Geology and Ore Deposits 

of the Freeland-Lamartine 

District, Clear Creek 

County, Colorado

GEOLOGICAL SURVEY BULLETIN 103 2_- B

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Geology and Ore Deposits 

of the Freeland-Lamartine 

District, Clear Creek 

County, Colorado

By J. E. HARRISON and J. D. WELLS

GEOLOGY AND ORE DEPOSITS OF CLEAR CREEK, 

GILPIN, AND LARIMER COUNTIES, COLORADO

GEOLOGICAL SURVEY BULLETIN 1032-B

This report concerns work done on behalf 

of the U. S. -Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C.
CONTENTS

Page

Abstract___________________________________._ 33

Introduction and acknowledgments______________________ 34

History..-_____________________________________ 36

General geology_________________________________________ _ 37

Pre-Cambrian rocks...____________________________ _ 37

Idaho Springs formation___________________________ 38

Biotite-quartz gneiss____________________________ _ 38

Sillimanitic biotite-quartz gneiss______________________ 4O

Amphibolite. _______________________________________ 41

Lime silicate gneiss__________________________________ 42

Origin________________________________ 4S

Quartz diorite and associated hornblendite______________ 45

Distinctions between amphibolite, quartz diorite, and hornblendite-___________________________________________ 47

Origin______________________________________________ 48

Migmatite__ ______________________________________________ 49

Granite gneiss and pegmatite.______________________________ 50

Granodiorite______________________________________________ 53

Biotite-muscovite granite___________________________________ 54

Granite pegmatite_________________________________________ 56

Tertiary intrusive rocks________________________________________ 57

Classification __ _________________________________________ 58

Quartz monzonite porphyry_______________________________ 591

Alaskite porphyry_______________________________________ 59

Syenitic bostonite porphyry_______________________________ 60

Quartz bostonite________________________________________ 61

Quaternary deposits-________________________________________ 61

Slump deposits____________________________________ 62

Avalanche deposits________________________________________ 62

Alluvium__________________________________ 62

Structure.. ____________________________________________________ 62

Folds. _____________________________________________ 63

Faults...___________________________________ 65

General statement_________________________________________ 65

Sequence of faulting__________________.__________________ 67

Joints______________________________________________ 70

General statement__________________________-_____________ 70

Regional joint pattern__________________________________ 70

Economic geology.________________________________________________ 73

Production from the district.___________________________________ 74

Classification of the veins_______________________________________ 74

Mineralogy of the veins. _______________________________________ 75

Paragenesis of the ores_________________________________________ 76

Primary ore minerals_____________________________________ 76

Secondary ore minerals____________________________________ 78

Abnormal radioactivity of veins._____________________-_-________ 80

Wall-rock alteration ______________________________________ __ _ 82

Localization of the ore bodies___________________________________ 83

m
IV CONTENTS

Economic geology Continued Page

Persistence of ore with depth________________________________ 85

Hypogene zoning of the ore deposits.._________________________ 85

Description of mines______________________________________________ 87

Ariadne mine________________________________________________ 87

Avalanche mine___________________________________________ 88

Baltimore mine_____________________________________________ 89

Belle Creole tunnel____________________________________________ 90

Bell of the West tunnel_____________________________ 91

Brazil mine___________________________________________________ 91

Brighton mine.____________________________________________ 93

Crazy Girl mine______________________________________________ 93

Diamond Mountain (Lanagan) mine____________________________ 96

Freeland group of mines____________________________________ 98

Golden Rod mine_______________________________________ 100

Harrisburg mine_______________________________________ 100

Invincible mine.______________________________________________ 101

Lamartine mine._____________________________________________ 101

Little Johnie group of mines__________________________________ 106

Lone Tree mine.._______________________________________ 110

Mendick mine_______________________________________________ 112

Miller mine_____________________________________________ 113

New Era mine______________________________________-_________ 114

Poor Man mine_________________________________________ 117

Silver Link mine______________-_-_-_-_---_--_-_--__--------_-_ 117

Teller mine_______________________________ 118

Turner mine._________________________________________________ 118

West London tunnel_______________________-----_-_-_--_------_ 121

Small inaccessible mines and prospects.__________________________ 122

Literature cited__________________________________________________ 124

Index._____________________________--____ ______ 125

ILLUSTRATIONS

[All plates in pocket]

PLATE 2. Geologic map and section of the Freeland-Lamartine district.

3. Vertical projection along the Lamartine-Great Western vein group.

4. Geologic map and section of the Old Stag tunnel.

5. Map showing the location of mines and the distribution of veins and 

dike rocks.

6. Geologic map of the Diamond Mountain mine.

7. Map and sections of the Freeland group of mines.

8. Geologic map of part of the Lamartine tunnel.

9. Geologic map of part of the Miller tunnel.

10. Geologic map of part of the south tunnel of the New Era mine.

11. Geologic map of the Turner mine.
CONTENTS V

Page

FIGURE 3. Index map of Colorado showing the location of the FreelandLamartine district with reference to the Front Range highland 

and the Front Range mineral belt______________________ 35

4. Index map showing the location of the Freeland-Lamartine

district, Clear Creek County.__________________________ 35

5. Variations in modal composition of granite gneiss and pegmatite

and biotite-muscovite granite__________________________ 51

6. Contour diagram of lineations-____________________________ 64

7. Vertical projection through the Little Johnie group of mines___ 66

8. Traces of major veins projected to an altitude of 9,500 feet. _ 68

9. Diagram illustrating the age relations among the fault sets 69

10. Contour diagram of joints ____________ _______________ 71

11. Stereographic diagram showing main joint sets and principal

fold axes___________________________ 72

12. Generalized paragenetic diagram for the primary vein minerals. 77

13. Geologic map of the Avalanche tunnel__________ _______ 88

14. Plan and section of the Baltimore mine______ ___ _______ 89

15. Geologic map of the Belle Creole tunnel.-_____ _-___ 90

16. Geologic map of the Bell of the West tunnel._____ _______ 92

17. Plans and sections of the Brighton and Harrisburg mines. _-__ 94

18. Plan and section of the Crazy Girl mine.__________ ____ 95

19. Plan of part of the workings on the Oneida-Mendick veins.___ 103

20. Geologic map of the lower tunnel, Little Johnie group of mines. 107

21. Geologic map of the middle tunnel, Little Johnie group of mines. 109

22. Geologic map of the upper tunnel, Little Johnie group of mines- 110

23. Plans of the Lone Tree and Teller mines___________ 111

24. Geologic map of part of the Lone Tree tunnel _______________ 112

25. Geologic map of the north tunnel of the New Era mine ___ 116

26. Vertical section through the Turner underground shaft-_--_._ 120

27. Geologic map of the West London tunnel.... ____________ 121

TABLES

TABLE 1. Modes of biotite-quartz gneiss_________________________ 39

2. Modes of sillimanitic biotite-quartz gneiss__________________ 41

3. Modes of amphibolite and related rocks.-__-___________ 42

4. Modes of quartz diorite and associated hornblendite________ 46

5. Amount and type of twinning in plagioclase feldspar in amphibolitic rocks_________________________________________ 47

6. Modes of granite gneiss and pegmatite_____-_____-__--______ 51

7. Modes of biotite-muscovite granite.________________________ 55

8. Classification of the Tertiary intrusive rocks-______________ 58

9. Radioactivity of samples collected from mines and mine dumps. 79

10. Data on small inaccessible mines and prospects_____________ 123

GEOLOGY AND ORE DEPOSITS OF CLEAR CREEK, GILPIN, AND LARIMER

COUNTIES, COLORADO

GEOLOGY AND ORE DEPOSITS OF THE FREELANDLAMARTINEJDISTRICT, CLEAR CREEK COUNTY,

COLORADO

By J. E. HAEEISON and J. D. WELLS

ABSTRACT

The Freeland-Lamartine district, Clear Creek County, Colo., forms part of 

the Front Range mineral belt, which is a northeastward-trending belt of coextensive porphyry intrusive rocks and hydrothermal veins of Tertiary age. 

About $18 million worth of gold, silver, copper, lead, and zinc had been produced 

from the mines in the district between 1868 and 1953.

The bedrock in the district is pre-Cambrian in age and consists of igneous 

rocks, some of which have been metamorphosed, and metasedimentary rocks. 

The metasedimentary rocks constitute the Idaho Springs formation and are 

biotite-quartz gneiss, sillimanitic biotite-q\iartz gneiss, amphibolite, and lime 

silicate gneiss. These older rocks have been invaded by quartz diorite and associated hornblendite, granite gneiss and pegmatite (which locally forms a migmatite 

with units of the Idaho Springs formation), granodiorite, biotite-muscovite 

granite, and granite pegmatite. During Tertiary time the pre-Cambrian rocks 

were invaded by dikes and plugs of quartz monzonite porphyry, alaskite porphyry, 

syenitic bostonite porphyry, and quartz bostonite. Solifluctional debris of 

Wisconsin age forms sheets in some of the high basins and fills narrow valleys; 

similar debris forms avalanche ridges in certain of the narrow valleys. Recent 

alluvium covers the valley floor of the major stream.

Two periods of pre-Cambrian folding can be recognized in the district. The 

older folding crumpled the metasedimentary rocks into a series of upright and 

overturned north-northeastward-plunging anticlines and synclines. Granodiorite, quartz diorite and associated hornblendite, and granite gneiss and pegmatite 

were metamorphosed during this period of folding. The second period of folding 

appears to have been less intense and resulted in a series of warps trending northnorthwestward across the older folds. The biotite-muscovite granite, which is 

the youngest major pre-Cambrian rock unit, was intruded late in the period of 

north-northeastward folding and before the period of north-northwestward 

folding.

Arching of the Front Range highland during Laramide time is believed responsible for the formation of a regional joint pattern. During Tertiary time the 

bedrock was intruded by porphyritic dike rocks. A regional shear stress caused 

fractures in the bedrock that were the loci of deposition of hydrothermal veins 

subsequent to the intrusion of the porphyries.

The fractures formed under the regional shear stress are long, cymoid-shaped 

fissures composed of three elements that can be dated in a sequence. The first 

set of fractures formed approximately parallel to north-northeastward-trending

33
34 GEOLOGY AND OEE DEPOSITS, COLORADO

axial planes of major pre-Cambrian folds; those fractures now form the middle 

segment of the cymoid fissures. Subsequent fractures formed at both ends of 

the early fractures, one set with east-northeasterly trends and the final set with 

easterly trends.

The veins in the district are typical mesothermal fissure fillings. The veins are 

lodes that have smooth bounding walls and abundant slickensides; the fissures 

are fairly regular in strike and dip, and irregularities, where present, commonly 

provided favorable structures for the deposition of the ore minerals.

Two principal types of ore, pyrite-gold and galena-sphalerite, have been mined 

in the district. A third type, composite ore, is found where galena-sphalerite 

ore locally overlaps pyrite-gold ore. Mineralization took place in two stages 

during the period of fracturing; the veins were deposited in open space and show 

a well-defined zoning individual veins have a central segment of pyrite-gold 

ore bounded at both extremities by galena-sphalerite ore. In the first stage of 

mineralization quartz and auriferous pyrite with some chalcopyrite and tetrahedrite filled the early fractures, chiefly the north-northeasterly set and adjacent 

parts of the east-northeasterly set. In the second stage galena and sphalerite 

with minor amounts of quartz, pyrite, chalcopyrite, tetrahedrite, and carbonate 

filled the younger fractures near the ends of the cymoids. Veins formed during 

the second stage of mineralization locally cut the earlier veins in the east-northeastward-trending segments of the fissures, forming composite veins.

Structural control of ore shoots in mines of the district is generally well defined. 

Vein intersections and deflections in dip of veins have formed openings favorable 

for the deposition of ore; locally deflections in strike of veins appear to have formed 

openings; and one example of an ore shoot controlled by deflection of a fault upon 

entering a rock unit of different competency occurs in the district. These controls, or combinations of them, can be found on all three elements of the long, 

cymoid-shaped fissures.

Every accessible mine in the district was examined for radioactivity, and the 

dumps of inaccessible mines were traversed with a scintillation counter. Secondary uranium minerals torbernite, autunite, and dumontite(?) occur in vugs or 

fractures or in gouge, along several veins. Hydrous iron oxides from veins and 

from recent deposits on mine walls commonly show an unusual amount of radioactivity. In most of the radioactive material sampled, however, no discrete 

uranium minerals could be identified. It is tentatively concluded that large areas 

containing only pyrite-gold veins are poor in uranium and that areas of pyritegold or galena-sphalerite veins containing chalcopyrite are more favorable localities in which to look for uranium deposits.

INTRODUCTION AND ACKNOWLEDGMENTS

The Freeland-Lamartine mining district, in Clear Creek County, 

Colo., about 3 miles due west of Idaho Springs (figs. 3 and 4), forms a 

part of the Front Range mineral belt, a northeastward-trending belt 

of coextensive Tertiary veins and porphyry intrusives (Levering and 

Goddard, 1950, p. 72-73, pi. 2, and fig. 21). The district occupies 

about 4 square miles and includes the abandoned mining towns of 

Freeland and Lamartine.

Gold, silver, copper, lead, and zinc ores worth at least $18 million 

have been produced in the district from mesothermal veins of Tertiary
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 35

age. These veins occupy fractures that cut metamorphic and igneous 

rocks of pre-Cambrian age and porphyritic intrusive rocks of Tertiary 

age.

After Levering and Goddard, 1950

FIGUHE 3. Index map of Colorado showing the location of the Freeland-Lamartine district with reference 

to the Front Range highland and the Front Range mineral belt.

FIGUHE4. Index map showing the location of the Freeland-Lamartine district, Clear Creek County, Colo.
36 GEOLOGY AND ORE DEPOSITS, COLORADO

The first study of the geology of the district was made by Spurr, 

Garrey, and Ball (1908) as part of their investigation of the Georgetown quadrangle. Brief summaries abstracted from this report are 

given by Vanderwilt (1947, p. 63), Goddard (1947, p. 308-313), and 

Lovering and Goddard (1950, p. 191-193). The original mapping of 

the district was on a scale of 1:62,500.

During the period May-October 1952, the district was mapped by 

the U. S. Geological Survey on behalf of the Division of Kaw Materials of the U. S. Atomic Energy Commission. The topographic 

base map (on a scale of 1:6,000 with a contour interval of 20 feet) 

was made by the Geological Survey from aerial photographs taken in 

1951. In general, the part of the district mapped by Wells was 

mapped in detail equivalent to a scale of 1:24,000, and the remainder 

of the district was mapped in greater detail on a scale of 1:6,000. 

In addition, 16,000 feet of accessible mine workings were mapped on 

scales of 1:600 or 1:240. The area mapped by each author is shown 

in plate 2.

This report represents a part of the Survey's studies in the Idaho 

Springs-Central City area of the Front Kange.

The writers wish to thank C. L. Harrington, U. S. Mineral Surveyor, 

Idaho Springs, Colo., for the use of many maps of inaccessible mines. 

Much of the production data since 1906 was obtained from files of the 

U. S. Bureau of Mines. Thanks are due A. J. Martin of the U. S. 

Bureau of Mines for his assistance in providing the data. The 

Montana Mining Development Corp. loaned maps and assisted the 

writers in their examination of the Lamartine mine and mill. Thanks 

are also due the local miners who aided in the identification of abandoned mines and who provided information on the workings and 

location of ore in inaccessible mines.

HISTORY

About April 1, 1859, pay gold ore was discovered hi a placer near 

the mouth of Chicago Creek (Spurr, Garrey, and Ball, 1908, p. 311). 

Soon after this initial discovery a search for gold veins spread into the 

area along Trail Creek. The Freeland vein was discovered hi 1861, 

the Lamartine vein in 1867, and the Great Western vein in 1878. By 

1952 at least $18 million worth of gold, silver, copper, zinc, and lead 

had been produced from these and several smaller veins. Since about 

1910, mining in the district has been intermittent and generally on 

the decline. During 1952, 1 mine was operated for 6 months; 3 

mines were worked on a small scale; and only 1 mine was operated 

throughout the year. Most of the mines in the district are now 

partly or completely inaccessible.
FREELANDHLAMARTESTE DISTRICT, CLEAR CREEK COUNTY 37

GENERAL GEOLOGY

The general geology of the Freeland-Lamartine district has been 

described by Ball (Spurr, Garrey, and Ball, 1908) and by Lovering 

and Goddard (1950, pi. 2). The mapped area (pi. 2) consists predominantly of igneous rocks, some of which have been metamorphosed, 

and complexly folded metasedimentary rocks of pre-Cambrian age. 

Dikes and plugs of bostonite and monzonite have been intruded into 

the pre-Cambrian complex during Tertiary time. Gold-silver-leadzinc-uranium-bearing fissure veins occur in the same fracture systems 

as the dikes but are slightly younger. Quaternary debris sheets and 

avalanche ridges cover some of the high basins and narrow valleys. 

Kecent alluvium fills the valley flat of Trail Creek.

PRE-CAMBRIAN ROCKS

Ball (Spurr, Garrey, and Ball, 1908, pi. 2) and Lovering and 

Goddard (1950, pi. 2) indicate that most of the bedrock in the Freeland-Lamartine district belongs to the Idaho Springs formation. This 

formation was named by Ball (1906, p. 374) who considered it to be 

metamorphosed sediments. The Idaho Springs formation includes 

several lithologic types that are distinct and large enough to be 

mapped on a scale of 1:6,000 (pi. 2). In this report the rock types in 

the Idaho Springs formation that the writers have distinguished will 

be referred to by lithologic name. The approximate equivalents 

between the units in the Idaho Springs formation mentioned by Ball 

and those mapped by the writers are shown below.

Ball (1908) Harrison and Wells 

Biotite schist__________________ Biotite-quartz gneiss.

Biotite-sillimanite schist..__________ Sillimanitic biotite-quartz gneiss.

Quartz gneiss ______________ Sparse in the Freeland-Lamartine district *,

included with lime silicate gneiss. 

Lime silicate member _____ _____ _ Lime silicate gneiss. Amphibolite.

In addition, the writers mapped migmatite as a rock unit. Th® 

term "migmatite" is used by the writers to denote a rock unit that 

contains a finely interlayered mixture of two types of rock-forming 

material commonly a mixture of one of the biotite-fich gneisses and 

granite. The migmatite is equivalent to the "injection gneiss" of 

Ball and is partly of metasedimentary origin. Therefore, the migmatite of this report belongs, in part, to the Idaho Springs formation 

of BaU.

The rocks in the Idaho Springs formation are the oldest in the 

district. During pre-Cambrian time they were invaded by quartz 

diorite and associated hornblendite, granite gneiss and pegmatite, 

granodiorite, and finally by biotite-muscovite granite and pegmatite,
38 GEOLOGY AND ORE DEPOSITS, COLORADO

The complex resulting from these successive emplacements of younger 

rocks has been described by Ball (1906, p. 372) as follows 

Some idea of the complexity of injection may be gained from the fact that in a 

distance of one mile, on the ridge between Silver Creek and Clear Creek, six 

formations alternate seventy-six times, or at the rate of one alternation to 70 feet. 

This is exclusive of a number of minor injections and inclusions.

IDAHO SPRINGS FORMATION

The rock units of the Idaho Springs formation are referred to in this 

report by lithologic name. These names have been selected on the 

basis of quantitative mineral content, presence of diagnostic minerals 

easily recognized in the field, and structure of the rock. An attempt 

has been made to choose mineral modifiers that most nearly describe 

the prominent features of the rock seen in the field. Thus, rather than 

name one of the units quartz-biotite-plagioclase-microcline gneiss 

using all of the principal minerals as modifiers, the writers have named 

this unit biotite-quartz gneiss because of its characteristic black color 

due to the biotite, and its characteristic hardness due to the high 

quartz content. In the garnet-bearing varieties of this rock, garnet is 

conspicuous, and garnetiferous has been added to the lithologic name 

at places in the text to denote that garnet is locally present in the rock 

unit (biotite-quartz gneiss).

Ball (1906) interpreted the Idaho Springs formation to be a series of 

metamorphosed sedimentary rocks that originally consisted of interlayered sandstones, shales, and calcareous sandstones although age 

relations among the various rock units are not known. He concluded 

that under regional metamorphism the sandstone yielded quartz 

gneiss, the shales yielded biotite schist and biotite-sillimanite schist, 

and the calcareous sandstones yielded the lime silicate rocks. In 

general, Ball's generalized interpretation is acceptable to the writers 

although it appears to need modification concerning parts of certain of 

the rock units that appear to have been changed by metasomatic 

processes and are not the simple result of thermodynamic metamorphism as he implied.

BIOTITE-QUARTZ GNEISS

Biotite-quartz gneiss is exposed at a few places in the district, and it 

can be seen best in the workings of the Little Johnie group of mines 

and on the ridge just south of the abandoned mining town of Freeland 

(pi. 2). The gneiss also occurs as layers and lenses, too small to be 

mapped, in sillimanitic biotite-quartz gneiss and granite gneiss and 

pegmatite. At many places the biotite-quartz gneiss is slightly 

migmatitic owing to scattered 1-inch-thick conformable layers of 

granitic material.
FREELAND-LAMAETINE DISTRICT, CLEAR CREEK COUNTY 39

The contacts between the biotite-quartz gneiss and the other rock 

units of the Idaho Springs formation are gradational.

The biotite-quartz gneiss is a black to mottled gray and black, fineto medium-grained gneiss that commonly is well foliated, except in 

local quartz-rich facies that appear fine grained and uniform.

The principal minerals in the gneiss are quartz, biotite, and plagioclase; varietal accessories include microcline, muscovite, magnetite, and 

garnet; many varieties containing garnet are fine grained and poorly 

foliated. All varieties of the biotite-quartz gneiss have a pronounced 

lineation, expressed by biotite alinement, and in some more f eldspathic 

facies by streaking or crenulations along biotite-rich planes in the 

rock. 

The structures of both the garnetiferous and nongarnetiferous varieties of the biotite-quartz gneiss are similar in thin section. The rock 

is foliated by segregation of the minerals into layers and through 

elongation of mineral grains and alinement of platy minerals. Layering is more prominent in the garnetiferous varieties and biotite alinement more common in the nongarnetiferous varieties.

The biotite-quartz gneiss ranges considerably in composition from 

outcrop to outcrop as shown by the modes (volume percent) given in 

table 1. In general, the gneiss contains from 20 to 40 percent biotite, 

from 30 to 60 percent quartz, and from 10 to 20 percent plagioclase. 

The garnetiferous variety commonly contains more magnetite and less 

feldspar than the nongarnetiferous variety.

Two samples of garnet were handpicked from specimens from 

widely separated localities of garnetiferous biotite-quartz gneiss.

TABLE 1. Modes (volume percent) of biotite-quartz gneiss

Quartz ______

2-5-78

4.0

- 39

- 39

- 19

2-6b-8

64.0

12

21

1.5

c

2-6a-56a

19 n

46

7

20

10

2

3

OS-5

22.0

49

21

8

Trace

BC-6

6.0

64

9

20

1

370-1

Q n

37

11

39

1

2

2-2a-172a

37.0

7

28

19

10

Trace

2-6b-47

45.0

14

30

11

1

358-1

39.0

9

22

30

.5

2-5-78: Feldspar-rich layer in siUimanitic biotite-quartz gneiss, 500 feet N. 15° W. from the portal of the 

New Era south tunnel.

2-6b-8: Biotite-quartz gneiss layer in migmatite from outcrop on the north side of the road where the 

Trail Creek road crosses Trail Creek near Freeland.

2-6a-56a: Biotite-quartz gneiss layer in migmatite from outcrop along road 800 feet east of the portal of 

the Old Stag tunnel.

OS- 5: Feldspar-rich facies of biotite-quartz gneiss from the Old Stag tunnel.

BC-6: Biotite-quartz gneiss from the Belle Creole tunnel.

370-1: Garnet-bearing biotite-quartz gneiss from the upper tunnel, Little Johnie group of mines.

2-2a-172a: Garnetiferous biotite-quartz gneiss from the upper tunnel, Little Johnie group of mines,

2-6b-47: Garnetiferous biotite-quartz gneiss from layer in granite gneiss and pegmatite 250 feet west of 

the portal of the Bell of the West tunnel.

358-1: Magnetite-rich garnetiferous biotite-quartz gneiss from the lower tunnel, Little Johnie group 

of mines.
40 GEOLOGY AND ORE DEPOSITS, COLORADO

Garnets from both samples had a refractive index of 1.811. The a0'a 

were determined by A. J. Gude 3d, U. S. Geol. Survey laboratory, 

Denver, Colo., to be 11.542 and 11.555 angstrom units. According 

to the data presented by Fleischer (1937) and Levin (1950), the garnet 

is probably almandite.

The biotite-quartz gneiss is mainly fine grained and granoblastic, 

though some of the garnetiferous varieties contain coarser pods of 

poikilitic garnet, magnetite, or quartz. Biotite flakes are alined along 

grain boundaries, and quartz grains are commonly elongate parallel 

to the biotite alinement. In the garnetiferous variety the quartz 

grams tend to have a more sutured boundary than in the nongarnetiferous -varieties. The cores of most of the garnet poikilitically 

enclose small grains of biotite, magnetite, and quartz. Although 

subrounded garnet crystals locally transect planes of biotite, many 

of the biotite flakes within the garnet are oriented parallel to the 

i)iotite laths outside of the garnet crystal. Magnetite in this rock 

type occurs with biotite (commonly as laths and wedges along cleavage planes) or in cores of garnet crystals. Magnetite in a thin section 

from an exceptionally magnetite-rich specimen of garnetiferous biotite-quartz gneiss (358-1) poikilitically encloses quartz, biotite, garnet, 

and apatite. The magnetite forms both patches that cut across contacts between garnet and quartz and small anhedral blebs oriented 

parallel to foliation along grain boundaries.

SnilMANITIC BIOTITE-QUARTZ GNEISS

The largest exposed body of sillimanitic biotite-quartz gneiss is on 

the north side of Trail Creek, in the north-central part of the mapped 

area (pi. 2). It also forms small, scattered lenses and layers in migmatite and granite gneiss and pegmatite throughout the district. 

Parts of the sillimanitic biotite-quartz gneiss contain as much as 30 

percent of 1-inch thick conformable granitic layers. At the eastern 

edge of the district, on the north side of Trail Creek, small layers of 

sillimanitic biotite-quartz gneiss occur on minor fold crests and troughs 

as inclusions in granite gneiss and pegmatite.

The sillimanitic biotite-quartz gneiss is mottled black and gray, 

medium grained, and has a conspicuous gneissic structure. The 

principal minerals are biotite and quartz; varietal accessories include 

sillimanite, microcline, plagioclase, and muscovite; the minor accessories are magnetite, sphene, and hematite. The foliation is produced 

by segregation of the minerals into mica-sillimanite layers and quartzrich layers, and the lineation is given by the biotite and sillimanite. 

Modes of this gneiss are shown in table 2. The presence of sillimanite 

in amounts greater than 5 percent serves to distinguish this gneiss 

from other members of the Idaho Springs formation.
FREELAND-LAMARTESTE DISTRICT, CLEAR CREEK COUNTY 41

Examination of this gneiss in thin section shows that it contains 

elongate, subrectangular crystals of quartz that form, a layered network. Biotite and sillimanite form bands parallel to the layering 

in the quartz network. Biotite occurs in fine- to medium-grained 

crystals, some of which fill tiny fractures in some of the quartz crystals. 

Sillimanite is in short, subhedral to euhedral crystals and appears to 

embay both biotite and quartz. The microcline, plagioclase, and 

sphene grains are distributed through the rock. Muscovite is associated with biotite in the biotite-rich layers. Magnetite occurs 

chiefly along cleavages and grain boundaries of the micas. Hematite 

is in flakes and dust coating or surrounding magnetite.

TABLE 2. Modes (volume percent} of sillimanitic biotite-quartz gneiss

Sillimanite __ ..

Biotite . . _ _ 

Sphene .. . --- ... . .. ... .. .. ...

