain and about parallel to it. Graphic-Waldo mine. 

MINERALS OF THE MAGDAL,ENA DISTRICT 97 

· piece of cuprite (Wuestner No. 4417) collected at the 

Kelly mine between 1900 and 1905 by Mr. Wuestner. 

Although at first thought to be one of the blue copper 

silicates, the blue fibers are probably cyanotrichite. 

On optical examination W. T. Schaller found that the 

minute fibers ex~inguish parallel, are strongly pleochroic, and agree with cyanotrichite in their. indices of 

refraction, which are as follows: a (normal to fibers, 

nearly colorless)= 1.59; ,8= 1.62; Y, (parallel to fibers, 

deep blue) =about 1.65. 

Qualitative tests showed the presence of aluminum 

and sulphate but no chloride. · 

Half a centimeter away from the cyanotrichite is a 

little spangolite, bbth minerals being hydrous sulphates 

of copper and aluminum, spangolite containing chlorine 

in addition. Their formulas are: Cyanotrichite, 

Cu4At$01o·8Hz0; spangolite, Cu6AlClS010.9H2 0. 

LEAD MINERALS 

SULPHIDE ZONE 

GALENA 

Galena, lead sulphide, is present in most of the ores 

in the Magdalena district, the proportion of galena to 

the other sulphides increasing with distance. from the 

monzonite contact. According tothe superintendent at 

the Nitt mine, a little galena was found in one stope, and 

a few microscopic specks were noted in sphalerite in 

one specimen from that mine; but it first appeared in 

appreciable quantities in the Graphic-Waldo mine 

about 300 feet south of the contact. . 

In most places it is a subordinate constituent of mixed 

sulphide or~ and is very fine grained, but in the outer 

parts of the district it is very much coarser grained and 

in places is by far the predominating ore mineral. 

There temperature and pressure during mineral deposition were relatively low and less subject to rapid 

changes,. and the ore-forming solutions, after deposition 

of considerable quantities of pyrite and zinc blende, were 

relatively dilute but relatively rich in lead. All the ores 

seen in the outlying parts of the district, however, have 

been partly leached, and their original content of zinc 

blende was doubtless much higher tlian it is now. Microscopic study shows that although the boundaries between the grains of ga!ena and sphaler:ite or chalcopyrite are commonly irregular, galena is clearly interstitial 

to some sphalerite and forms veinlets in both minerals. 

One specimen with chalcopyrite interstitial to galena has 

already been noted. In general the deposition of galena 

appears to have followed that of chalcopyrite, which had 

already followed that of sphalerite, but available evidence is somewhat conflicting. 

Remnants of galena are present in the oxidized ores 

as kernels surrounded by anglesite and cerussite and 

are locally associated with . plumbojarosite. 

The etching of ·polished specimens of galena discloses microscopic inclusions of some other. mineral or 

minerals, a very common feature of silver-bearing 

galena. Some of· these inclusions are crystals or 

irregular spots· and others are thin threads along clea vage planes or grain boundaries. These inclusions are 

further discussed on page 98. 

OXIDIZED ZONE 

ANGLESITE 

Anglesite, lead sulphate, is common as the first product of oxidation of galena, and its occurrence as thinbanded gray to white crusts surrounding nodules of 

galena in the oxidized zone is so generally characteristic that no special description is necessary. It shows 

all stages of alteratien to cerussite. 

CERUSSITE 

Cerus~ite, lead carbonate, is present in the oxidized 

ore of all the mines, and in some of the ore shoots it 

is commercially the most important mineral. In the 

early days of the . district effort was· confined largely to 

the mining of slightly consolidated cerussite or "sand 

carbonate" ores near the surface: Silliman 51 described 

a body of lead carbonate ore in the "J uaniata" 

(Juanita~) mine that was 40 to 60 feet 1Vide. 

Cerussite generally occurs as glassy masses or aggregates of prismatic to bladelike crystals. The cerussite 

is typically derived from anglesite as the second step 

in the oxidation of galena, and in places it preserves 

the anglesite banding. The color of pure cerussite is 

gray to white, but much of the cerussite mined is 

stained reddish-brown or yellow. by iron qxides ~nd 

perhaps in part by plumbojarosite. 

Although most of the cerussite was formed practically in place, some of it was transported for short 

distances, as is shown by veinlets and small clusters 

of cerussite crystals that occupy fractureS! in otherwise unmineralized rock near ore bodies. Some move-

. ment and concentration of lead as carbonate within an 

ore shoot is illustrated by a highly cellular spongy 

specimen from the Graphic-Waldo mine. This specimen is composed of cerussite crystals in random or·ientation, cemented and coated wtih iron and manganese 

oxides. The prismatic cer'ussite crystals range in 

length from 1 millimeter to 12 millimeters and project 

into the openings in the mass and bridge them. The 

small crystals, n1any of which are white and unstained, 

have grown at ra1;1dom in large part upon the surfaces 

of the larger crystals. 

PLU.MBOJ AROSITE 

Plumbojarosite, a basic sulphate of lead and iron, 

Is chemically the same as jarosite except :for the replacement of potassium by lead. It is prominent in 

the outcrop at the large glory hole of'the .Hardscrabble 

at Silliman, Benjamin, Jr., Mineral regions of southern New Mexico; 

Am. lust. Min. Eng. '.rrans., vol. 10, pp. 424- 444, 1882. 
98 MAGDALEN A MINING DISfl'RICT, NEW MEXICO 

mine, and Lasky 52 reported its presence at the Papa 

prospect. of the Water Canyon district, which adjoins 

the Magdalena district ou the southeast. It occurs in 

minute crystalline flakes that are very similar in appearance to those of jarosite, from which they can be 

reliably distinguished only by optical or chemical 

tests. 

VANADINITE 

V anadinite, a lead chlorovanadate, has not been recognized within the area mapped, but Lasky 5 3 .. reports 

some from prospects about llh to 2112 miles north of 

Magdalena on the Jack Frost, Night Hawk, an~ 

Pleasant View groups of claims. It forms an 

incrustation on quartz. 

SILVER MINERALS. 

SULPHIDE ZONE (HYPOGENE) 

All the sulphide ores contain a little silver whose 

exact mode of occurrence is not known. No undoubted 

primary silver minerals have been found. The galena 

of the ore contains microscopic inclusions of various 

forms that become visible upon polished surfaces etched 

with hydrochloric or nitric acid. Concavo-cubic outlines are common. Other forms include dots of indistinct outline, stubby and elongate rods, and very 

thin threads that follow grain boundaries or cleavage 

planes in the galena. 

Such inclusions, common in the galena of silverbearing ores, have been described by different 

authors 5 4 as inclusions of argentite, proustite, 

pyr.argyrite, or tetrahedrite. The inclusions are much 

too small to extract for analysis, and their nature may 

ony be inferred, although Nissen and Hoyt have shown 

that argentite can separate from a solid solution with 

galena and that when it does so it forms inclusions 

similar to those found in natural galena. Some of 

the inclusions in the galena at l\1agdalena may be of 

a silver mineral, but it is doubtful if they all can be 

as the silver content <?f the ore is so low. 

In addition to its probable presence in some of the 

minute inciusions in galena, silver is also present in 

some unknown form in the comparatively galena-free 

ores. An average assay of the zinc-copper ore mined 

close by the monzonite contact in the Nitt mine during 

1925-32 shows only 0.5 percent of lead but 2 ounces of 

silver to the ton. Brinsmade 55 states that the average 

sulphide ore mined in the district in 1906 contained 12 

percent of lead and from 1 to 5 ounces of silver to the 

52 Lasky, S. G., The ore deposits of Socorro County, N. Mex.: New 

Mexico State Bureau of Mines Bull. 8, pp. 53-54, 1932. 

63 Idem, pp. 42-43. 54 Nissen, A. E., and Hoyt, S. L., On the occurrence of silver in argentiferous galena ores: Econ. Geology, vol. 10, pp. 172-179, 1915. Lindgren, Waldemar, Mineral deposits, 3d ed., p. 970, 1928. Schneiderhohn, 

H., Anleitung zur mikroskopischen Bestimmung von Erzen, pp. 100, 104, 

105, 133, 208, 209, Berlin, 1922. Van der Veen, R. W., Minerography 

and ore deposition, vol. 1, pp. 47-48, The Hague, 1925. 55 Brinsmade, R. B., op. cit., p. 51. 

ton. Galena ore from the Black Cloud mine assayed 

13.5 percent of lead and 2 ounces of silver to the ton. 

Apparently the silver . is not confined to the galena 

but is also present in some unrecognizable form in or 

with some of the other minerals, as has been emphasized for the Leadville district, Colorado.56 Where the 

silver content of the ore is higher than ordinary, this 

lack of definite relations 1nay be attributable to submicroscopic supergene silver minerals in sulphide ore 

a short distance below the oxidized zone, as interpreted 

for the ore of the Ground Hog mine in the Central 

mining district, New Mexico. 57 

SULPHIDE ZONE (SUPERGENE) 

ARGENTITE ( I) 

A mineral not positively iQ_entified but like the 

silver ·sulphide argentite in ;nost of its properties is 

intergrown with chalcocite in the high-grade silver 

ore of the Iron Mask vein. As it seems to be contemporaneous with chalcocite, it is thought to be 

supergene. 

NATIVE SILVER 

Wire silver is found at the Anchor mine rn seams 

and crevices in the sulphides, chiefly galena, and in 

the gangue. The richest ore begins about 50 feet 

below the surface and is confined to a vertical zone 

about 75 feet deep. The vein below this zone contains 

scant sphalerite and very little silver; in other words, 

the silver is limited to a certain vertical zone with an 

abrupt change from good ore to almost worthless veinmatter. This change is very suggestive of supergene 

processes in or just below the oxidized zone. No native silver was noted in the two polished specimens of 

this ore examined, but the late E. H. '\V ells, 5

8 then 

president of the New Mexico School of Miites, stated 

that native silver was distinctly visible in polished 

specimens examined at that institution some time ago. 

The specimens were lost in the fire that destroyed the 

museum in 1928. 

Specks of native silver accompanied by pyrite occur 

at the Black Cloud mine in replacement quartz, which 

also contained minor quantities of galena, sphalerite, 

and secondary chalcocite and covellite. 

OXIDIZED ZONE 

CERARGYRITE 

All the oxidized ores, both lead and zinc, contain a 

few ounces of silver to the ton. Brinsmade 59 states 

that the oxidized lead ores contained from 2 to 5 

ounces of silver to the ton and the oxidized zinc ores 

somewhat less. The large body of lead carbonate 

66 Emmons, S. F., Irving, J. D., and Loughlin, G. Jj"\, Geology and ore 

deposits of the Leadville mining district, Colorado : U. S. Geol. Survey 

Prof. Paper 148, pp. 198-199, 1927. · 61 Lask.y, S. G., Distribution of silver in base-metal ores: Am. Inst. 

Min. Met. Eng. Trans., vol. 115 (Mining Geology), pp. 69-80, 1935. 58 Personal communication. 59 Brinsmade, R. B., op. cit., p. 51. 
MINERALS OF THEI MAGDAL,ENA DISTRICT 99 

mined in the Juanita mine in the early days contained 

from 8 to 10 ounces of silver to the ton,60 and some 

of the references to ore mined in the earliest days of 

the district imply a much greater content. The exact 

nature of the silver in the oxidized ore has not been 

determined, but in the richer oxidized ores at least it 

was presumably in horn silver, or cerargyrite, which 

is common in the oxidized silver ores throughout the 

West. 

NATIVE GOLD 

Most of the sulphid~ and oxidized ores have contained very little gold, as is shown in the table of 

production, but native gold was visible in oxidized 

ore of the Stonewall mine. This gold occurred as 

grains and wires accompanied by cerussite and ·willemite in partly silicified -limestone. Galena was found 

on the lower side of one pocket of gold ore, and it was 

reported that wire gold occurred with the galena. Ore 

with an average gold content of 1 ounce to the ton 

was shipped from the Young America mine, probably 

before 1900, but there is no information regarding th~ 

mode of occurrence of the gold. 

MANGANESE MINERALS 

SULPHIDE ZONE 

Although manganese is present in all the oxidized 

ores, the primary mineral or minerals from which it 

was derived are not clearly evident and may onJy be 

inferred. The siderite found at the Germany mine 

may contain manganese and very probably some calcite 

contains ·manganese. The altered mineral described 

under "Hedenbergite" and the calcite that has replaced 

undoubted hedenbergite also contain manganese. 

OXIDIZED ZONE 

PYROLUSITE, PSILOM:ELANE, AND WAD 

The manganese oxides pyrolusite and psilomelane 

and wad, the earthy impure variety of psilomelane,61 

may -be individually recognizable in isolated occurrences, but· they are generally so mixed with one another an.d with iron oxides that exact mineral species · 

cannot be identified. These mixtures, accompanied by 

clay minerals, are prominent along the borders of zinc 

and lead carbonate ore bodies, particularly on their 

undersides. The massive, buff-colored variety of zinc 

carbonate is impregnated with dendritic manganese 

stains, and manganese and iron oxides along cleavage 

planes of calcite_ are common. 

CADMIUM MINERAL GREENOCKITE 

Greenockite, cadmium sulphide, occurs as a very thin 

orange-yellow coating upon smithsonite and as a yellow 

stain within it. Partial analyses of the yellow smithsonite are given on page 93. 

oo Silliman, Benjamin, Jr., op. cit., p. 426. 

61 Orcel, J., and Pavlovitch, S., Les caracteres microscopiques des 

oxydes de manganese et des manganites naturels: Soc. fran0. mineralogie 

Bull., vol. 54, pp. 108-179, 1931. 

GANGUE MINERALS 

The gangue mineral_s a,re treated for convenience in 

the following order: silicates formed at relatively high 

temperature al(d characteristic of the "contact-metamorphic" zone; silicates, quartz, barite, and fluorspar formed 

at moderate to relatively low temperatures; and clay 

m~nerals formed only in and just below the oxidized zone 

by descending waters. 

TOURMALINE 

Tourmaline, a complex borosilicate of aluminum with 

magnesium, iron, or the alkali metals, occurs in a small 

pegmatite ·dike about an inch thick in pre-Cambrian 

granite east of Anchor Canyon but isprobably of the 

same general age as the ore deposits (p. 49). Tufts of 

tourmaline occur/ on fracture surfaces in the argillite 

and felsite near the Tertiary ( ~) granite and. also in 

the aplite dikes in monzonite south of Hardscrabble 

Camp. Its occurrenc~ in the aplite correlates it with the 

final stage of monzonitic intrusion, during or soon after. 

which the early high-temperature silicate minerals in the 

sedimentary rocks were formed. 

WOLLA~TONITE 

.Wollastonite, a calcium silicate, is a light gray to 

white mineral that occurs both in fine-grained to dense 

masses and in coarse-grained aggregates of elongate or 

fibrous crystals. It is characteristic of contactmetamorphic lime~tone and has been found in masses 

of Kelly limestone enclosed in monzonite just north of 

Oak Spring and in Tertiary ( 1) granite at the Hard,. 

scrabble mine. That at Oak Spring closely resembles · 

fine-grained margie except for its higher specific gravity. 

That at the Hardscrabble mine, in the caved roof of the 

stope east of the north glory hole, includes both the finegrained sugary variety and a relatively c~arse-grained · 

variety in sharp contact with each other. Under the 

m~croscope the fine-grained variety proves. to be essentially pu_re wolla~tonite, whereas the coarse-grained 

variety is a mixture of wollastonite and calcite. 

ANDALUSITE 

Andalusite, an aluminilm silicate, has been found only 

in hornfels that evidently marks the basal Sandia beds 

along the west edge of the Kelly limestone at the Hardscrabble mine. There it forms a few scattered grains 

associated with sericite and chlorite. This basal peel 

is in contact with the granite that encloses the limestone. 

DIOPSIDE 

Diopside, a calcium-n1agnesium silicate of the pyroxene group, is a common constituent of contact-metamorphic limestone, mostly in association with wollastonite 

and garnet. At Oak Spring it is associated with wollastonite in Kelly limestone, whe~ the two minerals 

have· been converted in part to a dense or fine-grained 

aggregate. 
lOU MAGDALENA MINlNG DISfl'RIC'l', NEW MEXICO 

On level 3 of the Nitt mine a block of limestone enclosed in monzonite but close by a. sulphide ore body 

has been changed into a medium-grained rock composed 

of diopside crystals in a matrix of calcite. The diopside 

occurs as prismatic grains that are slightly altered to 

serpentine (antigorite). Its indices of refraction 

(a=1.68; ,8=1.69; y=1.71) indicate that it contains 

about 25 percent of the hedenbergite molecule. 

East of Granite Mountain a limestone layer in the 

upper quartzite member of the Sandia formation is im-

!pregnated with microscopic. transparent specks whose 

birefringence suggests diopside. They are associated 

with minute magnetite grains, serpentine, and chlorite. 

HEDENBERGITE 

Hedenbergite has a formula analogous to that of 

diopside, but it contains iron instead of magnesium. It 

is found farther from igneous contacts than diopside, 

and its association with other minerals imtplies that it 

was formed at a lower temperature and during a later 

stage of mineralization than diopside. Chemical tests 

show that the hedenbergite from ~Iagdalena contains 

considerable manganese. It was present in the mixed 

sulphide ore collected by Gordon in the-Graphic mine 

in 1905 2 and in similar ore collected by Loughlin in 

the Linchburg tunnel in 1916. It forms fine-grained 

masses and also rosettes about half an inch in diameter 

and columnar sheaves as much as 2 inches long. The 

indices of refraction of the hedenbergite from the 

Linchburg tunnel are a= 1. 722; ,8 = 1. 733, y = 1. 7 48. 

The fresh mineral iB clear greenish black, but the altered mineral is dull green to brown. It is associated 

with garnet (andradite), specularite, magnetite, quartz, 

and calcite. Under the microscope it is seen to be 

considerably replaced by quartz and calcite and only 

poorly defined skeletal crystals remain that resemble 

groups .of parallel slender needles. (See pl. 29, A) . 

Similar material described by W uestner 63 as altered 

hedenbergite, and submitted by him to Lasky, resembles hedenbergite in structure and apparently con- . 

tains manganese; but it is intimately mixed with 

iron oxides and silicate minerals and cannot be positively identified. 

TREMOLITE AND ACTINOLITE 

A thin section of the metamorphosed limestone taken 

from a dump near Oak Spring shows tremolite associated with wollastonite, grossularite, diopside, muscovite, rare sanidine, and titanite. Gordon reported 64 

that the ores studied in 1905 contained tremolite, the 

magnesium-calcium amphibole, intergrown with pyroxene and associated with specularite and sphalerite; 

and W uestner reported the presence of actinolite, the 

62 Lindgren. Waldemar, Graton, L. C., and Gordon, C. H., op. cit., 

pl. 18, B. 

63,·wuestner, Herman, op. cit., p. 129. 

M Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., op. cit., 

p. 253. 

ferroan variety of tremolite, but, with the exception 

of the specimen from the dump near Oak Spring, no 

tremolite or actinolite was found during the later 

silrvey; however, ·pseudon1orphs of antigorite found on 

level 2 of the Nitt mine may represent former tremolite 

or actinolite. 

Radiating aggregates of specularite, pyrite, and zinc 

blende and a white material that resembled tremolite 

were found at several places in the Graphic-vValdo 

mine, but the white material proved to be calcite 

accompanied by a little quartz and chlorite. 

GARNET 

Garnet, though prominent in a few places, is a minor 

member of the high-temperature group. Two varieties-grossularite and andradite-are present, the first 

associated with wollastonite and diopside and the 

second with hedenbergite. 

Grossularite, the calcium-aluminum garnet, is conspicuous in metamorphosed - Kelly limestone at the 

Hardscrabble mine and at Oak Spring; at the east 

base of Stendel Ridge and in the low hill east of Granite Mountain it is present in limestone beds of the 

Sandia formation. It forms brown and green granular aggregates. Garnets of both colors are present 

at the Hardscrabble mine and Oak Spring. The index 

of refraction for the brown variety is about 1.76, and 

that of the green variety 1.74, both of which correspond to grossularite. Both varieties are colorless and 

indistinguishable in thin section, and both contain con- · 

centric zones, some of which are anisotropic. 

Yellowish-brown andradite, the calcium-iron garnet, 

has been found in the Linchburg tunnel associated with 

hedenbergite, quartz, calcite, specularite, magnetite, 

and sulphides, which have replaced the "Pinto" bed of 

the lower Kelly limestone. It appears to have formed 

later than the hedenbergite but earlier than the other 

minerals. Its index of n~fraction is 1.885. Its crystals, 

as seen in thin section, have six-sided and four-sided 

outlines and consist of "pyramids" whose apices meet 

in the center and whose bases correspond to crystal 

faces. This structure, according to Winchell, 65 is 

characteristic of the uvarovite-grossularite-andradite 

group. The "pyramids" contain concentric anisotropic 

zones. The garnet in the adjacent argillite is colorless 

and isotropic in thin section. Its index of refraction 

has not been determined. Garnet has also been reported from the edge of the zinc sulphide stope below 

level 9 of the Graphic-Waldo mine. 

EPIDOTE 

Epidote, a hydrous silicate of calcium, aluminum, 

and.iron, forms distinct dark-green bladelike to columnar crystals, which are sparingly present in the ores. 

It also forms dense green to yellowish-green veins and 

65 Winchell, A. N., op. cit., pp. 257-265. 
MIN.ERALS OF THE MAGDAL,ENA DISTRICT 101 

patches, especially In altered igneous and siliceous 

sedimentary rocks. Minute to microscopic grains are 

commonly associated with quartz, sericite, and chlo- · 

rite and add to the green color of altered rocks. Some 

of the limestone beds of the Sandia formation enclosed in monzonite on level 2 of the Nitt mine have 

been converted to rather coarsely granular epidote 

that so mew hat resembles the granular green garnet at 

Oak Spring. Limestone interbedded with the shales 

at the east base of Stendel Ridge is also green with 

epidote in places, as is the coarse breccia at the base of 

the overlying volcanic rocks. The breccia is composed 

of epidotized shale, limestone, and quartzite fragments 

in epidotized volcanic tuff. Another noteworthy occurrence of epidote is in small coarse-grained or pegmatitic veins of quartz, feldspar, epidote, and calcite 

that cut the monzonite near its contact with metamorph~c limestone at Oak Spring. 

SERPENTINE (ANTIGORITE) 

Antigorite, a variety of serpentine, occurs as an 

alteration product of one .or more of the magnesiumbearing silicates, particularly diopside, in contactmetamorphic zones, and also as a direct replacement 

product of limestone. On level 2 of the Nitt mine, 

pseudomorphs of antigorite after some elongate crystals whose form resembles that of actinolite or tremolite 

were found. The antigorite is pale brown to fleshcolored 'and is soft and highly cleavable. 

Serpentine is also present in fragments on two small 

dumps a little west and southwest of . the southeast 

corner of sec. 12, T. 2 S., R. 4 W. It· is intimately 

intergrown with chlorite. The serpentine-chlorite rock 

is banded with black layers of magnetite as much as an 

e]ghth of an inch thick. 

QUARTZ 

Quartz is the most wi.despread product of mineralization in the district. It forms massive veins of milky~ 

to gray quartz with or without conspicuous amounts of 

other minerals and fine-grained to dense masses of 

jasperoid that have repiaced limestone. Both of these 

massive varieties contain vugs and fractures lined with 

well-formed white to brownish quartz crystals. In the 

southernmost part of the district, chalcedonic quartz 

forms small geodelike growths, especially in the upper 

andesite. · . 

Quartz is least conspicuous in · the silicate zones near 

intrusive stocks and in the large bodies of specularitemagnetite and sulphide ores of the Graphic-W~ldo and 

Kelly mines. The average silica content of the sulphide 

ores mined in 1906 was about 10 percent.66 l\1ost of 

the ~re bodies, however, are connected with fissures that 

contain milky quartz, with or without other vein minerals. They also have small to conspicuous casings of 

66 Brinsmade, R. B.~ op. cit., p. 59. 

fine-grained quartz or jaspcroid. Quartz yeins, most 

of which are comparatively small, are more conspicu-

·ous in the outer parts of the district, where they cut . 

both the Tertiary ( ? ) volcanic and the pre-Cambrian 

rocks. The large prominent replacement veins of 

milky quartz in felsite southeast of Hardscrabble Camp 

and in monzonite and rhyolite porphyry south of 

Granite Mountain are striking exceptions to the veins 

as a whole. 

By far the greatest development of quartz is in the 

large masses of jasperoid that have replaced the Kelly 

limestone throughout the southeast part of the district 

. (pl. 28). Southeast of Grand Ledge tunnel and north 

of the Socorro highway the pre-Cambrian argillite is 

·also replaced by jasperoid. The masses that have replaced limestone contain many openings, some of which 

may express shrinkage during replacement but most 

of which represent incomplete replacement; many may 

even contain remnants of unreplaced limestone that 

have not been entirely removed by subsequent weather-

·ing processes. These openings are lined with small to 

large crystals of quartz,. SOille of which under the 

microscope show several stages of growth, as shown in 

figure 11. Some fractures in the jasperoid contain 

small veins of milky quartz, barite, and sulphides 

identical with the quartz veins elsewhere in the district. 

Under the microscope some specimens of j asperoid 

suggest the progress of replacement by the growth of 

small well~formed crystals in advance of the main mass. 

As the process continues and these crystals form a netorusy cavity 

I 

/ 

L lmrn:± 

~' IG nE 11 .- Micr·o!lrawing, showing four distinct ::;tages of g-J·owth of n 

quartz crystal in a drusy cavity in jasperoid: 1, Original crystal of 

clear quartz ; 2, accretion, also of clear quartz ; 3, zone containing 

considerable "dust" ; 4, clear quartz with radial structure. All four 

zones are tn optical continuity. Q, Adjacent qual"tz grains ln jasp.eroid. 
io2 MAGDALENA MINING DISfl'RICT, NEW ME.X!CO 

work,: the spaces between them become filled with 

anhedral grains, some of which are in optical continuity with the well-formed crystals. Similar wellformed crystals enclosed in sulphides indicate that 

silicification on . a relatively small scale has been overtaken by sulphide deposition that completed the replacement of limestone. Field observations, however, 

suggest that jasperization in the main occurred along 

a wavelike front that yielded a sharp contact between 

j asperoid and limestone. 

SERICITE 

Sericite, a fine-grained silky variety of muscovite, is 

an abundant constituent of argillite and altered igneous 

rocks and a minor constituent of quartz veins. In the 

· altered rocks it commonly impregnates or replaces feldspar grains, and where alteration has been very pronounced it has replaced other minerals, even including 

quartz. Parts of the pyritized monzonite in upper 

Hardscrabble Valley, for example, have been changed 

to aggregates of sericite, pyrite, and chlorite in nearly 

equal amounts. The serici~e is in part intergrown 

with chlorite and in part forms radial sheaflike 

growths. Where silicification has been extreme, any 

sericite formerly present has been replaced by quartz, 

but for the most part sericite and fine-grained quartz 

have been deposited simultaneously and represent a less 

extreme degree of alteration. 

· CHLORITE 

Chlorite, a dark green micaceous mineral, is commonly fine-grained and closely associated with sericite. 

For the most part it impregnates or replaces the dark 

silicate minerals of the igneous rocks, but it is also a 

constituent of altered sedimentary rocks and of mineral 

deposits. It is abundant in the pre-Cambrian argillite, 

gabbro, and diabase, accounting largely for their darkgreen or greenish-gray colors. It is also common in the 

Tertiary ( ~) igneous rocks, especially the monzonite 

and laniprophyre, and in altered shale, impure limestone, and quartzite. It is a prominent gangue mineral in some of the pyritic lenses of the Graphic-Waldo 

mine. 

THAUMASITE 

A white fibrous crystalline mineral with properties 

corresponding to those of thaumasite, a hydrous silicate-carbonate-sulphate of calcium, occurs as a. felted 

crust of silky fibers on some of the metamorphic limestone northeast of Oak Spring. The optical properties are as follows: €=1.47±; w=1.51±; the mineral is 

optically negative. It effervesces in hydrochloric acid, 

leaving a flaky residue of silica. 

SIDERITE 

Siderite is associated with galena, zinc blende, replacement quartz, and comparatively abundant pink 

barite on level 3 of the Kelly mine. Siderite crystals 

are also conspicuous in a vein near the south end of the 

Germany mine. The crystals occur as rpearly palebrown to white interlocking rhombs, as much as 2· millimeters in diameter. They coat vugs in the vein and 

adjoining silicified limestone and are also perched on 

botryoidal growths of sphalerite. 

All the siderite examined has an w index of refraction not much above i.82, which implies the presence 

of some other element, as the index w of pure siderite 

is 1.873. 

A massive granular carbonate resembling the man-

. ganosiderite of the Leadville district, of Colorado, was 

· found on levels 6 and 7 of the Graphic-Waldo mine 

and was the principal constituent of a bleached and 

apparently recrystallized 7 -foot · bed of limestone that 

lay between two ore shoots (see fig. 9). The associated 

ore and gangue minerals were specularite, magnetite, 

sulphides, quartz, and radiating blades of calcite. If 

similar carbonate with high contents of iron ~nd 

manganese was originally present in the ore bodies 

that have been thoroughly oxidized, the prominence of 

brown iron oxides, and especially the manganese oxides could be more readily explained. The contrast ·' in association: between this granular carbonate and the 

siderite noted above recalls a similar contrast at Leadville, where small crystals of siderite coat sulphide ore 

in the Tucson mine and large masses of manganosiderite in the same mine are replaced by sulphide ore. 67 

DOLOMITE 

The only dolomite seen-in a specimen collected by 

Philip Argall-lined the opening in the middle o£ a 

layered veinlet that cut a typical mass of specularite 

and interstitial quartz. The outermost layer of the 

veinlet was quartz followed by one of specularite, 

another of quartz, and next the layer of dolomite. 

The dolomite was pale pink and formed typical 

rhombs. 

CALCITE 

Calcite, besides being the principal constituent of 

the limestones, occurs in three forms that are o£ considerable significance in the interpretation of ore-forming processes. These forms are platy crystals in radial 

aggregates, long pointed crystals or scalenohedrons, and 

flat or disklike rhombohedral crystals. 

The platy crystals have been found in the sulphide 

ores of the Graphic-Waldo and Kelly mines and in 

metamorphic limestone on the dumps east of Granite 

Mountain. They give a distinctive appearance to the 

ore and the contact rock. They are white to light gray 

and are ·as much as 12 millimeters in length and 2 millimeters in width. In the ore they are accompanied 

by scales of specularite arranged along their radiating 

boundaries and by sphalerite and small amounts of 

a1 Emmons, S. F., Irving, J'. D., and Loughlin, G. F., Geology and ore 

depos-its of the Leadville mining district, Colorado: U, S. Geol. Survey 

Prof. :faper 148, pp. 152, 291, 1'927. • 
MINERALS OF THE, MAGDAL.ENA DiSTRICT 103 

other sulphides and quartz that have impregnated 

them but preserved much of their radial arrangement. 

As the thinner plates appear fibrous in cross section 

(pl. 29, A), aggregates of radiating and interlocking 

· crystals may be mistaken at first for such fibrous silicates as tremolite and hedenbergite (see p. 100). 

Some of the platy to fibrous calcite is so closely associated with these silicates as to indicate their pseudomorphous replacement by calcite, but this relation has 

·been obscured by the replacement of hedenbergite, and 

perhaps of calcite also, by quartz (pl. 29, A). 

East of Granite Mountain platy calcite is intergrown 

with fine-grained interstitial aggregates of chlorite, 

serpe:ptine, epidote, quartz, and garnet (pl. 29, B). In 

places lobes of chlorite and serpentine replace the edges 

of calcite crystals. Only. a few small, cattered grains 

of garnet occur, and they are most commonly enclosed 

in the platy calcite. 

Platy calcite is a relatively high temperature form, 

and aggregates of it are among the earliest products of 

crystallization in quartz-calcite-gold veins characteristic of the shallow or epithermal zone of ore deposition. 

The platy calcite of Magdalena, therefore, may have 

resulted from recrystallization of limestone during or 

soon after the development of the high-temperature 

silicates, and its tendency to radial arrangement may 

have been favored by the radial habits of the silicates. 

The specularite flakes may also have grown with the 

calcite or may have impregnated it along crystal 

boundaries. .Regardless of its exact mode of origin, 

this calcite is regarded as evidence of .mineral deposition at relatively high temperature and before the m~in 

sulphide stage. Qualitative tests on unstained calcite 

showed the presence of some iron, and the calcite 

associated with hedenbergite was found to contain 

considerable manganese. 

The scalenohedral calcite occurs mainly along fissures 

outside the margins or ends of ore shoots and to a . ' m1nor extent as vug and fracture linings within ore 

shoots. This mode of occurrence is typical of several 

districts 68 and evidently represents deposition by weak 

ascending or hypogene solutions that had become 

largely depleted of their metal content. Where the 

crystals have completely filled fissures they form veins 

with transverse columnar structure. · · 

The disklike or "nail-head" crystals are colorless and 

as much as half an inch in diameter. They are characteristic of the oxidized zones and are very commmi 

as cavity linings in bodies of iron and manganese oxide.· 

They are also present in oxidized lead and zinc ores and 

in the ~dj oining rocks. They are found coating hemimorph1te, the latest oxidized zinc mineral, and mark the 

very latest stage of deposition in tlie oxidized zone. 

68 Lindgren, Waldemar, and LQughlin, G. F., Geology and ore deposits 

of the Tintic mining district, Utah: U. S. Geol. Survey Prof. Paper 107, 

p. Ui9, 1919. Loughlin, G. ,F., and Behre, C. H., Jr., Zoning of ore deposits, Leadville district, Colorado: Econ. Geology, vol. 29, p. 230, 1934. 

ARAGONITE 

Aragonite, the orthorhombic form of calcium carbonate, has been reported by Wuestner 69 in a number 

of forms-delicate fibres coating other minerals, 

clusters of pseudohexagonal crystals in part changed 

to smithsonite, and botryoidal or mushroomlike, fibrous, 

and massive forms. 

BARITE 

Barite, barium sulphate, occurs in white to p~le-pink 

platy crystals as much as 4 inches in diameter. They 

form radiating and interlocking groups with interstitial quartz and fluorspar and are char.acteristic constituents of the gangu.e in the outlying deposits of the 

district, where the temperature of mineralizing solutions was comparatively low. The northernmost occurrence of it in the main ore zone south of the Nitt stock 

is on level3 in the southeast part of the Graphic-Waldo 

mine. It is present in the Kelly mine but only in spots 

along the margins of the ore shoots and in veinlets that 

cut the massive sulphide ore and are preserved in the 

~xidized ore. Some of the veinlets are nearly free from 

quartz and fluorspar. Barite is more conspicuous in 

the Juanita mine and is a characteristic gangue mineral from there southward. The barite in these outlying deposits was deposited before the sphalerite and 

galena that accompany it and before part of the quartz. 

The largest crystals seen, however, are in small prospects of little promise on the upper east slope of the 

range. Narrow veins of barite, quartz, and sulphides 

fill fractures in the extensive. masses of jasperoid or 

silicified limestone in the southeast part of the district. 

Barite with fluorspar and quartz is a principal gangue 

mineral in t:P,e Anchor vein, near the east edge of the 

larger _ stock of Tertiary (?) granite, and in several 

of the pr_ospects in the Granite Mountain area. 

FLUORSPAR 

Fluorspar, calcium fluoride,. forms colorless to green 

crystals of cubic to irregular outline as much as an 

inch in diameter. It is associated with barite, as noted 

abov~, but is more restricted to the outlying deposits 

and 1s most conspicuous in prospects of little promise. 

CLAY MINERALS 

Allophane, halloysite, beidellite, montmorillonite, 

kaolinite. 

Masses, veins, and patches of· clay or "talc'1, in part 

colored by red, brown, · and yellow iron oxides and 

. black m_anganese oxides, are common associates of 

the oxidized ores. They represent in part the 

original impurities in leached _limestone beds, particularly the "silver pipe", but the largest masses, derived 

largely through the leaching of overlying shaly rock, 

have replaced Kelly limestone along major faults and 

around oxidized ore bodies. Specimens from a most 

69 Wuest~er, Herman, op. cit., p. 129. 
/ 

104 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

conspicuous exposure at the outcrop of the Kelly ore 

body along the Kelly-Graphic fault on the north side 

of Kelly Gulch consist mainly of the amorphous mineral allophane, 'vhich is pale bluish or greenish and 

translucent on freshly broken surfaces but becomes 

chalky white after prolonged exposure. The bluish or 

greenish color is caused by a small amount of chrysocolla, and smne allophane is accompanied by the blue 

copper carbonate azurite. Some of the chalky 'white 

crusts have finely botryoidal surfaces and radiating 

structures, and those examined microscopically consist 

of other clay minerals derived from allophane; for 

example, material from a veinlet in the Juanita mine 

has been tentatively determined by C. S. Ross, of the 

U. S. Geological Survey, as halloysite that has crystallized from the allophane. Other material that forms 

white, platy rosettes on allophane more closely resembles beidellite. One pale blue specimen, from a 

vein cuttin,g zinc carbonate in the Kelly mine proved 

to be a mixture of halloysite and kaolinite. Kaolinlike 

material is the essential impurity in t.he "silver pipe" 

bed, but the claylike residues of zinc carbonate ores 

that have replaced the "silver pipe" bed resemble 

sericite microscopically. Some of the clay associated 

with zinc-carbonate ores may contain appreciable 

a1nounts of zinc, but the few samples tested showed 

only negligible quantities. (See p. 94.) 

The clay minerals beidellite-montmorillonite and the 

celadonite that occur in some of the volcanic rocks 

have already been described (p. 55). 

CELADONITE 

No oeladonite has been found in close association 

with ore bodies, but the celadonite and associated clay 

mineral in altered volcanic rocks, described on page 

30 and considered in cminection with processes of 

alteration (p. 55) 1nay be cited here as indicative of 

deposition under relatively low temperature conditions. 

DISTRIBUTION AND CLASSIFICATION OF MINERAL 

DEPOSITS 

The distribution, sizes, and general forms of most 

of the ore bodies that have been n1ined in the Magdalena district are shown on plate 30, which represents 

the area south of the Nitt monzonite ·stock, and in the. 

illustrations that accompany mine descriptions (pp. 123 

to 162). The largest deposits, which lie in the main 

ore zone between the Nitt stock and the town of Kelly, 

have replaced beds in the Kelly limestone both below and above the "silver pipe'' along fissures of 

northerly and north-northwesterly trend. The main 

ore bodies in the Graphic-Waldo and Kelly mines pitch 

north-northwestward along the intersections of the 

fissures with the west-dipping limestone beds. Their 

southern or upper parts, above the general level of 

pediment D (p. 74), are oxidized and include separate 

shoots of lead carbonate and zinc carbonate ore. At 

the bottom of the oxidized zo~e some rich copper ore 

has been found, particula:dy in the Graphic-Waldo 

. mine. Ore bodies in the Kelly mine are bounded on 

the east in places by small veinlike bodies that lie 

along the Kelly-Graphic fault. 

South of Kelly the main ore zone is represented by 

replacement bodies in the Juanita and South Juanita 

mines. Farther south the Kelly limestone has been 

downfaulted along the main ore zone and is exposed 

only underground at th() east end of the Linchburg 

tunnel, where some 'low-grade sulphide ore has been 

developed. At shallower levels, from Chihuahua Gulch 

to the south boundary of the district, the main ore 

zone i~ represented by veins that lie in or near the 

faults that separate pre-Cambrian from the Sandia 

and Madera formations. Most of these veins. ~re in 

the oxidized zone and have been worked for lead-silver 

ore, although a little high-grade copper-gold ore is 

said to have· been shipped frmn the Young America 

mine. Some mixed sulphide ore has been mined below 

the oxidized zone. 

East of the main zone, in the southeast part of the 

district, much of the Kelly limestone has been replaced 

by fine-grained massive quartz or jasperoid, ·and the 

ore shoots are small replacement masses or bunches 

that lie beneath or between masses of j asperoid and 

also just below the "silver-pipe" bed. They consist of 

partly or completely oxidized lead ore accompanied in 

part by small bodies of. oxidized zinc ore. West of the . 

main ore zone only small veins in Abo sandstone and 

volcanic rock have been found. very little ore has 

been produced from them. 

North of the Nitt monzonite stock the continuation 

of the main ore zone extends along Hardscrabble Valley and is represented by small prospects in pyritic 

monzonite and by the Vindicator vein (pl. 38), which 

occupies a fault between Madera limestone and Tertiary ( ? ) granite. To the east elongate replacement 

deposits of oxidized lead-silver ore in Kelly limestone 

have been mined in the Hardscrabble mine (pl. 38), 

and farther east, across the summit of the range, a 

vein cutting Tertiary ( ? ) granite has been worked in 

the Anchor. mine (fig. 27). 

No underground ·information is available on any of 

the small deposits in the Granite Mountain area and 

the area west of it; in fact, almost no records at all 

have been available to us regarding prospects in this 

area. To the south of the Magdalena district the small 

Water Canyon and Hop Canyon districts, briefly 

described by Lasky,70 may be considered continuations 

of the Magdalena district. Further consideration of 

distribution is most conveniently presented in the descriptions of the different classes of ore, particularly 

on pages 105-110. 

70 Lasky, S. G., The ore deposits of Socorro County, N. Mex. ; New 

Mexico School of Mines, State Bur. Mines and Mint!ral Resources, Bull. 

8, pp. 43-44 and 46-54, 1932. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 28 

A. PARALLEL BANDED SILICIFIED KELLY LIMESTONE. 

Looking down on surface of large boulder. Parallel cavities are lined with quartz crystals. Near crest of main range in southeastern part of district. 

B. BRECCIATED SILICIFIED KELLY LIMESTONE RECEMENTED BY LATER MILKY QUARTZ. 

Near crest of main range in southeastern part of district. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 29 

A. PHOTOMICROGRAPH OF ORE FROM GRAPHIC-WALDO MINE. 

Shows specularite (spe), hedenbergite (h),' quartz (q), calcite (c), and sulphides (8). Skeletal crystals of hedenbergite (sh) are largely replaced by quartz, and the relation of the 

pseudomorphous quartz (pq) to the specularite suggests that the specularite represents an earlier partial replacement of hedenbergite. Plain light. 

B. PHOTOMICROGRAPH OF METAMORPHIC LIMESTONE FROM A BED IN TilE SHALE MEMBER OF THE SANDIA FORMATION EAST OF 

GRANITE MOUNTAIN. 

The rock consists of interlocking platy calcite crystals (c) and a fine interstitial intergrowth of chlorite, serpentine, and epidote (cis e) with some quartz (q) and a few garnets (g). 

Crossed nicols. 
DEPOSITS FORMED AT HIGH TEMPERATURES 105'-

The ore bodies of the district are classified in this 

report mainly according to origin-primary, or hypo-

. gene, and secondary, or supergene. The primary ores 

are further classified according to the relative tempera-

,tures at which they were formed-high temperature or 

hypothermal and · moderate temperature or mesothermal. The moderate-temperature class evidently 

has a great temperature range. It is conveniently subdivided into a "hotter" and a "cooler" grm1p, which are 

distinguishable by their mineral compositions and have 

differed markedly in their relative commercial importance. The "cooler" group has recently been 

recognized by G~aton as a. distinct class and was designated by the tern1 "leptotherma]" (formed at mild 

temperature) .

71 No low-temperature or epithermal 

ore deposits have been recognized within the district, 

but certain minerals are believed to have been deposited 

at relatively low temperature by solutions that had 

already deposited ore at moderate temperature. The 

minerals formed at these different temperatures are 

shown in the table on page 88. 

The ore bodies thus classified may be further dasf:)ified according to form, but this further classification is 

of interest mainly in connection with the moderate- . 

temperature class, which includes disseminated sulphide 

deposits in monzonite, in veins mainly within or along 

the margins of igneous rock and argillite, and in replacement deposits, mostly in limestone. Nearly all 

the output of the district has come from replacement 

deposits in limestone. A few productive veins have 

been mined along or close by major faults that separate 

limestone from Tertiary (?) granite' or pre-Cambrian 

argillite. The disseminated sulphide deposits are of 

little or no prospective value. 

The ores of the primary deposits may be classified 

· according to their dominant metal contents, but such 

a subdivision is worth wh~le only for the "moderatetemperature" ores. The secondary ores are divided 

first into oxidized and sulphide ores and subdivided 

according to dominant metal content. 

DEPOSITS FORMED AT HIGH TEMPERATURES 

Ores formed exclusively at high temperature in the 

Magdalena district are of no economic interest except 

insofar as they are associated with ores formed at moderate temperatures and thereby complicate -mining and 

milling. The highest-temperature deposits, as may be 

surmised, are mostly limited to the immediate vicinity 

of the centers of igneous intrusion-the stocks of monzonite and Tertiary (?) granite; a few that have been 

found remote from the exposed stocks suggest the 

presence of concealed stocks below the present surface. 

The character of the high-temperature deposits differs 

considerably from place to place. They are mainly ex71 Graton, L. C., The depth-zones in ore deposition : Econ. Geology, 

vol. 28, pp. 513-5•55, 1933. 

