Pegmatites of the 

Crystal Mountain 

District, Larimer 

County, Colorado

GEOLOGICAL SURVEY BULLETIN 1011

Pegmatites of the 

Crystal Mountain 

District, Larimer 

County, Colorado

By WILLIAM R. THURSTON

GEOLOGICAL SURVEY BULLETIN 1011

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 : 1955
&°\

UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

For sale by the Superintendent of Documents, (7. S. GOFernment Printing Office 

Washington 25, D. C.
CONTENTS

F»f«

Abstract...________^---_-____--___-----.-------------------------- 1

Introduction. _ ___________________------_-----------_-_---------.__ 2

Description of the area.---------------------------------------- 2'

History of mining-_-_--___--__-----------.----__-----------_-_ 4

Previous work___.-_._.______--____-____________-______-.-.-_ 4

Fieldwork and acknowledgments .--_.-._.-_-...____..-.-__-__ 6

Geology--.-----------.---- - 7

Summary of the geologic history of the Front Range.-___________-- 7

Geology of the Crystal Mountain district----------------..---.--- 8

Country rocks ______-_---__--_-.------------__-__--._--_ 9

Schist..__-------- .- ... ------- 9

Granite--..--.,____------_--_---_-_-----_--__-.--_--- 14

Diorite.____-_-_-___-_-___---__--------------.--_-__-_ 16

Surficial deposits.--.------------------..-------------- 16

Structure. ._-.__--__.-_-.___----_-__-._-__._>.--____.-._.-_ 16

Pegmatites.---.--.----------- .-.-. ---... .......-...._ 18

Distribution _._-___.___.-____.__-.-_-------_-----------_--_.__ 18

Shape and structure of pegmatites.._ .-------------------_--._ 18

Textures..------------------___._-_-_.__-------_.-_.- 20

Internal structure of zoned pegmatites.-__--_-___-___-___-_-___-_ 23

Fracture fillings...---------------------------------------- 23

Replacement bodies.----------------------.---------------. 24

Zones..-------.---------.-.--_----.-----.-.----.--_---_-- 24

Border zones___---_-_-___-______-_---_-_-___--_-._-- 24

Wall zones__.____ .. __--..___.-. 26

Intermediate zones._____-_-__-__-_-_-_--._-___-_---_._ 26

Cores..____------____-..--_-__-.__.._-__.-. 26

Telescoped zones-------__--__-----------_--_-------------- 27

Shoot.____._____..-.._..... ...-_....._.. 27

Homogeneous pegmatites._-__-_-___-_--_--_----_---_----_-----. 28

Multiple pegmatites____-.-.__----_--------_----_----_-.-_..-_ 30

Banded pegmatites_--_._._._..____-_.___.___....__.._..__._.._ 30

Mineralogy------__-_-__-_-_-___-------_----_----------_----_- 31

Mineralogic types of pegmatites.____________________________ 32

Feldspar-rich pegmatites------___-_--------_-_--_--_-_- 35

Quartz-rich pegmatites.__.__-_--------.--._-_---_.___-_ 35

Tourmaline-rich pegmatites...--___--__-___-__-_--__-.__ 36

Descriptions of minerals.-__-----------_---_-_-_-_----__---_ 36

Perthite_.-.-._.._...___-..__._.-.-..._.-...-_...... 37

Microcline..______._.__;____-_____...____.___________. 38

Plagioclase_._____._.__-___-_______-____._____.__-_._ 38

Quartz.:_______________________.-_.._._-_._.__.l._.a_ 40

Muscovite and biotite--_----_-----_-_-._.___.__.___.___ 41

Tourmaline.-_--__-_---_-_----_--_----_-__-_-.-_._-__. 42

Beryl.--_---.-.---.-.---------------.--_----.-----... 43

Garnet.---_---------_-_-_-----_-__---_--------_-__--_ 47

Apatite_---__---__-_---_-_-----___---_____-_____--__ 49

Sillimanite.. - _________-----_-_-___-___-___-__._.-_____ 49
JV CONTENTS

Pegmatites Continued

Mineralogy Continued

Description of minerals Continued

Lithiophilite-triphylite. _____________________ __________ 49

Columbite-tantalite__-_-_-----_----____--._____________ 50

: Bismuthinite________________________________________ 50

Uraninite and related minerals__________________________ 51

Relict spodumene__-______________________'___________ 52

Hematite and magnetite..______________________________ 52

Chrysoberyl. __________________________________________ 52

Miarolitic minerals-_---_-_---_-__--___---_-__--_-__--_ 53

Relation of pegmatites to wall rocks and structures________________ 54

Wall-rock alteration___-__--_---_-_--__-__------_-_-_-----. 54

Control by wall-rock structures..____.___-_____-_____.___.__. 56

Pegmatites concordant with schistosity.__________________ 56

Pegmatites discordant to schistosity_____________________ 56

Pegmatites filling joints in granite_______________________ 57

Pegmatites parallel to flow structure_--_-_--_-___________ 57

Amoeboid pegmatites in granite____________.____________ 58

Control by wall-rock mineralogy__.__---__-______---_______ 58

Minor elements in wall rocks-----_-_-----___---__-_.-_-__--_ 60

Age relations of pegmatites_________________________________ 63

Origin.._ _____________________-_--_--_____-___-___-_-_._____-_ 63

Mineral resources of the Crystal Mountain district___________________ 68

Descriptions of individual pegmatites ________________________________ 70

Deposits explored by core drilling..._____________________________ 71

Hyatt pegmatitei_-_____---_---_-_---_--__-_-___-_-___--__ 71

Geology____________.____.___________._ 72

Exploration.__ ______-___--__-___-_-_-_-___-__--_____-_ 82

Mineral deposits...____________________________________ 87

Big Boulder prospect_-___---__--_-_____-___________________ 88

Geology-_-_________-_-_--____-_--__-___-_-__-________ 88

Exploration.._ ________________________________________ 92

Mineral deposits___._- .-_____._._-_-_-_---------- 92

Buckhorn Mica mine___. __.--._.-_-.._-_-.--.--.-.---- 96

Geology... _________ _____________________ _ _ _ _ 98

Exploration. __________________________________________ 105 Mineral deposits......-..-.---------------------------- 106

Selected bibliography._____________________________________________ 111

Appendix A Logs of drill holes------------------------------------- 114

Appendix B Mineralogy of pegmatites.----------------------------- 130

Index.___________________________________________________________ 181

ILLUSTRATIONS

[Plates 1-13 are in pocket]

PLATE 1. Index map of the United States, showing 'locations of principal

pegmatite mining districts.

2. Geologic map of the Hyatt area

3. Geologic cross sections of the Hyatt area

4. Pegmatites discordant in schist, Hyatt area

5. Index map to pegmatites in the Hyatt area

6. Distribution of omega indices of beryl in Hyatt area

7. Distribution of beryl-bearing pegmatites in the Hyatt area
CONTENTS V

PLATE 8. Shapes and grain boundary relationships of beryl and other minerals 

as observed in drill core.

9. Geologic map of the Hyatt pegmatite

10. Geologic cross sections of the Hyatt pegmatite

11. Geologic map of the Big Boulder prospect

12. Geologic cross sections of the Big Boulder prospect

13. Geologic map and cross sections of the Buckhorn Mica mine

Page 

FIGURE 1. Index map of the Crystal Mountain district, Colorado..__._ 3

2. Geologic map of the Big Boulder prospect area._-_-_-__._-_ 10

3. Geologic map of the Buckhorn Mica mine area...-_.----__. 11

4. Idealized plans of pegmatite bodies showing sequence of types

between homogeneous pegmatites and zoned pegmatites __ 29

5. Distribution of plagioclase indices. _-___-_-__-__----_-____ 39

6. Distribution of beryl indices--_-___---_-_____---.-_--_-__ 45

7. Plan of beryl grains exposed on diamond-drill core from hole

HY-1, Hyatt pegmatite_-___-_-_________---___-_--____- 74

8. Plan of beryl grains exposed on diamond-drill core from hole

HY-2, Hyatt pegmatite..._____________-._--_-_.._ 75

9. Plan of beryl grains exposed on diamond-drill core from hole

HY-3, Hyatt pegmatite.--..-.-....___-__---_---____ 76

10. Plan of beryl grains exposed on diamond-drill core from hole

HY-4, Hyatt pegmatite......_________________________ 77

11. Plan of beryl grains exposed on diamond-drill core from hole

HY-5, Hyatt pegmatite__________-___--___---._-._ 78

12. Plan of beryl grains exposed on diamond-drill core from hole

HY-6, Hyatt pegmatite_._________.___________________ 79

13. Assay plan of diamond-drill hole HY-1, Hyatt pegmatite.___ 83

14. Assay plan of diamond-drill hole HY-2, Hyatt pegmatite.... 84

15. Assay plan of diamond-drill hole HY-3, Hyatt pegmatite.... 85

16. Assay plan of diamond-drill holes HY-4 and HY-5, Hyatt

pegmatite- --__-_---_--_____.-__-_-___-___-___-_______ 86

17. Assay plan of diamond-drill hole HY-6, Hyatt pegmatite.... 87

18. Assay plan of diamond-drill hole BB-3, Big Boulder prospect. 93

19. Assay plan of diamond-drill hole BB-4, Big Boulder prospect. 94

20. Assay plan of diamond-drill hole BB-5, Big Boulder prospect. 95

21. Plan of beryl grains exposed on diamond-drill core from hole

BB-4, Big Boulder prospect.__________________________ 96

22. Plan of beryl grains exposed on diamond-drill core from hole

BB-5, Big Boulder prospect-.....-.._____-_.-_-_____-_ 97

23. Plan of beryl grains exposed on diamond-drill core from hole

BH-1, Buckhorn Mica mine...............--._-_-___._ 100

24. Plan of beryl grains exposed on diamond-drill core from hole

BH-2, Buckhorn Mica mine.__-__._-________..-__.-___ 101

25. Plan of beryl grains exposed on diamond-drill core from hole

BH-3, Buckhorn Mica mine.__________________________ 102

26. Plan of beryl grains exposed on diamond-drill core from hole

BH-4, Buckhorn Mica mine.._________________________ 103

27. Plan of beryl grains exposed on diamond-drill core from hole

BH-5, Buckhorn Mica mine_______________-___________ 104

28. Assay plan of diamond-drill hole BH-1, Buckhorn Mica mine. 106

29. Assay plan of diamond-drill hole BH-2, Buckhorn Mica mine. 107

30. Assay plan of diamond-drill hole BH-3, Buckhorn Mica mine. 108
VI CONTENTS

TABLES

Page

FIGURE 31. Assay plan of diamond-drill hole BH-4, Buckhorn Mica mine. 109 

32. Assay plan of diamond-drill hole BH-5, Buckhorn Mica mine_ 110 

TABLE 1. Pegmatite minerals produced in Crystal Mountain district,

Colorado._______-_-_-_-_.!._-_-_--_-__-____----_---_-_-_ 5

2. Grain sizes of three zoned pegmatites in Crystal Mountain

district, Colorado-..-- -_-_-_-_____---___---------_-__- 21

3. Comparison of changes in grain size in a zoned pegmatite and

homogeneous pegmatite, Crystal Mountain district, Colorado. 22

4. Pegmatites consisting of two zones, Hyatt area._---__-_______ 25

5. Mineralogic types of pegmatites in the Hyatt area.___________ 32

6. General sequence of mineral assemblages ____________________ 33

7. Distribution of beryl with respect to granite intrusives in Hyatt

area.___-_-_________-___---_-_-__--___-_--_------_--__ 46

8. Distribution of beryl-bearing pegmatites according to country

rock and structure._________________________--------_-__ 47

9. Approximate composition of garnet in Hyatt area.____________ 48

10. Quantitative spectographic analysis of sericite from the core of

the Hyatt pegmatite.______________________--------_-___ 53

11. BeO content of granite near Hyatt pegmatite._______________ 55

12. BeO content of schist near explored deposits, Crystal Mountain

district, Colorado--___---_-_---__-______-__------------_ 56

13. Semiquantitative spectrographic analyses of wall rock of explored deposits, Crystal Mountain district, Colorado.--.---. 61

14. BeO content of concealed zoned pegmatite «core in drill hole

BH-3, Crystal Mountain district, Colorado____--_________- 71

15. Analysis and norm of plagioclase-perthite-quartz pegmatite,

wall zone of Hyatt pegmatite____-___^_____-_---_--___--_ 80

16. Semiquantitative spectrography of plagioclase-perthite-quartz

pegmatite, wall zone o£ Hyatt pegmatite_____--___--__-_-. 81
PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, 

LARIMER COUNTY, COLORADO

"By WILLIAM R. THURSTON

ABSTRACT

The Front Range of Colorado is composed chiefly of schists of the Idaho 

Springs formation of pre-Cambrian age which have been intruded by a variety of 

granitic batholiths. In the Crystal Mountain district the Mount Olympus 

granite, a satellite of Fuller's Longs Peak batholith, forms sills and essentially 

concordant multiple intrusions in quartz-mica schist that dips southward at 

moderate to steep angles. A great number of pegmatites accompanied and 

followed the intrusion of the sills and formed concordant and discordant bodies 

in schist and granite.

More than 1,300 pegmatites in the Hyatt area north of the Big Thompson 

River are mapped and individually described. There are 27 pegmatites in the 

area that are made up of a wall zone and a core, and one, the pegmatite at the 

Hyatt mine, is composed of five zones. The largest pegmatites in the area are 

discordant in schist and occupy zones that are interpreted to be tear faults and 

tension fractures produced by the successive intrusion of granite that formed 

multiple sills. The majority of pegmatites in the large multiple sills were emplaced along the foliation and fractures.

The pegmatites were intruded over a period of time and probably were derived from a granitic magma at different stages during differentiation. Ninetysix percent of the pegmatites are granitic, 3.5 percent are quartz-rich pegmatites, 

and a few are tourmaline-rich. Solutions escaping from many of the pegmatites 

tourmalinized and silicified the wall rocks for a few inches to 2 feet, but chemical 

and spectrographic analyses fail to show the transport of any other constituents.

Perthite, plagioclase, and quartz are the essential minerals of the pegmatites, 

and muscovite is a minor but widespread constituent. Tourmaline, garnet, 

beryl, and apatite are common accessory minerals; and lithiophilite-triphylite, 

bismuthinite, uraninite, columbite-tantalite, and chrysoberyl are rare constituents. 

Beryl is found in 350 pegmatites, or 27 percent of the total, and makes up 0.01 

percent or more of 77 pegmatite bodies. The beryl-bearing pegmatites are 

richest in two of the three large granite masses, and are somewhat less rich at a 

distance of more than a thousand feet from the margins of the intrusives, but 

contain the least beryl in the thousand-foot belt immediately surrounding the 

intrusives. The Hyatt pegmatite * is by far the richest deposit of beryl in the 

area mapped.

Most of the pegmatites mapped are "unzoned" or homogeneous pegmatites of 

uniform texture and mineral distribution. All gradations are visible between 

homogeneous pegmatites and zoned pegmatites. The interpretation is made 

that, for most pegmatites, the initial composition determines whether or not zones 

will form. Pegmatites containing many zones can form from a magma composed 

of the elements in perthite, plagioclase, quartz, and muscovite, depending on the 

proportions of the components crystallizing at any given time. The complexly 

zoned deposits depend for their formation on the presence of several of the rarer

 The names of the pegmatites are purely economic terms and are not to be confused in any way with 

formal stratigraphic nomenclature.

1
2 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

elements, principally lithium. Replacement textures in zones result from the 

interaction of the rest-liquid with the earlier-formed solid crystals. No mappable 

pegmatite in the Crystal Mountain district formed from the replacement of preexisting pegmatite by solutions escaping from the rest-liquid, or by solutions 

originating outside the pegmatite.

Three beryl-bearing zoned pegmatites, the Hyatt, Big Boulder, and Buckhorn 

Mica deposits, were explored by core drilling. Each deposit is mapped and described in detail, and the mineral reserves are evaluated. The exploration indicates a total of 2,000 tons of beryl, of which 480 tons is estimated to be recoverable 

by hand sorting. The mapping of the 3% square miles in the Hyatt area indicates 

beryl in substantial additional resources.

Small tonnages of scrap mica and perthite may be obtained from the Hyatt 

and Big Boulder prospects, and columbite-tantalite may occur in sufficient 

amounts at the Buckhorn Mica mine and Tantalum claim to produce several 

hundred pounds as a byproduct of beryl mining. Dumps at the various deposits 

contain 25 to 50 tons of beryl.

INTRODUCTION

In mid-1942 the wartime demand for tantalum, mica, and beryl 

caused the United States Geological Survey to undertake a greatly 

expanded program of pegmatite investigations; and in the following 

2K years, work was done in most of the important pegmatite mining 

districts of the country. These studies entailed approximately 68 

man-years of work by 39 geologists (Cameron and others, 1949). 

The wartime investigations were focused on deposits containing minerals of strategic importance; limitations on time and manpower precluded examination of deposits not known to contain strategic minerals or study in detail of the regional relationships.

From 1946 to 1950, regional studies were made of the geology and 

beryl resources of 10 pegmatite districts. (See pi. 1.) The work included the preparation of detailed geologic maps of the districts, 

large-scale maps of individual pegmatites of unusual interest, sampling 

and diamond-drill exploration of selected deposits, and mineralogic 

studies. More emphasis was placed on regional investigations which 

included study of the country rock, structure, and economically unimportant pegmatites and their relation to deposits of economic interest. The study of the Crystal Mountain district, Larmier County, 

Colo., is but one phase of this post-World War II pegmatite program, 

in part carried out by the Geological Survey on behalf of the Division 

of Raw Materials of the Atomic Energy Commission.

DESCRIPTION OP THE AREA

The Crystal Mountain district is an unincorporated mining district 

without precise boundaries. In this report the name refers to an 

area north of the Big Thompson Kiver and south of Buckhorn Creek 

in Tps. 6 and 7 N., Ks. 71 and 72 W., sixth principal meridian. The 

district is in the Front Range of the Rocky Mountains, approximately
INTRODUCTION

16 miles west of Loveland and Fort Collins, Larimer County, Colo. 

The northern part of the district, near Crystal Mountain, is reached 

by way of unimproved ranch roads that branch southward from the 

Buckhorn Creek road at a bridge 21 miles west of the town of Masonville. (See fig. 1.) The Hyatt pegmatite area is reached by a private road which branches northward from the Glen Haven road at a 

bridge 500 yards west of the town of Drake. (See fig. 1.) The ranch 

roads and the Buckhorn Creek road may be closed for several weeks 

during severe winters. The road in the steep-walled parts of Buckhorn Creek is washed out occasionally by spring floods.

R. 72 W. R. 71 W.

UCKHORN 

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Masonville

FIOUEE 1. Index map of the Crystal Mountain district, Colorado

The topographic sheets which cover the district are the Livermore 

quadrangle for the northern part and the Mount Olympus quadrangle 

for the southern part. The lowest altitudes hi the Crystal Mountain 

district are 6,500 feet on Buckhorn Creek, which bounds the district 

to the north, and 6,100 feet on the Big Thompson River, which bounds 

it to the south. Rugged valley walls rise steeply from these streams 

for about 1,000 feet to a maturely dissected rolling upland. The 

highest points on the upland surface are Lookout Mountain (10,633 

feet), Crystal Mountain (9,952 feet), and Storm Mountain (9,915 

feet). Most of this area is thickly forested with conifers, principally 

lodgepole pine, but with some Ponderosa pine, blue and Engelmann
4 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

spruce, Douglas-fir, and various junipers. Cottonwood, aspenj boxelder, and chokecherry are found along the smaller intermittent 

streams. There are many small meadows bordered by aspen groves 

around Crystal Mountain; the Hyatt ranch occupies much of a large 

meadow called Cedar Park.

The principal economic activities in the area are lumbering and 

summer grazing. The Dickerson family, at a ranch in Box Prairie, 

and the Hyatt family, at a ranch in Cedar Park, were the only permanent residents during the time the fieldwork was in progress.

HISTORY OP MINING

Mining has never been an important activity in the region, though 

the area has been prospected for various commodities since frontier 

days. Gold mining and milling near Masonville, copper mining just 

east of the Crystal Mountain district, and various attempts to mine 

pegmatite minerals have been marginal to submarginal ventures. 

Scattered throughout the area are caved and weed-covered pits and 

trenches of unknown date.

The earliest recorded pegmatite mining in this district was at the 

Buckhorn Mica mine in 1884. It is reported that some time prior to 

1900 the Crystal Silica deposit was opened. In 1913 the district was 

visited by Sterrett (1923, p. 59-61) who described the Buckhorn Mica 

mine and "another mica prospect [which] was opened by Parkson and 

Kitchen about a quarter of a mile west of the Buckhorn mine"; the 

unnamed deposit may be the one known now as the Double Opening 

prospect. A claim to the Double Opening prospect was filed in 1934. 

The Big Boulder prospect and the Hyatt pegmatite were opened in 

1936. About a dozen other pegmatite deposits have been prpspected, 

but little or no development work has been done; four of them have 

been described by Hanley, Hemrich, and Page (1950). Since completion of the wartime studies in 1945, the only production has come 

from ike Hyatt pegmatite in 1948. The production record, insofar 

as it is known, is compiled in table 1.

The geology of the Front Range area of Colorado has been studied

because of its many metallic ore deposits and their relation to regional 

structure and stratigraphy. Burbank and Levering (1933, p, 272-

311) summarize the general geology of Colorado and part of Wyoming

and list the principal references, In an earlier paper, Levering (1929)

describes the geologic history of the Front Range. Pegmatite deposits 

are not considered, nor are there maps or descriptions Which glV6 the 

relations in the Crystal Mountain district, The reports on the 

Georgetown quadrangle by Ball (1908), the Montezuma quadrangle
INTRODUCTION

TABLE 1. Pegmatite minerals produced in Crystal Mountain district, Colorado

Property and location

Hyatt mine, NEJ4NWH sec. 28, T. 6 N.,

R. 71 W.

Buckhorn Mica mine, SWH sec. 29, T. 7 N.,

R. 71 W.

Big Boulder prospect, SEJi sec. 36, T. 7 N.,

R. 72 W.

Crystal Silica claims, sec. 26, T. 7 N., R.