2-5-41C

2

44

10

5

25

15

Trace

2-5-85

51

Trace

12

30

6

1

Trace

OS-11

16

49

3

6

22

5

2-5-41c: Sillimanitic biotite-quartz gneiss layer in migmatite from outcrop along road 75 feet east of the 

portal of the New Era north tunnel.

2-5-85: Sillimanitic biotite-quartz gneiss from outcrop along road 900 feet west of the portal of the New 

Era north tunnel.

OS-11: Sillimanitic biotite-quartz gneiss from the Old Stag tunnel.

AMPHIBOUTE

Exposures of amphibolite are sparse but are most common in the 

east-central part of the district. The amphibolite occurs as conformable layers and lenses intercalated with, and gradational into, other 

rock types of the Idaho Springs formation and the granite gneiss and 

pegmatite.

The amphibolite is a black to greenish-black fine- to mediumgrained gneiss consisting principally of hornblende, andesine-labradorite, and quartz; it is distinguished with difficulty from metamorphosed quartz diorite. (See page 47.) Locally, the amphibolite 

contains layers of pyroxene gneiss. Modes of the amphibolite and 

related rocks are shown in table 3.

Marked by the segregation of the minerals into light and dark 

layers, foliation is well shown in the amphibolite; lineation is produced by the alinement of hornblende crystals.

The amphibolite has a fine- to medium-grained granular texture. 

The hornblende crystals are commonly about 2 millimeters long and 

are in a matrix of fine- to medium-grained equigranular quartz and 

plagioclase. Most of the plagioclase grains are twinned. The twins 

are predominantly albite and pericline (or acline) or, less commonly,
42 GEOLOGY AND ORE DEPOSITS, COLORADO

combinations of the two types. In 3 thin sections, only 1 carlsbadalbite-pericline, and 2 carlsbad-albite twin combinations were noted.

TABLE 3. Modes (volume percent) of amphibolite and related rocks

2-5-8a

55

25

16

1

3

2-5-Sb

58

Trace

25

11

3

2

2-5-Sc

9

34

37

11

8

<j

2-5-8: Suite of specimens from outcrop of amphibolite containing pyroxene gneiss layers on the north side 

of the road at Freeland. 

a, Amphibolite.

b, Amphibolite 1 inch from contact with 6-inch pyroxene gneiss layer. 

c, Pyroxene gneiss layer in amphibolite.

LIME SILICATE GNEISS

Lime silicate gneiss is sparse in the Freeland-Lamartine district; 

the best exposure of this rock is on the north side of Trail Creek, about 

700 feet west of the collar of the New Era shaft. At this exposure, 

the rock is intimately folded with other members of the Idaho Springs 

formation and granite gneiss and pegmatite. A thin layer of quartzmagnetite gneiss (quartzite?) is exposed along parts of the south edge 

of this outcrop and has been included with the lime silicate gneiss 

on the map (pi. 2).

The lime silicate rocks were considered by Ball (1906) to be a 

member of the Idaho Springs formation. In a later report (Spurr, 

Garrey, and Ball, 1908, p. 41-44) he included within this member four 

rock types which he called quartz-magnetite gneiss, hornblendediopside gneiss, quartz-epidote-garnet rock, and calcite-lime silicate 

rock.

The writers include varieties of Ball's quartz-epidote-garnet 

rock and calcite-lime silicate rocks in the rock group mapped as lime 

silicate gneiss. Skarns and skarnlike rocks that may have formed 

from calcium-rich rock layers of the Idaho Springs formation by 

metasomatism rather than simple thermodynamo metamorphism are 

also included in the lime silicate gneiss. The quartz-magnetite gneiss 

occurs only in small, unmappable layers in the district; a variety of 

the hornblende-diopside gneiss has been mapped by the writers as 

amphibolite.

In the Freeland-Lamartine district the lime silicate gneiss is a 

bright-green to greenish-black fine- to coarse-grained massive to 

layered rock. Epidote or intergrowths of epidote and clinozoisite 

commonly are the major constituents of the massive varieties, and
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 43

hornblende, feldspar, and clinopyroxene are more common in the 

layered varieties. The layers range in thickness from fractions of an 

inch to as much as a foot and are due to segregation of the minerals 

into light and dark layers. The layers of many of the hornblendic 

rocks are crosscut by irregular patches and pods of quartz and epidote 

as much as 2 feet in diameter. The layered rocks are commonly cut 

by microscopic to 1-inch-thick stringers of epidote-microcline-hornblende.

The composition of the rocks mapped as lime silicate gneiss varies 

from layer to layer within one outcrop. Generally the rock contains 

hornblende, epidote, and quartz in varying proportions that make up 

about 50 percent of the rock by volume. The remainder of the rock 

consists largely of clinopyroxene or clinozoisite, and plagioclase 

(andesine to bytownite), also in varying proportions. Sphene is 

commonly present in amounts of from 1 to 4 percent; and magnetite 

and apatite are accessory minerals in most of these rocks.

Examination of these rocks in thin section indicates that if epidote 

and clinozoisite are both present in the gneiss they tend to form large 

(as much as one-half inch in diameter) compound porphyroblasts 

consisting of irregular intergrowths of diversely oriented crystals of 

the two minerals. Hornblende commonly is in short, stubby crystals 

about 2 millimeters long although at places in this rock hornblende 

crystals as much as 1 inch across and 3 inches long are present.

ORIGIN

The gradation between the rock units in the Idaho Springs formation and the interlayering and interlensing of the units suggests to 

the writers that the Idaho Springs formation represents metamorphosed sedimentary rocks. The broad regional distribution of rocks 

of similar character has been pointed out by Ball (Spurr, Garrey, and 

Ball, 1908), Bastin (Bastin and Hill, 1917), and Lovering and Goddard 

(1950). Probably the rocks of the Idaho Springs formation were 

formed by regional metamorphism of sedimentary rocks, and the 

mineralogic variations in the rocks are principally the result of differences in original mineral composition of the sediments that appear to 

have been under pressure and temperature conditions necessary for 

the formation of the amphibolite facies. 1 In a broad sense, this is 

probably true, but certain local differences in the rock units suggest 

to the writers that the metamorphic rocks derived from regional 

metamorphism have been modified, at least in part, by metasomatism.

The biotite-quartz gneiss contains a mineral assemblage that could

1 In the Freeland-Lamartine district all of the rock units of the Idaho Springs formation approximate the 

same grade of metamorphism. The mineral assemblages are those described by Turner (1948, p. 76-88) 

for various subfacies of the amphibolite facies. The term "amphibolite facies" is used here to describe 

mineral assemblages that are compatible throughout the region.

370788 56 2
44 GEOLOGY AND ORE DEPOSITS, COLORADO

be derived from original sandy beds. A slight decrease in the amount 

of potash in the original sediment would favor the formation of garnet 

instead of microcline, and the garnetiferous biotite-quartz gneiss may, 

therefore, represent a facies of the biotite-quartz gneiss. The close 

field association between the garnet-bearing rock and the biotitequartz gneiss the former everywhere forms lenses or layers in the 

latter supports the belief that the two types of rocks are genetically 

related. A metasomatic modification of parts of these two varieties 

of biotite-quartz gneiss is indicated by field and laboratory observations. In the Little Johnie group of mines several 1- to 2-inch-thick 

granitic stringers were seen crosscutting biotite-quartz gneiss and 

a %- to 1-inch-thick band of garnet was noted in the biotite-quartz 

gneiss adjacent to and following the irregular contacts between the 

granitic stringer and the gneiss. As the layer of biotite-quartz gneiss 

was not garnetiferous except for the thin band along the granitic 

stringer, the writers infer that the garnet formed by metasomatic 

processes. Examination of the magnetite-rich varieties of the biotitequartz gneiss showed irregular patches of magnetite that crosscut 

grain boundaries and poikilitically enclose corroded mineral grains. 

The uncommon concentration of magnetite, its textural distribution, 

and its lateness hi the paragenetic sequence of the gneiss suggest to 

the writers that much of the magnetite in the magnetite-rich varieties 

has been introduced into the rock.

The sillimanitic biotite-quartz gneiss contains a mineral assemblage 

that could have been derived from original alumina-rich sediments. 

The interlayering and interlensing of this rock type with other rocks 

of the Idaho Springs formation along flanks of open folds suggests 

that much of this gneiss was derived from sediments that originally 

contained alternating sandy and shaly beds.

A metasomatic origin for part of this rock unit is, however, entirely 

plausible. It is particularly significant that in the migmatitic parts 

of the sillimanitic biotite-quartz gneiss the amount of sillimanite 

present seems to be proportional to the amount of granite in the rock. 

Thus, even if the more sillimanitic gneiss were more subject to migmatization, the proportionality of thickness of sillimanite layers to 

thickness of granite stringers is suggestive of local change in the 

original bulk chemical composition of the gneiss.

The amphibolite and lime silicate gneiss are calcium-rich layers and 

lenses intercalated with the other rocks of the Idaho Springs formation. 

These calcium-rich rocks may represent limy sandstones or impure 

limestones in an original sedimentary sequence. Some local metasomatic modification of these rocks is indicated in most outcrops by 

crosscutting stringers, pods, and patches of quartz-epidote rock. 

Where these patches are in amphibolite, they represent a considerable
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 45

loss of iron from the rock. Metasomatism of calcareous rocks by 

granitic solutions to produce skarns and skarnlike assemblages of 

minerals is too common to be overlooked as a possible origin for some 

of the lime silicate gneiss.

QUARTZ DIORTTE AND ASSOCIATED HOBNBLENDITB

Quartz diorite and associated hornblendite form sparsely scattered, 

small, rounded plugs (?) and short, conformable and disconformable, 

dikelike bodies in the older pre-Cambrian rocks. As the contacts 

between this rock unit and other rocks of the district are poorly 

exposed, no definite age relations can be established from this study. 

However, Ball (Spurr, Garrey, and Ball, 1908, p. 56-57) found that at 

certain localities these rocks appear to be younger than what he 

mapped as quartz monzonite and at other localities appear to be 

older. The quartz diorite clearly intrudes metasedimentary rocks of 

the Idaho Springs formation and is definitely intruded by Silver Plume 

granite (Spurr, Garrey, and Ball, 1908, p. 37-60).

Although some of the quartz diorite and associated hornblendite 

in the district is massive, most of these rocks contain a foliation caused 

by a faint to prominent mineral layering in the rock. In general, the 

smaller bodies as well as the margins of the larger bodies of this rock 

type contain a foliation, and the central parts of the larger bodies are 

massive. The layering in the foliated rocks is concordant with the 

foliation in the adjacent pre-Cambrian rocks regardless of whether 

the gross outline of the body is concordant or crosscutting. Certain 

of the foliated facies cannot be distinguished in the field from amphibolite of the Idaho Springs formation; certain facies resemble granodiorite but can be distinguished by the abundance of hornblende which 

is sparse in granodiorite.

The quartz diorite is a black to mottled black and white fine- to 

coarse-grained hypidiomorphic granular rock consisting principally of 

hornblende, andesine-labradorite, and quartz. Varietal accessories 

in the rock are pyroxene and biotite; and minor accessories include 

apatite, magnetite, epidote, and sphene. At places the rock is a 

hornblende-biotite-quartz diorite (tonalite); and at other places it is a 

diorite. (See table 4.)

The layering in the foliated facies of the quartz diorite is due to 

segregation of the minerals into mafic-rich and quartz-plagioclaserich layers. The formation of this layering appears related to the 

mineral composition of the rock. An increasing degree of gneissic 

structure as shown by more continuity and regularity of the layering 

is accompanied by an increase in the amount of plagioclase and biotite 

and a decrease in the amount of hornblende. (See table 4, specimens 

2-5-4la, 2-6b-52, 2-5-49b, and 2-5-49c.) This same change is
46 GEOLOGY AND ORE DEPOSITS, COLORADO

TABLE 4. Modes (volume percent) of quartz diorite and associated hornblendite

Biotite 

I-16b

27

11

38

8

14

Trace

Trace

Trace

1

2-5-49a

95

1

1

3

l-2-24a

82

7

8

Trace

2-10-31

69

3

16

5

6

Trace

1-2-11

36

25

16

22

.4

1

2-5-41a

65

30

4

.6

Trace

.3

2-6b-52

53

36

7

2

2

2-5-49b

56

39

.7

3

.6

.3

2-5-49C

31

50

3

13

1

2-

1-16b: Quartz diorite from the Jo Reynolds area, about 1 mile northwest of the district.

2-5-49a: Hornblendite from the sill on the north side of the road 300 feet east of the portal of the New Era 

mine.

1-2-24a: Weakly foliated hornblendite (?) from the top of the ridge 600 feet east of the collar of the Silver 

Queen shaft.

2-10-31: Weakly foliated hornblendite(?) from an outcrop along the road 500 feet east of the point where 

Trail Creek road crosses the head of Trail Creek.

1-2-11: Moderately foliated hornblendite (?) from a dikelike body on the ridge to the north of the head of 

Trail Creek.

2-5-41a: Weakly foliated quartz diorite from the sill on the north side of the road 300 feet east of the portal 

of the New Era mine.

2-6b-52: Weakly foliated quartz diorite from the Bell of the West mine.

2-5-49b: Moderately foliated quartz diorite from the sill on the north side of the road 300 feet east of theportal i.f the New Era mine.

2-5-49c: Moderately to strongly foliated quartz diorite from the same locality as 2-5-49b.

reflected in thin section by a textural change trending from hypidiomorphic granular in the massive facies to allotriomorphic granular in 

the better foliated facies. This textural change is partly due to the 

increasing proportion of biotite flakes, parallel to the layering, that 

cut through former euhedral hornblende or plagioclase crystals. The 

plagioclase in the massive quartz diorite is subhedral and twinned. 

Most of the plagioclase has combination twins of albite-pericline (or 

acline), carlsbad-albite, carlsbad-pericline, or more complex and rarer 

varieties. Although the plagioclase in the foliated facies has the same 

compound and complex twinning characteristic of the massive facies,, 

anhedral crystals of altered plagioclase embaying all the other minerals 

except biotite are characteristic of the quartz-plagioclase-rich layers. 

The massive hornblendite is a black to greenish-black fine- to 

medium-grained rock composed essentially of hornblende. Accessory 

minerals in this rock include magnetite, apatite, and quartz. The 

foliated facies of the hornblendite is mottled black or greenish black 

and white and consists essentially of hornblende, andesine-labradorite, 

and quartz. Biotite is a subordinate mineral found in this facies, and 

magnetite, epidote, and sphene occur as accessory minerals. The 

massive hornblendite and the dark parts of the foliated hornblendite 

consist of hypidiomorphic granular hornblende with minor amounts of 

quartz. The white areas in the foliated hornblendite are patches or 

irregular stringers of altered andesine-labradorite containing fragments 

of irregular-shaped hornblende and biotite and rounded blebs of quartz. 

The small amount of unaltered plagioclase has simple albite twinning,, 

or, uncommonly, an albite-pericline combination twinning.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 47

In general, the same trend toward decrease in hornblende and increase 

in plagioclase and biotite is shown from the massive to foliated hornblendite as is shown from massive to foliated quartz diorite (table 4).

DISTINCTIONS BETWEEN AMPHIBOUTE, QUARTZ DIORITE, AND HORNBLENDITE

Certain of the better foliated facies of quartz diorite and associated 

hornblendite are difficult or impossible to distinguish in the field from 

amphibolite of the Idaho Springs formation. A laboratory study of 

these two groups of amphibolitic rocks was undertaken because 

Turner (1951) had suggested that the genesis of some amphibolitic 

rocks can be deduced from the amount and complexity of the twinning 

in the plagioclase. The results of the writers' study are shown in 

table 5. The amphibolite indicated in this table represents a group 

of layered rocks gradational into rocks of the Idaho Springs formation; 

the hornblendite is included only to place emphasis on its lack of 

plagioclase; the quartz diorite is from a body containing pigeonite 

along pyroxene cleavages (specimen I-16b, table 4); and the discordant and concordant bodies represent rocks considered to be 

quartz diorite and hornblendite which have been grouped by field 

occurrence.

The difference between the type and amount of twinning in the 

plagioclase of the amphibolite and the better foliated facies of quartz 

diorite and associated hornblendite is that the latter have a greater 

variety of plagioclase twinning and the twins tend to occur in 

combinations.

TABLE 5. Amount and type of twinning in plagioclase feldspars in amphibolitic

rocks 

[Varieties: Ab, Albite; Pe, Pericline; Ca, Carlsbad. Occurrence: X, present; C, common; O, occasional;

R, rare]

Hornblendite (no plagioclase). 

Quartz diorite __ 

Discordant bodies 

(massive to weakly 

foliated). 

Concordant bodies 

(massive to weakly 

foliated). 

Discordant bodies 

(moderately to 

strongly foliated). 

Concordant bodies 

(moderately to 

strongly foliated).

Amount and type

Untwinned grains

A few ...

None .... 

 do.....

...do.....

 do.....

...do.....

Mostly 

simple twinning

X

 _- 

X

Mostly 

combination 

twinning

X

X 

X

Varieties

Ab

C

--_._

0

R 

O

Pe

C

R 

C

.....

Ab-Pe

C 

R

C 

C

Ca-Ab

R

C

C 

C

Ca-Pe

O

Ca-AbPe

R

O

C

Other! 

complex

C

C 

0
48 GEOLOGY AND OEE DEPOSITS, COLORADO

ORIGIN

Turner (1951, p. 585) stated that the plagioclase of schists and 

hornfels differs from the plagioclase of undoubtedly igneous rocks 

by the prevalence of simple twins and the lack of variety of types 

(mostly either simple albite or pericline, or both, carlsbad rare, complex combinations even rarer, albite-pericline combinations in one 

crystal are infrequent). He also noted (p. 583) 

In amphibolites of igneous origin, coarse plagioclase (in some cases retaining 

relict idiomorphic outlines) is liable to show twinning just as complex as that of 

igneous plagioclase albite-Carlsbad-pericline combinations especially.

This argument, when taken in conjunction with the data in table 5 r 

suggests that the plagioclase of the better foliated facies of quartz, 

diorite and associated hornblendite is of igneous origin and that the 

plagioclase of both the weakly foliated facies and the amphibolit& 

is of metamorphic origin.

The foliation in the quartz diorite and associated hornblenditeresults from the plagioclase layers, stringers, and patches. The 

orientation of the foliation is the same as the orientation of the foliationin the enclosing rocks whether the major outlines of the body ar& 

concordant or discordant. This fact, in conjunction with the textural 

change from hypidiomorphic to allotriomorphic and the mineralogic 

trend from hornblende to plagioclase in going from the massive to 

foliated facies, suggests to the writers that the foliation in the rock 

is not due to flow structure but is due to shearing and recrystallization 

of the rock. If the foliation is due to metamorphism, then some of 

the plagioclase in these rocks is of metamorphic origin. Because 

the hornblendite originally had no plagioclase (or only accessory 

amounts), any plagioclase found in these rocks now would have the 

characteristics of metamorphic plagioclase.

The writers tentatively conclude from the limited data available 

that the quartz diorite and associated hornblendite are basic intrusive 

rocks that have been metamorphosed to varying degrees principally 

by shearing and recrystallization. The writers infer that the bodies 

of hornblendite were more resistant to shearing than equal sized bodies 

of the quartz diorite and that the hornblendite is, therefore, more 

likely to occur as a massive or faintly foliated rock.

One further possibility should be mentioned. The rocks mapped 

as quartz diorite and associated hornblendite, and the metamorphosed 

facies of each, may not all be of the same age. The apparent difference in amount of shearing and recrystallization of the massive varieties may be due to posttectonic intrusion. The better foliated, 

concordant varieties may have been intruded into the Idaho Springs 

formation before or during the principal period of pre-Cambrian 

folding.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 49 

MIGMATITE

Definition. Migmatite as used in this report refers to a rock 

consisting of intimate mixtures of metasedimentary rocks and granitic 

rocks. All degrees of migmatization occur in the Freeland-Lamartine 

area. An arbitrary classification was used in the field in mapping 

migmatite of the Idaho Springs formation and granite. This classification was based on two considerations first, the structure of the 

interlayering, and second, the amount of granitic material present in 

the rock. To be classified as migmatite, a rock had to be finely interlayered somewhat in the manner of rocks that have been called 

"injection gneisses," and the rock had to contain at least 30 but not 

more than 70 percent of granitic material. If the rock contained less 

than 30 percent granitic material, it was mapped as the appropriate 

unit of the Idaho Springs formation; if the rock contained over 70 

percent of granitic material, it was mapped as the appropriate granite 

(usually granite gneiss and pegmatite).

Description. Migmatite is well exposed at several places in the 

district, particularly on the north side of Trail Creek near the eastern 

edge of the mapped area (pi. 2). Good exposures of this rock type 

also can be seen underground in the workings of the New Era mine 

and in the crosscut part of the Old Stag tunnel.

Although most migmatite in the district is a mixed rock consisting 

principally of quartz-biotite gneiss and generally conformable discontinuous 1-inch-wide layers and pods of granitic'material along foliation 

planes in the gneiss, migmatite is locally composed of sillimanitic 

biotite-quartz gneiss and intercalated granitic layers, and at a few 

places it consists of garnetiferous biotite-quartz gneiss and granitic 

material.

Contacts between the migmatite and biotite-muscovite granite are 

fairly sharp, and at most places usually little or no migmatite occurs 

at contacts between biotite-muscovite granite and units of the Idaho 

Springs formation. However, contacts between the migmatite and 

the granite gneiss and pegmatite are gradational, commonly over 

several tens of feet. The proportion of granitic material in the migmatite gradually increases toward the granite gneiss and pegmatite 

and approximate contacts have been drawn where granitic material 

exceeds 70 percent of the rock. Likewise, contacts between the 

migmatite and biotite-quartz gneiss or sillimanitic biotite-quartz 

gneiss are also completely gradational, and the contacts drawn are 

approximate. As mapped most migmatite occurs in a broad zone 

separating large bodies of sillimanitic biotite-quartz gneiss from 

granite gneiss and pegmatite. Smaller bodies of metasedimentary 

rocks and granite gneiss and pegmatite may be interlayered, and the 

transition zone of migmatite is commonly too small to map even
50 GEOLOGY AND ORE DEPOSITS, COLORADO

though it is present. The interlayering of the granite gneiss and 

pegmatite, migmatite, and biotite-quartz gneiss is shown in the 

geologic section (pi. 2).

Origin. The origin of a mixed rock unit obviously involves the 

origin of its component parts. As has been previously stated, the 

metamorphic rocks of the Idaho Springs formation are believed to 

be principally metamorphosed sedimentary rocks. The origin of the 

granitic component of the migmatite and the manner of its emplacement in the metasedimentary component involve the origin of biotitemuscovite granite and the granite gneiss and pegmatite. The writers 

interpretation of field and laboratory data suggests that the biotitemuscovite granite is of magmatic origin and thus that the part of the 

migmatite containing biotite-muscovite granite could be called injection gneiss or attributed to assimilation affects. The data gathered 

on the granite gneiss and pegmatite are not conclusive as to whether 

this body is of metamorphic, metasomatic, or magmatic origin. The 

migmatite containing granite gneiss and pegmatite may have formed 

by metamorphic differentiation, metasomatism, or injection.

GRANITE GNEISS AND PEGMATITE

About 50 percent of the mapped area (pi. 2) contains scattered 

outcrops of granite gneiss and pegmatite. Some of the best exposures 

of this rock type are along the west side of the small valley extending 

southerly from Freeland. Other good exposures are on the north 

side of Trail Creek, near the eastern edge of the district.

All surface and underground exposures of contacts between granite 

gneiss and pegmatite and rocks of the Idaho Springs formation show 

that this unit is conformable. The contacts are gradational, commonly over zones that are several tens of feet wide, and the rock unit 

mapped as migmatite appears to represent this gradation between 

the gneiss and rocks of the Idaho Springs formation, principally 

biotite-quartz gneiss.

The granite gneiss and pegmatite unit ranges greatly in composition and contains rocks that could be classified as alaskite, granite, 

quartz monzonite, and granodiorite. The range in composition of 

the unit is indicated by figure 5A and by the approximate modes 

shown in table 6. The rock consists principally of quartz, microcline, and plagioclase (oligoclase-andesine) with some biotite and 

muscovite. The common accessory minerals are magnetite and 

sphene, but sillimanite, garnet, epidote, and zircon are present locally. 

Some of the alaskitic gneiss contains magnetite as the only ironbearing mineral.

The granite gneiss and pegmatite is a pink to white medium- to 

coarse-grained and pegmatitic rock. Pegmatite forms irregular
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 51

Granite gneiss and pegmatite 

(Q=quartz, K=microcline, P=plagioc)ase)

A

Biotite-muscovite granite 

(Q=quartz, K=microcline, P=plagioclase)

FIGVBE 5. Triangular diagrams showing variations in modal composition (volume percent) of granite 

gneiss and pegmatite and biotite-muscovite granite.

patches, lenses, and pods that are scattered through the rock and range 

in size from 1 inch to 500 feet in diameter. The alaskitic facies is 

commonly more pegmatitic than are the other facies, although all 

facies contain patches of pegmatite.

All but the alaskitic facies contain discontinuous streaks and wisps 

of mafic-rich materials and, commonly, 1 inch to 10 feet wide discontinuous layers, lenses, and pods of metadsedimentary rocks. Many 

of the inclusions in granite gneiss and pegmatite are highly contorted, 

and at some places only faint shreds of biotite strands in scroll-like 

patterns remain.

TABLE 6. Modes (volume percent) of granite gneiss and pegmatite

Microcline. . 

Plagioclase-. 

Quartz ...... 

Biotite 

Magnetite - - 

Sillimanite--

2-2a-154

19 

6 

58

5

.5 

2

2-5-13

54 

8 

32 

2

Trace 

Trace

Trace

2-5-49d

24 

29 

44 

2

1

Trace

TVnpp

2-6a-56b

9 

30 

44 

14

.3 

Trace

Trace

2-6a-109b

39 

15 

44

Trapp i

.4

2-6b-70

41 

6 

34

8

12

Trace

358-6

28 

42 

29 

2

Trace

370-3

40 

21 

38 

1

Trace

Trace

BC-8

33 

25 

33 

5

5

Trace

Trace

357-6

70 

1 

27

1

Trace

Trace

2-2a-154: Medium-grained thinly layered granite gneiss from granite gneiss and pegmatite layer in migmatite on top of hill 700 feet northeast of the collar of the Crazy Girl shaft.

2-5-13: 1-inch-thick alaskitic granite gneiss and pegmatite layer in migmatitic granite gneiss outcrop on 

north side of road at Freeland.

2-5-49d: Alaskitic granite gneiss and pegmatite granulite on north side of quartz diorite sill 300 feet east 

of the portal of the New Era mine.

2-6a-56b: Coarse-grained granite gneiss layer in migmatite along road 600 feet east of the portal of the 

Old Stag tunnel.

2-6a-109b: Cataclastically deformed alaskitic granite gneiss and pegmatite from prospect pit 700 feet 

southwest of the collar of the Brighton shaft.

2-6b-70: Cataclastically deformed granite gneiss and pegmatite from outcrop on the nose of the ridge 

800 feet southeast of the portal of the Teller tunnel.

358-6: Cataclastically deformed alaskitic granite gneiss and pegmatite from the lower tunnel, Little Johnie 

group of mines.

370-3: 1-inch-thick layer of alaskitic granite gneiss and pegmatite in migmatite from the upper tunnel, 

Little Johnie group of mines.

BC-8: Cataclastically deformed alaskitic granite gneiss and pegmatite from the Belle Creole mine.

357-6: Cataclastically deformed alaskite from the middle tunnel, Little Johnie group of mines.
52 GEOLOGY AND ORE DEPOSITS, COLORADO

The degree of gneissic structure and the composition of this gneiss 

are related to the abundance of inclusions in the gneiss. The greater 

the number of inclusions in the gneiss, the more apparent is its gneissic 

structure. Outcrops of the gneiss that contain no inclusions are 

poorly banded or massive. In composition, granite gneiss and pegmatite with few or no inclusions is an alaskite, and gneiss with abundant inclusions is granite, quartz monzonite, of granpdiorite.