200889-42-8 

pressed at the surface by the conversion of the original 

blue, gray, or black limestones into white crystalline 

limestol!e or into white, ·green, or brown aggregates of 

silicate , minerals, principally wollastonite, diopside, 

garnet, and hedenbergite and the conversion of green 

argillite and black shale into dense green to gray hornfels; but these altered rocks afford no definite clue 

to the positions of ore bodies. Hedenbergite and the 

andradite variety of garnet are more closely associated 

with ore zones than the other silicate minerals. The 

significance of the silicate minerals in connection with 

rock alteration and origin of ores is considered on 

pages 50 and 51. , 

A later stage of deposition at high temperature is 

expressed by the specularite-magnetite masses, none of 

which are sufficiently larg~ to form commercial bodies 

of iron ore under present local conditions. These minerals have beeh found in the mines just south of the 

Nitt monzonite stock, at the Hardscrabble mine, the 

Linchburg tunnel, two prospect dumps in the Granite 

Mountain area, and in surface debris on the Medley 

Ranch to the northwest of J\tfagdalena Mountain, where 

iron ore is s~id to have been obtained as flux for the old 

smelter at South Camp about 1882. The occurrences 

south o.f the Nitt stock, however, are intimately associated with suLphides in the largest o~e bodies of the 

district. The specularite-magnetite masses were evidently formed by solutions that followed fissures and 

spread along adjacent bedding planes, impregnating 

and replacing limestone, some of which had already 

been partly replaced by silicates. Some of the specularite-magneti.te masses are several feet in diameter, 

but most of them consist of layers only a foot · or two 

thick with considerable interlayered limestone that has 

recrystallized into platy calcite (pp. 102-103). These 

thin layers were formed along the main ore zone and 

its principal branches throughout the Nitt, most of the 

Graphic-Waldo, and at least the northern half of the 

Kelly mine, and redu~ed the amount of limestone that 

was later available for replacement by sulphide ores. 

The distribution of · specularite-magnetite masses and 

associated sulphide ores indicates that the ores of these 

mines were supplied from two locStl sources, one near 

the south contact of the Nitt stock and one at the intersection of the Kelly-Graphic fault and Kelly-Graphic 

cross fault. These sources will be considered in connection with structural discussions. 

The occurrence of specularite arid magnetite in the 

Linchburg tunnel, in the sout~ern pa.rt of the district, 

is of particular interest, as they are associated with 

hedenbergite and garnet and indicate a high-temperature group of minerals. The occurrence therefore implies another center of mineral deposition. along a 

major fault zone but remote from any exposed stock of 

monzonite or· Tertiary ( ? ) granite. Its discovery 

justifies the expectation of much more undeveloped 
106 MAGDALENA MINING DISTRICT, NEW MEXICO 

ore in the southern part of the district tha~ would 

otherwise have seemed possible. 

DEPOSITS FORMED AT MODERATE TEMPERATURES 

All the commercial deposits of the district and most 

of the minor deposits consist mainly or wholly of minerals that are characteristically formed at moderate 

temperatures, but they are divisible into two groups 

that represent the hotter and cooler parts of this range, 

or mesothermal and leptothermal as defined by Graton 

(see table, p. 88). The first group includes the more 

productive ore bodies, ·a few large quartz veins, and 

the immense jasperoid deposits that have replaced 

limestone; the second group includes relatively small 

ore bodies in the outlying parts of the district. Each 

group could be further divided according to mineral 

composition, form, and wall rock, but to do so would 

give undue prominence to features of little practical 

significance. It will suffice here to give first a brief 

separate description of a few large barren quartz veins 

in igneous rock that attract attention because of their 

size and then to consider the outstanding features of 

the productive ore bodies. 

LARGE BARREN QUARTZ VEINS IN IGNEOUS ROCK 

Large quartz veins in igneous rock have been found 

at two places in the district : in pre-Cambrian felsite 

south of the Hardscrabble mine on the west slope of the 

l\1agdalena Range and in the Tertiary ( ~) monzonite 

and rhyolite porphyry on the low . hill a mile south 

of Granite Mountain. They cannot be definitely correlated with other mineral deposits in the district, but 

it seems most consistent to regard them as deposits 

formed during an early stage _of the period of ore 

deposition but at a moderate temperature. 

The large white vein in the Magdalena Range is a 

distinct topographic feature, which parallels the. contact 

between felsite and argillite for 2,300 feet. A short 

thick vein lies 250 feet northwest of the southwest end 

of the large vein in steplike arrangement. No proof 

that it is a faulted part of the large vein could be 

found. The large vein is 25 feet thick at the crest of 

the range. It strikes N. 70° E. and dips steeply southsoutheast. It ranges in character from a white . solid 

granular mass, completely replacing felsite and crisscrossed and bordered by a network of milky quartz 

veinlets, to vuggy masses lined with quartz crystals 

an inch or more long. Incomplete replacement of the 

felsite is represented by a porous mass of quartz 

crystals coated with films of sericite and accompanied 

by oxidized pyrite and green and black stains of copper 

and manganese minerals. 

The large vein is cut by the same sets. of minor fractures that cut the felsite, and midway down the west 

slope of the range it is slightly offset by a short fault 

of north-northwest trend that also offsets the contact 

between felsite and argillite but does not cross the contact bet~een argillit~ and Tertiary ( ~) granite. This 

evidence suggests that the vein is older than the granite 

and could even be of pre~Cambr:ian age; but no similar 

veins have been found in the pre-Cambrian rocks of the ' 

district, and the trend of the vein is similar to that of 

some of the transverse faults that cut the Carboniferous 

rocks. Both the Tertiary ( ~) granite and the vein are 

cut by a white rhyolite dike, one of a linear group, and 

it may be that the minor fault that cuts the vein is a 

l,ocal member of a relatively new or reopened fissure 

zone along which the dikes were intruded. 

Prospects along the vein are located at places where 

the vein has been disturbed. At the crest of the range 

it is crossed by a small barite-quartz-sulphide vein of 

northerly trend and in this respect is similar to the 

immense mass of jasperoid that has replaced Kelly 

limestone and pre-Cambrian argillite in the southern 

part of the district. Near its southwest end the large 

vein is crosscut by a shear zone of northwesterly trend 

that has been followed by an incline. A prospect dump 

at the short vein nearby shows rusty honeycombed 

·quartz but no evidence of ore minerals, and it could 

not be determined whether this quartz was a part of 

the original vein or of a minor vein that cuts the 

original vein. Structural evidence, therefore, regarding the age of the two veins in felsite is inconclusive. 

There is no proof that they are not pre-Cambrian, but 

they may be of the same age as the jasperoid that was 

forme9- after the main period of vertical faulting in 

Tertiary ( ~) time (p. 53) . 

The large barren vein on the hill south of Granite 

Mountain is similar in general character to the veins 

in felsite just" d,escribed. This vein, however, cuts 

rhyolite porphyry and monzonite and is apparently cut 

by a lamprophyre dike, although its intersection with 

the dike is concealed by debris. No contact between 

the vein and any white rhyolite dike is exposed. The 

age of this vein is, therefore, determined as younger 

than that of n1onzonite and probably older than that of 

lamprophyre. In this respect, it is similar to the 

granophyre that has replaced Tertiary ( ~) sandstone 

(p. 41). The granophyre may be regarded as a product 

of replacement at high temperature and the quartz vein 

one of replacement at a temperature too low to permit 

the formation of granophyre. 

This interpretation is paralleled by that of the .origin · 

of jasperoid in the sopthern part of the district (p. 53). 

The jasperoid was deposited at the same general time 

as the high-temperature silicates that replaced limestone but at a temperature too low to permit the 

formation of those silicates. 

SULPHIDE DEPOSITS 

Sulphide deposits that represent the higher part of 

ihe moderate-temperature range include the large re-
DEPOSITS FORMED AT MODERATE TEMPE'RATURES 107 

placement deposits of zinc-lead and ~opper ores in the 

Kelly limestone that have accounted for the greater 

part of the output of the district, small depo'sits of 

similar ore in adjacent parts of the Sandia and Madera 

formations, and noncommercial pyritic copper deposits 

in monzonite. 

With few exceptions, these deposits lie along the 

main ore zone of the district, which extends southsoutheast through the Nitt, Graphic-Waldo, and Kelly 

mines (pl. 30) and continues beyond the south end of 

the district. The ores are represented along the main 

ore zone in the three mines named and in the Linchburg tunnel. Even material consisting mainly of 

specularite and magnetite is commonly so much impregnated with sulphide as to be classed as commercial 

sulphide ore of mill grade. The main zone may also be . 

regarded as continuing northward under Hardscrabble 

Valley through . the mineralized part of the Nitt monzonite. stock. The ·exceptions include the deposits in 

the west ore zone along the "\V aldo fault and ore shoots 

of the Hardscrabble mine which lie along a relatively 

short fissure zone in Tertiary ( ? ) granite northeast of 

the Nitt stock. 

Ores that represent the cooler or leptothermal part of 

the moderate-temperature range are found throughout 

the rest of the district. They include all of the known 

deposits in the main zone south of the Kelly mine except that in the Linchburg tunnel and !perhaps that in 

a poorly exposed vein near the breast of the ~Iistletoe 

or Gordon tunnel, and they may be grouped as follows: 

all the known deposits along the Germany, AmbrosiaTip Top, and Black Cloud zones, which may be regarded as easterii ~ranches of the main zone ; the minor 

zones in volcanic rock, most or all of which are western 

branches of the main zone; the Anchor vein, which may 

well be connected with the Hardscrabble deposit of 

hotter mesothermal ore; and the deposits in the Granite 

Mountain area and those north of Magdalena Mountain, which are too scattered and inadequately exposed 

to be correlated with any distinct zones. 

The large replacement bodies lie mainly along minor 

faults ·and fissures, which as a group may be regarded 

as auxiliary members of the main fault zone. Some 

of the minor vertical to steeply west-dipping fissures 

in the Kelly mine are dearly branches or spurs 

that diverge north-northwestward from the KellyGraphic ault, which forms the east wall of the 

ore shoot. The Brown fault, along which the 

Kelly ore shoot attains its greatest length,. has a similar 

divergent position but is terminated or interrupted by 

minor cross faults near the Kelly tunnel and does not 

actually join the Kelly-Graphic fault. The main ore 

shoot in the Graphic-Waldo and Nitt mines lies along 

minor faults and fissures of northwest strike and northeast dip, but the intersections of these faults with the 

west-dipping Kelly limestone have north-northwest 

trends and pitches. The principal of these minor 

faults pass upward into small "rolls" or monoclinal 

folds in the basal shale bed of the Sandia formation. 

The movement along these faults, as shown on page 71, 

caused auxiliary movement along bedding faults, 

especially at the top, middle, and probably the base of 

the Kelly limestone, which thus became especially 

permeable to ore-forming solutions. 

Transverse faults, mostly of northeast strike and 

southeast dip, but in part of northwest strike and 

northeast dip, have also exerted some control over the 

form and distribution of the ore shoots. In the 

Graphic-Waldo mine .they have permitted a widening 

of the larger ore shoots at or near their intersections 

with the longitudinal faults, and these intersections 

have also 'allowed solutions to rise into the Sandia formation and form small shoots that have been mined in 

its lower quartzite and lower limestone members. The 

transverse-faults, though formed mainly before ore deposition, have also caused a few apparent offsets in the 

ore shoots that had replaced the previously offset !parts 

of limestone beds. They appear to have been especially 

influential in the southern part of the Graphic-Waldo 

mine and to have serv:ed as connecting links between 

the main and eastern ore shoots; but most of the stopes 

there ~re so old and filled that data for a complete 

picture of them were not obtainable. ~1inor transverse 

faults in the Kelly mine have played similar parts. 

The largest of the transverse faults associated with 

these ores is the Kelly-Graphic cross fault (see pl. 20). 

It forms an abrupt north end to the Kelly ore body, 

which was being mined in 1916 and from which a veinlet extends along the fault on level 6. · This veinlet is 

somewhat shattered, indicating a small amount of postmineral movement along the fault; but the main ore 

body showed little effect of such movement; furthermore, the ore shoots found on the north side of the fault 

are small and irregular and are clearly not offset continuations of the main Kelly ore body. Practically all 

the movement along this fault, therefore, took place 

before ore deposition. Besides the difference in form, 

the- presence of barite in the small ore shoots north of 

the fault suggests a gradation into the ·cooler mesothermal or leptothermal ores, whereas the large Kelly 

ore body, with its associated silicates, specularite, and 

magnetite, suggests that the broken ground near the 

intersection. of the longitudinal Kelly-Graphic fault 

and the Kelly-Graphic cross fault was a local center 

of ore deposition distinct from that near the boundary 

between the Nitt and Graphic-WaJdo mines. The small 

incompletely mapped ore shoots of the Juanita mine 

bear the same relations to the Kelly center as do those 

in the southern part of the Graphic-Waldo mine to the 

Nitt-Graphic center. 

The west ore zone, along the 'Valdo fault, has been 

seen only where it is crossed by the Waldo tunnel. 
108 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

There it has the general structure of a vein in shattered ground along the fault that is bounded on the 

east by steeply dipping shale and limestone. South of 

the tunnel a nearly vertical pipe of sulphide ore was 

found at the intersection of a member of this fault 

zone and a fault or fissure of northwest trend. The 

west zone has also been explored in the Kelly mine, 

but we have very little information about it. 

As the ore in the Linchburg tunnel has been mainly 

developed since our visit, the only specific remark that 

we can make about it is that it is walled on the east 

by the Young America fault, which corresponds to the 

Kelly-Graphic fault in the Kelly mine, although the 

argillite or "greenstone" in the east wall of the fault 

is impregnated with ore minerals to a minor degree. 

In the Hardscrabble mine, which is in an elongate 

block of Kelly limestone enclosed in Tertiary ( ~ ) 

granite, the largest ore shoots are controlled by a set 

of fissures intersecting the bedding nearly at right 

angles. The ore extends from the limestone even into 

the underlying granite, which it has replaced along 

a network of fissures. 

The Kelly limestone as a whole is the principal ore 

stratum in the district, but it is divisible into three or 

four minor units (fig. 1), which locally coalesce. The 

lowest is the "pinto" bed, which lies along or just above 

the impure basal beds and is overlain by fine-grained 

to dense beds, locally including the "marbleized lime" 

of the Kelly mine and the "lower silver pipe". Above 

the "lower silver pipe" the next u·nit is the coarsegrained or "lower crystalline" limestone, which underlies the main "silver pipe" bed. Similar coarse-grained 

limestone just above the main ''silver pipe" forms a 

third unit in places, but it is less extensively mineralized than the coarse-grained limestone that lies near 

the top of the formation and is capped either by a 

thin "upper silver pipe" b~d or by the shale at the base 

of the Sandia formation. In the Nitt and northern 

part of the Graphic-Waldo mine these beds are thoroughly connected, especially along the local faults that 

have shattered the "silver pipe" bed and even brought 

the beds below and above it into contact with each 

other. The "silver pipe" bed a very short distance 

from the faults, however, has resisted replacement almost entirely. In the Kelly mine the beds below the 

main "silver pipe" bed have probably been more productive than those above it, but a considerable part of 

their output has been oxidized zinc ore, which replaced 

limestone that had not been reached by the original 

sulphide ores; furthermore the upper beds have been 

eroded from the southern part of the Kelly mine. 

Strata that have been productive above the Kelly 

limestone include the following: a quartzite bed just 

above the base of the Sandia formation in the old part 

of the Graphic-Waldo mine, where movement along 

intersecting faults had made it unusually permeable; 

the lower limestone member of the Sandia formation 

in which ore deposition was also favored by intersecting faults above and between the pri11:cipal ore shoots 

of the Graphic-Waldo mine; a limestone bed in the 

shale member ·of the Sandia formation, opened by the 

Cimarron tunnel near the intersection of the KellyGraphic cross fault and a probable branch of the 

'longitudinal Kelly-Graphic fault; massive Madera 

limestone in the Vindicator mine made accessible by 

the longitudinal Vindicator fault and cross faults south 

of the shaft. These Stnd other beds may contain ore 

shoots elsewhere, where structural conditions and proximity to ore zones are favorable; but in the light of past 

experience their contribution to the output of the district . will be small, and whether or not they are 

workable at a profit is questionable. 

HOTTER MESOTHERMAL ORES 

The character of the original sulphide ores will be 

considered here because of its bearing on the origin 

of the ores and on future exploration and development. 

The oxidized and enriched sulphide ores are more conveniently treated after the origin of the original 

sulphide ores has been considered. 

The original ores of the hotter mesothermal group 

are mixtures of pyrite, sphalerite, galena, and. chalcopyrite, with some or all of the following minerals in 

small to considerable amounts : specularite, magnetite, 

silicates, quartz, calcite, and manganiferous siderite. 

They are divisible according to their principal mine~al 

or metal content into the following groups: (1) Pyritic 

or iron ores, (2) chalcopyrite-pyrite or copper ores, 

(3) sphalerite or zinc ores, (4) galena or lead ores, 

( 5) mixed sulphide ores. The first two and last thre.e 

of these groups are conveniently considered together. 

IRON AND COPPER (PYRITIC) ORES 

Massive, coarse-grained pyrite has replaced a considerable part of the Kelly limestone in the Nitt mine 

and the northernmost part of the main ore shoot in the 

Graphic-Waldo mine. It is accompanied · by minor 

amounts of quartz and chlorite, but much of it appears at first glance to be essentially pure pyrite. The 

massive pyrite . contains only negligible quantities of 

silver or gold. It could be regarded as a small reserve 

for the manufacture of sulphuric acid, but as much 

larger deposits in other districts are nearer markets, it 

must be regarded as of not even potential value under 

ordinary conditions. 

The pyritic ore continues southward along the basal 

part of the Kelly limestone throughout the sulphide 

zone of the Graphic-Waldo mine, where it contains 

sufficient interstitial chalcopyrite to become a copper 

ore. Its, copper content, however, has been appreciably 

increased in places by chalcocite, covellite, and mala-
• 

D>EPOSITS FORMED AT MODERATE TEMPE!RATURES 109 

chite. Available records of shipments show its copper 

content to range from 1.7 to 9.4 percent and its silver 

content from 2.0 to 5.6 ounces to the ton. It contains 

considerable quartz, chlorite, and iron oxides, which 

are locally so abundant as to be left as pillars in the 

stopes. It also grades into mixed sulphide and 

sphalerite ores. 

The limitation of this pyritic copper ore to the basal 

,part of the l(elly limestone is remarkable ~nd not satisfactorily explained. The distribution of oxidized 

copper ore implies that this pyritic ore was originally 

continuous in the same bed through much of the 

Graphic-Waldo mine and was present in parts of the 

Kelly mine also. A simple explanation would be that 

the solutions depositing this ore rose during an early 

stage and permeated the lowest replaceable bed; but 

it is noteworthy that the still earlier solutions of the 

silicate and specularite-magnetite stages, as well as 

the later solutions of the sulphide stages, replaced the 

upper part of the Kelly limestone. If temporary obstructions along the feeding fissures deflected the 

pyritic copper solutions into the lowest limestone beds, 

it is remarkable that they were effective at the same 

horizon and at the same time throughout the GraphicWaldo and at least part of the Kelly ground. The 

close association of the pyritic copper ore with the 

siliceous basal beds of the limestone and the siliceous 

argillite that forms the footwall of the pyritic copper 

shoot suggests that these siliceous rocks exerted some 

influence on the deposition of this particular ore, but 

there is no apparent reason why siliceous rocks should 

have any greater influence than those of pure limestone. 

It is commonly recognized in many districts that 

pyrite-chalcopyrite ore represents an . earlier stage of 

deposition than sphalerite and galena ores. The 

chalcopyrite, however, is interstitial to pyrite, and, in 

the Magdalena ores at least, no evidence has been found 

to show whether it was deposited by the same solution that deposited the pyrite or by a distinctly later 

solution that permeated not only the pyritic ore but 

sphalerite and galena ore as well. According to the 

second suggestion, the greater though unevenly distributed quantity of chalcopyrite in the pyritic o're 

could be attributed to the precipitating power of 

pyrite, whose iron and sulphur would react with 

copper in solution and produce chalcopyrite. If this 

were accepted, all the chalcopyrite in the deposits could 

be attributed to one stage which followed that of 

sphalerite and p~l\haps that of galena, but there is no 

reason why chalcopyrite could not have been formed at 

more than one stage. 

The relative concentration of chalcocite and other 

copper minerals as coatings on chalcopyrite and pyrite 

and as linings of cavities and fractures will be 

considered on page 122. 

ZINO BLENDE, GALENA, AND MIXED SULPHIDE ORES 

Zinc blende ores-those that contain sufficient zinc 

to be shipped to smelters or that yield only zinc concentrates in appreciable quantity through millinghave been the most abundant in the district, and their 

highest grades have been mined throughout the sulphide zones of the larger mines. They have not been 

mapped separately from zinc-lead sulphide ores, into 

· which they .grade, and the stopes shown on mine maps 

include both kinds, as well as small amounts of galena 

ores. They have been found at all horizons of' ths 

· l(elly limestone, and their quantity at any one place, 

as well as their mineral composition, has depended on 

the degree of fracturing and permeability and on the 

extent to which the limestone had already been replaced by ·silicates, quartz, iron oxides, and py:ite. 

Surprisingly large irregular masses have been mined 

in the Hardscrabble and Nitt mines and in the northern part of the Graphic-Waldo mine, although iron · 

oxides and pyrite are the most abundant minerals in 

all three places. Small shoots are present here and 

there in the pyritic copper ores. Elsewhere they are 

the dominant ores. Their composition varies greatly. 

Zinc ores shipped crude have contained from' 19.7 to 

37.7 percent of zinc. They consist of ferroan zinc 

blende with small amounts of pyrite, galena, chalcopyrite, quartz, and calcite or other carbonate.. Milling ores have contained from 19.1 to 15.3 percent of 

zinc with correspondingly larger amounts of the other 

sulphides and especially of specularite, magnetite, and 

gangue minerals. 

Ores in the hotter mesothermal zone that contain 

sufficient galena to be shipped directly as lead sulphide 

ores are scarce and have been seen' in commercial quantity only at the transition between the sulphide and 

oxidized zones, where large quantities of zinc blende 

and smaller quantities of chalcopyrite and pyrite have 

been removed. Shipments of lead ore have contained 

from 15 to 20 percent of lead and from 3.4 to 5.3 

ounces of silver to the ton. In the original sulphide 

deposits galena ore is co~fined to small lenticular 

bodies and streaks in which other minerals are comparatively scarce. These small bodies for the most 

part represent lim~stone that had escaped appreciable 

replacement during the zinc blende and earlier 

stages of deposition but some repre~ent deposition 

along bedding planes or other openings. Galena 

for the most part is disseminated in singl'e grains 

and small aggregates or streaks through zinc blende 

and mixed sulphide ores. In some of these ores 

it can be largely separated by milling, but in othevs 

zinc blende and galena are so fine grained and intimately mixed that separation has been impractical 

a~d the ore has been shipped crude for the direct 

manufacture of zinc-lead oxide pigment. Shipments 
110 l\1AGDALENA MINING DIStl'RICT, NEW MEXICO 

of crude zinc-lead sulphide ore have contained frmn 

14 to 30 percent of zinc and 5 to 15 percent of lead. 

Chalcopyrite has formed distinct streaks to a smaller 

extent than galena and is a smaller visible constituent 

of the mixed sulphide ores; but, as shown on pages 

94-95, minute to microscopic grains of it are present 

in the zinc blende, and are attributed by us to reaction 

between copper in solution and iron and sulphur in 

zinc blende, similar to that between solution and pyrite 

that produced pyritic copper ores. 

The contents of silver and gold in these sulphide 

ores are too small to warrant suggestions as to exact 

n1odes of occurrence. In this respect the mixed sulphide ores of Magdalena are similar to those in other 

districts, where the silver and gold have been thought 

to be partly in solid solution in galena and partly in 

submicroscopic grains of native gold and silver or of 

argentite or some other silver sulphid~. Practically 

no assays of the zinc and zinc-lead ores of Magdalena 

show more than 0.02 ounce of gold and 4 ounces of 

silver to the ton. 

COOLER MESOTHERMAL (LEPTOTHERMAL) ORES 

The cooler mesothermal or leptothermal ores include 

not only replacement deposits in limestone similar in 

structural relations to replacement deposits already 

described, but also vein deposits in other kinds of rock. 

They contain the same sulphide's as the hotter mesothermal ores, but pyrite is subordinate, and the zinc 

blende is resinous and of a lighter-brown or even yellow 

color and evidently lower in iron. The principal 

gangue minerals are quartz with conspicuous amounts 

of barite and small commonly inconspicuous quantities 

of fluorite. Calcite in mino~ quantity lines fractures 

or cavities in the form of long pointed crystals or 

scalenohedrons (dog-tooth spar). Replacement quartz 

is more prevalent than in the hotter mesothermal ores. 

It had replaced so much of the limestone before the 

arrival of sulphide solutions that the sulphide ore 

shoots are correspondingly restricted and commonly lie 

beneath a roof or between walls of replacement quartz. 

Some small shoots, which have replaced remnants of 

limestone that had escaped earlier replacement, are entirely surrounded by quartz. The quartz-barite aggregates, which were later than the early replacement 

quartz but earlier than the sulphides, were deposited as 

open-textured masses. Into these the sulphides were 

introduced, forming comparatively low grade ore. 

Because of these features, as well as the undesirability 

of barite in smelting, these ores and their oxidized 

equivalents have been less profitable to work; and, 

notwithstanding their. wide distribution, they have contributed only a minor part of the output of the district. 

These ores may originally have nearly or quite all 

been mixed sulphides, their prevailing ratio of galena 

to zinc blende may have been relatively high, and their 1 

copper content may have been high enough in a few 

places to give them commercial value as lead-copper 

ores; but, owing to their shallow positions, they have 

been for the most part so thoroughly oxidized that 

galena is the only sulphide left in sufficient quantity to 

constitute sulphide ore. Some of this galena, for example in the Young America and Enterprise claims, is 

so massive and free from cavities that it no doubt 

formed small shoots of high-grade lead sulphide even 

in the original ore. 

Shipments of crude lead sulphide ore of this class 

have ordinarily ranged from 0.02 to 0.04 ounce of gold 

and 2.3 to 4.5 ounces of silver to the ton, 0.2 to 0.8 percent of copper, and 12 to 33 percent of lead. One lot 

of 7 tons contained 47 percent of lead and 8 ounces of 

silver to the ton; and one of 427 tons credited to the 

Germany mine averaged 0.28 ounce of gold . and .28.7 

ounces of silver to the ton, about 2 percent of copper, 

and about 10 percent of lead. The only definitely recorded shipments of crude copper sulphide ore-13 tons 

from the Black Cloud mine-contained 11.7 ounces of 

silver to the ton, about 7 percent of copper, and 1.5 

percent of lead. 

The veins in volcanic and other siliceous rocks are 

preyailingly small and of such low grade that few prospects have attained any considerable depth. So far as 

known only one-the Iron Mask at South Camp-was 

ever developed into a mine. It was worked about 1880 

but has contributed only negligible quantities of ore 

since then. The ore, as shown on pages 95 and 98 

· had undergone some sulphide enrichment and therefore 

contained considerable chalcocite and argentite ( ~) 

along with oxidation products. The original conlposition of the ore was not definitely determinable. Small 

shipments fron1 the Morning Star claim, just north of 

the Iron Mask, were made in 1934-36. 

DEPOSITS FORMED AT LOW TEMPERATURES 

As shown in the table on page 88, no ore minerals 

are thought to have been formed at low temperatures; 

at least, they cannot be distinguished from those 

formed at moderate temperatures. The long pointed 

crystals or scalenohedrons of calcite, which were deposited later than the ore minera]s, may have been 

formed in part at low temperature, especially where 

they are not closely associated with ore minerals. The 

only other minerals in the district that can be consistently classed as low-temperature minerals are the 

chalcedony, celadonite, and n1ontmorillonite ( ~), small 

amounts of which are present in altered andesite in 

the southern part of the district (see p. 55). These 

minerals are rather far from any zone of intense 

mineralization, and they may be attributed either to 

cooled, spent, ore-forming solutions or to emanations that permeated the and~site immediately after its 

eruption. 
MAGDALENA MINING DISTRICT, NEW MEXICO 111 

GENESIS OF ORIGINAL (HYPOGENE) ORES 

Tentative opinions regarding the source of the 

original ore-forming solutions, previously expressed 

by Gordon 72 and Ringlund 73 afteil' reconnaissance 

work, have been that the ores were most clearly related 

to the rhyolite porphyry, formerly called "granite 

porphyry,'' along the west base of the range. Our 

work, however, has shown that the major period of 

faulting, as well as the intrusions of the monzonite 

and Tertiary ( ? ) granite sto.cks and the lamprophyre 

and white rhyolite dikes, all took place after the intrusion of the rhyolite porphyry and before ore deposition. Some of those interested in the district in 1915 

and 1916 thought that the ores were derived from the 

"faulting dikes': of lamprophyre with which they are 

so closely associated in the Kelly mine; but the fissures 

through which the ores were introduced only coincide 

in part with the dikes, whereas some fissures cross or 

slightly offset the dikes and others are far away from 

them. The fact that these dikes were intruded after 

the monzonite stocks also precludes any suggestion that 

the ore-forming solutions were emanations expelled 

from the crystallizing main monozonitic stocks, and 

the only tenable idea that remains is that the oreforming solutions were derived from a deep sourcepresumably the same as that from which the Tertiary ( ? ) intrusive rocks had already been derivedand rose along the most persistent fault zones, from 

which they spread wherever there was opportunity. 

That n1ineral deposition took place during several 

stages, mainly within the ranges of high and moderate 

temperatures, has already been implied. Minerals 

.- formed by rock alter~tion during these stages have 

already been considered at some length (pp. 4 7-55) , and 

their correlation with different stages is only summarized here. The earlier stages, especially, are believed to be represented by minerals indicative of high 

temperatures near the sources of supply and moderatetemperature farther from the sources; but no productive deposits were formed during these stages. The 

ore-forming stages are believed to have taken place at 

moderate temperatures throughout the district, but 

they also are represented by relatively high temperature or meso thermal deposits near sources of ·supply 

and lower-temperature or leptothermal deposits elsewhere. Low-tem,'Perature deposits, which are represented within the district by only a few gangue minerals, are present over a large area, mostly far from 

centers of. mineralization and are only considered incidentally. As the different stages of deposition have 

been most clearly defined by processes that took place 

in limestone, these processes will be considered first. 

72 Gordon, c~ H., in Lindgren, Waldemar, Graton, L. C., and Gordon, 

C. H., Ore deposits of New Mexico : U. S. Geol. Survey Prof. Paper 68, 

p. 254, 1910. 73 Ringlund, Soren, Geology and ore deposits of the Magdalena district, 

unpublished thesis, New Mexico School of Mines, 1913. 

PROCESSES IN LIMESTONE 

EARLY SILICATE-FORMINGSTAGES 

The earliest stage of mineral deposition, as shown 

on pages 49, 50, evidently accompanied the later stages 

of crystallization of the intrusive stocks. It is represented by such minerals as tourmaline, wollastonite, 

diopside, ' and garnet (grossularite), particularly 

within 300 feet of the monzonite contact at Oak 

Spring. These minerals are found mainly in the Kelly 

limestone, but they are not restricted to tp.e main ore 

zones ; in fact, they are extremely scarce or absent 

there. They were evidently formed by solutions that 

escaped through fractures in the newly crystallized 

marginal parts of the stocks and permeated the adjoining limestone along fractures and bedding !planes. 

. Beyond the limits of their deposition, the limestones 

of · the Kelly, Sandia, and Madera formations were 

bleached and recrystallized for as much as 1,000 feet 

from the contact~ 

The second stage, represented by hedenbergite, gar-

. net (andradite), and platy calcite, took place after 

the consolidation and profound fracturing of the 

stocks. It is most conspicuously represented along the 

·main ore zones of the Graphic-Waldo and Kelly mines 

and the Linchburg tunnel, and its solutions rose along 

reopened faults for moderate to long distances from 

sources that cannot be correlated ·with any exposed 

parts of intrusive stocks, although the stocks and solutions doubtless had the same general deep source. As 

neither hedenbergite nor andradite nor platy calcite 

have been recognized within monzonite, the effects of 

this second stage on monzonite has not been determined, although the Nitt monzonite stock was fractured by the recurrent movements along the fault zone 

in which these minerals were formed in the GraphicWaldo mine. 

The solutions of the first two stages reached per-

. meable lim~~to~e at temperatures sufficiently high for 

silicates to form. However, where the same solutions 

traveled so far before reaching permeable limestone 

that they had cooled below the stability ranges of tho~e 

silicates, they replaced the limestone with fineMgrained 

quartz or jasperoid, which is very extensive in the 

southern part of the district and also near Granite 

Mountain.. The large quartz veins in felsite, rhyolite, 

porphyry, and monzonite are more consistently assigned to one of these early stages than to any other. 

SPECULARITE-MAGNETITE STAGE 

Specularite, magnetite, and_ quartz are also regarded 

as high-temperature minerals and, like hede.nbergite, 

formed for the most part along the most productive ore 

zones. Small veins of magnetite and quartz also formed 

within the monzonite. • The solutions of this stage 

reached the Kelly limestone, even near intrusive con-
112 MAGDALENA MINING DISfl'RICT, NEW MEXICO 

tacts, at temperatures too low for the formation of calcium-iron silicates but too high for iron to combine with 

sulphur to form pyrite. The quartz was deposited 

partly in close association with the specularite and magnetite and partly in fine-grained replacement masses that 

are not distinguishable from j asperoid of the earlier 

stages unless in their closer association with ore bodies. 

Deposits belonging to this stage have not been recognized a way from the centers of mineralization. 

Any or all of these stages may be represented by 

epidote and perhaps chlorite, particularly in the less 

pure limestones, shales, quartzites, and igneous rocks; 

but epidote is so widely distributed, qoth near and far 

from intrusive contacts and ore zones, that it is of 

little or no value in the recognition of different stage~ 

of mineral deposition. It was doubtless formed during stages of moderate as well as high temperature. 

The restricted distribution of specularite and magnetite throws more light on centers of mineralization 

than the silicates. The abundance of these iron oxides 

in the lower, northern part of the Graphic-Waldo mine . 

implies that solutions rose along the Roll fault (p. 127) 

near its junction with the Nitt monzonite stock and 

spread upward to the south and east throughout much 

of the Graphic-Waldo ground before their temperature fell below the stability range of the iron oxides. 

Little or no magnetite was ·deposited in the extreme 

southern part of the Graphic-Waldo ground so far 

as known, but evidence there is obscured by thorough 

oxidation and the inaccessibility of most of the 

workings. 

The prominence of ·specularite and magnetite in the 

northern half of the Kelly mine, together with -local 

structural conditions, imply that solutions rose through 

fractured ground at the intersection of the KellyGraphic fault and the Kelly-Graphic cross fault. The 

south limit of specularite and magnetite in this mine 

also is obscured by oxidation and the inaccessibility 

of old stapes, but no trace of these minerals has been 

found in the southernmost part of the mine or in the 

Juanita mine, farther south. 

The specularite in the Linchburg tunnel implies a 

third center of mineralization in the vicinity, but too 

little is known of the extent of the specularite to 

indicate the approximate position of the center or to 

· correlate it with junctions of longitudinal and cross 

faults. It does show, however, that the distribution 

and zonal relations of ores are not to be correlated 

with exposed intrusive stocks but with places along 

major fault zones where_ circulation from great depth 

was most favored. As the pre-Cambrian argillite, 

gabbro, and granite had little reacting power with the 

rising solutions during this stage, deposition did not 

take place in appreciable quantity until the solutions 

reached the Kelly limestone. 

Occurrences of specularite and magnetite in the 

Hardscrabble mine and in the areas east of Granite 

Mountain and northwest of Magdalena Mountain 

imply other centers of mineralization. That in the 

Hardscrabble mine is along a fault, but available 

information from. a study of the debris-covered surfaces elsewhere is insufficient to delimit the extent of· 

other occurrences or their relation to faults. Still 

other centers of mineralization may be present-for 

example near the north boundary of the Nitt stock in 

Hardscrabble Valley; but they are not represented by 

high-temperature minerals and must be inferred from 

evidence presented elsewhere (p. 164). 

ORE-FORMING STAGES 

The ore-forming stages are represented by the 

sulphides pyrite, sphalerite, galena, and chalcopyrite. 

Minor local disturbances may have fractured the hightemperature n1inerals before the deposition of any 

appreciable quantities of sulphides, which characterize the ore-forming stage, but no evidence of 

pronounced fracturing or faulting between the specularite-magnetite and sulphide stages has been observed;. on the other hand, the relation of pyrite to 

specul.arite indicates a gradational change. Deposition 

of sulphides may b!3 conveniently regarded as having 

taken place in four general stages represented respectively by pyrite, zinc blende, galena, and chalcopyrite. ' 

The pyrite stage is clearly represented only around 

the Nitt-Graphic and Kelly centers of mineralization, 

as shown in the description of pyritic iron and copper 

ores on pages 108-109. The pyrite-forming solutions · 

followed the same general courses as those that had 

formed hedenbergite, specularite, and magnetite. 

They replaced the adjacent limestone, the recrystallized 

interstitial calcite in silicate masses, and to a slight 

extent the silicates. The pyrite, however, was less 

extensively deposited than the earlier minerals, 

especially in the upper parts of the Kelly limestone and 

along the minor fissures. 

The sphalerite stage, which followed, was the most 

extensive of any in the ore-forming group. Sphalerite 

was deposited along the ·same courses as the earlier 

minerals, replacing them to a slight degree and thoroughly replacing interstitial calcite and limestone that 

had previously escaped replacement. It enveloped the 

layers and bunches of specularite and earlier minerals 

that had not been previously enveloped by pyrite. The 

areal extent of replacement by sphalerite along and at 

right angles to the main feeding fissures is shown on 

plate 30 and in more detail on the maps that accompany 

mine descriptions. Sphalerite partly enveloped quartz 

and in places formed beneath a thin cap of quartz, 
GENE.SIS OF ORIGINAL (HYPOGENE:) ORES1 113 

especially along the top of the Kelly limestone. It 

also evidently replaced some quartz and dro:ve it along 

in solution so that it was redeposited as a rim or casing around the margins of the zinc-blende shoots. The 

sphalerite that was deposited relatively near.the centers 

of mineralization, where the solutions were more concentrated, had a comparatively high content of iron, 

a feature characteristic of several mining districts. It 

was deposited while barite, fluorite, and dolomite remained in solution. These minerals near the centers of 

mineralization are present only in very small quantity 

and in fractures and small cavities in the zinc blende. 

Farther from the centers of mineralization either 

through cooling or dilution of the solutions, barite and. 

fluorite were precipitated in advance of the sphalerite 

that had remained in solution. This· later-formed 

variety of sphalerit~ had a relatively low content of 

iron, and a little of it, which was pale yellow or nearly 

colorless, contained almost none. The solutions that 

deposited these outlying ores were evidently under less 

pressure than those near the centers of mineralization 

and had correspondingly less penetrating and replacing power. The Kelly limestone in the ou~lying areas, 

furthermore, had already been extensively replaced by 

masses of dense quartz or jasperoid, and the zinc solutions were in part dispersed through these masses, impregnating or replacing any remnants of limestone that 

they happened to reach. They also formed deposits 

beneath the large masses of jasperoid. Even the 

largest of these deposits was smaller and contained 

more gangue than those nearer the centers of 

mineralization. • 

Solutions rising from the southern or Linchburg 

center and escaping above· the Kelly limestone along 

the west wall of the Young America fault rose through 

the Sandia formation and formed the veinlike ore shoot 

of the Cavern and Grand ~edge mines, which lie between lower Madera limestone on the west and preCambrian argillite on the east. The solutions doubt-

] ess were deflected along the Kelly limestone and minor 

faults east of the Young America fault and formed 

the shallow deposits in . the Young America and 

adjacent claims. · 

Solutions similarly. escaping from the Nitt-Graphic 

and K~lly centers also formed outlying deposits, many 

of whiCh have doubtless been eroded. The solutions 

that rose mainly through these centers were evidently 

deflected in part along transverse faults below the 

present mine workings and into the faulted gFound 

east of the Germany fault, where only deposits 

characteristic of the outlying areas have been found. 

The relative order of the galena and chalcopyrite 

stages is not clear. In some places the chalcopyrite 

appears to have filled interstices among crystals of 

galena, and in others the opposite relation seems to 

hold. The solutions during both stages, however, -followed the usual courses, filling openings and replacing 

limestone or ealcite among the minerals already formed. 

The galena, introduced in greater quantity than chalcopyrite, was deposited wherever there was opportunity 

in relatively small quantity near the centers o£ mineralization and more abundantly beyond the range of the 

high-temperature minerals and the large deposits of 

pyrite. 

The chalcopyrite that clearly belongs to this late 

stage cannot be sharply distinguished from the interstitial ch~lcopyrite in the pyritic copper shoot (pp. 108-

109) and the minute specks of chalcopyrite in zinc blende 

(pp. 94-95). If the suggestion is accepted that the chalcopyrite specks grew by replacement of sphalerite, the 

chalcopyrite throughout the district was formed later 

than thel other sulphides with the possible exception of 

galena. It is therefore conceivable that all the chalcopyrite was deposited during one stage, that pyrite and 

sphalerite both favored its deposition through reaction 

with solutions, and that much of the copper, even 

though it was introduced Jate, was therefore deposited 

within shoots of pyrite and sphalerite near the centers 

of mineralization. Copper that was not deposited 

through these reactions was carried into the outlying 

parts of the ore zones but was nowhere deposited in · 

sufficient quantity to form an original sulphide ore 

body. This suggestion-that ·an the chalcopyrite in the 

district was introduced at.one stage-is·consistent with 

the facts regarding its occurrence in this district and · 

assumes a simple succession o~ depositional stages, each 

characterized by one metal; but. natural processes are 

not necessarily simple, and evidence in other districts 

that have similar ores may clearly indicate that copper 

was introduced during more than one stage. 

The precious metals, which are scarce in the original 

sulphide ores, were presumably deposited either in solid 

solution in the sulphide ore or as free gold and argentite. They impregnated the minerals already formed 

wherever they could but in quantities too minute to be 

detected with a microscope. 

Solutions nearly or quite depleted of their metal contents and containing mainly calcium carbonate-de:. 

rived from limestone that had been replaced by ore and 

other gangue minerals-eventually deposited calcite in 

its relatively ·low temperature or scalenohedral form, 

both near centers of mineralization and in the outlying . areas. This calcite may be accompanied by a little 

zinc blende and galena and also fine-grained pyrite 

and quartz. Any or all of these minerals may represent material that had been removed from deposits near 

centers of mineralization and redeposited. 

PROCESSES IN IGNEOUS ROCKS 

Although the igneous rocks of the district were subje?ted to attack by the same solutions that formed ores 
114 MAGDALENA MINING DISfrRICT, NEW ME.XICO 

in limestone and were extensively altered to different 

degrees, they were much less subject to replacement by 

ore and the different stages of ore deposition in them 

are not so clearly defined. In previous discussions 

(pp. 39, 47, 49), it was inferred that the feldspathic 

dikes and veins in monzonite and the tourmaline that 

lines fractures in monzonite and argillite could represent the same early stage of alteration as the wollastonite and other silicates in limestone and at least some 

of the secondary silicates in volcanic rocks close to the 

monzonite contact. No direct evidence for distinguishing a second stage, equivalent to the hedenbergite stage 

in limestone, was recognized; but the large quartz· veins 

in monzonite south of Granite Mountain may have been 

formed during this stage by solutions that had cooled 

below the stability range of such silicates as hedenbergite. (See p. 106.) V einlets of magnetite and 

quartz in monzonite suggests deposition on a small scale 

by the same solutions that replaced limestone with 

specularite and magnetite, and the main ore body of the 

Hardscrabble mine shows that these solutions also attacked the Tertiary ( ~) granite. This ore body consists of mixed sulphides associated with specularite and 

magnetite, which form a casing around the sulphides. 

It is similar in general composition to the hotter mesothermal ore bodies of the Graphic-Waldo and Kelly 

mines. It is mostly in the large block of Kelly limestone but extends downward into the granite, which it 

has replaced along a network of closely spaced fractures 

in a fault zone. The specularite and magnetite are confined to the ore body, whereas the adjoining granite is 

largely altered to sericite, chlorite, and pyrite along 

fractures. It therefore appears that the mineralizing 

solution was hot enough to deposit the iron oxides only 

within the fault zone and that those portions of it that 

spread into the walls were cooled to a temperature at 

which the sulphide pyrite was stable. 

The hotter mesothermal stages are represented by 

the Hardscrabble ore body just mentioned, by pyritic 

veinlets that cut the Nitt monzonite stock close by . 

the massive body of pyrite that replaces the adjoining 

Kelly limestone along the main ore zone in the Nitt 

mine, and by veinlets and disseminated grains of pyrite 

and chalcopyrite in the monzonite along the north 

extension of the main ore zone in the upper part of 

. Hardscrabble Valley. The monzonite adjoining the 

Nitt ore body is thoroughly fractured for at least 300 

feet west of the 1nain ore zone, as far as it is exposed 

by the crosscut from the Nitt shaft. The fractures 

throughout this distance are filled with veinlets of 

pyrite and quartz, and the monzonite is chloritired 

and impregnated with pyrite. The marked contrast 

between this wide scattering of the pyrite in the monzonite and its concentration into a massive replacement 

body in the Kelly limestone evidBntly reflects corresponding differences in fracturing and replaceability. 

The limestone was readily and thoroughly replaceable 

and the pyritB was therefore deposited close to the 

channel along which it was introduced, whereas in 

the monzonite only the minerals containing iron were 

very subject to replacement and the solution permeated 

far from its main channel of access before it lost its 

ability to form pyrite. Although the larger pyritic 

veinlets in monzonite suggest that the pyrite was introduced from the main channel, the conversion of the 

iron-bearing minerals to pyrite indicates that the solution introduced sulphur but little or no iron into the 

monzonite for any appreciable distance from the fractures along which it circulated. 