72 W.

Total recorded production ............

Commodity produced

Beryl............. ..........

.....do...... ._._..-........_.

.....do.......................

Sheet mica ___ . ..........

Beryl __ ...... _______

__ do _ ..... _ . ...........

.....do ......... ... .....

.....do.......................

Bismuth minerals ...........

Fusing quartz ...............

Beryl _____ . ............

Potash spar _ .. ...........

Scrap mica ..................

Amount

Pounds 

1,600

Tons 

34

14

400

Oft

180 (')

Tons 2-3

1

10.5

Pounds

fiflO

Tons 

62.8

400

. 210

Date

1936-42

1043

1048

1948

1948

1884-1942

1884-1942

1884-1944

1944-60

1936

1941

Prior to 1900

1884-1960

1948

1884-1948

' A few hundred pounds.

by Levering (1935), and the Front Range generally by Lovering and 

Goddard (1950) contain abundant information on the schist, granite, 

and pegmatities of those areas that are helpful in studying similar 

rocks in the Crystal Mountain district. The descriptions are detailed 

and precise, and comparisons can be made though the areas are 50 

miles apart.

A general map by Lovering (1935, pi. 5) shows the relationships in 

the area south of the Crystal Mountain district but ends at the southern boundary of the district. The features of the pre-Cambrian structure along the Big Thompson River described by Fuller (1924) and 

the observations on the granites of the Longs Peak-St. Vrain batholith 

by Boos and Boos (1934) are too generalized to be applicable to the 

detailed studies made in the Crystal Mountain district.

The first description of pegmatites in the Crystal Mountain district 

was made in 1913 by Sterrett (1923) in the course of an appraisal of 

mica deposits of the United States. Between September 21 and 

October 10, 1942, L. R. Page and J. B. Hanley mapped in detail 

about 20 beryl-bearing pegmatites at 9 properties in the district, 

including two described previously by Sterrett. Continued studies 

at the Hyatt pegmatite resulted in revision and remapping in 1943 

and 1944. The results of this work have been described by Hanley, 

Heinrich, and Page (1950, p. 86-103).

FIELDWORK AND ACKNOWLEDGMENTS

The field and laboratory work on which this report is based was 

begun in August 1947 and completed in December 1950. From
6 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

August to November 1947 the previously described deposits in the 

Crystal Mountain district were reexamined and five prospects were 

remapped with the assistance of A. J. Lang. As a result of this reexamination three beryl-rich pegmatites, the Hyatt, Big Boulder, 

and Buckhorn Mica deposits, were selected for exploration, and 

preparations were made during the winter for diamond drilling. 

The three deposits were core drilled between July 16 and November 7, 

1948, by the Fillmore Drilling Co., of Deadwood, S. Dak., for the 

Geological Survey. For 7 weeks A. E. Grass and E. V. Dedman were 

samplers under the supervision of W, I. Finch. For the remaining 

9 weeks the sampling was done by R. E. Roadifer and the writer. 

During July and August 1948, H. D. Wright mapped in the vicinity 

of the Hyatt pegmatite, and Wright and Finch mapped and studied 

45 pegmatites in the meadow north of the Hyatt ranch.

While core drilling was in progress, an area a quarter of a square 

mile surrounding the Big Boulder deposit was mapped, and an eighth 

of a square mile in the vicinity of the Buckhorn Mica mine was mapped. 

For 2 weeks the writer was assisted by C. S. Robinson. From October 

4 to November 5, 1948, W. R. Griffitts was associated with the project 

and mapped in the vicinity of the Big Boulder and Buckhorn Mica 

deposits. In the winter of 1948-49, 255 samples of drill core were 

prepared for analysis; the core data were studied and compiled. In 

1949 the Hyatt area was mapped on aerial photographs at a scale of 

1:6,000: a total of 12 man-months were spent by E. N. Hinrichs and 

the writer in mapping more than thirteen hundred pegmatites in 3% 

square miles.

The topographic maps of the district were of too small a scale for

detailed mapping, so aerial photographs were used. The geology 

was plotted in the field directly on United States Forest Service photographs enlarged to a scale of approximately 1:6,000. The topographic

relief in the Hyatt area is sufficient to require a contoured base map 

for the representation of the geology (pi. 2). The base was prepared 

from photographs of the area, using the Mahan Stereoscopic plotter. 2 

The WOrk Was done by John W. Zydik, of the Topographic Division 

of the Geological Survey, and" tke Writer. Vertical COBtfOl fOf Ofientaand contouring was obtained from a six-man altimeter survey

benchmarks. The writer is grateful to J. w. Adams, j. K. 

Stacy, A. F, Trites, Jr., and D. J. vames for tkdr kelp in making

this survey.

PlflJOijGQCtriC maps Were made directly from the photograph in the

small areas of low relief around tne Big BouluW prOSpfiCt (fig, 2), flfld

> Instrument and procedure are described in U. S. Geol. Survey, Topographic instructions: chap. 3 0 12 

[fn preparation].
INTRODUCTION 7

the Buckhom Mica mine (fig. 3). Distortion in the photograph has 

not been corrected, but it is probably not great.

Over 500 determinations were made of the indices of refraction of 

plagioclase and beryl from the pegmatites; studies were made of other 

minerals, and 55 thin sections were examined.

Special thanks are due the members of the Hyatt and Dickerson 

families for their courtesies and hospitality while the writer was

working near their homes.

GEOLOGY

The Crystal Mountain district is such a small part of the Front 

Range that studies within the district give little direct information 

on the regional setting. To understand the geologic details and discuss the problems within the district, the broader relations must be 

considered. Excellent summaries of the geology and history of the 

Front Range have been written by Lovering (1929) and Burbank and 

Lovering (1933, p. 272-316, especially p. 272-285). A condensation 

of geologic history of the pre-Cambrian is taken from these sources.

SUMMARY OF THE GEOLOGIC HISTORY OF THE FRONT RANGE

The Front Range is a mountainous uplift 30 to 35 miles wide and 

175 miles long, composed of pre-Cambrian metamorphic and igneous 

rocks, cut locally by Tertiary intrusive rocks. Paleozoic and younger 

sedimentary formations are upturned along the flanks of the range. 

The metamorphic rocks comprise a thick series of schists, gneisses, 

and greenstones; they were derived by dynamic and contact metamorphism from dominantly argillaceous and sandy sediments with 

intercalations of limy and pebbly beds, and probably some eruptive 

rocks. The schists grade from fine-grained quartz schist on the 

east through mica-quartz schist to biotite-sillimanite schist on the 

west. Lime silicate rocks and hornblende-rich rocks are minor components of the schists. Ball (1908, p. 37) gave the name Idaho 

Springs formation to the succession of metamorphic rocks in the 

Georgetown quadrangle, Colo. The name has been extended by 

common usage to include much of the schist of the Front Range, 

though the continuity of the formation from place to place has not 

been established. The metamorphic rocks along the Big Thompson 

River have been called the Big Thompson schist by Fuller (1924) 

and in the Coal Creek area have been divided into the Coal Creek 

quartzite and the Ralston schist by Adler. 3 The various units of the 

schist exposed along the Big Thompson River seem to be conformable.

The schists and gneisses of the Idaho Springs formation are cut by 

quartz monzonite gneiss, pegmatites, and hornblende-quartz diorite;

»Adler, Joseph, 1930, geologic relations of the Coal'Creekfquartzite inJColorado: unpublished thesis in 

flies of University of Chicago.
8 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

these are the oldest intrusives recognized in the Front Range. The 

schists and quartz monzonite gneiss are intruded by a series of granite 

batholiths and then- satellite stocks, pegmatites, and hornblendequartz diorite or gabbro bodies. The quartz-monzonite of preCambrian age of the Georgetown quadrangle is probably of the 

same age as the Boulder Creek granite gneiss of Boos and Boos to 

the east. The Pikes Peak granite of the central part of the Front 

Range in Colorado and the Sherman granite in the northern part of 

the Front Range in southern Wyoming are approximately contemporaneous according to Boos and Boos (1934, p. 307). The Silver Plume, 

Cripple Creek, and Longs Peak (of Fuller) granites are petrographically 

similar, are younger than the Pikes Peak and Sherman granites, and 

are probably contemporaneous with each other. The Mount Olympus 

granite has been designated by Boos and Boos (1934, p. 311 and 

323-324) as a satellite facies of the Longs Peak batholith. The granite 

intrusives are so related structurally and petrographically that, despite 

certain marked differences, Lovering (1929, p. 64) believes they 

belong to one great period of batholithic invasion. Maps by Lovering 

(1935, pi. 5) and Boos and Boos (1934, fig. 1) show the distribution 

of the main masses of the intrusives.

Van Hise and Leith (1909, p. 827) date the schists and gneisses as 

Archean, because their structural and lithologic complexity is similar 

to the "basal complex" of many other regions, and date the later 

quartzites and quartz schists as Algonkian. A tentative correlation 

of the Front Range rock units with the Lake Superior section was 

made by Lovering (1929, p. 74) on the basis of similarities in history 

when he stated that the Idaho Springs formation might be coiTelated 

with Lower and Middle Huronian, the Pikes Peak granite might be 

assigned to the early Algoman, and the Silver Plume and associated 

granites to the late Algoman all included in the Algonkian.

The structural grain of the pre-Cambrian rocks of the Front Range

trends generally east-west (Burbank and Lovering, 1933, p. 273,

p. 274, and fig. 11) and is bowed locally by the intrusion of batholithic 

raa.sses. During Paleozoic and MeSOZOlC time the main lines of deformation gradually rotated clockwise, culminating in the formation 

of a north-trending highland in the Front Range region during the

Laramide revolution. There are no important Paleozoic or younger 

rocks in the Crystal Mountain district.

GEOLOGY OF THE CRYSTAi, MOUNTA-in DISTB.XCT

Quartz-mica schists of the Idaho Springs formfttiflD. fllfi

rocks in the Crystal Mountain district and have been intruded by sills

of Mount Olympus granite and by pegmatites that are probably 

related to the granite babholith of Longs Peak. In the Hyatt area
i GEOLOGY OF THE CRYSTAL MOUNTAIN DISTRICT 9

(pi. 2) the schist is in open folds that have an average plunge of 60° S. 

and a general eastward strike. Most of the granite occurs in sheets 

which are essentially concordant with the foliation of the schist. The 

two largest granite masses, north and southwest of the Hyatt ranch, 

are multiple sills. Two smaller granite bodies, one almost surrounding 

the Hyatt pegmatite and the other about a thousand feet to the east, 

seem to be pluglike masses with southward plunging axes and almost 

circular horizontal sections, but the contacts are poorly exposed.

Around the Big Boulder prospect, the strike of the schist ranges 

from north to northeast (fig. 2), and the dip is eastward at steep angles; 

the plunge of linear structures is steep and to the southeast and south. 

The strike of the schist in the vicinity of the Buckhorn Mica mine 

(fig. 3) is about east-northeast, and the dip is steep and to the south. 

The mile of unmapped country between the two deposits has been 

traversed without observing unusual changes in structure so it may 

be inferred that the deposits are on the same broad fold; however, 

linear elements in the schist near the Buckhorn Mica mine plunge 

erratically, suggesting that between Big Boulder and Buckhorn Mica 

deposits there are concealed structural complexities.

Most of the thirteen hundred or more pegmatites mapped in the 

Hyatt area (pi. 2) are concordant, although about 30 of the largest 

pegmatites in the area are discordant, dipping northward at steep 

angles.

Most of the pegmatites in this area are feldspar-rich though some 

are quartz-rich and a few are tourmaline-rich. The dominant minerals 

of the pegmatites are, in order of abundance, perthite, plagioclase, 

and quartz. Muscovite is an everpresent minor constituent. Tourmaline is the commonest accessory mineral and the commonest mineral 

in the altered wall rock. Beryl and garnet are present in about 27 

percent of the pegmatites. The Hyatt pegmatite contains a varied 

suite of minerals, which are described separately.

SCHIST

The most common metamorphic rock in the Crystal Mountain 

district is quartz-mica schist of the Idaho Springs formation. It is 

fine to coarse grained; fresh surfaces are generally light gray and 

weathered outcrops are dark grayish brown. The facies of the formation range from quartz schist to mica schist, the types grading into 

each other by changes in the proportions of the dominant minerals, 

quartz, muscovite, and biotite. The schist is exposed on the steep 

valley walls in jagged irregular outcrops and on the flatter parts of 

the upland surface as widely scattered low mounds. In much of the 

area, outcrops are rare, except at the margins of pegmatites.
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12 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

The foliation of the schist is approximately parallel to the bedding 

in most places. Wherever recognizable bedding diverges from the 

foliation at an angle of more than 15°, it has been mapped separately 

(pi. 2). The linear structures of the schist include drag folds, ranging from minute crinkles to those 2 feet in cross section; elongation 

of mineral grains, principally biotite and quartz; and "pencil structure" produced by the intersection of closely spaced planes of fracture. 

The plunge of the linear elements, with few exceptions, is a reliable 

indicator of the attitude of the nearby fold.

The most abundant type of schist is characterized by the alternation of thin mica-rich and quartz-rich layers. Commonly, there 

are from 5 to 50 layers per inch; in places they are thicker. The color, 

composition, proportions of minerals, or grain size of layers may differ. 

Quartz, as grains with rounded outlines, is the most abundant mineral. 

Granulated and strained grains as well as grains with intricately 

sutured boundaries are rare. The proportions of biotite and muscovite vary widely. The biotite is coarser grained than the muscovite; 

some books are as much as 0.3 inch in diameter. Feldspar is not 

abundant, but in many layers it may constitute 5 to 15 percent of the 

granular material. Orthoclase, microcline, and plagioclase have been 

identified; orthoclase is the most common.

Tiny euhedral to subhedral crystals of apatite, zircon, and magnetite or ilmenite are present in all thin sections of schist that were 

examined. Chlorite, as large flakes and as felted masses of small 

shreds, is a common accessory. Staurolite, andalusite, and garnet 

are widely distributed throughout the quartz-mica schist but are 

rarely abundant. Staurolite crystals range from 0.02 to 1.1 inches 

in length; equant grains of andalusite range from 0.02 to 0.3 inch in 

diameter; and garnet crystals average 0.02 inch in size the largest is 

about 0.2 inch. Sillimanite is a rare accessory mineral in the Hyatt

area except in a few small lenticular beds west of the Hyatt ranch. 

Sillimanite needles, intergrown with quartz, are abundant in clumps 

which form white buttonlike masses in the mica schist. On Buckhorn

Creek sillimanite clusters, oriented with the long dimension parallel 

to the schistosity, are conspicuous in some outcrops. Mflppftblfi 

beds of staurolite-mica schist and garnet-mica schist occur in a few

places (pi. 2). Minor quantities of Staurolite, garnet, and other

accessory minerals are widespread in other types of schist in the 

Hyatt area. 

Small needles of black tourmaline are plentiful in some schist

layers, but quantitatively are a minor constituent. Tourmaline 

crystals as much as 1 inch long, however, are in the schist bordering 

some pegmatites. The tourmaline decreases in size and abundance
GEOLOGY OF THE CRYSTAL MOUNTAIN DISTRICT 13

away from the pegmatite borders, and the tourmalinized zone rarely 

exceeds 2 feet in thickness.

Textural facies of the quartz-mica schist are conspicuous in places. 

Several beds in the area are characterized by closely spaced, roughly 

ellipsoidal knots. The knots are from ^ to 1 inch in longest dimension, 

are oriented with the shortest dimension normal to the schistosity, and 

are compQsed of essentially the same minerals as the schist, though 

not necessarily in the same proportions. They are spaced irregularly, 

from Yz to 4 inches apart. In some exposures the folia of the schist 

seem to pass through the knots and in others to pass around the 

knots. The material composing the knots is not uniform, but it is 

always different from the enclosing schist. The component grains 

may be finer or coarser; they may be aggregated in a different manner; 

the proportions of minerals may be different, and invariably the 

knots weather differently. The knots have irregular boundaries, in 

some cases gradational. A thin section across several knots shows 

them to be composed almost entirely of medium-grained muscovite 

in flakes of random orientation; the surrounding schist is made up 

predominantly of fine- to medium-grained quartz, with subordinate 

quantities of fine-grained biotite, muscovite, and chlorite, and accessory magnetite, zircon, and apatite. The knots in another bed contain the same minerals as the schist (principally quartz, micas, chlorite, and staurolite), but the aggregate is outlined by a band rich in 

interstitial limonite, and the schistosity passes around the limonitic 

shell. Levering (1935, p. 7-8) describes a "knotted schist" in the 

Montezuma quadrangle which he likens to the schist with "ellipsoidal 

masses" described by Ball (1908, p. 41) and to the "pebble-bearing 

gneiss" of Spurr (Spurr, Garrey, and Ball, 1908, p. 177). Lovering 

states that the knots consist of medium-grained quartz with small 

amounts of sillimanite and attributes them to extreme metamorphism 

attended by the migration of siliceous and aluminous material. The 

knots in the sehist of the Hyatt area are more varied in composition 

but may be, nevertheless, the result of the migration of material 

during metamorphism; the muscovite in the knots may have been 

formed by retrograde metamorphism of original andalusite or sillimanite.

Quartz schist is less common than the quartz-mica schist, though 

the varieties are gradational and have not been mapped separately. 

Massive quartzites are rare, but directly south of pegmatite 504 a 

quartzite with a maximum width of 2 feet trends westward for 430 

feet (pi. 2). Between the Hyatt pegmatite and pegmatite 631, a 

7-foot quartzite bed trends approximately N. 15° W. for 120 feet.

A few rounded boulders of a rock composed of lime silicate minerals 

have been found in the Crystal Mountain district These apparently
14 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

were derived from thin limy beds, but none have been recognized in 

the abundant outcrops along the steep valley walls. The dominant 

minerals are plagioclase (labradorite, An8Ab4), epidote, and quartz; 

abundant accessory minerals are hornblende and garnet. Magnetite,, 

siderite, zircon, and sericite are present in minor quantities.

The schist has undergone no serious deformation since the schistosity was formed and recrystallization was completed. Shredded and 

bent mica flakes and strained quartz grams are very rare. Andalusite, staurolite, sillimanite, and tourmaline grains and needles are 

intact despite their susceptibility to dislocation. Retrograde metamorphism has caused the local degeneration of some andalusite to 

quartz and mica, and of biotite to chlorite. There is no record,, 

however, of large-scale retrogressive metamorphism. The metamorphism of the schists, as indicated by andalusite and sillimanite, is

high grade in places, although the more widespread and abundant 

staurolite and garnet suggest that most of the rocks are middle grade. 

The well-developed schistosity and foliation, as well as the widespread 

and well-marked linear arrangement of biotite and, to a lesser extent, 

of quartz, indicate that these rocks recrystallized under great stress 

characteristic of the middle grade of metamorphism of Harker (1932,. 

p. 198-199). Barker's (1932, p. 203) distinction between schistosity 

and foliation is "* * * schistosity is the result of the orientation of 

minerals into plane parallelism, foliation is due to segregation of 

minerals into planes or thin layers of contrasting composition."

GRANITE

The granite in the Crystal Mountain district is a medium- to coarsegrained biotite granite that has many textural and color variations. 

It is correlated with the Mount Olympus granite because of its similar 

composition, its mode of occurrence, and its closeness to areas of 

Mount Olympus granite described by Boos and Boos (1934, p, 323-

324, 308, and fig. 2; 1948, p. 1398). The typical Mount Olympus

granite forms irregular masses, large sheets, and sills. It is not confined to a single more or leas regular mass as are tKe larger and betterknown granites of the Front Range. With two possible exceptions,

the granite in the Hyatt area forms essentially concordant boaiafi.

Isolated sills range from 1 to perhaps 200 feet in thickness; the average 

is about 15 feet. The marginal members of multiple sills have approximately the same range of thickness, but the central members may be

much, thicker. The two largest granite masses, to the north and 

SOUthwest of the Hyatt ranch, are multiple sills. The full extent of

the northern mass has not been mapped, but the part shown in plate 

2 has been demonstrated to be a multiple sill by the flow structures 

and schist partings that parallel the contacts and structure of thecountry rock. The southern mass, though smaller, has a more mas-
GEOLOGY OF THE CRYSTAL MOUNTAIN DISTRICT 15

sive core of granite flanked by marginal sills and many satellite sills 

to the south. The granite in both masses is intricately interfingered 

with the schist; the majority of the relatively smooth contacts shown 

on plate 2 are concealed contacts.

The schist partings are in some places pendants of wall rock, in 

others they appear to be isolated slabs or screens. The partings 

range from slabs of schist 20 feet thick to mere films having the dark 

color, fine grain, and oriented quartz and mica typical of schist. 

They range from 2 feet to several hundred feet in length. Schist 

partings in the granite masses are distinctly weak zones, readily 

etched out by weathering and erosion, that become steps or notches 

which gather talus or a thin stony soil capable of supporting trees and 

shrubs. More schist partings probably exist than were observed, 

but they could not be discriminated readily from joint-controlled 

features.

The isolated sills are consistently concordant. Discordance of any 

part of the large multiple sills is not obvious in the field, but the shapes 

of the two large granite masses indicate some discordant contacts.

The granite is composed principally of orthoclase, microcline, and 

quartz, with lesser amounts of biotite, muscovite, and plagioclase, 

and minor quantities of apatite, magnetite, and zircon. A few minute 

crystals of tourmaline are present in one thin section, and another 

contains siderite along the edges of magnetite grains. A red-brown 

mineral, probably hematite, clouds the orthoclase of one sill.. Orthoclase commonly has been sericitized along fractures and cleavage 

lines, and generally the orthoclase shows pronounced zoning and 

twinning. The biotite is partially chloritized, and it ranges in texture 

from very fine grained to coarse grained The margins of the sills 

in some places show a border zone, %-Yz inch wide, of finer grain than 

the bulk of the sill.