The foliations and lineations in the granite gneiss and pegmatite, 

in the layers and lenses of inclusions, and in the contorted inclusions 

are all oriented with the foliations and lineations of other pre-Cambrian 

rocks in the district. Minor local variations in the broader structural 

pattern have been traced from metasedimentary rocks into granite 

gneiss and pegmatite.

Most of this rock has a fractured appearance in outcrop. In some 

of the rock the large crystals have been broken but not shattered; in 

other parts of the rock, the large crystals consist of an aggregate of 

small crystals having irregular but smooth mutual grain boundaries 

perhaps a hundred small crystals forming a patch half an inch in 

diameter. Quartz and feldspar commonly fill the fractures in the 

larger crystals and form tiny veinlets around and through the patches 

of the smaller crystals. This fabric is similar to that described by 

Ball (Spurr, Garrey, and Ball, 1908, p. 49-51) for the rock unit he 

called "gneissoid granite."

In thin section the gneiss is allotriomorphic granular. Foliation 

in the gneiss is a weak to moderate layering resulting from the concentration of the minerals into biotite-rich and quartz-feldspar-rich layers 

or into biotite-rich, quartz-rich, and feldspar-rich layers. Biotite 

is commonly in flakes along grain boundaries or in strands and is 

alined parallel to the layering. In the very weakly foliated varieties, 

the mineral layers are irregular and discontinuous.

Most of the plagioclase is partly altered some grains have clear 

rims and altered cores and others in similar positions with respect 

to the same minerals have clear cores and altered rims; no explanation is apparent for this difference. Where fresh microcline forms 

irregular patches projecting into plagioclase or forms thin irregular 

veinlets along twin lamellae, plagioclase grades into antiperthite. 

About 50 percent of the plagioclase is twinned according to the albite, 

pericline (or acline), or carlsbad laws, or combination of these. Most 

microcline is fresh and slightly perthitic. Grains of microcline occur 

scattered through the rock, as well as in pods consisting of aggregates 

of small disoriented crystals. In the granulated parts of the granite 

gneiss and pegmatite, microcline has fractures filled with quartz, 

and contacts between grains commonly show a mortar structure 

formed by fine-grained quartz and microcline in a thin irregular
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 53

band around a single grain or a group of grains. The quartz commonly 

shows strain shadows and is in large and elongate crystals, in pods 

or irregular strands parallel to the foliation, or in thin bands with 

microcline around microcline grains. Muscovite laths occupy fractures in the rock or form netlike patches in biotite, microcline, or 

altered plagioclase.

Origin. The mortar textures and rehealed crystals indicate that 

the granite gneiss and pegmatite has been deformed by cataclasis 

subsequent to the crystallization of the original rock. The podlike 

agglomerations of crystals with mutual grain boundaries are interpreted as glomeroporphyroblasts, and, because the pods locally have 

mortar texture around or through them, they are believed to represent recrystallization of the gneiss (with or without introduction of 

n£w material) prior to cataclasis. Thus, the granite gneiss and pegmatite has been deformed at least once by cataclasis, and recrystallization has affected the rock to a limited extent at the time of cataclasis 

and to an unknown extent prior to this granulation. The geologic 

history of this rock unit is, therefore, very complex, and the ultimate 

origin of this granitic unit cannot be inferred from the data gathered 

in the district.

One conclusion seems clear from the field evidence the granitic 

part of the migmatite and the granite gneiss and pegmatite are 

genetically related. No conclusive evidence has been found to show 

whether this genetic relation resulted from lit-par-lit injection of the 

Idaho Springs formation by an alaskitic magma, from either metamorphic differentiation or partial syntexis of the Idaho Springs 

formation, or both, or from transformation of the Idaho Springs 

formation by metasomatism.

GRANODIOKTTE

A few small bodies of granodiorite crop out in the western and southwestern parts of the mapped area (pi. 2), but because these bodies are 

small and poorly exposed, little could be determined about their age 

relations to the adjacent rocks of granite gneiss and pegmatite and 

biotite-muscovite granite.

The granodiorite is probably equivalent to the quartz monzonite 

mapped in the Georgetown quadrangle (Spurr, Garrey, and Ball, 1908, 

p. 51-54). About half of the Georgetown quadrangle as mapped by 

Ball is underlain by quartz monzonite, and the northern contact of a 

large mass of this rock is about half a mile south of Lamartine.

The small bodies of granodiorite in the Freeland-Lamartine district 

are usually well foliated, and much of the unit is granulated. These 

bodies may not be typical of the large masses, however, for Lovering 

and Goddard (1950, p. 27) stated that the small bodies of this rock
54 GEOLOGY AND ORE DEPOSITS, COLORADO

are strongly crushed and granulated and that foliation is best shown 

in small bodies and at the margins of the larger bodies.

In the mapped area the granodiorite is a gray or mottled black and 

white medium- to coarse-grained gneissic rock. It is readily distinguished from granite gneiss and pegmatite by the more even distribution of the biotite and from the biotite-muscovite granite by its 

abundant biotite and deformed texture.

Origin. The outcrops of granodiorite are too few and too poorly 

exposed in the Freeland-Lamartine district to allow a complete study 

of this rock unit. Ball (Spurr, Garrey, and Ball, 1908, p. 51) and 

Levering and Goddard (1950, p. 27) believed this rock to be of igneous 

origin.

BIOTTTE-MTISCOVrrE GRANITE

The youngest granite in the Freeland-Lamartine district is a relatively undeformed biotite-muscovite granite that occupies about 10 

percent of the mapped area (pi. 2). It is best exposed on Alps 

Mountain and on both sides of Trail Creek near Freeland. This 

granite is similar in fabric, mineralogy, and color to the Silver Plume 

granite from the type area at Silver Plume, Colo. Correlation of the 

biotite-muscovite granite with Silver Plume granite is not certain, 

and the writers prefer to call this rock by lithlogic name in this report.

Most of the bodies of the biotite-muscovite granite in the district 

are concordant, although some are sharply discordant. Many of the 

bodies are hook shaped and crescent shaped in their surface exposure 

and are in axial regions of folds (pi. 2).

Contacts between biotite-muscovite granite and other pre-Cambrian 

rock units are generally sharp, but locally the contacts are indistinct 

and transitional over a width of a few feet. At a few localities where 

this granite is in contact with metasedimentary rocks a transition zone 

of vaguely defined layers or irregular pods of granite and metasedimentary rocks separates typical granite from typical metasedimentary rock. This type of contact is rare in the district, and the 

transition zone is generally only a few inches wide. Most of the 

sharp contacts have a few inches to a few feet of pegmatite along 

them.

The granite ranges from a nearly massive rock to a foliated rock; 

the foliation results from nearly parallel arrangements of tabular 

microcline crystals and biotite laths. The foliation is subparallel 

to the contacts of the granite bodies.

At places the granite contains prominent subparallel fractures that 

commonly are spaced as close as one-eighth of an inch; at other places 

these fractures are only faintly visible in outcrops though prominent 

in. thin sections, and at still other places these fractures are not
FREELAND-LAMARTESTE DISTRICT, CLEAR CREEK COUNTY 55

megascopically visible though visible in thin sections. In this report 

the writers will refer to these fractures as incipient fractures. At 

localities where the incipient fractures are best formed, the surfaces 

of these fractures have slickensides outlined by %- to 1-inch-wide 

streaks of chlorite, biotite, and muscovite. The few slickensides 

observed are not consistent in bearing from layer to layer through 

the rock. At outcrops where the incipient fractures transect the 

foliation, individual crystals and planes of crystals are disrupted with 

the result that the foliation is almost destroyed.

In the Freeland-Lamartine district, the biotite-muscovite granite 

is a gray to tan or buff fine- to medium-grained rock that has seriate 

porphyritic texture. At places a fine-grained equigranular facies 

occurs in small, irregular bodies within the seriate porphyritic facies. 

All the facies are composed principally of microcline, plagioclase 

(oligoclase to sodic andesine), and quartz; biotite and muscovite are 

minor constituents. The accessory minerals include zircon, apatite, 

monazite, and magnetite. Eight modes of typical Silver Plume granite 

are shown in table 7, and the variation in composition is indicated by 

the triangular diagram (fig. 55).

TABLE 7. Modes (volume percent) of biotite-muscovite granite

Biotite-- - - ___

2-2a-135

26

33

24

9

6

1

Trace

Trace

Trace

2-6a-S3

30

30

31

3

4

1.3

Trace

2-6b-7

42

22

28

.6

6

.9

Trace

Trace

Trace

2-7a-18a

21

31

38

6

4

.6

2-7a-18b

25

29

34

4

7

Trace

Trace

Trace

BC-5

28

28

31

4

8

Trace

Trace

TrsicG

La-19

42

21

33

1

3

Trace

Trace

La-20

35

32

28

2

2

.8

Trace

Trace

2-2a-135: Biotite-muscovite granite containing incipient fractures from outcrop on the ridge east of Freeland.

2-6a-53: Well-fojiated granite from a small pod 800 feet southeast of the collar of the Gum Tree shaft.

2-6b-7: Well-Miated granite from an outcrop along Trail Creek 200 feet east of the point where the road 

crosses Trail Creek near Freeland.

2-7a-18a: Well-foliated granite from the east peak of Alps Mountain.

2-7a-18b: Well-foliated granite adjacent to a 2-inch pegmatite dike on the east peak of Alps Mountain.

BC-5: Faintly streaked granite from the Belle Creole tunnel.

La-19: Massive gray granite from the Lamartine tunnel.

La-20: Massive buff granite from the Lamartine tunnel.

In thin section the granite is allotriomorphic to hypidiomorphicgranular. Most of this rock has a seriate porphyritic texture fresh 

microcline in anhedral to subhedral laths commonly forms crystals 6 

millimeters long; altered plagioclase and quartz form crystals 1 to 3 

millimeters in diameter; and quartz, plagioclase, biotite, and muscovite 

occur in the fine-grained groundmass. Opaque hairlike inclusions 

(nitile?) are abundant in most of the larger quartz crystals and in 

some of the larger plagioclase crystals. Myrmekite is common at the 

edges of plagioclase crystals where they contact microcline or quartz.
56 GEOLOGY AND ORE DEPOSITS, COLORADO

Thin sections of rocks containing the incipient fracture have a weakly 

formed mortar structure similar to that seen in the granite gneiss and 

pegmatite.

Most of the muscovite in the deformed rock occurs in the incipient 

fractures interleaved with biotite or in irregular patches and networks, 

in microcline or plagioclase.

The granite has a high radioactivity one typical fresh sample from 

the Lamartine mine assayed 0.006 percent equivalent uranium, 0.004 

percent uranium, and 0.006 percent thorium. No discrete uraniumminerals were recognized in the thin sections, but George Phair (oral 

communication, 1953) reported that from separations and analysis of 

accessory minerals he had tentatively concluded that the principal: 

source of radioactivity in the granite is monazite.

Origin. The small amount of deformation of the biotite-muscovite 

granite combined with an internal structure in the granite which 

parallels irregular contacts that crosscut older foliated rocks suggest 

to the writers that the granite is of magmatic origin. The foliation 

in the granite is, therefore, interpreted as flow structure rather than. 

planes of minerals formed by metamorphic processes.

The incipient fractures are believed to be related to a postgranite 

stress distinct from the stress prevailing at the time of intrusion of the 

granite. Cloos (1933, p. 239) states that continued stress and subsequent movement after crystallization of a pluton results in fractures, 

that are parallel to the flow structure. The incipient fractures in 

biotite-muscovite granite commonly transect the flow structure in the 

granite. The bearing of the slickensides on the incipient fracture 

surfaces does not parallel that of the foliation planes as described by 

Balk (1937, p. 106-107) for flat-lying normal faults. The texture of" 

this granite containing the incipient fractures is similar to that of the 

deformed parts of the granite gneiss and pegmatite. The writers have 

tentatively concluded that the incipient fractures in biotite-muscovite 

granite are related in time to the cataclasis of the granite gneiss and, 

pegmatite and that the cataclasis occurred after solidification of" 

biotite-muscovite granite.

GRANITE PEGMATITE

Dikelike and podlike bodies of granite pegmatite cut all other preCambrian rocks in the mapped area (pi. 2). One body, irregular im 

shape, was large enough to be mapped. The dikes range in width from 

1 inch to 10 feet, and the pods are as much as 500 feet in diameter.. 

The dikelike bodies are most common along joint surfaces in biotitemuscovite granite and older pre-Cambrian rocks, and as subconcordant 

layers in metasedimentary rocks. The podlike bodies of pegmatite are^ 

abundant in granite gneiss and pegmatite.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 57

The pegmatite is a pink to white coarse-grained granite composed 

essentially of microcline (commonly perthitic) and quartz with minor 

albite. Locally the pegmatite contains black tourmaline or one-half 

of an inch thick books of muscovite or biotite. Pegmatite associated 

with the granite gneiss and pegmatite locally contains subhedral to 

euhedral crystals of magnetite as much as an inch hi diameter; discontinuous stringers of magnetite as much as one-fourth of an inch 

thick are present in some outcrops.

Origin. Most of the pegmatite in the district is believed to be 

genetically related to either biotite-muscovite granite or granite gneiss 

and pegmatite. The magnetite-bearing pegmatite and the non^ 

magnetite-bearing irregular patches and pods of pegmatite in the 

granite gneiss and pegmatite are believed related to that unit. The 

pegmatite around the margins of and in joints in the biotite-muscovite 

granite are believed to be related to that granite. Much of the pegma^ 

tite in the district, however, is not visibly connected with either of 

these granite rocks. As most of the nonmagnetite-bearing pegmatite 

throughout the district has a similar mineralogy and degree of defor-- 

mation, masses of pegmatite not visibly connected with a granitic 

body cannot be readily separated into distinct age groups. Ball (Spurr^ 

Garrey, and Ball, 1908, p. 60-64) found a similar problem in distinguishing between pegmatites of three different ages that occur iij 

the Georgetown quadrangle.

TERTIARY INTRUSIVE ROCKS

Porphyritic intrusive rocks quartz monzonite, alaskite, syenitic 

bostonite, and quartz bostonite occur as dikes and small plugs that 

cut the pre-Cambrian rocks in the Freeland-Lamartine district. So. 

far as known, the intrusive rocks are confined to the southeastern part, 

of the mapped area (pi. 2). The dikes range in length from 200 to. 

2,600 feet, and in width from a few feet to 100 feet; generally the 

width is about 15 feet. Most of the dikes trend northeasterly, but a, 

few trend northwesterly. Because of the sparse exposures, little is, 

known concerning the true dip of the dikes, but their surface traces, 

suggest that all are vertical or dip steeply to the north. The age of the 

dikes has been established as early Tertiary by Lovering and Goddard 

(1950, p. 47).

The sequence of intrusion of the porphyries in the FreelandLamartine district cannot be determined. Phair (1952, p. 20-22) 

inferred from work in the Central City district that the sequence is. 

monzonite, syenitic bostonite, quartz bostonite. The alaskite is. 

indicated by Lovering and Goddard (1950, p. 44-47) to be youngerthan the monzonite and older than the bostonite.
58 GEOLOGY AND ORE DEPOSITS, COLORADO

An alaskite plug with a radiating dike pattern occurs near the 

eastern boundary of the mapped area, and a syenitic bosonite plug was 

mapped on the ridge southwest of the collar of the Invincible shaft. 

The geometric pattern of those bodies, particularly of the alaskite, 

suggests that they were forcefully intruded.

CLASSIFICATION

Phair (1952) classified the Tertiary intrusive rocks of the Central City 

district, 5 miles to the northeast, according to overall texture, groundmass texture, quartz content, type of feldspar, and presence or absence 

of mafic minerals. Phair also presented a correlation between the 

type of intrusive and a range of radioactivity. In this report Phair's 

classification has been followed with but slight modification because 

of minor differences in the mineralogy and radioactivity (table 8). 

Phair gave the range of radioactivity for the syenitic bostonite in the 

Central City district as greater than 0.004 percent and less than 0.007 

percent equivalent uranium; in this report the upper limit has been 

extended to 0.009 percent equivalent uranium. A rock type has been 

added to Phair's table, the alaskite porphyry, that has a moderate 

range of radioactivity and a usual mineral content for alaskites. The 

samples of quartz bostonite from the district are so intensely altered 

that the data on their radioactivity is unreliable and is not presented 

in this table as characteristic.

TABLE 8. Classification of the Tertiary intrusive rocks. 

[Classification modified from Phair (1952)]

Rock type

Nonporphyritic quartz bostonite __

Alaskite porphyry ___ . ______

Average 

equivalent 

uranium 

(percent)

>0. 014 

>.007,

<.014 

>nnd

<.009 

>.006,

<.007 

>.002,

<.007

Diagnostic features

5-15 percent quartz, <5 percent phenocrysts, bostonitic 

texture, usually reddish brown in hand specimen.

crysts, bostonitie texture, usually lilac in hand 

specimen.

phenocrysts, may contain hornblende or garnet, 

faintly to well-defined bostonitic texture, lilac to 

brown in hand specimen.

phenocrysts, <5 percent mafic, poikilitic granular 

groundmass texture, gray to buff in hand specimen.

phenocrysts, may contain quartz, hornblende, or 

biotite phenocrysts also, granular texture, gray in 

hand specimen.

In spite of the intense alteration of the rocks in the district, reasonably certain identification of the rocks has been made from the 

combined megascopic, microscopic, and radioactivity data. Only 

rarely was it possible to determine the type of plagioclase in the rock, 

and in some specimens the plagioclase could not be distinguished from
FREELAND-LAMAR'

the potash feldspar. S 

specimens complicating 

The f erromagnesian mine 

and alteration products

The bostonites are dis 

on the basis of ground 

table 8); the quartz bost 

of quartz content and 

bostonite; and the 

plagioclase phenocrysts i

ondary quartz is present in a few of the 

the estimation of original quartz content, 

 als can be recognized only by crystal outline 

i most slides.

inguished from the monzonite and alaskite 

mass texture and hand-specimen color (see 

nite from the syenitic bostonite, on the basis 

)resence of mafic minerals in the syenitic 

monzonite from the alaskite, by the presence of 

L the monzonite.

QUARTS

South of Trail Creek 

quartz monzonite porph 

easterly and easterly. r. 

black flecks fine- to medh 

essentially of quartz anc 

5 to 15 percent of quartz 

of which are zoned. Th 

with white phenocrysts.

Microscopically the gr 

allotriomorphic to poikil 

porphyry), and consists p 

The phenocrysts of pla 

apatite, and topaz are eu 

to 4 millimeters hi length 

others are not. The con 

albite and exhibit albit< 

The few crystals with u 

the centers are oligoclase 

analysis of one thin secti 

lar groundmass gave a 

feldspar, 28 percent plagic 

trace amounts of magnet

The radioactivity of tl 

0.003 to 0.004 percent eq

Alaskite porphyry occurs

the eastern boundary of 

trending dike near the ce

The alaskite is a gray 

rock commonly containin 

consists essentially of qu

370788 56 3

:NE DISTRICT, CLEAR CREEK COUNTY 59

MONZONITE PORPHYRY

near the abandoned town of Freeland, thq 

ry forms branching dikes that trend northbe quartz monzonite is a gray to buff with 

m-grained seriate porphyriiic rock consisting 

plagioclase. The rock commonly contains 

feldspar, and hornblende phenocrysts, some 

weathered rock is buff to yellowish brown

 undmass is fine grained (0.05 to 0.2 mm), 

ic granular (term described under Alaskite 

edominantly of quartz with magnetite flecks, 

ioclase, sanidine, ferromagnesian minerals, 

edral and range in size from the groundmass 

Some plagioclase phenocrysts are twinned, 

pletely twinned plagioclase phenocrysts are 

or, more rarely, carlsbad-albite twinning, 

twinned centers are compositionally zoned; 

and the margins are nearly pure albite. An 

n of a specimen with allotriomorphic granumode of 66 percent quartz, 2 percent potash 

lase, 4 percent ferromagnesian minerals, and 

te, apatite, and topaz.

s quartz monzonite in this area is low, from 

ivalent uranium.

PORPHYRY

as a small plug with radiating dikes near 

the district and as a short northwestwarditral part of the district, 

o buff fine- to medium-grained porphyritic 

15 to 20 percent of phenocrysts. The rock 

rtz and potash feldspar. The groundmass
60 GEOLOGY AND ORE DEPOSITS, COLORADO

has a porcelaneous to flinty surface, and the phenocrysts are equidimensional. The weathered surface is gray to buff and generally is pitted 

owing to the removal of the phenocrysts.

Microscopically the rock is characterized by a poikilitic granular 

groundmass hi which small (0.1 to 0.4 mm), irregular to circular 

quartz grains with mutually sutured boundaries include small euhedral 

to subhedral grains, probably feldspar. These small grains-are cloudy 

with a leucoxenelike appearance in the more altered specimens. The 

phenocrysts are orthoclase, sanidine, and small quantities of ferromagnesian minerals, magnetite, sphene, and topaz. The orthoclase 

phenocrysts are generally more abundant, more altered, and larger 

(2 to 3 mm) than the sanidine (1 to 2 mm). The ferromagnesian 

minerals (1 to 2 mm in length) are completely altered to sericite and 

magnetite. The approximate mode (volume percent) is 44 percent 

quartz, 52 percent orthoclase, 2 percent ferromagnesian minerals, and 

trace amounts of topaz, sphene, and magnetite.

The radioactivity of the alaskite porphyry ranges from 0.006 to 

0.007 percent equivalent uranium although one sample, taken near a 

radioactive vein, assayed 0.011 percent equivalent uranium.

STTENITIC BOSTONITE PORPHYRY

Syenitic bostonite is the most abundant type of dike rock in thedistrict and forms small elongate plugs and branching dikes that 

trend northerly and northeasterly across the east-central part of the 

mapped area. The northward-trending dikes are in a group geographically separate from a group of northeastward-trending garnetbearing dikes.

Syenitic bostonite is a lilac to brown fine- to medium-grained seriate 

porphyritic rock that commonly contains 10 to 65 percent of phenocrysts. The weathered rock is gray to buff, and the surface may be 

pitted owing to the removal of phenocrysts, especially of the mafic 

minerals. The rock consists essentially of orthoclase, plagioclase, and 

amphibole; black garnet occurs in subordinate amounts. The feldspar phenocrysts are both zoned and unzoned, and the amphibole 

commonly occurs as radiating aggregates.

Microscopically, the groundmass has a trachytoid or faintly trachytoid texture that commonly shows marked flow structure around 

the phenocrysts. The feldspar phenocrysts are as much as 1.5 

centimeters long and are plagioclase (albite, showing albite twinning) 

and orthoclase.

The unaltered rock contains less than 5 percent of primary quartz; 

the altered rock, however, commonly has veinlets or pods of finegrained and chalcedonic quartz that at places amounts to several 

percent. The ferromagnesian minerals are as much as L5 millimeters
FRE1LAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 61

long and have been altered so that only pseudomorphs of chlorite,, 

sericite, quartz, and magnetite remain. The accessory minerals are 

sphene, magnetite, and zircon. The approximate mode, considering 

the groundmass as orthoclase feldspar is 75 to 80 percent orthoclase, 

8 to 19 percent plagioclase, 2 to 4 percent ferromagnesian minerals, 

1 percent garnet, and trace amounts of magnetite, zircon, apatite, 

and calcite. The garnet content may be relatively large as showtt 

by one specimen that contained 4 percent garnet. The quantity 

of orthoclase as phenocrysts is relatively constant at about 21 percent.

In thin section the garnet forms euhedral crystals as much as 2 

millimeters in diameter. The garnet is brown and is generally altered 

to limonite, chlorite, and calcite. The index of refraction determined 

in oils is about midway between 1.852 and 1.861. An X-ray analysis 

by A. J. Gude 3d, U. S. Geol. Survey laboratory, gives a0 to be 12.013 

angstrom units. The refractive index and a0 of the garnet indicate 

that it consists principally of the andradite molecule.

The radioactivity of the syenitic bostonite porphyry ranges from 

0.003- to 0.009 percent equivalent uranium. The garnetiferous variety 

has'lower radioactivity (0.003 to 0.006 percent equivalent uranium)' 

than the nongarnetiferous variety (0.006 to 0.009 percent equivalent 

uranium).

QUARTZ BOSTONITE

The quartz bostonite in the district consists of both the porphyritie 

and nonprophyritie varieties. The nonporphyritic quartz bostonite 

occurs as dikes on the ridge near the north boundary of the area. 

This rock is fine grained and intensely altered to a tan. The characteristic quartz grains poikilitically enclosing feldspar laths and tJfrex 

trachytiod texture, though poorly formed, can be seen in thin sections 

of this rock.

Only one specimen of porphyritie quartz bostonite was found in thedistriet. This specimen, from the dump of the Diamond Mountain 

mine, is not considered representative because it is intensely altered.

The radioactivity of the samples of quartz bostonite from the 

district is lower (0.006 tio 0.010 percent equivalent uranium) thanr 

that of the quartz bostonites in the Central City district (Phair, 1952).; 

The low radioactivity may be due to the intense alteration of the rock,

QUATERNARY DEPOSITS

Three types of unconsolidated Quaternary deposits were mapped 

in the Freeland-Lamartine district solifluctional debris, avalanche 

ridges, and alluvium. The solifluctional debris occurs hi sheets asbroad high-basin deposits as well as in valley fills and consists of 

unsorted material ranging in size from boulders to silt. Avalanche 

ridges, consisting of poorly sorted material ranging in size from silt
GEOLOGY AND ORE DEPOSITS, COLORADO

to cobbles, occur in some of the tributary valleys of Trail Creek. The 

alluvium is on the valley floor of the major stream.

SLUMP DEPOSITS

Two solifluctional debris sheets of unsorted heterogeneous rock 

fragments are at the head of Trail Creek between altitudes of 10,200 

and 10,700 feet (pi. 2). The sheets occur in broad basins and have 

irregular terraces marking their surfaces. One is about 1,500 feet 

wide and 3,000 feet long; the other is about one-fifth as large. The 

thickness of these debris sheets is unknown, but similar sheets are 

reported by Spurr, Garrey, and Ball (1908, p. 87) to range from 20 

to 100 feet hi thickness. Debris similar to that in the sheets fills >po-ts 

of the valleys of the tributaries to Trail Creek.

The debris sheets and valley fills are composed of material from 

the surrounding ridges. The rock fragments range in size from 

boulders to silt; they are not sorted. The deposits appear to be 

colluvial and slump material of local origin. Gerald Richmond, who 

has studied the Pleistocene geology of parts of the Front Range, 

stated (oral communication, 1953) that the solifluctional debris sheets 

at the altitude of those at the head of Trail Creek are Wisconsin hi 

age and are probably early Wisconsin.

AVALANCHE DEPOSITS

Small ridges of poorly sorted silt, sand, and cobbles occur along two 

of the small tributaries of Trail Creek. The ridges are about 50 feet 

wide on the crest and have a relief of about 20 feet above the valley 

floor. These ridges have been noted only in small valleys on northfacing slopes. The ridges are probably the result of movement of 

water-saturated slump debris. These deposits according to Richmond 

(oral communication, 1953) are also Wisconsin, probably early 

Wisconsin, in age.

ALLUVIUM

A thin cover of Recent alluvial material is present along the valley 

flat of Trail Creek. Some of this material is mill tailings from mills 

no longer working. An old 10-stamp mill below the dump at the 

Lamartine shaft contributed much of the material mapped as^alliwiuaii 

on the north-facing slope at the head of Trail Creek (pi. 2).

STRUCTURE

The bedrock in the Freeland-Lamartine district is a generally 

conformable series of metamorphic and igneous rocks. The rocks 

were folded during pre-Cambrian time, and many of the folds are now 

outlined by the lithologic layering. The rocks are jointed and are 

cut by numerous faults; some of the joints now contain porphyry
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 63

rocks of Tertiary age, and many of the faults locally contain 

gofd-silver-lead-zinc ores of Tertiary age.