The monzonite along the north extension of the 

main ore zone is also crisscrossed by pyritic veinlets 

and is thoroughly impregnated by pyrite. The pyrite 

iR accompanied by chalcopyrite, which is mainly confined to the veinlets and givBs the rock a close resemblance to the well-known disseminated or "porphyry" 

copper ores; but the amount of disseminated chalcopyrite is so small and in an area of such little topographic 

relief that it is of no commercial interest. The rBstriction of the chalcopyrite to fractures in the ore zone 

is in marked contrast to the much wider distribution 

of pyrite. The chalcopyrite is also interstitial to py- . 

rite . . These relations indicate either that thB chalcopyrite was the last sulphide to crystallize during the 

pyrite stage, the view commonly held, or that it was 

introduced at a distinctly later stage and was deposited 

through reaction between thB solution .and pyrite as 

suggested on page 109. According to either view the 

solution was not able to impregnate the monzonite 

itself with chalcopyrite to any appreciable degree. 

The monzonite is also considerably altered to sericite and quartz along the more pronounced veinlets. 

The concBntration of sericite, here and at the Hardscrabble mine, in rock near these veinlets, implies that 

the formation of sericite was for the most part closely 

associated with the pyrite stage of deposition if not 

with sulphide deposition a~ a whole. The sericitized 

rock grades into chloritized-epidotized rock, which 

suggests that either chlorite and Bpidote had been 

formed at an earlier stage and were replaced by sericite and quartz or all were formed during the same 

stage. If all were formed during the same stage 

the introduced potash and silica seem to· have been 

promptly used up, whereas the original ferromagnesian minerals were hydrated and converted i.nto chlo"-

rite and epidote for .greater distances: 

As stated on page 52, epidote may have forW1ed 

during several stages within the ranges of high and 

moderate temperatures, and the same statement may 

apply to chlorite and sericite, although the concentra-
MAGDALENA MINING DISTRICT, NEW MEXICO 115 

tion of sericite near the main zones of circulation of 

sulphide solutions has the significance emphasized 

above and is of distinct value in the recognition of 

possible ore deposits in or beneath exposed bodies of 

igneous rock. The bleached, sericitized pyritic tuff 

on the southeast slope of Stendel Ridge, for example, 

suggests that sulphide ore may be concealed in underlying limestones along the Stendel fault; however, the 

advisability of searching for such ore depends on 

several factors that are discussed elsewhere. 

The only . sphalerite-galena ore in igneous rock that 

. is referable to the hotter mesothermal stage is that of 

the Hardscrabble mine, already cited. This ore has 

replaced a small amount of highly sericitized granite, 

which was distinctly more permeable and replaceable 

than the original rock. The fact that no similar ore 

has been found elsewhere in igneous rock, even along 

recognized ore zones, implies either that the solutions 

of sphalerite and. galena, unlike those of chalcopyrite, 

had little reacting power with pyrite or igneous rocks 

or that in some places they had deposited their sulphides in limestone before they rose into overlying 

volcanic rocks. 

The cooler mesothermal or leptothermal stage is 

represented by the Anchor vein in Tertiary ( ? ) granite and by several small veins in volcanic rock in the 

southern part of the district. These veins consist 

typically of quartz and barite with small to moderate 

amounts of sphalerite, galena, pyrite, and smaller 

amounts of chalcopyrite. Those in the southern area 

also contain calcite. The granite walls of the Anchor 

vein are not appreciably altered, and vein:-forming 

solutions. therefore did little besides fill the vein fissure 

with quartz, barite, and sulphides. Veins in the south-

. m·n area are commonly bordered by bleached wall rock 

from an inch to a foot or more thick. The sulphide 

solutions that formed the veins were evidently able to 

permeate the walls slightly and to reduce and remove 

the hematite in the reddish volcanic rocks and the Abo 

sandstone. Their relatively large content of calcite 

may represent material that had been removed from 

underlying limestone or from the more calcareous 

volcanic rocks during the upward passage of the solutions. The fact that very little ore has been found 

in any of these veins implies either that only small 

amounts of solutions during the sphalerite, galena, and 

copper stages reached the present surface or that they 

had already deposited most of their metal. contents in 

underlying formations. 

No effects of mineralization at low temperatures 

along ore zones in igneous rocks have been recognized, 

but the presence of calcite scalenohedrons in altered 

i1npure limestone near monzonite not far from the 

Nitt shaft implies that the monzonite also was invaded 

by solutions at comparatively low temperatures. 

J. 

OXIDIZED ORES 

Oxidized ores constituted almost the entire output of 

the district until 1905, and, though the large bodies 

were practically exhausted many years ago, small 

quantities have been intermittently produced until the 

present time, mainly by lessees working small deposits 

or recovering small aiJlounts that had been left in and 

around old stopes. The oxidized ores show a wider 

variatimi in mineralogic character than the sulphide 

ores, as is true in other districts of mixed sulphide ores; 

furthermore, the processes of oxidation have separated 

them to a greater degree, especially the lead from the 

zinc ores. 

The different classes of ore and their derivation are: 

(1) Oxidized iron and iron-manganese ores in small 

quantities, derived from pyritic ores in limestone and 

perhaps also from disseminated pyrite in altered shale 

and igneous rock; (2) lead carbonate ore, derived from 

massive galena and mixed sulphide ores; (3) zinc carbonate ore, derived from massive zinc blende and mixed 

sulphide ores; (4) oxidized copper ores, derived froin 

pyritic copper ores; ( 5) oxidized gold ore, derived 

locally from siliceous mixed sulphide ore; ( 6) oxidized 

silver ore, derived locally from siliceous mixed sulphide 

ore. 

OXIDIZED IRON .AND IRON-MANGANESE ORES 

Oxidized iron ores. derived from pyritic ores low in 

silica are of interest because of their association with 

other ores. They are mainly confined to the lower 

Kelly limestone in the southern parts of the GraphicWaldo and Kelly mines, where the oxidized copper 

ores had been mined before our work in the district 

began. This type of m~terial consists essentially of 

brown hydrated iron oxide with irregularly distributed 

siliceous material, and lies within the original pyritic 

ore bodies and just down the dip from them. . 

Similar iron ore accompanied by manganese oxide 

and clay is found below the original positions of mixed 

sulphide bodies, now represented by lead carbonate 

ore, and along beds and fissures in limestones that 

underlie thoroughly oxidized masses of pyritic shale or 

igneous rock. Those beneath oxidized shale are little 

more than iron-stained clays. 

The largest deposit of brown iron oxide not definitely related to sulphide ore bodies is that in the Vindicator mine. This body, as shown in figure 28, has 

replaced Madera limestone through a vertical range of 

at least 200 feet and an area 80 by 175 feet. On the 

east it adjoins the Vindicator vein, which consists .of 

mixed sulphides in a quartz-barite gangue; on the 

west it grades into unmineralized limestone. The only 

chemical" analysis available is that given on the following page, together with a partial calculation of the 

mineral composition. It represents a sample from the 
MAGDALENA MINING DISTRICT, NEW MEXICO 

main shaft on the 100-foot level of the mine that was 

submitted by V. C. Grubnau. 

Partial chemical analysis of brown oa:idized material 1 from 

the Vindicator mine 

[R. E. Stevens, analyst] 

Analysis 

Si02---------------- Ah0a-- - -- ---- - - --- - FezOa------.,.-------- FeO _______________ _ MgQ ______________ _ 

CaO ___ ___ - ___ - ____ _ 

HzO + - - ------------

HzO- -------------- TiOz _____ _________ _ 

P20s---- ------------ SOa- __ _ ------------ · Cr20a- MnO .. --- ---- ------ _____________ _ _ 

BaQ __ _ --- - - ---- - -·-

56. 25 

7. 36 

15. 32 

None 

. 82 

1. 70 

4. 55 

2. 15 

. 41 

. 70 

2. 30 

. 06 

1. 92 

3.29 

96.83 

Mode 

Quartz ______________ _ Clay 2 _ __ ____________ _ 

Goethite __ ___ _______ _ Manganite ___________ _ Barite _____ _______ ---- Dolomite a ___________ _ Calcite a __ ______ __ ___ _ Jarosite a __ __________ _ 

1 Insoluble in hydrochloric acid, 70.38 percent. 

43. 1 

24.5 

16. 2 

2. 5 

5. 1 

3. 9 

.9 

1.8 

98.0 

2 A clay mineral with most of the properties of beidellite has been identified, but 

other clay minerals may also be present. 3 Dolomite and calcite imply the presence of 2.3 percent of carbon dioxide, and jaro- site the presence of 0.2 percent of potash. These constituents would raise the total 

of the chemical analysis to 99.3 percent. 

The difference between the total and 100 is mainly 

accounted for by carbon dioxide, which is present with 

CaO and MgO in the form of carbonate. The conspicuous amounts of TiOz, Pz05, and Cr203 have not 

been correlated with any recognized mineral. Assays 

of other samples collected at different times showed 

some lead, zinc, silver, and gold. (See p. 161.) 

Inspection of the sample shows that it contains considerable quartz and barite coated with brown earthy 

limonite and that it evidently represents a remnant 

of a quartz-barite vein concealed within the large· body 

of iron oxide. There may be several minor veins concealed within the deposit, but the body as a whole appears to contain much more limonite and to have 

resulted directly from the replacement of limestone. 

The cellular texture and fine box-work patterns in 

parts of it have prompted the sugge8tion that it was 

formed by partial replacement of sphalerite, which 

. has since been completely removed. The only direct 

evidence of replacement seen by us, however, is that 

of unmineralized limestone by limonite. The source 

of so large a quantity of brown iron oxide is not directly evident, but, as suggested on pages 120, 162-

163, a considerable thickness of volcanic rock that 

formerly overlay the limestone may have been impregnated with pyrite along the main fault zone in 

the · vicinity, and downward circulation of water 

through this zone after leaching iron from the 

oxidizing volcanic rock could cause extensive replacement of the limestone by the brown iron oxide. 

The black manga~ese oxides, which are conspicuous 

in parts of the iron and other oxidized ores, have evidently been derived mainly from manganiferous calcite, siderite, and hedenbergite, and to a minor degree 

from the minute quantities of manganese · present in 

any of the rocks along the ore zones. No appreciable 

bodies of commercial grade have been reported. 

LEAD CARBONATE ORES 

The lead carbonate bodies occupy the same positions 

as the original sulphide bodies from which other minerals have been wholly or partly leached. They have 

been mined throughout the upper levels of the larger 

mines and have been the principal product of most of 

the outlying mines. 

Lead carbonate ores, as the name implies, consist 

mainly of cerussite with minor to negligible quantities 

of the sulphate anglesite and the yellow lead-iron sulphate, plumboj arosite. Other lead minerals, such as 

vanadinite and wulfenite, may have been found in 

places; but none were noted by us in the mines of the 

main Magdalena Range, although mine dumps in the 

area northwest of the town of Magdalena contain conspicuous amounts. Impurities include mainly iron and· 

manganese oxides and silica, and some of the outlying 

ores have doubtless contained barite and a little fluorite. 

The highest-grade ore, called "sand carbonates," consists of loose or only slightly cemented crystals of 

cerussite~ some of which has run like sand when the ore 

body was opened from below. The most noteworthy 

occurrence of this ore was in the Big Twenty stope of 

the Kelly mine, where according to the late C. T. 

Brown, who was a lessee of the mine for several years, 

many tons flowed down to the underlying drift and was 

shoveled into mine cars. Some of the high-grade cerussite is firmly cemented into "hard carbonate" ore, but 

other varieties of "hard carbonates" contain considerable siiica and represent original ore in which galena 

was disseminated in grains or streaks through partly 

silicified limestone, especially in the outlying parts of 

the district. 

The lead content of the lead carbonate ores shipped 

since 1904 has ranged from 8 to 38 percent. The silver 

content, however, has been prevailingly low, ranging 

from 1.2 to 10.5 ounces to the ton, although in some 

assayed samples and some of the early shipments (pp. 75-78) it has been considerably higher. 

Some ore from the Germany mine, though relatively 

low in lead, has contained as much as 45 ounces of 

. silver and 1.09 ounces of gold to the ton. 

ZINC CARBONATE ORES 

The zinc carbonate ores have mainly been found 

either vertically below the lead carbonate ores or down 

the dip from them. A few bodies have been found in 

the hanging walls of the lower or down-dip parts of 

lead carbonate bodies. The largest bodies have been 

formed by replacement of limestone beds and some 

smaller bodies by replacement of the limestone walls of 

fissures by reaction with descending water that had 
OXIDIZED ORES 117 

leached zinc from the original sulphide ore. The 

larger bodies may be separated from the lead · carbonate bodies by a few feet of mixed clay and iron 

oxide or may also be separated from them by one or 

more beds of dense or relatively unfractured and therefore impermeable limestone. The "sil·ver pipe" bed,· 

which commonly resisted replacement by sulphide ore, 

has formed the floor of zinc carbonate bodies and, 

where rendered permeable, has been replaced by zinc 

carbonate to a considerable degree. A few small 

bunches of zinc carbonate have been found at considerable distances from known lead carbonate or iron oxide 

bodies of considerable size, and it therefore appears 

that in some places water with zinc in solution traveled 

a long way before finding an opportunity to reac~ with 

limestone. 

Some of the zinc carbonate ore, especially that in the 

"silver pipe" bed, is gray to brown and of massive 

granular texture and so closely resembles the replaced 

limestone as to escape recognition; but most of it is 

of brown to reddish color and of a more open texture, 

with cavities as much as 2 inches in diameter. Close 

examination of the finely porous ore indicates that 

the original grains in limestone had been replaced 

from their boundaries inward, and that-where replacement was not complete the unreplaced parts of grains 

were later dissolved. Some {)f the most open textured ore has a boxwork pattern, as if the zinc carbonate had replaced limestone along intersecting small 

fractures and the intervening remnants of unreplaced 

limestone had later been dissolved. Another conspicuous variety is the· ore consisting of parallel layers 

separated by essentially ·empty spaces. This layered 

ore replaces limestone in part along bedding planes 

and in part along crosscutting fractures, and, as stated 

on page . 92, is attributed to rhythmic molecular reac-. 

tion with water containing zinc sulphate. 

The most striking variety is the green, blue, and 

yellowish smithsonite in botryoidal and related forms 

described on page 92, but its quantity has been small 

and localized. It has perhaps been of more interest 

and value as museum material and semiprecious stone 

than as zinc ore. Practically all of. it had been removed before our' study of the district began, but, 

from what could be seen of it underground and in 

available specimens, it had forrcned as linings of fractures and cavities in and near the mas~ive and cellular 

zinc carbonate ore. Although the deeper-blue variety 

contains a few percent of copper and the yellow 

variety contains cadmium, these metals have not contributed to the value of the ore. ' 

Other zinc minerals occur . in small . to negligible 

quantity in and near the oxidized ores. Calamine, the 

most abundant of them, forms druses in the cellular and 

layered ore and in the 1 adjacent brown iron oxide and 

clay. It may even account for all of the zinc in some 

of the low-grade material. Willemite, so far as known 

(p. 94). js only locally present but has not been 

. found in commercial quantity, either by itself or 

in association with other zinc minerals. Chalcophanite occurs only in lo al small, thin drusy coatings 

in the carbonate ore. Most of the shipments of zinc 

carbonate ores have contained from 26 to 38 percent 

of zinc, but a few small shipments from mines outside 

of the main ore zone have contained as little as 20 

percent. 

OXIDIZED COPPER ORES 

The oxidized copper ores, though found in relatively 

small quantity, h~ve a more diversified mineral com-

. position than the other oxidized ores. Small bodies 

of them, some of very high grade, have been found at 

widely scattered ,localities, particularly in the GraphicWaldo, Kelly, and Young America mines and probably the Hardscrabble mine. · Shipments of _ copper ore 

from these mines have ranged from 3.6 to 42 percent 

of copper and 1 to 23 ounces of silver to the ton. 

The ores in shallow thoroughly oxidized ground con-. 

sist mainly of the green and blue carbonates in drusy 

bunches and " fracture linings throughout masses of . 

brown iron oxide or iron -stained silica and to · some 

' extent in oxidized zinc ore. Their colors in these 

materials are so prominent that their quantity may 

readily be overestimated. In deeper ground considerable quantities of the- black oxide may be present, 

and, where local structural conditions perll}itted concentration of descending water near the bottom of the 

oxidized zone, cuprite and native copper, somewhat 

coated 'with the black oxide and the carbonates, are 

the dominant minerals. The trough in the older workings of the Graphic-Waldo mine, formed by the intersection of the west-dipping argi~lite at the base of the 

. Kelly limestone and an east-dipping lamprophyre dike, 

was most effective in permitting copper-bearing waters 

to converge and concentrate attack on the wedge of 

limestone within the trough. No definite information 

has been obtained regarding the local structural conditions where ore containing 13 percent of copper was 

found in the · Young America mine. 

Even below the oxidized zone the oxidized copper 

minerals have been deposited along fissures and adjacent bedding planes where circulation from above was 

favored, thus enriching the or:iginal sulphide ore to 

some degree. Such enrichment :is especially marked 

along the copper zone in the lower part of the GraphioWaldo mine. 

OXIDIZED GOLD ORE 

The only noteworthy deposit of oxidized ,gold ore that 

we have seen is in the Martin lease of 1915 and 1916 irr 

the Stonewall mine. There the gold, in flakes and wires, 

was closely associated with galena in leached siliceous 

sulphide ore, where the intersection of the west-dipping 

Kelly limestone and an east-dipping fault had pro-
118 MAGDALENA MINING DISTRICT, NEW ME.XICO 

duced a troughlike structure that favored the concentration of descending water. The derivation of the gold 

is not clear, but it was presumably leached from very 

thinly disseminated gold in the silicified upper Kelly 

limestone or in mineralized parts of the overlying shale 

and quartzite. It may well have been precipitated at 

the former base of the oxidized zone, not only by galena 

but especially by chalcocite-coated zinc blende and chal-

. copyrite, which were subsequently leached, leaving the 

gold in residual forms. Shipments of oxidized dry and 

lead ores, credited to the Germany mine but probably 

from the Stonewall claim, which was owned by the 

same company, have contained as much as 1.09 ounces 

of gold to the ton. . 

OXIDIZED SILVER ORE 

Although no oxidized silver ore has been studied by us 

in place, small shipments of siliceous silver ore have been 

reported from time to time. They evidently came from 

places in the silicified l{elly limestone where the small 

content of silver in original siliceous sulphide ore could 

be concentrated, presumably in the form of chloride. 

The highest silver contents in shipped ore, up to 45.1 

ounces to the ton, are credited to oxidized dry and lead 

ores from the Germany mine. The enriched and partly 

oxidized silver-copper sulphide ore in the Iron Mask 

mine has been described on page 95 and the enriched 

and partly oxidized silver-lead-zinc sulphide ore in the 

Anchor mine on pages 159-161. 

ZONES OF ALTERATION 

The alteration of ores, as shown incidentally. on preceding pages, has been effected through processes of 

oxidation and sulphide enrichment. Ores of the oxidized zone were formed in part above the groundwater level and in part at or below it. Some sulphide 

ore remained above it, but enrichment by addition of 

new sulphide minerals took place below it. The change 

from the zone of thoroughly oxidized to leached sulpl~ide ore is rather abrupt in the largest ore bodies, 

although the' transition to the zone of original unleached 

sulphides is gradual and is marked by ore from which 

all sulphides excep~ galena have been nearly or entirely 

removed. Partial oxidation, moreover, has taken place 

along faults and certain open bedding planes considerably deeper than elsewhere and overlaps the zone of 

sulphide enrichment. This zone is not clearly defined, 

as enrichment has taken place to some degree even to 

the bottom of the deepest ore body studied. No information is at hand regarding its downward extent in the 

west ore zone along the ""'r aldo fault. · 

The depth of the oxidized zone differs in different 

parts of the district because of its relations to erosion 

surfaces, different kinds of rock, and geologic structure. The bottom of the oxidized zone has an approximate altitude of 7,450 feet in the Graphic-Waldo mine 

and 7,550 feet in the Kelly mine. These mines are 

comparable, as they lie west of the Kelly-Graphic fault 

and beneath the erosion bench called pediment F. 

(See p. 74). The bottom of the oxidized zone where 

clearly defined in these mines is slightly above the general slope of pediment D. Oxidation therefore appears 

to have taken place mainly during the development of 

pediment D, which marked a temporary base level, and 

to a minor extent since then. The impounding of 

water by faults, however, as will be shown later, appears to account for the lower limit of thorough oxidation, as the impounding formed local reservoirs that 

have not been reached by drainage courses active subsequent to the development of pediment D. The bot- · 

tom of the Juanita mine, at an altitude of 7,587 feet, 

is about on a level with the projected position of pediment D and contains partly oxidized ore. The bottom 

of the South Juanita mine, at an altitude of 7,728 feet, 

or at least 100 feet above the nearest part of pediment 

D, is in oxidized ore. 

Farther south, in the Mistletoe and Linchburg tunnels, which cut the Mistletoe and Young America 

faults, sulphides are present, although t~1e altitudes of 

the tunnels-approximately 7,960 and 8,050 feet-are 

well above and east of the nearest part of pediment D, 

whose altitude here is about 7,750 feet. These ore 

bodies, however, are well to the east of the pediment 

at depths of 300 and 400 feet below the present surface 

and are separated from the pediment by faults that 

doubtless dammed the groundwater to the east of them. 

Sulphides are present in the lower Germany tunnel, 

east of the Germany fault, at an altitude of about 7,860 

feet, and in the Grand Tower mine, which is east of 

the same fault at an altitude of about 8,000 feet. The 

shallower mines on the upper slope of the range are 

all in oxidized or partly oxidized ground, although 

residual galena ore has been shipped from son1e of 

them, and some ore containing considerable sphalerite, 

which had escaped oxidation, was reported in the early 

days of mining. (Seep. 76.) 

In the northern part of the Magdalena Range the 

Hardscrabble mine contains mixed sulphide ore at an 

altitude of 7,750 feet, which is about the altitude of 

pediment F, whereas the bottom of the Vindicator 

mine in Hardscrabble Valley co~tains oxidiz~d iron 

ore at an altitude of only 6,800 feet, although its main 

vein contains mixed sulphide ore at an altitude of 

about 6,850 feet. 

These differences in altitude in part conform to the 

general slope of the range but are governed largely 

by' structure and the different kinds of rock. The 

Kelly limestone with its open bedding planes and 

high degree of solubility had allowed water from the 

surface to develop channels down to ground-water 

level, which, if dependent solely on this limestone, 

would be at the base of the range. . The shaly Sandia 

formation, in contrast, has tended to divert water along 
ZONES OF ALTERATION li9 

its bedding planes and to maintain a shallow water 

level which is expre sed by springs. Where the Kelly 

limestone crops out and dips below the Sandia formation oxidation has taken place along water courses, 

even though they are covered by the unoxidized Sandia 

formation, provided they are above the general groundwater level of any restricted area. The Madera limestone is intermediate between the other two formations 

in its influence on ground water. Its upper more 

massive beds .tend to develop water courses and a 

relatively deep. water level, whereas intervening shaly 

beds and the lower thin-bedded member tend to develop local perched water tables. ·:The igneous rocks 

as a whole tend to develop shallow water levels, except 

where faults in the higher and steeper parts of. the 

range have drained them. Shafts partly filled with 

water even along the crest as well as near the base of 

the range illustrate their capacity for holding water in 

their less open or permeable fractures. 

The two faults that most clearly affect the groundwater table are the Germany and Waldo faults. Little 

information is available regarding the others, as workings along them are too shallow. The Germany fault 

and the mass of argillite and gabbro west of it .formed 

a barrier to circulation down the west-dipping Sandia 

strata and established a local ground-water reservoir 

that must have drained through springs into upper 

Kelly Gulch until disturbed by the Alhambra and 

Germany tnnnels. Drainage through the Germany 

tunnel has supplied the town of Kelly with water, and 

where drainage is blocked by fallen rock the tunnel 

is flooded. The original water level marked the approximate lower limit of oxidation, and only sulphide ore 

with little or no evidence of oxidation was seen in 

accessible parts of the Germany mine. 

The Waldo fault along the base. of the Magdalena 

Range is walled on the west by rhyolite. and forms a 

similar barrier to circulation in the Sandia and lower 

Madera beds. Before the local ground-water reservoir 

was disturbed by deep mining its outlet was through 

a spring along the fault that furnished water for North 

Camp. Minor, east-dipping faults in the w~stern part 

of the Kelly mine made minor barriers that had maintained a rather high water level and restricted the 

d'epth of oxidation along the ore zone. The original 

level of the water is not known, but, as a large amount 

of water was pumped through the Traylor shaft in 

1907, when the sulphide ore was being newly developed, 

the original water level could not have been much if 

any below level 5, at an altitude of 7,541 feet. Even 

as late as 1915 develop1nent of a prospect on level 7 

was being postponed until it could be drained through 

a lower drift. Some natural drainage' may have taken 

place into Kelly Gulch near the 7,500 foot contour 

line. 

Although the Traylor shaft extends about 200 feet 

below the spring near North· Camp, the spring was not 

affected until the west crosscut on level 10 from the 

bottom of the shaft cut the Waldo fault in 1916. Then 

the spring ceased flowing. The fault zone itself was 

obviously full of water that had been supplied fron1 

circulation along the Sandia and lower Madera beds. 

Pumping through the Traylor shaft continued during 

the sinking of a winze 1.n the volcanic rock west of the 

fault to the level of the Kelly limestone in the east 

wall. This deep work was abandoned about 1918, and 

pumping through the Traylor shaft ceased about 1921. 

The mine has been filling ever since, and, according to 

the late Professor Weir,74 of the New Mexico School of 

Mines, the water surface early in 1935 was about 300 

feet below the collar of the shaft, or at an approximate 

altitude of 7,280 feet, and about ·70 feet below the 

dried spring along the Waldo fault. 

No record of the original water level in the GraphicWaldo mine has been found. It was presumably near 

the bottom of the oxidized zone, whose altitude is about 

7,450 feet, although direct connection with the Waldo 

fault could have lowered it somewhat. It was lowered 

by the Waldo tunnel in 1906 to an altitude of about 

7,300 feet and by pumping through the Waldo shaft 

in 1916 to an altitude of about 6,800 feet. Water 

pumped from, the mine served as a temporary water 

supply for the town of Magdalena during the dry spell 

in 1928, when the regular supply from Hop Canyon, 

south of the district, failed. Pumping through this 

shaft was abandoned in September 1928, and the mine 

has since then filled to a level 115 feet below the Waldo 

tunnel. Rainfall since 1928 may· have been below· the 

average, but, even so, the slow rate of inflow and the 

consequent limitations of mine water as means of irri..; 

gation are noteworthy. The fact that the lowering of 

the water below the Waldo tunnel level had no appreciable effect on the spring near North Camp implies 

that southerly· drainage was impeded by cross faults. 

Water level along the west side of_ the main fault 

zone south of Kelly was somewhere above the Mistletoe 

and Linchburg tunnels, whose respective altitudes are 

about 7,950 and 8,050 feet. Still farther south it is represented by the spring in Patterson Canyon, which 

lies close to a west member of the fault zone at an altitude of about 8,100 feet. This spring is along a fault 

that forms the east boundar~ of .igneous rock of a 

considerable-thickness in which the ground-water level 

_is doubtless very· shallow. 

North of the Nitt mine the differmJ.Ces in water level 

in monzonite and Madera limestone are striking. Shallow shafts along the ~yritic monzonite zone in upper 

Hardscrabble Valley are partly filled with water, 

which stands at an altitude of about 7,100 feet, whereas 

no water has been found in the Madera limestone at 

the bottom of the Vindicator mine at an approximate 

74 Weir, J. A., written communication, April13, 1935. 
120 MAGDALENA MINING DIStrRICT, NEW MEXICO 

altitude of 6,750 feet. If the Madera limestone continues very far. beyond its northernmost outcrop h1 

lower Hardscrabble Valley, the altitude of the groundwater surface may be as low as 6,500 feet and may 

slope northward with an extremely low gradient towards the valley bottom along the railroad. If the 

northerly pitch of the strata is appreciable, the slope 

of the water surface is likely to be determined by shale 

below the massive beds of the Madera limestone. This 

position will be of interest if further development is 

undertaken along the Hardscrabble Valley, as water 

in and near the pyritic monzonite and in the volcanic 

and underlying shaly rocks of Stendel Ridge can be 

drained northward at a depth that will permit considerable work without pumping. If eXJploration 

should be undertaken in the Kelly limestone, whose 

altitude beneath the Vindicator workings may be as 

low as 6,100 feet, water would have to be lifted only 

400 to 500 fe~t; and work in Kelly limestone beneath 

the shale on the west side of the Stendel fault may 

require no pumping. 

Information on ground water in the Granit-e Mountain area is limited to the low eastern part, where a 

few shallow shafts are partly filled with water. As 

some of the shafts, in particular the Cambria shaft, 

are rapidly filled with water after heavy rains, they 

are apparently connected with surface fissures that 

probably intersect the creek to the south. The Cambria shaft, which is about 75 feet deep, is also rapidly 

drained. 75 The depth to ground-water level is unknown but may be 100 feet or more. The rather steep 

dips, however, together w1th the strike of the beds and 

faults directly toward the valleys, suggest that the 

ground-water surface is more regular than it is in the 

main Magdalena Range. 

PROCESSES OF ALTERATION 

As the sulphide and oxidized ores in the Magdalena 

district are similar to those in the Leadville district, 

Colo., and as the processes of alteration, which are 

therefore similar, have been thoroughly discussed in 

the Leadville report,76 only ' a comparatively brief 

review of the processes will be given below. 

When the period of dominant erosion and of alteration by descending water began, the present surface of 

the Magdalena district was covered by some additional 

thickness of sedimentary rocks and by a considerable 

thickness of volcanic rock. (See fig. 2.) It was not 

·until the stage of erosion represented by pediment F 

(p. 74) had been completed that the principal ore 

bodies o:f the district west of the Kelly-Graphic fault 

zone were subjected to chemical attack by descending 

water. By that time the volcanic rocks had been about 

5 Moore, Paul, oral communication. 76 Emmons, S. F., Irving, .J. D., and Loughlin, G. F ., Geology and ore 

deposits of the Leadville mining district, Colorado : U. S. Geol. Survey 

Prof. Paper 148, pp. 248-272, 1927. 

as completely removed from the upper slopes of the 

rang as they are today, but P~tterson Canyon and 

Hardscrabble Valley, which were not developed until 

later, were represented by smooth pediments composed 

of volcanic rocks. The volcanic rocks in the mineralized fault zone in the position of the present Hardscrabble Valley are believed to have been pyritic, as 

suggested helow. The impure quartzite and shale 

beds of the Sandia formation, the pre-Cambrian argillite, and the lamprophyre and white rhyolite dikes were 

also pyritic to some degree, especially along miner 

alized fault zones. 

ALTERATION OF COUNTRY ROCKS 

The leaching of these pyritic rocks produced 

sulphuric acid and ferric sulphate, which in 'turn 

leached alkalies and alkaline earths, silica, and carbon 

dioxide from the different rock-forming minerals in 

igneous and shaly rocks and replaced them with ferric 

oxide and clay minerals. Where water with these dissolved constituents entered shale it was largely deflected down the dip; and thick shale beds, even near 

the larger faults, may have prevented the water from 

reaching some ore bodies until the shale was almost 

entirely eroded. The amount of descending water that 

reached and attacked the sulphide ores, therefore, was 

much less in some parts of the district than in others. 

Where the descending water passed from pyritic rock 

into limestone, any free acid in it was promptly neutralized and the ferric sulphate reacted with the limestone, 

replacing it with ferric hydrate, which later became 

partly dehydrated to limonite. Such a reaction has 

been suggest~d to account for the large body of brown 

iron ore in Madera limestone in the Vindicator mine. 

Similar deposits may be present in limestone beds of 

the Sandia formation, though none have been noted, 

and in the uppermost part of the l{elly limestone, 

where they may be mistaken for the oxidized tops of 

sulphide bodies. 

Similar reaction between aluminum sulphate and 

limestone formed allophane or other clay minerals, 

which replaceq the limestone, usually just below those 

parts that had been replaced by brown iron ore.. As 

the process continued and the iron and clay deposits 

grew, the iron oxide tended to migrate downward, 

replacing the clay an'd driving it along as an advance 

guard. The descending water became increasingly 

charged with calcium sulphate and carbon dioxide, the 

carbon dioxide tending to dissolve the limestone and 

to form open channels or water courses. Silica from 

the descending water also replaced limestone to some 

degree, but its relatively small quantity is not readily 

distinguished from the large quantity that preceded 

and accompanied the deposition of sulphide ore and 

later became stained with iron and manganese oxides. 

Where the concentration of alkalies as well as iron 
PROCESSES OF ALTERATION 121 

was high, presumably where water from igneous rocks, 

after its free acid and oxygen had been exhausted, became concentrated on reaching limestone, jarosite was 

formed. The clay minerals and jarosite, where subjected to further attack by water containing oxygen, 

became veined with brown iron and black manganese 

oxides. The combination of iron oxides and clay minerals with or without jarosite and amorphous or 

chalcedonic silica constitutes the oxidized "vein" material that lies along the principal courses followed by 

the descending water; its origin is obviously in dependent of ore bodies in the limestone that it. has replaced, 

although it may be closely associated with some of 

them. · 

ALTERATION OF SULPHIDE ORES 

SOLUTION OF :PRIMARY SUL:PHIDES 

Where descending water charged with material derived from siliceous rocks reached ~ermeable sulphide 

bodies, the sphalerite was dissolved and removed before 

any other sulphides were greatly attacked. Water 

with free sulphuric acid was neutralized by reaction 

with sphalerite and carbonate gangue. Where the sulphuric acid had been exhausted, either before or after 

reaching the ore, ferric sulphate reacted with sphalerite 

replacing it with brown or red iron oxide. The zinc 

was removed in solution together with sulphate and 

carbonate radicals. Chalcopyrite was removed by 

similar processes. 

Pyrite in pyritic and mixed sulphide ore reacted in 

the same way as that disseminated in the siliceous rocks 

and increased or renewed the quantity of sulphuric 

acid and ferric sulphate available for attacking ore, 

gangue, and country rock. Part of its iron was converted to limonite ·and remained essentially in place, 

forming comparatively pure masses and staining other 

materials. The remainder was carried downward as 

ferric and ferrous sulphates. 

Galena, though beginning to oxidize promptly, became quickly coated with a protecting film of lead 

sulphate which in turn became converted into the even 

more insoluble lead carbonate. The galena, therefore, 

remained almost intact until the other sulphides had 

been practically all removed. Honeycombed masses 

of high-grade galena have been mined in otherwise 

thoroughly oxidized ground. These masses also mark 

the transition from the oxidized to the sulphide zone, 

as is well shown in the Graphic-Waldo mine. (See 

pl. 33.) 

The transfer of gold in the oxidized zone was presumably dependent on the liberation of chlorine. The 

chlorides, possibly derived from the air and from small 

amounts in siliceous rocks by descending water, may 

have reacted with any manganese dioxides that had 

already been formed by oxidation, thus liberating 

chlorine, which was able to extract minute quantities 

of gold from any of the ores. This reaction evidently 

200889-42- 0 

took place after the general process of oxidation was 

well-advanced. In the ·absence of this :t;eaction gold 

would remain in leached ore in its original position, 

but no noteworthy amount of strictly residual gold has 

been recognized in the Magdalena district. Its ultimate source, therefore, is indefinite. Presumably it 

was finely disseminated throughout veins and replacement bodies of ore and along pyritic fissures and seams 

in the siliceous rocks. 

The general absence of high silver content, either in 

oxidized ore or in the under lying parts of the larger 

sulphide ore bodies, forces the inference that most of 

. the silver remained without appreciable transfer or 

concentration throughout the entire period of oxidation. A little silver, however, was presumably dissolved and carried downward and redeposited nearby, 

usually in close association with lead car onate. The 

failure to detect visible grains of chloride or other 

compounds leaves the occurrence of silver in the scat.., 

tered bodies of relatively high-grade oxidized ore to 

conject~re. 

REDE:POSITION AS :PRODUCTS OF OXIDATION 

The metals dissolved by descending water were redeposited, as partly implied already, by the following 

processes: hydration and oxidation, which accounted 

for the relatively insoluble brown iro;n ore and lead 

sulphate and carbonate; evaporation, which a.ccounted 

for incrustations of m,inerals along cavities, fractures, 

and the walls of fnine workings; reaction between different solutions and between solutions and sulphide ore 

or wall rock, which accounted for the large bodies of 

, zinc carbonate and smaller bodies of oxidized copper 

and gold ore, as well as enriched copper and silver sulphide ores. As oxidation took place in stages, redeposition is most conveniently considered in corresponding stages. 

Zino carbonate stage.-Where water that had pass2d 

through a sulphide body into limestone contained free 

sulphuric acid and ferric sulphate, the acid was 

promptly heu~ralized anc\ the uppermost part of the 

limestone was replaced by ferric oxide, manganese 

oxide, and clay. Such deposits are found today as 

layers separating lead carbonate and even some galena 

ores from underlying deposits of zinc carbonate, which 

were formed after the iron, manganese, and clay had 

been removed from solutions. Where water had been 

depleted of the acid and ferric, manganic, and aluminum sulphates before reaching the limestone, no such 

layer was formed, and zinc carbonate replac-ed limestone immediately below the original ore body or its 

siliceous casing. 

The replacement ·of limestone by the normal zinc 

carbonate, smithsonite, began along grain boundaries 

and worked toward the centers of the grains. Where 

replacement was complete the zinc carbonate preserved 

the structure and texture of the limestone. As replace-
122 MAGDALENA MINING DISII'RICT, NEW MEXICO 

1nent was in part the result of reaction between calcium carbonate and zinc sulphate, which involves 

considerable shrinkage, it is concluded that some of the 

zinc was in solution as bicarbonate and, while replacement was in progress, was deposited as additional carbonate in sufficient quantity to preserve the original 

structure and texture. Where this additional supply 

of ztnc was insufficient, a corresponding amount of 

shrinkage resulted and is represented by the layered 

ore. Openings in the cellular ore may be in part the 

result of shrinkage, but they appear mostly to represent unreplaced remnants of limestone' that have been 

subsequently removed. Minute openings in the massive 

ore may be attributable to one or both causes. 

Complete replacement took place 77 close to the 

ground-water level if not below it, where the limestone could be permeated by slowly moving or stagnant 

solutions. The ferrous and manganous carbonates in 

the gray zinc carbonate ore supports this statement, as 

they show that the reaction took place in the absence 

of oxygen, the presence of which would have prevented 

the formation of ferrous and manganous carbonates. 

Where the gray ore was later exposed to oxygen it 

turned brown, owing to 'the oxidation of its iron. 

Iron-manganeS'e oxide stage.-After the removal of 

zinc blende from the original ore bodies, oxidation 

o£ pyrite and chalcopyrite generated new supplies of 

sulphuric acid and ferric sulphate, most of the sulphate 

being promptly converted into brown iron oxide and 

left as a porous residue. Any that escaped oxidation, 

together with the acid, was carried downward into 

the zinc carbonate zone, where it reacted as in the first 

stage. Casings of quartz or · jasperoid or any layers 

of siliceous rock became stained_ with brown or red iron 

oxide. Zinc carbonate was replaced by the same oxides 

which supplemented the layer previously formed be~ tween the zinc and lead carbonate bodies, and 'the dissolved zinc was redeposited farther down, either by 

replacement or as linings of openings. As the water 

during this stage had little or no excess of carbon 

dioxide, this redeposited zinc was more likely to form 

the layered and cellular varieties than the massive 

variety of zinc carbonate ore. 

As chalcopyrite, though more readily soluble than 

pyrite, was, for the most part, considerably protected 

by its interstitial position in pyritic ore, the transfer 

and redeposition of copper accompanied rather than 

preceded the iron-manganese oxide stage. The minute 

inclusi.ons in sphalerite were doubtless dissolved during the zinc carbonate stage, but the quantity o£ copper 

involved was too small to account for any conspicuous 

amount o£ copper ~arbonate, separate from that transferred later. The copper was carried downward as 

sulphate and replaced either limestone or zinc carbon71 Lindgren, Waldemar, T'he nature of replacement: Econ. Geology, 

vol. 7, p. 531, 1912. 

I 

ate with the copper carbonate. Whether the green 

carbonate, malachite, or the blue carbonate, azurite, 

was formed evidently depended upon differences in 

concentration of copper, carbon dioxide, and water. 

Replacement of zinc carbonate by copper carbonate 

evidently did not exhaust quite all the copper in solution; the remainder of it was deposited as a minor 

constituent of the blue and green crustiform and 

botryoidal smithsonite and as a major constituent of 

aurichalcite, whose deposition followed or alternated 

with that of the crustiform smithsonite. 

The copper that descended along the pyritic zone 

without coming in contact with limestone or other 

carbonates was in part deposited, temporarily at least, 

as the green and blue carbonates, but toward the bot-< 

tom of the oxidized zone, where carbon dioxide was 

deficient and where ferrous sulphate was present in 

solution, it was deposited as the black and red oxides 

and, where oxygen also was deficient, as native copper. 

Where structural conditions permitted the descending 

waters to converge and stagnate at the bottom of the 

oxidized zone, as in the trough between the tilted 

argillite floor and crosscutting lamprophyre dike in 

the Graphic-Waldo mine, these minerals accumulated 

in unusual quantity. Where the water could descend 

below the oxidized zone, the copper sulphate in s9lution was reduced by contact with chalcopyrite and 

pyrite and deposited as co~tings of chalcocite. Similar . reaction with galena and sphalerite produced 

coatings of covellite. 

Lead! carbonate stage.-Oxidation of galena mostly 

followed that of pyrite. The descending waters during this stage were bringing in very little sulphuric 

acid; and the proportion of carbon dioxide, especially 

in water that had passed through limestone before 

reaching the ore, was relatively high. Thus most of 

the lead sulphate derived through oxidation of galena 

was quickly changed to the carbonate without appreciable transfer; and the lead carbonate ores therefore 

remained in the general positions of the original sulphide bodies, either in nearly pure masses or mixed 

with iron oxide, quartz, and barite, according to the 

composition of the original ore. The change from 

lead sulphate to carbonate released the sulphate radical, which helped the water to retain some lead and 

iron sulphate in solution; and where these constituents 

became sufficiently concentrated and the acid neutralized, the yelJow basic lead-iron sulphate, plumboj arosite, was formed as a replacement of either limestone 

or iron oxide. Too little of this mineral has been 

found in the district to justify further discussion of 

the origin. 

Final base-metal stages.-After processes involving 

sulphuric acid and ferric sulphate had come to an end, 

processes involving oxygen, carbon dioxide, and silica 

caused minor changes and additions to. the oxidized 
MINES IN THE' MAIN . ORE1 ZONE 123 . 

ores. Oxygen attacked iron and manganese in zinc to permit identification, is associated with chalcocite 

carbonate ore, forming brown iron and black man- / in .the' or~ of the Iron Mask mine. 

ganese oxides and the manganese-zinc oxide chalco- Gold, carried in solution as chloride, could be prephanite. Zinc carbonate was dissolved to some ex- cipitated by ferrous sulphate at or below the bottom 

tent and redeposited as coatings, in part over those of of the oxidized zone; also by chalcocite, chalcopyrite 

iron and manganese oxides. The exhaustion of ex((ess or galena, and less readily by pyrite or sphalerite. The 

carbon dioxide caused the deposition of the basic car- close association with sphalerite or with cavities left 

bonates hydrozincite and aurichalcite, usually upon by the leaching of sphalerite may be explained by a 

crusts of s~ithsonite .or alternating with layers of · complex reaction involving gold chloride, :ferrous sulsmithsonite, as if there had been small renewals of , phate, and sph.alerite, or1 by reaction between the 

solution that still retained some excess of - carbon chloride and films of chalcocite that once coated the 

dioxide. After practically all the carbon dioxide had sphalerite.' Whatever the reactions were, the original 

been used in this way, silica became the most active amounts of gold were so small and thinly scattered 

acid radical and formed calamine, the latest of the that the effect of downward transfer was negligible 

definite zinc minerals. It formed mainly along cracks except where small structural troughs, illustrated in 

and openings in and near the zinc carbonate as a the Stonewall mine, permitted the convergence of water 

result of .supersaturation, although it replaced the from a wide area into a place where the reacting 

carbonate. to a small extent. Its deposition was ac- minerals· were available. 

companied by that of small amounts of "tallow clay," 

which was formed either by the direct deposition of a 

hydrous aluminum-zinc silicate or by the partial 

replacement of aluminum in clay by zinc. The source 

of the small amount of sili9a represented was evidently in the siliceous gangue of ·the original . ore 

and in the silicate minerals of the overlying rocks. 

Small amounts of opal or chalcedony may have followed calamine. 

During the final stages the secondary sulphides and 

oxides of copper tended to change into the more stable 

carbonates. The process is well illustrated in the Iron · 

Mask mine, where progressive changes !rom chalcocite 

through covellite and cuprite to malachite are represented. Copper that had not been removed from the 

oxidized residue of pyritic ore was deposited as crusts 

and veinlets of malachite or azurite in brown iron ore. 

The last product of deposition ·was colorless calcite 

in the flat, disklike or "nailhead" variety of rhombohedrons. These crystals line cracks and vugs in all 

varieties of oxidized ore~especially the porous brown 

iron ore-and in the adjoining wall rock. No consideration has been given to aragonite, wulfenite vana- . . . ' dm1te, and certain other minerals that have been 

m~rely reported .from the · district but have not been 

seeP. by us. 

·P1·ecious metal stage.-The amounts of silver and 

gold in the original ores were so small that. they were 

affected only after alteration of the common sulphides 

exposed them to attack. Although some silver may 

have been retained in the oxidized zone 1 as chloride 

' some was carried down in solution and deposited either 

as minute quantities of native silver or argentite in or · 

below the lower part of the oxidized zone by reaction 

with ferrous and copper sulphates, by confplex reaction 

between these sulphates and zinc blende! or by <,lirect 

reaction with chalcocite. The only visible silver ~ineral, whi~h could not be separated in sufficient quantity 

MINES 

. The mine descriptions are arranged in the following 

order: Those extending southward from the Nitt stock 

along the main ore zone ; those east or west of the main 

z~ne and south or east of the Nitt stock; those north 

of the Nitt stock and in the main Magdalena Range. 