The Mount Olympus granite has a different appearance in different 

sills. It is light to medium gray, depending upon the size and abundance of biotite flakes. One brick-red sill owes its color to the myriad 

of red-brown specks, probably hematite, that cloud the orthoclase. 

In another sill a tapiocalike effect is caused by large rounded grains 

and aggregates of orthoclase in a fine-grained dark matrix of quartz 

and accessory biotite, muscovite, magnetite, and apatite. The orthoclase grains in some sills are larger than the rest of the minerals and 

give the rock an irregular mottled appearance. In sills where the 

major constituents are roughly of equal size the rock has the speckled 

"salt-and-pepper" appearance of typical granite. Longitudinal fractures, thin pegmatites, and biotite flakes in mfany exposures are 

parallel to the sill wall and appear to be related to flowage at the 

time of intrusion.
16 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Straight parallel-sided quartz veins, ranging in width from a knife 

edge to 3 inches, cut the granite and are in turn cut by pegmatite. 

Quartz veins intersected by pegmatites are in some instances displaced 

as much as 6 inches. The relative displacement is always in the-same 

direction: the northwest wall moved northeastward on northeast 

trending pegmatites.

DIOBITE

Scattered boulders of porphyritic, fine-grained black diorite are 

found in a small area between pegmatites 77 and 80 in the northern 

part of the Hyatt area. Individual pegmatites are identified by 

number in plate 5, Index map to pegmatites in the Hyatt area, Crystal 

Mountain district, Colorado, for location on plate 2. Judging from the 

fineness of grain the boulders probably came from a dike similar to 

many dikes known in the Front Range. The rock is composed of 

plagioclase and hornblende with accessory magnetite and minor 

amounts of apatite and quartz. There are two distinct ages of plagioclase: the early generation of large laths are andesine (Ab6An4), and 

the late generation of small interstitial grains are andesine-oligoclase 

(Ab7An3 ). The andesine phenocrysts and the hornblende are slightly 

sericitized. Only a few grains of quartz and apatite are present.

SURFICIAL DEPOSITS

The rolling upland surface has a fairly deep soil presumably Pleistocene in age. The steep valleys of the latest cycle of erosion are 

strewn with boulders, talus cones, and rock slides. In the intermediate 

zone between the new valleys and the old upland, the old soil is being 

removed by slope wash and soil creep and by gullying of the meadows 

and mountain parks as the stream valleys reduce the area of upland 

surface in the process of developing a mature drainage system at the 

new base level for the Front Range.

STRUCTURE

The schist of the Hyatt area strikes approximately east and dips 

southward. Folds in the schist plunge southward at angles ranging 

from 25° tO 75°. The schist in the vicinity of the Hyatt pegmatite

forms small symmetrical folds that plunge to the south. The schist

On the hanging Wall Of the northern granite mass dips southward ftt

angles of 25° to 60° locally 75° and is part of a broad fold. West 

and north of the northern granite mass tKe metamorphic rocks dip 

from 45° to 65° southward and strike uniformly east-northeast. 

(See pi. 2.) The attitude of the sciiist irx ^& vicinity of the southern 

granite mass is more irregular; llCie the schistosity dips more steeply 

than in the rest of the area,

Granite sills and the majority of pegmatites occurring in schist are 

concordant with the metamorphic structure, as shown in the-structure
GEOLOGY OF THE CRYSTAL MOUNTAIN DISTRICT 17

sections (pi. 3). The granite, intruded as several individual bodies 

along the schistosity of the metamorphic rocks, formed multiple sills 

in many places.

About thirty of the widest and longest pegmatites in the area are 

discordant, dipping northward at angles of 65° to 89°. The exact 

nature and age of the structures controlling the attitude of the discordant bodies are not known. The discordant bodies are concentrated, 

with few exceptions, in linear groups having two general trends, 

eastward and north-westward. (See pi. 4.)

The major folds and fractures apparently resulted from the intrusion 

of the large multiple sills. It is assumed that the granite, the pegmatites, and the fractures containing the discordant pegmatites were 

formed during the same period of intrusive activity. The northern 

multiple sill was formed in schist of moderate dip under a broad fold 

or asymmetrical dome; the doming produced a few tear faults trending 

northwestward, and fractures arranged in belts trending eastward. 

Pegmatites were formed both parallel to the schistosity and flow 

structure and across it in faults, fractures, and joints.

Near the middle of the northern mass a few faults displace pegmatites. The faults do not exceed 500 feet in length, and the maximum 

displacement is about 20 feet. The fault planes are straight, narrow, 

and without gouge, breccia, or marginal fractures; they are little morethan joints along which minor movements have taken place. The 

fault planes dip from 45° to 70° to the northwest, and the relative 

displacements are everywhere in the same direction; the northwest 

block moved diagonally upward and to the northeast.

The writer infers from the distribution and refractive indices of 

beryl that there is probably a granite mass, somewhat larger than the 

ordinary sills, buried at no great depth in the vicinity of the Hyatt 

pegmatite. The granite which almost surrounds the Hyatt deposit 

and the body a thousand feet to the east may be attached or closely 

related to the hypothetical mass, and the anticlinal fold plungingsouth-southeastward from the Hyatt pegmatite may represent the 

bowing of the schist by the intrusion of this hypothetical mass. The 

shape and attitude of the fold suggest that the mass may be a concordant body about 700 feet wide and 500 feet thick, shaped more 

like a crude cylinder than a tabular sill; the granite exposed near the 

Hyatt pegmatite may be a part of its irregular top. The fold flattens 

out abruptly to the north of the Hyatt pegmatite and tapers out 

gradually southeastward.

The area has not undergone important deformation since the consolidation of the pegmatites.
18 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

PEGMATITES 

DISTRIBUTION

The pegmatites of the Hyatt area are part of a group that extends 

about 5 miles east and south and at least 10 miles north and west of 

the area. Examination of a few deposits outside the area suggests 

that they are similar mineralogically and structually to those 

mapped in the Hyatt area. Some discordant bodies attain larger 

size and more irregular shape than the concordant bodies, but otherwise there is no correlation between the pegmatites and their environment. The different mineralogic and textural types of pegmatites 

are found in all kinds of country rock and structure. Four types of 

internal structure are recognized in the pegmatites of the district, 

but they are all widely distributed.

SHAPE AND STRUCTURE OF PEGMATITES

The shape and structure of the pegmatite body can be approximated from a study of the pegmatite contacts, the zones and zonal 

boundaries, and the structure of the country rock. The shape of the 

pegmatite is controlled to a large degree by the nature of the country 

rock and the kinds of openings that can be developed in that rock. 

In competent rock such as granite the pegmatites are predominantly 

tabular, branching with angular bends and having relatively linear 

courses. (See pi. 2.) In well-foliated rock such as mica schist, the 

concordant pegmatites are predominantly lenticular, with smoothly 

curving outlines and tapering ends. The discordant pegmatites in 

schist usually have irregular and serrate margins which reflect the 

jagged fracture of schistose rock. Pegmatites controlled by intersecting structures (such as several systems of fractures or schistosity 

cut by fractures) may develop highly irregular shapes, but the shapes 

can be determined if the relation between structure and pegmatite 

can be established. In well-foliated rock the schistose structure, 

linear elements, and details of the contact give evidence of the structure of the pegmatite body. Jahns (1951, p. 54) found the plunging 

structures of pegmatites in New Mexico consistently conformable

with the plunge of numerous minor structural elements in the adjacent country rock. Cameron and others (1945, p. 372) describe the 

pitch of rolls in some pegmatites of New England as related to structural elements of the enclosing rock. According to Bannerman 

(1943, p. s), in certain districts of New Hampshire the types of pegmatites that follow the foliation in schist are inclined to wedge out

suddenly but, generally speaking, to conform in strike and plunge 

with the linear structures of the schist.

The direction and plunge of linear structures impressed on the 

schist by the pegmatite furnish data for determining the plunge of
SHAPE AND STRUCTURE OF PEGMATITES 19

contact features. The data will rarely, if ever, provide a single 

complete solution, but it will set limits to the extent, shape, and 

attitude from which a reasonable generalized picture can be evolved. 

The zones reflect to varying degrees the shape of the pegmatite; 

data on the attitude and dimensions of a zone contribute to the 

determination of the shape of the neighboring zones and the body as 

a whole.

Pegmatites whose shapes are controlled by more than one factor 

present more problems than those controlled by a single factor such 

as schistosity. The greater part of the Hyatt pegmatite is in granite, but both ends extend beyond the granite into schist (pi. 9). The 

contacts between schist and granite are not exposed. The contacts 

between pegmatite and wall rocks give a wide range of possible attitude, but the zonal relationships limit the reasonable interpretations 

to a somewhat narrower range. The shape and attitude of the Hyatt 

deposit as finally interpreted from the results of drilling (pi. 10) are 

reasonably close to that of the composite picture postulated in advance of exploration.

In a bulbous pegmatite, such as the Big Boulder, the lower side of 

which is concealed, the exposures of pegmatite indicate the attitude of 

the roughly convex upper surface, and the dips and plunges do not 

necessarily relate to the converging lower. surface. A small keelshaped exposure hi the undercut outcrop at the north end of the deposit 

(pi. 11) was used as the principal basis for postulating the location 

and inclination of the lower side of the body; two diamond-drill holes 

based on this interpretation did not intersect the pegmatite because 

the plunge of that small exposure was steeper than the plunge of the 

entire body.

The Buckhorn Mica pegmatite has been extensively eroded, but the 

contacts along the western part of the deposit do not indicate the 

plunge of the west end of the body. Indecisive evidence suggested 

that a crest might plunge steeply westward or a keel might plunge 

eastward. (See pi. 13.) Drilling indicated a keel with a moderate 

eastward plunge, and the Buckhorn Mica pegmatite proved to be 

smaller than the "compromise body" postulated before drilling. The 

structures in the schist and the plunge of the line of intersection of 

the contacts in the eastern part indicated that the keel at the east 

end plunged about 40° to the west; exploration confirmed this interpretation.

The structure of internal units in many pegmatites reflects the 

structure of the nearest contact with remarkable fidelity. "Rolls" 

in the contact (anticlinal or synclinal bends or folds) in some places 

determine the localization in internal units of shoots or pockets of 

valuable minerals. The relationship between the two features is
20 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

well exposed in some districts by mining, and examples have been 

described by Cameron and others (1945, p. 377-380, 388), Bannerman 

(1943, p. 11-12), and Jahns (1951, p. 54). The information obtained 

by studies in other districts has been useful in projecting external and 

internal structures below the surface to determine shape and attitude 

of pegmatites and to interpret the results of drilling.

The pegmatites of the Hyatt area have a wide variety of sizes and 

shapes as shown in plate 2, but a few examples to indicate the maximum sizes may prove useful in making comparisons with other 

districts.

The longest pegmatite completely enclosed in granite is pegmatite 

272. It has a length of 1,050 feet, an average width of 8 feet, and a 

maximum width of 12 feet. Pegmatite 259 in the same area is the 

widest, ranging from 11 to 24 feet and averaging 15 feet, it is 830 feet 

long.

The longest concordant pegmatite enclosed in schist is pegmatite 

584. It is 2,675 feet long and 2 to 4 feet wide. The widest concordant pegmatite (585) is 2,100 feet long; it ranges from 2 to 18 feet in 

width and averages 12 feet. The greatest width of concordant 

multiple pegmatite is 200 feet (pegmatite 846). The discordant 

pegmatites in schist vary widely in size. Multiple pegmatite 448 is 

the longest with an over-all length of about 2,500 feet; the maximum 

width is 130 feet. Pegmatite 1197, which has the greatest width, is 

as much as 250 feet wide. If pegmatites 1197 and 1199 should prove 

to be a continuous body, it would be the largest mass of pegmatite in 

the Hyatt area.

Despite the relatively small average dimensions of the individual 

bodies in the western part of the northern granite mass, the myriad of 

interconnected pegmatites exposed there probably contain the greatest 

concentration of pegmatitic material in the area. Pegmatites are 

generally more extensive in schist than in granite, however.

TEXTURES

The textures of individual units within pegmatites vary widely. 

The grains commonly attain sizes so much larger than those in other 

rocks that the ordinary descriptive terms must be redefined. The 

size classification used in this report is that given by Cameron and 

others (1949, p. 16) :

Qtneral grain sizt

Fine.. ..._----_-_-_------.-----------------------------' ^ess than *

Medium___-__-_____-______-_-_-----_-_--_-----------__-_ 1 to 4

Coarse-..-------........-..----------------------------- 4 to 12

Very coarse_._---__. __-_-.__.._._._.._......----------_-- Greater than 12
TEXTURES 21

Statements with regard to the grain size of a pegmatite or unit indicate 

the general appearance in exposures; grain size is a qualitative expression of the size of the grains comprising the bulk of the material. 

Interstitial grains may be very much smaller, and a few grains or 

masses may be much larger than the average size or range indicated. 

(See pi. 8.) Bastin (1911, p. 10) regards this irregularity of grain of 

pegmatites as more distinctive than the coarseness that is so widely 

emphasized.

The texture and range of grain size of the principal zones of the 

 explored pegmatites are summarized in table 2. All the minerals 

increase in average grain size toward the center of the pegmatite, but 

each mineral seems to have its own rate of change in grain size. The 

increase is most spectacular in zoned pegmatites, but the change is 

'apparent in homogeneous pegmatites. Perthite exhibits the most 

obvious increase in grain size. Quartz, whether in single grains or 

aggregates, increases in size manyfold from the border zone inward. 

Muscovite in a few places shows a great increase in size, as for example, from the contact to the inner intermediate zone at the Hyatt 

pegmatite and from the contact to the outer intermediate zone of the 

Buckhorn Mica mine, but ordinarily the increase in grain size of 

muscovite is less marked than that of perthite and quartz. Plagioclase shows the lowest rate of increase. Though the minerals may be 

present near the center of a homogeneous pegmatite in approximately 

the same proportions as near the contact, the increase in size of the

TABLE 2. Grain sizes of three zoned pegmatites in Crystal Mountain district,

Colorado

Location of pegmatite

Hyatt deposit: 

Border zone _ _______________

Inner intermediate zone_______

Core. _____--_--_-----_-____-

Big Boulder prospect:

Upper intermediate zone. _____

Lower intermediate zone l-....

Hood_-_-_---------___------

Core »_. _____ ------- .....

Buckhorn Mica mine: 

Border zone __ ______________

Outer intermediate zone __ .__

Inner intermediate zone_--_-__

Core. ________-_-__--_-___.__

Texture

Fine.--.. _ .

__.__do_----_-

Very coarse. ._

Fine... _ '...

----.do.......

Medium._-___

Coarse_______

Very coarse. _ .

_--..do__-___.

Fine ____ ..

___._do._.____

Medium _ ___

__-..do_---__

Coarse..-----

Range in size of 

the majority of 

grains (inches)

<1

4-12

4-12

>12

<1

<1

1-4

4-12

>12

>12

<1

<1

1-4

1-4

4-12

Range in size of 

all grains 

(inches) 

0. 01-4

. 01-36

. 01-60

. 01-120

.01-1

.01-3

.01-8

. 01-30?

. 01-72

. 01-60?

. 01-5

.01-3

. 01-12

. 01-24

. 01-36

1 Maximum dimension inferred from drill core.
22 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

perthite and quartz is more conspicuous because the plagioclase is ID 

part interstitial to the larger grains and in part masked by weathering, 

staining, and plant matter. The changes in grain size for the minerals of a well-exposed zoned pegmatite and a typical homogeneous 

pegmatite are summarized in table 3.

TABLE 3. Comparison of changes in grain size in a zoned pegmatite and homogeneous 

pegmatite, Crystal Mountain district, Colorado

Perthite_ ________ ____

Quartz __ _ ___________

Plagioclase. __________

Muscovite. ______ ___

Beryl.. _ ____ . _

Tourmaline. ______._._

Garnet. ______________

Hyatt pegmatite

Grain size in 

wall zone (inches)

0 01-4 

01-3 

01-1 

01-2. 5 

01-1. 75 

01-2 

01- 2

Grain size in or 

near core 

(inches)

0 01-120 

01-48 

01-8 

01-15 

01-48 

01-4 

01- 6

Homogeneous pegmatite

Grain size within 

6 inches of eontact (inches)

0 01-1 

01- 7 

01- 4 

01-4 

01- 8 

01-1 

01-2

Grain size near 

center of pegmatite (inches)

0. 01-10 

. 01-10 

.01-1 

. 01-2. ft 

.01-2 

.01-2 

. 01-1

Boundaries between pegmatite units are more generally gradational 

than abrupt because of the over-all coarseness of the component 

minerals. The boundaries between well-exposed fine- and mediumgrained units of contrasting composition can be fixed ordinarily 

within a foot or two, but the boundaries between coarse- and very 

coarse-grained units are less well marked, especially if the mineralogy 

is closely related. The general sequence of mineral assemblages 

(table 6) shows that most assemblages are closely related mineralogically to those earlier and later in the sequence. The average composition and texture of a zone may contrast sharply with the average

for those adjacent to it, but the boundaries are in most places gradational. A pegmatite zone is a lithologic unit, and its boundary does 

not necessarily follow the margins of individual mineral grains. In

the Big Boulder deposit tke boundary between thfi hOOd Of per.hi.6- 

quartz pegmatite and the core of quartz pegmatite (pi. 11) must be

drawn between zones with a common mineral and also across a texture

featuring the interlock Of grains as much as 6 feet in size. The boundary is drawn so that the average composition of the core does not 

Include more than 5 percent Of perthite, although a trench along the

boundary as drawn mignt sKoW that 80016 perthite gTRmS OVCrlap

the boundary or some isolated perthite crystals were present m the

quartz core. In all the maps of zoned pegmatites the boundaries

between zones have been drawn as relatively smooth lines, whereas

development work will inevitably show an intricate serrate relationship between the individual mineral grains.
TEXTURES 23

The textures developed in a pegmatite result from the complex 

but orderly progress of crystallization in a multicomponent chemical 

system whose composition and environment make possible greater 

(or at least, more obvious) growth and segregation of minerals than 

is found ordinarily in igneous rocks.

INTERNAL STRUCTURE OF ZONED PEGMATITES

The lithologic and structural units found within pegmatite bodies 

differ in mineralogy or texture, or both. Three basic types of units 

are distinguished and are defined by Cameron and others (1949, p. 

13-24) as follows:

1. Fracture fillings are units, generally tabular, that fill fractures in previously 

consolidated pegmatite.

2. Replacement bodies are units formed primarily by replacement of pre-existing 

pegmatite, with or without obvious structural control.

3. Zones are successive shells, complete or incomplete, that reflect to varying 

degrees the shape or structure of the pegmatite body. Where ideally developed 

they are concentric about an innermost zone or core. Some concentric units, 

however, are not zones but belong in the categories above.

The term "unit" includes all three types of bodies defined above.

FRACTURE FELLINGS

Fracture fillings are common although minor features of pegmatites 

in the Crystal Mountain district. Quartz-filled fractures are the most 

abundant and rarely exceed 30 feet in length. They commonly are 

from 1 to 12 feet long and from a knife edge to 3 feet wide. Pegmatitic 

fracture fillings in homogeneous pegmatites are apparent because of 

differential weathering; they invariably differ in texture from the 

enclosing body and are etched out by weathering.

Fracture fillings may be homogeneous or zoned and occur within 

homogeneous or zoned pegmatites. Pegmatite 645 (pi. 2) is not zoned, 

but one fracture filling is a zoned unit containing a wall zone of plagioclase-perthite-quartz-muscovite pegmatite, and a core of perthitequartz-plagioclase pegmatite. At the Big Boulder prospect a fracture 

filling composed of perthite-quartz pegmatite extends from the 

hood-shaped inner intermediate zone across the outer intermediate 

and the wall zones. (See pi. 11.) The fracture filling has a gently 

curved trace and steep dip, but its vertical extent is not known. It 

can be traced into the hood for about 4 feet where it merges with the 

minerals of the inner intermediate zone.

The margins of fracture fillings are fine grained and in some places 

contain oriented muscovite flakes and quartz grains. Beryl crystals 

in the wall zone of the fracture filling in pegmatite 645 (pi. 2) are 

oriented with the long axis normal to the wall of the fracture. Pegmatite 448 (pi. 2) contains two beryl-bearing fracture fillings at the
24 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

east end. Both are nearly flat lying and occur near the top of thebody. In one fracture filling 161 beryl crystals are exposed, and theberyl content is about 0.28 percent. In the other fracture filling 52 

crystals are exposed, and the beryl content is 0.3 percent. Pegmatite 

645 (pi. 2) contains many fractures with an average strike and dip 

of N. 60° W., 40° S., but only a few contain beryl-bearing pegmatite; 

the best exposed fracture filling has over SOOismall beryl crystals, 

and the^rocfc has 'a beryl content of 0!9 percent.11 The-beryl4>earing; 

fracture fillings rarely exceed 3 feet in thickness, the maximum being^ 

about 5 feet. The average dimensions of fracture fillings are about 

1 foot thick, 60 feet long, and 15 feet wide, and the tonnage of contained beryl is small.

REPLACEMENT BODIES

No mappable replacement bodies have been recognized in the 

pegmatites of the Crystal Mountain district. Cameron and others. 

(1949, p. 83-97) have described replacement bodies in other parts, 

of the country.

. . ' ZONES i '. . ' -'' '

A zoned pegmatite is one consisting of two or more successive 

shells, and may or may not contain fracture fillings or replacement 

bodies. Zoned pegmatites are comparatively rare hi the Crystal 

Mountain district. Of the 1,300 bodies mapped in the Hyatt area, 

28 have been designated as zoned pegmatites. Of these, 27 consist 

of two zones and are listed in table 4; one, the Hyatt deposit, has. 

five zones.

Zones have been classified by Cameron and others (1949, p. 20) as 

border zones, wall zones, intermediate zones, and cores.

BOBDEB ZONES

The border zone is the outermost zone of a pegmatite and constitutes a fine-grained selvage that is not more than a few inches thick 

in most pegmatites. In most border zones the minerals, especially 

muscovite and quartz, show a preferred orientation normal to the 

COntaCt. Minerals with an elongate habit, such as tourmaline and

beryl, exhibit preferred orientation to ft marked &Qg£QG When pieSP/nt 

in the border zone.