Tbe structural history of the bedrock in the Freeland-Lamartine 

district is complex. Several of the elements involved in creating the 

present structural pattern cannot be dated with much accuracy. A 

general summary of the structural history follows: (1) Late preCambrian northeast folding accompanied by intrusion of biotitemuscovite granite; (2) northwest warping and cataclastic deformation 

of biotite-muscovite granite and granite gneiss and pegmatite; (3) 

early Laramide(?) arching resulting in the formation of the regional 

joint pattern; and (4) Tertiary fracturing and faulting followed by 

intrusion of dikes and deposition of hydrothermal veins.

FOLDS

Two fold systems can be recognized in outcrops in the district. 

Broad arcuate patterns of some of the rock units serve to outline some 

of the larger folds, and traces of axial planes of the folds are shown on 

the geologic map (pi. 2). The most prominent fold system trends 

northeasterly, and the axis of this system is called 61 hi this report. 

The selection of 61 is based upon evidence of a strong crumpling of 

the rocks into compressional folds trending in a northeastward direction. A much less prominent fold system trends northwesterly, 

and the axis of this system is called 62 in this report. The selection 

of 6jvis considered tentative as it was chosen on the basis of a persistesfc-northwesterly lineation and observed warping along northwesterly 

trends of the major folds.

Lineations related to both of the fold systems are present in outcrops of the district. The types of lineations present include mineral 

alinement, streaks, crinkles (small crenulations whose amplitude to 

wave length ratio is about 1:1), warps (crenulations whose amplitude 

to wave length ratio is about 1:2 or smaller), drag folds, and fold axes, 

All of these types of lineations are found on both fold systems in both 

the a and 6 directions. Most of the lineations are hi 6 directions; 

that is, parallel to the axis of the major or minor fold system. A few 

lineations were found in a directions; that is, perpendicular to the 

major or minor fold axes.

All of the lineations measured in surface outcrops were plotted on 

the lower hemisphere of a Schmidt equal-area net. The net was then 

contoured, and the resulting diagram is shown in figure 6. Both of 

the fold systems recognized in the field are represented on this diagram. 

The major fold system (61) is indicated by the strong "bullseye" and 

has ,an average plunge of 27° N. 20° E. The minor fold system (62) 

is indicated by the smaller "bullseye" and has an aveiage plunge of 

47° N. 28° W. Because the lineations in bi tend to be deflected as
64 GEOLOGY AND ORE DEPOSITS, COLORADO

N

Note: Contoured in 

percent of poles

bi-major fold axis, bz-minor fold axis 

FIGURE 6. Contour diagram of lineations, lower hemisphere plot of 344 poles.

they pass over the crests of the 62 folds, the minor fold system is 

considered to be younger than the major fold system.

The fold axes are sinuous both horizontally and vertically. Changes 

in strike of the traces of axial planes (pi. 2) represent somewhat the 

change in direction of fold axes; variation in amount and direction of 

plunge of one of the folds is shown on the cross section (pi. 3) wfeieh 

is almost parallel to the axial plane of one of the major folds.

Upright, overturned, and recumbent folds are observed in the 

district. The recumbent folds are sparse and most of them are small 

(1 to 8 inches across). Overturned folds are common along the 

flanks of the major folds which trend northeasterly across the center 

of the mapped area (pi. 2). Details of some of the overturned folds 

are shown in the vertical section along the Old Stag tunnel (pi. 4) 

which has been driven through the northwest flank of a major fold.
FREELANDHLAMARTINE DISTRICT, CLEAR. CREEK COUNTY 65

Because the folds open out into upright folds toward the axial region 

and the axial planes of the folds on the flanks converge upward, the 

major fold could best be described as an abnormal anticlinorium. 

Toward the eastern edge of the mapped area (pi. 2), the major folds 

are more open and exhibit little overturning on their flanks. The 

vertical section through the Freeland-Lamartine district (pi. 2) is 

approximately perpendicular to the trend of the major fold axes and 

illustrates both open and overturned folds on the flanks of certain of 

the major folds.

The distribution of certain of the rock units is clearly related to the 

folds. One of the most apparent relations shown on the geologic 

map occurs where phacoliths of biotite-muscovite granite outline fold 

crests and troughs. In addition, most of the metasedimentary rocks 

in the granite gneiss and pegmatite are found on fold crests or troughs 

(pi. 2), and the pinch and swell of rock layers along fold axes appears 

to be partly related to changes in plunge of the fold axis (pi. 3 and 

%. 7).

Age relations of the folding. Dating of the folding is based primarily 

on whether rocks in the district have been plastically or cataclastically 

deformed, or both. The older folding was plastic, and the younger 

folding was cataclastic in part. The only rock unit that appears 

to show only cataclastic effects is the biotite-muscovite granite the 

youngest pre-Cambrian rock in the district. This granite is, however, 

in phacoliths along folds of the older system. These data are interpreted as indicating that the older fold system plastically deformed 

all rocks younger than biotite-muscovite granite which was intruded 

in phacolithic bodies into fold crests and troughs late in the northeast 

folding. A later warping of the older northeastward-trending system 

produced the minor northwestward-trending.fold system. The final 

stages of the warping caused cataclasis that is now most evident in 

the granite gneiss and pegmatite and the biotite-muscovite granite.

FAULTS 

GENERAL. STATEMENT

Although most of the faults in the Freeland-Lamartine district dip 

steeply to the north, the Freeland group and the Turner-Falu are 

 exceptions in that they dip only 30°-50° NW. Many of the faults 

are bordered by zones of sheeting and fracturing, indicating repeated 

movement along the fault or fault zone. Although local areas on a 

fault may show slight reverse movement, the overall movement has 

been normal. In addition to dip-slip movement, strike-slip movement has occurred, causing the northwest blocks to move northeast 

relative to the southeast blocks. As the faults all dip to the north,
9000'-

Datum is mean sea level

FIGURE 7, Vertical projection through the Little Joh
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 67

the general movement on the faults in the district is for the northwest 

blocks to move down and to the northeast relative to the southeast 

blocks. The age of the faulting has been established as Tertiary by 

Lovering and Goddard (1950, p. 44-47).

The amount of movement on the faults generally has been small. 

Many veins of the district cross without noticeable displacement. 

An apparent horizontal offset, however, of about 100 feet was mapped 

on the surface where a Tertiary dike is offset along the Freeland vein.

Evidence that the faults containing the veins were formed under 

regional shear stress is presented by Lovering and Goddard (1950, 

p. 80) who have concluded that the main shear couple was composed 

of stresses exerted toward the northeast on the northwest side of the 

mineral belt and toward the southwest on the southeast side of the 

mineral belt. This conclusion is borne out by the movement on 

faults in the Freeland-Lamartine district.

SEQUENCE OF FAULTING

Three principal sets of faults, those trending north-northeastward, 

east-northeastward, and eastward, have formed under the regional 

shear stress. In plate 2 and figure 8 the faults are indicated by the 

veins which occupy them. In figure 8 the major veins in the district 

have been projected to 9,500 feet altitude to eliminate the effect of 

topography on the true strike.

Data on age relations among the fault sets, although not abundant, 

are consistent. The north-northeastward-trending faults, represented 

by the Oneida, Great Western, Lone Tree, New Era, and Freeland 

veins, are crosscut and sometimes offset by east-northeastward- and 

eastward-trending faults. The Great Western vein is offset along the 

Mendick (east-northeast) vein in the New Era mine. In this same 

mine, in an exposure at the junction of the main tunnel and the southernmost crosscut, the New Era vein is offset along an eastwardtrending vein. The Oneida vein is cut by eastward-trending veins 

in at least two places along the Lamartine tunnel.

The trace of axial planes of pre-Cambrian folds and the trace of 

veins occupying the oldest faults is essentially parallel as is shown in 

plate 2. Mapping of the New Era, Old Stag, and Lamartine mines 

has shown that the north-northeasterly veins tend to follow axial 

planes of pre-Cambrian folds. The first breakage of the bedrock 

under Tertiary shear stress was selective in that the rock broke along 

preexisting planes of weakness.

The east-northeastward-trending faults, represented by the Mendick, Golden Rod, Alabama, Crazy Girl, and Miller veins, are younger 

than the north-northeastward-trending faults but older than the 

eastward-trending faults. Near the junction of the Oneida vein (here
68 GEOLOGY AND ORE DEPOSITS, COLORADO
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 69

trending east-northeastward) and the Lamartine vein (eastwardtrending vein) in the Lamartine tunnel, eastward-trending fractures 

not only cut through the Oneida vein but are also filled with minerals 

characteristic of the Lamartine vein. In the Turner mine, the eastnortheastward-trending part of the vein is cut by eastward-trending 

faults. The relations are particularly well exposed on the third level 

to the west of the underground shaft.

The east-northeastward-trending faults have the position of tension 

fractures related to the north-northeastward-trending faults, but the 

movement on them has been by shear, at least in part.

Eastward-trending fractures cut through and locally offset both 

north-northeastward- and east-northeastward-trending faults. The 

eastward-trending faults are represented by the Lamartine, Mammoth, 

Crown, Harrisburg, Split, and Anchor veins. These faults are 

clearly the youngest in the district. They may either be tension 

fractures related to the east-northeastward-trending faults or preexisting joints along which later movement has taken place. As the 

two most prominent preshearing joint sets in the district trend 

slightly north of east and slightly south of east (see p. 70 and figs. 10, 

11), and as these joints are weakly mineralized in many outcrops 

of the district, the writers prefer the explanation that the eastwardtrending faults formed by movement on preexisting joints.

Interpretation of the data on the age relations among the three 

fault sets,has led to the determination of age relations expressed 

diagrainmatically in figure 9. The total amount of time expressed in 

this diagram is probably a small part of the Tertiary period; the eastnortheastward-trending faults are essentially contemporaneous with, 

but slightly younger than, the north-northeastward-trending faults; 

and the eastward-trending faults are essentially contemporaneous

TIME

H ENE.

-I

< E. 

LL

FKFCTRE 9. Diagram Illustrating the age relations among the fault sets.
70 GEOLOGY AND ORE DEPOSITS, COLORADO

with, but slightly younger than, the east-northeastward-trending 

faults.

In general, faults belonging to the younger sets formed principally 

at the ends of the next previous set. The north-northeastwardtrending faults formed approximately parallel to axial planes of folds 

in the pre-Cambrian bedrock; these faults were followed by eastnortheastward-trending tension fractures which formed at both ends 

of the north-northeastward trending faults; and finally, eastwardtrending faults formed at the ends of the east-northeastward-trending 

fractures probably as a result of movement along preexisting joint 

surfaces. The pattern resulting from the combination of fractures 

in this manner is one which shows long cymoid-shaped fissures. 2 

These are well illustrated by the Freeland, Oneida, and Lone Tree 

veins (fig. 8). The central parts of these cymoids are the oldest 

fractures, and the ends of the cymoids are the youngest.

JOINTS

GENERAL STATEMENT

Joints are present in all of the rocks in the Freeland-Lamartine 

district, and considerable data concerning them were collected during 

surface geologic mapping. The joints were plotted on the upper 

hemisphere of a Schmidt equal-area net by using the pole of the plane 

which describes the joint surface hi the field (fig. 10). The upper 

hemisphere was chosen for this plot because the pole thus plotted falls 

into the quadrant of its true dip direction; that is, the pole of a plane 

dipping northeastward falls into the northeast quadrant of the 

diagram.

REGIONAL JOINT PATTERN

A statistical representation of the regional (district-wide) joint 

pattern is shown in figure 10. The poles of 1,680 joints in all j?ock 

types were plotted on a net which was then contoured. The data 

shown on this diagram are approximately in proportion to the areal 

extent of the rock types; about 50 percent of the data is from granite 

gneiss and pegmatite; 25 percent, from metasedimentary rocks; and 

25 percent, from biotite-muscovite granite.

The contour diagram discloses four prominent joint sets. The 

most prominent joints strike N. 74° W. and N. 82° E. and dip 68° and 

62° N. respectively. Field data are insufficient to state whether th& 

prominent joints at N. 77° W., 82° SW. are related to the N. 74° W.i, 

68° NE. joints or represent pre-Cambrian cross joints. Next most 

prominent are joints which strike N. 22° W. and dip 79° NE. The

 A cymoid is a reverse curve in which a line swerves from its course and then swings back again, resuming 

a direction parallel to its former course but not in line with it (McKinstry, 1948, p. 315).
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 71

N

Note: Contoured ora 

number of poles

FIGURE 10. Contour diagram of joints, upper hemisphere plot of 1,680 poles. ,

fourth and weakest recognizable joint set strikes N. 56° E. and dips 

63° NW. These joint sets were plotted on the lower hemisphere of 

a stereographic net; the resulting diagram is shown in figure 11.

This diagram is interpreted to indicate that a joint system is present 

containing longitudinal (/), cross (c), and two diagonal (di and <4) 

joint sets. The major fold axis (61) and the minor fold axis (62) have 

been plotted on this diagram for comparison. The strike of the 

longitudinal joint (I) should coincide with the bearing of one of the 

pre-Cambrian fold axes if the regional joint pattern is related to preCambrian folding. In addition, the cross joint (c) should be approximately at right angles to a related fold axis. The trend of the major 

fold axis (61) does not parallel the strike of the longitudinal joint set (/). 

Although the trend of the minor fold axis (62) is near the strike of the 

longitudinal joint set (/), the cross joint (c) dips 62° NW., whereas
72 GEOLOGY AND ORE DEPOSITS, COLORADO 

N

I-longitudinal joint; d/ and d2 - diagonal joints;

c-cross joint; b{-major fold axis, b2-minor fold axis

FIGURE 11. Stereographic diagram showing main joint sets and principal fold axes.

it should dip 43° SE. if related to the minor fold axis (which plunges 

47° NW.). The tentative conclusion drawn from these data is that 

the regional joint pattern is not related to the pre-Cambriaji folding. 

This is not to say that there are no joints in the district that are 

related to the folding but rather that the most prominent and extensively formed joint sets are not related to the folding.

The formation of the regional joint pattern cannot be dated with 

great accuracy. The regional joint pattern does not appear to be 

the result of Tertiary fracturing, yet it has been imposed upon the 

pre-Cambrian folding; therefore, the pattern can only be dated as 

post-pre-Oambrian and pre-Tertiary. Levering and Goddard (1950, 

p. 57-58) gave a brief summary of the Laramide structural history
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 73

of the Front Range region. They stated that the Front Range highland (as shown in fig. 3) was a positive area intermittently during the 

Paleozoic and Mesozoic eras and that the last uplift of the Front 

Range probably began in Late Cretaceous (Pierre shale) time. The 

present Front Range highland is an oblong area trending about 

N. 22° W., and this trend is the same as that of the longitudinal joint 

set in the Freeland-Lamartine district. The cross joint set in the 

district suggests a fold or warp related to this joint which would plunge 

about 28° SE. The Front Range highland disappeared under younger 

sedimentary rocks south and southeast of Cripple Creek, Colo., 

southeast of the Freeland-Lamartine district. The accordance between the regional joint pattern of the Freeland-Lamartine district 

and that expected from a study of the Laramide structural history of 

the Front Range has led the writers to infer that the regional joint 

pattern is early Laramide in age.

ECONOMIC GEOLOGY

The Freeland-Larmartine district, in the Front Range mineral belt, 

contains gold-, silver-, copper-, lead-, and zinc-bearing veins that were 

formed as hydrothermal fissure fillings in faults. Replacement of the 

wall rocks by the ore minerals was unimportant as a method of formation of the ore deposits. Most of the veins have smooth walls; 

slickensides are abundant but inconsistent in bearing and plunge. 

The fissures are fairly regular in strike and dip, and irregularities, where 

present, commonly provided favorable structures for the deposition 

of the ore minerals.

The principal ore minerals are sulfides and sulfosalts of iron, copper, 

lead, and zinc, but locally some free gold was found. Three types of 

veins have been mined in the district: pyrite-gold veins mined chiefly 

for gold; galena-sphalerite veins mined chiefly for silver, lead, and 

zinc; and composite veins mined for gold, silver, and lead. Most of 

the veins in the district are of the galena-sphalerite or composite 

type. Quartz is the most abundant gangue mineral, but carbonates 

locally form as much as 80 percent of the gangue.

Lead-uranium determinations on pitchblende from veins in the 

Central City district (about 5 miles northeast of the FreelandLamartine district) made by Holmes (1946) and by Phair and others 

(George Phair, written communication, 1954), indicate an age for 

those veins of about 60 million years (early Tertiary). As the veins 

in the Freeland-Lamartine district are in the same geologic setting 

as the veins in the Central City district, it seems probable that these 

two groups are the same age.
74 GEOLOGY AND ORE DEPOSITS, COLORADO

PRODUCTION FROM THE DISTRICT

Production records for the mines of the district are nearly complete for the period 1905 to 1953. 3 Previous to 1905 systematic records were not kept for all mines in the district. On the basis of 

existing information, however, the writers estimate that from 1868 

to 1905 ore valued at $5 million or more was extracted. The production figures given in this report for mines that were operated prior 

to 1905 should be considered as minimum values.

From 1905 to 1953 the total recorded yield of metals from the 

district was about 100,000 ounces of gold, 3,277,000 ounces of silver, 

250 tons of copper, 6,000 tons of lead, and 800 tons of zinc. The 

value of this ore at 1953 market prices was more than $13 million. 

Most of the ore came from the Lamartine-Great Western and the 

Preeland groups of veins.

CLASSIFICATION OF THE VEINS

Spurr, Garrey, and Ball (1908, p. 97-101) recognized two types of 

veins in the Georgetown quadrangle: silver-bearing veins without 

important amounts of gold (galena-blende ores) and gold-bearing 

veins with or without silver (pyritic ores). They also recognized 

that at places both types of ores occurred together and stated (p. 100) 

that "these phenomena were characteristically found on the borders 

between an area of predominantly gold-bearing veins and an area of 

silver-bearing veins." Bastin and Hill (1917, p. 105-114) recognized 

similar vein types in Gilpin County and referred to the mixture of 

the two types of ore as "composite ore." Bastin notes (Bastin and 

Hill, 1917, p. 113) that in the composite ore, veinlets of the galenasphalerite type sharply crosscut ore of the pyritic type. The general 

classification of vein type proposed by Spurr and Garrey and by 

Bastin and Hill is followed in this report. Two main types of ore are 

recognized: (1) pyrite-gold ore and (2) galena-sphalerite ore. A third 

type is composite ore, which occurs where ore of type (1) is crosscut 

by veinlets of ore of type (2).

The pyrite-gold ore consists predominantly of pyrite and auriferous 

pyrite, with subordinate amounts of chalcopyrite and tetrahedritetennantite and traces of galena and sphalerite. The gangue is quartz, 

and carbonate, if present, is usually siderite. This type of ore i& 

usually massive but locally is weakly banded in part. Pyrite-gold 

ore is characteristic of the Oneida, Freeland, and part of the Lone 

Tree veins.

The galena-sphalerite ore consists predominantly of galena, argentiferous galena, sphalerite, and pyrite with subordinate amounts of

1 U. S. Bureau of Mines, published with permission. /
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 75

chalcopyrite and tetrahedrite-tennantite. In most veins the gangue 

accompanying this type of ore is composed of about equal amounts 

of quartz and carbonate. The carbonate gangue is mostly rhodochrosite and calcite with smaller amounts of ankerite and dolomite. 

This type of ore is usually banded. Galena-sphalerite ore is characteristic of all veins in the district with the exception of the Oneida, 

Freeland, and Lone Tree veins.

The composite ore is in a transitional zone along a single vein 

between pyrite-gold and galena-sphalerite ore. A good exposure of a 

transition zone containing composite ore is along the Lamartine tunnel, 

in the area southwest of the Johnston shaft. The large scale observation of Spurr and Garrey on the geographic distribution of composite 

veins (see p. 74) appears to be a feature that can also be observed 

on a small scale.

The limits of the zones of composite ore are difficult to delineate, 

and, accordingly, the veins are classified into the two principal types 

(pi. 5); the data for some veins was insufficient to assign it to one of 

the principal vein types, so it is reported as "type not known." The 

data on which the division into the two principal vein types is based 

are given on pages 87-123. Along each vein composite ore occurs 

for varying distances in both directions from the point where pyritegold veins join galena-sphalerite veins.

Mineralization of the veins appears to have taken place in two 

stages; the first stage resulted in the deposition of pyrite-gold ores, 

and the second stage resulted in the deposition of galena-sphalerite 

ores. Both stages of mineralization deposited pyrite, chalcopyrite, 

tetrahedrite, galena, and sphalerite but in strikingly different ratios 

and generally with different gangue minerals. It seems reasonable to 

assume that the two stages of mineralization are closely related in 

time and that the second ore stage probably represents a continuation 

of a briefly interrupted process of mineralization.

Because of the close spatial relationship bstween the porphyry 

intrusive rocks and the Tertiary veins in the Front Range mineral 

belt, Levering and Goddard (1950, p. 75-76) have inferred that the 

Tertiary magmas were the source of the solutions that deposited the 

ores.

MINERALOGY OF THE VEINS

The most common primary metallic minerals in the veins are pyrite, 

auriferous pyrite, galena, argentiferous galena, sphalerite (both 

marmatite and resinous sphalerite), tetrahedrite-tennantite (copper 

antimony-arsenic sulfide), chalcopyrite, and free gold. Pyrite and 

auriferous pyrite form fine- to coarse-grained cubes and pyritohedrons 

in those parts of the veins that are not fractured or sheared. Most 

galena forms coarse grains and cubes, but the argentiferous variety

370788 56 4
76 GEOLOGY AND ORE DEPOSITS, COLORADO

appears to constitute fine-grained aggregates. Sphalerite occurs in 

medium- to coarse-grained masses and pods. Tetrahedrite-tennantite 

occurs in small veinlets and patches scattered through the ores. Sight 

identification of this mineral in the field is impossible as it has the 

steel-blue color and reddish-brown streak of hematite. When ore 

containing tetrahedrite-tennantite is drilled, the sludge from the 

drill hole is reddish; and, accordingly, some of the miners refer to 

tetrahedrite-tennantite bearing ore as "bloody ore." Chalcopyrite 

forms tiny blebs in sphalerite and occurs as veinlets and patches 

scattered through many of the ores. The occurrence of free gold was 

not observed.

Oxidized parts of the veins at places contain cerussite as an important lead ore and malachite, azurite, and coyellite as alteration products 

of tetrahedrite-tennantite and chalcopyrite. Yellow flakes of wulfenite 

(lead molybdate) are scattered through the ore and associated gouge 

in the oxidized part of the Diamond Mountain vein. Scattered 

flakes of torbernite (hydrous copper uranium phosphate) and autunite 

(hydrous calcium uranium phosphate) were observed in gouge or 

along fractures in several mines of the district, and needles or prisms 

of dumontite(?) (hydrous lead uranium phosphate) were noted along 

fractures in biotite-muscovite granite on the dump at the collar of 

the Ariadne shaft.

The gangue is predominantly quartz, either in the form of clear 

crystals or chalcedony. The chalcedonic quartz generally is tan to 

buff, but locally it is black because of inclusions of powdered pyrite 

or galena. Quartz commonly cements brecciated fragments of sulfide 

ore. Carbonates are common in some of the ores. Siderite is generally 

associated with pyrite-gold ores, and rhodochrosite, calcits, ankerite, 

and dolomite are associated with galena-sphalerite ores. Purple 

fluorite was observed with galena-sphalerite ore in specimens from 

the lower tunnel of the Little Johnie group of mines.

PABAGENESIS OF THE ORES 

PRIMARY ORB MINERALS

The paragenesis of the primary vein minerals is similar throughout 

the district; the generalized paragenetic sequence is given in figure 12.

The paragenetic sequence was determined from field observations 

and from the study of 74 polished surfaces and polished thin sections 

of ores from the district. The microscopic determination of paragenetic sequence was worked out using the criteria suggested by 

Bastin and others (1931).

The pyrite-gold type of ore is characterized by a coarse intergrowth 

of clear quartz and euhedral pyrite. Some of the pyrite contains tiny 

blebs of chalcopyrite, and a weathered vein of this material has a
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 77

Time

Pyrite-gold ore Galena-sphalerite ore

bo bo ton

 S «5 -» a a I * *» -* o o u

td td cd

V, V, V. ft, fa fa

Coarse vein quartz

Siderite (locally absent) >

Pyrite (commonly auriferous}'.

Chalcopyrite

Spahlerite

Tetrahedrite-tennantite

Galena

Fine-grained quartz

Rhodochrosite and (or) calcite

Chalceconic quartz

o

DOM 

W

i H i

11 11

FIGURE 12. Generalized paragegetifi, diagram for the primary vein minerals.

tarnish characteristic of chaleppyrite. Sphalerite (var. marmatite) 

usually containing small bleBs of chalcopyrite, fills vugs in the quartzcarbonate-pyrite vein material. At places tetrahedrite-tennantite 

or galena partly replaces the older vein minerals, particularly 

sphalerite.

Narrow galena-sphalerite veins typically are banded: a section from 

margin to center of a typical 4-inch vein contains half an inch of finegrained quartz and pyrite on the margin; the next layer inward 

consists of three-fourths of an inch of sphalerite (var. marmatite); 

aadthe center consists of galena. In many places rhodochrosibe and 

calcite form layers between, the- quartz-pyrite and the sphalerite. 

Chalcopyrite forms blebs along cleavage planes in sphalerite and tiny 

veinlets filling fractures in sphalerite. Tetrahedrite-tennantite occurs 

chiefly as veinlets replacing chalcopyrite or sphalerite, or as fracture 

fillings in sphalerite or gangue. Some "eutectoid" intergrowths of 

tetrahedrite-tennantite and galena occur in these ores. Galena commonly replaces all of the earlier sulfides as well as the gangue. Most 

of the ores show postgalena fracturing, and some, such as those in the
78 GEOLOGY AND ORE DEPOSITS, COLORADO

Turner mine, have been strongly brecciated. The fractures or 

breccia fragments are commonly cemented by chalcedonic quartz.

In the composite type of ore, the paragenetic sequence is a combination of the sequence of the pyrite-gold type of ore and the galenasphalerite type of ore. In the Freeland-Lamartine district, the composite ore is formed by galena-sphalerite ore filling fractures in 

pyrite-gold ore.

Many mines in the district show minor variations from the general 

mineralogy described above. The ore in the lower tunnel of the 

Little Johnie group of mines contains ankerite and fluorite; the lower 

workings of the Turner mine expose brecciated ore that contains 

fragments of light-amber sphalerite free from chalcopyrite blebs; and 

the New Era ore is noted for its abundance of chalcopyrite and lack 

of sphalerite. The overall pattern of mineral associations and their 

sequence of deposition is, however, strikingly consistent throughout 

the district. j

SECONDARY ORB JMINERAJLS

The secondary ore minerals in the district are considered to have no 

economic significance. Malachite, chilcanthite, and azurite, characteristic of the upper workings of the Qrazy Girl mine, occur in small 

quantities in most of the other mines] Wulfenite is scattered along 

fractures and in gouge along the mafgins of the east ward-trending 

vein of the Diamond Mountain mine.! Cerussite is characteristic of 

the ore from the upper workings of the Brazil mine (Spurr, Garrey, 

and Ball, 1908, p. 319). Barite has been reported (Spurr, Garrey, 

and Ball, 1908, p. 330) from the Harrisburg and Brighton mines.

Secondary uranium minerals, torbernite, autunite, and dumontite(?) 

occur in vugs or fractures or in gouge along several veins. Hydrous 

iron oxides from veins and from recent deposits on mine walls commonly show an unusual amount of radioactivity. In most of the 

radioactive material sampled, however, no discrete uranium minerals 

could be identified. None of the material assayed occurs in sufficient 

quantities to be commercial. Analyses of samples collected from 

mines and mine dumps in the district are given in table 9.
TABLE 9. Radioactivity of samples collected from mines 

[All samples are grab samples]

Mine 

no. 