Very little information is available on properties north 

and west of the main range, as most of the work in 

those places was done so long ago that few records, 

even including heresay eviden~, have been found; but 

the :few brief descriptions presented should give a fair 

impression of conditions there. 

· MINES IN THE MAIN ORE ZONE 

NITT MINE 

The Nitt mine is owned by the Tri-Bullion Corporation, incorporated in 1927 as a successor to the TriBullio.I;l Smelting & Development Co. It comprises 

about 115 acres, including the Silver Bell claim (pl. 2) 

and an adjoining group of six unpatented claims that 

were acquired by the older company in 1912.78 These 

claims are mostly within the area of the Nitt stock, but 

they include an adjoining strip of sedimentary rock 

about 210 feet wide that is crossed by the northernmost 

part of the main ore zone. This ground was leased to 

the Ozark Smelting & Mining Co. from 1914 until1923, 

and its output for those years was included ..,with that 

of the Graphic-Waldo mine. From 1923 until 1930 

it was leased to J. A. Macdonald, of Kelly, who, because of the closing of the Ozark Co.'s mill in 1921,· 

mined only ore of shipping grade. The output in these 

years is shown in the tables on page 124. This ore, 

according to Mr. · Macdonald, has averaged about 20 

percent of zinc, 2 percent of copper, 0.5 pe!'cent of lead, 

and 2 ounces of silver to the ton. 

78 Mines handbook, vol. 14, p. 1260, 1920. 
124 MAGDALENA MINING DISTRICT, NEW MEXICO 

Ore shipped from Nitt mine, 1923--.30/ and its gross metal 

content 

(Data collected by C. W. Henderson. Geological Survey and Bureau of 

Mines, U. S. Department of the Interior, Denver, Colo.] 

/ Ore '0 "' 

j ~ Q "' ~ "' '0 '0 Q 0 Q Q ~ B ~ § Year ::3 ~ 0 0 

~ .... ~ B B Class Tons '0 Q;) 0. '0 

0 ~ 0. <e ~ ~ 0 Q;) 

0 0 ...::l N --------------------------

2 1923 rP.fo'_ '"~~hid' :::::: 189 4. 40 1, 052 37,069 683 --------- 930 .40 2, 925 us, 522 

1924 Zince-lead sulphide. ___ 202 -- i2~i2o- ------ ------- --------- ll3, 120 

Zinc sulphide. _________ 46 ------ ------- --------- 28,913 

topper sulphide. ___ ___ 368 1, 523 49,458 - 32~383 " --------- 1925 Lead sulphide. ____ ____ 72 99 391 

Zinc sulphide. _________ 718 ""507 ~ 339 T9o- 129 39,386 

1926 _____ do ________________ _ 1, 205 1, 598 7,107 33,233 908,068 

1927 _____ do _______ __________ 422 2. 40 934 9,879 15, 427 166,155 

1928 { c.opper sulphid~- ---- 1, 990 2. 60 4, 3~3 118; lQ.4 Zmc-lead sulphide. ___ _ 848 -184~ 822" ------ -4;io2- 408,642 

{Copper sulphide. ______ 2, 031 ------ 144,196 --i7;ii6" --------- 1929 Lead sulphide. ________ 68 100 615 

Zinc sulphide. _________ ---61;786 91 ------ --------- {Copper sulphide. __ __ __ 393 ---i~628" ------ 1,186 28,374 --------- 1930 Lead sulphide. ________ 86 276 1, 951 23,450 

Zinc- --ii9.-ooo lead sulphide. ____ 272 847 --------- 14, 157 

9, 931 19. 70 19, 124 515, 666 37 4, 405 2, 313, 023 

1 Mine idle 1931-39. 2 Output for 1914-22 was included in output of Graphic-Waldo mine, operated by 

Ozark Smelting & Mining Co., to which the Nitt mme was leased. 

Sulphide ores shipped from Nitt mine, 1923-30, and average 

gross metal content (based on assays) 

[Data collected and classified by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Copper Lead Zinc-lead Zinc 

Year Silver Cop- Silver Lead Zinc Lead Zinc 

Ore (oz. per Ore (oz. ( Ore ( (per- Ore (per-

(tons) per (per- (tons) per c~~~) (tons) c~~~) cent) (tons) cent) ton) cent) ton) 

1923 .. ~-- 189 5. 6 9. 8 ------ ------ ------ ------ ------ ------ ------ ------ 1924______ 930 3.1 6.4 ------------------ 202 28.0 3.0 46 31.4 

1925______ 368 4.1 6. 7 72 1. 4 22.5 ------ ------ ------ 718 35.3 

1926.----- ------- ------ ------ ------ ----- _· ------ ------ ------ ------ 1, 205 37. 7 1927 _____ _ ------- ------ ------ ------ ------ _· _____ ------ ------ ------ 422 19.7 

1928 ____ . __ 1,990 2.2 3.0 ------------------ 848 24. 1 10.9 ------------ . 1929 __ __ __ 2,031 2.0 3. 5 68 1.5 12.6 ------ ------------ 91 33.9 

1930______ 393 3.0 3.6 86 3.2 13. 6 272 21.9 2.6 ------ ------

5,9o1 ____________ 226 __ ___ _____ __ 1,322 _____ T _____ 2,482 ____ _ _ 

NOTE.-The copper ores shipped in 1923-25 were evidently enriched somewhat in copper and silver, whereas those shipped in 1928-30 more nearly express the original 

metal content. The lead and zinc-lead ores were comparatively low in lead and 

correspondingly low in silver. Assays of the zinc ores shipped in1926 and 1927, which are presumably representative of the zinc ores as a whole, showed an average of 1.5 ounces of silver to the ton, 0.5 percent of. copper, and 1.5 percent of lead. 

The mille is opened by a shaft 300 :feet deep, whose 

collar has an altitude o:f 7,446 :feet. Two levels have 

been driven :from it at depths o:f 200 and 300 :feet. 

Sublevels connected with these levels by winzes have 

been driven in the ore zone at depths o:f 230, 275, and 

350 :feet, the last two connecting with levels 10 and 11 

o:f the Graphic-Waldo mine. About 4,000 :feet o:f drifts 

and crosscuts have been driven, including some short 

irregular drifts in ore that have been destroyed by 

stoping. The mine was studied by Loughlin in 1916 

and by Lasky in 1929. As its ore body is the northern 

part o:f the main pre body o:f the Graphic-Waldo mine, 

the two are described as one on the following pages. 

GRAPHIC-WALDO OR OZARK MINE 

The Graphic-Waldo mine, owned by the Ozark 

Smelting &: Mining Co., a subsidiary o:f the Sherwin 

Williams Paint Co., comprises a continuous area o:f 227 

acres about" three-fifths o:f a mile north of Kelly. The 

developed ground is bounded on the west by the Waldo 

and Contact claims and on the east by the Miriam and 

1896 claims. The company also owns the Ozark mill, 

1¥2 miles west-northwest of Kelly, and its total 

holdings cover 800 acres. 79 

There is. some confusion in the naming o:f the mine. 

The Graphic and Waldo claims, which are among the 

oldest in the district, are about 1,000 :feet apart,- are on 

different ore zones, and were originally under different 

ownership. The original Waldo workings were along 

the Waldo :fault, but after the 'V" aldo tunnel was 

driven, in 1906, the deeper ores o:f the mai~ ore zone 

in the Graphic ground were mined through it, and the 

Graphic property also became known as the Waldo 

mine. The levels throughout the entire workings are 

numbered consecutively, and it has become the informal 

practice to refer to levels above level 6 as the Graphic 

and to all levels below that as the Waldo. In this report the mine as a whole is called the Graphic-Waldo 

mine. The workings have also been called the Ozark 

mine, after the present owners. 

The Ozark mill, erected in 1913, was operated until 

the depression o:f 1921, as shown on pages 80-81, except 

during the last hal:f o:f 1916, when it was destroyed by 

fire and had to be rebuilt. Production. o:f the mine 

and mill during the period 1918-20, inclusive, declined 

markedly, according to the company's report to the ' 

State Tax Commission, and operations were conducted 

at an aggregate loss o:f $403,619.06.80 The report also 

stated that ore reserves amount to 50,000 tons averaging 

12 percent o:f zinc. 

The mine and mill, because o:f market conditions, 

remained closed between 1921 and 1926, except :for a 

little work by lessees in 1924. Company operations 

were then resumed, and both ore and concentrates were 

shipped until the end o:f 1926. Some or all o:f these 

concentrates were exported. The mill was again closed 

in 1927, and mining operations were restricted to pumping and diamond -drilling and a little leasing until 

late in 1929. The mine was closed :from 1929 to 1937, 

when mining was resumed on a restricted scale. 

The output :from 1905 to 1939, inclusive, is shown in 

the accompanying tables. Operations were confined 

mainly to the mining o:f oxidized or.es :from ~he older 

workings and the selective mining o:f high-grade zinc 

sulphide ore until' 1913, when milling began. Thereafter the lower-grade zinc ores were mined and along 

79 Mines handbook; vol. 18, p. 1685, 1931. 80 Finlay, J. R, Report on appraisal of mines in New Mexico: New 

Mexico State Tax Commission, 1921-22, p. 53, 1922. 
MINES IN THE MAIN ORE ZONE 125 

with them the zinc-lead ores, which were shipped to 

zinc-oxide plants, and the pyritic copper ores, which 

underlay the bulk of the other sulphide ores and were 

not developed until about· 1913. The percentages of 

copper in copper sulphide ores imply local enrichment, 

but any enrichment in silver has been negligible. The 

quantity of lead sulphide ore shipped is surprisingly 

small, considering the quantity seen in the transition 

zone between the oxidized and sulphide zones in 1915; 

it may be that the lead sulph.ide has been included with 

oxidized lead ores in the annual statistical reports. 

The output ·of oxidized ore, largely the work of 

lesses, represents the extension of lead stapes in the 

older part of the mine and the mining of zinc carbonate ore in the adjoining ground: The relatively large 

output of oxidized lead ore of less than average grade 

in 1916-18 accords with the high, wartime price of lead. 

The low content of silver and its .rather uniform ratio 

to lead in the oxidized lead ore is noteworthy, as is 

the prevailingly high grade of the oxidized zinc ore 

regardless of the ·average value of zinc. 

Ore produced at Graphic-Waldo mine, 1905-39 1 and gross metal 

content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] . 

Ore . I Gold2 Silver Copper Lead Zinc Year shipped (ounces) (ounces) (pounds) (pounds) (pounds) (tons) 

--------------------

1905_ --- - ----- 25,150 ---- ---- - · 2,000 365,100 94,500 15,421, 875 1906 ___ - ------ 6,907 ----·------ ---------- 64,560 1, 248,680 3, 341,300 1907 __ ________ 2,250 ---------- 2,300 24,000 375,000 825,000 1908 ___ ------- 1, 766 ---------- ---------- ------------ ------------ 1, 243,200 

1909 ___ ------- 1,263 ---------- 1,126 12,871 164, 543 661, 500 1910 ____ -- ---- 6,280 1. 55 637 4,165 71,181 4, 234,300 191L ________ 2,894 3.0 1, 834 23,869 159,578 1, 739,033 

1912_- -------- 1,085 .60 522 2,012 72,827 596,556 

1913_ -- ------- 33,382 5. 22 6,008 167, 198 822,382 10,204,488 

1914_ --- -- ---- 49,681 5. 51 8, 842 207,354 823,734 15,449, o92 

1915_-- ------- 63,939 ---------- 36,522 1, 394, 165 990,249 17,022,410 

1916_-- ------- 47,116 18.30 44,494 913,944 2,116,034 11,672,000 

1917_ -- - -- ---- 68,599 26.99 111,667 2, 632,068 2, 853,627 9, 555,600 

1918_ --------- 49,943 .80 50,037 505,762 3, 285,033 12,474,200 

1919_ --------- 12,014 - --- ------ 24,144 611,089 783,579 3,130,080 1920 __ ________ 16,295 ---------- 31,486 302,918 1, 151,484 4, 427,765 192L ___ ______ 412 ---------- 155 645 88,770 163,178 

1922_- -------- 8,045 ------ ---- 2.484 7, 358 1, 615,170 3, 869,123 

1923_ --------- 8,379 - --- -- ---- 2,344 5, 166 1,880, 574 4, 161,894 1924 __________ 8,393 -- ----- -- - 1, 475 4,266 1, 544,649 4, 637,800 

1925_ --------- 8,310 -------- -- 6,424 16,067 I, 711,070 3, 319,840 

1926_ --- ------ 38,087 2. 74 8,230 43,342 1, 007,950 8, 366,606 1927 ______ ____ 21,900 ---------- 29,320 124,296 654,254 5, 168,142 1928 __ __ ____ __ 67 5. 70 2,152 896 44,499 25.932 1929 ___ _______ 248 1. 50 706 8,531 --··---- ----- ------------ 1937 ______ ____ 3, 878 --- ----- -- -----·· ··--- --------- -- 114,788 1, 750,510 1938 _____ _____ 983 ---- ----·- - ------ ---- ------------ 7, 556 543,531 

1939_ -- ----- 989 ----- - ---- - --------- ··-- - -------- 24,291 566,783 

------- 488,255 71.91 374,909 7, 441,642 23,706,002 144, 572, 338 

1 Mine idle 1930-36. 2 No gold recorded until1910. 

Classes and average gross metal content of ore shipped from Graphic-Waldo mine,1 1905-39 · 

LData collected and classified by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Sulphide ore Oxidizep. ore 

Copper ore Lead ore Zinc-lead ore Zinc ore Copper ore Lead ore~ Zinc-lead ore Zinc ore 

Year 

------------------------------------------- - ------------------------

igg~====== === ===== ====== ====== ==== == ====== ·==== ==· --6;ioa- ---25- ---io- ============ ====== 1, ~~ --~~~- 12i~ ~g~ --~~~- ~i· 5 :======= =:==== ===== = 23, ~g~ ~~:g 1907 ______ ------ -- ------ "- ---- ------ ---- 7 - ------ -------- - ----- - ----- 900S 33.3 200 2.4 6 750 2.4 25 -------- --- --- ------ 400 28.1 1908 ____ __ -- ------ ------ ------ ------ -.. 0--- ------ -- - ----- ------ ------ ---- -------- "----- ------ ------ ------ ---- ---- ----- - -- ---- - ---- --- -- ---- ---- -- 1, 766 35.1 1909 ______ -------- ------ ------ ------ ------ ------ -- ------ - ----- ------ 9458 35.0 ------ ------ ------ 318 3. 54 25.9 -------- ------ ------ ·------- ------

i~i~====== ======== :===== ====== === === ====== :===== ======== ====== ====== 'gg~~ ~g:& ====== ====== ====== :~ ~:i5 i~:: ======== ====== ====== --1;787- --36-- 1912 ______ -- ------ ------ ------ ------ ----- - ------ -------- ------ --- --- -- --------'-- ------------ - "---- ------ 163 3.2 22.3 -------- ------ ------ 922 32;4 

1913______ 448 8.5 26 ___ ___ 36. 8 ______________ ____ __ { 26,68~~ ~g:r --~~~- ===== = -~=~~ -~·-~=~- =~=-- ~~ -- =~~- ~~ ~~~~ --=~~~~- --~~--

1914 ______ 2,600 2. 8 4.0 29 ---- -- 23. 5 1,503 24. 8 12. 0 { 38,26~~ f~J ====== ====== ===== = ---~~~- ~~~- ~~~ --- -~~=- -~~~~ ~~~~ ~~~~=- --~~-- 1915 ______ 12,627 2.7 5.4 ______ ------ ______ __ _____ __ ________ __ 42,301M 14.9 , 82 .5 9.1 648 3.7 23.6 2,281 18 15 6,000 30 

1916 ______ 10,128 2.7 4.2 ------ ·--- -- ______ 5,500 18.0 10.0 24,100M 14.6 76 5.2 7. 8 2,912 5.7 17.4 ______________ ------ 4,400 30 1917 ____ __ 36, 303 2. 5 3.5 ______ ------ ______ 3,450 18.0 10.0 18,200M 15.3 __________ __ __ ____ 6,356 3.2 16.8 _________________ ___ 4,290 32 1918 ______ 7,344 2. 4 3.0 ______ -- ---- __ ____ 13,250 20 8 21,271M 11.1 __________________ 3,593 3.5 14.3 ____________________ 4,485 27.4 1919 __ ____ 4,224 5.1 7.1 ______ ------ ______ 1,340 22 11.9 2,850M 13.4 ________ .__ __ _____ _ 771 3.53 16.8 1,550 31.5 6 1,279 31.1 1920 _____ _ 2,875 3.8 5. 0 ______ ------ ___ ___ 2,849 21.2 12.5 8 061M 14 2 964 4.6 20.7 _________ _ -- ---- 1,546 30 

192L _____ -------- -- --- ------ ------ ------ __ ____ 351 19.9 9.8 ---~ ------- --- ~-- ====== === === =~==== 26 6.0 36.9 ===- ---- =----- ______ 35 33. 1 1922____ __ 32 4.6 2.4 ------------------ 6,160 25.0 10.0 ------------------------ ------------ 483 4.8 24.3 640 23.5 11.5 730 33. 4 1923 ____ __ --- ----- -------------- -- -- ---------- -- 7,685 26.0 11.0 ------------------ ----- ------------- 468 5.0 20.3 -------- ------ ------ 226 36.7 1924 ____ __ -------- -- ---- -- ---- ------------ ----- - 7,247 30.0 8.0 ------------ ------------ ------ ------ 422 3.5 19.9 724 ·20.0 15.0 -------- ___ : __ 1925 __ ____ -------------- ______ 1,914 3. 4 17. 3 5,996 26.2 8.0 ------------------------ ---- -- -- ---- ·------- ---- -- ---- -- 400 23.0 11.0 -------- ------ 1926_____ _ 319 3.4 4. 8 ------ --- --- ___ ___ 3,425 25.2 7.4 32,793M 10.1 _____ ____ ______ ___ 1,550 3.0 14.7 -------------- -- ---- ----- ------ 1927 __ ____ -------- -- -- -- ------ ------ ---- -- ______ 456 17.0 5.0 20, 722M 12. 0 ______ ______ __ ____ 722 3.0 18.9 -------- ---- -- --- --- -------- ------

1928 5 ___ __ -- - ----- ------ - - ---- 567 32.0 33.2 -------- .. ----- ------ -- ---------------------- --~--- ---- -- -------- ------ ------ -------- ---- -- ------ -------- ------ 1929____ __ 6248 2.8 1.7 ~- ---- -------------------------- ------ _________ : __ -------------------------------- ------ ----------------------------------------

t~~r==== = ~~====== 77 === === ===== = :== === ====== ====== ======== =;==== =·===== 83:!~~~ ~!J ====== ====== ==== == ======== ====== ====== ====~=== ====== ======~======== ====== , 148 · == == 2. 036 == = 65.315 ==i== 249,403 - == 2, 447 · ~-~-::-=-~·~r-~-~ 22, 926 -== == _ 6, 642 1

==1== 

1 

62,338 == 1 Includes shipments from Nitt mine from 1914 to 1922, when that mine was under lease and was worked as a part of Graph'ic-Waldo mine. 2 Oxidized lead ore contained from 0.4 to 0.8 per.cent of recovered copper and about 0.005 ounce of gold to the ton. The gold credited to the mine in 1926 came from this ore. 3 Average silver content expressed in ounces to the ton, is commonly too low to be paid for and frequently has not been recorded. Average gold content is less than 0.05 ounce to the ton and has rarely been recorded. Less silver and gold in zinc-lead ores than in lead ores. 

4 S, Ore shipped crude; M, mill ore. · . • Mine and mill idle. 67 tons of lead concentrates were separated from zmc concen- trates by tabling and were shipped. It contained 0.083 ounce of gold and 32 ounces of silver to the ton, 0. 7 percent of copper, and 33.2 percent of lead; also, 19.4 percent of zinc, which was lost. .· . . 6 Dry ore from dump of Waldo shaft. Averaged 0.006 ounce of gold to the ton. 7 Mine and mill idle 1930-36. _ s Contained 1.5 percent lead in 1937, 0.4 percent in 1938, and 1.2 percent in 1939. 
126 MAGDALENA MINING DISII'RICT, NEW MEXICO 

The mine was studied· by Loughlin in 1916, but the 

workings opened since then were inaccessible when 

field work was resumed in 1928 and 1929. We are 

ir..debted to the late Philip B. Argall, general manager, 

and Superintend~nts Pressler (1915) and P. H. Argall 

( 1916-29) for helpful information during the study 

and to Professor J. A. Weir, of the New Mexico School 

of Mines, for information regarding depths of more 

recent workings and the depth of ground water in 

1935. 

The mine includes 14 levels, 10 of which are shown 

on plate 31. These levels are opened by several tunnels and one shaft. The Mitchell tunnel, whose altitude is 7,840 feet, is equivalent to level 1 and crosscuts 

the southeastern part of the property. Five short 

tunnels at similar and higher altitudes explore the long 

faulted outcrop of Kelly limestone in the northeastern 

part. The lower, western part of this outcrop is 

opened by the Graphic tunnels 1, 2, and 3, which correspond to levels 1, 2, and 3. The No. 1 tunnel is also 

called the Gibbany tunnel. 

MAIN WORKINGS 

The No. 3, or main Graphic tunnel, extends southward along the Kelly limestone. It connects about 

1,200 feet south of its portal with the crosscutting 

Greyhound tunnel, which extends east-northeastward 

from the central part of the property. Farther south 

level 3 connects through a stope-raise 30 feet high 

with level 4 of the Kelly mine. 

Level 4 of the Graphic mine was opened through 

the Ida Hill tunnel, which follows a zigzag northeasterly course, explores mineralized fissures in the 

Sandia formation, and connects eastward with level 3 

through stoped inclines in the Kelly limestone. Levels 

5 and 6, and also level 4, were opened through a southsloping incline from level 3, but levels 7 to 11 were 

opened through the Waldo tunnel whose portal is at 

North Camp at an altitude of 7,284 feet. This tunnel, 

completed in 1906, extendea eastward for about 1,700 

feet through rhyolite porphyry and the Madera, Sandia, a.nd Kelly formations and is equivalent to level 9. 

Levels 6, 7, and 8 are reached from it by · inclined 

raises along the dip of the "silver pipe" bed of the 

Kelly limestone, and levels 10 and 11 by an inclined 

winze of north-northwesterly trend also along the 

"silver pipe" bed and nearly parallel to the pitch of 

the main ore zone. Levels 10 and 11 have been extended into the Nitt . mine, where . they are called the 

275- and 350-foot levels. Since 1916 an inclined winze 

down the dip of the "silver pipe" bed from level 11 

has served to open the northern parts of levels 12, 

13, and 14. 

The western ore zone along the Waldo fault has 

been opened . through the Waldo shaft. This shaft, 

the altitude of whose collar is 7,436 fee.t, is just north 

of the Waldo tunnel and about 450 feet from the 

portal. Four levels, equivalent to levels 9, 10, 11, and 

14, have been driven from it, but only the workings 

open on the tunnel level in 1916 have been accessible 

to us. 

The general method of development on each level 

has been to drift along the "silver pipe" bed and to 

drive crosscuts from it through the upper and lower 

parts of the Kelly limestone; but in some places, notably on levels 3 and 5, drifts have been driven for 

considerable distances along or near the top of the 

Kelly limestone. 

The Graphic-Waldo and Nitt niines lie in the large 

relatively uplifted Graphic fault block, which is bordered by rhyolite porphyry on the west and monzonite 

on the north. The formations present include the preCambrian argillite, Kelly limestone, Sandia formation, 

Madera limestone, the Nitt monzonite stock, and dikes 

of monzonite and lamprophyre; but the ore mined has 

come almost entirely from the Kelly limestone supplemented to a small extent by ore from the lower mem-

. hers of the Sandia formation. The general .distribution of the different formations and their exploration 

by mine workings are shown on plates 31 and 32. 

The sedimentary rocks above the argillite dip 45°-50° 

WSW. They have all been metamorphosed to some 

degree near the monzonite contact, and their identity 

is therefore obscured in Nitt workings west of the 

main ore zone; but ~lsewhere they are typically represented, and the only uncertainty in identification is 

where faulting has brought shale beds of different 

members of the Sandia formation together. · 

The Graphic fault block is broken by at least six sets 

of minor faults, nearly all of which are normal. Each 

set appears' to have played some part in the control of 

ore deposition. These different sets have the following 

trends: (1) northwest strike and northeast dip; (2) 

north-northwest to north-northeast strike and vertical 

to easterly dip; (3) east-northeast to northeast strike 

, and southeast di[>; ( 4) east to east-northeast strike and 

south dip; ( 5) east~ southeast strike and northeast dip; 

and (6) bedding faults. Some of these sets could be 

divided into two minor sets on the basis ?f relative age; 

for example, early faults or fissures of northwest trend 

that contain dikes have been offset along normal bedding faults that were formed at the same time as later 

faults of northwest trend. Some bedding faults, in 

contrast to those just cited, may be reverse and may 

have been formed during the earliest stages of deformation. Faults of north-northwest to north-northeast 

trend are grouped' together because their influence on 

ore deposition has been uniform, although, if details 

of deformation could be more thoroughly recognized, 

more than one north-trending set might be recognized. 

The set that has had the greatest influence on ore 
MINES IN THE' MAIN ORE ZONE 127 . deposition strikes northwest and dips 45" or less northeast. The lines of intersection of these faults with the 

west-dipping beds pitch north-northwest at rather 

small angles. The set is well-developed in the Kelly 

limestone, where its dip slips are as much as 30 feet. 

It !passes upward into small monoclines or rolls in the 

basal shale bed of the Sandia formation. These rolls 

have in part absorbed the entire movement, but in some 

places . the sha~e is offset as much as 15 :feet along the 

dip of the :fault. The rolls have not been explored 

upward, so their continuity and relations to minor 

:faults or fissures in quartzite and limestone beds of the 

Sandia formation can only be inferred. The most 

prominent member of this set, called the ·Roll fault, · is 

shown on plates 32 and 33. It extends south-southeastward along the main ore zone :from stopes in the 

Nitt mine to a point on level 8_ of the Graphic-Waldo 

mine about opposite the Waldo tunnel, where it probably ends against a cross fault of east-northeast trend. 

Its northern part especially is closely paralleled by 

s1naller faults that constitute a zone as much as 175 

feet wide that is normal to the dip. (See fig. 12.) A 

steplike continuation of the Roll fault extend-s southsoutheast along the main ore zone on levels 6 and 7, 

but it has not been identified along the old _stopes in 

oxidized ore on level 5. 

A dike o:f monzonite, older than the ore, is exposed 

at intervals on levels 5, 6, 8, and 9. It occupies a 

fissure of northwest trend and moderate northeast dip, 

but it is offset by one or more bedding faults that are 

w. 

related to the Roll fault, indicating that faults of northwest trend and northeast dip wer·e formed at different 

times. ' 

A similar though smaller fault, which is here called 

the East Roll fault, is exposed along the west drift on 

level 5 and lies along the east ore zone of the mine. Its 

trend is more northerly than that of the main Roll 

fault and it is correlated with the north-northwesttrending set of :faults, although in all other respects 

it is similar to the main Roll fault. It ends ag~inst a 

:fault of east-northeast trend a little south of the Greyhound tunnel, and no steplike continuation of it has 

been recognized. ·other faults of north-northwest to 

north trend and · mod€rate to steep easterly dips are 

exposed on levels 3 and 4 and lie witrin the east ore 

zone. 

Only minor :faults of -north to north-northeast trend 

have_been exposed and none have been :followed any considerable distance, although some :form boundaries to 

small stopes in the upper levels near· the incline from 

the Graphic tunnel and in the Ida Hill workings. 

The faults of northeast to east-northeast trend dip 35° ~ 

to 40° SE. anq are nearly parallel to the Kelly-Graphic . 

cross :fault, which :forms the south or southeast bound- , 

ary o:f the major faul~ block. ·Some o:f them are :followed by lamprophyre dikes and others, which are 

mineralized; apparently :form connecting links between 

the east and main ore zones, although ore has not been 

mined along them for any considerable distance except 

near junctions with faults or fissures o:f the other sets. 

E 

-+-- TO SHAFT= ==============·==-= ===== ==== 

~TO SHAFT -=== == ====-==~=~- ~ 

// ~ // 

. /<'/ ' / / / 

/// / //// 

/ / / / 

/ / / / 

/ / -1 / 

,... - -----,L./.--- --,--,- -.Lv!_- - ----- _ __j_-'---- -- _,_, _ -'-'-- _] 

' ' ' ' -

~ [SJ [ZJ ·[2LJ ~ . 

Stop es Fissure "Silver pipe" Coarse-grained Quartzite 

orfau It beds limestone 

Kelly limestone 

50 0 so Feet \, 

:B' IGURE 12.-Generalized cross section through Nitt mine, looking north. By S. G. Lasky. 
128 MAGDALENA MlNII\G lHSTRICT, NEW MEXICO 

The northernmost fault of northeast to east-northeast 

trend is exposed at the top of the incline on level 3, and 

the incline descends obliquely along it. Its presew~e on 

level 2 is expressed by discordant positions of old 

stopes in Kelly limestone to the northwest and southeast 

of it. It is also exposed just north of the old shaft 

that connects level 4 with the Ida Hill workings, and 

its southwesterly projection through the main ore zone 

extends approximately along the interval between the 

stope on level 6 and that on level 8. (See pl. 31.) 

A fault of east to east-northeast strike is exposed in 

the Ida Hill workings, but the exposures are insufficient to serve as a basis for positive interpretation of 

its structural relations. Together with associated 

faults of northerly trend, however, it· appears to bring 

the shale member of the Sandia formation on the south 

down to the same level as the lower quartzite member 

on the north, as shown on plates 31 and . 32. It was not 

recognized on the debris-covered surface; whether it 

extends upward into the Madera limestone or merges 

into bedding faults in the Sandia formation, as is suggested on plate 32, is not known. This fault, if projected eastward, would join the fault just described, 

but it may end against some concealed fault of more 

northerly trend. Other faults with northeast strike 

and southeast dip are exposed on levels 3 and 5 in the 

southern part of the old Graphic workings. With one 

exception the hanging walls of all except the southernmost of these faults have moved downward and northeastward. The southernmost fault was not seen because of the caved and filled ground among the old 

stopes in oxidized ground, but its approximate position 

is suggested by the discordant positions of the Kelly 

limestone, which indicates that the hanging wall has 

moved southwestward. · 

The only noteworthy fault of east-southeast trend 

and northeast dip is exposed in the southern parts 

of levels 6 and 9; its southeasterly projection would 

nearly coincide with the stope at the south end of level 

3. Its upward projection would closely parallel the 

lamprophyre dike shown on plate 2, al?out 1,200 feet 

southeast of the vValdo tunnel portal. 

Bedding faults have been noted along the "silver 

pipe" bed in the Kelly limestone and at several places 

along shale beds in the different members of the Sandia 

formation. Only the fault along the "silver pipe" bed 

near its junction with the Roll f~ult is clearly associated with the distribution of ore, but it may be similarly 

associated near the East Roll fault, and bedding slips 

along the shale bed at the top of the Kelly limestone may 

have similar significance. Where the monzonite dike has 

been offset along the "silver pipe" bed on levels 8 and 

9, near the east end of the Waldo tunnel, its upper part 

with the enclosing upper Kelly beds has moved downdip to the west as if to make room for the roll in the 

shale along the Roll fault, as shown in figure 7 and 

plate 33. Along the southern part of level 9, however, 

particularly where the fault of east-southeast trend 

is· exposed, all the upper Kelly beds are locally eliminated and the overlying shale is in contact with the 

"silver pipe" bed (fig. 3). At the south end of level 

9 the same fault, or one closely parallel to it, is exposed within the "silver pipe" bed. These last two 

exposures seem most reasonably explained Ly either a 

reverse movement of the hanging wall upward to the 

east, opp_9site to the normal movement induced by the 

Roll fault, or by movement in the general direction of 

strike but at a small angle with the dip of the beds. 

The suggested reverse movement could have accompanied the original tilting of the major fault block or 

the folding that preceded faulting, but it could hardly 

have accompanied the subsequent minor faulting. 

Movement in the direction of strike could have accompanied that along the Roll fault. 

Although some of the bedding faults in shale may 

also be supplementary to faults of the roll type, those 

at considerable distance from crosscutting faults seem 

n1ore likely to be related to the reverse movement. 

Thi~ relation seems especially true of a fault in the 

shale member of the Sandia formation exposed in the 

Waldo tunnel about 350 feet east of the Waldo shaft 

(see fig. 3). 

As shown in the general section on structure 

(pp. 65-73) faulting took place at different times and 

the direction of movement along any on~ fault changed 

at different times. The most significant movement that 

affected ore deposition in the Graphic-Waldo mine, 

however, was a settling of the major Graphic fault 

block soon after the intrusion of the Nitt monzonite 

stock. During this settling, which tended to open the 

major faults along its boundaries, the block as a whole 

tended to expand- by the slipping of minor blocks 

within it along the minor faults. The faults with 

north or northwest strikes and northeast dips were 

the most favorably situated to serve as slipping planes 

in the eastern half of the block, and movement along 

them tended to produce tension fractures as well as 

normal bedding faults along the adjacent west-dipping 

bedding planes that were ideally situated in this respect. These open bedding planes and the more open 

parts of the northeastward-:dipping faults, therefore, 

became 'the m~st favored courses to be followed by oreforming solutions. The faults of northeast strike 

and southeast dip . were favorably situated for 

slipping in the southeastern part of the block, but the 

attitude of the bedding did not give so good an opport_unity for associated tension cracks to form adjacent to 

them. These faults, therefore, served mainly to aid 

in the development of open ground near their june.: 

tions with faults of north-northwest to northwest trend, 

especially on the west sides of the junctions; but small 

openings along them may have permitted a minor I , 
GEOIJOGICAL SURVEY 

w. 

Madera. limestone 

------ ~~fi~~~~~h~- --

..340 reet to .south} 

"Silver pipe" bed 

Sa.ndia . formation 

100 o 100 SOo Feet 

(Approximate scale) 

CROSS SECTION OF THE IDA HILL, WALDO, AND GRAPHIC WORKINGS, LOOKING N. 77° E. 

Shows relations of atopes to faults and stratigraphic horizons. 

PROFESSIONAL PAPER 200 PLATE 32 

E. Madera. 

limestone 

1 Kelly limestone : \ I I I 

200889-42 (Face p. 128) 
.· / 

·~ . 

•': ;.( 
GEOLOGICAL SURVEY 

9th level 

Nitt 

LONGITUDINAL 

z~----------------

PLAN 

Ji/!2 I 0 

EXPLANATION 

Stope above 

~ upper"stlver pipe'bed 

Stope below 

~ upper"stlver pipe'bed 

L2.J ~ 

Stope belo w lower"stlver ptpe"bed 

0 100 

.J 

c 

0 

:.3 

() 

Sec.l 

Sec.3 

Sec.S 

PROFESSIONAL PAPER 200 PLATE S8 

Sec. 2 

Sec.4 

IDEALIZED SECTION 

CROSS SECTIONS 

5 =Stope 

Af1er Phtho 8 Argall, wtlh mmor rt"vtstons 

PLAN, LONGITUDINAL PROFILE, AND UROSS SECTIONS OF MAIN ORE SHOOT NORTH OF WALDO T NNEL GRAPTIJC -VfALDO MlNE 
CEOLO .!CAL UR EY 

200-FOOT LEVEL 

E 

N 

EXPLANAT ION 

~ 6~ ~ D "Silver ptpe' sp"l B dd ~ plene, Vein ore Disseminated 

' ' 

limeston faul , nd f•!!sur e or 

py, Pyr•te: c b, copper carbonates; Is, li mestone; lim, limonite; 

qtz, quartz : pee, specul r 1t e nd magnetite. 

!I~J... _ ..___..___,Lo _________ so-' Feet 

K T H 200-A 275-F LEV L 

PROFESSIOI'o:AL PAPER PLATE 34 

275-FOOT LEVEL 

By S.G.La ey, Dec. l, l929 

Til ITT Ml E 
MlNES lN THE MAIN ORE ZONE 129 

amount of circulation between parallel groups of 

northwestward-trending faults. 

The faults of east-southeast strike and northeast dip, 

noted only in the southern part of the mine, were toQ 

unfavorably situated to become slip planes during this 

stage of settling, although they aided in) the formation 

of open ground at their junctions with other · faults. 

The bedding faults, besides being subjected to opening 

along faults of ea.st and northeast dip in the eastern 

half of the block, as stated above, were in position to 

serve as slip planes near the western side. They corresponded in this respect to . the northeast-dipping 

faults in the eastern half of the block. Complementary 

tension fractures across the bedding could have formed 

between bedding faults, but as bedding faults are 

numerous and close together on the whole, the tension 

cracks would have been very short and confined to the 

more brittle beds of limestone and quartzite. They 

would not have provided trunk channels for circulation, although those close to the west boundary of the 

blook could have served as local branch channels for 

solutions that rose along the more open parts of the 

'V aldo fault. 

The ore bodies of the Graphic-Waldo and Nitt mines 

lie in three zones-the eastern or Graphic zone, the 

middle or main zone, and the western or Waldo zone. 

The eastern zone has been developed through the three 

Graphic tunnels but mainly on levels ·3 and 5. Its ore 

shoots are entirely in Kelly limestone, except in the 

west part of level 4, where one small shoot has been 

stoped along a quartzite bed near the base of the 

Sandia formation and near the intersection of northand northeast-trending faults. The or.e mined has been 

mostly lead . carbonate , and zinc carbonate, but some 

rather high grade, partly oxidized copper ore has been 

mined on and below the , southern part of level 5. 

Oxid~tion has obscured the structural relations to some 

extent, but the dependence of the ore shoots on the 

intersection of minor faults with the upper. and lower 

members of the Kelly limestone is generally clear. 

The principal original minerals left along stope walls 

are streaks and thin replacement masses of specu~aritemagnetite with some pyrite and here and there a little 

zinc blende and radiating, platy calcite. 

Many of the stopes are caved or 'filled with waste, but 

in tho~e available for study the character. and distribution of the ore are typical. The lead carbonate had 

been largely mined out by 1905, and in 1915 and 1916 

zinc carbonate was being taken from the floors or walls 

of the old stopes. The copper ore on level 5 lay along 

a bed 18 inches thick in upper Kelly limestone. This 

bed had been replaced by magnetite-specularite aggregates and pyrite, with a little original chalcopyrite and 

a small amount of green copper carbonate. Near the 

south end of level 5, this same bed was replaced by a 

shoot from which some shipments in 1915 were said to 

assay as much as 5 percent of copper. Material seen 

from this shoot consisted of typical magnetite-specularite aggregates with minor amounts of pyrite and 

copper minerals. · About 1905 an enriched shoot was 

followed from level 5 ,nearly to level 6 in a trough 

between the argillite floor an(J. the northeast-dipping 

monzonite dike. It was said to contain lumps of 

native copper "too big for two men to lift." 

The main Graphic tunnel, or level 3, follows a steplike group of east-dipping fissures southward in upper 

Kelly limestone for about 600 feet to their intersection 

with the northernmost fault of northeast strike and 

southeast dip. Along this fault several small stopes 

have been mined at intersections with north-trending 

fissures in both upper and lower Kelly limestone. 

The westernmost of these stopes connects with a narrow, crescent-shaped stope in the overlying quartzite. 

Farther south for. 330 feet level 3 follows along some 

old stopes that extend down to level 4 both above and 

below the "silver pipe" bed. The level then crosscuts 

eastward ~nd follows the "silver pipe" bed southward 

to a point about 100 . feet beyond the Greyhound 

tunnel. The main drift south of the tunnel follows 

the upper Kelly limestone for 400 feet to the first of 

, a group of east-northeast-trending faults that shift 

the Kelly limestone first eastward and then westward, 

as shown on plate 31. The drift follows a sinuous 

course along old stopes in the cross-faulted ground, · 

then follows the "silver pipe" bed to the south boundary. of the mine, near which it is connected through 

an inclined stope with level 4 of the Kelly mine, 30 

feet above the Graphic level3. 

The Graphic No. 2 tunnel, which corresponds to 

level 2, and No. 1 tunnel, which is about 50 feet above 

No.2,· open some old .stopes associated with the northern cross fault. Level 2 is also developed through a 

raise in a stope near the Greyhound tunnel. It contains a few small stopes as far south as its intersection 

with a reverse fault of north~est trend and northeast 

dip. Beyond this fault np ore was noted. 

The middle or main ore zone extends south-southeastward from the monzonite contact in the Nitt mine 

for more than 1,400 feet and practically unites with 

the east zone in the cross-faulted grounl in the south 

part of the mine. The monzonite and metamorphic 

Sandia strata near the north end of the main ore zone 

are impregnated with pyrite and are thoroughly cut 

by a network of slickensided fractures, many of which 

contain pyrite and quartz and a few of which contain 

pockets lined with calcite scalenohedrons. The pyrite. evidently represents little besides the conversion 

of original iron minerals in the rock, and the calcite 

evidently represents redeposition of material that had 

been' replaced and removed from the ore zone. 

The ore extending from the Nitt ground as far south 

as level 6 consists. of specularite-magnetite aggregates, 
130 MAGDALENA MINING DISII'RICT, NEW MEXICO 

sulphides, and m.inor amounts of quartz. On and 

above level 6 it is thoroughly oxidized. The specularite-magnetite aggregates form replacement masses 

along beds throughout the Kelly limestone, particu- · 

lady beneath such impervious beds as the lower and 

upper "silver pipes'' and the basal shale of the Sandia 

formation. Pyrite replaced limestone -that was not 

reached or was only partly replaced by the specularitemagnetite aggregates, and zinc blende and galena replaced limestone that escaped attack by pyrite. The 

specularite-mag~etite aggregates and pyrite are most 

abundant in the northern part of the shoot, but they 

are conspicuous throughout the sulphide zone. Pyrite 

forms large apparently pure masses throughout the 

thickness of the Kelly limestone near the south boundary of the Nitt mine; but farther south it is concentrated mainly beneath the "silver pipe" bed, where it 

constitutes the eastern or copper shoot of the zone 

that had been mined out on levels 8, 9, and 10 in 1916. 

It had not been explored on highe-r levels, but t;he 

position of the enriched copper shoot below level 5, 

about where the east and main zones unit~, suggests 

that the copper shoot of the middle zone may continue 

southward above level 8. The copper ore consists 

largely of pyrite, specularite, magnetite, and a little 

chalcopyrite, somewhat enriched by chalcocite and 

malachite. The base of the Kelly limestone has provided a good course for down ward circulation, and 

thus acounts largely for the enrichment, but it has 

been supplemented by some of the minor faults of 

north-northwest trend along which oxidation has taken 

place lower than elsewhere. 

A small proportion· of zinc ore has been found in the 

copper shoot, but zinc and zinc-lead sulphide ores are 

the principal products of the .middle and western 

shoots. The western shoot, opened on level 10, is in 

the upper Kelly limestone west of a fault that evidently dies out southward or ends against a cross 

f~ult in the northern part of the Graphic-W ~ldo mine. 

The middle shoot is the mo~t continuously developed. 

It has been mined continuously from the Nitt ground 

to a point above level 8 opposite the Waldo tunnel. 

The zinc blende in the middle and western shoots 

forms irreguTar bodies in the pyritic ore near the monzonite contact. The stopes shown on plate 34 and 

figure 12 are largely walled by massive pyrite. 

The steplike continuation of the middle zone was 

being developed on level 7 in 1916. Its outline on 

that level had not been proved, but its outline on level 

6, where it extends upward into ·the oxidized zone, is 

shown on plate 31. Its position on level 5, north of 

its obscure junction with the east zone, is shown by 

a few small stopes in lead -carbonate ore, around which 

some zinc carbonate ore has doubtless been mined. 

The combined east and middle zones appear to weaken 

beyond the south boundary of the mine, which is 

about 200 feet north of the Kelly-Graphic cross fault. 

The main zone also includes a few small shoots in 

the lower limestone member of the Sandia formation 

that have been mined through the Ida Hill tunnel. 

The eastern of these shoots have replaced beds along 

faults of north and north-northwest trends near their 

junctions with one of east-northeast trend and southsoutheast dip that has apparently brought the shale 

member of the Sandia formation on the south down 

· to the level of the lower quartzite member on the 

north. No fault of such magnitude was recognized 

or suspected when the surface in the vicinity was 

mapped, and the interpretation is therefore subject to 

doubt. It accords with evidence on levels 8 and 9 

directly below the Ida Hill workings, as shown on 

plate 32, and with that in the Ida Hill crosscut and 

level 4 to the east; but more accessible workings and 

better exposures in critical places would doubtless 

result in some revision. The western Ida Hill shoot, 

as shown on plate 32, is along the up-dip projection 

of the main Roll fault. Doubtless the fault, or even 

the roll in the basal shale bed, is not continuous across 

the lower quartzite; ·but the presence of some equivalent effects of disturbance may have afforded a somewhat tortuous course along which ore-forming solutions could reach the lower limestone member. The 

western ore shoot, from which oxidized lead and zinc 

ores were mined, was followed by an incline down the 

dip of the formation for about 100 feet where it is 

said to have passed into sulphide ore containing 

copper. _ 

The western ore zone lies near the Waldo fault. It 

is crossed by the Waldo tunnel and has been explored 

through the Waldo shaft, from which three levels have 

been driven below tunne-l level at altitudes of 7,158, 

6,982, and 6,780 feet. Only the workings on the tunnel level have been accessible to us . . The Waldo fault 

in the tunnel is about 150 -feet west of the shaft. Its 

position is obscured by chloritic alteration along slickensided fractures that range in strike from S. 20° E. 

to SE. Some of them dip west or southwest, whereas 

others dip east or northeast. Although the principal 

rock west of the fault is rhyolite porphyry, the rock 

at the contact. with Madera limestone, which lies east 

of the Jault, is 1 a monzonitic porphyry with a chilled 

contact. It is evidently a dike intruded along the 

fault. The limestone adjoining the porphyry is finely 

brecciated and somewhat silicified. The brecciated 

rock passes into_ recrystallized limestone impregnated 

with magnetite, specularite, and pyrite. 