Quartz and muscovite, and in some places plagioclase, are the 

dominant minerals of border zones adjacent to schist; the texture of 

these border zones is universally fine grained, the minerals averaging 

leSS than a quarter of an inch in diameter. The line between schist 

and border zone is invariably sharp and distinct.

Border zones of pegmatites in COntaCt With granite are somewhat

less regular and not so well defined. The minerals of the border zone 

interlock noticeably with those of the granite even where there is a
INTERNAL STRUCTURE OF ZONED PEGMATITES 25

TABLE 4. Pegmatites consisting of two zones, Hyatt area, Crystal Mountain

district, Colorado

[Essential minerals are stated in order of decreasing abundance, perthite (P), plagioclase (Pg), quartz (Q),

and muscovite (M)]

Pegmatite no.

Mineralogic composition

Wall zone Gore

Beryl content 

[percent]

405.

442" 

443. 

464. 

512. 

527. 

563.

565.

566.

567. __ Pg, P, Q

571-. ....................... Pg, P, Q

642............................. P, Pg, Q

748. . ... P, Pg, Q 

766 .........-.- ........... P, Pg, Q

llZ. r .................. ......... P, Pg, Q

774--. 779... ...................... P, - Pg, - --Q

781 l -

827. .. _PJ_Q7Pg

859.. 

939- 

1017. 

1039. 

1068 ---...-----.---.--------- P, Pg,

1111.

1284 ......................... P, Q.'Pg

0.09 

0

Tr.

Tr. 

0

Tr.

.10 

0

.02

.07

.31

Tr.

Tr.

Tr.

Tr. 

0 

0

.56

Tr.

.15 

0 

0

Tr. 

0

.02

Tr. 

0

i One member of a multiple pegmatite.

seemingly sharp contact between the two rocks. In both rocks, 

quartz and feldspars are the dominant minerals, and muscovite is a 

minor accessory; plagioclase is subordinate to perthite in most border 

zones in contact with granite. The margins of many pegmatites 

grade into granite over a width of an inch or two. Gradational contacts are ordinarily irregular, and it is impossible in some places to 

fix the precise limits of the border zone. In a strict sense, perhaps, 

there is no border zone in these places.

WAIL ZONES

The wall zone is inside the border zone and is generally coarser 

grained and thicker. In describing the zoning of some pegmatite 

deposits in Brazil the term "border zone" has been used by Pecora and 

others (1950a and 1950b) to include both the border zone and wall 

zone as here used. A common practice in pegmatite mining districts 

of the United States is to include border zone arid wall zone, as defined 

here, in the term "wall zone."
Wall zones of pegmatites in the Crystal Mountain district are 

invariably composed of feldspars and quartz; in some deposits perthite 

is much more common than plagioclase, and in others the reverse is 

true. Quartz is subordinate to the feldspars, and muscovite is a 

minor constituent. Beryl, tourmaline, and garnet are present in 

many wall zones as accessory minerals. In a few deposits the beryl 

content is about 1 percent.

The texture of most wall zones is medium to fine grained, and the 

minerals have a random orientation. Some minerals in wall zones 

exhibit a preferred orientation with the long dimension normal to 

the wall of the pegmatite, for example, the beryl crystals hi the wall 

zone of the fracture rilling of pegmatite 645 (pi. 2). Tourmaline 

crystals, though uncommon in the wall zone in the Crystal Mountain 

district, are oriented similarly in some deposits.

INTERMEDIATE ZONES

Any zone between the core and wall zone is an intermediate zone; 

if there are two or more, they can be designated by letter, number, or 

such terms as "inner," "middle," and "outer." Most intermediate 

zones are shells around a core, but some, as in the Hyatt pegmatite, 

are discontinuous and lenticular. The Hyatt, Big Boulder, and Buckhorn Mica pegmatites all contain more than one zone between the 

wall zone and the core. Perthite-rich intermediate zones of some 

pegmatites are discontinuous and show a marked tendency to be 

concentrated in the upper part of the pegmatite; such a domelike 

deposit, concave inward and downward, is referred to as a "hood." 

The Big Boulder pegmatite contains a prominent hood of perthitequartz pegmatite. The other zoned pegmatites described in this 

report contain only wall zones and core in addition to the very thin

border zones. In each of the polyzonal deposits the texture and 

mineralogy are sufficiently distinctive and well exposed that more than

two mappable units can be distinguished.

CORES

The core is the innermost zone and occurs at or near the center of

the pegmatite, commonly as an elongate lens or a series of disconnected segments. Cores of pegmatites in the Crystal Mountain

district are, lor tne most) part, quarts or pertKito, o*- botK. The core

of the Hyatt deposit is perthite pegmatite (pi. 9) and that at Big

BOUlder prOSpeCt (pi. ll) is quartz pegmatite. The core of the 

Buolsiiorii Iviioo. pegmatito (_Fl. i3> is i,Ke only exception In this district

and it is composed of cleayelandite-quartz-spodumene(?) pegmatite.

The texture of the cores is very coarse. The cores of thin pegmatites 

are invariably thin and may be discontinuous. Tne core of the 

Buckhorn Mica deposit has the shape of a flat lens witn a maximum
INTERNAL STRUCTURE OP ZONED PEGMATITES 27

width of 12 feet and a length of 160 feet.. Bulbous bodies like the 

Hyatt and Big Boulder pegmatites have somewhat ovoid cores consistent with the shape of the entire body. Pegmatite 464 is a narrow 

pegmatite with a pronounced bulge near the middle, and a quartz 

core is present only in the bulge (pi. 2). A similar relationship has 

been described by Cameron and others (1945, p. 383) at the United 

Mine, Grafton, N. H., and the E. E. Smith mine, Alexandria, N. H., 

.and other deposits. There is no fixed ratio between the size of the 

pegmatite and the size of the core; in some bodies the core constitutes 

a small percentage of the pegmatite, and in others, such as the Crystal 

silica deposit described by Hanley, Heinrich, and Page (1950, p. 93- 

 96), the core seems to make up more than half of the pegmatite.

TELESCOPED ZONES

Two or more zones that are clearly defined in parts of a given 

pegmatite may appear elsewhere to merge along their dip or strike 

into a single unit whose composition corresponds to the bulk composition of the two zones. Such "telescoped" zones bear the same relationship to the adjacent zones as that occupied jointly in the other 

parts of the pegmatite by the zones into which the single unit can be 

traced. Telescoping may present the reverse impression to the one 

described above: a zone continuous around the core may show a 

local segregation of minerals so marked that two mappable units are 

formed. The bulk composition of the segregated units corresponds 

to that of the full zone into which they can be traced. At the Hyatt 

pegmatite the hanging-wall side of the intermediate zone of plagioclase-quartz-perthite-muscovite pegmatite shows such a segregation 

of minerals into two mappable units: an outer intermediate zone of 

perthite-quartz pegmatite and an inner intermediate zone of plagioclase-quartz-muscovite pegmatite.

SHOOT

The terms "shoot," "streak," "pocket," and "lens" are used to 

describe local concentrations of particular minerals or textures within 

a zone and carry the connotations established by general use in 

mining. The minerals of a particular zone may be uniformly dissemi- 

.nated but commonly are more irregularly distributed; this is especially true of the minor constituents. Tourmaline, beryl, garnet, and 

the rare minerals commonly occur within a zone as local concentrations separated by relatively barren rock. The beryl in the inner 

intermediate zone of the Hyatt pegmatite is found hi pockets of coarsegrained crystals and masses. The pockets discovered by past mining 

(pi. 9) were 6 to 12 feet long, generally extended the full width of the 

zone, and were 10 to about 35 feet apart. The fine-grained beryl in 

the wall zones of the Hyatt, Big Boulder, and Buckhorn Mica pega295165 55 3
"' 't I. .' ' ;'' ''';,' 1 ' '' .. '"i

28 PEGMATITES OF THE* CRYSTAL MOUNTAIN DISTRICT, COLORADO

matites is not segregated into pockets or shoots, but the distribution? 

is sufficiently irregular to necessitate extensive sampling in order toobtain a representative analysis. Large books of muscovite arescattered irregularly throughout the inner intermediate zone of theHyatt pegmatite, but much of the fine-grained muscovite has been, 

found concentrated in streaks 1 to 30 feet long and from 1 inch to 

5 feet wide. The mica streaks overlap the beryl pockets to some 

extent, but do not everywhere coincide with them. At the Big; 

Boulder prospect garnet occurs in pockets of closely packed euhedral 

and subhedral crystals. The individual crystals are as much as oneinch in diameter, and the pockets are X to 3 feet in size.

A pegmatite that consists of a single zone enclosed between borderzones tthat is, uniform from wall to wall except for the selvages was 

 designated as a "homogeneous pegmatite" by Johnston (1945,. 

p. 1025). Most of the pegmatites of the Crystal Mountain district 

are of this type, and differ from zoned pegmatities in grain size and' 

degree of segregation of the essential minerals. Bodies exhibiting 

uniform texture and proportions of minerals from wall to wall are 

almost-as unusual in the Crystal Mountain district as those madeup of sharply contrasted zones. Even the zones within zoned pegmatites may show widely differing proportions of the essential minerals 

on short distances. (See: appendix A.)

Perthite, plagioclase, quartz, and muscovite are the most common 

minerals in homogeneous pegmatites of the Hyatt area. Perthite

has the most variable grain size. Quartz grains increase in size and 

form aggregates in progressively larger clots or pods toward the center 

of the pegmatite. Muscovite, although a minor constituent, forms;

distinct books in the interior of the bodies in contrast to the tiny

flakes near the walls. Plagioclase grains increase in size toward the 

center, but the increase is less than that of the other minerals.

\ The relative proportions of the yarious minerals may change as

well as the grain size; generally perthite and quartz increase in abundance as the plagioclase decreases. The texture and mineral distribution in a great many pegmatities is irregular because perthite, ana

quartz, or both, occur in clots scattered throughout the perthiteplagioclase-q'uai'tz pegmatite which forms the bulk of the deposit. In 

other bodies the clots are centrally located. A group of pegmatites

could be selected to show, like the diagrammatic sequence of figure 4, 

gradation from. homogeneous bodies' to. 'pegmatites consisting Of a

Wall zone and. core. In discussing pegmatites in New England;

Cameron and others (1945, p. 373) note ttat fee 18 flO sharp distifld-' 

tion between zoned bodies'and "unzOne'd"' or homogeneous bodies.
- HOMOGENEOUS PEGMATITES .

Uniform texture and dissemination of minerals

Irregular texture and distribution of minerals

 __^--t--?rrr^yiiS^^^ ' » ^sift

.v^j

Irregularities accentuated- by .formation of clots

__ 

_^___....._ ^Tt n . .:--.V-.':-:xv?^??1r-!^-_ 

 ^r 77 - I?.:.--.-.-.--:-: ».- ' "... .-. : ,,»,.» x ; -;. : V":: i",- > -.?; ^^v^>>^ <^JvL7rr;;JiV^^v'«'-v.xw*x'-<;*:i\i;;>Vi<»««*«»»*v*iVi?/rxii*»»w^v*? 1--'-V-iiiN ^?^vs: ^r^iJJ^\.;^M^* «^ ::v"v ?'' v ; ^^?;^ ^^^^>>»>M^'A ;^^: ^v ^^^a^^T^y^-^^x^^^ii-'r^^:.^-^^:-.

, Clots arranged' symmetrically with respect to the walls

<<z$53?%^ ^^&%?;:W<wWl^

Intermediate stage between central clots and .discontinuous core

Discontinuous core of zoned pegmatite

Discontinuous core in pegmatite containing three zones

FIQUEE 4. Idealized plans' of pegmatite bodies, showing sequence of types 

between homogeneous pegmatites and zoned pegmatites.

29
30 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

For purposes of this report an arbitrary limit has been drawn between 

homogenous pegmatites containing scattered clots of minerals and 

zoned pegmatites containing cores. If the centrally located concentrations of clots are continous for at least a quarter of the length of 

the pegmatite and have a width of at least a fifth of the width of the 

pegmatite, they are considered cores, and the pegmatites in which 

they occur are designated as zoned bodies. This definition of the 

lower limit of zoning places about 2 percent of the pegmatites of the 

Hyatt area in the zoned class. More than 1,300 pegmatites are 

plotted in plate 2; of these 1,234, or 94 percent, are classed as 

homogeneous.

MULTIPLE PEGMATITES

The term "multiple intrusion" is credited to Holmes (personal 

communication) by Stokes and Varnes 4 and defined as: "A term 

applied to sills, dikes, laccoliths, and other intrusions formed by two 

or more successive injections of approximately the same magma." 

The term "multiple pegmatite" is used in this report to designate 

bodies mapped and described as one pegmatite which consists of two 

or more pegmatitic masses separated by screens or partings of country rock or by border zones. In many parts of the Crystal Mountain 

district there are clusters of pegmatities so narrow and so closely 

spaced that they can not be plotted individually at a scale of 1:6,000. 

The members of multiple pegmatities are, with few exceptions, homogeneous bodies. Pegmatite 846 is a continuous mass of pegmatite 

but is made up of a number of individual members. Between pegmatites 723 and 746 (pi. 2) are about 75 individual intrusions forming 

.a series of 24 multiple pegmatites.

BANDED PEGMATITES

The term "banded" is used to describe the appearance and internal 

structure of a few pegmatites in the Hyatt area composed of alternating bands of light and dark minerals. Feldspar and quartz pre-

 dominate in tlae light bands and muscovite and quartz predominate

In the dark bands. Tourmaline is abundant in the dark bands of a

few banded pegmatites and greatly intensifies the contrast between

bands. In pegmatite 629 (pi. 2), tourmaline constitutes about 1

percent of the dark bands. The banding is most sharply defined in

very fine-grained pegmatites where the grains average less than a

quarter of an inch in diameter. With, increasing grain size the banding 

becomes less distinct. Banding is roughly paraUel to the walls -whether

the pegmatite is in schist or in granite, Or whether COnCOrdant OF 

discordant. Fegmatite 025 is partly discordant, but the banding

parallels the walls throughout the body. No pegmatite is known to 

< Stokes, W. L., and Varnes, D. J., Preliminary glossary of selected geologic terms (manuscript report).
BANDED PEGMATITES 3l

be uniformly banded throughout its length; banded portions merge 

with homogeneous material either along the strike or across the 

width. Within a single exposure, banded pegmatite may appear to 

cut and be cut by typical unhanded pegmatite. The narrow easttrending offshoot of pegmatite 432 is discordant and crudely banded. 

The banding is parallel to the contact but is separated from the 

contact by a 2-foot, fine-grained, feldspar-rich layer. A 3-inch wide 

fracture filling cuts across the feldspathic layer from the banded layer 

to the wall. The fracture filling is not banded but is of the same composition and grain size as the banded rock. The fracture filling is 

neatly outlined by garnet grains and muscovite flakes.

This use of the term "banded" differs from that of Ball (1908, 

p. 63) who states: " * * * granular pegmatites grade along their 

strike into rudely banded dikes, quartz being commonly segregated 

in the center (fig. 17) * * *." The description and figure 17 in Ball's 

report refer to a pegmatite that the writer would describe as a pegmatite with a feldspar-rich wall zone and a quartz- and biotite-rich

core.

MINERALOGY

The internal units of pegmatites are designated by names that 

express composition hi terms of essential minerals. The order of 

mineral names in the designation is in approximately the decreasing 

order of abundance and in most cases includes those that are present 

in the unit in excess of 5 percent. The essential minerals of a majority 

of the pegmatites in the district are perthite, plagioclase (albite and 

cleavelandite), and quartz. Muscovite is an essential constituent hi 

the inner intermediate zone of the Hyatt deposit. Tourmaline is an 

essential mineral in a few small bodies. In order to distinguish the 

core from the innermost intermediate zone at the Buckhorn Mica 

mine, it is necessary to include the name of a relict mineral in the 

designation: the inner intermediate zone is quartz-cleavelandite 

pegmatite, and the core is quartz-cleavelandite-spodumene(?) pegmatite, though the spodumene is represented only by aggregates of 

fine-grained albite and sericite, pseudomorphous after spodumene. In 

the field the difference in the units is very apparent, but the mineralogy is approximately the same, except for the pseudomorphs.

Proportions of minerals were determined in the field by inspection 

and noted as percentage composition. The beryl content of each 

outcrop was determined by measuring the area of every discernible 

grain of beryl and calculating the percentage with respect to the area 

of the exposure. In pegmatites that contain over 0.1 percent beryl, 

the total area of rock studied by grain counting was at least 1 percent 

of the calculated surface area of the deposit. Experience has shown 

that careful grain counting yields an accurate measure of percentage
32 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

composition: estimates of ore grades at the Hyatt, Big Boulder, .and 

,Buckhorn Mica pegmatites based on grain counts made by Hartley, 

.Page, and-the writer between 1942 and 1948 were confirmed by mine 

.productivity at the Hyatt mine in 1948 and by bulk assays made in 

1949 and 1950. Similar confirmations have been obtained from the 

.work in South Dakota.

MINEKA1LOGIC TYPES OF PEGMATITES

Six mineralogic types of pegmatites, based on bulk mineralogic 

composition, are recognized in the Hyatt area. Five of the types are 

inineralogic assemblages common in many pegmatite districts, but 

the sixth is an anomalous assemblage in which tourmaline constitutes 

more than 5 percent of the unit. The types and the number of pegmatites included in each type are given in table 5.

The descriptions of individual pegmatites in the Hyatt area are 

arranged in appendix B by mineralogic types in the same order as 

in table 5. The individual bodies are numbered to correspond with 

the index map (pi. 5), from which they can be identified on the 

geologic map (pi. 2). A few small pegmatites are shown without 

numbers or corresponding descriptions.

.TABLE 5. Mineralogic types of pegmatites in the Hyatt area, Crystal Mountain

district, Colorado

Mineralogic type

I.

II 

II

Feldspar-rich pegmatites : 

A. Plagioclase-perthite-quartz pegmatite. _ _________________

B. Perthite-plagioclase-quartz pegmatite: 

1. Ratio of perthite to plagioclase approximately 1 :!____ 

2. Ratio of perthite to plagioclase approximately 3:2_ _ _ _ 

3. Ratio of perthite to plagioclase approximately 2 :!____

' Total__________.______________-____----______

Total_-.___________________

Quartz-rich pegmatites

[ . Tourmaline-rich pegmatites ____________

Pegmatites 

(number)

198 

614 

303

144 

1,115

1,259 

45 

3

Sequences of mineral assemblages as units of zoned depoalts 

been determined for many districts, and the assemblages in four 

districts have been summarized by Cameron and others (1949, p. 

59-70); the assemblages in the Black Hills, S. Dak., have been described in detail by Page a,rxd otters (1053). The mineralogic types 

Of pegmatites in the Hyatt area are analogous to mineralogic units

recognized in pegmatites of tie BlfUt HfflS. Page's tabulat-OH Of

mineral assemblages is reproduced as table 6, with the addition of 

small arrows to indicate the mmeralogic types of pegmatites observed 

in Hyatt and other areas in the Crystal Mountain district.
MINERALOGIC TYPES OF PEGMATITES 33

Comparison of table 5. with table 6 shows that the pegmatites of the 

Hyatt area have a relatively limited range of composition. Those

 of the first four types (table 5) contain perthite, plagipclase, and

 quartz and comprise 96 percent of the bodies in the area. These are 

.all variants of assemblage 3 (table 6). Those of the fifth type are 

.representatives of assemblage 12 (table 6).

TABLE : 6. General sequence of mineral assemblages l and observed lithologic types 

in pegmatites in Black Hills, S. Dak., and Crystal Mountain district, Colorado

[Arrow Indicates lithologic types observed In Colorado]

Minerals of zones

Essential minerals

1. Muscovite (M). 

Quartz (Q). 

Plagloclase (Pg) : 

a. Albite 

b. Oligoclase.

2. Quartz (Q). 

Plagioclase (Pg): 

- a. Albite 

'b. Oligoclase.

3. Perthite (P). 

Quartz (Q). Muscovite. 

Plagioclase (Pg): 

a. Albite 

b. Oligoclase.

4. Perthite (P). 

Quartz (Q).

5. Perthite (P) (or mlcrocline). 

Quartz (Q). 

Plagioclase (Pg) 

(usually clea velandlte) . Amblygonite (A). 

Spodumene (8).

Common accessory minerals

Tourmaline. 

Beryl. 

Biotlte. 

Perthite. 

Apatite. 

Cassiterite. 

Columbite.

Tourmaline. 

Beryl. 

Perthite. 

Apatite. Muscovite. 

Cassiterite. 

Cblumbite-tantallte.

Tourmaline. 

Beryl. ,.. , Li, Mn, Fe, phosphates. 

Columbite-tantalite. 

Apatite. 

Lollingite. 

Biotite.

Tourmaline. 

Beryl. 

Plagloclase. 

LI, Mn, Fe, phosphates. Muscovite. 

Columbite-tantalite. 

Apatite. Lollingite.

Tourmaline. 

Beryl. 

Cassiterite. 

Tantalite-columbite. 

Muscovite. 

Apatite.

Essential minerals hi order of 

abundance

: Dominant

 >a. Q. M.. ...... ........

 »b. M, Q... ....... ......

__>c O M Pe

, d. Pg, Q...............

e. Q, Pg.. .............

f 0 Pe M

g Pg M Q

h Pe O M

a

'Pff f\

 ^->b O Pff

a. Pg, M, Q, P... ...

b. Pg, Q.M, P.........

c. Pg, Q, P.M.. .......

d. Pg, Q, P

e. Pg, P, Q, M.. .......

f Pg, P M Q

 *g. Pg> P Q

h. P, Pg, Q,M ......

 >1 P Pe O

j. Q, Pg.M, P. ........

k. Q, Pg, P.M........

1 O Pe P

m. Q, P, Pg, M.. ......

n. Q, P, Pg

o. Q, P.M.. ...........

P. P, Q, Pg 

q. P, Q.M.... .........

r O Pe P '

s. Q.Pg.M.. ..........