(Pi. 5)

1

2

4

20

21

25

29

30

30

30

32

60

61

61

66

66

69

69

69

70

71

71

71

73

73

73

Mine name

Mammoth.... ___ _ .._. .........

do .

- do .

Old Stag. ..--.....-..... ............

Little Johnie middle tunnel. _____

 ..do...... ........... ................

Crazy Girl... .........................

_ .do ______ __ __ .. ..........

Belle Creole. ... . _ ..........

do .

do

Miller

. .do.. ..............................

do

. .do.............. .............

..do -

Material sampled

do

do ...

do

do

- - do .... . - .... .... .....

do

---. do . _ . _ .. . __ _ . _ _ 

do
80 GEOLOGY AND ORE DEPOSITS, COLORADO

ABNORMAL RADIOACTIVITY OP VEINS

Concentrations of radioactive materials in amounts greater than 

usual (or normal) is called abnormal radioactivity in this report. 

Every accessible mine in the district was examined for abnormal 

radioactivity; the dumps of inaccessible mines were traversed with a 

gamma scintillation counter. A previous report on results from the 

examination for radioactive materials (Wells and Harrison, 1954) in 

the Freeland-Lamartine district and the surrounding 20-square-mile 

area describes the distribution of abnormal radioactivity. In this 

report it is tentatively concluded that large areas containing only 

pyrite-gold veins are poor in uranium and that areas of pyrite-gold or 

galena-sphalerite veins containing chalcopyrite are more favorable 

sites in which to look for uranium deposits. Data from the district 

are insufficient to warrant a correlation between abnormal radioactivity and zoning of individual veins. The Diamond Mountain 

mine is the only mine in the district that might warrant a limited 

amount of exploration work to search for uranium ore.

The mines and mine dumps that contain radioactivity of at least 

twice the background on a rate meter with a 6-inch beta-gamma 

probe are listed in alphabetical order; the assay data have been 

condensed in table 9.

Ariadne. About 75 percent of the dump shows abnormal radioactivity. A sample of the fractured granite containing visible torbernite and dumontite(?) along the fractures assayed 0.039 percent 

equivalent uranium and 0.032 percent uranium.

Belle Creole. Two small areas (each about 1-foot square) of abnormal radioactivity were sampled in the mine. A sample (BC-1) 

taken near the winze on the split vein assayed 0.010 percent equivalent 

uranium and 0.002 percent uranium; a sample (BC-2) from the crosscut from the main tunnel assayed 0.037 percent equivalent uranium 

and 0.033 percent uranium. About 10 percent of the dump at the 

shaft southwest of the tunnel portal (pi. 5) is abnormally radioactive. 

A grab sample of limonitic vein material from this dump assayed 

0.006 percent equivalent uranium and 0.002 percent uranium.

Bell of the West. The two stronger veins exposed in drifts have 

abnormal radioactivity of almost twice background. As these 

anomalies were so slight, no samples were collected for assay.

Brazil. Radioactive material was found on the dumps of the lower 

adit and shaft. A grab sample from the lower adit dump assayed 

0.040 percent equivalent uranium and 0.038 percent uranium, and a 

grab sample from the shaft dump assayed 0.013 percent equivalent 

uranium and 0.008 percent uranium. The samples consisted of 

limonitic vein material.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 81

Crazy Girl. One sample of radioactive vein material was collected 

from the hanging wall of the vein on the second level of the mine. 

The material assayed 0.033 percent equivalent uranium and 0.026 

percent uranium. A sample of alaskite porphyry from the east end 

of the second level assayed 0.011 percent equivalent uranium and 

0.006 percent uranium.

Diamond Mountain. A sample of mill concentrate of ore from the 

lower stope on the ore shoot near the breast of the workings assayed 

0.078 percent equivalent uranium and 0.041 percent uranium. A 

grab sample (DM-1) of the gouge on the eastward-trending vein near 

the breast of the workings in the lower tunnel assayed 0.16 percent 

equivalent uranium and 0.046 percent uranium; a grab sample (DM-2) 

of gouge from and split on the sublevel assayed 0.30 percent equivalent 

uranium and 0.35 percent uranium. The uranium mineral or minerals 

could not be separated from the gouge for identification.

Falcon. About 10 percent of the surface of the dump contained 

abnormal radioactivity, and one grab sample of limonitic vein material 

from the dump of the Falcon tunnel assayed 0.004 percent equivalent 

uranium.

Harrisburg. One small area of weathered vein material on the 

Harrisburg dumps is abnormally radioactive. A grab sample of the 

radioactive material assayed 0.015 percent equivalent uranium and 

0.013 percent uranium.

Lamartine. Abnormal radioactivity was noted on the Lamartine 

tunnel level and on the Old Stag tunnel level. In the Lamartine 

tunnel, intermittent abnormal radioactivity was noted in the area 

600 to 1,660 feet from the portal. Three samples for assay were collected in this area. Sample La-1 consists of pyritic vein material 

and assayed 0.007 percent equivalent uranium and 0.002 percent 

uranium. Sample La-2 composed of- limonitic material (about 

one-fourth inch thick when sampled), which was being deposited on the 

walls of the tunnel by water dripping from an old gold stope, gave 

0.083 percent equivalent uranium and 0.15 percent uranium. Sample 

La-3, gouge from the footwall of a cross vein, was collected in an old 

drift about 25 feet above the Lamartine tunnel and gave 0.12 percent 

equivalent and 0.11 percent uranium.

In the Old Stag tunnel abnormal radioactivity resulting from radon 

was noted near the portal and gradually increased in intensity toward 

the breast of the workings. No specific area of abnormal radioactivity 

could be isolated. A grab sample of limonitic material (OS-1, pi. 4) 

from the tunnel walls assayed 0.007 percent equivalent uranium and 

0.002 percent uranium.

Little Johnie group. One small area 2 feet square of abnormal radioactivity was noted in the lower tunnel. The area is in one of the gouge
82 GEOLOGY AND ORE DEPOSITS, COLORADO

leads about 360 feet from the portal. A grab sample (358-2) of the 

gouge assayed 0.017 percent equivalent uranium and 0.013 percent 

uranium.

In the middle tunnel, two local areas of abnormal radioactivity 

were noted. Both of these areas are near the west end of the main 

drift. A grab sample from a thin gouge lead (357-1) assayed 0.037 

percent equivalent uranium and 0.033 percent uranium. A grab 

sample from one of the eastward-trending veins (357-2) assayed 

0.002 percent uranium.

No abnormal radioactivity was noted in the upper tunnel.

Lone Tree. Slightly anomalous radioactivity was noted on the 

dumps at the Lone Tree and Lone Tree Extension shafts. The 

anomaly was noted over most of these dumps and was partly the result of fragments of bostonite. Radioactive material other than that 

in the dike rock could not be isolated well enough to sample.

Some of the vein material on the dump at the Lone Tree tunnel 

portal also is abnormally radioactive. A grab sample of limonitic 

vein material had assay values of 0.006 percent equivalent uranium 

and 0.005 percent uranium.

Mammoth. Abnormal radioactivity on the order of twice background was noted on the dump of the Mammoth shaft. A sample 

of limonitic vein material assayed 0.003 percent equivalent uranium.

Miller. Three small areas, each about 2 feet square, of abnormal 

radioactivity in composite vein material were noted in the mine. 

Grab samples (Mi-1, Mi-2, and Mi-3) were collected and assayed 

0.006, 0.009, and 0.014 percent equivalent uranium and 0.003, 0.004, 

and 0.001 percent uranium, respectively. A few scattered flakes of 

torbernite were observed in the samples.

Poor Man. A grab sample of limonitic vein material taken from 

the dump assayed 0.028 percent equivalent uranium and 0.023 

percent uranium.

WALL-BOCK ALTERATION

The country rock found within the lode has been broken, silicified, 

and bleached. The feldspars are altered to sericite, and the biotite 

is bleached and partly pyritized. Minor amounts of pyrite are 

scattered through the altered feldspars. The biotite-rich gneisses 

commonly have been bleached to white or dull-greenish-gray sericiterich rocks that have layers of sericite-pyrite instead of biotite.

Outside of the lode, beyond the smooth footwall and hanging wall, 

the alteration is less intense, and usually visible alteration extends 

only a foot or less into the wall rock. The alteration along minor 

fractures, which are common for several feet beyond the lode zone,
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 83

usually is only an inch or less wide; the same alteration minerals are 

formed here as within the lode.

Most of the wall rocks found in the district contain abundant silica 

and iron in the form of quartz, feldspar, biotite, and magnetite. It 

seems reasonable to believe that part of the quartz and pyrite found in 

the veins has been derived by metasomatic processes from the wall 

rock. Many small fractures in wall rock outside of the lode zone contain traces of quartz and pyrite regardless of whether the fracture is 

associated with the pyrite-gold or galena-sphalerite type of ore. These 

minor traces of quartz and pyrite in small fractures in the wall rock 

could well have been derived from the wall rock by metasomatic 

processes which added, at least, a small amount of sulfur.

LOCALIZATION OF THE QBE BODIES

Most of the ore bodies in the Freeland-Lamartine district occur as 

shoots, lenses, or pods that are localized principally at vein intersections, changes in strike or dip of veins, or by a combination of 

these factors. At one locality an ore body is present at a deflection in 

the vein caused by the change in strike of a fault through a rock type 

of different competency. A chemical control related to the type of 

wall rock apparently has not been a factor in the deposition of the ores.

Vein intersections. Vein intersections are the loci for ore bodies in 

several mines. In the New Era mine some of the richest ore was found" 

at the junctions of the Flat, Oldbury, and Great Western veins. 

Spurr, Garry, and Ball (1908, p. 318) attributed localization of the 

ore body near the Larnartine shaft to the intersection of the Oneida 

and Lamartine veins.

At several localities horses in the veins occurring between vein 

splits are enriched by stringers of ore as well as by thickening of the 

ore at the perimeter of the horse.

Deflections in strike of veins. The ore bodies in the Turner and 

Old Stag mines appear to be related to changes in strike along the vein. 

At the Turner mine the only ore shoot in the mine is located on a very 

prominent strike change. Dip control in conjunction with strike control is apparent in the Turner mine, and the same may be true for the 

ore body that was mined above the Old Stag tunnel. In general, 

strike control is less evident than dip control in the mines of the 

district.

Deflections in dip of veins.- Many ore bodies in the district clearly 

are localized by changes in dip along a vein. Ore bodies along veins 

that have a relatively uniform strike and little change in dip along the 

direction of strike are consistently in the steeper part of the veins. 

Accordingly, the writers have concluded that the hanging wall of the 

faults in the district moved down relative to the footwall.
84 GEOLOGY AND ORE DEPOSITS, COLORADO

Miners at the Lamartine and Crazy Girl mines report that the ore 

is always thicker on the steeper parts of the vein. The main Freeland 

ore body appears to be definitely related to a prominent change in dip 

(see discussion on page 100), and the widest part of the ore in the 

Turner mine is near the second level, where the dip of the vein is steeper 

than elsewhere. Even in small detail, dip control is prominent; in an 

old stope at the east end of the drift in the middle tunnel of the Little 

Johnie group of mines, the flat part of one of the veins contains % 

inch of ore, but the steep part contains 1% inches of ore. This 

change from flat to steep to flat dip occurs within a length of 12 inches 

along the vein.

The control of ore shoots by deflections in strike and dip has been 

discussed at some length by Newhouse (1940). The writers wish to 

call attention to the fact that both principal types of ore have been 

localized by deflections in strike and dip. Such features occur on all 

three sets of fractures in the district. This detailed structural control 

along all parts of the long cymoid-shaped fissures indicates, as suggested by Newhouse (1940), that the long cymoids are not simply 

large examples of the small cymoids that have helped localize the ore 

bodies. The long cymoids have been opened all along their length at 

some time during the formation of the fracture system and the deposition of the ore. Offsets of steeply dipping pre-Cambrian rock units and 

Tertiary dikes indicate that the strike-slip component of movement on 

the faults in the district was northwest side to the northeast; a slight 

dip-slip component accompanied the strike-slip movement. As the 

ends of the large cymoids have about the same dip as the central segments, such movement should have its principal bearing area along 

the north-northeast fault surfaces and should form openings along the 

east-northeast and east fractures. The north-northeast fractures, 

however, are neither barren nor less strongly mineralized than the 

other fractures. This information considered in conjunction with the 

data previously presented on the sequence of fracturing suggests that 

the long cymoids are not the result of one simple shear but represent a 

series of breaks, each fracture in the series having been mineralized at 

the time of opening. The ore deposits along the large cymoids were 

localized by small changes in strike and dip that created openings along 

 each succeeding fracture set as it was formed.

Fault deflections due to rock type. One ore body in the district appears to have been localized by the deflection of a fault caused by a 

difference in competency of two rock types traversed by the fault. 

Harrington's detailed map of part of the Diamond Mountain mine 

«hows this deflection clearly. The ore shoot along the fault is confined to a bostonite dike in biotite-muscovite granite. The deflection 

of the fault is particularly evident on the lower tunnel level where a
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 85

weakly mineralized fracture trending eastward is deflected as it enters 

the dike. The fracture trends east-northeasterly through the dike and 

contains minable ore.

Newhouse (1942) has summarized observations of several geologists 

on this type of fault deflection. According to theory, the fault deflection in the Diamond Mountain mine should result from strike-slip 

movement on the fault in which the northwest block moved to the 

northeast relative to the southeast block if the dike is less competent 

than the granite. If the dike is more competent than the granite, then 

the deflection is that expected from movement on the fault in which the 

northwest block moved southwest relative to the southeast block, the 

reverse of the movement on the other faults in the district. The 

answer to this enigma could not be obtained because, unfortunately, 

the dike does not appear to be offset.

PERSISTENCE OF QBE WITH DEPTH

The deepest mine workings in the district are along the McClelland 

tunnel level of the Freeland mine. Ore was mined along the Freeland 

and Shaffer veins from several small stopes above the tujinel, and a 

shallow winze is reported to have reached ore of about the same grade 

as that found in these nearby stopes. Accordingly, ore has been found 

along the Freeland vein over a vertical distance of about 1,600 feet, 

between an altitude of 7,900 and 9,500 feet. This is equivalent to 

about 2,700 feet measured in the plane of the vein. Ore has been 

found in the mine workings along the Lamartine-Great Western group 

of veins at altitudes from 10,500 feet down to 8,900 feet.

None of the mines has been explored sufficiently to establish a 

bottom for the effective depth of mineralization. The effective height 

of mineralization appears to be at an altitude of about 10,500 feet. 

Although several shafts have been sunk on veins at altitudes above 

10,500 feet, none of the workings have reached ore above that altitude. 

The Lamartine ore body was found at a depth of 100 feet below the 

collar of the shaft, which is at an altitude of 10,600 feet. The ore shoot 

in the Diamond Mountain mine pinches out before it reaches the 

surface, which has an altitude of about 10,450 feet over the apex of the 

ore shoot.

In general, the values in the ore decrease with depth. In the Lamartine ore body, which was a blind ore body inasmuch as it did not 

reach the surface and had not been affected by supergene enrichment, 

the best values were near the top of the ore shoot.

HYPO GENE ZONING OF THE QBE DEPOSITS

The veins of the Freeland-Lamartine district show zoning confined 

to a single cymoid vein. The geographic pattern of this zoning is
86 GEOLOGY AND ORE DEPOSITS, COLORADO

rectilinear along the trace of the vein instead of subcircular and does 

not involve several veins as is common in many districts showing the 

classic "onionskin" type of zoning described by Emmons (1940, p. 

194-196) or as found at Butte.

The zoning in the district is believed to be the result of a combination in space of two processes, a sequence of fracturing and a sequence 

of mineralization; the two sequences occurred essentially contemporaneously. The first, and hotter, solutions deposited ore of the pyritegold type in the earliest set of fractures which formed approximately 

parallel to axial planes in the pre-Cambrian bedrock. This first 

stage of ore-bearing solutions probably deposited large bodies of 

pyrite-gold ore below and small (?) bodies of galena-sphalerite ore 

above. As the process of fracturing continued, younger fractures 

(first east-northeast and finally east) formed at the ends of the older 

fractures. Solutions that were slightly later, and cooler, than those 

that deposited the pyrite-gold ore deposited ore of the galena-sphalerite 

type in the younger fractures. The composite type of ore is found 

where younger fractures, containing minerals deposited by the cooler 

solutions, cut through the ends of the older pyrite-gold type of veins. 

The ideal geographic expression of this combination of processes is a 

long, cymoid-shaped vein containing pyrite-gold ore in the center, 

composite ore along the curving part, and galena-sphalerite ore at the 

extremities.

Effect of topography. The present geographic pattern of any zonal 

distribution of ores is related to the local topography. As the effective height of mineralization in the Freeland-Lamartine district 

extended about 1,000 feet above the average altitude of the present 

topography, the geographic pattern of any original zonal arrangement 

of the ores would have been modified by erosion to the present surface. This modified pattern of the distribution of the two main ore 

types is shown in plate 5 and is described below.

Longitudinal zoning. Three complete cymoid-shaped vein systems 

occur in the Freeland-Lamartine district; namely, the Freeland, the 

Lamartine-Great Western, and the Lone Tree. Zoning along the 

strike of the cymoids is apparent from the geographic distribution 

of the ores as shown in plate 5. Veins of the pyrite-gold type are 

found only on north-northeast segments of the long cymoids, and the 

ends of the cymoids contain the galena-sphalerite ore. In the Freeland group of veins this pattern of longitudinal zoning is nearly perfect. Along the Lamartine-Great Western cymoid the pattern is 

well formed but along the Lone Tree cymoid the pattern is very 

weakly formed. The changes in the degree of formation are probably 

related to the effect of topography on an original depth zoning.

Vertical zoning. Limited information from the two largest mines,
FREELAND-LAMARTINE DIS^RICST, CLEAK CREEK COUNTY 87

the Freeland and the Lamartine, suggests the presence of vertical 

zoning in these mines. On the north-northeast Freeland vein galena 

was found in bunches near the surface, but none was found at depth 

with the pyrite-gold ore. Some good zinc ore was reported from the 

near surface stopes on the north-northeast Oneida vein, but only 

traces of sphalerite are present in the lower workings of the part of 

the mine that contained pyrite-gold ore. A cautious inference drawn 

from these data is that the shallow workings of the Lone Tree mine 

have cut only the top of the pyrite-gold zone, and that the poor 

agreement with the ideal pattern is due to insufficient erosion of a 

vertically zoned vein.

X^is vertical zoning is related to the longitudinal zoning in the 

fracture systems. The pyrite-gold veins are in the oldest part of 

the cymoids, the north-northeast segments, and these ores appear to 

be vertically zoned; the lower part of the ore is of the pyrite-gold 

type and the upper part of the ore is of the galena-sphalerite type. 

In addition, the pyrite-gold ores are locally cut by galena-sphalerite 

ores at the margins of the pyrite-gold zones along the veins. In 

theory the younger galena-sphalerite ores could also cut the older 

galena-sphalerite ores deposited as the outer zone by the first stage 

of mineralization. Although this feature was not seen in the accessible 

mines of the district, such a feature might be overlooked. The most 

productive galena-sphalerite ores, however, have been found in the 

east-northeastward- and eastward-trending fracture systems.

DESCRIPTION OF MINES

Because many of the mines in the district are now inaccessible, 

much of the underground geology in the district was not available 

for study by the writers. Information on the underground workings 

of inaccessible mines was obtained from several sources and is acknowledged on the appropriate maps.

The mining terms used in this report are those that are in general 

usage in the district. Any nearly horizontal passageway from the 

surface i& called a tunnel in the district; as none of these passageways 

extend completely through a hill, they are preferably called adits.

ARIADNE MINE

The Ariadne mine is on the northeast slope of Alps Mountain 

(pi. 5). The collar of the shaft is at an altitude of 9,820 feet.

Because in 1952 the shaft was almost entirely filled with water, 

it was not possible to determine accurately the depth and extent of 

the mine. However, the quantity of broken rock on the dump 

indicates about 350 feet of underground workings.
88 GEOLOGY AND ORE DEPOSITS, COLORADO

The rock on the dump is highly sheared and fractured biotitemuscovite granite and associated pegmatite. The vein seen at the 

collar of the shaft strikes N. 50° E. and dips 72° N., and it may be 

correlated as the northeasterly extension of the Miller vein. (See 

pi. 5.) Vein material on the dump includes quartz, limonite, torbernite, and dumoiitite(?). Disseminated crystals of torbernite and 

dumontite(?) thinly coat some of the fractures in the granite, and 

quartz and limonite fill vugs in* the jgjp&nite.

No record of production from the Ariadne mine could be found.

AVALANCHE MINE

The portal of the Avalanche tunnel, at an altitude of 9,480 feet, 

lies in a small gulch about 4,800 feet N. 60° W. from Freeland (pi. 5). 

A caved shaft 110 feet east from the tunnel portal is on the vein. 

Only the 240-foot tunnel, driven westward along the vein (fig. 13), 

is now accessible. A water-filled winze, 85 feet from the portal, and 

two small stopes 15 and 20 fe$t high-near the winze are inaccessible.

Granite gneiss and pegmatite, migmatite, and biotite-mustfovite 

granite are exposed in the tunnel. These rocks have been folded 

into a series of small anticlines and synclines that plunge about 30° 

to the south.

2-foot silicified zone with dissemlnated pyrite; 2 in. of 

chalcedonic quartz; 3 in. of

galena, ^pMerite, and pyrjte in swingers

8 in. of disseminated 

pyrite in quartz

2 in. of galena, pyrite, 

sphalerite, and quartz

Datum is mean sea level 

EXPLANATION

Biolite-muscovile granite

Granite gneiss and 

pegmatite

Contact, dashed where inferred

Strike and dip of foliation 

and plunge of lineation

Vein, snowing dip; dashed where 

approximately located

go 

Vertical vein

!ZJ 

Head of winze 

Geology by J. 0. Wells, 1952 

FIGURE 13. Geologic map of the Avalanche tunnel.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 89

The vein in the accessible drift trends from N. 84° W. to N. 70° E. 

and has an average strike of N. 82° E; the dip is about 84° S. The 

width ranges from % inch to 2 feet; the widest part is 110 feet from the 

portal. Disseminated quartz and pyrite occur along the length of 

the vein. In the area between the stopes, stringers of galena, 

sphalerite, pyrite, and quartz cut the disseminated quartz-pyrite 

vein. Some chalcedonic quartz occurs in the widest part of the vein.

The vein is widest at changes in strike and at vein intersections 

(fig. 15). No evidence is available to determine what influence, if 

any, changes in dip might have.

U. S. Bureau of Mines records show that between 1910 and 1915, 

32 tons of ore was shipped from the Avalanche mine. The ore 

yielded a per ton average of 0.5 ounce of gold, 5.0 ounces of silver, and 

25 percent lead.

BALTIMORE MINE

The portal of the Baltimore tunnel, at an altitude of 10,166 feet, 

is about 2,900 feet N. 40° W. from the western peak of Alps Mountain 

(pi. 5). The Baltimore mine consists of a short tunnel and a winze 

that connects with two short drifts (fig. 14). The tunnel was found 

caved at the portal.

The tunnel was driven on a vein that strikes N. 65° E. and dips 

about 60° NW. (fig. 14). The more northeastward-trending vein 

that cuts the main vein about 128 feet from the portal probably 

is the Lone Tree vein.

SECTION THROUGH WINZE

After map by C. L. Harrington.1939

50

III.

FIGURE 14. Plan and section of the Baltimore mine.
90 GEOLOGY AND ORE DEPOSITS, COLORADO

The rock on the dump indicates that the mine workings are mostly 

in granite gneiss and pegmatite. The vein material on the dump 

consists of pyrite, chalcopyrite, galena, and sphalerite in a quartz 

gangue.

No record of production from the Baltimore mine could be found.

BELLE CREOLE TUNNEL

The Belle Creole tunnel is about 2,000 feet N. 20° E. of the western 

peak of Alps Mountain (pi. 5). The portal is at an altitude of 9,800 

feet. The tunnel is 356 feet long; 80 feet from the portal a drift follows 

a vein split for 140 feet (fig. 15). A winze has been sunk on the branch 

vein about 80 feet from the junction with the main vein. As the 

winze was full of water in 1952, the extent of the winze was not 

observed. No extensive stoping has been done in this mine. A small 

shaft, 300 feet southwest of the tunnel portal, probably is on the same 

vein, but the shaft does not connect with the workings on the tunnel 

level.

The tunnel is principally in biotite-muscovite granite, but small 

patches of amphibolite, migmatite, and granite gneiss and pegmatite 

are present at the extremities of the mine workings.

Maximum of 1 in.

of composite ore..-

2-foot brecciated granite zone

with stringers and thin veins

totaling a maximum of 2 in.

of quartz-pyrite-chalcopyritesphalerite-galena ore

PORTAL

Elev 9800 ft 

Overburden 

Timbered>xT EXPLANATION

Biotite-muscovite granite

in. of crushed granite with disseminated 

pyrite

Sample BC-1

 3 in. of disseminated quartz-pyrite 

ore. Some disseminated galena 

and sphalerite

Sample BC-2

50 150 Feet

Datum is mean sea level

Amphibolite

Contact, dashed 

where inferred

Strike and dip of foliation

Vein, showing dip; dashed 

where inferred

Foot of raise

0 

Head of raise

Geology by J. E. Harrison and J. D. Wells, 1952 

FIGURE 15. Geologic map of the Belle Creole tunnel.
91

The main vein strikes about N. 59° E. and dips on the average 

65° NW.; probably, it is the western extension of the Crazy Girl vein 

(pi. 5). The vein that splits from the main vein, 80 feet from the 

portal, strikes about N. 43° E. and dips about 85° NW. The winze 

was put down on the split vein where it reached a maximum width 

of 10 inches of crushed granite and disseminated pyrite. The vein 

consists of pyrite, chalcopyrite, chalcocite, galena, and sphalerite in a 

quartz gangue. Several small horses occur along the main vein 

(fig. 15), and they appear to have influenced localization of the ore. 

The maximum thickness of ore observed, however, was only 2 inches.

No record of production for the Belle Creole could be found, but 

indications are that little ore has been produced from this mine.

BELL OF THE WEST TUNNEL

The portal of the Bell of the West tunnel, at an altitude of 9,280 

feet, is about 2,000 feet southwest up the valley from Freeland (pi. 5). 

The mine workings consist of a crosscut tunnel that trends N. 63° W. 

for the first 345 feet and then N. 13° W. for 177 feet to the breast 

(fig. 16). Two short drifts have been driven southwesterly at distances of 73 feet and 245 feet from the portal.

The tunnel cuts across the general northeasterly trend of foliation 

in the wall rocks, and exposes 20- to 80-foot layers of biotite-quartz 

gneiss, migmatite, amphibolite, and granite gneiss and a small body 

of biotite-muscovite granite.

Several small, weakly mineralized veins, most of which are thin 

streaks of gouge that contain a small amount of pyrite, are cut by the 

tunnel. Two of the stronger veins contain thin stringers of pyrite, 

chalcopyrite, and galena in a quartz gangue. Both of these veins 

have been drifted on for about 65 feet, but no stoping has been done 

along them. The first of the stronger veins nearer the portal strikes 

N. 54° E. and dips on the average 81° NW. The second strikes 

N. 37° E. and dips about 62° NW.; this vein probably is a northeast 

extension of the Silver Link vein (pi. 5).

As there are no stopes in the mine, there probably has been no 

production of ore.

BRAZIL MINE

The Brazil mine is near the head of Trail Creek with the lower 

tunnel 150 feet north of the stream at an altitude of 10,084 feet (pi. 5).

The workings, all caved at the surface, consist of three adits and 

two shafts. The main shaft lies northwest of the lower adit at an 

altitude of 10,351 feet. The other shaft, which was sunk on the vein, 

is 120 feet northwest from the lower adit. The other two adits, one 

on the vein, the other to the south of it, are at altitudes of 10,198 and

370788 56 5
92 GEOLOGY AND ORE DEPOSITS, COLORADO

EXPLANATION

Contact, showing dip; dashed 

where inferred

Strike and dip of foliation

Strike and dip of foliation 

and plunge of lineation

Strike of vertical foliation

Plunge of minor anticline

___ ^76

Vein, showing dip; dashed 

where inferred

PORTAL 

OF ADIT

Elev 9280 ft

SILVER LINK!?) VEIN 

50 0

Datum is mean sea level

Geology by J, E. Harrison, 1952 

FIGURE 16. Geologic map of the Bell of the West tunnel.