Drifts have been driven northward and southward 

from the tunnel along a shear zone about 30 feet east 

of the contact. The short north drift was timbered 

and only collapsed, slickensided, chloritic rock could 

be seen along it. The south drift is in softened or 

leached, white, crystalline limestone and hard dark-
MINES IN THE MAIN ORE· ZONE 131 

green chloritic rock, both of which are pyritic and 

, thoroughly cut by a network of wet, slickensided fractures. The drift ends at a fissure zone about 5 feet 

wide that strikes N. 65° W. and dips 65° NNE.;_ along 

this zone a small, pipel~ke shoot of pyritic lead-zinc 

sulphide ore has been stoped above and below the level. 

The shoot appears to pitch steeply west-ward. 

The character of the ore is similar to that of the 

main zone. The structural conditions also are similar 

to those that control the small oxidized shoot near the 

south end of level 6. The fact that ore has been deposited in this western zone in the Madera limestone, 

which was presumably rather inaccessible to rising 

solutions because of the shale beneath it, should encourage deeper exploration in the limestone members 

of the Sandia formation and in the Kelly limestone. 

Owing to the abnormally steep dip near the Waldo 

fault, however, the depth that these limestones reach 

in the fault zones and the amount of water tht~tt must 

be handled render mining relatively expensive. Although considerable exploration has been undertaken 

below the tunnel level, the results have not been 

disclosed. 

The depth to promising limestone horizons west of 

the fault can only be roughly estimated. Some drilling has been done there, but we have not learned the 

results. The rhyolite porphyry and underlying volcanic rocks there may have a thickness of 1,500 or 2,000 

feet, and the to:p of the Kelly limestone may be 1,200 

or 1,500 feet deeper-too deep to encourage development under ordinary market ,conditions. 

SMALL TUNNELS EAST OF GRAPHIC TUNNEL 

The No. 2 Graphic tunnel, or level2, which is 150 

feet southeast of the No. 3 or main Graphic tunnel, 

extends 45'0 feet southward in an irregular course; 

and crosscuts extend from its southern end for 150 

feet westward and 200 feet eastward. The tunnel is 

for the most part in 'Pre-Cambrian argillite, but the 

southern . part and the crosscuts penetrate the Kelly 

limestone. The fault of northeast trend that erosses 

the head of the Graphic incline on level 3 evidently 

crosses the southern part of level 2 also and accounts 

for the easterly offset of the Kelly limestone. The 

limestone is also cut . by faults of more northerly 

trend, but the workings are so thoroughly filled or 

caved that no detailed study of them was possible. 

The No. 1, or first-level, Graphic tunnel, also called 

the Gibbany tunnel (pl. 31), is ·about 50 feet above 

and 260 feet east-southeast of the No. 2 tunnel. Some 

low-grade lead ore was being mined from beds just 

below the "silver pipe" bed in 1916. 

The Gibbany tunnel, follows an .irregular southerly 

course for about 200 feet. Its portal is at the top of 

the Kelly limestone, but the tunnel eurves southeastward until it reaches the "silver pipe" bed. It then 

follows the "silver pipe" bed for 100 feet to its intersection with a fault of westward trend and steep northward dip, which offsets the "silver pipe" 50 feet to the 

west. The tunnel turns west along the fault and south 

again along the "silver pipe", which it follows for 35 

feet. North of the west-trending fault the tunnel euts 

a shoot of partly oxidized ,pyritic. copper ore that replaces a bed just below the "silver pipe." The shoot 

has been stoped southeastward obliquely up the dip 

and at the south end of the stope was 3 feet thick. 

Thirty-five feet ~ast of the tunnel the replaced bed is 

slightly offset by a fault that dips east at a· very low · 

angle. The ore as a whole is said to have contained 

4 percent o£ copper and 10 percent of lead, but no lead 

minerals were. recognized in the ore exposed in 1916. 

The "Augustine tunnel, 270 feet east-southeast of the 

Gibbany tunnel, follows a sinuous southerly course for 

about 130 feet (and ·cuts a vertical fault of ·northeast 

. trend in the top of the Kelly ·limestone. A small streak 

of oxidized lead ore was being worked along the shale 

roof on the northwest side of the fault. 

The Tabacchi tunnel, 130 feet east-southeast of the 

Augustine tunnel, is 70 feet long and follows the lower 

Kelly limestone. It has served to take ore through a 

chute from the Martin tunnel stope above it. 

The Martin tunnel, about ' 100 feet long, is in ·upper 

Kelly limestone and follows a fissure that strikes N. 

20 E. and dips 45o E. Thirty feet -from the portal a 

winze has been sunk for 25 feet along the fissure and 

a drift from it extends about 80 ·feet along the intersection of the fissure with the "silver pipe" bed. A 

little ore has apparently been stoped along the fissure 

from the "silver pipe" bed to a point on the surface 

about 25 :feet above the tunnel, but the ore -was 

interrupted in places by rusty gougy material. 

Cook tunnel, 120 feet east of the Tabacchi tunnel, 

is 80 feet long and is entirely in pre-Cambrian argillite. 

The shallow shaft above it has been sunk along a 

vertical fault that strikes N. 35° E. and separ~tes 

Kelly limestone on the northwest from argillite on the 

southeast. A small stope has been mined along the 

fault. 

MITCHELL TUNNEL 

The Mitchell tunn~l, whose portal is 2,300 feet east 

of -North Camp at an approximate altitude of 7,830 

feet, has explored the ground ·east of the southern 

Graphic workings. It is abo~t 930 feet long, trends a 

little north of east, and crosscuts complexly faulted 

ground, as shown on plate 31 and figure '13. Its first 

550 feet is mainly in the lower quartzite-shale member of the Sandia. formation, but the Kelly limestone 

appears at three places, in two of which it is separated 

from the · quartzite-shale member by vertical or steeply 

dipping faults. At the north end of the north drift 

(pl. 31) it 1s also separated by a fault that nearly 

parallels the bedding and partly" removes the upper 

Kelly limestone. For the next 200 feet along the main 
132 MAGDALENA MINING DISTRICT, NEW MEXICO 

NE. 

c 

-~ 

sw. 

100 0 200 Feet ~~~~----~----~ 

Northern extensions of Kelly - Grauhi c f aul t zo ne 

FIGURE 13.-Geologic section along Mitchell tunnel. 

tunnel the shale member o:f the Sandia :formation appears and is stepped down along the east side o:f a :fault 

that dips 32° E. The shale is bounded on the. east by 

the westernmost o:f a group o:f :faults that may be 

regarded as north continuations o:f the Kelly-Graphic 

:fault zone. The Kelly limestone :forms the east wall 

o:f the westernmost :fault and persists as :far as the 

easternmost :fault near the end o:f the tunnel, where it 

is :faulted against pre-Cambrian diabase and argillite. · 

Pre-Cambrian diabase also appears beneath the Kelly 

limestone at a vertical :fault 300 :feet :from the portal. 

The :faults west o:f the Kelly-Graphic :fault zone ·be- . 

long to the prevailing sets, some dipping east at angles 

o:f 300 to 35° and others dipping vertically or steeply to 

· east or west. Both sets are mineralized but contain 

only quartz and a little pyrite and are flanked by 

silicified limestone and pyritized shale, quartzite, or 

diabase. Solutions during the earlier stages o:f mineralization werE< apparently under sufficient pressure to 

penetrate along some o:£ these comparatively tight 

:faults, but the later ore-:forming solutions were not. 

The steep reverse :fault 125 :feet :from the portal is 

an exception, as it contains the quartz-barite aggregate that is characteristic o:£ the later or weaker stage 

o:f ore deposition. A little ore may have been stoped 

along its eastern or hanging side. This :fault evidently 

marks the east limit reached by the solutions that 

deposite~ ore In the southern part o:f the Graphic- "T aldo mine. 

KELLY MINE 

The Kelly mine, including the Paschal, Traylor, 

and old Billings sha:fts and the Kelly tunnel (pl. 35), 

owned by the Empire Zinc Co., is just northeast o:f the 

town o:£ Kelly. The company at first owned only the 

Lillie group o:f claims west o:£ the Kelly mine but in 

1913 purchased the mine and mill :from the TriBullion Smelting & Development Co. The property 

now consists o:f 40 claims, covering 578 acres.81 

Intensive development was begun in 1913, and improvements 'were made in the combination wet concentration, 

roasting, and magnetic concentration mill; but the 

milling process was not altogether successful, partly 

because the gangue contained sufficient iron to prevent 

its electromagnetic separation :from the zinc blende. 

The company reported 82 that during the years 1915-17 

zinc ores were produced at some profit above operating 

expenses, not including amortization o:£ capital invested. At the end o:f that period the main sulphide 

ore body o:f the mine, which bottomed near level 6, 

was practically exh'austed. Meanwhile developments -

on lower levels had disclosed very little ore; so company operations ceased, though some leasing continued. 

The mine was idle in 1921 and 1922, and the company's 

report, cited above, stated that all known pay ore had 

been removed; it also stated that there was "a possibility o:f zinc ore on property not prospected but the 

prospects have been deemed so unfavorable that nearly 

all equipment has been removed :from the property and 

the plant buildings scrapped." Since 1922 lessees 

have made small outputs, mainly o:£ lead, but in 1930, 

1933, and 1934 they produced :from 1,000,000· to 

2,000,000 pounds o:f zinc, as well as :from 447,000 to 

915,000 pounds o:f lead, annually. 

The output o:£ the mine :from 1905 to 1939, inclusive, 

is shown in the accompanying tables. The second table 

contrasts with the corresponding table :for the GraphicWaldo mine in the sm~ller relative quantity o:£ copper 

ores and in the dominance o:f zinc-lead sulphide instead 

81 Finlay, J. R., Report of appraisal of mines in New Mexico: New 

Mexico State Tax Commission, 1921-22, p. 53, 1922. 

82 Idem, p. 53. 
MlNES lN THE MAIN ORE ZONE 133 

of zinc sulphide ore. The bulk of the copper and gold 

credited to the mine in the first table came from lead 

ores and lead concentrates. The low silver content of 

the lead ores and the prevailingly high .grade of the 

.oxidized zinc ores are common to both mines. 

Ore shJi pped from Kelly mine, 1905-39 1 and its gross metal 

content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of 

Mines, U. S. Department of the Interior, Denver, Colo.\] 

Year Ore Gold Silver Copper Lead Zinc 

(tons) (ounces) (ounces) (pounds) (pounds) (pounds) 

- - - - ---- ---- - - - ----- 1905 __ _______ ___ 4, 496 ---- ------ ---------- ---------- ---- -- ------ 2, 805,060 

1906_- ---------- 27,300 ---------- --------·-- ---------- (2) 18,775,500 

1908 _ ----------- 4,375 - --- - - ---- ---------- ---------- ------------ 3, 675,000 

1909- --- -------- 28,893 15,684 276, 942 3,429,126 14,911,185 

1910 _- ---------- 35,393 12. 77 61,544 181, 479 3. 769,288 16,663,665 

191L ----------- 22, 351 14.01 40, 842 258,924 2, 158,688 9,128, 576 

1912 _--- -------- 16, 736 35. 25 31,915 66, 143 2,058, 581 7, 417,328 1913 ________ __ __ 10,540 26.18 14,761 151,742 1, 281,568 3,652,297 1914 ____ ___ __ o __ 68 ---------- ---------- ---- ------ ------------ 55,109 1915 ___ _____ ____ 9, 449 1.60 13, 504 37,241 1, 431, 709 3, 756,257 1916 ___ ______ ___ 28, 416 31.76 16,202 71,495 3, 016,524 10,189.162 

Ore shipped from Kelly mine, 1905-39 1 and its gross metal 

content-Continued 

Year Ore Gold Silver Copper Lead 

(tons) (ounces) (ounces) (pounds) (pounds) 

1917---------- -- 24, o06 15.26 9,309 113,529 3,019, 591 

1918_ --------- -- 4, 528 1. 00 11,899 98,130 943,061 

1919------ --- --- 1, 179 .48 4, 557 11,319 343,340 1920 ____ _____ , __ 446 511 3,228 31, 799 1923 __ __ ________ 318 5.40 1, 624 6,497 126,141 1924 __ ___ ___ ____ 682 2, 515 4, 584 249,974 1925 ___ ______ __ _ 748 32. 10 4,232 6,649 319,934 1926 __ ______ ____ 471 4.08 2,015 3,389 149,814 

1927------------ 1,186 1, 365 2,300 127, 439 

f~~ = === === ==== = 

3 598 3. 70 1, 702 5,674 194,767 

2,366 7. 10 8,169 19,418 823,067 

1930_- ---- ------ 4,533 3. 00 4,908 10,667 1, 111, 518 

1932_- ---------- 622 ---------- ---------- -- - ------- 155,800 

1933 __ - - -------- 5, 501 ---------- ---- ------ 1,307, 660 

1934_- ---------- 3,129 -- - - - ----- ---------- ---------- 639,028 

1935_ --- -- ---- ~ 1,957 ---------- ---------- ---------- 350,280 

1936 _- -- -------- 1, 571 ~ --------- ---------- ------ ---- 248,012 

1937- ----------- 962 2. 90 3,354 5, 903 172,985 Hl39 _________ ___ 713 485 ---------- 126,217 -------- 244,133 196. 59 251,097 1, 335,253 27,585,911 

t Mine idle 1907, 1921-22, 1931, and 1938. 2 Contained undej;ermined amount of lead-. 3 All from dump. 

Zinc 

(pounds) 

8, 365,424 

1, 401,340 

342,314 

234,330 

41,012 

------ ------ 31,950 

------------ ------------ ------------ 238,368 

1, 718,534 

290,720 

2, 515, 540 1,363, 801 844,560 

682, 097 63,734 

227,138 

109, 390, 001 

Classes and average gross metal content of ore shipped from Kelly mine, 1905- 39 1 

J Data collected and classified by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Sulphide ore Oxidized ore 

Copper ore Lead ore z Zinc-lead ore Copper ore Lead ore 2 Zinc ore 

--- ---- ---- -------- --------------------- -------- Year 

~ -;:; as~ -;:; ~ -;:; -;:; -:= gs'a' -;:; ~"a' -;:; ~~ -;:; ..., 

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~ ~§:: C) 

~§ C) 8 ;:l..., C) 

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.£ 0."" "0 ... ~a> o>=lolo ~ 1~~~ ~::l ... ~a> 0."" 1i>::l ... a>'-' ~oa> p.<l> a>O ~oa> ol<l> ~8. C)Q) c;><l> ~oa> a>O ~oa> p.<l> a>Q ~oa> a>O C)Q;I 

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1905 _________ ------ ------· ------ ----- -- - ------ ------ -- ------ -- --- - ------ ---- ---- ------ -- ------ ------ -- ---- --- ----------- ------ -------- ------------ 4,496 31.2 1906 __ __ ·____ ------ ------ ------ -------- -- ---- ------ 3 5, 575 ------ ------ ---- ---- ------ -- ------ -- -- -- -- -- -- ··--- ---·· -----·- -- ---- -- ------ ------ ------ 21,725 34.4 1908 __ __ ____ ------ ------ ------ -------- ------ ---- -- 375 11.7 4125 35. 0 ---- ---- ---- -- ------ -- ------ ~- --- ------ -------- -- ---- ------ 4 4,000 35. 0 1909 ___ __ __ _ ------ ------ ____ __ -------- --- --- ______ 3,444 12.6 4. 4 1,H8 37.7 ___ __ ___ ------ ____ __ __ ________ ___ _ __ ___ _ -------- ___ ___ ______ 25,449 27. 6 

1910 ________ ------ ------ -- ---- ---··---- ·----- ------ 519,605 21.6 7.0 11, 062 38.4 4,622 10. 9 29. 9 -------- ------ ------ 63,000 3. 9 20 6J2,788 39. 0 1911_ ____ _ ------------ --------------------- ------116,333 18.5 5.3 7,800 38. 6 1,390 19. 0 48. 0 --·--- ·----- ------ 1,135 4.4 19. 5 4,883 31.8 1912 _____ ___ ------------------ -- ------------ 15,040 21.7 6.5 8, 664 37.6 3,369 . 8.7 29.2 36 --· --- 4.5 259 10. 2 17.1 1, 401 32. 4 1913 ____ ____ ---- -- ------ ·----- -------------- ·----- 8,200 18. 5 7. 7' 4,086 37. 1 2,479 4.7 25.5 1.503 2.2 4. 5 -------- -- ---------- 837 37.0 

1914 ___ _____ ---- -- -- ---- --- --- ----- --- ------ ------ -------- ------ ------ · ------- ------ -------- ------ ------ -------- ------ -- -- -- -------- ------ ------ 68 40.5 1915 __ ____ __ ------------ ---- -- -··------ ------ -------------------- ·----- -- ------------ -------------------- -------- -· -- -- -- -- -- 3,100 4.3 23. 1 6, 349 29.6 

1916 ___ ____ _ L === ==== == ===== = ---~~ ~~~ -~ ~~ ~- 10 ~: ~~~ ~iJ 1i: g _

9

_ ~: ~~~ . . ~~~= =~==== ==== == == ==== . -- -~~ ___ ~ ~- -~~: _ -=~ =~~- -~ ~ ~~ ·=~~~=~ -- ~~ ~ 1917 ________ 29 2. 0 7. 5 ---- -------- -- -- ·--· 17,904 16. 1 6.5 ll]4,057 20.5 30 15.7 44. 1 67 2.1 12.5 2,115 4. 1 16.5 4,491 29.0 

1918 ____ ____ 404 3. 3 6.9 12'1, 995 5. 3 22. 8 -------- ------ ___ _ ·__ -------------- -------------- ---- -· ----- - ------------------ -------- ------ -- 132,045 33. 4 

1919 .. ------- ··----- ------ "--- -- -------- - ----- ------ ------ -- ------ ------ -------- ------ -------- ---- -- ------ -------- ---- -- ------ 680 6. 7 25. 2 499 34. 3 1920 __ ______ ------ ------ ·- ---- -------- -- ---- ------ -------- ---· -- ------ -------- ------ -- -- ---- ---- -- ------ ------ -- -- · --- --- --- 81 6. 3 19. 6 365 21.1 1923 ________ ------ ------ ------ ---·---- ------ ------ -------- ------ ------ -------- ---- -- --- ------ ------ ------ ------ -- --- -- - ------ 259 6. 3 24.4 59 34. 8 

1924 _ ------- ------ ------ ---- -- -------- ------ ------ -------- ------ ------ -- -- -- -- ------ -------- ------ ----" - ------- - ------ ---- -- 682 3. 7 18.3 ------ -- ------ 1925 __ ______ ------ ------ -------------- ·----- ------ 1428 57.0 5.9 --------------- -- ------ ------ ------ -- ------ ------------ 720 5.9 22. 0 -------- -··---- 1926 ________ ·----- ------ ------ ------ ·- ------ ------ -------- ------ ------ ---- · --- ------ -- ------ -- ---- -- ---- ------ -- ---··- - ------ 15 471 4.3 15. 9 ---- ---- ------ 1927 _______ _ ------------------ -------- ·----- ------ -------------------- -------- __ · ___ _ -------------- ___ __ ·_ ------·- ------ ____ __ 161, 186 1.2 5.4 ------------- -- 1928 ___ ___ __ ------ -- ---· ·----- ------ -- ·-- -·· - --·--- -------- ------ ------ ---- ---- ------ ·-------- ------ ------ __ ,. _____ ------ ------ 17 598 2.8 16.3 - ----- --- -- -- -- 1929 ______ ___ ------ ---- ·-- -------------- -- ---- -- ---- H497 24.0 14. 9 ------ -- __ ____ -------------- ------ ____ ___ __ _____ ------ 1,869 4. 4 18. 1 --- --------- -- 1930 __ ____ __ ------ ------ ---- -- ---- ---- --- --- ------ 14 3, 423 2.5. 1 11.9 -- ------ -- ---- -------- ---- -- -----· -- ----- _ _. ____ ------ 1,110 4. 4 13. 4 ·------- ------ 1932 ___ _____ ------ --·---- ------ -------- ------------ 14622 23. 4 12.5 -------------- ____ . ___ _ -------------- ------ -- -- ------ -- --------· ------ ------ -------- - --- --- 1933 ______ __ ----··- -- ---------------- -- ---- -- ______ _ 14 5,501 22.9 11.9 -------- ··- ---- ---- -- ·- ------------ ·· ·- ------ ----- - -----·· -------- ----·-- ---- ---------------- 1934 ____ ____ ------ ------ ------ ------- - -- ---- -- -- -- !4 3,129 21.8 10. 2 -------- ------- ---- ---- ------ ---- --. -------- ---- -- ------ -------- ------ ------ --- ----- -----· 1935 _____ ___ ------ -- ---- ------ -------- ------ ------ H 1, 957 21.6 9. 3 -------- ------ -------- ____ __ ------ ---- ---- ------ ------ -- -- ---- ------ ------ -------- ------ 1936 _____ ___ ------ ------ ------ -------- ------ ---- -- H 1, 571 21,7 7. 9 -------- ------ -------- -- ---- ------ ---- ---- ______ ------ -- --- ------ ------ -------- -- ---- 1937 ___ _____ ------ ------------ 18 680 4.9 11.4 282 11.3 3. 1 -- ------ -------------- -- ---------- -- -- ---- -- ---------- ---- ---- -------------------- -- --~ 

1939 -------· ------ ------ ------ 19144 3. 4 23. 1 569 20.0 11.1 ---- ---- ------ -------- ------ ------ -------- ------ ------ -------- ------ ------ -------- ------

TotaL 433 -- ---- ____ __ 5,344 ____________ 117, 819 ---~ ---- ·- ·---·--· ____ __ __ ___ ___ ______ ___ ___ 1,fJ35 _____ _ ______ 18, 450 __ ____ -----" 100,368 __ ___ _ 

1 Mine was idle during 1907, 1931, and 1938; no ore was shipped during 1921 and 1922. 2 Lead ores, both sulphide and oxidized, and lead concentrates contained from 0.03 to 2.0 percent of copper and as much as 0.04 ounce of gold to the ton. a Zinc-lead ore in 1906 contained 32 percent of lead and zinc and was evidently shipped to zinc-oxide plants. About ~ of the total recovered zinc for 1906 was used as pigment. 

4 Shipments of zinc concentrates and crude oxidized zinc ore averaged 35 percent of zinc. ' • Original metal content of crude ore calculated from metal recovered from con- centrates. 

~ Tonnages approximate, based on pounds of recovered metal from a total of 15,788 tons of lead and zinc ores shipped separately. Lead ore shipped by C. T . Brown, 

lessee, contained 2.9 ounces of silver to the ton, 9.2 percent of copper, 22.3 percent of 

lead, and 21.5 percent of iron. 7 2,710 tons of iron middlings containing 38 percent of iron was also produced from 

this crude ore. · · 

8 Includes 35 tons of lead-copper ore containing 4.2 ounces.of silver to the ton, 4.6 percent of copper, and 7 percent of lead. 9 Contained 8.3 percent of lead. 10 Slimes from old Tri-Bullion mill, which was operated in 1908--13. u Contained 8.2 percent of lead. 12 Includes 95 tons of lead-copper ore. 13 Does not include 84 tons of oxidized zinc-lead ore containing 21.0 percent, of zinc and 15 percent of lead. u Zinc-lead ore shipped crude to zinc-oxide plants. u Consists of 300 tons of crude ore and 171 tons of concentrates. 16 Includes 1,000 tons of crude ore reduced to 115 tons of concentrates that assayed 7.7 ounces of silver to the ton, 1 percent of copper, and 43.5 percent of lead. 17 Ore from dump only. 18 Contained 0.004 ounce of gold to the ton and 0.4 percent of copper. 19 Contained 0.6 percent of copper, 

I . 
134 MAGDALENA MINING DISTRICT, NEW MEXICO 

Horizontal and vertical scale o 5o 100 200 feet 

FIGURE 14.-Cross section (B- B' on plate 36) through Traylor shaft of Kelly mine. After Soren Ringlund. 

w. 

-t + t 1' -t + t 

+ 1" . t 

+ t + 

+ + t 

Shal e Limestone 

Argi H ite 'i5reenstone" 

100 

D . 

+ 

+ 

Volcanic rocks 

0 

I 

. 

Kelly limestone including" silver pipe"bed 

White porphyry dike 

200 Feet. 

FIGURE 15.-Cross section along level 10 of Kelly mine, west of Traylor shaft. After C. M. Glasgow and R. G. Garnett. 

E. 
MiNES IN THE MAiN ORE' ZONE 135 

w. 

EXPLANATI 0 N 

fti{:fHJ Alluvium 

] ~~ Sha le ember i :! ~:::: ~~.:::::: :::::: .?>~ {B"Upper crys~.alline limeston.e w~ Sl!verp1pe ~ ,§ Lower crystalline limestone 

B"Greenstone" 

E. 

100 0 100 Feei 

Altitude 

e,ooo· 

7,900' 

7,800' 

7,700' 

7,600' 

7,500' 

7,400' 

FIGURE 16.- Cross section (A- A' on plate 36) through middle part . of Kelly mine. Shows relations 

of lead-carbonate and zinc-carbonate ore shoots. After Soren Ringlund: 

Yhe mine (pl. 36 and figs. 14-16) is opened by the 

Kelly tunnel, which corresponds to level 3, and by 

three shafts, two of which-the old Billings and the 

Paschal-had been abandoned before 1915. The old 

Billings shaft, 200 feet e~st of the portal of the Kelly · 

tunnel, extends only to level 4; the Paschal shaft, 750 

feet to the northwest, extends· to level 7; the Traylor 

shaft, 7.00 feet southwest of the Kelly tunnel, is connected with levels 7 to 10. All the levels except level 

10 are developed mainly in the Kelly limestone, and 

most of the main drifts are along the "silver pipe" bed. 

Level 10 (fig. 15) consists of a long crosscut that extends westward for about 1,150 feet, ·!partly through 

argillite and Kelly limestone but mostly through the 

Sandia formation, and into the volcanic rocks beyond 

the Waldo fault. A winze from level 10 has been sunk 

about 380 feet in the volcanic rocks, and an east crosscut from it crosses the fault and enters the upper 

Kelly limestone. 

The· Kelly limestone in the mine has been subdivided 

for local purposes into the following members, beginning with the lowest: (1) a 6-inch layer of pebbly~ 

arkose in a calcite matrix, (2) a few feet containing 

much quartz and epidote (the "pinto lime") , ( 3) 

coarse-grained "lower crystalline" limestone 70 to 80 

feet thick, which includes a bed of fine-grained, white 

("marbleized") limestone 1 to 4 feet thick, (4) the 

/ 

dense, argillaceous "silver pipe" bed, 1 to 6 feet . thick 

about 20 feet above the "marbleized lime", ( 5) the 

"upper crystalline lime" 45 feet thick, which is divided 

near the middle by a "west" or "upper silver pi'Pe" 

bed about 2 feet thick. In places, however, especially 

in the west-central part. of the workings, the "upper 

silver pipe" is immediately below the basal sh~le of 

the Sandia formation, perhaps as a result of faulting 

along the bedding. The principal ore"'bearing~ strata 

are below the "marbleized lime'' and below the main 

"silver pipe"· bed. The "U!pper crystalline lime," very 

productive in 'the Graphic-Waldo mine, has been less 

!productive than the "lower crystalline lime'' in the 

Kelly mine, partly because' it has been eroded from 

the southern part of the mine. 

The productive ground is in the eastern part of the 

Kelly fault block (p. 71), which is bounded on the east 

by the Kelly-Graphic fault, on the north by the KellyGraphic cross fault, on the west by the Waldo fault, 

and on the south by a cross fault, mostly concealed, 

· that joins the Kelly-Graphic fault a little south of the 

Juanita tunnel. This block has dropped in relation 

to the block east of it and also to the block north of it, 

but the blocks south and west of it ·have dropped much 

more. The Kelly block is cut by sets of minor faults, 

of which four are normal, one is reverse, and one follows the bedding. The set having the most marked 
136 MAGDALENA MINING DISTRICT, NEW MEXICO 

influence on ore deposition is the normal set of northnorthwest trend and vertical to steep westerly dip. It 

is slightly convergent southward with the east boundary, or Kelly-Graphic fault, and includes the Brown 

fault, which is 120 to 130 feet west of the KellyGraphic fault and is the axis of the ore zone. A 

second normal set is of east-northeast trend and southerly dip, generally parallel to the north boundary or 

Kelly-Graphic cross fault. The members of this set 

between the l{elly-Graphic and Brown faults have 

served as minor channels for the circulation of oreforming solutions. A third set, of west-northwest to 

west trend and northerly dip, is similarly related to 

ore deposition. A fourth normal set, of northwesterly 

trend and n@rtheasterly dip, is conspicuous west of the 

ore zone but is only slightly mineralized. Only two 

reverse faults have been noted, both in the west crosscut on level 10, where their relations to other faults 

have not been determi~ed. The outstanding bedding 

fault is along the "silver pipe" bed. It has offset a 

lam,prophyre dike west of the ore zone, the hanging 

wall showing an apparent movement of 38 . feet down 

the dip (fig. 16) ; but the actual movement here, as in 

the Graphic-Waldo mine, was probably for the most 

part along the strike of the bedding. Some of the 

no·rmal faults are followed approximately by lamprophyre dikes. (See pl. 36.) Small movements along 

the normal faults have recurred since the intrusion of 

the dikes and both before and since ore deposition. 

The movement that provided openings for ore-forming solutions was principally down the dip of the 

Kelly-Graphic cross fault. It involved some southerly 

movement along the longitudinal Kelly-Graphic and 

Brown faults, whose curvature, as shown in figure 6 

and plate 36, caused ·all but their northernmost parts 

to open. The cross faults 'between them also opened. 

Some settling toward the Kelly-Graphic· and Brown 

faults must have taken place along the northeast-dipping faults whose relatively low angles of dip evidently 

kept them tight. In this respect they are in marked 

contrast to the Roll fault in the Graphic-Waldo mine. 

The ore-forming solutions evidently rose from a deep 

source into the northeast corner of the Kelly block and 

moved through the open ground along the KellyGraphic and Brown faults.' There is no evidence that 

they came southward from the Graphic block, as the 

ores in the southern part of that block contain barite 

and were deposited farther from their source than were 

the northernmost Kelly ores which contain considerable 

specularite, magnetite, and some silicate gangue; 

Specularite and magnetite have been found as far 

south as crosscut 3 on the Kelly tunnel level, and they 

may have extended somewhat farther in ground that ( 

is now thoroughly oxidized; but ore in the southernmost part of the mine and in the Juanita workings 

beyond contains considerable ba~ite. 

Ore bodies in the Kelly mine are essentially confined 

to one zone along the eastern part of the Kelly block. 

Development in the middle part of the block has disclosed only small occurrences of ore, and that along the 

Waldo fault at the west edge of the block has also had 

discouraging results: The ore zone crops out at the 

Kelly -Graphic fault on the north slope of Kelly Gulch. 

On the lower slope the upper part of the Kelly limestone has been eroded, exposing lead carbonate, allophane, and zinc carbonate, which have replaced the 

lower part. TP,e outcrops of both the upper and lower 

parts were developed first by shallow tunnels along or 

near the fault, and their down-dip continuations were 

later reached through the Kelly tunnel (level 3) and 

the Billings shaft, which extends to level 4. Development of the upper part led to the Big Twenty stope, 

where loose "sand carbonate" was tapped and, according to the late C. T. Brown, flowed down to level 3, 

where many tons of it had merely to be shoveled into 

mine cars. This ore, which was mined in the early 

eighties, contained about 20 ounces of silver to the 

ton-much more than the average lead carbonate ore 

of the district. The associated zinc carbonate was not 

mined until 1903, or later, after it had been recognized 

by Brown. The relative positions of the lead and zinc 

carbonate ores in and beneath the Big Twenty stope 

and in the lower Kelly limestone on either side of the 

Brown fault are shown in figure 16. 

The stopes accessible in 1915 and 1916 are shown on 

plate 36. The oldest stopes, which extended for nearly 

500 feet northward from the Kelly tunnel along level 

3, are filled and inaccessible ; but, together with the 

stopes mapped, they represent an almost continuous 

replacement of the more permeable beds. Beyond the 

filled stopes on level' 3 the sulphide ore appears. 

The ore zone, which widens northward in. accordance 

with the diverging trends of the Kelly-Graphic and 

Brown faults, has a general steplike or zigzag outline 

that has been influenced by cross faults, whose positions 

are indicated by branch stapes of southwest trend. For 

about 400 feet north of the Kelly tunnel the ore zone 

is almost entirely between the Kelly:.Graphic and 

Brown faults. · It is widest in the vicinity of southwesttrending cross faults near crosscut 4 on level 3, but 

farther north the ground between the two faults has 

not been very productive. The principal shoot north 

of crosscut 5 extends with north-northwest pitch along 

the west side of the Brown fault and ends abruptly 

between levels 4 and 6 against the Kelly~Graphic cross 

fault, whose footwall is argillite. Beneath level 6 a 

short west branch of the shoot extends southward from 

the Kelly-Graphic cross fault, and a veinlet follows the 

cross fault for a considerable distance. Farther south 

short branchef? of the ore shoot that have been mined 

along _minor cross faults extend nearly down to level 6. 

The ore south of crosscut 4 on level 3 was entirely 
-

GEOLOGICAL SURVEY PROFESSIONAL PAPER 200 PLATE 35 

SURFACE PLANT OF KELLY MINE IN 1916, LOOKING NORTH. 

Traylor shaft in left foreground; ore bin and dump of Kelly tunnel in right foreground. High slope on left is capped with cliff-forming beds of Madera limestone. Lower quartzite member of Sandia formation crops out above ore bin on extreme right. J,evel-topped central area represents pediment F. 

MINES IN THE MAIN ORE ZONE 137 

oxidized. In some places, particularly near the outcrop and in parts of the Big Twenty-stope, considerable 

oxidized copper ore was mined near the Kelly-Graphic 

fault. The fault itself was filled with leached quartz, 

which had also replaced the adjacent limestone beds 

to some extent. Similar quartz, with some barite and 

calcite, was found along some of the minor cross faults. 

The only metallic minerals remaining are remnants of 

specularite-magnetite. The ore on the west side of the 

Brown fault and below level 3 is massive sulphide, 

·largely zinc blende with minor amounts of galena, a 

little visible chalcopyrite and pyrite, and considerable 

specularite and magnetite. There is no change in its 

content of pyrite that corresponds to the change in 

the Nitt-Waldo workings. Any original pyritic ore 

was evidently near the quartz veins where the oxidized 

copper was found. Such a restricted position would 

strengthen the impression that the ·principal channels 

into which the solutions ro~e were along the shake~ 

grou~d where the longitudinal and minor cross faults 

intersect. The stopes in the southwest branch east of 

the Paschal shaft and at the Kelly-Graphic cross fault 

show how far ore was deposited in commercial amounts 

west of the main zone of shaken ground. 

Along the northern part of . level 6 north of the 

Paschal shaft the upper Kelly limestone is somewhat 

impregnated with sulphides along minor fractures, and 

near the south end of level 6 (pl. 36 and fig. 14) a little 

ore has been mined near the junction ·of a vein of south-· 

erly trend and a fault of southeasterly trend. The 

north end of level 7 exposes a small mineralized fissure 

where the "silver pipe" bed reaches the Kelly-Graphic 

cross fault. A similar but more encouraging showing 

was found on level 8 about 400 feet northeast of the 

Traylor shaft, but water a few feet below the level 

had retarded its exploration prior to 1916. Farther 

south on level 8 a small amount of mineralized 

ground was exposed west and south of· the main ore 

shoot. (See figs. 14 and 16.) 

The large ore shoot on the highest levels ends southward against a dike~one of the "faulting dikes"~that 

follows a n1inor cross fault or fissure. A little ore 

has been found south of it along fissures on level 3 

(fig. 16)., which is there very close to the surface; but 

no continuous stopes had been found prior to 1916, 

although the ground was in line with the Juanita ore 

zone to the south. The "faulting dike'' or its steplike 

continuations have been cut on levels 4, 6, 7, 8, and 9 

(pl. 36), and the "silver pipe" bed has been followed 

for several hundred feet south of it on levels. 7, 8, and 

9. A quartz vein was found in the lower Kelly limestone near the south end of level 7, along a . minor 

longitudinal fault; and some sulphides and calcite have 

been found in an oblique fissure along the "silver pipe" 

bed west of it. The structural setting of this ground 

200889-42-10 

is similar to that in the southern part of the main ore 

zone, but the ore-forming solutions that n~ached it 

were ·weak. A little oxidized ground with zinc carbonate was found along the fissure at the extreme 

south end of level 7. A little ore has also been found 

in the southern parts of levels 8 and 9, but its character is that of ore deposited by solutions that have 

traveled rather far from their source. 

The crosscut on level 10 was driven to explore the 

vValdo fault, along which the west ore zone of the 

Graphic-Waldo mine was formed. The fault had been 

cut in 1916 (fig. 15), showing purple andesite on its 

west wall, and the lower quartzite, shale, and limestone 

beds of the Sandia formation on the east wall. Since 

then a winze was sunk about 380 feet in the volcanic 

rock and a crosscut driven about 120 feet eastward, 

cutting the fault and entering the upper Kelly limestone; but no discovery of ore has been reported. 

The development of the mine leaves little unexplored 

ground worthy of consideration. Work in the Kelly 

limestone shows no noteworthy ore zones except that 

near the Kelly -Graphic and Brown faults. The ore 

mined in 1929-39, so far as known, has come from 

·that zone. The Sandia strata are largely eroded above 

this zone except in the northernmost part of the mine, 

where the wedge of ground near the junction of the 

Brown fault and Kelly-Graphic cross fault is rather 

favorably situated. It may be that solutions could 

r~se above the Kelly lin1estone -along the Brown fault 

or its branches and form small .ore shoots in the overlying quartzite and limestone beds, as they did in the 

Graphic-Waldo mine. These beds, so far as known, 

remain unexplored, and the thick covering of shale 

above them may readily conceal any superficial evidence of ore deposition. 

JUANITA MINE 

The Juanita mine, owned by former Senator T. B. 

Catron, of Santa Fe, and leased from 1~15 to 1928 to 

the Mines & Metal Co., of Kelly, is in the Mamie Lode 

claim (pl. 36) in the southeast part of the Kelly fault 

block, south of Kelly Gulch. Although the mine has 

been active in almost every year for which records of 

output are available, its total output, sl;l<;>wn in the 

accompanying ·tables, has been small. According to 

these tables the output has consisted almost entirely 

of lead ores, 'both oxidized and sulphide, and oxidized 

zinc ore, supplemented by a few small shipments of 

zinc-lead and zinc sulphide ores and dry silver ore. 

The grade of the oxidized zinc ores is similar to that of 

the Kelly and Graphic-Waldo ores, but the lead and 

silver contents of the lead ores have been generally 

lower. The copper and gold credited to the mine in 

the first table has come from the lead ores. 
138 MAGDALENA MINING DISrrRICT, NEW MEXICO 

Ore prod'ucerJ at J uanita mine, 1905-37/ and its gross metal 

content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of 

Mines, U. S. Department of the Interior, Denver, Colo.] 

Year Short I Gold Silver Copper Lead Zinc tons (ounces) (ounces) (pounds) (pounds) (pounds) 

--- 1905_ ----------- 750 ---------- 2,800 ---------- 321, 160 175,000 

1906_-- --------- 1,210 ---------- 2, 515 ---------- 223,194 568, 750 

1907------------ 200 --------- - ---------- ---------- ------------ 152,000' 

1908_ ----------- 100 ---------- ---------- ---------- ------------ 64,000 

191L ----------- 590 ---------- 83 803 8, 657 416, 178 

1 912_----------- 4,468 0. 24 302 1,106 51,089 3, 148, 666 

1913 _ ----------- 2,989 2. 71 2,341 3,197 333, 050 1, 646,809 1914 2 ___________ 1,617 -- -------- ---------- ---------- ------------ 1, 135,682 1915 2 ______ _ ____ 1,313 7.47 514 1,877 106,979 757, 131 1916 2 ____ ___ ____ 1, 486 1.00 881 4, 214 158,644 694,634 

1917------------ 1,047 1. 90 2, 816 10,759 329,652 186,504 1918 2 _______ ____ 1,073 3.50 777 5,673 164, 387 386,543 

1919_--- -------- 546 ---------- 214 422 34,395 259,994 

1920_ ----------- 189 ---------- 300 694 49,115 43,444 

1923_- ---------- 623 1.40 1,468 3,464 376,776 73,442 

1924 _ ----------- 700 ---------- 2,025 4,906 270,304 ------------ 1925_-- --------- 1, 308 .80 3, 093 8, 764 674,656 ------------ 1926 _- ---------- 1, 287 .40 917 1, 908 239,663 457,080 

1927------------ 128 . 70 172 245 26,381 43,908 

1928 _- ---------- 25 ---------- ---------- ------- --- ------------ 15,000 

1929 ------------ 537 3.09 1, 220 5,479 209,134 ------------ 1930 ____________ 397 . 80 535 1, 674 99,601i ------------ 1937-- ---------- 175 ---. 90 379 857 67,389 ----------··- - - - 22,758 24.91 23,352 56,042 3, 744,230 10,224, 765 

1 No returns on file for 1909 and 1910. Mine idle 1921-22, 1931-36. 2 May include 161 tons of oxidized zinc containing 91,448 pounds of zinc from Ambrosia mine in 1913; includes 121 tons of oxidized zinc ore from Ambrosia mine in 1914 and small outputs of oxidized zinr. ore in 1915, 1916, and 1918 from same mine. 

Glasses and average gross metal content of ore shipped from 

JuanUa mine, 1905-37 1 

[Data collected and classified by C. W. Henderson, Geological Survey and 

Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Sulphide ore Oxidized ore 

Lead orez Zinc-lead ore Lead ore 3 Zinc ore 

<ll "' +> +> Year Q; "i:1 "i:1 (!; 

<:.> "i:1 

~ <.l l=l J:l~ Q) ~ l=l ......, Q) Q) 

::~l=l 'iii' ~ 'iii' ::~l=l 

~ <ll 8 ~ ~: l=l l=l ~: J:l Q) 

~ ... Q) s e 8 .e e ... Q) .e e .e a>p. '0 <:.> '0 ,;p. '0 <.l Q) ~ «l Q) J:l c:l Q; C<l Q; l=l 0 w ~ 0 t:S Q) 0 w 0 

H H 0 t:S 

1905___ ________ ______ ______ ____ __ ______ ______ liOO 5. 6 32.1 250 35.0 

19064 __ -- ------ ------ ------ ------ ------ ------ 440 ' 4.0 25.4 750 37.9 1907 ___ -------- ------ ------ ·----- ------ ------ ------ ------ ------ 200 38.0 1908 ___ -- ------ ------ ------ ------ ·------ ------ ------ ------ ------ 100 32.0 1911_ __ -------- __ c ___ ------ ------ ------ ------ 23 3.6 18. 8 567 36.7 

1912 ___ -------- ------ ------ ------ ------ ------ 118 2. 6 21.6 4, 375 36. 0 1913 ___ -------- ------ ------ ------ ------ ------ 576 4. 0 28.9 2, 413 34. 1 1914 ___ -------- ------ ------ ------ ------ ------ ------ ------ ------ 1, 617 35. 1 1915 ___ -------------- --·--- ------------------ 166 3. 1 32.2 1,147 33. 0 1916- ---------------- ---·-- 36 20.0 16.0 374 2.4 1.9.7 1,076 31.6 

1917 ___ -------- ------ ------ ------ --- -- ------ 746 3. 8 22.1 301 31.0 1918 ___ -------- ------ ------ 82 18. 0 11.0 339 2.3 18. 7 652 27. 4 

1919 ___ -------- ------ ------ --·---- ------ ------ 71 3. 0 24.2 475 27.1 4 1920 ___ ------·-- ------ ------ ------ ------ ------ 117 . 2. 6 21.0 72 30.2 1923_ __ 5512 2.9 36.8 ---- -- ------ ------ ------ ------ ------ 111 33. 1 1924___ 700 2. 9 19.3 ------ ------ ------ ------ ------ ------ -------- ------ 1925 ___ 1,039 3.0 19.2 ------------------ 6269 ------ 51.1 -------------- 1926 7__ 400 2.1 14.0 879 26.0 7.0 6 5. 5 38.5 -------------- 1927__ _ 73 2.4 18.1 ------------------------------------ 855 40. 0 1928 ___ -------- ------ ------ ------ ------ ------ ------ ------ ------ 25 30. 0 1929___ 537 2. 3 19.5 ------ ------ ------ ------ ------ ------ -------- ------ 1930___ 397 1.3 12.5 ------------ ---·--- -------------------------------- 1937 ___ -------- ------ ------ ------ ------ ---- -- 175 2. 2 19.3 -------- ------

3,658 ====997"' ====3,920 ~----· == 14 86,~ 

!No returns on 'file for 1909 and 1910. Mine idle 1921-22, 1931-36. 2 Lead sulphide ore contained from 0.001 to 0.01 ounce of gold to the ton and from 0.2 to 0.5 percent of copper. 3 Oxidized lead ore contained from 0.001 to 0.045 ounce of gold to the ton and from 0.02 to 0.8 percent of copper. · 4 20 tons of siliceous silver ore containing 37.7 ounces of silver to the ton also shipped in 1906. 