_ 40 n P

 >b. P, Q....... .........

 >C. P-... ...............

a. A.. .................

b. Q.P, A....... ......

c. Q,P, Pg, A. ........

d. Q, Pg, A, P;........

e. Pg, Q, A. ..:...... ..

f. Pg, Q,A,8 . 

g. P, Pg, Q 'A, 8

h. Q,P, 8, A.. ........

i. P, Q, 8...:. . :.

j. Q. Pe. P. 8..........

Minor

Pg 

Pg

M

M '

M

M

M

M 

M

S 

ft

P

Q

Pg

P 

P

P?

1 Page, L. R., and others, 1953.
34 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

TABLE 6. General sequence of mineral assemblages 1 and observed lithologic types 

in pegmatites in Black Hills, S. Dak., and Crystal Mountain district, Colorado

Continued

[Arrow Indicates lithologic types observed in Colorado!

Minerals of zones

Essential minerals

6. Plagloclase (Pg): 

a. Cleavelandite. 

Quartz (Q).

7. Plagloclase (Pg): 

a. Cleavelandite. 

Quartz (Q). 

Spodumene (S).

8. Quartz (Q). 

Spodumene (S).

9. Plagioclase (Pg): 

a. Cleavelandite. 

Quartz (Q). 

Lepidolite (L).

10. Quartz (Q). Microcline (P). .

11. Microcline (P). 

Plagloclase (Pg). 

Lithia-Micas? (L1M). 

Quartz (Q).

12. Quartz (Q).

Common accessory minerals

Tourmaline. 

Beryl. 

Cassiterlte. 

Tantalite. 

Muscovite. 

Apatite. 

Amblygonite.

Beryl. 

Tourmaline. 

Muscovite. 

Cassiterite. 

Tantalite. 

Apatite.

Microcline. 

Plagioclase. 

Lepidolite. 

Beryl.

Microlite. 

Spodumene. 

Beryl. 

Amblygonite. 

Tantalite-columblte. 

Cassiterite. 

Microcline. 

Tourmaline. 

Apatite.

Spodumene. 

Muscovite. 

Plagioclase. 

Apatite.

Cassiterite. 

Apatite.

Plagioclase. 

Beryl. Microcline. Muscovite

Essential minerals ta order of 

abundance

Dominant

 »a. Q, Pg... ............

C TPpr

a. Q, Pg, 8..... ........

b. Pg, Q, S.. ........ ..

a. Q, S...... ...........

a. Q, Pg, L.. ..........

b. Pg, Q, L............

c. Pg, L- ...... ......

d. L.. .................

a. Q, P... ..........

b. P, Q........ .....

a. P, Pg, L1M, Q.......

 >a Q

Minor

Q

?g,Q

i Page, L. K., and others, 1963.

The dominant units of zoned pegmatites in the Hyatt area consist

of assemblages 5 and 4, or 3 and 12. The border zones are quantitatively insignificant; many have the composition of assemblage 1,

and some, principally those in granite, are of assemblage 3. Many*

homogeneous pegmatites contain clots of perthite or quartz, or both, 

which may be regarded as incipient development of assemblages 3.

and. 4. The Hyatt pegmatite is the only body with more complex

zoning and is.considered separately,

Lithium minerals are not abundant in the district and, therefore,

assemblages 5/7, 8, 9, and 11 are not represented. The presence of

trace quantities of 'lithium at the Hyatt, Big Boulder, and Buckhorni

Mica pegmatites is indicated by minor amounts of Li-Mii-Fe phosphates and by relict spodumene; in these three bodies assemblage 6r
MINERALOGIC TYPES OF PEGMATITES .35

plagioclase-quartz pegmatite, is well developed. This is, the assemblage that Cameron and others (1949, p. 67-69, and table 5) list as a 

variant of plagioclase-quartz-spodumene pegmatite.

Fersman (1940) classifies pegmatites by the mineral assemblages 

(though they are not designated as such) and by the characteristics 

of certain diagnostic minerals. The individual groups are called 

"geophases" and labeled A to L. The paragenetic diagrams by Fersman (1940) and the illustrations and descriptions in reports by 

Tscherbakov,6 Labuntzov (1939), and Sinegub (1943) show that 

essentially the same mineral assemblages found in American pegmatites are recognized in Russian deposits and in the same sequence as 

shown in table 6. The pegmatites, of the Hyatt area have been 

.assigned tentatively to Fersman's geophase E, the descriptive group, 

without accepting his genetic and geochemical-geophysical interpretation of that group.

FELDSPAR-RICH PEGMATITES

The average composition of the feldspar-rich pegmatites, type I 

of table 5, of the area approximates that of granite. This type has 

been subdivided into three classes in which the ratios of perthite to 

plagioclase are approximately 1:1, 3:2, and 2:1. The members of 

each class are distributed at random throughout the area, and there is 

no clear correlation between mineralogic composition of the .pegmatites and structural control, beryl content, indices of refraction of 

beryl or plagioclase, accessory mineral content, country rock, or 

relation to intrusive masses.

The feldspar-rich pegmatites predominate in the area and exhibit 

the widest range in size and shape. Perthite makes up as little as 

:20 percent of the plagioclase-rich pegmatites and as much as 65 percent of the perthite-rich pegmatites. Plagioclase generally composes 

from 15 to 60 percent of the same types of deposits, and the qua,rtz 

 content ranges from 5 to 35 percent.

QUARTZ-RICH PEGMATITES

The quartz-rich pegmatites, type II, tables 5 and 17, are minor 

bodies rarely consisting of more than lenses of massive quartz containing scattered feldspar and muscovite crystals. Quartz-rich 

pegmatites are generally 6 inches to 3 feet wide and 5 to 85 feet long. 

They are more commonly concordant than discordant and consist of 

either single continuous bodies or closely spaced lenses separated by 

1-inch to 2-foot schist partings. The largest of the quartz-rich 

pegmatites is pegmatite 1033 (pi. 3) which has an inferred length of 

'650 feet.

 Tscherbakov, D. I., 1936, Genetic types of berryllium deposits in the USSR: Redkie Metally [rare 

.metals], v. 5, p. 35-41. [Translation, in flies of U. S. Geol. Survey].
36 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

. Quartz-rich pegmatites are gradational with the other types of 

pegmatites (table 5). Pegmatite 1023 is 55 percent quartz, pegmatite 1145 is 60 percent quartz, and pegmatites 525 and 598 are each 

85 percent quartz; they comprise a connecting series between the 

feldspar-rich pegmatites and the typical quartz pegmatite containing 

over 95 percent quartz. Perthite and plagioclase are both common 

in quartz-rich pegmatites, but the proportions vary greatly. Only a 

few grains of feldspar and flakes of muscovite are identifiable in most 

pegmatites of this type.

Gradation between the quartz-rich and tourmaline-rich types of 

pegmatites is illustrated by pegmatites 260 and 404; both tourmaline 

and quartz are essential constituents, and perthite is an accessoryconstituent.

TOURMAUNE-BICH PEGMATITES

The classification and interpretation of the tourmaline-rich pegmatites, type III in table 5, are much in doubt. They are poorly exposed 

and have a maximum width of 1 foot and a maximum inferred length 

of 30 feet. Only 3 pegmatites, 260, 398, and 404, are of mappable 

size; but about 5 other bodies are known. The tourmaline content 

ranges from 12 to 90 percent, and it may occur as a marginal or as a 

.central segregation. In these bodies tourmaline is associated with 

quartz, with quartz and perthite, and with plagioclase, perthite,. 

quartz, muscovite, and garnet (appendix B). There are all gradations 

in mineralogy from a typical pegmatitic assemblage to a quartz-tourmaline vein. The tourmaline-rich bodies may be classified either aa 

variants.of assemblages 1, 2, or 3 (table 6), in which the tourmalinizing 

and silicifying fractions that ordinarily escape and alter the wall rock 

were retained in the pegmatitic liquid, or as the early fugitive frac^ 

tions from a granitic or pegmatitic magma that were concentrated 

and trapped aS fillings Of fractures. They also may be considered 

deposits transitional between pegmatites and tydrOthermal VeiuS.j 

if SO, they WOllld be similar to the chalcopyrite-bearing tourmalinequartz veins found near Pecos, N. Mex., described by Krieger (1932,

p. 463); the tourmalme-rich Silver, lead, and gold veins of the Helena 

region, Montana, described by Knopf (1913, p. 45-54); and the tOUTmar 

line-bearing tungsten veins of the Isla de Pinos, Cuba, described by

-Page and McAllister (1944, p. 177-246).

DESCRIPTIONS OF MINERALS ' The minerals observed in the pegmatites of tJio orystai Mountain,

area are described in their approximate decreeing 01(101 Of abundance, 

and the properties of a group of minerals found in a miaroiitic 

are described at the end of the section.
DESCRIPTIONS OF MINERALS 37

Perthite, plagioclase, and quartz are the most abundant; muscovite" 

is rarely an essential mineral; beryl, tourmaline, and garnet are the 

commonest accessory minerals, and apatite is less common.

Of the following rare minerals found in trace amounts, some are 

known in only one locality and others in eight: Biotite, columbitetantalite, microcline, lithiophilite, triphylite, sillimanite, bismuthinite, 

hematite, magnetite, limonite, chrysoberyl, bertrandite, fluorite, and 

uraninite and related minerals. For convenience in reference the 

description of microcline follows that of perthite, and the description 

of biotite is included with that of muscovite, though both microcline 

and biotite are very rare in these pegmatites.

PERTHITE

. Perthite is the dominant mineral in 85 percent of the pegmatites in 

the Hyatt area and is an essential mineral of assemblages 3 and 4 

(table 6). The perthitic structure, an intergrowth of albite in microcline from which the name "perthite" is derived, is generally visible 

without the aid of a hand lens. The microcline ranges in color from 

milky white to deep salmon but is usually a dull pinkish white; the 

albitic stringers form an anastomosing network and are lighter in 

color than the microcline.

Perthite is an abundant and readily identifiable constituent of 

most pegmatites, both as small grains near the walls and large masses 

and aggregates in the interior. It is closely associated^with quartz in 

most occurrences. Perthite is the principal constituentTof the hood 

at the Big Boulder prospect, and it is the only essential constituent 

of the core of the Hyatt deposit, where it contains innumerable minute inclusions of muscovite, plagioclase, and quartz. Perthite grains 

range in size from microscopic (in border zones, banded pegmatites, 

and matrix) to large crystals up to 10 feet across. The mineral varies 

in abundance from less than 1 percent in some quartz pegmatites to 

about 96 percent in the core of the Hyatt pegmatite.

In zones where both perthite and plagioclase are essential minerals;, 

perthite is almost invariably more abundant in the upper part of the 

zone than in the lower part. The causes or methods of this segregation have not been determined, but it is a widespread phenomenon, 

recognized in other districts by Cameron and others (1945), Jahns 

(1946), Cameron and others (1949), Page and others (1953), and 

Staatz and Trites (in press). Some zones of the explored deposits 

are divided into an upper perthite-bearing zone and a lower plagioclase-rich zone. (See pis. 10, 12, and 13.) The upward segregation 

of perthite is not confined to the wall zones; the formation of a perth* 

ite-rich hood, such as that of the Big Boulder deposit (pi. 12) is another example of the same phenomenon wherein thejpotash feldspar
38 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

of an interior zone is segregated toward the top or roof of the pegmatite. Another example is the perthite-rich outer intermediate zone 

of the Hyatt pegmatite (pi. 10), which is developed only on the 

hanging-wall side of the deposit. Page and others (1953) and Staatz 

and Trites (in press) describe similar perthite occurrences.

Graphic intergrowths of perthite and quartz are common in many 

pegmatites but never abundant in any of them. It is not recorded 

separately in appendix B because graphic granite does hot seem to 

have any consistent relationship to the composition or structure of 

.the pegmatites in the Crystal Mountain district.

mCROCLINE

Nonperthitic microcline has been recognized only in a few scattered 

occurrences. It occurs as a few light-salmon grains about 1 inch in 

diameter in the plagioclase-quartz pegmatite of the lower wall zone 

from diamond-drill hole BB-5 in the Big Boulder pegmatite. Only a 

small part of the grains exhibit gridiron twinning, and the indices of 

refraction are somewhat lower than for most specimens: the beta index, 

determined by W. T. Pecora, of the U. S. Geological Survey, is 1.519.

Microcline is an essential constituent of assemblages 10 and 11 

(table 6) and is present in assemblage 5 in some pegmatites. However, assemblages 5, 10, and 11 are directly related to lithium-rich 

units. The Crystal Mountain district is a lithium-poor region, and 

microcline is not found as an essential mineral. In its few occurrences 

it constitutes only a rare accessory mineral.

PLAGIOCLASE

Although plagioclase is the dominant feldspar in the 144 pegmatites of type IA (table 5 and appendix B), it is less abundant in the 

district than perthite. It is milky white to pale pink and generally 

shows polysynthetic twinning under the hand lens. The grains are

usually smaller than those of the associated perthite and quartz, even

where plagioclase is the most abundant mineral, and it is found more

as groundmass and interstitial material than as distinct crystals or

aggregates. Plagioclase forms small equidimensional grains in most

pegmatites, but in some bodies the grains become elongate and platy

toward the center of the deposit. In the central units of the larger

zoned deposits, the plates become well formed and as much as 8

inches long; the name cleayelandite is applied to this variety of plagioclase. Plagioclase is a persistent associate of muscovite and beryl

and can be found around or intergrown with them wherever they occur. 

The ranges in indices of refraction and composition of 237 plagio-

.clase specimens from the Hyatt area are given in figure 5. Ihe determinations are of the minimum index of refraction (Ni) on (010) 

cleavage fragments. The ratio of albite to anorthite is taken from a
DESCRIPTIONS OF MINERALS 39

200

160

O

o .

IT 

UJ 

O>

120

1.520 1.530. 1.540

N fl ON (010)

FIGURE 5. Distribution of plagioclase indices.

table by Grout (1932, p. 468) which correlates the variation in index 

of refraction with changes in composition. The composition ranges 

from Ab78 to Ab99 , but 91 percent of the determinations are between 

Ab94 and Ab99 . The cleavelandite variety of albite has a compositional range of Ab94 to Ab99 .

The writer has attempted, without success, to correlate the variations in composition of the plagioclase in the Hyatt area with (1) the 

composition of the enclosing pegmatite, (2) the structural position of 

the pegmatite, (3) the type of country rock, (4) distance from the 

granite masses, and (5) association with other minerals, especially 

beryl. The range of composition of the majority of specimens is so
40 PEGMATITES OF,THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

limited that no systematic variation is discernible, and the few specimens with compositions outside the dominant range are scattered 

seemingly at random throughout the area. ; 

Several hundred determinations of index of refraction of plagioclase 

from the drill cores are not included in figure 5. The exploration 

furnished 14 excellent cross sections through three well-zoned deposits. The composition in these bodies ranges from Ab;92 to Ab99, 

with an average pf about Ab98 ., The composite results for the three 

deposits show a slight decrease in the anorthite content from the wall 

to the core of the pegmatite. Several holes show no systematic change 

in index, and in bthers the change is confined to the outermost few 

feet of the pegmatite.

Plagioclase is the dominant mineral in the lower part of the wall 

and intermediate! zones of the Hyatt, Big Boulder, and Buckhorn 

Mica pegmatites] Cleavelandite is an essential constituent of the 

core and inner intermediate zone of the Buckhorn Mica deposit and 

the'lower intermediate zone of the Big Boulder pegmatite. The 

abundance of pligioclase is not easily determined in all outcrops. 

Because the plagioclase grains are generally smaller than their associates, they weather more rapidly and form hollows that are invariably 

stained and crusted; and masses of the mineral, even where large, 

are : not conspicuous beside perthite and quartz. Plagioclase and 

quartz are found:in graphic intergrowth in many small areas and in 

places make up sizable parts of a zone, as in drill hole BB-5, Big 

Boulder prospect, where the inner ,part of the plagioclase-quartz 

pegmatite contains 7 feet of rock of which about half is composed 

^f graphic material.

QUARTZ

'Quartz is the dominant and in some places almost the only mineral 

in the quartz-rich pegmatites, but in the other types it is subordinate 

to the feldspars. (Quartz, as milky-white to light-gray anhedral grains, 

most commonly forms from 5 to 35 percent of the pegmatite. Glassy 

chips are not common, and according to Hanley, Heinrich, and Page

(1950, p. 95), even the clearest material at the Crystal Silica property 

(fig. 1) is slightly milky. Smoky, to black quartz is found in,contact

 with, radioactive minerals.

Quartz ranges in size from microscopic grains in border zones and

interstices between other minerals to large masses in the-interior ZOneS.

The difficulty in recognizing the precise boundaries ,.of anhedral

grains precludes giving exact measurements, tout oon-tin/uous ina-sses

(that-'may be aggregates of grains), of quartz are as much as. ftftBt

across in the core of the Big. Boulder pegmatite. The perthite, bore 

of the Hyatt deposit contains, in addition to minute inclusions of 

quartz, rounded masses as much as \% feet wideband 4 f,eet long. ..
..,. . ,..,,,.,. ..DESCRIPTIONS OF MINERALS 41 1 > '> ' . - ' . .'' ' ' . . < ' r V "V. *., :' ; " " ''' s

Some of the quartz in the perthite-quartz pegmatite of the hood in 

the Big Boulder pegmatite has the appearance of, a ''quartz breccia" 

with a perthite matrix. This "breccialike" material occupies irregular 

but somewhat rounded areas 1 to 6 feet in cross section. There is ho 

 continuity .between the areas nor any semblance of alinement or 

jplanar arrangement to suggest that it is a tectonic feature. The 

quartz is separated by a network of irregular fractures into sharply 

angular fragments, the pieces gradually increasing in size so that the 

'/breccia".grades outward into normal massive quartz cut,by a few 

joints and fracture planes. The central parts are made up of darkgray pieces ranging in size from 0.01 to 0.2 inch, the color becomes 

lighter as the fragments increase in size. The dark color of the quartz 

suggests that radioactive minerals might be present and that perhaps 

the fracturing might be related to then: presence. The interstices are; 

filled by material that would normally be available during crystal-; 

lization but not likely to be transported into the fractures after

consolidation of the hood. ..* .; *: , ... 

MUSCOVITE AND BIOTITE

Muscovite is a minor, '"but 'universal, constituent-of pegmatites "in 

the Crystal Mountain district. Despite the abundance o!: 'biotite in 

the related granite intrusives and in the schist wall ^rock,>.: it'has been 

found in trace quantities in only three bodies, pegmatites 1'014,1225, 

and 1244. The Crystal silica pegmatite described by HanleypHe'inrioh, 

and Page (1950, p. 93-96) contains both muscovite andr a mass of 

lodestone of large but 'undetermined' size, but no biotite is found. 

Staatz and'Trites (in rjress)' found that biotite supersedes muscovite 

in the Quartz Creek district as the iron content of the pegmatites 

increases' arid: magnetite becomes an' accessory mineral.

The principal deposit of muscovite in the Crystal Mountain district 

is in the outer intermediate zone of the Buckhorn Mica pegmatite. 

It has been described by Sterrett (1923, p. 59-60) and Hanley, Heinrich, and Page (1950, p. 88-90) and is reported to have yielded some 

sheet mica, but most of the muscovite is suitable only for grinding. 

About 30 tons of scrap mica is reported to have been mined from the 

inner intermediate zone of the Hyatt deposit: The books attain sizes 

as much as 15 inches long and 6 inches thick, but are wedge shaped 

and show ruling, "A" structure, and abundant mineral inclusions. 

The muscovite shoots are found in plagioclase-rich zones, but the 

pegmatites, as a whole, are rich'in, perthite and such deposits generally 

jdeld muscovite with little or no sheet mica, according to Cameron 

and others (1945, p. 383, 392) and Jahns (1951, p. 55). Bannerman 

(1943, p. 12) and Cameron and r others (1945, p: 382)'also..note that 

beryl and phosphatic minerals are associated in'many .places with
42 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

imperfect mica; beryl is a common associate of muscovite in the 

Crystal Mountain district.

In the majority of pegmatites mapped in the Hyatt area, muscovite 

ranges from microscopic size, to three-quarters of an inch in diameter 

and rarely attains 2 inches. The average size is about a quarter of an 

inch. It rarely exceeds 1 percent of the pegmatite and is present in 

excess of 5 percent only in the two zones mentioned previously.

Muscovite is associated with tourmaline in fracture fillings in the 

Big Boulder pegmatite and in late networks of fine yellow and white 

scales, some of which are lithium-bearing. The lithium-bearing 

muscovite fills fractures cutting all previous structures and minerals 

and is interesting because of its relation to relict spodumene. The 

scales of fine mica are in large part slightly curved, and many of them 

have one index below 1.55, which, based on findings in South Dakota, 

is interpreted as indicating the inclusion of lithium hi the composition 

of muscovite. Sericite present in a miarolitic cavity is described in 

a later section.

TOtfRMALINEColumnar crystals of black tourmaline with well-developed prism 

faces are present in the schists, granites, and pegmatites of the Crystal 

Mountain district. The tourmaline crystals range from microscopic 

in size to a maximum of 4 inches in length, but the tourmaline in 

pegmatites of type III (table 5 and appendix B) occurs in masses a& 

much as 4 by 4 by 6 inches in size. Much of the tourmaline in the 

schist and granite is derived from solutions escaping from the pegmatites, but some of it is native to the country rock. In granite the 

tourmaline Of replacement origin is markedly poikilitic and 10 to 

100 times larger than the minute delicate needles of primary crystallization. Tourmaline in the schist is commonly alined in the plane 

of foliation, and in some places there is a linear parallelism concordant 

with drag folds and other lineation. Crystals in the country rock do 

not exceed three-fourths of an inch in length, and the individual 

Crystal invariably has parallel Sides. Tourmaline in pegmatites 

generally forms long columnar crystals, but a number Of UTeglllar 

skeletal and tapering crystals have been found. (See pi. 8.) One

tapered crystal, about 3 incKes long, measures a quarter of an inch in

diameter at one end and 1 inch at the other and contains

inclusions Of groundmass material. A small pegmatite

of peg«xatit6 137 is only 5 inches wide, but contains tourmaline

CryStalS aS mUCh as 2ft inches long and IH i*ioKos in diameter wKich 

are uniformly oriented normal to tte Walls Ol tll6 UOUj.