10,205 feet respectively. Spurr, Garrey, and Ball (1908, p. 319) 

reported that more than 800 feet of the lower adit was open at the 

time of their visit and that there was a 150-foot stope on the N. 85° W. 

part of the vein.

At the surface, the mine area is in granite gneiss and pegmatite, 

and this is the only rock type found on the dump. Vein minerals 

identified from the dumps include galena, sphalerite, chalcopyrite, 

pyrite, quartz, and barite (?). The general strike of the vein is 

N. 75° W., but it ranges from N. 55° W. to N. 85° W., and the dip 

ranges from 50° to 60° NE. (Spurr, Garrey, and Ball, 1908, p. 319).

Production records of the U. S. Bureau of Mines indicate that the 

Brazil mine was worked from 1904 to 1905, from 1916 to 1917, and 

in 1920, 1941, and 1942. During the different periods of operation 

a total of 88 tons of ore was shipped. The ore contained a total of 

28.5 ounces of gold, 2,193 ounces of silver, 5 pounds of copper, 204 

pounds of lead, and 210 pounds of zinc.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 93 

BRIGHTON MINE

The collar of the Brighton shaft is at an altitude of 9,730 feet and 

is about 3,200 feet N. 5° W. of western peak of Alps Mountain (pi. 5).

The Brighton mine was worked almost continually from 1903 to 

1909. The mine was worked for a short tune during 1917 and again 

during 1927. According to the records of the U. S. Bureau of Mines 

about 4,085 tons of ore has been shipped from the mine. This ore 

yielded a total of 596 ounces of gold, 25,387 ounces of silver, 77,803 

pounds of copper, 1,041,824 pounds of lead, and 7,757 pounds of zinc.

The Brighton shaft is caved at the collar, and none of the mine 

is accessible. Accordingly, the following information has been taken 

from Spurr, Garrey, and Ball (1908, p. 325-332).

The Brighton vein was worked from an inclined shaft that connects 

with drifts on five levels (fig. 17). The vein, which has an average 

strike of N. 45° E. and an average dip of about 31° N., is probably 

part of the Freeland vein system. The vein material is mostly galena 

with some sphalerite, chalcopyrite, and pyrite in a quartz and carbonate gangue.

Work done since the report of Spurr, Garrey, and Ball (1908) 

suggests that the Brighton vein joins the Split vein hi the Freeland 

mine at a point several hundred feet west of the junction between the 

Split and the Freeland Extension veins (fig. 10).

CRAZY GIRL MINE

The Crazy Girl mine consists of a shaft that connects with drifts 

on three levels, a tunnel that crosscuts into the first level, and the 

Baby Eddy tunnel, which was driven to connect with the third level 

but was never completed (fig. 18). The collar of the Crazy Girl 

shaft is about 2,800 feet N. 40° E. of the western peak of Alps Mountain, at an altitude of 9,700 feet (pi. 5). The portal of the Crazy Girl 

tunnel is in a small gulch, about 380 feet N. 37° W. of the collar of 

the shaft. The portal of the Baby Eddy tunnel is about 800 feet north 

of the Crazy Girl tunnel portal.

At the time of the writers' visit the mine was under lease to K. J. 

King and J. M. East of Boulder, Colo. Ore'was being taken from a 

stope at the east end of the second level. Because of a sharp drop in 

the market value of lead, the mine was shut down almost overnight in 

July 1952. While the air was still good the writers were able to make 

a plan of the accessible parts of the mine, but a geologic map could 

not be completed.

Production records in the files of the U. S. Bureau of Mines for the 

years 1902 to 1952 indicate that the mine was operated intermittently 

during these years, and a total of 1,928 tons of ore was shipped. This
94 GEOLOGY AND ORE DEPOSITS, COLORADO

HARRISBURG SHAFTL

iECTION THROUGH THE HARRISBURG SHAFT

^BRIGHTON SHAFT

Elev9730ft

EXPLANATION

a

Shaft at surface

n

Shaft going above and below level

K 

Bottom of shaft

a 

Head of raise or winze

H

Foot of raise or winze

SECTION THROUGH THE BRIGHTON SHAFT

lap loaned by C L Hatrington. dated 1906 Se

FIGUEE 17. Plans and sections of the Brighton and Harrisburg mines.

i byj. E. Harrlson, 1953

ore yielded 231 ounces of gold, 6,885 ounces of silver, 4,591 pounds of 

copper, 412,818 pounds of lead, and 73,881 pounds of zinc. A settlement sheet loaned by Mr. East shows that one shipment of 7.08 tons 

of ore made in 1952 yielded 2.76 ounces of gold, 90.7 ounces of silver, 

78 pounds of copper, 4,548 pounds of lead, and 1,266 pounds of zinc.4

* Published with permission of sublessee, J. F. James.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 95

PORTAL 

BABY EDDY TUNNEL

Elev 9341 ft

-94001

PORTAL 

CRAZY GIRL TUNNEL

Elev 9560 ft

L CRAZY GIRL SHAFT 

Elev 9700 ft

Base partly from maps loaned by C. L. Harrington 

100

Map of accessible parts of mine by J. E.

Harrison and A. A. Drake, 1952 ' 

300 Feet

FIGUEE 18. Plau and section of the Crazy Girl mine.
96 GEOLOGY AND ORE DEPOSITS, COLORADO

The wall rock in the accessible part of the mine consists principally 

of biotite-muscovite granite and alaskite porphyry, with some biotitequartz gneiss and migmatite. The dump of the Baby Eddy tunnel 

indicates that granite gneiss and pegmatite was the principal rock 

type found in the tunnel.

The Crazy Girl vein strikes N. 50°-80° E. and dips about 70° 

NW.; its probable continuation to the northeast is seen in the Yankee 

Girl shaft and to the southwest in the Belle Creole tunnel (pi. 5). 

Two veins were found in the Baby Eddy tunnel. Both of these veins 

trend about N. 50° E. and dip 40°-50° NW. The vein nearest the 

portal of the Baby Eddy tunnel cannot be traced on the surface; the 

vein nearer the breast of the workings is probably the Alabama vein 

which on the surface can be traced to the northeast.

The Crazy Girl vein contains pyrite, chalcopyrite, tetrahedrite, 

galena, and sphalerite as the principal ore minerals. The upper levels 

of the workings also contain malachite and azurite. The gangue is 

principally quartz and some carbonate.

The main ore shoot in the mine appears to be confined to the more 

eastward-trending part of the vein, and according to the miners, the 

ore is thicker on the steep parts of the vein than on the flat parts. 

As the eastward-trending part of the vein is slightly irregular and the 

ore pinches and swells, the ore has been found in a series of lenses 

or pods. In more recent years the mine has been operated at times 

when the price of the metals would allow mining of the thinner ore 

between richer pods.

So far as known, stoping has not been done between the second and 

third levels of the mine.

DIAMOND MOUNTAIN (LANAGAN) MINE

The Diamond Mountain mine is on the north shoulder of Alps 

Mountain (pi. 5). The portal of the upper tunnel is at an altitude of 

10,312 feet, and the portal of the lower tunnel is at an altitude of 

10,178 feet.

The upper tunnel is about 510 feet in length and is along a thin vein 

that trends S. 46° W. (pi. 6). About 300 feet from the portal a cross 

vein has been stoped for about 60 feet. The first 430 feet of the lower 

tunnel is a crosscut; at this point the tunnel turns S. 46° W. and 

extends about 350 feet along the vein. Two small stopes connect 

the upper and lower tunnels, and a shallow winze and short sublevel 

drift are present near the breast of the lower tunnel workings. The 

stopes were inaccessible in 1952, but a plan of the stope near the 

breast of the workings was loaned by C. L. Harrington and is shown 

in plate 6.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 97

Both drifts follow a bostonite dike that has been intruded into 

biotite-muscovite granite, which contains local layers and bodies of 

pegmatite. The dike is present discontinuously on the walls of the 

upper tunnel, and, although it is principally on the footwall, locally 

it is in the hanging wall. The same dike is present in the lower drift, 

generally occurring in the hanging wall, but 80 feet from the breast 

of the workings it is in the footwall. Both the granite and the bostonite locally have been sheared and brecciated along the vein.

Both a footwall and a hanging wall vein occur along the bostonite 

dike. These veins are approximately parallel to the dike, although 

locally they are separated from the dike by several feet of granite. 

The veins and the dike have an average strike of N. 46° E. and a dip 

of 57° to 68° N. An eastward-trending vein that dips about 70° N. 

cuts through the dike near the breast of the workings in both tunnels. 

Where metallized, the veins consist of pyrite, auriferous pyrite, 

chalcopyrite, tetrahedrite-tennantite, galena, sphalerite, and wulfenite 

in a quartz and carbonate gangue. The presence of wulfenite suggests that the ore body exposed in the workings is in the oxidized zone.

Spurr, Garrey, and Ball (1908, p. 333-334) gave a brief discussion 

of this mine which was then called the Lanagan mine. At the time 

of the visit by Spurr and Garrey, only the upper tunnel had been 

driven. Spurr and Garrey concluded that the ore body then being 

mined had been deposited at the junction of two intersecting veins. 

C. L. Harrington (written communication, 1941) later concluded 

from an examination of a larger amount of workings that the ore shoot 

in the mine was deposited in the bostonite dike on a cross vein (pi. 6); 

the writers' study substantiates this conclusion.

The only productive ore shoot in the mine occurs where the eastward-trending vein cuts through the dike (pi. 6). The ore shoot 

plunges about 55° N. 5° E. Harrington's detailed map (pi. 6) shows 

that it decreases in width and thickness from the upper to the lower 

tunnel levels. In the upper tunnel the ore shoot has a stope length 

of about 60 feet and has a maximum thickness of about 30 inches; 

in the lower tunnel the ore shoot has a stope length of about 40 feet 

and has a maximum thickness of 12 inches. The ore shoot appears 

to be a lens-shaped body confined to the bostonite dike.

Spurr, Garrey, and Ball (1908, p. 334) gave the value of the ore in 

the upper stope which, when recalculated at 1953 market for gold, 

silver, and lead (average), is $216 per ton. Company assays indicate 

that the value of the ore in the lower stope was about $180 per ton.5 

Most of the production has been in silver (some assays show as much 

as 296 ounces per ton), and the upper stope also averaged slightly 

more than 2 ounces of gold per ton. The ore shoot has been very low

5 Published with permission.
98 GEOLOGY AND ORE DEPOSITS, COLORADO

in base metals and has averaged only about 1 percent total lead, 

zinc, and copper.

FBEELAND GROUP OF MINES

The Freeland group of mines as discussed in this report includes 

the Freeland, Freeland Extension, Toledo, Gum Tree, and Shakespeare 

mines (pi. 5). The veins in these mines include the Freeland, Freeland Extension, Split, Toledo, Gum Tree, and Anchor (pi. 5).

History. The Freeland vein, discovered in 1861, was probably the 

first vein found in the Freeland-Lamartine district. The vein was 

first worked in 1868, and parts of the Freeland group of veins were 

worked almost continuously until 1942. The McClelland tunnel was 

begun in 1900 and completed in 1917 and was to serve as a drainage 

and haulage tunnel. However, a raise to connect with the 6th level 

of the old mine was not driven until 1935. From 1936 until 1942 

some stoping was done on the veins above the McClelland tunnel level.

Production. Complete production records of the Freeland group of 

mines extend back only as far as 1902. Spurr, Garrey, and Ball 

(1908, p. 327) reported that the management of the mine estimated 

that the Freeland mine had produced $4,655,000 worth of ore from 

1861 to 1905. Since 1902, the total production from the Freeland 

group of mines as recorded in the files of the U. S. Bureau of Mines 

has been 37,859 tons of ore which yielded 11,125 ounces of gold, 

98,865 ounces of silver, 216,642 pounds of copper, 3,344,532 pounds 

of lead, and 173,612 pounds of zinc.

Mine workings. The portal of the Freeland tunnel is on the south 

bank of Trail Creek and is about 500 feet northwest of the abandoned 

mining town of Freeland (pi. 5). The Freeland group of mines has 

about 30,000 feet of drifting and 9,300 feet of raises and shafts. A 

plan of the workings is shown in plate 7. At the time of the writers' 

visit to this group of mines only the upper few feet of the Gum Tree 

shaft and about 3,400 feet of the McClelland tunnel were accessible.

Wall rock. Spurr, Garrey, and Ball (1908, p. 328-329) gave some 

information on the wall rocks of the Freeland group of mines; some 

additional information was presented by Carl Belser (written communication, 1940). Apparently most of the mine workings are in 

granite gneiss and pegmatite, which contains layers of biotite-rich 

metasedimentary rocks. Some monzonite dikes and bodies of biotitemuscovite granite were also found in the workings. These units are 

the same as those mapped on the surface along the trace of the veins 

(pl. 2).

The traces of axial planes of two anticlines bracket the trace of 

the Freeland vein (pl. 2). The dip of the axial planes of the anticlines is probably slightly steeper than the dip of the Freeland vein.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 99

Nature of the veins. The Freeland group of veins represents a 

complex fracture system. This group, together with the Brighton, 

Harrisburg, and Turner veins, appears to form a unit of relatively 

flat-dipping veins. Most of the flat-dipping veins have a dip of 45° 

or less, and only a few local dips on any of these veins exceed 60°.

Correlation of the veins is complicated by a lack of work in critical 

areas and by a fault (pi. 7) that crosses between the Toledo-Gum Tree 

workings and the Freeland-Shakespeare workings. Spurr, Garrey, 

and Ball (1908, p. 324-325) suggested that the Freeland vein connected with the Toledo vein and that the Gum Tree vein connected 

with the Anchor vein. In addition, the Anchor vein in the Shakespeare tunnel probably correlates with the Shaffer vein in the McClelland tunnel (pi. 7). The vein called the Anchor in the McClelland 

tunnel is probably the unnamed vein found near the portal of the 

Shakespeare tunnel. The New vein in the McClelland tunnel is 

possibly the same vein as the split off of the Anchor vein in the 

Shakespeare tunnel. Belser (oral communication, 1953) stated that 

the names of the veins on the McClelland tunnel level were those 

given by the miners and that he had used the names even though 

they were probably incorrect. Belser's correlation of veins between 

the 6th level and the McClelland tunnel level seems questionable, but 

any attempt by the writers to solve problems of vein correlation or 

decipher the complexities of the fracture pattern in inaccessible 

workings is not warranted at this time.

The mineralogy of the veins is given by Spurr, Garrey, and Ball 

(1908, p. 329-330), and by Belser (written communication, 1940),, an4 

can be inferred from dump specimens and production records. In 

the Freeland mine, the Freeland vein is composed principally of 

quartz, auriferous pyrite, chalcopyrite, and tetrahedrite with some 

siderite. Galena occurred chiefly in bunches near the surface. 

Renewed movement along the Freeland vein in the area between the 

portal of the Freeland tunnel and the junction with the Freeland 

Extension vein has resulted in what Spurr and Garrey called "friction 

breccia" a breccia consisting of rounded pebble-sized fragments of 

vein material which often is loosely cemented and has the appearance 

of a gravel "vein." The Shaffer vein on the McClelland tunnel level 

has a mineralogy similar to that of the Freeland vein. The Anchor 

vein in the Shakespeare tunnel is composed mostly of quartz and 

pyrite with a little chalcopyrite and sphalerite. The Toledo, Gum 

Tree, Split, and Freeland Extension veins are somewhat different in 

character in that the ore from them consists principally of galena anpL 

sphalerite with some tetrahedrite, chalcopyrite, and pyrite.

The location of the ore shoots, according to Spurr, Garrey, and Ball 

{1908, p. 330) and Belser (written communication, 1940), is controlled

370788 56 6
100 GEOLOGY AND ORE DEPOSITS, COLORADO

principally by vein intersections; in addition, however, the writers 

have noticed what appears to be a strong dip control. The main ore 

body in the Freeland mine was located between the Fourth level 

(Freeland Extension shaft) and the 2d level (Freeland shaft) and 

extended along the vein from the Freeland shaft to the junction of the 

Freeland, Split, and Freeland Extension veins. Vertical sections 

through the Freeland and Freeland Extension shafts show that the 

main ore shoot is, therefore, confined to the steeper part of the Freer 

land vein. (See pi. 7.)

GOLDEN BOD MINE

The collar of the Golden Rod shaft is on the ridge about one-half 

mile northwest of Freeland at an altitude of 9,550 feet. The shaft 

was inaccessible.

The only record of production that could be found in the files of the 

U. S. Bureau of Mines was of a shipment of 126 tons of ore in 1940. 

This shipment yielded a total of 10.8 ounces of gold, 14 ounces of 

silver, 30 pounds of copper, 146 pounds of lead, and 105 pounds of 

zinc. In 1952, part of the dump was being hauled to a mill for recovery 

of gold.

A dump inspection indicated that the wall rock is exclusively 

altered biotite-muscovite granite. Surface mapping shows that the 

granite is a small dikelike body occurring between migmatite and 

granite gneiss and pegmatite.

The vein strikes N. 66° E., dips 68° W., and probably is an extension 

of the New Era vein.

HABRISBUBG MINE

The collar of the Harrisburg shaft is at an altitude of 9,788 feet and 

is about 3,700 feet N. 5° W. of the western peak of Alps Mountain 

(pi. 5). The mine consists of an inclined shaft connecting with drifts 

on two levels (fig. 17). The shaft was almost entirely filled with water.

Only scanty information could be found on the production from the 

Harrisburg mine. According to records of the U. S. Bureau of Mines 

a total of 21.5 tons of ore was shipped from the mine during periods 

of operation between 1935 and 1937, and from 1941 to 1942. This 

ore yielded 1.85 ounces of gold, 56 ounces of silver, 75 pounds of 

copper, 1,790 pounds of lead, and 272 pounds of zinc. Spurr, Garrey, 

and Ball (1908, p. 327) indicated that the mine was worked before 

1900, but no production records previous to 1901 could be found for 

the mine.

The Brighton and Harrisburg mines are connected by two raises 

driven near the junction of the two veins (fig. 17). Spurr, Garrey, 

and Ball (1908, p. 326) mentioned a report that the Brighton appears
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 101

to be the main vein as it continues past the junction, whereas the 

Harrisburg does not appear to cross the Brighton.

The material on the Harrisburg dump indicates that bostonite, 

granite gneiss and pegmatite, migmatite, lime silicate gneiss, and 

biotite-quartz gneiss were found in the workings of the mine.

The Harrisburg vein strikes about N. 58° W. and dips about 48° 

NE. and probably is part of the Freeland vein system. Although the 

Harrisburg is subparallel to the Split vein, which was found in th£ 

Freeland mine, the Harrisburg appears to be a distinct vein and not an 

extension of the Split (fig. 8).

INVINCIBLE MINE

The collar of the Invincible shaft, at an altitude of 10,360 feet, is 

about 2,850 feet N, 60° W. of the western peak of Alps Mountain 

(pi. 5). A possible caved tunnel portal is at road level just below the 

shaft (pi. 2). The shaft was found caved at the collar.

Only one shipment of ore from the mine is recorded in the U. S. 

Bureau of Mines files. In 1908, a shipment of 8 tons of ore yielded 6i5 

ounces of gold and 25 ounces of silver. ,;

According to Spurr, Garrey, and Ball (1908, p. 333) the Invincible 

vein probably strikes about N. 53° E. and dips 70° NW. From the 

surface mapping, the writers have concluded that the Invincible vein 

is probably a southwest extension of the Lone Tree vein. On the 

surface the vein is along the hanging wall of a bostonite dike for about 

1,000 feet southwest of the collar of the shaft.

The rock on the dump is mostly granite gneiss and pegmatite and 

bostonite. Vein material on the dump is chiefly galena and pyrite in a 

quartz gangue.

LAMABTINE MINE

The Lamartine mine has the most extensive workings of any mine 

in the district. The mine has more than 12 miles of workings, but 

only about \% miles of workings is now accessible. The collar of 

the Lamartine main shaft is about 1,000 feet N. 60° E. of the abandoned town of Lamartine, at an altitude of 10,610 feet (pi. 5). The 

portal of the Lamartine tunnel is about 3,900 feet N. 45° E. of the 

Lamartine shaft at an altitude of 9,705 feet (pi. 5). Thelowest workings 

in the mine are accessible through the Old Stag tunnel, whose portal 

is on Trail Creek at an altitude of 9,360 feet and is about 1,300 feet 

N. 12° E. of the Lamartine tunnel portal (pi. 5). Other openings of 

the Lamartine mine include the Falcon tunnel and shaft, the Ben 

Harrison shaft, the Silver Queen shaft, the Money Musk shaft, 

(pi. 5) and the Oneida tunnel, whose portal is covered by the dump
102 GEOLOGY AND ORE DEPOSITS, COLORADO

of the Lamartine tunnel. A 100-ton mill near the portal of the 

Lamartine tunnel is used to concentrate the ore.

History. The early history of the mine is given by Spurr, Garrey, 

and Ball (1908, p. 314-315) as follows 

The Lamartine mine .... was located in 1867. The original discovery was 

made by Peter Cooper, John J. Bougher, and Peter Chavanne, who were searching 

for a gold mine. As the surface indications of this lode were not favorable, one 

of these men sold a fourth interest for $25, another for $250, and Chavanne sold 

out for $5. The property was acquired by Peter Himrod, of New York City, who 

in 1887 let a contract for sinking a shaft in the vein. The shaft encountered the 

Lamartine ore body at a depth of about 100 feet, in May, 1888, one month after 

the death of Mr. Himrod. Fred E. Himrod, his son, gave a lease on a small block 

of ground to Messrs. Armstrong, Burns, Williams, and Hanchett, who produced 

$616,000 from it in 16 months. At the expiration of this lease, vigorous development work was carried on by the owner, under the direction of Silas Hanchett.

The following statement of the production of the mine was taken from the 

record books by the courtesy of the present owners: Total production to August, 

1905, ore, net weight, dried, 67,946,019 pounds, yielding 39,291.81 ounces of gold, 

2,677,470.79 ounces of silver, and 3,232,020 pounds of lead, having a total actual 

value of $2,361,039.15. No copper appears in the returns.

At present not much work is going on at the mine, and many of the old workings 

are inaccessible.

The mine lay idle for several years until reopened by Morris Jule 

in 1937. The old workings had been principally in the area west 

of the main shaft along the Lamartine vein, but the new workings 

were east of the main shaft along the Oneida vein. Also, the old 

workings were in ore which had principal values in silver and lead, 

but the new workings were in ore whose principal value was in gold. 

Along one streak of free gold (see pi. 8 for location) it is reported 

that $158,000 worth of ore was collected in powder boxes. Early in 

1942 government regulations and shortages of men and equipment 

forced the mine to shut down. In 1949 the property was leased to 

the Montana Mining Development Corporation, who were opera ting 

the mine in 1952. Most of the work during 1949-52 had consisted 

of milling dump material from the main shaft dump. Some explora- 

.tive drifting and raising was done along the Lamartine tunnel level 

during 1952.

Production. Production records from the Lamartine mine include 

ore produced from the Lamartine, Falcon, Ben Harrison, Oneida, 

Old Stag, and Money Musk mines. A record of production from this 

mine from 1867 to 1952 was obtained by combining the data presented 

by Spurr, Garrey, and Ball (1908) with the more recent records of 

the U. S. Bureau of Mines. About 300,000 tons of ore has been 

produced from this group of mines along the Lamartine-Oneida veins. 

This ore has yielded 78,184.71 ounces of gold, 3,092,962 ounces of
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 103

EXPLANATION

B

Shaft

x 

Shaft passing through level

Bottom of shaft

Head of raise 

or winze

Raise or winze extending 

through level

Foot of raise 

or winze

Caved workings

OLD STAG 

TUNNEL

Elev 9360 ft

500 Feet

From company map by W. H. Wiley, 1911, with 

additions byJ. E. Harrison, 1952. Published 

with permission of the owners

FIGURE 19. Plan of part of the workings on the Oneida-Mendick veins.

silver, 162,802 pounds of copper, 5,601,598 pounds of lead, and 

1,258,136 pounds of zinc.6

Mine workings. The mine has been opened through several adits 

and shafts. The principal openings are the main shaft, which con-

 Published with permission of owner.
104 GEOLOGY AND ORE DEPOSITS, COLORADO

nects the Lamartine tunnel (10th level) with the surface; the Lamartine tunnel, which is about 9,000 feet long; the Oneida tunnel; and 

the Old Stag tunnel. (See pis. 4 and 8, and fig. 19.) In addition, several smaller adits and shafts, notably the Silver Queen and 

Money Musk, (pi. 5) have served to explore, the veins. The main 

underground shaft (Johnson shaft in pi. 8) was used to raise ore from 

below the Lamartine tunnel. The approximate extent of the stopes 

in the mine is shown in plate 3. Only a relatively small part of the 

mine was accessible at the time of the writers' visits. A cave on the 

Lamartine tunnel level about 300 feet east of the main shaft blocks 

access to the older workings around the main shaft. The Johnson 

shaft is caved, and the portal of the Oneida tunnel has been buried 

under the Lamartine tunnel dump. The Montana Mining Development Corporation cleared several caved areas from the Old -Stag 

tunnel hi order to drain the workings and make them accessible.

Wall rock. Most of the accessible mine workings have been driven 

through migmatite (pis. 3, 4, and 8; fig. 19). Local layers of biotitequartz gneiss and granite gneiss and pegmatite are exposed in some 

parts of the mine. Layers and small bodies of biotite-muscovite 

granite and pegmatite also occur locally in the mine. According to 

Spurr, Garrey, and Ball (1908, pi. 65), the workings west of the main 

shaft are in "massive granite," "gneissoid granite," and pegmatite. 

The surface exposures west of the main shaft are principally granite 

gneiss and pegmatite with some biotite-muscovite granite and granodiorite. The gneissoid granite mapped by Spurr and Garrey probably is 

equivalent to the granite gneiss and pegmatite of this report; the 

massive granite is probably biotite-muscovite granite and not the 

granodiorite which is characteristically well foliated where exposed 

on the surface in this area. In addition, Spurr and Garrey showed 

a bostonite dike along the footwall of the vein west of the main shaft.

The structure of the wall rock indicates that the accessible part of 

the Lamartine tunnel and that part of the Old Stag tunnel on the vein 

have been driven approximately parallel to the trend of a major 

abnormal anticlinorium. The vertical projection shown in plate 3 

shows the change in plunge of the axis of this major fold. Although 

the plunge of the axis is principally to the northeast, locally it is to 

the southwest. The vertical section along the crosscut part of the 

Old Stag tunnel (pi. 4) shows some of the small folds on the flank of 

the anticlinorium to be overturned and to grade into upright 

folds as the axial region of the major fold is approached. The 

principal gold-bearing part of the Lamartine-Great Western vein 

group is in the axial zone of the major anticlinorium.

Veins. The names given to parts of the Lamartine-Great Western 

vein group are shown in figure 8. The eastward-trending part of the
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 105

group at the southwestern end is called the Lamartine vein; the adjacent part that trends northeasterly is called the Oneida vein; the 

diagonal link is called the Mendick vein; and the norfcheast end of 

the group is called the Great Western vein. All of these veins dip 

steeply to the north. A vein found underground about parallel to 

the Lamartine vein but a few feet to the north has been called the 

Crown vein. The Crown vein has been mined extensively along with 

the Lamartine vein in the area west of the main shaft.

This group of fissures has been strongly mineralized from about 

3,000 feet west of the Lamartine shaft eastward to the portal of the 

New Era south tunnel (pi. 5). Both ends of the system break up 

into a series of weakly mineralized or barren fractures. This horsetailing is very noticeable west of the Silver Queen shaft (Spurr, Garrey, and Ball, 1908, fig. 119). The mines located on the minor veins 

west of the Lamartine shaft (Chloride, Collateral, Financier, R. E. 