5 Mixture of crude ore and concentrates. & Evidently includes concentrates. 7 2 tons of dry silver ore credited with 14 ounces of recovered silver to the ton was also shipped in 1926. BAll zinc sulphide ore in 1927. 

According to the company's tax report the net earn- · 

ings during the 6 years 1915--20 averaged about $7,400 

annually and in 1919 and 1920 they averaged only 

$666.83 

sa Finlay, J. R., Report on appraisal of mines in New Mexico: New 

Mexico State Tax Commission, 1921-22, p. 53, 1922. 

The Juanita mine workings are in the southerly continuation of the Kelly ore zone, and are entirely in 

the Kelly limestone except for the adit tunnel, or level 

4, which extends east-northeast for 365 feet in the 

Sandia formation before cutting the top of the Kelly 

limestone. Levels 4, 5, and 6, and some tunnels at 

higher levels (pl. 36) we~e accessible in 1915 and 1916. 

The limestone is cut by a zone of lamprophyre dikes 

that trend about parallel to the strike of the limestone 

and-dip from 45° to 80° E~ The limestone is cut off 

on the east by the Kelly-Graphic fault zone, which 

here ineludes three members that dip vertically to 

steeply east and step the li1nestone downward to the 

west. A parallel fault zone is exposed 130 to 160 feet 

west of the Kelly-Graphic. zone and is essentially a 

steplike continuation of the Brown fault in the Kelly 

mine. These two zones are eonnected hy at least 

three minor eross faults or fissures. Two of these, 

north of the adit tunnel, are followed by inclined 

winzes. They strike west-southwest, the more northerly one with downthrow on the north, and the other 

with downthrow on the soutn. The third fault is 370 

feet south of the tunnel, and its downthrow is on the 

south. A bedding fault along the "silver pipe" hed is 

exposed on level 4 about 300 feet south of the adit 

tunnel. A larnprophyre dike is cut off by it on the 

roof of the drift, but the amount of displacement along 

it is not shown. 

The early workings, which evidently include the 

upper three levels, were opened by tunnels along the 

Kelly-Graphic fault zone. Only small parts of them 

were accessible to us. The northernmost, in the 

Juanita North Lode claim, extends from Kelly <;iulch 

along a spur of the main fault for about 50 feet, and 

a winze from it explores the same fault 35 feet lower. 

It opened ore that extended down to the fourth or main 

tunnel level. A seeond tunnel, not shown on plate 36, 

but 500 feet to the south, enters the fault zone near the 

· northern cross fault. It was not aecessible in 1916. 

The third and fourth tunnels, whose portals are in the 

small gulch 1,000 feet south of Kelly Gulch, explore a 

fault 100 feet or more west of the main fault. The 

northern of these two tunnels lies along and beneath 

old oxidized lead stapes near the junction of· the middle cross fault . with the Kelly-Graphic. zone. The 

faults exposed in these upper tunnels contain quartz 

and barite, from which sulphides have been partly 

leached, although in places they contained enough 

galena to be mined in small leasing operations in 1916. 

The uppermost beds, especially of the Kelly limestone, 

have been silicified along these. faults, as is well shown 

i11 the Juanita North Lode claim. The oxidized l~ad 

ore lies beneath this silicified cap but does not extend 

far from the north-trending faults, exoopt at their intersections with the two northern cross faults, where 

it extends the full width of the Kelly-Graphic zone 
MINES IN THE; MAIN ORE1 ZONE 139 

and continues westward down the dip of the limestone 

along the cross faults. Narrow bands of cellular zinc 

carbonate form the walls of the more upright stopes 

and the floors or down -dip extensions of the stopes 

along the bedding. 

The main adit tunnel, or level 4, reaches the bottoms 

of the old stopes in the upper Kelly limestone just 

south of the middle cross fault, and the floor of the 

stoped ground consists of a quartz-barite aggregate 

that rests on the ";:;ilver pipe" bed. The stopes extend 

for at least 170 feet south of the cross fault and have 

been reached by raises from level 4. East crosscuts 

in the lower Kelly beds have not disclosed any ore. 

1 About 350 feet south 6f the tunn'el a small upright 

shoot has been stoped along a fissure that strikes north 

and dips 57° E. 'fhis fissure crosses the bedding fault 

along the "silver pipe." An east crosscut a little 

farther south extends 90 feet, crossing a fault along a 

lampraphyre dike 50 feet east of the drift and continuing through iron -stained silicified limestone to a second 

member of the Kelly-Graphic fault zone, but no ore 

had been found in 1916. 

The southern cross fault is a little south of this 

crosscut. Level 4 turns ·eastward :for 80 feet, crossing 

this fault at a low angle and continuing southward 

for 270 feet. Near its south end a west crosscut has 

been driven completely through the Kelly limestone, 

which is there overlain by pebbly quartzite and shale. 

Nothing of promise was found in these workings. 

The southern cross .fault evidently marks the south 

end , of at least the western members of the KellyGraphic fault zone and has prevented ore-forming 

solutions from permeating the ground south of it. 

North of the adit tunnel level 4 reaches the top of 

the Kelly limestone at the middle cross fault and 

curves eastward, crosscutting to the "marbleized lime" 

bed above which the old stopes are reached by raises. 

It extends northward for 220-feet, crossing the bottom 

of a stope that extends downward along the northern 

cross fault, and continues 170 feet farther to a raise 

that connects with the workings in the Juanita North 

Lode claim south of the tunnel mentioned on page 138. 

Ore has been mined along inclines in the lower 

Kelly limestone that follow the northern and middle 

cross faults down to level 5. A little above level 5 

pyritic quartz is present along the northern cross fault, 

and a raise along it disclosed some high-grade sulphide 

ore just below the "silver pipe" bed and along the intersection with a minor fault of northwest trend and 

northeast dip. The middle cross fault similarly contains quartz and galena just below the "silver pipe" 

and has been stoped to a slight extent above the 

"silver pipe." The· incline along it crosses two closely 

parallel faults of north-northwest trend along which 

shale has been stepped down_ against the upper l(elly 

limestone. This fault zone, which is in steplike relation to the fault cut at the south end of level 6 in the 

Kelly mine, is followed northward on level 5, and a few 

horizontal tubelike shoots have been mined along it. 

The shoots are floored by silicified limestone that rests 

on the "silver pipe" bed. The "silver pipe" bed is 

offset by two minor faults of north-northwest to northwest trend that join or cross the fault along the drift. 

The drift continues nearly to the north boundary line, 

where it turns eastward and completely crosscuts the 

lower Kelly limestone. 

The confinement of relatively large ore shoots to that 

part of the Kelly-Graphic fault zone that is near the 

cross faults and the relative prominence of quartz and 

barite gangue indicate that the ore-forming solutions 

were farther from their source and had somewhat less 

penetrating power than in the Kelly and GraphicWaldo mines. Solutions that escaped from the KellyGraphic zone along the two northern cross faults and 

the adjacent parts of the west fault zone had practically no penetrating power and therefore formed 

veinlike shoots. The southern part of level 7 in the 

Kelly mine lies parallel to level 5 of the Juanita mine 

and . 250 feet west of it; inclined raises from it extend 

eastward nearly to the property line. without disclosing 

encouraging signs of ore. Downward exploration near 

the middle cross fault west of level 5 also failed to disclose any ore. The small shoots along level 5, 

therefore, . appear to mark the west· limit of ore 

deposition. 

SOUTH JUANITA (JUANITA EXTENSION) MINE 

The South Juanita mine, entirely within the Juanita 

Extension claim, is about a quarter of a. mile south of. 

the Juanita mine. Its small, intermittent output from 

1907 to 1939, recorded . in the accompanying table, has 

consisted entirely of oxidized zinc and oxidized lead 

ore, both of which have been of lower grade than those 

of the three larger mines to the north. 

Ore shipped from So,uth Juanita mine, 1907-.39/ and gross metal 

content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of 

Mines, U. S. Department of the Interior, Denver, Colo.] 

Ore 

Year 

· Class 

{

Lead, oxidized ___ _ 1907 Zinc, ox!dized and sulphide ______ _ _ 

1912 Zinc, oxidized __ __ _ 1918 ..... do. ~------ --- 1919 ___ __ do ___________ _ 

1927 Lead, oxidized(?)2_ 1928 ____ _ do 2 __________ _ 

1929 ____ _ do __ ________ _ _ 

Silver Copper Lead 

(ounces) (pounds) (pounds) 

o:> 

b.O~ o:> o:> 

c:JO b.O b.O 

~ 3 ........ ~ 3 ctl 

o:>r-. .s ai 0 0 p.o:> 0 p. 0 p. 

E-< E-< ~0. E-< ~ E-< ~ 

Zinc 

(pounds) 

o:> 

b.O 

3 ~ 0 p. 

E-< ~ 

100 ----- ---- - ------ ----- 52,000 26.0 -------- -----

50 --- -- ----- ------ ----- --- ----- ------ 25,000 25.0 25 ----- ----- ------ ----- -------------- 16,667 33.3 64 ----- --- -- ------ ----- -- ------ ------ 36,370 28.4 88 ----- ----- ------ ----- -------- ------ 52,800 .30. 0 104 184 1.8 837 0.4 29,617 14.2 ------------- 226 554 2. 5 2, 556 0 6 89,853 19.9 -------- ----- 82 97 1. 2 349 . 2 20,599 12.9 -------- -----

739 835 ----- 3, 742 ----- 192,069 ------ 130,837 -----

I Mine idle 1908-11, 1913-17, and 1930-39; no shipments recorded 1920-26. Two 

carloads oflead ore were reported shipped in 1925, but metal content was not stated. 

2 Ore also contained 0.90 ounce of gold in 1927 and 1.70 ounces in 1928. No gold was reported in other years. 
140 MAGDALENA MINING DISrrRICT, NEW MEXICO 

w. E. 

Shale 

I I 

5o Feet 

~ : 

~-J 

\ 

FIGURE 17.- Cross section (A- Bon plate 37) of South Juanita (Juanita Extension) 

mine. After W. H. Paul. with minor additions. 

The mine (pl. 37 and fig. 17) is opened by a 200-foot 

vertical shaft along the Kelly-Graphic fault and by a 

120-foot adit tunnel that trends east-southeast and 

reaches the Kelly-Graphic fault 35 feet north of the 

shaft at a depth of 70 feet. Three levels have been 

driven-the adit level, the first level 35 feet lower, and 

the second level 50 feet below the first level. A third 

level and a long, lower adit tunnel whose portal would 

be 380 feet west-southwest of the present adit have been 

planned, according to mine maps, but so far as known 

no work has been done on them. The mine's geologic 

conditions are similar to those in the eastern part of the 

Juanita mine. The l(elly-Graphic fault with nearly 

vertical dip forms the east limit of the workings. It 

undulates in strike and in the southern part of the mine 

it curves from S. 15° E. to S. 45° E. a-s it approaches 

the Germany fault. The Kelly limestone with westerly 

dip pitches slightly northward along the workings except to the north of the adit level, where it becomes 

nearly horizontal. It is bounded by pre-Cambrian 

"greenstone" (gabbro or argillite) along this fault and 

is cut by two minor longitudinal faults conveniently 

called the middle and west faults. The middle fault, 

15 feet west of the Kelly-Graphic fault, drops the limestone a few feet on the west ; and the west fault, 45 

feet farther west, drops it 60 feet or more also on the 

west. The only cross fissure noted is along the adit 

tunnel where the north pitch of the limestone is a little 

' steeper than elsewhere. A few closely spaced lamprophyre dikes parallel to the minor faults are exposed 

in the southern part of the mine; and one dike of 

latite porphyry, 21;2 feet thick and similar to the latite 

porphyry in the large faulted sill south of Chihuahua 

Gulch, is exposed at the south end of level 2.. This dike 

dips steeply east and is beveled off by a more steeply 

east-dipping fault that strikes N. 35° "\V. and evidently · 

corresponds to the middle fault. 

The ore bodies include a small stope on the adit level, 

one along level 1, and a few small pockets on level 

2. The adit-level stope _is along the bedding of the 

upper Kelly limestone and is capped by replacement 

quartz that underlies the upper "silver pipe" bed. The 

stope and the quartz cap are bounded on the west by 

the middle fault. The principal stope of the mine 

pitches northward at a small angle and crosses level 1 

near the shaft. It extends 100 feet north and 270 feet 

or more south of the shaft. It underlies the 1nain 

"silver pipe" bed, and for most of its length south 

of the shaft it is bounded on the west by a lamprophyre 

dike. It narrows toward its south end, where the 

strike of the country rock is north west. There the 

Kelly-Graphic fault is tight but the "greenstone" and 

limestone along it are bleached and impregnated with 

pyrite and quartz. The ore mined has been largely 

lead carbonate, with minor quantities of zinc carbonate 

along the dow:n-dip side of the lead shoots and along 

fractures below and also west of the lead shoots. On 

level 2 a few small bunches of ore have been stoped in 
MINES IN ·THE MAIN ORE ZONE 141 

lower l{elly limestone about . 50 feet northwest of the 

shaft, and at the north end of the level ore containing 

pyrite, zinc blende, galena, and chalcopyrite in a quartz 

gangue has been followed by a winze for about 40 feet 

on the east side of the west fault. At the bottom of 

the winze "greenstone" appears on the east side of the . 

fault, but the ore continues downward. 

BLACK CLOUD AND MISTLETOE MINES 

The consolidated property of the Black Cloud Mining & Milling Corporation includes part of the main 

ore zone and extends eastward bey~nd the South 

Stonewall fault. It includes the Helen Cross group, 

from which small shipments of ore were reported in 

1906-7 and 1917-18. The original Black Cloud and 

Mistletoe mines are near the South Stonewall fault 

between the heads of Chihuahua and Mist~etoe Gulches. 

The Mistletoe or Gordon tunnel is down the slope 

to the west at an altitude of about 7,950 feet. The 

Mistletoe mine and the newly driven tunnel were both 

owned by the Mistletoe & Magdalena Tunnel Co. in 

1908. The Black Cloud mine was opened about 1915. 

In 1926. it was acquired by the newly organized Black 

Cloud Mining & Milling Corporation under a longterm lease with option to purchase for $24,500. The 

same company acquired a lease on the Mistletoe mine 

and tunnel in 1927 or 1928 with an option to purchase 

them for $125,000.84. The property then comprised 

about 400 acres. The Mistletoe mine was connected 

by an aerial tramway with the mill at the mouth of 

the tunnel. This mill, erected by the old company in 

1908 (p. 79) was overhauled by the new company 

and operated during 1928 and 1929. According to the 

~fines Handbook,85 the value of the total output of 

the property by former operators was about $100,000 

and by the new operators $37,500, whereas $150,000 had 

been spent on devel<Jpment work. Reorganization to 

provide funds for additional development work and 

equipment was then being contemplated. 

The oxidized ore shipped, according to the Mines 

Handbook; averaged between 7 and 10 percent of lead, 

and the average value of the silver and gold content. 

of the ore was les~ than $2.00 to the ton. Some ore of 

shipping grade contained as much as 25 percent of 

84 l\:fines Handbook, vol. 18, pt. 1, p. 1661, 1931. 96 Idem, p. 1661. 

/ ' . 

lead. The sulphide ore, presumably from the winze 

along the Mistletoe fault :in the tunnel, was reported to 

average between 12 and 15 percent of lead and 20 

percent of zinc and to contain minor amounts of 

copper, silver, and gold. 

The recorded outputs of ore from the ·Helen Cross 

group, the Mistletoe tunnel, and the Black Cloud 

workings are sliown in the accompanying tables. The 

copper and some of the lead ores from the tunnel were 

higher in silver than inost of the ores shipped from 

the district since 1904. The lead sulphide ores from 

the Black Cloud workings weue mostly of rather low 

grade and characteristic of the siliceo~s replacement 

ores east of the main ore zone, ~ut the oxidized zinc 

ores formed through the replacement of unsi1icified ' 

limestone beneath the lead deposits were of as high 

grade as those of the more productive mines in the 

main zone. 

Ore shipped from Helen Cross group, 1906-181., and its .gross 

' metal content 

[Data collected by C. W. Henderson, Geological Survey and Bureau of 

Miiies, U. S. Department of the Interior, Denver, Colo.] 

Gold Silver Copper Lead Zinc 

(ounces) (ounces) (pounds) (pounds) (pounds) Year Tons 

----------------------------

1906.-----------------

1907- ---------- ------- { 

1917------------------ 1918_--- --------------

61 . ---------- ------ -- ---------- ---------- 30,000 8 0. 63 103 ---------- 4, 620 ---------- 21 ---------- ---------- ---------- ---------- 13,428 24 ------ -- -- ---------- ---------- ---------- 17,520 38 1.90 184 844 16,260 ----------

I No ore shipped during years for which no reGard is shown. 

Ore shipped from Mistletoe tunnel, 1910-'26/- and its gros-s metal 

content 

[Data collected and classified by C. W. Henderson, Geological Survey and 

Bureau of Mines, U. S. pepartment of the Interior, Denver, Colo.] 

Ore 

Gold Silver Copper Lead Zinc 

Year----------.......-- (ounces) (ounces) (pounds) (pounds) (pounds) 

Class Tons 

1910 ZiJ;J.C and lead, oxi- ·dized ______________ 2 500 3. 70 955 401 84,091 11,871 1911 _____ do ________________ 3 30 --------- --------- --------- --------- --------- 1916 Lead ___ __ _______ _____ 141 24.00 1, 249 2,150 152,718 -------- ~ 

1917 Copper. _____________ • 20 162 2, 281 --------- --------- 1918 _____ dQ _______________ 28 204 2, 891 --------- --------- 1924 Lead (ore and con- centrates) __________ 140 7. 83 1, 288 1, 990 57,731 --------- 1925 Lead _________________ 316 2. 70 647 2,060 69,603 --------- 1926 _____ do _________________ 254 10.20 517 1, 529 51,019 ---------

I, 429 48. 43 5, 022 13, 302 415, 162 11, 871 

1 No ore shipped during years for which no record is shown. 2 500 tons of crude ore yielded 91 tons of lead concentrates and 16 tons of zinc con- centrates. Ore treated in mill, but p.o shipment made. 

·, 
142 MAGDALENA MINIKG DISil.'RICT, NEW MEXICO 

Ore mined at Black Cloud mine, 1915-38,1 and its gross metal content 

[Data collected and classified by C. W . Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Ore Gold (ounces) Silver (ounces) · Copper Lead Zinc 

Year -·--------------------.----1---;------------------·---;---1---·--.,---·-

Class Tons Total Per ton Total Per ton Pounds Percent Pounds Percent Pounds Percent 

1915 

1916 

Zinc, oxidized 2~-- ~-- ------------- ---------- 2434 

191 . ---- ----- ---------- ---------- ---------- ---------- ---------- ------------ ---------- 282, 689 32. 6 - _do ________ ____ ___ ------- _____ __ ______ _____ _ ---------- -------- -- -- -------- ---------- ---------- --------~- ------------ ------- -- - 128,784 33.7 

19"!7 {

Lead, oxidized (?) ________ ____ _____ ______ __ _ 3 4, 500 

15 

13 

91 

49 

27.23 0. 006 1, 713 0. 4 6, 494 0. 06 176,944 1. 7 ---------- ----------

___ ------- -------- -- ---------- ---------- ---------- ---------- ------------ ---------- 10,320 34. 4 

. 1923 

1925 

1927 

1928 

1933 

1937 

1938 

Zinc, oxidized ________________ ___ ____ ___ ___ _ 

{t~fJ~~~f~~~ _____ do __ ______________ -~~~= = == _____ === == ____ === = 

_= ___== = _____ = = ~= == ___ = = _ 

{~~:~ ~~~~~~~ ~~~~= === ============ =======~ 

t ==== ~g== =========== == ==== = = === === === = = = == = = 

.; 1, 000 

26 6 2,000 7 

10 

15 

103 9 

---------- ---------- 3.00 

1. 40 .03 

29.00 .03 

.49 .02 

81.98 .04 

---------- ---· ------- .20 . 02 

.50 ---------- 60.50 ---------- .20 ----------

152 11.7 1, 090 

338 3. 7 1, 908 

183 3. 8 706 

2, 503 2. 5 3,904 

118 4. 5 249 4, 505 2. 3 6, 850 

56 8.0 110 

72 7. 2 243 66 261 111 112 37 64 

44.0 

4.8 

4.5 

.2 

. 5 

.2 

.7 

1.2 

671 

31,666 

18,841 

248,966 7,399 

572,802 

6, 591 

6,447 

7, 910 

413 

3, 902 

41.3 

4 15.3 

4 16.8 

12.4 

14.3 

14.3 

47.1 

32.2 

34, 746 ---------- 280 2. 0 

8,463 204.50 ---------- 9,854 ---------- 21,991 ---------- 1,082,552 ---c------ 456, 819 ---- ---- --

1 Mine idle 1934--36. No production in 1918-22, 1924, 1926, and 1929-32, although assessment work and some experimenting in the mill were carried on. 2 Gold, silver, and copper were present in siliceous gangue but were not paid for. 3 Produced 247 tons of concentrates. 

The workii)gs near the South Stonewall fault are 

open~d by several short tunnels. The two northernmost, not shown on the geologic map, are in Kelly 

}jmestone about 1,000 feet north of the aerial tramway 

and between the Stonewall fault and the minor fault 

200 feet to the east. The upper Kelly limestone in 

their vicinity is almost completely silicified, and its 

outcrop between the two tunnels is marked by a small 

stope mainly just above the "silver pipe" bed. The 

upper tunnel extends southward along the east fault, 

which dips 76° W. About 70 feet from its portal 

there is an old, filled winze that is said to extend 

75 feet down the dip and to have exposed some good 

ore. The lower tunnel trends S. 20° E. along an 

east-dipping fissure at its intersection with the "silver 

pipe". bed. A short raise 45 feet from its portal connects with a small stope just above the "silver pipe" 

bed. The ore shoot stoped is about a foot thick, parn.llels the bedding, and consists of streaks of galena in a 

gangue of replacement quartz. The stope extends to 

the upper tunnel at a point midway between the portal 

and the old winze. A little azurite or blue copper carbonate was found at a few places just above and below 

the stope. The lower· tunnel continues 50 feet beyond 

its connection with the stope and exposes streaks of 

galena just above the "silver pipe" bed. It also exposes zinc carbonate which has replaced the "silver 

pipe'' bed for as much as a foot below its top. The 

zinc carbonate is underlain by soft, leached, ironstained limestone. 

The principal Black Cloud workings are east of 

the east fault and about 800 feet south of the two 

tunnels just described. They include two levels opened 

by upper and lower tunnels and connected with an 

abandoned shaft, which is marked on plate 2 by the 

upper of two buildings. The principal work in 1916 

was on level 2 under the direction of Paul B. Moore, 

• Percentage of recovered metal. ~ Produced 270 tons of concentrates. 6 Produced 591 tons of concentrates. 

of Magdalena. The north drift on that level lies in 

or just below the quartz that here also has almost 

completely replaced the upper Kelly limestone. · The 

quartz had been mined in places for lead, and small 

bodies of zinc carbonate that had replaced remnants 

of limestone between the quartz and the "silver pipe" 

bed were being stoped in 1916. The ore was accompanied by streaks of soft black earthly material, and 

some rusty material, that lay just above the stope and 

along the sides of it and contained little or no zinc. 

About 300 feet north of the shaft, and beyond the 

second crosscut, the north drift continues for a short 

distance along a fault that trends N. 25° W., dips 80° 

W., and has a downthrow of 6 to 8 feet on the west. 

It is apparently a branch of the east fault. A raise 

near the fault connects with a relatively large lead 

stope. This stope is also closely related to a fissure 

that in part nearly coincides with the bedding but 

steepens southward to a dip of 50°. The lead ore 

consists of partly oxidized galena in a gangue of 

replacement quartz. The galena is in part coarsegrained and is accompanied here and there by bunches 

of chalcopyrite. Such bunches are evidently the source 

of the small copper stains that are found throughout 

the siliceous ores in the southeast part of the district. 

The average content of the crude lead ore mined in 

1916 was said by :Mr. Moore to be 15 percent of lead 

and 2.25 ounces of silver and 0.05 ounce of gold to 

the ton. The concentrates, which in that year were 

produced in a mill at Magdalena, averaged 58 percent 

of lead and 9 ounces of silver and 1.8 ounces of gold 

to the to'n. The tailings contained about 0.9 percent 

of lead and less than 1 percent of copper. 

Zinc carbonate has been mined along the lower parts 

of the stope, and at several places beneath the stope 

small masses of brown "tallow clay" have replaced 

limestone immediately below the quartz mass. One of 
MINE'S IN THE MAIN ORE' ZON.l!l 143 

them also extends down ward for . about 10 feet into 

black earthy material along a steeply east-dipping 

fracture just east of the fault. The clay, which has 

fine horizontal banding even in the fissure, has slightly 

replaced the fissure walls. Although similar clays at 

Leadville, Colo.,86 contain considerable zinc, a test on 

the clay from the Black Cloud mine showed , little or 

no zinc. The clay, however, was regarded as a guide 

to zinc carbonate ore; in fact, veinlets and cavity linings of high-grade green botryoidal. smithsonite and 

white hydrozincite cut the clay, and similar material 

coats the larger masses of zinc carbonate ore. 

Another fairly large stope containing similar ore 

lies just above the tunnel level and extends south~ard 

from the shaft. An associated stope of zinc· carbonate 

ore, below tunnel level, replaces part of the "silver 

pipe" and the limestone just above it. This stope in 

1916 extended nearly 100 feet in a southerly direction 

and had a maximum width of 40 feet. Its height was 

very irregular and its cross section roughly U-shaped, 

as if it had replaced the upper limestone for short disstances along parallel steeply dipping fissures leaving 

an intervening hanging mass of limestone, but com- . 

pletely replacing the underlying "silver pipe" and 

adjacent beds. 

The lower tunnel near its north end penetrated about 

25 feet of pyritic quartz that contained specks of native 

silver, but the relations of this material to the lead ore 

and to faults and fissures were not clearly defined. 

The old Mistletoe mine was opened by two tunnels 

about 500 feet south of the main Black Cloud workings 

and a little east of the south end of the Stonewall fault. 

The principal work was done about 1911. The upper 

or main tunnel extends eastward about 50 feet to a 

narrow stope whose ore had replaced a limestone bed 

along a steeply east-dipping fissure. The stope extended for 90 feet north and 50 feet south of the tunnel. 

Low -grade ore left along the edges of the stope consists 

of galena in a gangue of leached quartz. The ore mined 

is said to have been of similar low grade and to nave . 

been milled. No associated zinc ore has been found. 

The lower of the tyYo tunnels cut a thin shoot of 

siliceous galena ore about 40 feet· from the portal. The 

shoot, which did not exceed a foot in thickness, underlay a shale parting about 6 feet below the upper "silver 

pipe" bed. A little ore had been stoped from it. 

The Mistletoe or Gordon tunnel, whose portal is on 

the north slope of Mistletoe Gulch at an approximate 

altitude of 7,950 feet, is 1,050 feet long. It extends in 

a general easterly direction but is slightly convex to 

the north. It was flooded in 1915 and 1916 but was 

mapped by Kosch1nann and Lasky in December 1929. 

It follows the gei1eral co_urse of a much faulted lam-pro86 Loughlin, G. F., The oxidized zinc ores of the Leadville district, 

Colorado : U. S. Geol. Survey Bull. 681, pp. 24-28, 1922. Emmons, S. F., 

Irving, J. D., and Loughlin, G. F., op. cit. (Prof. Paper 148), pp. 

160-162. 

phyre dike or sill for about 100 feet and continues in 

· Madera limestone as far as the Mistletoe fault, east 

of which it cuts black shale and limestone as far as a 

second fault 19o- feet east of the Mistletoe ·fault; and 

there it enters into the argillite for a few feet. The 

Mistletoe fault is represented by a crushed zone 10 

feet thick, about 820 feet due east of the portal, and 

almost vertically.below its position on the surface. Its 

dip in the tunnel, however, is 75° W. The principal 

minor faults cut by the tunnel farther west conform in 

positi~n to those mapped at the surface, and the same 

is true of the fault 190 feet east of the Mistletoe fault. 

Several other minor faults of vertical to steep westerly 

dip are cut. The shale and limestone east of the Mistletoe fault, however, have not been satisfactorily explained. According to the geologic map (pl. 2), 

displacement along the fault east of the Mistletoe is 

not very great, 'but the rocks in the tunnel, which are 

evidently parts of the shale and lower limestone members of the Sandia formation, imply a drop of at least 

250 feet, sufficient to place the lower quartzite member 

and the Kelly limestone below the tunnel level. A re-· 

check of the surface mapping by Koschmann and Lasky 

failed .to account for the discrepancy, and it can only 

be inferred either that the principal displacement 

shifts from the Mistletoe to the eastern fault between 

the surface and the tunnel level or that the structure 

between the two faults is complicated by concealed 

minor faults and perhaps. contorted bedding. 

A little coarse-grained siliceous lead-zinc sulphide ore 

was noted on the tunnel dump in 1916. This ore evidently came from a winze along the Mistletoe fault, in 

which ore was reported at a depth of 50 feet below the 

tunnel level. The winze was full of water in 1929. 

This ore suggests that the Kelly limestone on the west 

side of the fault may be worthy of exploration.. Drilling would doubtless be necessary to determine the 

position of the limestone. · The comparative costs of 

pumping and driving of a lower drainage tunnel should 

also be considered. . 

YOUNG .AMERICA, IMPERIAL, AND ENTERPRISE CLAIMS 

The Young America mine is situated on the upper 

slope of the Magdalena Range, just east of the Water 

Canyon Trail and ll/5 miles southeast of Kelly. Its 

first owner since 1907, when annual reports of it began 

to be submitted to the United States Geologica] Survey, 

was H. W. Russell & Co., who reported a shipment in 

1909 of 22 tons of crude ore, from which 220 ounces of 

silver and 22,520 pounds of lead were recovered. The 

ownership passed to C. T. Brown in 1911 and to the 

Empire Zinc Co. in 1915. It was leased to Sim Exter 

in 1916, but his shipments were evidently included with 

those of the Empire Zinc Co. for that year. 

The workings are mainly in the Young America and 

Imperial claims and the unpatented Enterprise claim, 

which overlaps the eastern parts of the other two (see 
144 MAGDALENA MINING DISTRICT, NEW MEXICO 

fig. 18). The workings include several short tunnels 

of easterly trend from which drifts extend northward 

and southward. Only two-here called the Young 

America and Enterprise tunnels-were accessible in 

1916. The Young America tunnel is close to the north 

boundary of the Young America claim. . Drifts from 

it follow the Young America fault, which separates the 

shale member of the Sandia formation on the west 

from silicified upper Kelly limestone on the east. The 

silicified part of the limestone is about 40 feet thick 

and should therefore include practically the entire 

upper member. 

To the northeast, in the Imperial claim, the north drift 

from the tunnel whose altitude is 8,570 feet is said to 

have followed a streak of lead and copper carbonates. 

The south drift from this tunnel opened two small 

bodies of high-grade zinc carbonate that had evidently 

replaced unsilicified remnants of limestone. The Ellen 

tunnel, south of the Young America, was said to trend 

about N. 73° E. and to connect with an old shaft that 

had been sunk along the fault and had disclosed a little 

high -grade copper ore. 

The Enterprise tunnel extends east-northeast to the 

most westerly of two closely parallel minor faults of 

north-northwest trend. At the breast of the tunnel a 

raise along the bedding has followed a thin streak of 

lead carbonate across the two faults. and for a short 

distance beyond without disclosing an ore shoot. A 

thin streak of zinc carbonate lies about 5 feet below 

the lead carbonate streak. The south drift from the 

tunnel follows the lead carbonate streak along the west 

side of the west fault, which is vertical at the tunnel 

but dips 70° W. along the southern part of the drift. 

Lead carbonate was mined for a width of 2 feet along 

. the fault and connected with a small stope 3 feet thick 

0 100 200 300 4oo Feet 

N 

that extended westward or down-dip from the fault. 

The stope along the bedding was roofed and floored 

by silicified limestone. That in the floor was cellular 

and about 2 feet thick and connected downward with 

a vertical mass that had replaced limestone along a 

vertical fissure. Two elliptical bodies of zinc carbonate were mined, one along each side of the vertical 

quartz body. They were 12 to 15 feet long, as much 

as. 5 feet wide, and about 4 feet thick. 

The north drift from the tunnel turned east-northeast along a cross fissure close to the southeast boundary of the Imperial claim. The limestone on both 

sides of the cross fissure was replaced by a mass of 

coarse-grained high-grade galena, which was said to 

have an unusually high content of silver. The ore was 

accompanied by some quartz but ended abruptly 

against unaltered lin1estone. The cross fissure had 

been followed for about 20 feet in this ore in 1916; and 

at the breast of the drift, which was near a fault of 

northerly trend, it was turning to a more northerly 

course. This structural condition suggested that the 

ore shoot was controlled by the intersection of fissures. 

LINCHBURG TUNNEL 

The Linch burg tunnel (fig. 18) is about a mi!e 

southeast of Kelly. It was begun by the American 

Zinc, Lead & Smelting Co. in 1910, was taken over 

by C. T. Brown in 1912, and by the Empire Zinc Co. 

in 1915 or 1916. ' 

It extends about 1,150 feet in an average N. 75° E. 

direction to prospect the Kelly limestone on the west 

or downthrown side of · the Young America fault. 

Its breast is along the middle of the northwest boundary of the Young America claim. A raise (fig. 19) 

had been put up into the limestone in 1916, but it was 

Imperial, and Enterprise claims.· 
GEOLOGICAL SURVEY 

7778.8' 

"Greenstone'' 

£1.7778.8' LEVEL I 

2 7728' 

LEVEL 3 

7678' 

LQNGJTUDINAL PROFILE 

PLAN 

,...., 

I I 

5~o~--~~~--o~----------~5~o------------~----------~~--------~2~ooFeet 

PROFESSIONAL PAPER 200 PLATE 37 

After W. H.Paur 

PLAN AND LONGITUDINAL PROFILE OF SOUTH JUANITA (JUANITA EXTENSION) MINE. 

200889--42 (Face p. 144) 
, '1 .... 

-·· 
MINES IN TliE· MAIN ORE ZONE 145 

EXPLANATION 

"Greenstone" 

25 

~\;::_;; 

Granit e 

0 

Zi nc o re · Copper ore 

50 Feet 

F IGU RE 19.-Section through main raise n ea r breast of Li nchburg tunnel, looking N. 70° E. After Soren Ringlund. 

so full of gas when visited that observations were confined to the tunnel. The portal, at an approximate 

altitude of 8,050 feet according to plate 2, is in purple 

andesite, which continues for a short distance. The 

tunnel then cuts a dike of latite porphyry with north 

strike and vertical dip. The dike is about 25 feet 

thick and is faulted against Madera limestone on tht3 

east. The Madera limestone continues to a point 

about 570 feet from the portal, where it is faulted 

against th~ lower beds of the Sandia formation. A 

short distance farther east the tunnel cuts 'the Kelly 

limestone, which dips west at a small angle and continues to a point about 100 feet from. the end of the 

tunnel, where it is underlain by pre-Cambrian argillite 

or "greenstone." A short · distanc~ beyond the base 

of the Kelly limestone the Y omtg America fault is 

exposed, and a little farther east the argillite is cut 

by. granite, whose contact dips about 40° W. The 

lower beds of the Kelly limestone,· called the "Pinto 

limestone," are mineralized along the tunnel;· and the 

main raise, put up along a west branch of the Young 

America fault (fig. 19) is said to have cut ore of low 

to moderate grade both below and above the "silver 

pipe" bed. The argillite or greenstone is also 

mineralized along the fault zone. Since 1916 drifts 

were extended to the north and the south on the tunnel 

level and considerable work was done ·through the 

raise; but the prevailing market for zinc has been such 

that no shipments of ore have been made, and the 

workings have probably been idle from .1921 to 1941. 

A specimen of the mineralized limestone collected 

on the tunnel level in 1916 contained about 50 percent 

of garnet, 3"0 percent of hedenbergite, 10 percent of 

quartz, 5 percent of calcite, and 5 percent of sulphides 

(galena, zinc blende, and chalcopyrite). The limestone 

also contains specularite in places. Specimens of the 

underlying argillite or "greenstone" were also found 

to contain the same . sulphides and specularite, as well 

as epidote and colorless garnet. This association 

points to a more intense mineralization than has been 

indicated elsewhere in the southern part of the district. 

Its relation to the ore and gangue in the higher Young 

America and Enterprise workings implies that the oreforming solutions, locally at least, rose vertically. It 

also suggests that the Kelly limestone for a considerable distance along the west side of the fault may be 

more thoroughly replaced by ore than it is on the 

east side. The Kelly limestone west of the main fault 

zone has not been exposed at any other place south of 

the South Juanita mine, but it may be significant that 

the showing along the fault in the Mistletoe tunnel 

1,800 feet to the north justified the sinking of a winze; 

in fact, the Kelly limestone throughout this distance 

is worthy of consideration. 

WOODLAND MINE 

The vVoodland mine is near the summit of the range, 

due east of South Camp, with which it was once connected by an aerial tramway. It is opened by a short 

tunnel in silicified upper Kelly limestone. A short 

distance from the portal and a little above the "silver 

pipe" bed the tunnel cuts a streak of partly leached 

galena and quartz. The streak lies along the bedding 

and has been followed for short distances by north and 

south drifts and by a raise to the east. :No evidence 

of stoping was found in these workings. 

CAVERN Al\'D GRAND LEDGE MINES 

The Cavern and Grand Ledge claims are opened by 

two tunnels along the Water Canyon ~ Trail ea~t of 
146 MAGDALENA MININO DISTRICT, NEW MEXICO 

South Camp and just southwest of the Woodland mine. 

The tunnels are connected by an inclined tram road 

with a small dismantled mill (p. 79) in the middle 

branch of Patterson Canyon. The claims were locat€d 

in 1885 and were worked intermittently. The last mining done was in 1897 on the Grand Ledge and about 

1904 on the Cavern claim, although assessment work 

was continued until 1919. The property in 1915 and 

1916 was in the care of Mr. F. A. Gordon, who guided 

Mr. Loughlin through the accessible workings of these 

and other properties in the southern part of the district. We are also indebted to Messrs. G. L. Brooks 

and B. A. Statz, of Albuquerque, president and 

engineer of the Cavern Gold Mining Co., for maps of 

the workings. 

The claims are ~tlong a southerly continuation of the 

fault zone that extends through the Young America 

claim. The courses of the principal faults in the zone 

are irregular and partly concealed by an old landslide. 

The Young America fault evidently curves southeastward, is joined by a minor fault of southerly trend, and 

thence turns to the south and south-southwest. The 

fault west of the Young America curves even more· 

southeastward. The two faults unite beneath the landslide and continue southward as the Grand Ledge fault, 

whose west wall at the surface consists of Madera and 

uppermost Sandia beds, and whose east wall is preCambrian argillite or "greenstone". The argillite is 

partly capped by silicified Kelly limestone, none of 

which extends down to the tunnel levels. The Grand 

Ledge fault is followed by a dike of white rhyolite in 

th~ Grand Ledge tunnel. · 

The Grand Ledge tunnel (fig. 20), which evidently 

corresponds to the first level of the workings, has an 

altitude of 8,761 feet and extends S. 83 ° E. for about 

175 feet. The first 90 feet is in Madera and Sandia 

beds which dip 20°-25° W. and are bounded on the 

east by the white rhyolite dike and the main fault. 

The remainder of the. workings are in argillite. The 

rhyolite dike is followed by a vein composed of barite 

with a little quartz, fluorspar, and sulphides, which has 

been opened by a short north drift. Eighteen feet east 

of the vein, a south drift in argillite has explored a 

veinlet of barite and quartz with a little zinc carbonate 

and green copper carbonate. This veinlet strikes 

N. 20° W., dips 65° W., and evidently follows a small 

spur from the main fault. Twenty-one feet east of the 

south drift the main north drift follows a fault vein 

for about 50 feet in argillite and connects with an old 

stope that strikes N. 25° E. arid dips steeply east at the 

tunnel level but curves to 60° W. above the level. 

According to a generalized blue print dated 1904, on 

which figure 20 is partly based, this stope has a horizontal length above the level of 100 feet and extends 

nearly to the surface. The average width of the stope 

where seen on the tunnel level is about 4 feet, though 

its horizontal projection in figure 20 is greater, and its 

maximum width is 15 feet. Remnants of the ore consisted of galena and cerussite in a honeycombed ironstained gangue. The ore shipped is said to have included "sand carbonate" and some low -grade copper 

carbonate. The north drift, according to the blue 

print, continues for about 200 feet, passing an 

abandoned shaft 25 feet north of the stope. 

The Cavern tunnel is about 200 feet N. 10° W. 

from the Grand Ledge tunnel and 30 feet or more 

lower. It trends N. 73°-87° E. for 290 feet, passing 

through Madera and upper Sandia beds and ending in 

the main fault zone. The beds dip about 35° "\V. 

except in the eastern 60 feet of the tunnel, where black 

py~itic shale of the Sandia formation dips 65° W. 

and is cut by many nearly vertical fractures that are 

essentially part of the fault zone. · A south branch of 

the tunnel obliquely crosscuts the shale for about 60 

feet and connects with the abandoned shaft, south of 

which an old stope extends upward and, according to 

the blue print, is essentially continuous with the stope 

on the Grand Ledge level. It is also apparently continuous with a downward tapering stope that was 

opened by short crosscuts from the old shaft 25 and 

50 feet below the Cavern tunnel or second level. A 

winze inclined about 78° W. followed the mineralized 

zone downward for 90 feet from the bottom level, but 

no drifting or stoping was done from it. 

The appreciable size of the ore shoot and its mineral 

composition imply that ore depositioJ?. in this part of 

the main fault zone was rather intense, especially as 

the ore was deposited between walls of argillite and 

dense black limestone · or shale, which are relatively 

resistant to replacement. The fact that the downthrow on the west side of the fault is greater than at 

any other place along the fault zone also favors the 

existence of minor faults and fractures in the Kelly 

limestone and other more brittle beds below the shale 

member of the Sandia formation, which. could have 

served as circulation channels for ore-forming solutions just as those in the Graphic-Waldo and Kelly 

mines did. The presence of high-temperature minerals as well as promising shoots of sulphide ore in 

Kelly limestone along the same fault zone in the 

Linchburg tunnel, less than 2,000 feet to the north, 

is a strong indication of a local source of ore in the 

vic:lnity. Geologic conditions as a whole, therefore, 

favor the exploration of the Kelly limestone on the 

west side of the Grand Ledge fault. The irregularity 

of dip at and near the surface prevent a close estimate 

of the depth of the Kelly limestone, which should be 

determined by drilling. Calculation from available 

data places the ~ase of the Kelly limestone at an average altitude of 7,600 feet and implies that the 

limeston~ could be drained by a tunnel 3,200 feet long 

with its portal in the north branch of Patterson Can-
MINES IN THE MAIN ORE' ZONE 

N 

'1 

0 

w. 

Alt . CA 8,730' VERN /L TUN NEL 

(££VEL 2.),_ _ 

I 
148 MAGDALENA MINING DISTRICT, NEW MEXICO 

yon. Drilling, however, may prove that the base of 

the limestone is not quite so deep. 

CONNELLY TUNNEL . 

The Connelly tunnel cuts the Grand Ledge fault 

1,800 feet south of the Grand Ledge tunnel. There 

the shaly lower Madera limestone beds are faulted 

against argillite. A number of small quartz veins are 

present in the fault zone., accompanied in places by 

barite and a small quantity of ore minerals. The 

ground was partly caved and was not explored 

thoroughly. 

WEST VIRGINIA TUNNEL 

The West Virginia tunnel, about 900 feet southeast 

of the Connelly tunnel, extends N. 55°-60° E. for 

about 160 feet in Madera limestone and ends at a 

reverse fault that strikes N. 25° W. and dips about 

60° E. The east wall of this fault is pre-Cambrian 

argillite or "greenstone", and it therefore is the main 

fault of the zone, although it must be connected with 

the Grand Ledge fault by a sharp westerly deflection 

or a concealed cross fault a short distance north of the 

tunnel. No veins have been developed in the tunnel. 

VICTOR TUNNEL 

The Victor tunnel, beyond the south boundary of 

the area mapped but in the general direction of the 

main fault zone, follows a narrow pockety quartz vein 

in purple andesite breccia for about 100 feet in a S. 5o 

W. direction. The breast of the tunnel exposes 

stringers of chalcopyrite, galena, and zinc blende in a 

gangue of calcite and quartz. 

Other outcrops and "float" of vein material in the 

vicinity consist of quartz and barite with minor 

amounts of other characteristic minerals. 

MINES AND PROSPECTS EAST OF THE MAIN ORE ZONE 

Workings in the complexly faulted ground just east 

of the Germany fault are mostly on the Sampson, Legal 

Tender, and Grand Tower claims to the north of Kelly 

Gulch and in the Germany min~s to the south of it. 

(See pl. 30.) The Sampson claim lies along the fault 

of northwesterly trend, referred to here as the Sampson fault, that separates the Madera limestone from 

the lower limestone and quartzite members of the 

Sandia formation. The Legal Tender and Grand 

Tower claims, which overlap, include the southern part 

of the Sampson fault and the network of short faults 

crossed by the Tip Top road. 