Tourmaline in pegmatites of type III (table 5 and appendix B) 

constitute 12 to 90 percent of the rock, and in altered wall rocks it 

comprises as much as 40 percent of the schist. Tourmaline grains
DESCRIPTIONS OF MINERALS 43

observed in the drill core of the Hyatt and Big Boulder deposits 

indicate that this mineral is present in all zones, including the quartz 

core. Tourmaline and muscovite fracture fillings occur in the Big 

Boulder pegmatite. Tourmaline also was found in a miarolitic cavity.

The Crystal Mountain district is one of about a dozen beryl-rich 

pegmatite areas in the country, and the present larger study was made 

primarily to determine the distribution and quantity of beryl. Beryl 

occurs as an accessory mineral only in the pegmatites; none has been 

recognized in the granites or schist, though spectrographic assays 

indicate the presence of traces of beryllium in the wall rocks of the 

three explored deposits (table 13). Beryl is widely distributed 

throughout the area in pegmatites that contain from traces to about 

2 percent. It occurs in homogeneous and banded as well as zoned 

pegmatites but has not been found in quartz pegmatites or tourmalinequartz pegmatites of the Hyatt area. Its general associations do not 

seem to preclude the possibility that better exposure or more extensive examination of these bodies might disclose the presence of 

beryl.

Beryl is difficult to recognize in many parts of the Crystal Mountain 

district. It is usually a dull greenish gray to light bluish green, but 

white, yellowish, and blue varieties have been found. Beryl associated 

with lithium-bearing minerals is a dull-white mineral that is particularly difficult to distinguish from milky quartz and feldspar. Only 

two tiny, greatly fractured chips of clear aquamarine-blue beryl 

were found. Crystals of a wide variety of shade£,q,f,bluergreen,,occur 

in close proximity, and there is no discernible external control of the 

color. Fersman (1940, p. 97-98) states that this pale grayish- and 

bluish-green beryl, distinct from the yellow, golden, brown, rose, 

green, and aquamarine varieties, is typical of the beryl of his "geophase E."

Beryl generally forms euhedral crystals on which the only common 

face is the hexagonal prism (110), but anhedral grains have been 

found in many bodies and are especially abundant in the zoned 

deposits (figs. 7-12, 21, 22, and 23-27). Commonly, the prismatic 

crystals are tapered, in some places producing strikingly conical shapes. 

In other places crystals are broken along the basal cleavage and the 

parts recemented with the enclosing minerals. One specimen exhibits a series of steplike offsets along the basal cleavage, similar to 

that described by Johnston (1945, p. 1032-1033). Such beryl indicates movement within the pegmatite after the formation of that 

particular crystal but before complete crystallization of the material 

forming the nearby groundmass.

295165 55 4
44 PEGMATITES OF,THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

The largest beryl crystal found in a homogeneous pegmatite or the 

wall'zone deposits of zoned pegmatites was. 8 inches long and 3 inches 

in diameter, but the'common range is from 0.01 to 2 inches. The 

beryl grains are considerably larger in interior zones: in the inner 

intermediate zone of the Hyatt pegmatite, the range is from 2 inches 

to 5 feet; the average is about 1 foot. One beryl crystal at the Big 

Boulder prospect, mined from the inner side of the hood, as reconstructed from the weight, the known depth of the pit, and part of the 

cast of the crystal remaining in the rock, was approximately 6 to 7 

feet long and 1.8 feet in average diameter. It is also reported that 

the crystal tapered towards both ends. The other minerals in the 

associated perthite-quartz pegmatite are as much as 6 feet in cross 

section, so the size of the beryl crystal was proportional to the 

surrounding crystals.

In zoned pegmatites the plagioclase- and muscovite-rich units are 

the most likely to be beryl-bearing, though other units may contain 

beryl if the deposit is beryl-rich. Even .in homogeneous pegmatites 

the plagioclase- and muscovite-rich areas in or surrounding the clots 

or cores of perthite and quartz are more likely places to find beryl 

than in the clots themselves. No beryl is exposed in the Hyatt 

deposit in either the perthite of the ,core or the perthite-quartz pegmatite of the outer intermediate zone, although the spectrographic 

assays (figs. 1.5 and 16) indicate the. presence of a small percentage of 

BeO. The beryl-bearing hood.of perthite-quartz pegmatite in the 

Big Boulder deposit contains interstitial plagioclase and muscovite. 

Most beryl contains abundant inclusions .of plagioclase, muscovite, 

quartz, and perthite and, in .addition, a thin layer of fine-grained

muscovite may coat the crystal..

The theoretical formula of beryl; Be3Al2 (Si03)8, contains .14.0

percent BeO, but natural beryl contains varying amounts of Na2 (X

Li2O, Cs2O, and combined water. Unpublished studies by ~W. T.

Schaller, of the Geological Survey, show that the indices of refraction

of beryl increase as the alkali content increases. The increase in

alkali is made almost entirely at the expense of beryllium, so the 

variation in the omega index of refraction is also a. measure of berylr 

lium content. The results of almost 300 determinations of the 

omega index and corresponding BeO content of beryl from pegmatites

in tlae Hyo,tt turetx o,:re shown in. figure 6. The dotted lino superposed

on the distribution graph represents the symmetrical curve that

could be derived by smoothing out the irregularities in the graph of

actual determinations. It is the sort of curve produced by deviations 

which are free to fall in either directipn from a mean value. The

curve indicates that the beryl of the Hyatt area contains an average 

of about 13.4 percent BeO, but no at.tempt has been made to confirm
 DESCRIPTIONS <QF MINERALS , ,. .., ... 

APPROXIMATE BeO CONTENT, PERCENT

13.8 13.4 12.9

80

60 * </)

.'

.(E

*o 40

<ii 

o

,1'oc 

'o>

20

S

°

\

K

\

1.570 1.580

; N w OF BERYL 

FIGURE 6. Distribution of beryl indices.

 the average by analysis of a composite sample. The geographic 

position and index of each specimen, plotted in plate 6, show a systematic distribution of the variations in alkali and beryllium ratio that

 can be contoured with relatively smooth lines. The highest indices 

,are in the areas, of the two large granite masses and in the vicinity of 

the Hyatt pegmatite where there are two small pluglike masses of 

.granite: . - - 

: A high proportion of pegmatites in the Crystal Mountain district

 contain beryl as an accessory nuneralpthe abundance in different 

bodies ranging from about 2 percent in a particular zone to a single 

crystal in an entire pegmatite. Commonly several crystals or grains

 occur in close proximity even in small bodies; therefore, an arbitrary 

distinction has been made between a "rare accessory" and an."abundant accessory." If the estimated beryl content is less than 0.01 

percent it is considered a rare' accessory and reported in appendix B 

.ak a trace amount. If the estimated.quantity of beryl contained in a 

pegmatite is less than 1 ton it"is not considered a potential source of 

;the mineral: ; The beryl resources considered in tables 7 and 8, therefore^-represent the deposits-where beryl is an abundant accessory,
46 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

and contains an estimated 1 ton or more of beryl in rock with an 

estimated grade of 0.01 percent or more.

In the Hyatt area 350 pegmatites are known to contain beryl 

(pi. 7). The number of deposits in which beryl is an abundant 

accessory probably would not be increased appreciably by further 

search.

A-total of .7.7 pegmatites>% (tables 7, an,d 8) .contain over 1 ton of beryl 

in rock with a grade of 0.01 percent or more. Two deposits, the Hyatt 

pegmatite and the small body to the south (pi. 2), were known before 

the present study was undertaken. An analysis of the distribution 

of beryl deposits shows that the Hyatt pegmatite is the most important 

source of beryl in the area. Of the known beryl resources, 27 discordant pegmatites in schist contain 28 percent, 31 pegmatites in granite 

contain 62 percent, and 20 concordant pegmatites in schist contain 10 

percent. The northern granite mass is much richer in beryl deposits 

than the southern mass 20 percent as compared to 0.05 percent of 

the beryl resources.

The three principal areas'of granite, the two large masses and the 

plug which almost encloses the Hyatt pegmatite, are each surrounded 

by belts a thousand feet wide in which beryl deposits are small: 

the thousand-foot belt around the northern mass contains 2 percent of 

the beryl resources, the belt around the southern mass contains 0.3 

percent, and the one around the Hyatt plug contains 0.4 percent. By 

contrast, the next thousand-foot belt, concentric to the first belt, 

contains, in the same order, 9 percent, 9 percent, and 6 percent of the 

beryl resources. The 13 deposits that are not within the masses and 

their concentric belts contain 11 percent of the resourcea of the area 

(table 7).

TABLE 7. Distribution of beryl with respect to granite intrusives in Hyatt area, 

Crystal Mountain district, Colorado

Pegmatites

In granite mass:

Mass at Hyatt mine _ _ ____ ______

In l,OOO-foot belt around mass:

Southern mass-:..... .. .. ...«. .-

Mass at Hyatt mine _ _ _

In belt 1,000 to 2,000 feet around mass:

Northern mass ___ _ _ _ _ _____ ____ _

Southern mass ___._____-_____--_-_-__-___-_

Mass at Hyatt mine. .-.-_._____._._:._._.__

In the remainder of the area. -___.-__-__-_--__._.

Percent of

pegmatites

40

1

1

5

1"

3

25

8

13

Percent of

beryl resources

20.0

.05

42.0

2. 0

.3

.4

9.0

6.0

11.0
DESCRIPTIONS OF MINERALS 47

These comparisons suggest that beryl deposits occur with somewhat 

greater frequency in granite masses which contain both large and small 

pegmatites than in granite masses with only small pegmatites, that 

discordant bodies are more commonly beryl-bearing than concordant 

ones, and that, beryl deposits are,, least abundant in pegmatites immediately adjacent to granite masses.

Next in importance to deposits in granite are the discordant pegmatites; the pegmatites concordant in schist are the least important 

group. The comparisons are given in table 8.

TABLE 8. Distribution of beryl-bearing pegmatites according to country rock and

structure, Hyatt area

.Hange of inferred resources ' 

(tons)

Ito5.-. .-...... . 

6to SO.. ......................

More than 50 __ . __ ......

Pegmatites concordant 

in schist and isolated 

sills

Number 

. of pegmatites

12

7 

None

TtifSli beryl 

(tons)

25 

171 

None

Pegmatites discordant 

in schist

Number 

of pegmatites

10 

15 

2

Total beryl 

(tons)

32 

323 

209

Pegmatites In granite

Number 

of pegmatites

16 

11 

4

Total beryl 

(tons)

38 

145 

1,070

GARNET

Garnet is a common accessory mineral in the schist but is relatively 

uncommon in pegmatites and has not been found in the granite. The 

crystals in schist range from microscopic in size to one-quarter of an 

inch in diameter; the average is about 0.01 inch. The garnet in 

pegmatite has about the same average size, but crystals as much as 

1% inches in diameter can be found in a few bodies. Most garnet 

crystals are reddish brown, but a few minute trapezohedral crystals 

are bright red and transparent. Garnet usually occurs in scattered 

.groups of a few individual crystals and, more rarely, in rows near the 

pegmatite contact. Pockets % to 3 feet in diameter of closely packed 

euhedral to anhedral grains are found in the hood of perthite-quartz 

pegmatite at the Big Boulder deposit. The grains are as much as 

an inch in diameter, and heavily stained with manganese oxides. 

Associated with this garnet are quartz, muscovite, plagioclase, tourmaline, and iron and manganese phosphates.

The specific gravity of individual fragments was calculated from 

weighings on a Berman microbalance, and the specific gravities of 

entire suites of grains from single localities were obtained by use of the 

pycnometer. The microbalance indicates that the specific gravity of 

garnet varies within single layers of schist and within individual 

pegmatite outcrops. The overall range is from 3.72 to 4.31, but 

there is little correlation between the specific gravity of individual
48

grains and the bulk specific gravity of entire suites. Records of 

previous determinations do not exceed 4.25, so it is assumed the 

higher readings signify the presence of heavy impurities. The results of 24 microbalance determinations are given in table 9; the compositions are stated in terms of the percentages of theoretical end 

members: pyrope (Mg3Al2Si3Oi2), almandite (Fe3Al2Si3Oi2), spessartite- 

(Mn3Al2Si3O12), grossularite (Ca3Al2Si3Oi2), and andradite (Ca3Fe2~ 

Si3O12) (indicated by PY, AL, SP, GR, and AN, respectively). Thecompositions are approximate, and are taken from the data tabulated^ 

by Winchall (1947, p. 174-183).

TABLE 9. Approximate composition of garnet in Hyatt area 

concentration In garnets: +, present; , absent]

Pegmatite no.

144..........................

185............ _ ...........

316..........................

397..........................

483..........................

495. ...................

584..........................

584..........................

827..........................

863.. .......................

972. ......................

1050.......... ...............

1054.........................

1068.... . ..............

1128........... ..............

1131.........................

1157.........................

1164

1194...... ...................

1201.........................

1286 -.. ........ ..

Schist... ....................

Schist.... ........ ......

Mn

+++++++ +; +-H-+ i1

Sp gr Individual 

grain

4.06 

3.80 

4.06 

3.86 

4.06 

3.75 

4.07 

3.77 

4.00 

4.22 

4.15 

4.06 

3.95 

3; 72 

4.14 

. 3.87 

4.02 

4.00 

3.91 

4.14 

3.98 

3.94 

3.97 

3.87

Index 

of refraction

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.805 

1.80 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.81 

1.805 

1.81 

1.795 

1.81

Proportion

PY

33

21 

28

1.6 

34 

23

16

27 

34

AL

38

36 

20 

71 

53 

15 

84 

37 

65

84

53 

37

SP

76 

' 30 

; 76

: 76

21 

77 

26 

86 

64 

77

83 

66

82 

72

GR

11 

35 

11

II 

41 

10 

38 

8

48

4

14

7 

10

AN

13 

35 

13 

29 

13 

38 

13 

36 

6

3 

8 

19 

37

29 

 12 

13 

20

11

18 

20 

29

Sp gr 

entire 

suite

4.10- 

J 4.22

4.06-

3.9fr

3.71

The index of refraction was measured by immersion in liquids of 

known index of refraction. A few indices are equal to 1.81, but most

are slightly below 1.81 and above 1.805, and a few others are as low 

as 1.795.

The presence or absence of manganese was tested with borax beads. 

Garnets from some pegmatites contain manganese and others do not.

Two specimens from pegmatite 584, selected from different parts of 

the body, indicate widely differing compositions. Many garnets from

schist, not included in table 9, were tested for manganese; and the

results were consistently negative", A thorough study of garnet compositions and their distribution will require much more extensile,

sampling.
DESCRIPTIONS ' OF MINERALS 49 

APATITE

Deep-green, bluish-green, and lilac apatite has been found in the 

explored deposits and in pegmatites 807, 1212, and 1246 as grains 

ranging from 0.1 to 0.6 inch in diameter. Apatite is commonly dark 

and distinctive, but a few grams of light bluish-green material were 

mistaken at first glance for beryl, for example, in the outer part of 

the wall zone at the Big Boulder deposit. Lilac apatite occurs in the 

inner intermediate zone of the Hyatt deposit. It is a very rare constituent of the pegmatites and is recognized principally because of 

its distinctive color. Apatite is present also in a miarolitic cavity; 

Apatite is more abundant 'in the country rocks but is visible only 

under the microscope. :

1 SIILIMANITE

The schist contains sillimanite in fine acicular crystals, but the 

only specimen found in pegmatite consists of a cluster of parallel 

columnar crystals 0.5 to 1.5 inches long and averaging 0.1 inch in 

diameter. The crystals are a translucent grayish white, have a 

vitreous luster, and are somewhat fibrous. Sillimanite is associated 

with quartz, plagioclase, muscovite, and perthite and occurs within

2 inches of the contact of pegmatite 1146. There are no indications 

that the sillimanite was derived by alteration of an argillaceous 

inclusion; if it is the result of contamination, the material was 

thoroughly digested before crystallization of the sillimanite and 

surrounding pegmatite.

UTHIOPHILITE-TRIPHYLITE

The phosphatic minerals lithiophilite arid triphylite are end members of a continuous series between LiMnP04 and LiFePO4 . Ordinarily 

"the phosphates of Fe, Mn, and Li are coated with dark-brown to 

dull-black products of oxidation and hydration. The alteration 

products constitute a number of minerals of which only purpufite is 

readily identifiable in the field. Members of the lithiophilite-triphylite 

series were found only in the three explored and one unexplored 

deposits.

A member of the lithiophilite-triphylite series was exposed in the 

upper part of the inner intermediate zone of the Hyatt pegmatite by 

mining operations in 1948. The fresh material is medium blue, and 

the lowest index of refraction is about 1.675. According to Winchell 

(1947, fig. 78, p. 150) this indicates an approximate composition of 

Iithiophirite8o triphylite20 . It is associated with quartz, pyrite, and 

lithia mica, and the aggregate forms blocky masses from 1-20 cubic 

inches. Cinnamon-brown lithiophilite-triphylite was found in the 

lower part of the inner intermediate zone of the Hyatt deposit. The
50 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

beta index of refraction is about 1.69, indicating a composition of 

about Iithiophilite45 triphylite55 . It is estimated that the lithiophilite-triphylite content of the workings made in the inner intermediate zone in 1948 was of the order of O.OOX percent. Workings 

antedating 1948, yielded about 300, pounds of the brown to black 

altered material, and the content of that part of the zone may have 

been as high as 0.01 percent.

C OIUMBITE-TAWTAIITE

A single block of rock found on the dump of the Buckhorn Mica 

mine contains more columbite-tantalite than has been found in the 

remainder of the Crystal Mountain district. The mineralogy of this 

sample indicates that it came from the core of the deposit. Three 

clusters of tabular crystals have an aggregate volume estimated to 

be about 11 cubic inches. ,The plates are from 0.01 to 0.23 inch thick, 

0.2 to 3 inches long, and 0.1 to 2 inches wide. A block of what appears 

to be "massive" columbite-tantalite is about 1 inch by 1 inch by 0.7 

inch. The Tantalum claim and the Crystal Silica claims described 

by Hanley, Heinrich, and Page (1950, p. 93-96, 98-99) and the Beryl 

No. 5 claim, the Big Boulder deposit, the Hyatt pegmatite, and two 

small bodies not included in the areas mapped contain from a single 

crystal to three crystals of columbite-tantalite. The mineral dimensions range as follows: 0.02-0.1 inch in thickness, 0.3-0.9 inch in 

width, and 0.5-1.1 inches in length. From determinations of specific 

gravity it is possible to estimate the Ta2O5 and Nb2O5 content of 

columbite-tantalite: specific gravity of specimens from the Crystal 

Mountain district ranges from 6.2 to 7.3, indicating a range in T^Og 

content from about 39 to 76 percent and in the Nb2O5 content of 

from about 10 to 48 percent. A specimen from the Tantalum claim 

has the highest reported specific gravity and tantalum content (Hanley, Heinrich, and Page, 1950, p. 99). The columbite-tantalite content 

of the Buckhorn Mica pegmatite and the Tantalum claim deposit 

may amount to a few hundred pounds; however, the columbitetantalite found in the other pegmatites is negligible.

BISMUTHIWITE

Bismuthinite (Bi2S3 ) and its alteration product, bismutite, a

bismuth carbonate, occur in the inner intermediate zone of the Hyatt

pegmatite, The writer estimates the content in the zone exposed by

mining in 1948 amounted to O.OOX percent. In one place the bismuthinite formed a matrix for large grains of perthite and quartz

and filled fractures in other minerals. The main mass of bismuthinite 

was intergrown with plagioclase, muscovite, and quartz. The field 

determination of bismuthinite was verified chemically, and the 

bismutite was identified by J. J. Glass of the Geological Survey. The
DESCRIPTIONS OF MINERALS 51

bismutite is very fine grained but has the following characteristics: 

some grains are isotropic and others biaxial negative; mean index of 

refraction of biaxial grains is 2.20; the mineral occurs as square plates, 

is yellowish to light green, gives positive bismuth test, and effervesces 

with acid. X-ray examination by J. M. Axelrod, of the Survey, confirms the identification. A related alteration mineral also has been 

found: it is a greenish gray, amorphous or cryptocrystalline bismuth 

carbonate.

It is reported that bismuth minerals were mined at the Crystal 

Silica property prior to 1900, but the amount and source are unknown.

URANINITE AND RELATED MINERALS

The inner intermediate zone of the Hyatt pegmatite contains 

uraninite and its alteration products in minute quantities. Smoky 

quartz and reddish-brown feldspar are found in the vicinity of radioactive minerals. It is reported that masses of uraninite as large as 

an inch in diameter were found in the inner intermediate zone when 

the deposit was first opened. Still visible are masses of quartz as 

much as 4 feet in diameter which darken inward (from gray edges to 

jet black centers) indicating that uraninite was once present. Fractures in the quartz contain scales and flakes of yellow autunite, gray 

metatorbernite, and orange gummite. A specimen from the mine 

dump contains a dozen grains of dull-black uraninite, ranging from 

0.03 to 0.15 inch in diameter, embedded in perthite. Though not in 

actual contact with the uraninite, quartz grains in the specimen are 

black.

Autunite and gummite are present in pegmatite 824, but no uraninite is exposed.

Metatorbernite was identified in a specimen submitted to the 

U. S. Geological Survey Trace Elements Laboratory and is reported 

to have the following properties: radioactive and faintly fluorescent; 

small 2V, uniaxial positive; beta and gamma indices of refraction 

close to 1.632; anomalous blue and purple interference colors in 

anisotropic sections; qualitative chemical tests show the presence of 

P, Cu, and U. It occurs as small green flakes.

No uraninite can be seen at the Big Boulder pegmatite, but the 

intermediate zone contains the alteration products and smoky to 

black quartz. The associations are similar in the two deposits. The 

zones contain beryl, scrap mica, phosphatic minerals, columbitetantalite, smoky quartz, and perthite. The Hyatt deposit contains, 

in addition, bismuth minerals.