Lee, St. Louis) have produced little or no ore.

Spurr, Garrey, and Ball (1908, p. 315) described the ore from the 

Lamartine vein west of the shaft as follows 

The vein material contains abundant galena and blende, with some pyrite. 

The product has been chiefly galena ore which has been selected from ore containing blende. The zinc-bearing ore as a rule is poor in gold and silver. The best 

ore appears to be fine galena, much of the coarse galena being of lower grade as 

regards gold and silver. . . .

The ore from the Oneida vein consists principally of pyrite, gold, 

and chalcopyrite. Southwest of the Johnson shaft (pi. 8) the vein 

contains pods and stringers of galena and sphalerite that cut the older 

pyrite-chalcopyrite vein material, thus forming what has been called 

composite ore by Bastin and Hill (1917, pp. 112-113). The quantity 

of galena and sphalerite in the composite ore increases toward the 

main shaft, and west of the main shaft the vein (there called the 

Lamartine) is composed of galena-sphalerite type ore. The Oneida 

vein also is composite in character near the Mendick split. Quartz 

is the gangue mineral accompanying the pyrite-gold ore type, and both 

quartz and carbonate are gangue minerals accompanying the galenasphalerite ore type.

As so much of the mine is inaccessible, control of the ore deposits 

is conjectural. Spurr, Garrey, and Ball (1908, p. 318) suggested that 

the ore body west of the main shaft resulted from mineral deposition 

at the junction of the Oneida and Lamartine veins. The miners 

report that the ore is thicker on the steep parts of the vein and thinner 

or absent on the flat parts. On the Old Stag tunnel level the location 

of the ore bodies seems to be influenced by a change in strike (pi. 4). 

The vertical projection along the veins (pi. 3) suggests a northeastward-plunging shoot structure for the ore bodies below the Falcon
106 GEOLOGY AND ORE DEPOSITS, COLORADO

shaft and below the portal of the Lamartine tunnel. Junction of the 

unnamed vein southwest of the Mammoth vein with the Oneida vein 

also may have influenced the location of an ore body. These data 

seem to indicate clearly that the type of host rock is not a factor 

controlling location of these ore bodies.

Milling of dump material. An increase in metal prices since the 

1890's has made reworking of old dumps profitable at certain times. 

During 1951-52 the Lamartine mill processed material from the 

dump at the Lamartine shaft. Harold Anderson, superintendent of 

the Lamartine mine and mill for the Montana Mining Development 

Corporation, supplied the information that 100 tons of dump material 

yields about 3,000 pounds of concentrate which is worth about $290 

to $300 per ton. From the assay information supplied by Anderson, 

the tenor of the dump was calculated to be 0.15 percent lead, 0.15 

percent zinc, 0.0223 ounce of gold, and 1.5 ounces of silver per ton. 

All figures given are averages.

LITTLE JOHNIE GROUP OP MINES

The Little Johnie group of three mines is on the south side of Trail 

Creek about 800 feet southeast of the abandoned town of Preeland 

(pi. 5). The portals of the three tunnels are at altitudes of 8,988, 

9,071 and 9,215 feet.

All three tunnels have been driven approximately along the axis 

of an anticline. The distribution and relation of the main veins and 

rock layers along the anticlinal crest are shown in figure 7.

Lower tunnel. The lower tunnel is a crosscut adit that bears S. 

35° W. for a distance of 70 feet from the portal to an eastwardtrending vein; beyond the vein the adit crosscuts to the south for 

about 30 feet then follows a southwestward-trending gouge lead for 

about 300 feet at which point it turns and follows another gouge lead 

trending S. 35° E. (fig. 20). The only stope in the mine is on the 

short westerly drift near the portal.

The lower tunnel is driven into the northwest limb of an anticline 

that trends about N. 5° E. and plunges 28° to 40° NE. Layers of 

garnetiferous biotite-quartz gneiss, migmatite, and granite gneiss 

and pegmatite are exposed in the mine. A pegmatite dike 16 feet 

wide cuts through the older pre-Cambrian rocks at a point 180 feet 

from the portal (fig. 20).

The only metallized vein in the lower mine strikes N. 85° W. and 

dips to the north. The stoped area of this vein was inaccessible in 

1952. Samples of ore found on the dump show pyrite, chalcopyrite, 

galena, and sphalerite in a quartz, carbonate, and fluorite gangue. 

If the samples collected from the dump are representative of the ore 

body, then the vein is somewhat different from most of the veins in
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 107

Biotite-quartz gneiss, 

locally garnetiferous J

Contact, dashed where inferred

Fault, showing dip; dashed where 

approximately located

Strike and dip of foliation

Strike and dip of foliation 

and plunge of lineation

Vein, dashed where approximately located

Geology by J. E. Harrison, 1952

150 Feet

I Datum is mean sea level 

FIGURE 20. Geologic map of the lower tunnel, Little Johnie group of mines.

the district. The two principal distinguishing features of this vein 

are that carbonate rather than quartz forms most of the gangue and 

fluorite, usually uncommon, is present in fairly large quantities. 

The vein is a fissure filling in brecciated garnetiferous quartz-biotite 

gneiss, and is very vuggy. Crustification of the vein minerals allows 

a simple deduction as to paragenetic sequence. Following brecciation 

and fracturing of the host rock, quartz and pyrite partly replaced the 

wall rock along the margins of the fractures; some quartz crystals 

formed a thin crust along open fissures. Renewed movement along 

the main fault reopened some of the old fissures and opened new 

fractures. White calcite and ankerite, buff dolomite, pink rhodochrosite, and euhedral cubic and octahedral galena were deposited as
108 GEOLOGY AND ORE DEPOSITS, COLORADO

new crusts on the older quartz-pyrite material. Some disseminated 

galena, sphalerite, pyrite, and chalcopyrite were also deposited during 

this second stage. The carbonates also filled some of the new fractures accompanying the second stage of shearing. The second stage 

ended with the deposition of fluorite and chalcopyrite hi the centers 

of the vuggy openings and as crusts completely filling some of 

the fissures. The fluorite-chalcopyrite phase overlapped the strong 

carbonate phase to some extent.

Middle tunnel. The first 155 feet of the middle tunnel is a crosscut 

adit driven S. 7° W. The tunnel then bifurcates, extending about 

75 feet west and 115 feet east along the principal veins. A shallow 

winze, several short side drifts, and two small stopes complete the mine 

workings (fig. 21).

The crosscut adit was driven approximately on the axial plane of 

an anticline. The workings expose layers of gametiferous biotitequartz gneiss, amphibolite, migmatite, and granite gneiss and pegmatite, some of which is alaskitic. A pegmatite dike 1 foot thick cuts 

through the older pre-Cambrian rocks at an angle of about 45° to the 

fold axis (fig. 21).

The drift follows two veins, each of which range in strike and dip, 

but which on the average trend due east and dip 38°-70° N. The 

eastward-trending veins are intersected by two veins that trend N. 

30°-40° E. and dip 60°-70° NW. (fig. 21). Both the eastward- and 

northeastward-trending sets of vein fissures are weakly mineralized 

and contain pyrite, chalcopyrite, sphalerite, and galena in a predominantly quartz gangue. Some carbonate gangue occurs with the sulfides 

in the thicker parts of the ore streaks. The veins range in width 

from % to iyz inches.

Two local controls for the thickening of the ore streak can be seen in 

the mine. Intersection of the two eastward-trending veins at points 

about 30 feet east and 30 feet west of the crosscut (see fig. 21) has 

formed small ore pods. On the southwest wall of the room near the 

breast of the east drift, the southernmost vein has several changes in 

dip in the space of about 30 feet vertically down the vein. On the 

flat parts of the vein only % inch of ore appears, but on the steep parts 

\% inches of ore is present. The intersections between the northeastward-trending vein and the eastward-trending veins do not appear to 

be enriched.

Upper tunnel. The upper tunnel is a 200-foot crosscut adit that 

trends, in general, about S. 10° E. The adit has been driven into the 

east flank of the anticline not far from the anticlinal axis. Layers of 

gametiferous biotite-quartz gneiss and migmatite are exposed in the 

tunnel; two pegmatite bodies are also exposed, a 12-foot-thick con-
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK i COUNTY 109

PORTAL

Timbered °) /? Elev 9071 ft 

Overburden

10-foot stringer of galena, sphalerite, 

and chalcopyrite; stringer is % in. 

thick at vein junction and tapers 

to Vie in. at each end

Sample 357-2 

Sample 357-1

in. gouge seam with '' 

sparse quartz, pyrite 

galena, sphalerite, 

and chalcopyrite

% in. ore on flat 1% in. 

ore on steep parts of 

1 in. of galena, chalcopyrite, the vein 

sphalerite, and pyrite in a 

quartz gangue. Extends from 

vein junction west of raise 

through stope east of raise

150 Feet

Datum is mean sea level. 

EXPLANATION

Strike and dip of foliation 

and plunge of lineation

.Granite gneiss and 

pegmatite

Migmatite

Biotite-quartz gneiss, 

garnetiferous

Amphibplite

Strike and dip of foliation 

showing plunge of lineations

CD Bearing and plunge of lineation

Vein, showing dip; dashed where 

approximately located

Contact, dashed where 

approximately located

Strike and dip of foliation

Fault, showing dip; dashed where 

approximately located

E) 

Head of winze

Foot of raise

D 

Ore chute

Geology by J. E. Harrison and J. D. Wells, 1952 

FIGURE 21. Geologic map of the middle tunnel, Little Johnie group of mines.

formable body near the tunnel portal and a crosscutting body near 

the breast of the workings (fig. 22).

No strongly mineralized veins are exposed in the crosscut. A 

6-inch-wide zone of limonite-stained gouge and crushed migmatite is 

exposed about 40 feet from the tunnel breast. This zone may be a 

northeasterly extension of the Alabama vein (pi. 5).

Production from the group. Production of ore from the Little 

Johnie group of mines has been small. No ore has been produced
110 GEOLOGY AND ORE DEPOSITS, COLORADO

EXPLANATION

K 12 in. H

1 Drag fold '

plunges 28°N. 28°E. Biotite-quartz gneiss, 

garnetiferous

6 in. of limonite-stained 

gouge and crushed 

migmatite

50

Contact, dashed where inferred

Fault, showing dip; dashed where 

approximately located

Strike and dip of foliation

Strike and dip of foliation 

and plunge of lineation

Vein, showing dip; dashed where 

approximately located

150 Feet

Datum is mean sea level

Geology by J. E. Harrison, 1952 

FIGUBE 22. Geologic map of the upper tunnel, Little Johnle group of mines.

from the upper tunnel, and indications are that only a few tons of 

ore have come from the middle and lower tunnels.

LONE TREE MINE

The Lone Tree mine consists of a tunnel and two shafts that connect 

with the tunnel workings (fig. 23). The tunnel portal is at an altitude 

of 9,565 feet and is about 3,300 feet S. 87° W. of Freeland (pi. 5). 

The Lone Tree shaft is about 800 feet S. 29° W. of the tunnel portal, 

and the Lone Tree Extension shaft is about 300 feet farther from the 

tunnel portal along the same line. A shallow shaft (Brownell), which 

is probably on the Lone Tree vein, is about 1,000 feet southwest of the 

Lone Tree Extension shaft.

Although the location of the portal of the Lone Tree tunnel is 

indicated by Spurr, Garrey, and Ball (1908, pi. 17), no mention of the 

mine is made in the text of their report. Undoubtedly the mine was 

worked as early as 1905, but the first record of production in the files 

of the U. S. Bureau of Mines is for the year 1913. Production records 

indicate that the mine was worked from 1913 to 1914, in 1920, and 

from 1936 to 1945. The first development along the Lone Tree 

tunnel exploited ore that was rich in gold and low in silver, lead, and
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY HI

TELLER TUNNEL

Elev 9279 ft rt

LONE TREE TUNNEL

lev 9565 ft

// » '

//// -\v

//// ~* TELLER SHAFT 

Elev 9724 ft '{L1

/r* Caved workings

LONE TREE SHAFT

/ / Elev 9750 ft

WINZE //

LONE TREE V/'NN) LONE TREE 

EXTENSION \ // '& EXTENSION SHAFT

TUNNEL NXV/ // Elev 9735 ft 

Elev 9674 ft %CN//

// (^

Datum is mean sea level

BROWNELL SHAFT

--0 Elev 9860 ft

Modified from maps loaned by C L Harrington

FIGURE 23. Plans of the Lone Tree and Teller mines.

zinc. Subsequent work found ore rich in silver, lead, and zinc, but 

low in gold. During the different recorded periods of operation, a 

total of 1,757 tons of ore was shipped from the mine. This ore 

yielded 775.7 ounces of gold, 2,345 ounces of silver, 582 pounds of 

copper, 24,352 pounds of lead, and 16,300 pounds of zinc.

Only the first 315 feet of the tunnel were accessible (fig. 24), however, a map loaned by C. L. Harrington shows the main tunnel to be 

about 1,650 feet long (fig. 23).

The wall rock in the accessible part of the tunnel is mostly migmatitic biotite-quartz gneiss, with some pegmatite and quartz gneiss. 

The dump at the tunnel portal contains sillimanitic biotite-quartz 

gneiss, migmatite, granite gneiss and pegmatite, quartz diorite, and
112 GEOLOGY AND ORE DEPOSITS, COLORADO

EXPLANATION

PORTAL

Elev 9565 ft

Biotite-quartz gneiss, 

very migmatitic

10 in. of fractured, silicified 

biotite-quartz gneiss with 

disseminated quartz and 

pyrite

*2 ft. of disseminated quartz and 

pyrite and quartz-pyrite stringers. 

* in. of black gouge on both rootwall and hanging wall

8 in. of disseminated

quartz and pyrite ''Caved 

Timbered

Contact, dashed where inferred

,59

Strike and dip of foliation

Strike and dip of foliation 

and plunge of lineation

Vein, showing dip; dashed 

where inferred

Vein, showing true 

strike and dip

Vein, showing plunge 

of slickensides

Foot of raise

D 

Ore chute

50 0

Geology by J. E. Harrison, 1952 

150 Feet

Datum is mean sea level 

FIGURE 24. Geologic map of part of the Lone Tree tunnel.

biotite-muscovite granite. The dumps at the shafts include bostonite 

in addition to those rock types found on the tunnel dump.

The Lone Tree vein appears to have an average strike of about N. 

34° E. and an average dip of about 70° NW. This vein is probably a 

southwesterly extension of the New Era vein.

Examination of vein material on the dump indicates that the ore 

mined consisted of pyrite, chalcopyrite, tetrahedrite, sphalerite, and 

galena in a gangue composed of quartz, calcite, and siderite.

MENDICK MINE

The portal of the Mendick tunnel, at an altitude of about 9,500 

feet, is in a small gulch and about 4,300 feet S. 87° W. from the 

abandoned town of Freeland (pi. 5).

U. S. Bureau of Mines production records on the Mendick mine 

indicate that the mine was operated during 1916, and then again from
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 113

1938 to 1940. A total of 174 tons of ore was shipped from the mine 

during the two periods of operation. This ore yielded a total of 35.8 

ounces of gold, 67 ounces of silver, and 120 pounds of zinc.

In 1952 the tunnel was caved at the portal. The vein is exposed 

hi two places on the side of the hill above the tunnel where old 

stopes have caved. The vein appears to strike about N. 60° E. and 

dip 78° NW. Only quartz-pyrite vein material was seen on the 

dump.

The Mendick vein connects the Lamartine-Oneida vein with the 

Great Western vein (fig. 8). Short drifts have been made on the 

Mendick vein in the Old Stag tunnel (pi. 4) and hi the New Era 

mine.

MILLER MINE

The portal of the Miller tunnel is 1,650 feet N. 35° W. of the 

western peak of Alps Mountain (pi. 5), at an altitude of 9,921 feet. 

The Miller tunnel is on patented ground and is owned by Diamond 

Mountain Mines, Inc.

Early production figures for the Miller mine are not available, but 

the production from the mine since 1908 has been recorded by the 

U. S. Bureau of Mines. The available production records show that 

ore was shipped in 1908, 1928, 1933-35, and in 1939 and 1940. During these periods a total of 160 tons of ore was produced from the 

mine. This ore yielded 43.2 ounces of gold, 1,960 ounces of silver, 

35 pounds of copper, 3,484 pounds of lead, and 652 pounds of zinc.7

The first 80 feet of the tunnel is a crosscut trending almost due 

south to the vein. From this point the tunnel has been drifted 

S. 63° W. along the vein for about 1,200 feet (pi. 9). At 210 feet 

from the portal a raise extends through to the surface, and at 850 

feet a winze extends down 80 feet to a short level. The tunnel was 

inaccessible beyond the winze in 1952.

The wall rock in the accessible part of the tunnel is principally 

biotite-muscovite granite (pi. 9). A few thin layers or inclusions of 

biotite-quartz gneiss and granite gneiss and pegmatite are exposed 

near the portal. A small bostonite dike that cuts through the preCambrian rocks is exposed in the crosscut from the portal.

The Miller vein strikes about N. 63° E. and dips on the average 

about 80° NW. Where observed this vein is accompanied by a 6-inch 

to 4-foot-wide sheared zone containing disseminated pyrite and local 

disseminated chalcopyrite, sphalerite, and galena in a quartz gangue. 

Locally horses of country rock occur in the vein (pi. 9), and some of 

the horses contain disseminated pyrite cut by thin stringers of chalcopyrite, sphalerite, and galena.

" Published with permission of the company.
114 GEOLOGY AND ORE DEPOSITS, COLORADO

At the junction between the crosscut from the portal and the main 

drift, a bostonite dike is offset along the vein. A friction breccia has 

formed locally between the footwall and hanging wall veins. This 

friction breccia contains fragments of bostonite, granite gneiss and 

pegmatite, biotite-muscovite granite, biotite-quartz gneiss, and 

quartz-pyrite vein material. The breccia is cemented in part by 

quartz-pyrite and in part by chalcedonic quartz. The breccia extends 

about 100 feet southwest along the vein from the point where the 

crosscut joins the main tunnel.

Spurr, Garrey, and Ball (1908, p. 334-335) gave a brief description 

of the Miller mine. They attributed the ore shoot at the winze to the 

intersection of two slightly mineralized fissures which form "a small 

trough of ore pitching to the southwest and containing 1 to 4 inches of 

galena-sphalerite ore.''

NEW ERA MINE

The main part of the New Era mine is on the south side of Trail 

Creek about 3,000 feet upstream from the abandoned town of Freeland; a smaller part of the mine is on the north side of Trail Creek. 

The main tunnel portal is at an altitude of 9,183 feet (pi. 5). The 

mine exploits two subparallel veins which locally are less than 50 feet 

apart.

History. A brief history of the mine taken from the owner's application for an exploration loan (Conwell, C. N., written communication, 1950) is quoted in the following paragraph.

In 1878 H. G. Mils recorded the claims, Great Western and Great EasternThese were not worked much until leased to the New Era Mining Company in 

the 1890's. This company purchased the mines in 1903 and the Oldbury claim 

in 1904. The owners erected a mill l}i miles east of the mine and operated 

successfully until 1912, at which time the mine was purchased by the Trail Creek 

Mining Company. A new mill was constructed near the portal of the south 

tunnel and operated successfully until 1914. In 1914 the mines were operated 

for two years by the Calumet Corbin Mining Company and then regained by the 

Trail Creek Mining Company. However, they were not operated during World 

War I. During the early years of operation, gold was the principal value as lead 

was then selling for approximately three cents a pound; some of the ore at this 

time carried as much as 50 percent lead. It has been reported that in operations 

above the tunnel level (4 stopes and over 3,000 feet of drifting along the 3 main 

veins) that over $700,000 worth of ore has been taken out. Dr. James Underbill, 

recently retired Professor of Mining at the Colorado School of Mines, was left to 

dispose of the property as he had been the company Engineer and Trustee. The 

title of the mines passed to Lucy Underbill in 1939. A few records and some 

maps have been made, but the mine was never reopened. The mines were purchased from Lucy Underbill by Cleland N. Conwell. Since 1946 mapping, 

general history research, and some exploration work has been carried on.

In 1952 Mr. Hans Mosch began development work in one of the old 

winzes.
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 115

Production. Complete production records of the New Era mine 

are not available for the period 1890-1907. The records in the files 

of the U. S. Bureau of Mines show that the mine was operated intermittently from 1908 to 1949. During the period when records had 

been kept, 36,762 tons of ore had been produced from the mine. This 

ore yielded 8,512 ounces of gold, 32,595 ounces of silver, 28,268 pounds 

of copper, 904,248 pounds of lead, and 82,193 pounds of zinc. 8

Mine workings. The mine is accessible through two adits and a 

shaft. The main adit, called the south tunnel, is on the south side of 

Trail Creek, and the shaft and a smaller adit, called the north tunnel, 

are on the north side of Trail Creek (pi. 5). The south tunnel (pi. 10) 

has been driven on the New Era vein for 1,055 feet in a general S. 32° 

W. direction. Two crosscuts connect with about 1,100 feet of ^drifting 

on the Great Western vein. In addition, about 120 feet of drifting 

has been done on the Mendick and Oldbury veins. The north tunnel 

(fig. 25) has been driven 311 feet N. 32° E. on the New Era vein. 

Two short crosscuts to the west show the Great Western vein to be 40 

to 70 feet west of the New Era vein. The shaft connects with what is 

called the 200-foot level, and Spurr, Garrey, and Ball (1908, p. 320) 

stated that about 1,000 feet of drifting on the Great Western vein 

and 500 feet of drifting on the New Era vein had been done on this 

level.

Wall rock. Except for one small pegmatite dike, all of the accessible 

workings of the New Era mine have been driven in migmatite. The 

migmatite is highly contorted, and the fold symbols on the maps (pi. 

10 and fig. 25) represent minor rolls on the flank of a major anticline 

lying west of the mine workings. Both the New Era and the Great 

Western veins are approximately parallel to the general trend of the 

foliation. The veins are slightly steeper than the foliation, and they 

have a pronounced tendency to split, roll out into the foliation, and 

become a weakly mineralized fracture.

Veins. The New Era vein strikes N. 15°-35° E. and dips on the 

average about 73° NW. The New Era vein probably connects with 

the Golder Kod vein to the northeast and with the Lone Tree vein to 

the southwest (pi. 5). The Great Western vein strikes approximately parallel to the New Era vein for most of its length in the New 

Era mine workings. A slight divergence between these two veins is 

apparent at the northeast end of the north tunnel and at the southwest 

end of the south tunnel. Where the two veins are exposed, at directly 

opposite points, the Great Western vein is everywhere slightly flatter. 

More of the mine workings were accessible on the Great Western vein 

at the time of the visit by Spurr and Garrey. They reported (1908, 

p. 321) that the Great Western vein offsets the cross vein (Oldbury

1 Published with permission of owner. 

370788 56 7
116 GEOLOGY AND ORE DEPOSITS, COLORADO

16-in. broken zone with a 2-in. 

quartz pyrite -galena - gouge 

vein on the footwall

3 in. of gouge plus quartz, pyrite, chalcopyrite, and galena 

in west vein; 1 in. of same 

material in east vein. Some 

quartz-chalcopyrite-galena 

stringers in broken ground 

between the veins

Opencut 

Elev9140ft

in. of galena on 

hanging wall; 8 

in. of quartz, 

pyrite, chalcopyrite, and 

gouge or» 

foot-wall

\\s Opencut

Elev9140ft 

Snow shed 

NEW ERA SHAFT

Note: 2 to 8 in. of quartz, pyrite, and gouge 

with intermittent streaks of galena and 

chalcopyrite in New Era vein from first 

crosscut to the tunnel breast. The vein 

has a tendency to split, roll out into the 

foliation, and become a weakly mineralized fracture

Plunge of slickensides 

Strike and dip of foliation

Strike and dip of foliation 

and bearing and plunge 

of lineations

Vein, showing dip; dashed 

where inferred

re

Collar of shaft at surface

50

Geology by J. E. Harrison, 1952 

100 Feet

Datum is mean sea level

FIGURE 25. Geologic map of the north tunnel of the New Era mine.

vein) in the southernmost crosscut in the south tunnel; the cross vein 

in turn offsets the New Era vein (pi. 10). The Mendick vein was not 

seen at the tune of the visit, but the owner reports that the Great 

Western vein is offset along the Mendick vein. None of the offsets 

are more than a few feet in apparent horizontal displacement. The 

Mendick vein apparently does not extend to the New Era vein. The 

Great Western vein is connected to the Lamartine vein by the Mendick vein. The continuations of the Great Western and the Lamartine 

veins are less well mineralized north and south, respectively, of their 

junction with the Mendick vein. The Mendick vein thus has the 

geometric position of a diagonal link (McKinstry, 1948, p. 314) 

between two well-mineralized, possibly related, veins (fig. 8).

The mineralogy of the veins is similar to most of the silver-lead-zinc 

veins in the district. The Great Western vein is notable for its rela-
FREELAND-LAMARTESTE DISTRICT, CLEAR CREEK COUNTY 117

tive lack of sphalerite and abundance of chalcopyrite. Two stages 

of mineralization can be recognized: the first is represented principally 

by quartz and pyrite; the second, which locally can be recognized by 

mineralized stringers cutting the first-stage minerals, consists of 

quartz, pyrite, chalcopyrite, and galena which were deposited together 

with minor carbonate, sphalerite, and tetrahedrite.

At least two local controls for the ore bodies were observed in the 

mine. Horses of country rock tend to be enriched by stringers and 

disseminated ore, and vein intersections appear to be favorable areas 

for the deposition of ore.

Most of the ore produced from the mine has come from the Great 

Western vein. This vein has been stoped along most of the tunnel 

level workings in the south tunnel. According to Spurr, Garrey, and 

Ball (1908, p. 322), "The first-class ore of the mine . . . carries from 

1% to 2 ounces of gold, 5 to 21 ounces of silver, and 45 to 50 percent 

of lead (per ton). Copper up to 5 percent and zinc up to 3 percent 

have at times been obtained. ..."

POOR MAN MINE

The Poor Man mine is near the head of Trail Creek, on the north 

side of the stream, at an altitude of 10,136 feet (pi. 5).

Records of the U. S. Bureau of Mines indicate that the Poor Man 

mine was operated from 1902 to 1909, in 1921, and from 1933 to 1935. 

During this time, 222 tons of ore yielding a total of 82.5 ounces of gold, 

8,259 ounces of silver, 625 pounds of lead, and 159 pounds of zinc was 

produced.

At the time of the writers' visit, the tunnel was caved at the portal. 

Spurr, Garrey, and Ball (1908, p. 319-320) reported that the workings 

in 1906 consisted of a 250-foot crosscut and a drift on a vein that 

strikes a few degrees south of west and dips 75° NW. This vein 

probably intersects the Brazil vein west of the Brazil shaft.

The waste rock on the dump and the rock exposed at the surface is 

principally granite gneiss and pegmatite. Limonite and quartz were 

the only vein minerals found on the dump.

SILVER LINK MINE

The collar of the Silver Link shaft is about 2,500 feet southwest of 

the abandoned town of Freeland, at an altitude of about 9,465 feet 

(pl. 5).

In 1952 the workings were inaccessible because the head frame of 

the hoist had partly fallen into the shaft. A mine map loaned by C. L. 

Harrington shows the workings to consist of a shallow shaft connected 

to a 130-foot drift. One small area has been stoped.

At the collar of the shaft the Silver Link vein has a strike of N. 48°
118 GEOLOGY AND ORE DEPOSITS, COLORADO

E. and a dip of 62° N. Specimens on the dump indicate that the vein 

material consists of pyrite, chalcopyrite, galena, and sphalerite in a 

quartz and siderite gangue. The wall rock is granite gneiss and pegmatite which contains local 10- to 20-foot layers of biotite-quartz gneiss. 

The vein cuts across the general trend of foliation in the bedrock at a 

low angle.