The Sampson fault may be regarded as a steplike 

continuation of the Germany fault, as it marks the 

principal downthrow to the east that is marked farther 

south by the Germany fault. The intervening minor 

faults are in part branches of the Germany fault and 

in part transverse faults along which small blocks have 

undergone considerable subsidence. The greatest 

amount of subsidence is shown by the small rectangular 

block of Madera limestone bounded by J{elly limestone 

on the west and by the lower limestone of the Sandia 

formation on the other three sides. 

SAMPSON CLAIM 

Only shallow work has been done on the Sampson 

claim, where ore has been stopeq along a fissure, which 

strikes N. 37° W. and dips 70° E. in the Sampson fault 

zone. The ore shoot, as seen in 1916, had been followed 

about 80 feet and showed a northwesterly pitch of 20°. 

It consisted principally of oxidized lead ore that had 

replaced limestone between beds of shale in the Sandia 

formation. Bunches of zinc carbonate, said to average 

35 percent of zinc, were fourid in the down-dip and 

down-pitch parts of the shoot, and zinc carbonate of 

lower grade-reported as 20 percent-was found along 

bedding planes and fractures in adjacent limy shale. 

The only reported shipment was of 33 tons of ore in 

1917 from which 500 pounds of lead and 13,344 pounds 

of zinc were recovered; but other small shipments may 

have been included with other shipments by the owner, 

the Ozark Smelting & Mining Co. 

GRAND TOWER AND LEGAL TENDER CLAIMS 

In the northern part of the Grand Tower and Legal 

Tender claims, the second owned by the Tri-Bullion 

Smelting & Development Co., a row of shallow shafts 

and prospects has been sunk along minor faults of 

north-northwest trend and steep west dip in the lower 

limestone and quartzite members of the Sandia formation. No production has been reported from these 

claims since 1904. The ore, as seen from the surface 

at one of these prospects, has replaced a limestone bed 

in the hanging wall of the fault where quartzite forms 

the footwall. At the southernmost opening of the 

groUlp another small stope occurred similarly in a 

wedge of limestone faulted between two masses of 

quartzite. The limestone above the stope was silicified. · 

A few similar bunches of ore are exposed in shallow 

workings elsewhere on these claims. One of them, 

reached by a short tunnel that trends S. 80° E., just 

. northwest of the cable house on the Legal Tender 

claim, has replaced a slightly domed bed of Madera 

limestone just above a bed of quartzite that may mark 

the top of the Sandia formation. The stoped part of 

this shoot is circular, with a qiameter of about 20 feet 

and a thickness of 4 feet. Southeast of this tunnel, 

short tunnels along faults in the Kelly limestone expose 

small irregular stopes capped by thoroughly silicified 

limestone. 

The ' largest ore body in these claims is reached by 

the Grand Tower vertical shaft, which has been sunk 

a little west of the east boundary of the Legal Tender 

claim. (See fig. 21.) Between 10,000 and 15,000 tons 

of ore are said to have been milled and shipped from 

it, all prior to 1904. 

The mine, as ::;hown on plate 2, is in the midst of a 
MINES AND PROSPECTS' EiAST OF THE< MAIN OR'E ZONE 

Alt.50.3' 

I ' 

50 0 50 Feet 

FIGURE 21.-Plan of Grand Tower mine. Compiled from maps made· by L. P. Pressler for the 

Tri-Bullion Smelting & Development Co., in 1911, and by R. L. Chase in 1912. 

w 

e,ooo' . 

7,900' 

7,eoo' 

100 100 200 feet 

E. 

Upper quartzite member 

Shale member 

Lower limestone member 

alternatin~ beds~ Lower quartzite of pure ana impure_ quartzite end shale. 

c:::r::l. ·, Ket"IJ. limestone, 

t:J:::jjSp "5p"= silver pipe"bed 

FIGURE 22.-Section from the Germany fault through the Grand Tower shaft, looking 

N. 74° E. 

149 
150 MAGDALENA MINING DISTRICT, NEW MEXICO 

network of short longitudinal and cross faults that are 

east of the Germany fault and subsidiary to it and 

bound a group of small depressed blocks. The most 

d~pressed of these blocks is represented at the surface 

by Madera limestone, but the two blocks east of it, 

which contain the Grand Tower workings, are represented by the lower limestone of the Sandia formation.· The geologic structure, insofar as it can be 

interpreted, is shown in figure 22; 

The workings opened by the shaft are within an 

area 250 feet square. The shaft is said to be about 

190 feet deep, but water stood at a depth of 130 feet 

in l916, and no information regarding conditions below 

that depth is available. The shaft cuts the top of the 

Kelly limestone at a depth of 120 feet. A fault is 

exposed just west of the shaft at that level. It strikes 

· N. 5° E, dips 69° W., and corresponds rather closely 

to the fault that crops out just east of the shaft. This 

fault, which at the 120-foot level brings the lower 

Sandia beds against upper Kelly limestone, forms the 

west boundary of an ore shoot just below the shale 

roof of the Kelly limestone. The shoot, which has an 

average width of 50 feet, has been stoped up the dip for 

100 feet in a northeasterly direction. Near its northeast end, which is 80 feet above the southwest end, the 

limestone is cut by a small fault that dips 50°-60° E. 

and passes upw.ard into a roll in the shale. The ore 

follows the roll and continues a few feet beyond the 

fault. The shape of the stope suggests that the ore 

shoot followed a cross fracture between the two faults, 

but no such fracture was noted in the roof or floor of 

the stope. Remnants of sulphide ore in and around 

the stope contain pyrite, zinc blende, galena, and 

chalcopyrite; and low -grade material along the walls 

and floor consists largely of quartz-barite gangue. A 

few small bunches of zinc carbonate, replacing coarse-

. grained limestone, were noted along the down-dip side 

of the stope; and it is therefore inferred that the main 

ore body was in part oxidized. The only development 

above water level outside of the stope are two inclines 

that rise northward at low angles. Only the western 

incline was accessible. It followed the west fault for 

80 feet and showed shale and quartzite of the Sandia 

formation on both sides. 

As the stope is much too small to account for the 

total reported tonnage of ore produced, it seems that 

s0me ore must have come from below the present water 

level. The bottom of the shaft should be near the 

bottom of the Kelly limestone, and a west crosscut 

from it might reach Kelly limestone beyond the fault. 

Ore could be expected at both of these places. 

GERMANY MINES 

The Germany mines, owned by the Germany Mining 

& Development Co., comprise four sets of workings 

that have prospected the ground, half a mile and more 

east of Kelly, between the Germany fault and the north 

end of the Mistletoe fault. Development of this 

ground began in 1906, but, although a great deal of 

work was done, the output, as shown in the table on 

page 152, has been relatively small. The average 

grade of the ores has been distinctly below that of the 

ores in the main ore zone in both lead and zinc, but 

several shipments of lead and dry ores ha~e been much 

higher in silver. A few shipments have contained 

more gold than the average, but they may have included 

small quantities of gold ore from the Stonewall claim 

of the Tip Top and Key mines. The ground, explored 

by the Germany mines, as shown on plate 2, is crossed 

by two faults of east-northeast trend with downthrow on the south that displace· the Sandia and lower 

Madera formations on the surface. The northern 

cross fault is so compensated on its north side by faults 

of northerly trend that the displacement near its 

junction with the obscure northern part of the 

Mistletoe fault is small. The southern cross fault 

maintains a throw of about 400 feet throughout its 

length, thus compensating for most of the displacement along the Mistletoe fault. The lowest workings 

(figure 23) are opened through the main tunnel, whose 

portal is in Kelly Gulch at an approximate altitude of 

7,840 feet. Tunnel No. 1 is 700 feet to the east in a 

tributary of the gulch, at an altitude of 8,0~0 feet, and 

the Alhambra tunnel and "old workings" are on opposite sides of the tributary gulch at altitudes of 8,060 

feet and 8,080 feet. 

The Alhambra tunnel was flooded and inaccessible 

in 1915 and 1916; but the distribution of its workings 

suggests that they have explored the Kelly limestone 

west of the northernmost pa:rt of the Mistletoe fault, 

where displacement along it is small. The eastern 

part of the No. 1 tunnel workings, which explore the 

same ground were also flooded. The western part of 

No. 1 tunnel and the "old workings" above it explore 

the Germany fault, where it curves from a southeasterly to a south-southwesterly course, and a branch 

fault that is essentially a continuation of the southeasterly course. A little ore was evidently stoped 

where this branch fault cut the top of the Kelly limestone in the old workings. Elsewhere the limestone 

was silicified but nonproductive. 

The main or lower tunnel passes in aS. 72° E. direction through argillite, granite, and dikes of pre-Cambrian diabase and felsite, but it was flooded east of 

the Germany fauit in 1915 and 1916. It crosses the 

Germany fault 1,000 feet from the portal and continues 

for 350 feet farther, presumably to the Mistletoe fault. 

Workings extending southward from it have explored 

the ground in the vicinity of the Germany fault for 

about 1,600 feet. A little siliceous zinc sulphide ore 

with a green copper stain was found along a minor 

fissure in Kelly limestone on the east side of· the Germany fault. About 500 feet south of the tunnel, near 
MINES AND PROSPEC'bS! E:AST OF THE MAIN ORE ZONE 151 

s. 

N ~ 

-z_ 

-<.... 

-z_ 

a 

~ 

.4 

1..1\ 

C) 

a 

-z... 

1..1\ 

L_ 

J 

100 500 Feet ~~_.~------~----~------~-----L----~ 

FIGURE 2'3.-Map of the Germany mines showing geology of accessible parts. 
152 MAGDALENA MINING DIS'l'RICT, NEW MEXICO 

Ore mined at Germany mines, 1906-39,1 and its gross metal content 

[Data collected and classified by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Ore Gold (ounces) Silver (ounces) Copper Lead Zinc 

Year 

Class Tons Total Per ton Total Per ton Pounds Percent Pounds Percent Pounds Percent 

-----·--------·---------------------------------------

1909 {Ox~d~zed <?)lead __________________________ _ Ond1zed zmc. ____ __ ________________ _____ _ _ 

1910 Oxidized (?) dry ___ --------------·---- ____ _ 

1912 {Ox~d~zed <?) _Iead ________ ___ __________ __ ___ _ 

Ox1d1zed zmc. __ __ ___ ------------------ ___ _ 

2 1913 {£~~i~~J~:~---~====================== == ==== 2 1914 1915 {8~~~~~~ ___ _ . do ______ ~~~~= ___= 

_____ = = ==== ______ == == == ___= =___== = ___= == ________ = = == == = = _ 

1916 {8~~~~~~ ~~~~= = ====== ==== ================== 

{

Oxidized(?) dry _____ ____ ___ ______ _____ __ _ _ 1917 Oxidized lead. ______ ·r-----_______________ _ 

1918 1920 {g~~~~~ Oxidized t~~tc (?)lead o:~~~~ ______== === ___============= _________ ________ ==== = _ 

1922 {~i~~\~~~ l;~fli<Ie-_-_-: ======================== 1929 Oxidized (?)lead ___________________ ________ _ 

315 

166 

. 44 

35 

36 

'103 

427 

86 

15 

23 

596 

74 

135 1, 044 

112 

242 

12 

37 

38 

75 

68 

14.00 o. 04 671 2.1 9, 891 1. 6 . 103,080 16.4 ---------- ----------

---------- ---------- ---------- ---------- ---------- ---------- ------------ ---------- 66, 862 20. 1 0 87 0 02 1, 682 38.2 ---------- ---------- ------------ ---------- ---------- ---------- ---··------ ---------- 53 1. 5 71 .1 10,295 14.7 ---------- ---- --- --- ---------- ---------- ---------- --- --·· ---- ---------- ---------- ------------ ---------- 22, 500 31. 3 12.90 .13 4,652 45.~ 9,875 4.8 25,452 12.4 -------------------- 121.84 .29 12,285 28.8 14,661 1.7 87,583 10.3 ---------- ---------- 93. 41 1.09 387 4.5 139 .1 38,103 .22.2 ---------- ------ -· --

---------- ---------- ---------- ---------- ---------- ---------- ------------ ---------- 9, 600 32. 0 

---------- ---------- ---"------ ---------- ---------- ---- ------ ------------ ---------- 14,431 31.4 7. 43 . 0 01 1, 833 3.1 11,610 1. 0 194,653 16.3 ---------- -------- --

---------- ---------- ---------- ---------- ---------- ---------- ------------ ---------- 50,038 33. 8 2. 00 . 01 1, 843 13.7 3, 849 1. 4 10,397 3. 9 ---------- ---------- 20.68 0 02 3, 139 3. 0 11, 127 . 5 450, 381 21.6 ---------- ---------- 9.00 . 08 4, 061 36. 3 10, 119 4. 5 24, 126 10.8 ---------- ---------- 5.50 .02 862 3.6 2,203 1.5 99,755 20.6 --------------------

---------- ---------- ---------- ---------- ---------- ---------- ------------ ---------- 5, 856 24.4 56" 1. 5 968 25.5 

0 30 ---------- 104 1.5 

395 

836 

279 

0 5 1.1 

0 2 

13,655 

13, 565 25,500 

14, 193 

18. 5 ---------- ---------- 17.8 ---------- ---------- 17. 0 30,000 20.0 

10.4 ---------- ---------- -------------------1-----1----·1--------- 3, 683 287.93 ---------- 32,596 ---------- 75,055 ---------- 1, 110,738 --------- - 199,287 ----------

I Development or assessment work but no production in 1906-8, 1911, 1919, and 1921. Mine idle in 1923-28 and 193Q-39. 2 Shipments for 1913 and 1914 may include those from the Tip Top and Key mines as well as the Germany mines. 

the projected position of the northern cross fault, the 

Germany fault is either offset or bends abruptly westward and sends an east branch along the cont~nuation 

of its regular course. The lower Kelly limestone along 

this branch fault is replaced by quartz, barite, and calcite, and minor fissures between the east branch and 

the main fault are filled with quartz. These fissures 

either end southward or are deflected along a lamprophyre dike that parallels the cross faults. A little 

farther south a replacement deposit of sulphide ore 

about 2 feet thick is exposed at the junction of the topmost Kelly bed and a minor fault that strikes southsoutheast and dips 70° E. The deposit has been 

explored in a winze along the top of the Kelly limestone and another minor branch fault that follows a 

lamprophyre dike and has a small downthrow on the 

west. The ore is a coarse-grained mixture of galena, 

zinc blende, pyrite, and microscopic chalcopyrite in a 

gangue of quartz, calcite, barite, and siderite. It has 

been followed south-southeast along the branch fault 

and passes into a vein of calcite, whose scalenohedrons 

indicate the waning end of local mineral deposition. 

The fault and vein have been followed for 530 feet 

from the winze to the south end of the mine. 

The evidence throughout the accessible parts of the 

mine indicates that, although early silicification took 

place rather continuously along and near the Germany 

fault, it was confined to fissures and the adjacent limestone; also that the later ore-forming stage supplied 

only small quantities of sulphide ore to minor tension 

faults near the main fault and was too weak to effect 

perme-ation along the bedding of the limestone. 

LITTLE LOELLA CLAIM 

The Little Loella claim is on the upper west slope 

of the Magdalena Range about 4,000 feet due east of 

Kelly and a little west of the South Stonewall fault. 

Kelly limestone, whose uppermost beds are completely 

silicified, crops out along its eastern part and dips westward beneath the basal Sandia beds. Accessible workings include three tunnels in the upper-Kelly limestone. 

The lowest tunnel extends for 65 feet in a N. 62° 

E. direction, beginning in the silicified beds and passing 

·into the underlying unaltered limestone. A drift extends north for 30 feet from the breast of the tunnel. 

At the north end it exposes a lamprophyre dike of 

northeast trend and also a little zinc carbonate that has 

replaced limestone just below the silicified top. 

The two upper tunnels trend northward and follow the 

upper and lower sides of a stoped ore shoot that has 

replaced the limestone just below the silicified top for 

a maximum length of about 150 feet, a maximum width 

of about 25 feet, and a thickness of 3 or 4 feet. The maximum length is along the upper tunnel. The maximum 

width persists for about 60 feet and the down-dip side 

of the stope then turns northeastward and converges 

with the relatively straight up-dip side. The roof and 

floor of the stope consists of quartz and barite. Remnants of the ore consist of galena in a honeycombed 

quartz-barite gangue from which zinc blende and 

probably some pyrite and chalcopyrite have been 

leached. The ore is acco~panied by yellow and red 

earthy material, probably plumboj arosite in part, and 

a few green copper-stained streaks. The ore is said 

to have averaged 16 percent of lead after careful sorting. 

The lower of these two tunnels follows the down-dip 

side of the stope for 60 feet and continues 90 feet farther in a N. 6° E. direction in the silicified top beds of 

the limestone. A filled winze at the north end of the 

tunnel may have reached some high-grade zinc carbonate, as carbonate was seen on the dump but nowhere 

in the 1nain stope. It could also have come from a 
• 

MINES AND PROSPECTS E:AST OF THE' MAIN OR'E} ZONE 153 

hole about 8 feet square in the floor of the main stope, 

but the quartz walls of the hole suggests that it 

contained lead ore. 

TIP TOP AND KEY MINES 

The Tip Top and Key mines are in Tip Top Mountain, a mile northeast of Kelly. They are in the Key 

group of 16 claims, but their wot kings, which are 

continuous, are confined to the Tip Top, Stonewall 

North, Key, and Key No. 2 claims. They were worked 

by the Mine Development Co. from. 1900 to 1909 and 

were taken over by the Germany Mining & Development Co. in 1910. The only recorded output, according 

to the Denver office of the Geological Survey, is shown 

in the following table: · 

Ore shipped from Ti p Top and ;Key mines, 19,07-9, and i t s gross 

metal. content 

Ore Silver (ounces) Le ad 

Year Total I Class I Tons P er Pounds Percent (gross) I ton (gross) 

------

1907 Oxidized lead ______ _____ _ 1, 000 2,000 2. 0 309, 600 15. 5 1908 _____ do __ ----------------_ 50 100 2. 0 15, 477 15.5 1909 _____ do ___________________ 29 59 2.0 11, 994 20.7 --

1, 079 2, 159 -------- 337, 071 

Shipments were reported to have been suspended in 

1907 and limited to two carloads in 1908 and one car-. 

load in 1909 because of the low price of lead. The 

price did not improve appreciably until 1916,' but even 

then the mine remained idle. 

Some additional shipments from the Key group of 

claims may have been included in the output of the 

Germany mines (p. 152) in 1913 and 1914. They probably came from the Stonewall tunnels and were made 

because of their unusually high gold content. (See 

p. 155.) 

The portal of the Tip Top tunnel is on the south 

slope of Tip Top Mountain at the end of the road on 

the upper north slope of Kelly Gulch at an approximate altitude of 8,520 feet. The portal of the l(ey 

tunnel is on the north slope on the east side of the 

1nain range about 2,000 feet north-northeast ·of the Tip 

Top portal at an approximate altitude of 8,540 feet. 

The two tunnels are connected (fig. 24) by a z1gzag 

set of drifts and crosscuts that follow parts of the 

"silver pipe" member of the Kelly limestone and intervening cross faults. The Tip Top portal is connected 

by a short horizontal track with an ore bin just beyond 

the dump. 

The workings are almost entirely in the Kelly limestone. The underlying granite and argillite are exposed at the Key portal and in a few c:r;osscuts where 

faulting has brought them to the general level of the 

workings. The lm~ver quartzite member of the Sandia 

format! on has .been similarly exposed at a _ few places. 

200889-42-11 

The limestone member above this quartzite 1s cut at 

·and near the Tip Top portal. 

Three sets of faults are present-a dmninant set with 

westerly trend, called the Tip Top fault zone; a subordinate set with northerly trend; and an obscure set 

of bedding faults, only one of which, a low-angle revers.e or thrust fault within_ the "silver pipe" bed, has 

been ma.Pped. Most of the west-trending faults in the 

northern two-thirds of the workings. dip 50°-75° N. 

and have. their downthrows to the north. The positions of the larger faults conform to those mapped at 

the surface. (See pl. 2.) A few minor west-trending 

faults, between 600 and 700 feet northeast of the Tip 

Top portal, dip south, have downthrows to the south, 

and appear to represent local settling of n1inor slabs 

within the steplike south bqrder zone of the depressed 

block whose north side is in the vicinity of Oak Spring. 

The local north-trending fa-ults a.re evidently the 

northernmost members of the Stonewall fault zone, 

but here they merely represent adjustments within the 

slabs between the larger west-trending faults. The 

thrust fault that nearly coincides with bedding within 

the "silver pipe" bed is exposed along a short, stub 

drift 900 feet south of the l(ey portal. Its only signi-. 

ficance is to show that this kind of faulting took place 

in the eastern part of the district as well as elsewhere 

and to imply that similar slips have made minor openings along other beds and rendered them more susceptible to permeation. 

The only ore shoots found ha.ve been small and scattered and with one exception have been in the lmver 

and upper Kelly limestone at or near the intersections 

of west-trending and north-trending faults. The exception is along the short drift extending northward 

from the Tip 'Top tunnel, where the lower part of 

the lower limestone member of the Sandia formation 

contains small bunches of ore along or near an obscure west-trending fault. The same limestone, 130 

feet farther east, has been replaced by a shoot of 

northerly trend that probably cropped out originally 

and was mined through a short tunnel. The l(elly 

limestone between smne of the closely spaced productive and unproductive faults in the central part of the 

workings is considerably silicified, and one fault between the two most silicified areas contained coarsegrained calcite. Complete oxidation of such ore as 

could be seen prevented a thorough recognition of the 

-original ore, and gangue minerals, but they evidently 

represent deposition rather far from the source of 

supply. 

STONEWALL TUNNELS 

The Stonewall tunnels, all with easterly trend, have 

explored the Kelly limestone in the southern part of 

the Stonewall, North claim. They were owned by the 

Germany Mines Co. in 1913-14, and s1p.all shipme"nt~ 

from them were probably included in those from the 
0 

N. 2s·w Oip 58.E

~ 

.il Gran itc 

~ z ........ 

0 30 60 so feet 

Stop ~ 

TUNNEL 5 

•' 

Sand1 a formation aLong 

top of Kelly 11 mestone "-1 

TUNNEL 3 

\ 

ilver P'~(~ e5tC\ne Upper " r KellY 'te . :-. ed uppe uartll Si1;~f\ic pebbly q . 

Pyn Lead and Z1nc 

(

0 ~ carbonate (probably) 'z-\9_,0' ~ .,& 

"9:~ \'. .J ~ • -<'<" \ '.\ ....,~ ( 

(;> 6~~~\ ' ~ oqs'U 

(g" <1so'JI. ~q ., 

'; ~"t_,os.,9 sU) ~ ~ ~~ " 1-'\i)t..o , Small stope '3 ., ro ...., 

~];ro 

FIGURE 24.-Geolugic map of Tip Top and Key mines and adjacent Stonewall tunnels, 

~ 

1--1-

~ 

~ 

~ 

> 0 

t:::1 

~ t:<J 

z 

p.. 

~ 

z 

z 

0 

t:::1 

1-1 

UJ 

8 

~ 1-1 

0 

...,1-:3 

z 

t:<J 

~ 

~ t:<J 

~ 1-1 

0 

0 
MINES AND PROSPECTS E'AST OF THE• MAlNl OR'E' ZONE 155 

w E. 

50 0 100 Feet ~~~~----~----~ 

( 

FIGURE 25.- Vertical projection of. the Stonewall tunnels. 

Germany mines in those years. (See p. l52.) No. 1 

tunnel, 640 feet east of the portal of the Tip Top tunnel (fig. 24) begins at the lower "silv:er pipe" bed and 

crosses the base of the Kelly limestone, along which a 

thin streak of p'artly oxidized siliceous lead ore is· exposed. The tunnel continues through pre-Cambrian 

granite as far as the North Stonewall fault, where the 

Inain "silver pipe" and upper l{elly limestone beds 

in the hanging wall lie against the granite footwall. 

,The fault there strikes N. 20° W. and dips 37° E. 

The f1:actured limestone and granite contain coarsegrained iron-stained calcite and clay, but no ore minerals were noted. The No. 2 tunnel, 200 feet north 

of No. 1, also begins in Kelly . limestone and cross<~s 

the North Stonewall fault, which there dips 60° E. 

(See fig. 25.) East of the fault it continues southeastward through upper Kelly limestone, which dips 

20°- 30° W. and has been replaced by soft clay stained 

by black manganese and brown iron oxides. The main 

"silver pipe" bed is exposed in the breast of the 

tunnel. A branch of the tunnel extends southward 

for 50 feet through the soft ground, and a short winze 

and two raises extend from it along the fault. The 

winze was said to have exposed partly leached quartz 

and rather low grade lead carbonate along the footwall side and some zinc carbonate ore averaging 35 

percent of zinc along the hanging wall; but the only 

material noted in the winze in 1916 was soft porous 

material stained by the black manganese and reddishbrown iron oxides that commonly accompany zinc . 

carbonate dep?sits. 

A short distance south of No. 1 tunnel, the North 

Stonewall fault has been opened by a shallow, inclined 

shaft sloping 45° E., along which pyritized shale at 

the base of the Sandia formation in the hanging wall 

has dropped to the level of the main "silver pipe~' bed in 

the footwall. It discloses a thin streak of gold-lead 

ore ju.st beneath the upper "silver pipe" bed or "west 

vein," which locally marks the top of the Kelly limestone. The streak was followed up the dip to the base 

of a local "ro1l," where the dip became nearly vertical 

and the bedding planes relatively impervious. 

No. 3 tunnel, about 250 feet east-northeast of No. 1 

tunnel, has alsc;> opened ore just below the "upper silver 

pipe" bed, which i~mediately underlies pyritized shale. 

The tunnel cuts ail east-dipping quartz-galena vein 55 

feet from its portal. This vein has been followed 

southward for 90 feet and bunches of partly oxidized 

lead ore and zinc carbonate ore have been exposed along 

its wall~. The main ore shoot, found about 70 feet 

south of the tunnel, extends along the limestone bedding on both .sides of the vein. It has been stoped for 

190 feet up the dip and 40 feet down the dip from the 

tunnel level. It ends downward beneath a "roll" in 

shale similar to that described above. The lirp.estone 

beneath the "roll" is cut by a minor, east-dipping fault 

and the ore shoot thickens along the fault and on its 

footwall side, as shown in figure 25. 

Shipments of ore from the main shoot are said to 

have contained 18 to 20 percent of lea9., too little copper 

to be paid for, and averages of 4 ounces of silver and 

0.55 ounce of gold to the ton. The ore above tunnel 

level is said to have been high-grade lead carbonate 

with a small gold content. That below tunnel level, / . 

especially beneath the "roll," contained more gold, some 

sorted lots containing as much as 17 ounces to the ton. 

The gold occurred as minute grains in silicified limestone and was closely assoCiated with barite, galena, 

cerussite, willemite, gypsum, kaolin, and black manganese and brown iron oxides. The 17 -ounce ore came 

from a small wedge-shaped depression at the bottom of 

the stope (fig. 25) where gold had evidently been concentrated by downward circulation, in a trough formed 

by the intersection of the west-dipping beds and an 
156 MAGDALENA MINING DISfrRICT, NEW MEXICO 

east-dipping fault that passed upward into the "roll." 

Small bunches of zinc carbonate have been found on 

both the hanging walls and footwalls of the lead-gold 

stope. 

The small workings up the slope above No. 3 tunnel 

apparently opened ore along the uppermost beds of 

Kelly limestmie. 

AMBROSIA MINE 

The Ambrosia mine, owned by former Senator T. B. 

Catron and under lease to the Mines & Metals Co., of 

·Kelly, in the years 1914-20, is situated on the crest 

of the range 1,500 feet north of the Key tunnel. No 

record of its early shipments is available. Small shipments of oxidized zinc ore made from its old stopes 

in 1914, .1916, and 191g were included with those of the 

Juanita mine, which was leased to the same company. 

Its workings were too much caved to permit study, but 

they are evidently located along a fa_ult that locally 

coincides with the steep westerly dip of the beds. The 

southern ore shoot, which crops out, has replaced the 

uppermost beds of the KeHy limestone on both sides 

of the fault. It has been worked through a shaft and 

a .short tunnel. The stoped ground extends with twc 

interruptions for about 300 feet. Oxidized lead and 

oxidized zinc ores have been mined. 

A lower tunnel, whose portal is along. the trail 500 

feet southwest of the Ambrosia shaft, has been driven 

in a N. g5o E. direction for about 60 feet through the 

lower quartzite of the Sandia formation ·and 120 feet 

in Kelly limestone. Two short drifts extend from it 

along north-trending fissures but with no encouraging 

signs of ore. · 

The North Ambrosia or Ambrosia Extension workings are opened by two tunnels about goo feet nm;th of 

the Ambrosia shaft and a little west of the crest of the 

range. Its workings also are caved, but some zinc carbonate had been taken from them. They are in lower 

Kelly lim.estone to the north of a west-trendincr fault b 

and to the west of a north-trending fault. These faults 

bring the lower Kelly limestone on the west against 

pre-Cambrian felsite. The upper l{elly limestone 'has 

been entirely eroded. 

, SLEEPER TUNNEL 

The portal of the Sleeper tunnel is midway between 

the Key and Graphic tunnels, near the west edge of 

the lat·ge are,a of Madera limestone that is locally 

bounded by a northern continuation of the Germany 

fault. The tunnel (fig. 26) extends S. goo E. for 950 feet 

beginning in pre-Cambrian argillite, crossi~1g the Ger-· 

many fault about 250 feet from the portal, and continuing through the lower limestone and quartzite-shale 

members of the Sandia formation, the Kelly limestone, 

and a few feet of the underlying argillite. 

Development has consisted mainly in following the 

"silver pipe" bed of the l{elly limestone. The north 

drift along this bed shows that the bed has been 

bleached, evidently an effect of weak contact-metamorphism, 1,500 feet away from the nearest exposure of the Nitt monzonite stock. The main workings, which are south of the tunnel, consist of drifts 

and cross cuts that follo~ the "silver pipe" and its 

westerly shifts along · the south walls of two transverse 

faults. These faults strike S. goo W., dip 75°-g5o N., 

and are approximately in line with the northernmost 

transverse faults that influenced ore deposition in the 

Tip Top and Key mines; but there is no _positive indication ·of mineralization along them or adjoining 

north-trending fissures. . 

The only ore found in the mine, so far as we could 

see, was about 90 feet south of the second transverse 

fault, near the intersection of a north-trending fissure 

and a minor transverse fault whose south wall has 

shifted eastward. There a streak of partly oxidized 

galena from 1 to 2 inches thick, which lay just beneath 

the "silver pipe" bed, had been followed by a short raise. 

A small pile of galena seen on the dump presumably 

came from this raise. Another small pile of zinc 

carbonate with some green and blue copper carbonates 

may also have come from this raise or• perhaps from a 

raise farther west along the top of the Kelly limestone. A short distance south of the galena raise, the 

north-trending fissure contains small scalenohedrons 

of calcite and brown iron oxide. The calcite is a characteristic product of the weakest ore-forming solutions 

and therefore may mark the approximate limit reached 

by solutions in this vicinity. 

South of the calcite vein an irregular east crosscut 

has been driven among some intersecting faults of 

northeast and northwest trends along which the lower 

quartzite-member of the Sandia formation is in contact with Kelly limestone, but nothing encouraging has 

been found. . PROSPECTS WEST OF THE MAIN ORE ZONE 

The only deposit that has been productive recently 

in the west ore zone is that along the Waldo fault cut 

by the Waldo tunnel of the Graphic-Waldo mine 

( p. 130). Exploration of the southerly continuation of 

the fault by a crosscut from the Traylor shaft of the 

l{elly niine ( p. 137) was evidently not successful. The 

only workings farther south in this zone are shallow 

prospects along small veins in volcanic rocks, from two 

of which-the Iron Mask and Morning Star-a few 

tons have been shipped. , 

The Iron Mask at South Camp was one o·f the 

earliest claims to be worked, but evidently without 

much success, as the workings were left flooded in 

1gg1 (p. 76). A little work was done on it in 1913 

and 1914, but no output was reported. It was reopened . 

again in 192g but was closed again in 1929 without 

any output, although a small amount of ore was exposed containing chalcocite, other copper minerals, and 
PROSPECTS WEST OF THE· MAIN ORE ZONE 157 

.f I 

G o ·a 

/ H 0 !;' 

100 0 300 Feet 

FIGURE 26.-Geologic map of the Sleeper tu:pnel workin~.s. 
158 MAGDALENA MINING DISTRICT, NEW MEXICO 

argentite ( n' which have been described in the chapter 

on mineralogy. 

The Morning Star group is just north of the Iron 

Mask. It was not accessible to us, but 1 ton of dry 

ore containing 0.5 ounce of gold and 18 ounces of silver 

was reported from it in 1922; 13 tons containing a total 

of 5.8 ounces of gold and 3 ounces of silver was reported in 1934; 71 tons containing 58.0 ounces of gold, 

32 ounces of silver, 248 pounds of copper, and 1,049 

pounds of lead in 1935; and 34 tons containing 28.2 

ounces of gold, 11 ounces of silver, and 37 pounds of 

copper in 1936. 

MINES NORTH OF THE NITT MONZONITE STOCK 

Mines and prospects north of the Nitt monzonite 

stock are few, small, and scattered, and only onethe Hardscrabble-has had any considerable production. 

HARDSCRABBLE MINE· 

The Hardscrabble mine is situated on the upper 

west slope of the Magdalena Range, 4,000 feet east of 

Hardscrabble Camp. Although it is one of the older 

mines of the district, only incidental mention of it has 

been found in historical accounts of the district. It 

was owned by the Copper Ridge Mining & Development Co. in 1915-16 and by I. S. Mactavish of 

Magdalena in 1928. 

No figures showing its earliest output are available. 

In 1905 the ore shipped was claimed to average 4 percent of copper, 30 percent of lead, 44 percent of zinc, 

and 12 ounces of silver and 0.05 ounce of gold to the 

ton.87 Its recorded intermittent output from 1909 to 

1920 is shown in the accompanying table. The copper 

ores mined during this period were comparatively rich 

in both copper and silver, but the lead and zinc-lead 

ores were typically low in silver. No record of 

shipments before 1909 is available. 

Ore shipped from Hardscrabble mine, 1909-39/ and its gross 

· m,etal content 

[Data collected and classified by C. W. Henderson, Geological Survey and Bureau of Mines, U. S. Department of the Interior, Denver, Colo.] 

Ore 

Class 

Gold Silver Copper Lead Zinc 

Tons (ounces) (ounces) (pounds) (pounds) (pounds) Year 

-·--1-------1------ ------ - -----

1909 Copper, sulphide.. 4 63 655 __ __________ _____ _ 

{

Coppersulphide . .. 141 1.00 1,651 15,542 7,931 ______ __ _ 1916 

{~i:~~~~:;:i~:;~= II~ ---~--- -----968' " i5;336' ==== == === ~~~~~: 21917 Leadsulphide __ __ _ 126 376 __ ______ _ 30,388 9,100 

Zinc-lead sulphide. 43 __ _______ _________ ____ _____ 5, 934 22,620 

{

Copper, oxidized. _ 107 . 30 2, 536 Hi, 298 10,277 ________ _ 1918 Zinc-lead sulphide . 85 270 1, 012 1, 350 50, 181 Zinc sulphide.... .. 51 _________ 22 864 

1919 {C_opper ~u~phide ... 48 ---i;o56- --·s;i6o- ==== ===== -----~--- zmc, OXIdized...... 60 --------- --------- --------- --------- 42,000 1920 Drysilver ____ __ ___ 268 2,024 8,178 14,231 ______ _ __ 

TotaL ____ ___ 1,117jl:30 ~ 65,J81 70,111 190,567 

1 Mine 1910-15 changed ownership twice: some assessment work done. Idle 1921-39. ~Assays ?f crude ore reported in 1917 ranged as follows: Copper ore from 8.2 to 9.8 ounces of spver to the ton and 4.88 to 5.76 percent of copper; lead ore, 3.30 to 10.77 ounces of silver to the ton and 8.30 to 16.47 percent of lead; zinc-lead ore, 6.9 percent of lead and 26.3 percent of zinc. 

81 Stevens, H. J., Copper handbook, vol. 5, p. 456, 1905. 

We are indebted to Mr. Oscar Redemann, treasurer 

of the company in 1916, for a map of the mine made 

by H. W. Kitson and for other information. The mine 

(pl. 38) is opened by two old glory holes separated by 

an interval of 25 feet and by three tunnels, the upper 

two of which connect with an inclined tramway that 

extends about one-third of the distance down to the 

camp . . The camp has been deBerted for many years, 

and operation of the mine has been intermittent. 

The glory holes and the upper or No. 1 tunnel are 

in a large lenticular inclusion of metamorphic Kelly 

limestone in Tertiary ( ?) granite. The exposed contacts all show some effects of movement. The limestone mass is about 1,400 feet long, and as much as 

150 feet wide, and extends northeastward beyond the 

crest of the range; but mining has been confined to its 

southwest part. The limestone beds in the eastern part 

of the big glory hole strike N. 65° E. and dip 60° SE., 

forming an acute angle with the boundary fault, which 

strikes N. 30° E. and dips 60°-70° SE., and a nearly 

right angle with a set of fissures along which the 

southern ore shoots lie. For the most part they have 

been converted into light gray, coarse-grained marble, 

but some beds have been replaced by garnet and others 

by wollastonite. No cherty beds characteristic of the 

upper Kelly limestone were seen at the big glory hole, 

although they may be represented by wollastonite beds; 

but a bed resembling the metamorphosed "silver pipe" 

bed lies about j n the middle of the exposed mass, which 

is 60 feet wide. The small glory hole has exposed beds 

containing quartz grains typical of the basal Kelly 

beds. These quartzose beds happen to lie along the 

northwest edge of the limestone mass. The northwest 

edge near the crest of the range is a dark greenish 

gray epidotized rock cut by white rock that contains 

small tourmaline crystals. This rock is bounded conformably on the southeast by garnetized limestone; and 

its position therefore suggests that it represents metamorphosed, impure, basal beds of the Kelly limestone. 

The granite has been considerably altered to sericite, 

chlorite, and pyrite along faults and fissures. It is 

cut by a dike or linear group of dikes of white rhyoli~, 

which trend S. 65° E. up the slope from the portal of 

the lowest or No. 1 tunnel to the north wall of the 

larger glory hole. 

The southeast boundary fault or crushed zone is not 

exposed in accessible underground workings. The 

principal fissure or fault in the mine trends S. 70~ E., 

dips 50°-60° NNE., and e_yidently cropped out in the 

area now represented by the smaller or northern glory 

hole. It has been followed by No. 2 tunnel and is also 

exposed 125 feet lower in No. 3 tunnel. It has not produced any conspicuous offset in the limestone, but the 

underlying granite along it has been considerably 

crushed and altered. Its granite hanging wall has also 

been cut by intersecting minor fissures of northeast antl 
MINES NORTH OF THE NITT MONZONITE' STOCK 159 

northwest trend, and the principal ore shoot reached 

by No. 2 tunnel is in this fractured granite. Other 

fissures trend northeast and essentially coincide with 

the bedding of the limestone. They are most conspicuous in the workings of No. 1 tunnel, where they are 

associated with a transverse fault of north-northwest 

trend and east-northeast dip, and along the southeast 

corne:r of the large glory hole. · 

The ore bodies for the most part have replaced limestone, but they have also replaced shattered granite 

beneath the limestone. The main ore shoot cropped out 

near the southwest end of the limestone; and remnants 

of its gossan, which contains considerabie plumbojarosite, can be seen at the west end of the larger glory hole. 

The glory hole is so caved that its structural <ietails 

are concealed, but the limestone along its west half has 

been largely replaced by honeycombed quartz; the 

"silver pipe" bed forms the hanging wall. The limestone between the "silver pipe" bed and the southeast 

boundary of the inclusion has not been conspicuously 

mineralized. The smaller circular glory hole is on the 

main cross fault. Its bottom connects ·eastward with 

an old stope that extends northeastward for at least · 

60 feet and has an average width of about 35 feet. The 

stope in granite opened by No. 2 tunnel is on the 

hanging-wall side of the main :fault and directly down 

the dip of the fault from the glory hole and the connect~d stope. Boulders of limestone on the floor of 

the stope in granite show that some connection has been 

made with the over;lying stop~s. The stope in granite, 

which follows intersecting minor fissures of northeast 

and northwest trend, is very irregular in outline -and 

contains pillars of pyritized granite. · 

The northern ore bodies, all of which cropped out, 

were worked through No. 1 tunnel. They are all in limestone and lie along fissures or bedding planes of southeasterly dip. The western body, or No. 1 vein, has a 

:footwall of granite; and the eastern body, or No. 3 

vein, has a hanging wall of granite. The ore shoot on 

the middle, or No. 2 vein, which extends upward to 

the southwest and reaches the surface, is also floored 

at least in part by a narrow mass of granite that apparently crosscuts the limestone. 

No. 3 tunnel has evidently been driven to explore the 

ore zone at greater depth, but its breast in 1916 was 

still in granite and considerably· west of the projected 

positions of the westernmost ore bodies. 

The ore 1nined was mostly oxidized· and rich in lead 

and silver, with some oxidized zinc ore in typical relationship; but mixed sulphide ore was found in the 

lowest part of the No. 3 vein in No. 1 tu1mel and i11 

the ore in granite in No. 2 tunnel. The sulphide ore 

was similar to that in the Graphic-Waldo and Kelly 

mines; a;nd, like that ore, it was accompanied hyi 

magnetite-specularite aggregates, which formed casings 

around at least one of the stopes. The shoots in limestone are accompanied by quartz, garnet, epidote, chlo-· 

rite, and calcite, whereas those in granite are accmnpan-ied by quartz, sericite, and chlorite. The walls of 

· oxidized ore bodies contain considerable brown iron 

oxide and green copper carbonate, and the walls of the 

stope in granite were coated with conspicuous amounts· 

of blue copper sulphate. Some black-stained ore from 

an inclined winze along the main :fault was said to 

have unusually large contents of copper and silver. 

ANCHOR MINE 

The Anchor mine is at the end of the road in Anchor 

Canyon, 1~ mile~ east-northeast of Hardscrabble 

Camp. ~twas opened about 1885 and is said to have 

produced rich silver-ore with a total value of about 

$60,000, but it was abandoned aboi1t 1893, when the 

price of silver declined. It was reopened in 1924 b:y 

the, C. & M. Ores Co., of ~1:agdalena, which assumed 

control, through lease and ownership, of seven claims 

with a total area of about 125 acres. This company 

op~rated the mine intermittently until 1926 and treated 

the ore in a mill designed :for both gravitative concentration and flotation. A -lead-silver concentrate was 

made,. and about 20 tons of concentrates was shipped 

· to the smelter in El Paso, Tex., but zinc blende went· 

into the tailings. Operations ceased in 1926. 

The workings (fig. 27) consist of an inclined shaft., 

from which two short levels have been driven, and 

a tunnel 900 :feet long with an average trend of about 

S. 30° E., :from which a raise connects with the shaft 

whose colla:r is 125 :feet above tunnel level. The tunnel and the lower part of the shaft were flooded in 

1929, and the present description is based mainly on 

a report by J. A. Weir, which Mr. Ian E. Mactavish, 

of the C. & NI. Ores Co., kindly placed at ou~ disposal. 

The country rock is coarse--grained Tertiary ( ~) 

granite. It is cut by several dikes of lamprophyre 

· and white rhyolite in the vicinity of the mine. 

The ore occurs in a vein along a :fault whose irregular walls are slickensided and lined with gouge. The 

strike of the vein is about S. 30° E. and the average 

dip 50°NE. It can be traced on the surface with interruptions, and its course to the south of the shaft 

is marked by prospect pits. Its average thickness is 

about 4 :feet and its maximum thickness 6 feet. Its 

ore shoots are shown in figure 27. Its ore is somewhat 

banded, in general quartz :forming the outer parts and 

barite and fluorite the middle. V ugs are numerous, 

and some are lined with black manganese bxide. The 

quartz layer along the 'footwaJl is more massive and 

continuous than that on the hanging wall. 

Between level 1 and the surface the ore was oxidized. 

Its content of gold and silver was rather constant, 

_ averaging about 0.02 ounce of gold and 12.5 ounces 

of silver to the ton. A little lead and zinc were present. 

The ore minerals in the sulphide ore are zinc blende, 
160 

_...__ 

=::f}ump 

-// 

.;-// 

. -" /::/ 

MAGDALENA MINIKG DISTRICT, NEW MEXICO 

N 

50 0 50 Feet ~~--~--L--J __ -L------~-----~ 

FIGURE 27.-Plan and profile of Pfirt of the Anchor mine, surveyed by J. A. Weir for the C. & M. Ores Co. 
GEOLO I AL URVEY 

I 

I 

I 

I 

\. ',, 

I 

I 

( 

' ' ' ...... !:~,..< 

' '\ 

Map of workings suppl ied by the 

Copper Ridge M ining & Development 

Co.in 1916 

LO BBLE ~11 E 

PROFES lONAL PAPER 200 PLATE 

EXPLANATION 

Second 

~ level 

Limestone 

~ Stoped ore bodres 

B 

Surface Strike 

1~1 and dip 

First 

~ level 
MINES NORTH OF THE Nl'l'T MONZONI'l'E STOCK 161 

galena, and native silver, accompanied by small 

amounts of pyrite and chalcopyrite and a negligible 

quantity of gold. The silver, according to E. H. Wells, 

then president of the New Mexico School of Mines, 88 

occurs chiefly as wire silver in the seams and crevices 

of both sulphides and gangue. It is apparently the 

result of some local enrichment in the transition zone 

between oxidized ore and sulphide ore. The crude ore 

mined contained ~bout 3 percent of zinc and 2 percent 

of lead, and, in spite of evident enrichment, only 0.015' 

ounce of gol~ and 6.5 ounces of silver to the -ton. 