Despite the variety of uranium-bearing minerals in pegmatites, 

the total quantity of uranium obtainable from them is probably minor 

or negligible. The subject has been reviewed by Page (1950, p. 12-34).
52 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

The writer estimates that the uraninite content of the exposed parts 

of the intermediate zones at the Hyatt and Big Boulder deposits is of 

the order of O.OOOX percent.

RELICT SPODUMENE

No unaltered spodumene has been found in the Crystal Mountain 

district, but there is evidence that spodumene crystallized in the 

interior zones of the Hyatt, Big Boulder, and Buckhorn Mica pegmatites. The spodumene was altered to an exceedingly fine-grained 

aggregate of albite and sericite which has preserved the lathlike shape 

and the lamellar structure parallel to the (100) face. Some pseudomorphs are 3 feet long and 2 to 4 inches thick. Spectrographic 

analyses of two specimens of the aggregate were made by A. T. 

Myers, Trace Elements Section, Denver Laboratory, U. S. Geological 

Survey. Each specimen contains lithium in the order of O.X percent; 

the specimen from the Big Boulder pegmatite is slightly richer than 

the one from the Buckhorn Mica pegmatite.

The field relations indicate that, during the crystallization of the 

Big Boulder pegmatite, perthite crystallized hi the outer and upper 

parts of the wall zones and as a hood in the intermediate zones, albite 

formed in these units (cleavelandite in the inner parts), and lithium 

crystallized as spodumene in the inner part of the intermediate zone. 

The spodumene, however, was not in equilibrium with the rest-liquid 

during later crystallization and was altered by reaction to albite and 

sericite. The resorbed lithium was redeposited, partly with iron and 

manganese phosphates as lithiophilite-triphylite and partly as a minor 

element in lithium-bearing muscovite and sericite.

The sequence at the Buckhorn mica pegmatite is similar, but simpler mineralogically-. Albite and quartz grade inward into

and quartz, and the spodumene that crystallized with

and quartz was later altered by reaction; the freed lithium

was incorporated in micas.

HEMATITE AND MAGNETITE 

Hematite and. magnetite were found, in pegmatite S99. This quartz

pegmatite contains tourmaline crystals, as much as 0.2 inch in diameter and. 1.1 inches long, a-nd ono small mass of hematite and. magnetite, 0.3 inch by 0.4 inch, and 0.03 inch thick. No feldspar or mica

'was found. Lodestone occurs intergrown with quartz and muscovite

near the east margin of the quartz core of the Crystal silica pegmatite.

CHRYSOBERYI 

Pegmatites 1039j 1148 ; 1155; and 1158 contain asparagus-green to

yellowish-green chrysoberyl in plates, masses, and imperfect crystals. 

The crystals are found in groups of 3 to 8 per pegmatite and are 0.05
DESCRIPTIONS OF MINERALS 53

to 0.1 inch thick and 0.2 to 0.6 inch long. The chrysoberyl in pegmatite 1039 occurs in the core of perthite-quartz-plagioclase pegmatite. 

At the Beryl No. 5 prospect (fig. 1) a fracture in quartz is filled with 

many small plates of chrysoberyl which form an almost solid layer 

0.02 inch thick, 4 inches long, and 2.5 inches wide. Many of the 

plates are stellate twins showing fine featherlike striations on the 

(100) face;

Chrysoberyl is a rare mineral in the Crystal Mountain district, but 

5 miles to the north at the Wisdom Ranch prospect (SK sec. 5, T. 7 

N., R. 71 W.) described by Hanley, Heinrich, and Page (1950, p. 

102-104) numerous plates and masses of chrysoberyl have been found; 

however, it is quantitatively rare, even at the Wisdom Ranch prospect.

MIAROLITIC MINERALS

An irregular miarolitic cavity in the Hyatt pegmatite contained a 

compact mass of a yellowish-green micaceous mineral and minute 

crystals of a variety of minerals.. The cavity was about 0.4 inch in 

average, diameter and occurred in a fine-grained aggregate of quartz, 

plagioclase, and. muscovite that fill the interstices between large 

perthite masses. The material was identified by J. J. Glass, of the 

United States Geological Survey.

The micaceous material is sericite; and the associated minerals, in 

the order of their abundance, are bertrandite, apatite, fluorite, tourmaline, hematite, and limonite.

The sericite is dominantly platy, but a small portion is fibrous, 

has a waxy luster, and does not yield a lithium flame. It is biaxial 

negative, 2V variable from 30° to 70°, the finer grained material 

having the smaller optical axial angle. The gamma index is 1.577. 

A quantitative spectrographic analysis of the sericite, made by J. D. 

Fletcher, of the United States Geological Survey, is given in table 10.

TABLE 10. -Quantitative spectrographic analysis of sericite from the core of the 

Hyatt pegmatite, Crystal Mountain district, Colorado

IPlate examined for Ag, Mo, W, Ge, Pb, As, Sb, Zn, Cd, Tl, Co, Nl, V, La, Th, Nb, Ta, and U, but not 

found. J. D. Fletcher, spectrographer]

Constituent Percent 

BQ...... ................... 0 04

Cu.^-_-_- -.-_-_--,._ ___ 002

Sn.._. ___ ..'. _ - _____ 01

Bi _ _....- __ . ____ . _ 004

Mn.... ._.....-.,....-.._.. 3

Ga -_----__---, _-_-J-.-.- 008

Cr.___-______--_--. _-____-_ 0002

Sc_. --___- -_-.--__ _ ------ 001

Constituent 

Ti_._ .-.-.--..-..-.--..

Sr._. ..................

Ba. -----------------

B_.__ ..._..-.....-.-.-.

Fe203 .-. ---------------

CaO--------.-_------

MgO- ...............

Percent 

.... 0.02

-..- .0007

-.-- .01

---. .04

...- .02

...- .3-0.6

-..- .1-.3

.-.- .1-.3

The bertrandite is colorless, exhibits twinning,. and has perfect 

cleavage in three directions. The mineral is biaxial negative, the 

angle 2Fis 78° to 80°, extinction is parallel. The indices of refraction
54

are Na, 1.590; Np, 1.603; and Ny 1.614. Bertrandite is a rare hydrous beryllium silicate (H2O 4BeO 2SiO2).

The apatite has the properties of fluorapatite: uniaxial negative*,, 

specific gravity about 3.3; the pale-grayish, sapphire-blue fragmentshave indices of refraction Ne, 1.630 and Nu 1.633, and the colorless fragments have indices Ne, 1.632 and Nu 1.635.

Tourmaline is present as small columnar crystals on albite at theedge of the cavity. It is black in the hand specimen but brown to> 

greenish gray in thin grains. It is uniaxial negative with the indices 

Nt 1.626 and Nu 1.646.

Hematite and limonite are present as crustlike specks on the cleavage planes of the albite and as pale-pink and pale-yellow stains throughout the specimen.

RELATION OF PEGMATITES TO WALL BOCKS AND STRUCTURE

WALL-ROCK ALTERATION

The alteration of schist and granite wall rock in contact with pegmatites of the Crystal Mountain district is in most places inconsequential. Black tourmaline has been added to schist and granite in 

quantities ranging from negligible to 40 percent; intense alteration isunusual and rarely extends more than 5 inches from the contact. 

Tourmaline crystals range from microscopic sizes to an inch in length. 

Intensely altered mica schist contains about 20 percent tourmaline. 

Tourmalinization decreases outward from the contact and disappears 

at a distance of about 2 feet. Because tourmaline is a common accessory mineral in some schist layers, as well as being widespread around 

most pegmatites, it has been recorded as a wall-rock alteration product only where it is especially concentrated. Bannerman (1943,

p, 9) describes black tourmaline as a particularly common mineral in 

the contact zones in many districts in New Hampshire.

Tourmaline forms rosettes of acicular crystals in minute fractures 

between pegmatite and granite in the northern multiple granite sill..

The needles are 0.1 to 1 inch long and as much as 0.05 inch in diameter;

and the rosettes or clusters are no more than one-tenth of an inch

thick. The tourmaline is attached to the pegmatite but not to the

granite. Tourmaline rosettes have been found in only a few places^

their exposure depends on fortuitous breakage.

Tne granite in contact with pegmatite is almost invariably silicified

sufficiently to increase its resistance to erosion. The silicified Wall

rock forms low ridges flanking recessed pegmatites on the bare 5UTfaCeS of the northern multiple sill. Narrow ridges of resistant granite 

are found along jointlike Cracks WhlCh are Ul SOUIC

with pegmatites.
RELATION OF PEGMATITES TO WALL ROCKS AND STRUCTURE 55

Granite and schist in direct contact with the Hyatt, Big .Boulder; 

and Buckhorn Mica pegmatites were analyzed for BeO, and the determinations are given in tables 11 and 12. Most samples represent 

about 1 foot of rock at the pegmatite contact, but samples from drill 

holes HY-4, HY-6, BB-4, and BBt-2 represent greater distances. 

The locations of the samples are given in figures 13-20 and 28-32. 

The range of BeO content in the granite is from a trace to 0.015 percent; the average of samples without visible alteration is 0.005 percent, and the average of all granite samples (table 11) is 0.007 percent. 

As the limit of accuracy of the analytical method is about ±0.001, 

there is no significant difference between the averages, and it is 

apparent that addition of BeO to granite is not important.

TABLE 11. BeO content of granite near Hyatt pegmatite, Crystal Mountain

district, Colorado

Drill hole

HY-1. ..-... 

HY-1. -... .

HY-2.. ......... .....

HY-2.... .... ..

HY-3.. ............. .

HY-3_. ........ ......

HY-4.. ..............

HY-4.-.-.- .

HY-4................

HY-4.. ..............

HY-4 .... 

HY-4... .... ......

HY-4.. .-. .-

HY-5... ..........

HY-6. ............

Sample 

no.

C 223

C 231

C 201

C 218

C 175

C 200

C 145

C 159

C 160

C 163

C 165

C.167

C 173

C 144

C 123

Footage

56.8- 57.4

85. 0- 95. 0

104. 0-104. 9

165.6-166.8

131.8-132.5

209. 6-210. 6

169.0-170.0

213. 4-214. 5

217. 5-218. 7

220. 9-221. 8

222. 2-224. 4

227.8-228.2

234. 3-235. 0

83. 6- 85. 0

54.0-55.0

BeO 

content 

(percent) '

0.011

.015

.008

.009

.004

.008

.009

.001

.009

.001

.01

.001

.006

.01

.0033

Material Included In the granite

Apllte and pegmatltlc stringers.

None.

Quartzose patches.

Pegmatltlc blebs.

None.

Pegmatltlc patches.

Quartzose and pegmatitlc patches.

One sllckenslded quartz vein.

1 Quantitative .spectrographlc analyses of C 123 and O 144 by Saratoga Laboratories, and the rest by 

National Spectrographlc Laboratories.

The range of BeO content in altered schist at the contact with 

pegmatite is from a trace to 0.041 percent. Schist that is not visibly 

altered contains an average of 0.003 percent BeO. The average BeO 

content of all samples in table 12 is 0.008 percent. Pegmatitic 

stringers and impregnations add BeO to the schist, but there is no 

simple and consistent relationship between the addition of pegmatitic 

material and the beryllia content. The average of all schists, 0.008 

percent, and of all granites, 0.007 percent, indicates that both types 

of country rock are about equally enriched in beryllia, though the 

content in the schist is more varied.
TABLE 12. BeO content of schist near the explored deposits, Crystal Mountain

district, Colorado

Drill hole

HY-1... .... .........

HY-1- . 

HY-6 .... ...... ...

HY-6... -_.._ ... -.

HY-6.___. _..__ ..-

BB-3.. -.____ ...--

BB-4. . ...........;..

BB-4-. ......... -----

BB-4.-.-..... ......

BB-5.... ... ..... .

BB-5.. ............ ..

BH-1...... .,-.-. -

BH-2. ...............

BH-2. ...........:...

BH-2... ..........

BH-2. ............. ..

BH-2..... ,.....--

BH-3-... .-..... -

BH-3- .... .... ....

BH-4.. ...... .........

BH-5. ...............

Sample 

no.

C222

C225

cm

C113

C116

C110

079

C95

C96

C63

C78

C56

C40

C41

C48

C50

C 55

C26

C39

Oil

CIO

Depth (in 

feet)

55. 0- 56. 8

60. 0- 62. 0

29.0- 30.0

34. 0- 34. 4

39.2-40.5

82. 4- 83. 2

56. 0- 57. 0

130.8-133.0

133.0-134.1

107. 7-109. 0

178.1-179.1

72. 5- 73. 5

84. 0- 86. 8

86. 8- 90. 5

112. 7-114. 4

115.1-120.0

132.0-133.2

64. 0- 65. 2

89. 0- 90. 0

17.8- 18.8

131. 5-132. 4

BeO content (percent

0.001

.001

.0180

.034

. 0055

.0027

.0027

.0045

.0088

.0019

.0046

.0028

.041

.0078

.015

.0029

.0038

.0028

.0021

.0016

.0028

Nature of the schist

Toufmalinized; weathered.

Do.

Do.

Do.

Do.

Do.

Pegmatitic stringers and blebs.

Do.

Not visibly altered.

Tourmalinized.

Not visibly altered.

Silicifled.

1 Quantitative spectrographic analyses of C 222 and C 225 by National Spectrographic Laboratories and 

the rest by Saratoga Laboratories.

CONTROL, BY WALL-ROCK STRUCTURES

PEGMATITES CONCORDANT WITH SCHISTOSITY

Pegmatites concordant with the foliation of the schist have simple 

lenticular shapes. The exact ends of concordant pegmatites are 

rarely exposed, but from the steady narrowing of the exposed parts of 

the bodies and the diminution of the size of float, it is inferred that the 

ends of the pegmatites are wedge shaped.

PEGMATITES DISCORDANT TO SCHISTOSITY

Pegmatites that are discordant to the foliation of the schist usually 

occupy simple fractures. The contacts may be irregular in detail, 

but the general shapes of the discordant pegmatites are remarkably 

regular in comparison with those in other districts. For abundant 

maps and descriptions of pegmatites of more complex shape, the. 

reader should refer to papers by Bannerman (1943), Cameron and 

others (1949), Hanley, Heinrich, and Page (1950), Jahns (1946), 

Olson (1942), and Smith and Page (1941). Some of the more irregularly shaped bodies in the Hyatt area (pi. 2), such .as pegmatites 448.

and 645, are multiple bodies xvhose members are moderately straight 

and simple. The branching patterns of pegmatites 645, 673, 674,

and 675 are produced by concordant offshoots of discordant bodies.

Pegmatite 1108 follows intersecting fractures, and pegmatite 1045 is 

Concordant in the eastern half and discordant in the western half. 

Irregular pregmatites 442, 463, 190, 248, 249, 898, and 900 hftTC been

but little eroded and might present more regular outlines if they were 

more completely exposed.
RELATION OF PEGMATITES TO WALL ROCKS AND STRUCTURE 57

Pegmatite 432 seems to have been the feeder for the flat-lying 

pipelike body which constitutes pegmatite 430. Pegmatite 432 is a 

steeply dipping body that trends eastward; pegmatite 430 branches 

northward from pegmatite 432. The lower contact of pegmatite 432 

is an irregular surface with an average southerly dip of 20°, exposed in 

small outcrops for 200 feet north of the junction. The structure 

controlling the emplacement of pegmatite 430 is not exposed, but it 

may have been the low-angle line of intersection of two nearly parallel 

joints with opposed directions of dip. Other pegmatites in the area 

show apophyses following planes of weakness that diverge from the 

structure localizing the main body: the southwestern end of the 

concordant branch of pegmatitie 645 follows a plane dipping 45°- 

55° NE.; the southwest-trending discordant branch of pegmatite 846 

rests in part on a plane striking N. 70° W. and dipping 25° NE.; 

along the south side of pegmatite 695, the pegmatite bulges outward 

for a few inches to rest on a joint striking N. 31° W. and dipping 

6° NE. in schist.

PEGMATITES FILLING JOINTS IN GRANITE

' Pegmatites that occupy joints in granite are tabular bodies with 

straight courses and angular bends. Some joint-controlled pegmatites 

end abruptly and squarely against other joint surfaces, and some 

taper to a knife edge as the walls converge. Most joint-controlled 

pegmatites lose their identity in a network of other joint-controlled 

bodies. Pegmatites form a veritable maze of interconnected bodies 

at the western end of the northern multiple granite sill: in the Avestern 

part (pi. 2) are shown all the pegmatites more than 5 feet in width 

and r as many of the remaining bodies more than 1 foot wide as can 

be plotted at a scale of 1: 6,000. Eastward from pegmatite 300, all 

bodies more than 1 foot wide and many of the persistent narrower 

ones are mapped. North and east of pegmatite 105, bodies less than 

3 inches wide and less than 50 feet long are common but were not 

mapped.

The relation of many bodies to wall-rock structure is not apparent 

in the field and only those that are clearly joint-controlled are so 

designated in appendix B. The various networks of pegmatites 

centering around pegmatites 278, 375., 332, and 384 are similar to the 

more extensive and intricate networks made up of narrower bodies.

: PEGMATITES PARALLEL TO FLOW STRUCTURE

. Many pegmatites within granite sills are parallel to the flow structure or are along the hanging wall or footwall of the sills. These, 

bodies have the same structural characteristics as pegmatites concordant with the schist. Pegmatites 85, 87, and 88 dip southward 

parallel to the foobwall contact of the northern granite mass and give
58 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

the impression of being concordant hi the longitudinal fractures of 

marginal sills.

AMOEBOID PEGMATITES IN GRANITE

There are small irregular patches of pegmatitic material in parts 

of the large multiple granite sills that are not fracture controlled 

pegmatites. They are amoeboid in shape, with intricately embayed 

outlines and gradational contacts; but they are clearly fine-grained 

pegmatites. The material has the minerals typical of the granitic 

pegmatites of the district: perthite, plagioclase, quartz, and muscoyite and contrasts sharply with the biotite granite host rock. These 

bodies range from a few inches to 2 feet in maximum width and from 

1 to 5 feet in maximum length. They are not alined in any recognizable pattern with respect to the structure of the enclosing granite. 

Comparison of the mineralogy of the pegmatite with the host indicates 

that the pegmatitic material contains more plagioclase and muscovite, 

less potash feldspar, and no biotite or magnetite; the pegmatite 

therefore must have crystallized from material higher in alkalies and 

water and lower in iron than the surrounding granite.

These pegmatitic patches are so small, irregular, and rare that they 

are quantitatively unimportant, but they pose an interesting genetic 

problem. The writer interprets these pegmatitic patches as segregations of material rich in hyperfusibles which probably originated by 

differentiation of the granite after emplacement as a sill. The hyperfusibles apparently accumulated in pockets as the sill solidified. 

Irregular patches of this kind would correspond, according to this

interpretation, to the early generation of pegmatites discussed by 

Grout (1932, p. 220-221). The origin proposed for these pegmatites 

is similar to that postulated by Kelley and Branson (1947, p, 708) 

for the pegmatites of Rabb Canyon, N. Mex.

CONTROL BY WALL-ROCK MINERALOGY

Six broad mineralogic types of pegmatites are recognized hi the 

area/i t)Ut no Single type is restricted to any particular lithologic or

Structural environment. Garnet does not occur more abundantly in

pegmatites under one condition than any other. The distribution of 

moderate to intense tourmalinization of country rock shows no

preference for association with a mineralogic type of pegmatite.

Tourmalinization does seem more prevalent in granite than in schist, 

but the writer hesitates to draw conclusions from this simply because

tourmalinized granite is so muck more striking to the eye than tourmalinized schist; equivalent tourmalinization in schist might go

Unrecorded, particularly because tb.e granite is usually- better exposed

than schist. Only beryl exhibits a discernible preference in distri-
RELATION OF PEGMATITES TO WALL ROCKS AND STRUCTURE 59

Nation. It is slightly more abundant in discordant than in concordant 

pegmatites in schist and is found in more deposits away from the 

large multiple granite sills than immediately adjacent to them. (See 

.table 7.)

Throughout the Georgetown quadrangle, Ball (1908, p. 64) finds a 

ifairly constant relation between the mineralogy of the country rock 

.and that of the pegmatites. There are many exceptions, but the 

'following correspondence is noted:

1. Biotite-bearing pegmatites are mostly in biotite-bearing older 

granites.

2. Hornblende-bearing pegmatites are chiefly in quartz diorite and 

.hornblende gneiss.

3. Muscovite-bearing pegmatites occur mostly in the Idaho Springs 

formation.

4. Pegmatites in quartz monzonite areas are characteristically 

without ferromagnesian minerals, and many of them contain, instead 

«of an alkali feldspar, a soda-lime feldspar.

5. Allanite-bearing pegmatites are conspicuous in allanite-bearing 

quartz monzonite. Ball (1908, p. 64) concludes that in the Georgetown area the pegmatite fluid abstracted, prior to solidification, suffi-

 cient material from the enclosing rock to modify the chemical composition of the pegmatite. Ball infers that magnetite was,an original

 constituent of the pegmatite magma because it alone of the ferromagnesian constituents of the pegmatites is not influenced by the

:rock intruded. In the Montezuma quadrangle Levering (1935, p. 

15-16) .found the same general relationship between the composition

 of the country rock and the pegmatites; he adds that quartz-sillimanite-tourmaline-bearing pegmatites occur in quartz-sillimanitetourmaline-bearing schist. Lovering describes a pegmatite trans- 

.grossing the contact between biotite granite and muscovite schist: 

the pegmatite contains biotite between granite walls, muscovite bevtween schist walls, and both biotite and muscovite in the vicinity of 

.the contact between granite and schist.