Production of ore from the Silver Link mine has been small.

TELLER MINE

The Teller mine consists of a tunnel and a shallow shaft (fig. 23). 

The portal of the Teller tunnel, at an altitude of 9,279 feet, is in a 

small gulch about 2,500 feet N. 81° W. of the abandoned town of Freeland (pi. 5). The collar of the Teller shaft is 1,500 feet S. 41° W. of 

the tunnel portal. In 1952, the tunnel was caved at the portal, and 

the shaft was beginning to cave.

The Teller mine was worked from 1902 to 1912, in 1922, and in 1935. 

During the periods of operation a total of 126 tons of ore was produced 

from the mine. According to records of the U. S. Bureau of Mines, 

this ore yielded 60.8 ounces of gold, 359 ounces of silver, 558 pounds of 

copper, 5,939 pounds of lead, and 625 pounds of zinc.

A plan (fig. 23) loaned by C. L. Harrington shows the workings of 

the mine. The adit has been drifted about 1,800 feet in a general 

S. 50° W. direction.

A geologic map of part of the Teller tunnel given by Spurr, Garrey, 

and Ball (1908, p. 323, fig. 122) shows the wall rock to be gneiss. The 

dump consists mostly of migmatite and sillimanitic biotite-quartz 

gneiss, with a few fragments of bostonite. Spurr and Garrey also 

reported (p. 323) that only weakly mineralized veins of composite ore 

had been found up to the time of their visit. The production records 

indicate that better ore was found along the southwestern end of the 

present workings. A feature worth noting is that Spurr, Garrey, 

and Ball (1908, p. 323) reported that the main northeastwardtrending vein was slightly offset along a nearly eastward-trending 

vein about 300 feet from the mine portal.

TURNER MINE

The Turner mine has two surface openings, a tunnel portal and a 

shaft. The portal, at an altitude of 9,277 feet, is on the north side of 

Trail Creek about 1,850 feet N. 31° W. of the abandoned town of 

Freeland (pi. 5). The collar of the Turner shaft is about 600 feet N. 

71° E. of the tunnel portal and is on the top of a ridge at an altitude of 

9,389 feet.

Production. The Turner mine has been operated intermittently 

since the late 1890's. As the mine has been operated at times by the
FREELAND-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 119

same company that worked the Freeland, Toledo, and Anchor mines, 

the production records for the Turner are not always discrete from 

the records of these other mines. Production from the Turner was 

reported separately to the U. S. Bureau of Mines in 1909, 1910, and 

from 1942 to 1950. During these periods, 864 tons of ore was produced from the mine. This ore yielded 487.1 ounces of gold, 1,283 

ounces of silver, 1,564 pounds of copper, 50,531 pounds of lead, and 

878 pounds of zinc.

Mine workings. The accessible part of the mine consists of a 

tunnel from which a raise extends to an upper level, and an underground shaft connecting the tunnel level with drifts on four lower 

levels (pi. 11). Extensive stoping has been done above the upper 

level and between the tunnel level and the fourth level. A shaft 

from the surface and part of the upper level are inaccessible.

Wall rock. The mine workings are mostly in migmatite although 

most of the surface exposures in the area over the mine consist of 

granite gneiss and pegmatite. Granite gneiss and pegmatite was 

found in the westernmost parts of the tunnel level, the second level, 

and the fourth level. A layer of amphibolite is exposed on the tunnel 

level between the granite gneiss and pegmatite and the migmatite. 

Biotite-muscovite granite is exposed in the eastern end of the fourth 

level drift (pi. 11).

Wall-rock alteration along the veins is most noticeable in the 

migmatite. For about 6 inches on both sides of the veins the migmatite contains pyrite-sericite layers as a replacement of the biotite 

layers.

Veins. The Turner mine exploits a lode-type ore deposit. The 

main veins strike N. 35°-90° E. and dip 25°-62° NW. The vein 

system probably connects with the Falu vein to the west (pi. 5).

The ore minerals are pyrite, chalcopyrite, sphalerite (both marmatite and resin sphalerite), galena, and minor amounts of tetrahedritetennantite. The gangue is principally vein quartz and chalcedonic 

quartz with minor amounts of carbonate.

Supergene alteration of the ore is strong on the tunnel level but 

decreases rapidly toward the first level and is not apparent on the 

second level. The greatest depth of supergene alteration noted was 

120 feet vertically below the present surface.

Localization of the ore. Structural control of this ore deposit is 

quite striking. The geologic map of the mine (pi. 11) illustrates 

strike-slip control in that the ore is concentrated on a prominent 

change in strike. The vertical section through the underground shaft 

(fig. 26) illustrates the dip-slip control in that the thickest galena ore 

is concentrated on the steeper part of the lode zone. The combined 

movement in the fracture zone has been such that the northwest
120 GEOLOGY AND ORE DEPOSITS, COLORADO

2 to 10 in. of galena, chalcopyrite, and tetrahedrite

Disseminated pyrite 

and chalcopyrite

4 in. veins of quartz, pyrite, chalcopyrite, 

galena, and some sphalerite. Heavily. 

disseminated pyrite and chalcopyrite

 Hoist roon

ADIT LEVEL

Approximate Elev 9280 ft

Heavilydisseminated pyrite and chalcopyrite. Thin stringers r

f 45 percent galena

I jn. of I f5) vawx* sphalerite

I 10 percent chalcopyrite 

I minor tetrahedrit {

70 percent sphalerite 

20 percent galena 

10 percent chalcopyrite 

minor tetrahedrite

% in. of quartz, pyrite, 

and chalcopyrite EXPLANATION

1 cuts 2l 2, 

2 cuts 3, 4, and 5 > 

5 cuts 3j

3 in. of galena and chalcopyrite and 12 in. of 

disseminated pyrite and 

chalcopyrite on footwall

{ 2 in. galena and chalcopyrite 

2 in. chalcopyrite and sphalerite

i. chalcopyrite and sphalerite

i. galena

i. chalcopyrite and sphalerite

3 in of disseminated quartz, pyrite, 

and chalcopyrite on hanging wall 

2 in. of quartz and chalcopyrite

[85 percent galena 

o Pn nf J10 percent sphalerite 

" i 5 percent chalcopyrite

i. minor tetrahedrite 

2 in. of quartz and chalcopyrite 

Footwall

« - " .. 

Vein, dashed where inferred. 

Letter refers to corresponding 

in in plate 11

Timbered workings

Disseminated quartz, pyrite, and 

chalcopyrite with small amounts 

of galena and sphalerite

4TH LEVEL

Elev 9152 ft

Geology by J. E, Harjison, 1952

Datum is mean sea level

FIGURE 26. Vertical section through the Turner underground shaft.

blocks have moved down and to the northeast relative to the southeast 

blocks. The total amount of movement could not be determined 

accurately, but it appears to be only a few feet both horizontally and 

vertically.

The principal ore shoot below the tunnel level plunges about 28° N. 

30° E. The shoot structure has resulted from a combination of strikeslip and dip-slip movement along a cymoid-shaped fracture zone. 

Paragenetic relations suggest that the first movement was principally 

strike-slip and was followed by quartz-pyrite-chalcopyrite mineralization. The second movement resulted principally in dip-slip and was 

followed by the main galena-sphalerite mineralization. Minerals of 

both ore stages have been brecciated and recemented by chalcedonic 

quartz indicating that minor postmineralization movements took place.

An undiscovered ore body may be present some few feet out in the 

hanging wall between the second and third levels. The veins b and c 

split off from the main vein system and enter the hanging wall at the 

second level (fig. 26). Cross fractures having disseminated ore between 

them and containing thin ore streaks occur between the second and 

third levels and extend a short distance below the third level. Such
FREELANI*-LAMARTINE DISTRICT, CLEAR CREEK COUNTY 121

EXPLANATION

Migmatite

A pod of disseminated pyrite 

and granite with limonite 

2 ft by 2.5 ft by 8 in.

4 in. shear zone

2 in. of limonite

Contact, dashed where inferred

^45

Fault, showing dip; dashed where 

approximately located

85

Strike and dip of foliation 

38 10

Strike and dip of foliation 

and plunge of lineation

Vein, showing dip; dashed where 

approximately located

1 in. of disseminated 

pyrite and quartz 

with limonite

Geology by J. D. Wells, 1952

150 Feet

_I

Datum is mean sea level 

FIGTJEE 27. Geologic map of the West London tunnel.

disseminations of ore and mineralized fractures characteristically 

appear only between two mineralized veins in the mine. As the strong 

change in dip on the main vein system, and consequently the thickest 

part of the galena ore body, occurs just below the second level, the 

possibility exists that veins b and c also have a prominent dip change 

out in the hanging wall and may, consequently, contain thicker ore.

WEST LONDON TUNNEL

The West London tunnel is about 6,100 feet west of the abandoned 

town of Freeland, at an altitude of 9,580 feet. The portal is about 100 

feet north of the westernmost switchback on the Trail Creek road 

(pl. 5).

The mine workings consist of a 209-foot drift on one vein and a 20- 

foot drift on a cross vein (fig. 27). No stoping has been done in the 

mine.

The wall rock is granite gneiss and pegmatite, and migmatite. The 

foliation has an average strike of N. 20° E. and a dip from 38° to 85° 

NW.

The vein exposed in the tunnel is a weakly mineralized fracture that 

strikes N. 55° W. and dips about 80° N. The cross vein is also weakly
122 GEOLOGY AND ORE DEPOSITS, COLORADO

mineralized and has an attitude of N. 45° E., 70° N. Both veins 

consist of an inch or less of quartz and py ite. A small pod of quartz 

and pyrite occurs at the intersection of the veins.

No record of production from the West London tunnel could be 

found.

SMALL INACCESSIBLE MINES AND PROSPECTS

The district contains many small inaccessible mines and prospects. 

No production information could be found for any of these workings. 

The information that could be gathered on the more important of these 

mines is given in table 10.
TABLE 10. Data on small inaccessible mines an

Mine 

no. 

(Pi. 5)

63

54

72

18

49

48

43

47

20

40

23

41

64

68

Mine name

O.M.Welch-. .........

Ethel . 

Falu ... 

TVTammnt.h

Mint... -

Type of surface opening

Tunnel ..

 do. . 

Tunnel

tunnel.

do

-....do.. -. ..........

Shaft . 

do

.... .do-..... ...

tunnel.

Shaft 

Probable vein explored

Split off Miller vein ...

Crazy Girl __ -

Ore minerals identified 

on dump

Pyrite 

__ do ______ ....

 do .... ... ... ...

do.

 do.....--.-.-.-....

copyrite, sphalerite.

eopyrite, sphalerite.

copyrite.
124 GEOLOGY AND ORE DEPOSITS, COLORADO

LITERATURE CITED

Balk, Robert, 1937, Structural behavior of igneous rocks: Geol. Soc. America

Mem. 5. 

Ball, S. EL, 1906, Pre-Cambrian rocks of the Georgetown quadrangle, Colo.: Am.

Jour. Sci., 4th ser., v. 21, p. 371-389. 

Bastin, E. S., and Hill, J. M., 1917, Economic geology of Gilpin County and

adjacent parts of Clear Creek and Boulder Counties, Colo.: U. S. Geol.

Survey Prof. Paper 94. 

Bastin, E. S., and others, 1931, Criteria of age relations of minerals: Econ.

Geology, v. 26, p. 561-610. 

Cloos, Hans, 1933, Plutone und ihre Stellung in Rahmen der Krusten bewegungen:

Internat. Geol. Congress, 16th sess., United States 1933, v. 1, p. 235-253. 

Emmons, H. E., 1940, Principles of economic geology: 2d ed., New York, McGrawHill. 

Fleischer, Michael, 1937, The relation between chemical composition and physical

properties in the garnet group: Am. Mineralogist, v. 22, p. 751-759. 

Goddard, E. N., 1947, Summaries of mining districts and mineral deposits, in

Mineral Resources of Colorado: Denver, Colo. Min. Res. Board. 

Holmes, Arthur, 1946, The construction of a geological time-scale: Geol. Soc.

Glasgow Trans., v. 21, pt. 1, p. 117-152. 

Levin, S. B., 1950, Genesis of some Adirondack garnet deposits; Geol. Soc.

America Bull., v. 61, p. 519-565. 

Lovering, T. S., and Goddard, E. N., 1950, Geology and ore deposits of the Front

Range, Colo.: U. S. Geol. Survey Prof. Paper 223.

MeKinstry, H. E., 1948, Mining geology: New York, Prentice-Hall, Inc. 

Newhouse, W. H., 1940, Openings due to movement along a curved or irregular

fault plane: Econ. Geology, v. 35, p. 445-464.

 1942, Structural features associated with ore deposits, in W. H. Newhouse, 

ed., Ore deposits as related to structural features.: Princeton, Princeton Univ. 

Press, p. 11-15.

Phair, George, 1952, Radioactive Tertiary porphyries in the Central City 

district, Colo., and their bearing on pitchblende deposition: U. S. Geol. 

Survey Trace Elements Inv. Rept. 247, U. S. Atomic Energy Tech. Inf. 

Service, Oak Ridge, Tenn.

Spurr, J. E., Garrey, G. H., and Ball, S. H., 1908, Economic geology of the Georgetown quadrangle, Colo.: U. S. Geol. Survey Prof. Paper 63.

Turner, F. J., 1948, Mineralogical and structural evolution of the metamorphic 

rocks: Geol. Soc. America Mem. 30.

 1951, Observations on twinning of plagioclase in metamorphic rocks:

Am. Mineralogist, v. 36, p. 581-589. 

Vanderwilt, J. W., 1947, Metals, nonmetals, and fuels, in Mineral Resources of

Colorado: Denver, Colo. Min. Res. Board. 

Wells, J. D., and Harrison, J. E., 1954, Radioactivity reconnaissance of part of

north-central Clear Creek County, Front Range, Colo.: U. S. Geol. Survey

Giro. 345.
INDEX

A Page

Abstract ___________________ 33-34

Acknowledgments________________ 36

Alabama mine....__._____..___ 123; pi. 5

Alaskite porphyry, color____..._____ 59,60

exposures_ ___ __ _____ 59

radioactivity..______________ 60

structure.-. ___ ___ _____ 60

texture________-___________ 59-60

Alluvium, occurrence__--___________ 62

Amphibolite, color_______________ 41

exposures. _-___.___..._____ 41

origin____.___._____._____ 44

structure._________________ 41-42

texture-__________________ 41

twinning of plagioclase feldspars_____ 47

Anchor mine-.---.-__________ 123; pi. 5

Anchor vein__.____-...__._____ 98,99

Apatite, in amphibolite____________ 42

in biotite-muscovite granite_______ 55

in biotite-quartz gneiss..___._____ 39

in hornblendite______________ 46

in lime silicate gneiss. __________ 43

in quartz diorite_ _ __..__ 46

Ariadne Extension mine- _________ 123; pi. 5

Ariadne mine__ -_________ 79,80,87-88; pi. 5

Avalanche deposits, age...__._.._____ 62

occurrences________________ 62

Avalanche mine_____-_______ 88-89; pi. 5

B

Baltimore mine_____________ 89-90; pi. 5 

Belle Creole tunnel-- 79,80,90-91: pi. 5

Bell of the West tunnel-- 80,91,92; pi. 5

Biotite, in amphibolite____________ 42

in biotite-muscovite granite________ 55

in biotite-quartz gneiss _________ 39,40

in granite gneiss and pegmatite. _____ 51,52

in hornblendite_______________ 46

in quartz diorite______________ 46

in sillimanitic biotite-quartz gneiss____ 41

Biotite-muscovite granite, color_._____ 55

contact with other rock units_______ 54

exposures-_____.___.._____ 54

minerals, accessory.-____.._____ 55

principal.--_______________ 55

origin.-..______.___ ........_ 56

radioactivity..______________ 56 

structure--__________________ 54-55 

texture-____________________ 55 

Biotite-quartz gneiss, color___.._ .. 39 

composition. _________________ 39-40 

contact withotherrockunits _______ 39 

exposures_________________ 38 

minerals, accessory----- .. .. 39

principal._.__._-_.__.__ 39 

origin..------------__ . ._ 43-44

structure--------- ____________ 39,40

texture.--------______________ 39,40

Page 

Brazil mine........_ .......... 79,80,91-92; pi. 5

Brighton mine..- 93,94; pi. 5

0. M. Welch mine -_________ 123; pi. 5 

Oalcite, in amphibolite------ _ 42

Olinopyroxene, in amphibolite___ . 42

in lime silicate gneiss. 43

Crazy Girl mine.._ _. 79,81,93-96;pi. 5

D

Diamond Mountain mine.__ -.79,81,96-98; pis. 5,6

E

Economic geology, general-__--.. 73

Epidote, in amphibolite_ 42

in biotite-quartz gneiss.----_ 39

in granite gneiss and pegmatite. 51

in hornblendite_ 46

in lime silicate gneiss_ 43

in quartz diorite.----. 46

Ethel mine- - 123; pi. 5

Etruria mine _-__ 123; pi. 5

F

Falcon mine. 79,81,102,103; pi 5 

Falu mine-__-___-__-- - 123; pi 5 

Faults, description.-. 65-67

sequence -__ 67-70 

Folds, age relations.. . 65

description.. .. ....... 63-65

Freeland group of mines... _ .. 98-100; pis. 5,7

Q

Garnet, in biotite-quartz gneiss... 39,40 

in syenitic bostonite porphyry 61 

Giant Warrior mine..-- . 123; pi. 5 

Gneiss. See Biotite-quartz gneiss; Sillimanitic 

biotite-quartz gneiss; Lime silicate gneiss; 

Granite gneiss and pegmatite. 

Golden Eod mine-____ 100; pi. 5 

Granite. See Granite gneiss and pegmatite; 

Biotite-muscovite granite; Granite pegmatite.

Granite gneiss and pegmatite, color 50 

composition 50,51 

contact with other rock units. 50 

exposures.... 50 

minerals, accessory.. 50 

principal___.__ 50 

origin-. -..-. . - 53 

structure- 51-53 

texture--.... 50-51 

Granite pegmatite, color__ . 57 

exposures___ - 56 

origin__... 57 

structure.... 57 

texture.- - 57

125
126 INDEX

Qranodiorite, colorexposures.......

origin_____ 

texture.___ 

Page

54

63

54

54

Harrisburg mine - .. 79, 81, 94,100-101; pi. 5

Hematite, in sillimanitic biotite-quartz gneiss. 41

History of the area..._____________ 36

Hornblende, in amphibolite..________ 42

in hornblendite______________ 46

in lime silicate gneiss..___________ 43

in quartz diorite_______________ 46

Hornblendite, accessory minerals_______ 46

color____________________ 46

origin.. .....______. 48

structure._________________ 46-47

texture-____________________ 46

twinning of plagioclase feldspars. ____ 47

See also Quartz diorite.

Hypogene zoning, effect of topography.. _ __ 86 

general.-___________________ 85-86 

longitudinal zoning_____________ 86 

vertical zoning________________ 86-87

Idaho Springs formation, named by..____ 37 

origin ...__..__. 43 

rock units, lithologic naming..-______ 38 

See also Biotite-quartz gneiss; Sillimanitic 

biotite-quartz gneiss; Amphibolite; Lime 

silicate gneiss. 

Invincible mine_.____________ 101; pi. 5

Joints, general__________________ 70 

regional pattern.-. _ - ___________ 70-73

Lamartine mine_______ 79, 81,101-106; pis. 5, 8 

Lanagan mine. See Diamond Mountain mine. 

Lime silicate gneiss, color____________ 42 

composition________________ 43 

exposures__.______________ 42 

origin._ .. .. __________ 44-45 

structure___-_______________ 43 

texture. . _ __.___ 42 

Little Johnie group of mines. 79, 81-82,106-110; pi. 5 

Location, Freeland-Lamaratine mining district. ... __ _... 34,35 

Lone Tree mine.______... 79, 82, 110-112; pi. 5

M

Magnetite, in amphibolite_________ 42

in biotite-muscovite granite____.-___ 55

in biotite-quartz gneiss.-_________ 39,40

in granite gneiss and pegmatite. ...__ 51

in hornblendite-__-___________ 46

inlime silicate gneiss....._.__..._.. 43

in quartz diorite______________ 46

in sillimanitic biotite-quartz gneiss..___ 41

Mammoth mine..._________ 79, 82,123; pi. 5

Mary Ann mine.._.__._______ 123; pi. 5

Page

Mendick mine. . 112-113; pi. 5

Microcline, in biotite-muscovite granite . 55

to biotite-quartz gneiss..____ .-. . 39

in grani te gneiss and pegmatite.. _. 51,52

in sillimanitic biotite-quartz gneiss. _ 41

Migmatite, composition___...._ ..... 49

contact with other rock units__ ... 49-50 

definition.... .. _ ... 49

exposures_ ........_ . 49

origin........ ... 50

Miller mine. .._ 79,82,113-114: pis. 5,9 

Mines and prospects, inaccessible_ .... 123

Mines and prospects:

Alabama mine.____________ 123; pi. 5 

Anchor mine. . 123; pi. 5 

Ariadne Extension mine_.__ .. 123; pi. 5 

Ariadne mine.________- 79,80,87-88; pi. 5 

Avalanche mine...___..__ 88-89; pi. 5 

Baltimore mine.__-_____-.- 89-90; pi. 5 

Belle Creole tunnel.- . 79,80,90-91; pi. 5 

Bell of the West tunnel-__ ... 80,91,92; pi. 5 

Brazil mine.______.___ 79,80,91-92; pi. 5 

Brighton mine._____.. ... 93,94; pi. 5 

C. W. Welch mine 123; pi. 5

Crazy Girl mine - 79,81,93-96; pi. 5 

Diamond Mountain mine.. 79,81,96-98; pis. 5,6 

Ethel mine. _________.____ 123; pi. 5 

Etruriamine.____. . 123; pi. 5 

Falumine. _______________ 123; pi. 5 

Falcon mine. __. . . 79,81; pi. 5 

Freeland group of mines.. ___ 98-100; pis. 5,7 

Giant Warrior mine- _________ 123; pi. 5 

Golden Eod mine...__ _- 100; pi. 5 

Harrisburg mine.. . 79,81,94,100-101; pi. 5 

Invincible mine______._.. 101; pi. 5 

Lamartine mine.____ 79,81,101-106; pis. 5,8 

Little Johnie group of mines. . 79, 

81-82,106-110; pi. 5

Lone Tree mine... 79,82,110-112; pi. 5 

Mammoth mine._____ 79,82,123; pi. 5 

Mary Ann mine._____-___ 123; pi. 5 

Mendick mine - 112-113; pi. 5

Miller mine 79,82,113-114; pis. 5,9

Mintmine-._____________ 123; pi. 5 

New Era mine.__.___ 83,114-117; pis. 5,10 

Old Stag tunnel 79,81,83,101,104,105; pis. 2, 5 

Poor Man mine._.______ 79,82,117; pi. 5 

Shermanmine_______-___ 123; pi. 5 

Silver Link mine. 117-118; pi. 5

Teller mine . ... 111, 118: pi. 5

Trembath mine ._. ... . 123; pi. 5

Turner mine.-__..--__ 83,118-121; pis. 5,11

West Alabama mine.. 123; pi. 5

West London tunnel. . 121-122; pi. 5

Yankee Girl mine.. ... 123; pi. 5

Mint mine.,._____--___ __ - 123; pi. 5

Monazite, in biotite-muscovite granite... 55, 56

Muscovite, in biotite-muscovite granite 55, 56

in biotite-quartz gneiss.-. 39

in granite gneiss and pegmatite 51, 53

in sillimanitic biotite-quartz gneiss.._-..- 41

N 

New Era mine- .______ 83,114-117; pis. 5,10
INDEX 127

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Old Stag tunnel. - 79, 81, 83,101,104,105; pis. 2, 5

Ore deposits, effective depths for... 85 

localization -.. - 83-85

Ore minerals, primary_ 76-78 

principal ones from district . 73 

secondary, 78'

Ore production from district__ 74

Pegmatite. See Granite gneiss and pegmatite;

Granite pegmatite.

Plagioclase, in amphibolite- . 42 

in biotite-muscovite granite-- -- 55 

in biotite-quartz gneiss.. 39 

in granite gneiss and pegmatite. _ 51, 52 

in hornblendite_____-_ _-.- 46 

in lime silicate gneiss 43 

in quartz diorite-____-__------ 46

in sillimanitic biotite-quartz gneiss... . 41 

Poor Man mine___________ 79, 82,117; pi. 5 

Porphyritic rocks. See Quartz monzonite porphyry; 

Alaskite porphyry; Syenitic bostonite porphyry; Quartz bostonite.

Pre-Cambrian rocks, general__ 37-38 

Previous work in district-_____...__.... 36

Pyroxene, in hornblendite 46 

in quartz diorite___- ... 46

Q

Quartz, in amphibolite-.-----__ _ 42 

in biotite-mttseovite granite_______ 55 

in biotite-quartz gneiss.._________ 39 

in granite gneiss and pegmatite__, __ 51, 52 

in hornblendite________._____ 46 

in quartz diorite___ -_____ ___ 46 

in sillimanitic biotite-quartz gneiss..._. 41

Quartz bostonite, nonporphyritic _____ 61 

porphyritic______....__-______ 61 

radioactivity..______________ 61

Quartz diorite, accessory minerals....__ 45 

age-. . . . -----.-. 45 

associated hornblendite___. ______ 45-47 

color______________________ 45 

origin...________.__________ 48 

structure-_______________.___ 45, 46 

texture..___________________ 45 

twinning of plagioclase feldspars_____ 47

Quartz monzonite porphyry, color..__.-._ 59 

exposures__________________ 

radioactivity...______________ 59 

structure..__________________ 59 

texture..________________... 59

Quaternary deposits, general-...__.___ 61-62

R

Radioactivity, abnormal.-._________ 80-82 

assay data, condensed._..___-..._ 79

Shermanmine__ .-_ . __ 123; pi. 5 

Sillimanite, in biotite-quartz gneiss __ 39 

in granite gneiss and pegmatite ____ 51 

in sillimanitic biotite-quartz gneiss... __ 41 

Sillimanitic biotite-quartz gneiss, exposures_ 40 

minerals, accessory..___.__..____ 40 

principal-..--.-_...__...____ 40 

origin.. .. __ . __ 44 

structure-_________-________ 41 

texture-____ _______-_____ 40 

Silver Link mine.-- .__- 117-118; pi. 5 

Slump deposits, age--.__-____-____ 62 

composition__ .. .._ __.. 62 

occurrences________________ 62 

Spbene, in amphibolite____________ 42 

in granite gneiss and pegmatite______ 51 

in hornblendite_______________ 46 

in lime silicate gneiss. _________ 43 

in quartz diorite_______________ 46 

in sillimam'tic biotite-quartz gneiss.. __ 41 

Spurr, J. E., Garrey, G. H., and Ball, S. H.,

quoted.._________________ 102,105

Structural history, general___________ 62-63

Syenitic bostonite porphyry, color______ 60

exposures___..___....__..___. 60

radioactivity_______________ 58,61

structure...__..-__ -....- _... 60-61

texture____________________ 60

Teller mine __- 111, 118; pi. 5

Tertiary intrusive rocks, classification____ 58-59 

general... . . __ 57-58 

Trembath mine..__ ___ _..__ 123; pi. 5 

Turner, F. J., quoted______________ 48 

Turner mine_._ __ - 83,118-121; pis. 5,11

Veins, deflections in dip...------,________ 83-84

deflections in strike.. ____________ 83 

fault deflections..-_____________ 84-85 

intersections________________ 83

major.____________________ 68 

mineralogy....- . _ _, 75-76

Vein types, classification...-_________ 74-75

W

Wall-rock alteration- ______________ 82-83 

West Alabama mine __-_______ 123; pi. 5 

West London tunnel -.-___.__ 121-122; pi. 5

Yankee Girl mine______________ 123; pi. 5 

Z

Zircon, in biotite-muscovite granitein biotite-quartz gneiss___. 

in granite gneiss and pegmatite.

39

51

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