Smelter returns on the two shipments of concentrates 

were as follows : · 

Weight (tons) Gold (ounoo I Silvo<(oun""' I Load to the ton) to the ton) _ (percent) _ 

4. 25 0. 07 56. 8 I 41. 6 

8 . 05 65.3 I 50. 3 

Assays of the tailings showed that ·practically all the 

zinc, about half of the lead, and 60 percent or more 

of the silver (4 ounces to the-ton) were lost. 

VINDICATOR MINE 

The Vindicator mine, on the east side of Hardscrabble Valley, northeast of Hardscrabble Camp, consists 

of nine claims that cover about 150 acres. These claims 

were purchased by the Grubnau . Chemical . Co. in 

1924-27. They are an elongate group 7,400 feet long 

and from 600 to 1,200 feet wide. The mine was studied in 1929 by Koschmann, in company with Mr. V. 

Carl Grubnau, to whom we are indebted for much of 

the information. 

The property is underlain by Tertiary ( ? ) granite 

and Madera limestone, but the limestone is so extensively covered with alluvium, which is as much as 25 

feet thick, that detailed study of the bedrock is impossible at the surface. Limestone is exposed only along 

the low ledge that adjoins the granite south. of the 

shaft and in the arroyo southwest of the · shaft. The 

limestone in the arroyo contains thin-bedded and thickbedded rock charact~ristic of the lower and upper parts 

of the Madera limestone. The thin-bedded member is 

considerably epidotized. The low ledge adjoining the 

granite is largely bleached and recrystallized and may 

at first be mistaken for metamorphosed Kelly limestone. . 

A dike of white rhyolite with steep easterly or vertical dip lies along the contact between granite and 

limestone and evidently fills a longitudinal fault along . 

which some renewal ~f movement has taken place since 

the dike was intruded. Two transverse faults are indi-

' cated by offsets in the thick-bedded limestone-one, 

about 350 feet south of the shaft, between the two 

ss Oral communication. 

southern exposures shown on piate 2, and another, 

based in part on underground evidence, between the 

mine workings and the northern exposure. 

The Vindicat~r shaft, on the Vindicator No. 1 claim, 

is shown on plate 2 and figure 28. It is vertical for 

100 feet and then inclined 45° W. for an additional 

vertical depth somewhat more than 100 feet. _ ·Levels 

have been driven at depths of 65, 100, 150, and 200 

feet, the 150-foot level being driven from a winze that 

connects the 100- and 200-foot levels along the rhyolite 

dike. The mine is thoroughly dry, in contrast to the 

shallow shafts in monzonite 3,500 feet to the south, 

where the water level is at least 200 feet higher than 

the collar of the Vindic~tor shaft. All the levels extend eastward to the rhyolite dike, which is 40 feet from 

the shaft on the 65'-foot level and 70 feet from it on 

the 200-foot level. Only the 65- and 200-foot levels 

extend appreciably west of the vertical part of the 

shaft. 

The workings are entirely in thick-bedded limestone, 

which is thoroughly fractured and shows no distinct 

bedding planes. None of the limestone is bleached 

or noticeably recrystalli~ed, which is in contrast to the 

outcrops of metamorphic limestone south of the shaft. 

Sulphide ore has replaced the limestone along the 

longitudinal fault and has the rhyolite dike for a hanging wall. The limestone. footwall is very little shattered. The ore has been exposed on the 100-, 1'50-, and 

200-foot levels, as shown in figure 28. Two carloads, 

mined between the 100- and 200-foot levels and totaling · 

76 tons, were shipped to the El Paso smelter in 1929. 

Their assay contel}.ts were as follows: / 

Assay contents of sulphide ore from Vindicator mine 

Gold Silver I 

Tons (ounce to (ounces to Lead Copper Zinc 

the ton) the ton) (percent) (percent) (percent) 

------------------------ CarL _______________ _ 36 0. 015 2. 96 7.45 1. 22 13.8 Car 2 _______________ __ 40 '(!) (1) 10.55 (!) 18.55 

1 Not determined. 

Before the present ownership, some lead ore had 

been shipped from the Vindicator No. 8 (formerly the 

Jupiter) claim, but nothing is known of its quantity 

or. metal content. __, 

A considerable quantity of spongy brown iron oxide 

has been exposed. The principal exposure, which has 

been followed by ·the shaft for more than 100 feet 

from the surface, has an east-west extent of more than 

115 feet on the 65-foot level. A second exposure, at 

the bottom of the shaft, extends more than 50 feet in 

both north -south and east-west directions; and a third, 

on th~ 150-foot level, extends along the. footwall of the 

vein for at least 50 feet' and is as, much as 25 feet in 

width. Assays· of the iron oxide, according to Mr. 

Grubnau, showed the following contents of lead and 

zinc: On the.100-foot level, across the south side of the 
162 MAGDALENA MINING DISfi'RICT, NEW MEXICO 

EXPLANATION MAIN SHAFT 

m 

Limestone 

-

Gossan 

[SJ 

Sulphides 

N 

PROFILE. ALONG LINE A-A' 

25 SO FEET ~~~-L----~~----~ 

0 

FIGURE 28.-Geologic map of the Vindicator mine and cross section looking S. 77° W. By V. Carl Grubnau, with minor modifications. 

shaft, 0.3 percent of lead and -D.8 percent of zinc; average on the 150-foot level north of the winze, 1.0 percent 

of lead and 2.1 percent of zinc; grab sample at the 

crosscut north of the shaft, on the 200-foot level, 0.8 

percent of lead and 5.1 percent of zinc. ' 

A chemical analysis · of a sample submitted by Mr. 

Grubnau in 1935 is quoted on page 116. This sample 

cont~ined considerable barite and quartz and was evidently similar to the gangue of the main vein, but the 

iron oxide examined by us underground appeared for 

the most part to have resulted from the direct replacement of lil_llestone. The spongy character and the local 

"box-work" structu;·e of the iron oxide give it some 

resemblance to the gossan of leached zinc ore ; but 

similar structure has been produced by the direct re..: 

placement of limestone by brown iron oxide along 

grain boundaries and minute fractures followed by the 

leaching of any unreplaced limestone. 

The amount of iron oxide along the fault is too 

large to be interpreted solely as a gossan resulting from 

the partial replacement of limestone by zinc sulphide 

ore and its subsequent leaching, although such a 

process m:ty have contributed to it. The source of the 

iron, therefore, is not clearly understood, but it was 

presumably above the present erosion surface in 

pyritized rock similar to the bleached volcanic rock 
FUTURE: OF THE D~SrrRICT , 163 

to the southwest on Stendel Ridge. Volcanic rocks, 

shown in figure 2, undoubtedly once overlay the rocks 

of the Vindicator mine. They may have been strongly 

pyritized in the vicinity of the intersecting faults in 

and near the mine; and, together with the underlying 

limestone, they may also have been impregnated with 

small amounts of lead and zinc, which are reflected in 

the assays quoted above. According to this interpretation the iron oxide is not a reliable guide to zinc 

sulphide ore. Regardless of its significance, however, 

evidence in the district as a whole would favor exploration of the fault intersections south of the present 

workings. Ore bodies along such intersections elsewhere in the district have been of small to moderate 

size compared with those in the Kelly limestone. Be-· 

cause of the prevailingly steep dip of the Madera 

,limestone, as shown by surface exposures, the Kelly 

limestone may be 1,000 feet or more below the present 

bottom of the mine, and ground-water level is . 

doubtless considerably above it. 

OUTLYING :PROSPECTS 

CA V ALlER CLAIM 

The Cavalier claim, owned in 1916 by the late E. A. 

Clemens, is located on a low spur due . north of Magdalena Mountain and about half a mile south of the town 

of Magdalena. The vein zone on the claim is close to 

the vertical contact between a dikelike mass of monzonite and the volcanic rocks of Magdalena Mountain 

and is exposed in a sha.llow pit about 50 feet south of 

the shaft. T4e contact strikes northward and is 

closely paralleled by the vein zone, which is exposed 

for a width of more than 24 feet and consists of a set 

of closely parallel quartz veins. The exposed part of 

the zone cuts the volcanic rock, but the vein, according 

to Mr. Clemens, could not be traced up the steeper part 

of the mountain. The quartz is gray and massive and 

contains a few streaks of barite. In some places it contains a sprinkling of zinc blende and galena and in 

other places a sprinkling of pyrite. The zone is somewhat shattered, especially near its' east wall, and is 

partly leached and stained by iron and manganese 

oxides and green copper carbonate. According to Mr. 

Clemens assays of samples containing blende and 

galena showed some silver, and gold colors could be 

obtained from almost any part of the vein; but the 

total metal content evidently had not encouraged more 

than intermittent prospecting. 

MAGNETITE ON MEDLEY RANCH· 

The low rolling ground on the Medley ranch west 

of the town of Magdalena consists largely of rhyolite 

and probably .andesite, and the flat-topped hills in the 

area are capped by a brown weathering vesicular 

basalt. On the west and southwest slopes of one of 

these hills are thinly scattered fragments of' magnet'ite 

used as flu.x in the old South Camp smelter in 1882-83, 

but no magnetite was ever found in place. · One small 

fragment, noted during a brief visit in 1916, consisted 

of_ magnetite in contact with massive vein quartz. This 

association of magnetite with volcanic ; rocks is too 

unusual for an explanation of it to be offered without 

an opportunity to .stud:y the magnetite in place. 

HEISTER PROSPECT 

The Heister prospect is on the Mary Magdalena 

claim in low rolling ground about a mile north of the 

town of 1\1agdalena. The surface around the prospect 

is covered with rhyolite and andesite debris, and the 

vein may be near the contact between the two rocks. 

The vein trends north and is said to be in a mineralized 

belt that extends a niile farther north. The vein material seen in 1916 consists of quartz with irregularly 

distributed barite and galena, but no assay record of 

it was obtained. V anadinite and wulfenite. were said 

to be found with it occasionally . . 

FUTURE OF THE DISTRICT 

Comments regarding ore reserves and future developments in the district have been scattered at opportune 

places throughout this report and are summarized in 

the following paragraphs. 

When a district raaches a dormant stage, after having 

actively produced large quantities qf oxidized and sulphide ore as long as the Magdalena district has, its 

chances of substantial recovery, to the conservative 

mind, seem remote. It would be rash to predict that 

the Magdalena district can never attain its former activity, but a consideration of its known reserves and of 

related geologic conditions afford a basis for some encouragement, particularly along the main fault zone 

of the district, whenever the markets for zinc and lead 

justify development. Gonditions along other zones 

are such that discouraging factors may outweigh any 

that are encouraging. 

MAIN ORE ~ONE S_OUTH OF NITT STOCK 

The cessation of milling in 1927 is said to have left 

a considerable quantity of low-grade sulphide ore in the 

Nitt and Graphic-Waldo mine~ without adequate means 

of treatment. As a large tonnage of ore was mined and 

milled in the Graphic-Waldo mine during the 10 years 

after our study, we have no estimate of the remaining 

tonnage. or its grade. The main ore zone, as well as its 

east, branch in the old Graphic workings, has been 

so thoroughly explored that no great amount of shipping ore can be expected from it, althopgh small operations by lessees may continue indefinitely. The same 

inference applies to the Kelly mine. A systematic 

search in the Sandia and Madera formations along intersections of mineralized fissures in the main ore zones 

of these mines may disclose ore bodies similar to those 

mined through the Ida Hill and Cimarron tunnels. No 
164 MAGDALENA M!NING D!Stt'RICl', NIDW ME1:X:!CO 

information regarding tonnage and grade of ore from 

these workings is available, so no ratio of the costs of 

exploration and mining to the value of production can 

be expressed. · 

Further developments in the Juanita and South 

Juanita mines may disclose further small ore shoots, 

but as the variety of ore already mined is characteristic of that deposited rather far from its 

source and as no promising structural conditions 

have been noted that would suggest the presence 

of undiscovered ore shoots, no great contribution to 

output can be expected from these mines, although the 

Kelly limestone west o£ the west fault in the South 

Juanita has yet to be explored. 

The composition of the vein along the Mistletoe fault 

in the Mistletoe tunnel indicates. that it is nearer to its 

source of supply than are those of the Juanita and 

South Juanita mines. Its position in shale suggests 

that ore shoots along it may be small, and the amount 

o£ water present is an obstacle to development j but the 

possibility that the underlying ICelly limestone, capped 

by shale, may contain substantial ore bodies in shattered 

ground west of the fault is worthy of consideration. The 

difficulty in determining the exact stratigraphic position 

of the shale in the tunnel prevents an estimate of the 

depth to the Kelly li1nestone, but drilling may determine 

the depth and also the presence of appreciable quantities 

of ore. No deep development work has been undertaken 

between the Mistletoe and Linchburg tunnels, but the 

junctions of the Mistletoe fault with the Young America and Linchbur.g faults in the intervening area suggest favorable structural conditions; furthermore, the 

south-southeast trends and steep dips of the two faults 

are about parallel to that of the Kelly-Graphic fault to 

the north and suggests that the Kelly limestone along 

their west walls may have been as permeable as it was 

in the Kelly mine. 

The Linchburg ore body with its accompanying hightemperature minerals along the Young America}ault 

implies a center of mineralization nearby. Lack· of 

data on development through the Linchburg tunnel 

prevents an expression of opinion regarding the 

strength of this center as compared with those of the 

Graphic-W alclo and Kelly mines, but the character 

of the ore seen by us lends support to the idea that 

. Kelly limestone along the west side of the fault is 

worthy of further attention whenever the price of zinc 

and lead are sufficient to offset the costs of mining and 

milling. The shallow ore mined along the Grand 

Ledge fault, which is essentially a so1Ithern continuation of the Young America fault, encourages deep exploration of the Kelly limestone farther south. In 

short, the Kelly limestone along the main fault zone 

south of Chihuahua Gulch offers the best outlook for ore 

reserves in the district. The Linchburg tunnel affords 

drainage and haulageway at an altitwj~ 9f about 8,050 

feet, but drilling may show that a deeper outlet is desirable, primarily for drainage but also as a haulageway :f'or a large amount of ground. Small ore bodies 

may be found above the Kelly limestone, but will · 

hardly justify explo.ration unless incidental to the 

exploration o£ the Kelly limestone. 

AREA EAST OF MAIN ORE ZONE 

In the area east o£ the main ore zone it is most convenient to trace conditions £rom south to north. East 

of the Grand Ledge, Young America, and Mistletoe 

faults the Kelly limestone is either at or near the surface and has been rather thoroughly explored. The ore 

found in it was evidently formed by solutions that rose 

through the shaly ground along these faults and became 

dispersed along minor faults. Other ore bodies similar 

to those in the Black Cloud mine may await discovery, 

· but their expected extent and grade do not justify much 

outlay fo~· exploration and development. 

North of Chihuahua Gulch the east-dipping Germany fault was too tight to permit appreciable circulation of ore-forming solutions, and the small showings of ore along minor faults east of it in the 

accessible part of the Germany mine are discouraging. 

A greater output has been reported from the Germany 

mine than can be accounted for by these showings, and 

it is inferred that ore along minor faults was mined 

through the upper workings. The ore mined in the 

Grand Tower mine and in the Sampson claim al~o · 

proves that the much-faulted ground east of the Germany fault vYa s permeated by ore-forming solutions, 

but the character of the ore seeri indicates remotene~s 

from any center of mineralization and the improbability of finding sufficiently continuous ore shoots to 

justify costly exploration. It is a reasonable inference that the ore in this faulted ground was formed 

by solutions that rose from the Kelly center, wormed 

their way through the pre-Cambrian block between th~ 

Kelly-Graphic and Germany faults or along cross 

fractures beneath the down-faulted shaly ground just 

north of it, and dispersed along the minor faults. 

One cannot help wondering whether ore shoots of 

considerable size may exist in Kelly limestone beneath 

this down-faulted shaly area, but the facts that the 

ore shoots in the Kelly mine dwindled in this vicinity, 

wbere the associated faults curved from a northnorthwesterly to a northerly trend, and that faults 

east of the shale area have a northerly trend as well 

as dominantly lm:v easterly dips discourage the expectation of anything more than small scattered shoots, 

some of which may be found along the transverse fan1t 

zone that connects with the Tip Top and Key ground. 

The ground developed through the Sleeper tunnel 

north of this transverse fault zone has proved to be 

barren, and prospects still farther north around Oak 

Spring have been unproductive although they and the 
FUTURE' OF THE DISTRICT 165 

associated metamorphic rocks show the effects of considerable mineralization. One of the faults just south 

of Oak Spring strikes north-northwest, with downthrow on the west, and is therefore similar in attitude 

to the faults along the J(elly ore body. The fact that 

the Sandia strata along this and neighboring faults 

have been weakly mineralized suggests that ore bodies 

may be found in the underlying Kelly limestone. The 

weathered metamorphic shale effectively conceals evidence of transverse or other minor faulting that might 

help to localize ore shoots in this small area, and the 

suggestion of ore therefore is very speculative. 

WEST ORE ZONE 

The west ore zone, along the Waldo fault, has been 

explored in the westernmost parts of the Graphi~­

W aldo and Kelly mines, but no information has been 

obtained regarding the quantity or grade of ore found. 

Considerable work was done on the east side of the 

fault in the Graphic-"\Valdo mine, and· the fact that 

the mine was unwatered in 1928 in1plies the presenee 

of an ore reserve that is awaiting more favorable market conditions. Workings in the J{elly mine reached 

the Kelly limestone on the east side of this fault but 

were soon abandoned. · This fact, together with the interruption of the Waldo fault by one or more transverse faults between the two mines suggests that little 

mineralization took place along this zone as far south 

as the Kelly mine. The thickness of volcanic rock on 

the west side of the Waldo fault is roughly estimated 

to be 1,500 feet, and the vertical depth to its base close 

to the fault should accordingly be 2,000 feet or more, if 

its dip of 45°-50° persists. If the underlying Madera 

and Sandia · formations are as thick here as they are 

east of the fault, they should increase the' vertical 

depth to the Kelly limestone by another 1,500 feet. 

The total depth 'of 3,500 feet, together with the cost 

of pumping, seems prohibitive. 

A fault equivalent to the Waldo fault in general 

position and attitude separates pink rhyolite and red 

rhyolite from purple andesite in the foo_thill area south 

of Kelly. Small veins along or near the fault have 

been opened by shallow prospects, but the Iron Mask 

and Morning Star claims at South Camp are the only 

ones, so far as known, that have been at all productive. 

The Iron Mask vein has much the same structural and 

special relations to the Linchburg center of minerali~ 

zation as the vein along the Waldo fault has to the 

Graphic-Waldo center. It is reasonable to expect ore 

shoots similar to the Iron Mask at intervals along ~he 

fault zone, but the fact that the Iron Mask mine has 

been so little developed since the early '80's Implies 

that profitable mining below the shallow ground-water 

level is unlikely. The depth to underlying sedimentary 

rocks cannot be closely estimated because of unconformities in both the volcanic and sedimentary series. 

Rough calculation would place the top and bottom ofthe Madera limestone at depths of 1,000 and 1,500 feet 

and the top of the Kelly limestone at a depth of 2,300 

feet or more. "\Vhether the Kelly limestone, however, 

is appreciably mineralized along the fault is uncertain, 

because it is not known whether the shallow ore along 

the fault zone was introduced from a local deep center 

of mineralization or by solutions that worked their way 

upward and westward from the Linchburg center. 

The zone of mineralization still farther west indicated by the bleached rhyolite on the isolated low hill 

1lj2 miles west of Kelly is of little inte~est, as the evidence of mineralization . other than bleaching is weak 

and the depths to strata that have been productive 

elsewhere a~e too great and obscure to encourage 

exploration. 

ORE ZONES NORTH OF NITT STOCK 

Deep exploration in the faulted ground along Hardscrabble Valley is entitled to more consideration than 

it has received, as the evidence of sulphide deposition 

both in the monzonite and in the Madera limestone of 

the Vindicator mine justify the 'inference that the Kelly 

limestone may contain ore bodies of considerable size. 

The ground-water surface, furthermore, rna y be so deep 

that underground drainage would be feasible and 

pun1ping from the Kelly limestone would be corre-· 

spondingly reduced. 

There is little more to expect from the vicinity of 

the Hardscrabble mine, as ore deposition in appreciable quantity has been restricted to the limestone inclusion in Tertiary ( ? ) granite. The recent effort to work 

the Anchor mine offers little encouragement for prospecting in the granite area. 

GRANITE MOUNTAIN AREA 

Although the presence of magnetite and serpentine 

near the southeast base of Granite Mountain implies a 

local center of n1ineralizatio_n, the surrounding shaly 

and volcanic rocks and the small size and low grade of 

veins exposed by small prospects in them offer little 

ei1couragement to further exploration. The prevailingly steep dip of the formations renders the depth to 

the Kelly limestone too great to encourage sinking to 

it. Farther east, where the Kelly limestone is exposed, 

the evidence of mineralization is weak and the best 

that could be expected by :further exploration would be 

small ore bodies with quartz-barite gangue. The water 

level in the area is so shallow that no great amou~t of 

oxidized or enriched ore seems likely. 

\ . 

INDEX 

A 

Page 

Abo sandstone, description of _______________________________ .. _________________ 2o-22 

fossils in .... ___ .................. ________ ........ _ .. _ .. __ .. _ .. _ .... __ .. _ ........ ______ .. _ .. __ .. ___ ~ ____ 21-22 

near Patterson Canyon, section oL .. ___ _____________ _______ ________ ___ ____ 21 

Abstract_ ___________________ ---------·-- ........ _________ .. ____________ ______ _____ ...... 1-3 

Acknowledgments for aid ___________________ ---------------------------------- 3-4 

Actinolite, occurrence oL .. ______________________ _ _ _ __ ____ _ __ _ __ _ _ __ _ ___ __ ___ 100 

Alluvium, occurrence oL ___ -----------------~------------- -------------------- 22 Alteration of rocks and ores ___________________________________________ 47-55, 1U~-123 , 

Ambrosia mine, features oL __ .. _____ -------------------------- -------~- ------- 156 

Analyses of rocks and ore ________ .. _________________________ .... _ 11, 31, 39, 44, 92, 93, 116 

Anchor mine, description oL __ .. ________________ .. ___ .. ______________________ .. 159--161 

Andalusite, occurrence oL .. __ ........ ___________ .. ___ _ ___ __ _ ____ _____ ____ ____ ___ ___ 99 

Andesite, analyses oL __ ........ __________________________________________ .. ___ .. --" 31 

occurrence and character oL ____ .. _________ ...... ________ 25, 27,28-31, pis. 10, 11, 12, A 

Anglesite, occurrence oL ...... __________ .. ___ .. __ ___________________________ .. ___ ____ 97 

Antigorite, occurrence oL ________________________ ---------------------------- 101 

Antlerite, occurrence oL _________________________ .. ______ _____ ____ ____ ____ ___ ___ 96 

Aplite dikes, description oL---- ---------- ---------------~--------- ---- 4o-41, pl. 2 

Aragonite, occurrence oL _______ .. ___ .. _____ .... __________________ .... _____ .... ----r-- 103 

Argentite (?) occurrence oL ...... ______ ___ ________ .. ___ ___ _____ ___ ____ ________ ___ 98 

Argillite, character and occurrence oL ________________________ .. ______ __ __ _ _ __ _ 7-8 

Augite andesite, description oL ________ -_ __ ----------------------------- 35-36, pl. 13 Aurichalcite, occurrence ·or__ ______ .. --~________________________________________ 93 

Azurite, occurrence oL __ .. _ .. _________________ .. _____ .... _________ .......... ___________ 96 

B 

Banded rhyolite, description oL ______________________________________________ 27-28 

Barite, occurrence oL ___________ ___ ---~----- __ ____ ___ __ ___ ____ _ _ ___ _ ___ ______ 103 

Bibliography .. ___ ...... __________________ .. _ .......... _ .. .... ___ .. _ ...... _ .. _ .. _____ .. _______ .. ___ 4-5 

Biotitization of pre-Cambrian rocks ____________________ ________________ ______ • 12-13 

Black Cloud mine, description oL __________________________________________ 141-143 

ore mined at .... _______ ...... _ ........ ____ .... _ ............ __ .. __ ...... _ ...... __ ...... _ ...... _ .. ___ ............ 142 

Bornite, occurrence oL, ____ ____ ___________ ______________ --.- __ _______ ___ ____ ___ 95 

c 

Cadmium mineral, greenockite, occurrence of.________________________________ 99 

Calcite, occurrence oL ...... __________ ................ · .. _ .... _______________ __ ____________ 102-103 

Carboniferous system, description oL ________________________________________ 14-20 

Cavalier claim, features oL __________ .. _____ .. ___________________ ...... ___ _______ _ _ 163 

Cavern mine, description oL _ .. --------------------------------------------- 145-148 · Celactonite, occurrence or_ _________________________________________ 30,104, pl. 12, A 

origin oL .. -----------...... ___ .. _________________________________ .. _________ .. .... 55 

Cerargyrite, occurrence oL ___________________________ ...... ________ .. _____________ 98-99 

Cerussite, occurrence oL __ .. ________ .. _______ .. __ _________ ___ . __________________ .. .. . 97 

Chalcanthite, occurrence oL ...... .. __________ .. ______ .... __ .......... _______ .. __ __ _ ____ __ 96 

Chalcocite, occurrence oL ________________ _________ L _________________________ 95 

Chalcophanite, occurrence oL __ ---------------------------------------------- 93-94 

Chalcopyrite, occurrence oL .. ____ ...... _· ...... _ ...... _____ · ___________ ........ _ ................ _ .. _.. 94-95 

Chlorite, occurrence oL .... __ _ .. _ .. _________ -·-_ .. ___ .. __ ................ .... _ .... ____ .. __ .. _ _ _ _ _ _ 102 

Chrysocolla, occurrence oL __________ .............. ______________ -------------- ______ 96 

Clay minerals, occurrence oL ___________________________________________ 55,103-104 

Climate of the area ........ _____ .. ________ . _________ -·- ______ ---------- _____________ 6 

Connelly tunnel, features oL __ ------ -------------------------- _______________ 148 

Copper, nativE), occurrence oL__ ___ ___________________________________________ 96 

Copper minerals, occurrence oL _______ _________ _____ _____ . ________ 94-97,108-109,117 

Covellite, occurrence oL -------------------------------------------- __________ 95-96 Crest fault, features oL .. __________________________________ .. ______ ... ___________ 59-60 

Cuprite, occurrence oL _ ------------------------------------------------------ 96 

Cyanotrichite, occurrence oL ...... .... _______________ -----------~----- ____________ 96-97 

D 

Datil formation, occurrence oL ...... _________________________________________ ...... 22 

Diabase, occurrence and character oL .......... ----------------------------"-------- 12 

Diopsidc, occurrence of.. ______________ . ________ --"--------- _______ ........ ________ 99-100 

Dolomite, occurrence oL _____ ...... _ ............ _________________ ---- _____ _ ----------- 102 

Drainage of the area ____________ .. ______________ ................................... _--- ---:------ 6. 

E 

East Slope fault, features oL __________ . ________ _______________________________ 61-62 

Enterprise claim, features of. _______________________________________________ 143~144 

Epidote, occurrence oL ................ _______ .. __ .......... ________ ___ -_, ______ ·_____ ________ 100 

F 

Page 

Faults, age oL ____________ ............ __________ ---~- _ ·-------------.... .. ...... .. .. 57 

interpretation oL .......... .. __________ ____ ...... __________ .. ' .... _________ ...... --------- 65-73 

in the Granite Mountain area __________________ c_________________________ 65 

north of the Nitt stock ______________________ --------------------- 63c-65, pis. 2, 4 

south of the Nitt stock _______ ...... __________ .. _____________ .. 58-63, pis. 2, 20, 31, 32 

Felsite, occurrence and character oL __________________ _____ ___ ---------------- 9 

Felsite tuff, occurrence and character oL__________ __ _________________________ 32 

Field work in the area_ .. _ .. _ .. _ .......... _______ ...... .... _________ ........ --------............ "----

Fluorspar, occurrence oL _______________________________________ --.---- ............ -- 103 

Folding in the area, age and general character of. ........ -.... -----"---------------- 57 

Future development of the area ........ ---------------------------------------- 163-165 

G 

Gabbro, occurrence and character of._________________________________________ 8-9 

Galena, occurrence oL ___________________________________________________ 97,109-110 

Gangue minerals _______ .. __________ .. ___ ........ __________ ........ _________ .............. -- .. -- 99-104 

Garnet, occurrence oL ...... ____ ........ _____ ~ __ ...... __ .. ___ .. _____ .................. --.. ---.. .... .. .. .. .. 100 

Geography of the area ........ _____ .............. _________ • ___ .... ---------------------.......... 5-7 

Germany fault zone, features oL _________ ____ __________________________ 58-59, pl. 20 

Germany mines, description oL ____________ .. _________ _____ ...... -------------- 15o-152 

ore mined at ____________________________________ ........ ______________ ............ __ 152 

Girty, G. H., fossils identified by _____________________________________________ 16,21 

quoted _____________ .......... _________ ...... ___________ .... .......... ___________ ........ __ 16, 19,21 

Gold, occurrence of. _____ .. ___ .......... _ .... __ .. ____ ............ _________ .. __ .... -- ...... -...... 99, 117-118 

Goslarite, occurrence oL _______________ ...... ___________ --------- ---------...... ---.. 94 

Grand Ledge fault, features of ~ .. ___________ -------- --------------------------- 61 

Grand Ledge mine, description and section oL _____________________________ 145-148 

Grand Tower claim, description, plan, and section oL .. --"------------------ 148-150 

Granite, pre-Cambrian ____________________________ --------- 9-11, pls. 5, A, 6, A, B 

Tertiary(?) ________________________________________ ., _____ 39-40, 64, pl. 18, A, C 

Granophyre, origin and character oL _ ---------------------------------------- 41-42 

See also Hybrid granophyre. 

Graphic-Waldo mine, description oL ...... ------------·------------------------ 124-132 generalized section in .. _________ ........ __________________ ...................... __________ 90 

ore shipped from ____________ .. _ .. ____ ...... _______ .............. _________ .. __ .......... _____ 125 

Greenockite, occurrence of.. ........ _____ ...... _ .. _________ .......... -----...................... -----.... 99 

"Greenstone." See Argillite _____ .......... _____ .. __ ................ ----............ -........ -----........ 7 

Ground-water level in the area ______________________________________________ 118-120 

H 

Hardscrabble mine, description oL .. -~-------------------------------------- 158-159 ore shipped from _______ ........ ______ _____________ ...... ____________ _____ _________ , 158 

Hedenbergite, occurrence of.... _________________ .. ___________ ............ _____ -~.............. 100 

Heister prospect, features oL .. ___________ __ ........ ____ ----------- _______ --------- 163 

Helen Cross group, ore shipped from ___ .. ------------------------------------- 141 Hematitization in the southern area _________ _____ ____________________________ 54-55 

Eemimorphite, occurrence of.. __ ...... ___________ .. _____ .... __ .... _._ .. __________ ...... ---.. 94 

Hornblende andesite, description oL ____________________________ ____ __ 35, pl. 13, B 

Hybrid granophyre, description oL _________________________________ 41-42, pl. 18, B 

Hydrozincite, occurrence of _____ .. _ .. ______ .. _ .. ________ --.. _______ .. __ .... --.... --.. --.. - 93 

Igneous rocks, pre-Cambrian _____ .. _ .... _ .... ____ .. __ "-- __________ ...... ____________ .... 8-12 

Tertiary·(?), effusive __ , _________________ .. -c- ____ --~ ___ ...... ----------- : _____ 23-32 

intrusive ___ _________ ___ ______ .. ___ .. ______________________ .. __ .. _____ .... __ .. 32-47 

Imperial claim, features of.. _________ ---------------------------------------- 143-144 

Intrusion of stocks, local faulting during ______________________________________ 69-71 

Intrusive contacts, alteration far from ________ .. ____ .. __ .. _____ .. _______ .. __________ 51-55 

alteration near __ .. ______________ .... _ .. _______ : .. _____ .. -·- __________ .. --.. --.... -.... 49-51 

Iron,_ Mask vein, features oL _______________________________________ 9~, 96, 98, 156-158 

Iron minerals, occurrence oL _________________________________ 90-92,108-109,115-116 

J 

Jarosite, occurrence of.. __ .. ___ -----""--------------- ___ .. _______________________ 92 

Juanita mine, description oL .. ----".: ::c ______________________________________ 137-139 

ore produced at ....... __________ .. __ .. ____ .... __ .. _______ .. __ -" ____ .. ___ .. _________ ...... 138 

K 

Kelly fault block, diagram of.. ____ .... _____ .. ______ -: ~ ____ ~--: ___ ~ _______ .. __ .. ___ 72 

Kelly-Graphic fault, features oL .. ____ .. __ . ___ .. -~ ___ -~ _ .. --- ___ ·_ -------------.. --- 6G-61 

167 
168 !NDEX 

Page 

Kelly limestone, a?:e and correlation oL ___ ______ ______ ___ _____ ____ ______ 16 

character and distribution oL _ -------------------- _____________ 11- 16, pls. 5, 9, 28 

Kelly mine, description oL ________ ___ ·----------------- ___________ ·--------- 132-137 

ore shipped from___ _______________________________________________________ 133 

Key mine, features oL __ ___ ___ ___ __ ________ _______ ___ _______________ ·------- 1(;3,15-1 

L 

Lamprophyre dikes, occurrence and character uf. ----------------------------- 43 

Landslides, features oL ___________ ___ ___ . _ ------------------------------ ---- __ 22 

Latite, occurrence and character oL ____________________________ 24-25,25-26, pl. 7, A 

Latite dikes, character oL _ _ _______ _ ___ _ __ _ ____ ___ _ ___ ___ ___ __ _ __ _____ ___ _ _ _ __ 33 

Latite porphyry, occurrence and character oL _____________ ------------------- 32-33 

Lead. minerals, occurrence oL ________________ __________ ·-------- ---------- 97-98,116 

Legal Tender claim, features oL __ ___________ -- ------------------- -- ---------- 148 

Limestone, alteration of. _____ ______ _____________ ___ ___________________________ 5D-51 

Limonite, occurrence oL _ _' ______ ____ _ --"- _____ ___ _ __ _ _ ____ ___ __ __ _ _ _ ___ __ _ ___ 91 

Lincb.burg tunnel, features of. ___________________________ ____________________ 144-145 

Little Loella claim, features oL _________ ___________________________________ 152-15:c! 

Location of the area _________________________________ _____ _____ ___ ___ ___ _____ _ 

M 

Madera limestone, description oL ________ ___ _______ __________ ____ __ _____ 18-19, pl. 9 

fossils in _________ __________ ______ _____ ______ _________________ , ___ -------~- 20 

Magdalena group, description oL _______________ __ ____________________________ 16-20 

fossils in _________________________ ____ ________ _______________ _____ __ _______ 19-20 

Magdalena Range, columnar section of sedimentary rocks in __________________ pl. 8 

general features oL _________ ___ _____________________________________ 5-6, pl. 5, B 

Magnetitll, occurrence and character oL ________ ____ _______________ 9Q-91, 163, pl. 23 

Malachite, occurrence oL _ __ ___________ ___ __ _ ____ _ __ _ __ _ __ _ _ __ __ _ _ _ _ __ ______ _ _ 96 

Manganese minerals, occurrence oL _______________ ____ _____________________ __ 99, 116 

Melanterite, occurrence oL --------------------------------------------------- 92 

Mineral deposits, distribution and classification oL _________________________ 104-105 

formed at high temperatures ________ ______ __ __ ____________ ______________ 105-106 

formed at low temperatures ________________ ___ ________ --- ----------------- no formed at moderate temperatures ___________ _____________ ___ __ __________ 106-llO 

Minerals of the area ___________ ______ ______ ______ _________ ________ ___ _______ _ 87-104 

alphabetical list oL _ _ _ _ _ _ _ __ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ ___ __ __ _ _ 88 

Mines of prospects, descriptions oL ________ ______ _____________________ ____ __ 123-163 

See also names of individual mines and prospects. 

Mining in the area, historical sketch oL _______________________________________ 75-82 

Mississippian rocks, occurrence and character oL _____________________________ 14-16 

Mistletoe fault, features oL_ __ _ ________ __ __ _ _ _____ __ _ __ __ __ ___ ___ __ __________ _ 61 

Mistletoe mine, description oL __________ --- ----- ------------------------ --- 141-143 ore shipped from_ ______________________________ ________ _____ __ _________ ___ 141 

Mitchell tunnel, features oL _________________________ ______ , ______ ____ ___ ___ 131-132 

Monzonite group, description oL ____ _________ __ __ __ __________ _ 36-39, pl. 2, 14, 15,16 

Morning Star vein, features oL __ ___ __________________ ! ___________________ __ 156-158 

N 

Natrojarosite, possible occurrence oL ___ _ __ __ _____ _ _ _ _____ _____ ______ _ _ __ _____ 92 

Nitt mine, description oL _____________________________________________ __ ___ 123-124 

generalized section through ___ _ ·----------·-------------------------------- 127 ore shipped from___ _____________________________________ __________________ 121 

0 Oro, production oL ___ __ ____ ___ __ _________________ ___ ______ _____ ______________ _ 82-87 

Ore deposits, alteration oL ____ ___________________________ . _____ ____________ 118-123 

distribution and classification oL _______________________________________ 104-105 

formation oL ___________________ .. ________________________ ___ ___________ 105-11.'> 

historical sketch oL ___ ----------- _________ ______ ____________________ _____ 75-82 

oxidized, occurrence and character of.... _____________________________ ___ __ 115-118 

Outlying prospects ____________________________________________________ ______ _ 1G3 

p 

Pegmatitic material, occurrence oL _ ------------------------ __ _____ ___________ 41 

Pennsylvanian rocks, occurrence and character oL ___________ _____ __________ _ 16-20 

Permian rocks, occurrence and character of. __ ___________ t_ ________________ _ _ _ 20-n 

Physiographfc development of the area ---------------------------- 73-75, pls. 21,22 

Pitchstone, occurrence oL __ ------------------------------- -- --- ___________ ____ 42 

Plumbojarosite, occurrence oL _________________ ----------------------------·-- 97-98 

Pre-Cambrian rocks, alteration oL --------------------------------. ______ ____ 49-50 . correlation oL __ ________ _____________ ___ __ _________ _____ __ __ __ ____________ 13-14 

description of__ ___________________________ ____ ____________ __ ______________ 7-13 

Production of metals in Socorro CouQ.ty and Magdalena mining district, sum- mary oL __ _______________ _________ ________________________________ 82-87 

Prospects. See names of mines and prospects. 

Psilomelane, occurrence oL ___ ___ --------- ___________ ------ ________ c- --- ______ ___ _ 99 

Pyrite, occurrence oL ______ ______________ __ ________ ____________ __ _______ 91,108- 108 

Pyrolusite, occurrence oL__________ ________ _______ _______ _________ ___________ 99 

Pyrrhotite, occurrence oL __ ------------------------------------------ ________ 91 

Q 

Quartz, occurrence of_ _______________________ ___________________________ 101-102,109 

Quaternary formations, character and distribution oL _ ----------------------- 22-23 

R Page 

Relief of the area ___________ ------- ---- --------------------------------------- 5-6 

Rhyolite, analysis oL ___________________ , --------- ------ --------------------- 44 

occurrence and character QL __ _________________ - __ __ --- ---------- 29,31-32,43-44 

Rhyolite porphyry, description oL _ ------------------------------- 33-35, pis. 12,13 

magnetic facies in _______ . __ . _______ .. ______ .---------... --------------.. -- 34-35 

Rocks of the area, alteration oL ___ ___________________________________ 47-55, 12D-123 

character and distribution oL __________ __ . ---- -------.---------.-.------- 7-55 

s Sampson claim, features oL ___ _________________ ------------------------------ 148 

Sandia formation, description of ___________ __ ___ -------- ------- ---------- 16-18, pl. 9 

fossils in ______________________ . __ . ____ __ .--- _____ -~------. -------- -------- 19-20 

Sandstone, replacement of_ _______________ ------------ ----- ------ ------ 41-42, pl.19 

Schist, character and occurrence oL________ ________ ____ _____ _______ __________ 7-8 

Sericite, occurrence __________________ -- .. _----.------ .. -----.-.-.-----,--------- 102 

Serpentine, occurrence oL ___ . ______ . _____ __ . _________ ----------------------- ~ 101 

Shale, alteration oL ______________ _.. _____ . __ __ _ -. -----.------ ----.------ -----~- 50 

Siderite, occurrence oL ____ ___ ____________ --------------------------------.--- 102 

Silicification of the rocks ________________ _______________ __ ________ 53-54, pis. 2, 28 

Silver, native, occurrence of. _______ ---------------------.-.-. -- -- .. ----.--.--- - 98 

Silver minerals, occurrence oL ______________ ----------------.------------- 98-99, 118 

"Silver pipe" beds, occuHence and character oL ----- ~---- ---------- ---- ____ 14-16 

Sleeper tunnel features of.. ________________ .------.-----------------.------- 156, 157 

Smithsonite, occurrence of. _________________ __ .---- ---------"----------------- 92-93 

South Juanita mine, description oL __ ____________ .. ____________ --. _. _______ 139-141 

ore shipped from ______________________ __ ._ --. __ --------------------------- 139 

Spangolite, occurrence oL ____ . _____ __________ ------- -'-- ---------------------- 96 

Specularite, occurrence of. ____________________________ __ -------------------·-- 90-91 

Sphalerite, occurrence oL __________ ------------ ------------------------- 92, 109-110 

Stendel fault, features oL _. ___ _____ __ . __ . __ . _____ - ___ -- _. - _ -------- -------.--- 64.-65 

Stonewall fault zone, features oL. _________ __ ____ __ ________ ____ __________ _ 59, pl. 20 

Stonewall tunnels, description oL _________________ . _ ---------------- ------ 153-156 

Structure in the area, Laramide and Tertiary ___ ---------- -------------------- 57-73 

Laramide and Tertiary, interpretation oL ________________________________ 65-73 

Mesozoic _______ _________ _______ _______ _ . ___ .-.-------.-----------.------- 56-57 

Paleozoic ____ _______ ____ . ___ _________ __ .-.--.----------------------------- 56-57 

pre-Cambrian _______ ___ ____ _____ .. --------------------------------------- 56 summary oL _______________ ____________ _____ ______ _________ 55-56, pis. 2, 4, 20 

Sulphide deposits, alteration of. __ ______ _--~--- ________ -------------------- 121-123 

character and occurrence oL __ _______________ . _____ ------ ----· ---------- 106-110 

See also under indil!idual minerals. 

'.r 

"Tallow clay." See Zinc-bearing clay. 

Talus, occurrence of. __ ___________________ --------- ------ ---------------------- 23 

Tenorite, occurr~nce oL _____ ___________ --------------- ----------------------- 96 

Tertiary(?) rocks, igneous, character and distribution oL ______ __ __ _____ _____ 23-47 

sedimentary, character and distribution oL_______ ____________ ____ _____ __ 22 

Tertiary (?) structure __ _____ . ____ . _______ .--- .. -----------. -- ___ ----- __ ---.---- 57-73 

Thaumasite, occurrence of. ____ --------------------- --------------------------- 102 

Tip Top mine, features oL _____ _______ _________ ____________ ---------------- 153,154 

Topography of the area ____________ ------ ------------------ __ _ ----- --------- 5-6 

Tourmaline, occurrence oL _ ----- -------- ------ _. ____ -- ------- ------ ----------- 99 

Tremolite, occurrence oL _ ------------------- ____ ____ ________ ---- ------------- 100 

Tuff, occurrence and character oL ____ ____________ ___ ____ _ . ___ _______ 24--25, 25-26, 32 

v 

Vanadinite, occurrence oL ___ . -~- ----------------- ----------------- 98 

Vegetation of the area _____ ._ . ___ . ____ ._. -· _____ . ___ ___ -·--- ______ ____________ _ 

Victor tunnel, features oL ____ . __ . ______ -•. _ ------ _ .. --- - _ -- . ~- ---. _ -- _ -- ___ . _ 148 

·Vindicator fault, features oL --------------------- -- ----------·- ------ ------- 64 

Vindicator mine, assay of ore from ___ __ _________________________ _ ------------- 161 

description of ___ ___ ___ . _________ ______ _ .. _. __ . _. ___ . ______ ____ ______ ____ 161-16:3 

w 

0 

Wad, occurrence oL ____ _____ _______ . __ ----. -- ---- ___ -----.-. -- ------- _-. ----. _ 99 

Waldo fault, features of. __ ------ ------ --- ---·-· --------- -------c -· -------- 62, pl. 20 West Virginia tunnel, features of.._______ _______ ___________ ______ ______________ 148 

White, David, fossils identified by _____________________________ . ___________ 18, 19, 21 

' quoted _________ ___ ____ _________ _ . ___ . __ ._ .. __ __ __________________________ 21 

Willemite, occurrence oL ____ ___ __ __ __ __ _______ - _______ . ___ - _- _ --- _ --- _______ _ 94 

Wollastonite, occurrence oL __________________ ---- ------- -------------------- 99 

'Voodland mine, features of.. ____ . ___ . __ . ___ . ________ __ . ____ . ______ ___ --------- 145 

y 

Young America fault, features oL____ __ _ ______ _____ _ ___ _______ ____ ___ ________ _ 61 

Young America mine, features of __ ._------------------- -- --------- __________ i43-144 

z 

Zinc-bearing clay, occurrence of. ______ __ ___ ._________________________________ 94 

Zinc bien de ores, occurrence of. _______ . __ .. .. _________ _____ _____ ___ _________ 92, 109-110 

Zinc minerals, occurrence oL ________ . ______ ____ __________ _____ 92-94, 109-110, 116-117 

Zones of alteration _________ _ . . __________ _____ ____ _______ ____ ________________ 118-120 

~ I