The sills of Mount Olympus granite in the Hyatt area are everywhere rich in biotite despite their irregularities in texture, fabric, 

.and color. The schist contains biotite in all exposures. With three 

.minor exceptions muscovite is the only mica in the pegmatites. No 

.biotite has been found as an essential constituent or even as an important accessory in any deposit. Sillimanite is a common minor 

.accessory in the schist, but only one small cluster of sillimanite (in

 pegmatite 1146) has been found. Garnet and tourmaline are common 

.accessories in the schist and are abundant in and near pegmatites; 

itourmaline, .at least, is native to the granite; therefore, these minerals

.295165 ,55-
60 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

do not offer a means of correlating mineralogy of pegmatite with wall 

rock. The widespread tourmalinization of granite and schist and the 

moderate silicification of granite indicate that solutions escaped from 

the pegmatite magma and contributed material to the country rock, 

but the compositions of the pegmatites do not indicate significant or 

even any detectable assimilation of wall rock.

MINOR ELEMENTS IN WALL ROCKS

Analyses of 24 samples of wall rock show small but generally consistent amounts of rare elements. In the course of the exploration, 

the drilling of some holes furnished cores of virtually unweathered 

granite and schist. Samples of Wall rock for spectrographic analyses 

were cut from cores at the Hyatt, Big Boulder, and Buckhorn Mica 

deposits. Each sample is half of the drill core split from a 5-foot 

section; the sections are taken at 15-foot intervals from the pegmatitecontact but do not include wall rock within 10 feet of the pegmatite. 

The positions of the 24 wall rock samples are marked in figures 13, 14 r 

19, 20, 28, and 30, and the semiquantitative spectrographic analyses 

are given in table 13.

The analyses indicate that the granite contains small and erratic 

quantities of silver, molybdenum, and a trace of bismuth not found in 

the schist; and the schist contains small but consistent amounts of 

yttrium and lanthanum not present in the granite. The schist is 

also richer than the granite in cobalt, chromium, vanadium, zirconium,, 

boron, and magnesium. The granite seems to have a somewhat 

greater amount of lead, calcium, strontium, and barium. The differences, however, are not striking and are no more than one unit in. 

the order of magnitude scale. In samples taken more than 10 feet 

from the contact, there is no indication of a systematic increase or 

decrease in the content of any component in either the schist or thegranite outward from the wall of the pegmatite.

If there were such systematic variations, it might indicate that the 

emplacement and crystallization of the pegmatite had effected some 

changes in the surrounding rock by the addition or subtraction of 

material. The absence of discernible systematic variation means 

that either the contact aureole is so large that the samples represent 

rocks that have been affected equally, or the wall rocks have been so 

little altered chemically that the change is not detectable with the 

methods used. The first alternative seems so improbable that the

wi-iter believes the analyses in table 13 are truly representative of the

trace elements in the normal country rock at each deposit. If there

is a contact aureole, it must extend less than 10 feet from the pegmatite.
RELATION OF PEGMATITES TO WALL ROCKS AND STRUCTURE 61

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Property and location

Hyatt pegmatite, NEJ*£ NVf^ 

sec. 28, T. 6 N., R. 71 W.

Big Boulder prospect, SEMsec. 

36, T. 7N., R. 72 W.

Buckhom Mica mine, SW^sec. 

29, T. 7N., R. 71 W.

Wall rock

Kotite granite - .

Quartz-Hi ica 

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... .do ., .... -

Drill 

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HY-1

HY-2

BB-4

BB-5

BH-1

BH-3

Depth (in 

feet)

100 -105 

30 - 35 

10 - 15

30 -35 

50 - 55 

70 - 75 

90 - 95 

110.2-115.2 

130. 2-135. 2 

150 -155

16 - 21 

36-41

7-12 

27 -32 

47 - 52 

67-72 

87 - 92

12 - 17 

32 -37 

52 - 57 

107 -110

7-12 

27 -32 

105 -110

Sample

C232 

C233 

C234

C235 

C236 

C237 

C238 

C239 

C240 

C241

C242 

C243

C244 

C245 

C246 

C247 

C248

C249 

C250 

C251 

'C252

C253

C254 

C255

Or

O.OOX 

.OOX 

.OOX

.OOX 

.OX 

.OOX

.ox

.OOX

.ox

.OOX

.ox 

.ox

.ox 

.ox 

.ox 

.ox 

.ox

.ox 

.ox 

.ox 

.ox

.ox 

.ox 

.ox

V

O.OOX 

.OOX 

.OOX

.OOX 

.OOX 

OOX 

.OOX 

.OOX 

.OOX 

.OOX

.ox 

.ox

.ox 

.ox 

.ox 

.ox 

.ox

.ox 

.ox 

.ox 

.ox

.ox 

.ox 

.ox

Y

O.OOX 

.OOX

.OOX 

.OOX 

.OOX 

.OOX 

.OOX

.OOX 

.OOX 

.OOX 

.OOX

.OOX 

.OOX 

.OOX

O

1 Plateexamjned. for Oe, Sn, is, Sb, ZD, Cd, Tl, Nb, and Ta, but not found.
RELATION OF PEGMATITES TO WALL ROCKS AND STRUCTURE 63 

AGE RELATIONS OP PEGMATITES

The sills of Mount Olympus granite were intruded over a period of 

time, probably from a magma source to the south that might have 

been subsidiary to the Pikes Peak granite. Minor variations in 

composition of the granite, major variations in its texture and fabric, 

and the structural relations of the sills to the schist and to each other 

are evidence that the sills were emplaced as successive injections. 

Quartz veins, less than 3 inches in width and not more than a few tens 

of feet in length, were deposited in fractures that formed late in the 

cooling history of the sills. After the granite was well crystallized, 

joints developed which in some places cut across the margins between 

members of the multiple intrusives and across the contacts between 

schist and granite. Pegmatites were emplaced in the joints, the 

walls moving apart so as to cause a few inches of displacement of the 

quartz veins.

The pegmatites were also emplaced over a period of time. The 

mineralogic types, limited in number as they may be, correspond to the 

progressive changes in composition of a granitic magma during 

crystallization. The mineralogic types are unsystematically intermingled throughout the area, apparently indicating that the pegmatitic materials were fed sporadically into the area from an underlying 

source of magma undergoing fractional crystallization. From the 

relations in the Georgetown area, Ball (1908, p. 64) concluded that 

the pegmatite magmas left the cooling mass of granite at widely 

differing times and themselves differed from each other in chemical 

composition. Lovering (1935, p. 15), states that the structural 

relations of the pegmatites to each other and to other rocks in the 

Montezuma quadrangle indicate that their intrusion took, place over 

a long period. Few of the intersecting pegmatites hi the Hyatt 

area show conclusive age relations. Pegmatite 1192 is younger than 

the northwest branch of pegmatite 1197 and is probably younger than 

pegmatites 1190, 1191, and 1193 (pi. 2). Pegmatites 117 and 116-b 

are parallel; they are cut by pegmatite 116-a. Pegmatite 263 is a 

multiple body, made up of an anastomosing network of pegmatites 

2 to 18 inches thick; it intersects several pegmatites, but only its 

relative age with pegmatite 264 can be determined. Pegmatite 

263 cuts pegmatite 264 as indicated by fine-grained border-zone 

material along two of its branches in pegmatite 264.

ORIGIN

At one time there seemed to be little question that pegmatites were 

true eruptive rocks formed by crystallization of a magma derived 

from a source within the earth's crust. In 1925 this view was changed 

by three independent papers by Schaller, Hess, and Landes. Each
64 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

advocated that part or all of the zonal and related internal structures 

of complex pegmatites were developed by hydrothermal or pneumatolytic replacement of earlier formed pegmatite or aplite. These 

ideas have been used and elaborated since by a number of geologists, 

notably Landes (1928, 1933), Gevers and Frommurze (1929), Anderson (1931), Fersman (1931), Bjorlykke (1937), Quirke and Kremers 

(1943), and possibly by Uspensky (1943). In these papers there 

is the tacit assumption that the pegmatite magma and the later 

fluids of replacement, if any, are derived from granitic magma. By 

any hypothesis of the formation of granite whether by the melting 

of a deep section of the sialic crust, by the differentiation of a basaltic 

substratum, or by the transformation and mobilization of rock 

without a magmatic stage a fraction with granitic composition 

rich in hyperfusibles can be derived which will serve for pegmatite 

magma.

Cameron and others (1949, p. 97-106) have reviewed the literature 

and the field evidence offered by a large number of zoned pegmatites 

in many parts of the country. Additional reviews and evaluations of 

field evidence are contained in district studies by Bannerman (1943), 

Cameron and others (1945), Hanley, Heinrich, and Page (1950), 

Jahns (1946), Olson (1942), Page and others (1953), and Staatz and 

Trites (in press). The mode of origin of internal structures agreed 

upon by these men is summarized below, but no attempt is made to 

review their evidence or arguments.

Pegmatitic magmas are derived as a byproduct of the differentiation 

of granitic magma. They are formed over a period of time and vary 

somewhat in composition, depending on differences in place as well as 

time of escape from the parent chamber. Granitic pegmatite magma 

is composed of the same essential elements as granite: sodium, potassium, aluminum, silicon, and oxygen in large quantities; magnesium, 

calcium, iron, and manganese in relatively small quantities; and 

beryllium, fluorine, boron, phosphorus, lithium, and many less 

common metallic and rare-earth elements in widely differing, but,

generally small, quantities. Water is an important part of the solution W is present in relatively large proportions as compared with

the water content of the parent granitic magma (Ingerson, 1950).

The pegmatite magma invades the country rock in much the same

manner as other eruptive rocks: it moves under pressure, follows the 

path of least resistance, accommodates itself to preexisting structures,

and is capable of deforming its wall rocks. With declining pressure

and loss of heat and some Of the more fugitive mineralizers (boron and 

water, for example), viscosity increases and eventually the magma 

comes to rest. In some magmas crystallization starts before the last 

movements are completed, and gneissic and flow structures develop.
ORIGIN 65

Solidification proceeds from the walls inward and follows the normal order of crystallization of the minerals of igneous rocks. Fractional crystallization of pegmatite solutions rich in mineralizers and 

trace elements produces zones characterized by distinctive mineral 

assemblages arranged in a constant sequence. The process may be 

Interrupted by deformation and fracturing, by escape of hyperfusibles, 

or by intense reaction between earlier formed pegmatite minerals and 

the rest-liquid. Once crystallization starts it does not proceed uniformly in all pegmatites: the development of asymmetrical and 

telescoped zones attest to the fact that the crystallizing magma may

 deposit simultaneously assemblages of differing compositions. The

 differentiation of a pegmatite magma is undoubtedly similar to that 

of other igneous rocks and is brought about by similar processes such 

as liquid streaming, diffusion, and crystal settling. Plagioclase-rich 

.zones in the lower parts, perthite-rich zones in the upper parts, and 

quartz-perthite pegmatite in hoods of zoned pegmatites are too 

common and too consistent in their occurrence to be accidental or 

unique features of particular bodies. The systematic variation in

 composition of persistent or recurring minerals in the zonal sequence 

indicates that fractional crystallization produces a rest-liquid pro- 

.gressively richer in hyperfusibles. As stated by Bastin (1950, p. 8):

A crystallizing magma is a system characterized by changing conditions of

 equilibrium in the still liquid portions. Such changes in equilibrium may lead 

to changes in the composition of the minerals deposited and/or to resolution of 

minerals already formed.

'The unceasing attempt to establish equilibrium between the solid 

phases and the residual liquid phase of the complex system produces 

a host of replacement textures. In the final stages of the process of 

fractional crystallization the rest-liquid becomes so rich in mineralizers by residual concentration that it has more of the characteristics 

of a hydrothermal than a magmatic solution. Movement of the restliquid (or fractions thereof) into solidified parts of the pegmatite or 

into the wall rock produces replacement bodies. There is no evidence that zones or replacement bodies in pegmatites are formed from

 solutions that invaded the pegmatite body from outside sources.

The papers referred to in the preceding paragraphs and the theory 

of origin outlined above are concerned almost exclusively with the 

internal structure of zoned pegmatites. There does not seem to be 

any question that "simple unzoned" bodies, the homogeneous pegmatites, are deposits of orthodox magmatic origin. About 98 percent of the pegmatites in the Hyatt area are not zoned; of the 28 

zoned bodies 43 percent show only rudimentary zoning. Only one 

pegmatite in the Hyatt area is sufficiently well zoned to rank with 

those discussed in previous papers. The study of the Crystal Moun-
66 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

tain district has not disclosed new data concerning zoned pegmatites, 

but it provides supplementary information on a number of points:

1. The district provides examples that confirm the nature and 

sequence of six of the mineral assemblages described by Cameron 

and others (1949, p. 61).

2. There is independent verification that plagioclase-quartz pegmatite should be included as a distinct assemblage preceding plagioclase-quartz-spodumene pegmatite in the general sequence of mineral 

assemblages as proposed by Page and others (1953).

3. Where there is a systematic variation in the composition of beryl,, 

it consistently indicates a centripetal increase in the alkali content of 

the solution from which it was deposited. That is, the later beryl is, 

higher in alkalies.

4. The fracture filling at the Big Boulder deposit shows that the 

shell of partly solidified pegmatite was broken after the border zone, 

wall zone, outer intermediate zone, and a 4-foot thickness of the hood 

were formed; a portion of the solution from which perthite-quart^ 

pegmatite was being deposited was drawn into the fracture; theliquid continued normal crystallization, and perthite-quartz pegmatitewas deposited, which is continuous with and indistinguishable from 

the material composing the hood (pi. 11).

5. The amoeboid pegmatites in granite sills are evidence that 

pegmatites can be formed by segregation of the liquid rich in hyperfusibles which is concentrated in the last stage of the crystallization, 

of granite.

The writer believes the principal contribution that the study of 

the Crystal Mountain district can make to the problem of the origin

of internal structures of pegmatites is in the relation of homogeneous, 

to zoned deposits. What seems like a monotonous array of unzoned 

pegmatites contains many variations in texture, mineral proportion,.

and distribution. There is an insensible gradation from (1) pegmatitescomposed ol uniformly disseminated grains of small size, through (2) 

bodies containing crudely segregated clots of minerals in a homogeneous matrix, and (3) two-zoned pegmatites whose cores are coalescing clots, to (4) multizoned deposits of contrasting mineral assemblages and grain sizes. Each of these groups or kinds passes into thenext in a continuous series containing structures and essential mineralsof the contiguous groups in the series. (See fig, 4.) The zones of the'

multizoned bodies are also gradational units containing some or all

of the structures and minerals of the adjacent zones. No member of 

the series contains evidence of the action of solutions coming from

outside the pegmatite body. All members of the series show the samekinds of changes in grain size and distribution of minerals, and the1 

changes are of the same kinds exhibited by common eruptive rocks.
ORIGIN 67

The relation between homogeneous and zoned pegmatites gives

 some basis for speculation on the factors that control or promote 

.zoning. A series of hypothetical cases will illustrate one set of conditions visualized by the writer which will be compared with a different 

set discussed later:

1. A pegmatite magma containing the same elements as granite

 and in the same proportions as granite, with the addition of the barest

 essentials of mineralizers (perhaps water, boron, and phosphorus) 

to promote supragranitoid grain size, will crystallize as the simplest 

type of homogeneous pegmatite with the composition of assemblage

 3 (table 6).

2. A magma with the same elements but in different proportions 

will crystallize with rudimentary zonal structure.

a. A slight excess of silica will produce quartz clots; a marked

 excess will produce a quartz core, as in assemblage 12.

6. Lesser amounts of silica will leave perthite as the dominant 

:mineral crystallizing at the last, forming clots or a core of assemblage 4.

c. An excess of the elements of plagioclase will promote early 

saturation of the magma with respect to plagioclase and a plagioclase- 

:rich wall zone will form of the composition of assemblage 1 or 2.

These hypothetical cases are believed to be representative of the 

processes that formed the zoned pegmatites of the Hyatt area, with 

the exception of the Hyatt pegmatite. The mineral assemblages

 developed hypothetical^ are the same as those actually found in the 

.area, and the list is limited to assemblages 1, 2, 3, 4, and 12. Assemblage 4 is closely related to assemblage 10, and 1 and 2 are akin to 6,

 but 6 and 10 have not been found except in the association discussed 

below. The recurrence of minerals in nearly identical assemblages 

but with different structural positions within the pegmatites must 

require conditions not commonly met even by those unusual pegmatites that develop two zones.

Variations in proportions of the elements of common graniteforming minerals can produce a limited variety of zones. Other 

factors control or promote the development of the complex patterns

 of internal structure typical of well-zoned deposits: the wide range

 of textures, the recurrence of certain essential minerals in more than 

one assemblage, the marked segregation of accessory minerals, and 

the development of special units (such as perthite-rich hoods) and the 

.growth of replacement bodies. In the Crystal Mountain district the 

.homogeneous pegmatites have the widest range of shape, size, type

 of country rock, and structural environment; therefore, it is not the 

.amount of magma, nor the cooling rate, nor the pressure conditions 

that determine whether or not zones will develop. The well-zoned

 deposits, Hyatt, Big Boulder, the Buckhorn Mica pegmatites, are
68 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

distinctive by comparison with nearby pegmatites only by reason of 

their content of such elements as bismuth, tantalum, niobium, 

lithium, uranium, phosphorus, fluorine, and the rare earths. The 

writer infers that the initial composition of the pegmatite magma, 

particularly the content of minor constituents, determines in most 

magmas whether or not it will become a complexly zoned deposit.

There is no evidence that zoning is developed through the action of 

one of the rare elements listed nor does it seem likely that all are 

necessary. Not all the well-zoned pegmatites contain the same elements. There must also be a lower limit to the concentration and 

combination of minor elements effective in promoting the development of zonal structure because recognizable crystals of minerals 

containing rare or mineralizer elements are found in a few places in 

homogeneous pegmatites. Lithium-bearing compounds are essential 

constituents in four mineral assemblages and are present, at least in 

trace quantities, in so many complexly zoned deposits that the presence of lithium is considered a major factor in promoting extensive 

zoning. The concentration of beryllium does not seem to be important 

in promoting zonal structure. Pegmatites 132, 357, 387, 402, and 

606 contain approximately the same percentage of beryl as the Big 

Boulder and Buckhorn Mica deposits, but they are not zoned; pegmatites 441, 563, 773, 774, 859, and 1039 are zoned bodies but contain no beryl.

The quartz-rich bodies are classed as pegmatites rather than quartz 

veins because most of them contain at least trace quantities of feldspar 

and muscovite and resemble the quartz cores of pegmatites of type I 

(table 5 and appendix B). But, as in the case of the tourmaline-rich 

bodies of type III, they may be transitional genetically between pegmatites of magmatic origin and veins of hydrothermal origin, or may 

actually be products of crystallization from hydrothermal solutions.

MINERAL RESOURCES OF THE CRYSTAL MOUNTAIN

DISTRICT

Beryl, perthite, scrap mica, and cotumbite-tailtalite ar j the principal resources of the pegmatites of the Crystal Mounta n district. 

These minerals a,ro not being mined at the present time b scause the 

grain sizes and the concentrations are too small to be recovered at a 

profit by Land sorting. Tne future of the district depends upon the 

development of milling methods which will profitably separate beryl, 

perthite, mica, and columbite-tantalite from the associated minerals. 

The irregularity of the shapes and grain boundary relationships of

beryl and otner minerals (pi. 8) may necessitate elaborate milling to

effect high recovery of clean beryl.
MINERAL RESOURCES OF THE CRYSTAL MOUNTAIN DISTRICT 69

Beryl is the most important mineral in the district. It is present 

in 78 pegmatites in quantities of 1 ton or more and occurs as a minor 

constituent of at least 271 pegmatites. The beryl grains range 

from microscopic in size to 7 feet long, but most are less than 3 

inches. The beryl content ranges from trace quantities in many pegmatites to about 2 percent hi some units of zoned deposits. It is 

present in all types of feldspar-rich pegmatites. Beryl-bearing pegmatites are not restricted to any special structural environment or 

type of country rock, but there appear to be fewer rich deposits in 

the thousand-foot belts immediately adjacent to granite masses of 

the Hyatt area than in the masses themselves or in the areas farther 

than 1,000 feet from the masses. Discordant beryl-bearing pegmatites in the Hyatt area contain richer deposits than the concordant 

pegmatites.

Beryl has been produced from fortuitous exposures, and there has 

been comparatively little waste rock to move. The top of the Hyatt 

pegmatite has been eroded to the level of the inner intermediate zone 

and many large crystals were exposed before mining. Greater-thanaverage thicknesses of beryl-rich rock were available for mining in 

the gentle folds of the crest of the same zone in the upper opencut 

(pi. 9). Future mining will undoubtedly expose large crystals, but 

the principal reserves of beryl are in grains less than 3 inches in size. 

The pegmatites will have to be milled to recover the beryl, and the 

reserves of potash feldspar, scrap mica, and columbite-tantalite will 

constitute byproducts of value.

Perthite constitutes as much as 70 percent of some pegmatites, but 

more commonly ranges from 20 to 60 percent. It makes up 96 percent of the core of the Hyatt pegmatite. The perthite grains in most 

pegmatite range from microscopic in size to 15 inches; only in zoned 

pegmatites are there perthite crystals as much as 10 feet in diameter. 

The average size of perthite grains in the district probably does not 

exceed 3 inches. Perthite of such small average size and intergrown 

with other minerals is not exploitable at this time.

Muscovite is a minor constituent of the pegmatites, but it probably 

could be recovered by almost any milling process and is therefore a 

potential byproduct of value.

Columbite-tantalite is a rare constituent of the pegmatites at the 

Buckhorn Mica mine and Tantalum claim and is present in trace 

quantities in five other deposits in the district. Several hundred 

pounds of columbite-tantalite may be obtained from the Buckhorn 

Mica mine and the Tantalum claim, and small quantities might be, 

recovered from other deposits if they were milled for beryl, .perthite, 

and scrap mica.
70 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

The plagioclase and quartz of the Crystal Mountain district have 

no present value. The plagioclase is dominantly albite and could be 

used in commerce, if recovered by milling. The albite is generally 

fine grained, grayish white to pink, and intimately intergrown with 

other minerals; it seems improbable that this material could compete 

in the near future with the coarse-grained feldspar mined in other 

districts. The current market for soda spar is more limited than that 

for potash spar. Light-gray to smoky quartz has no special properties 

that make it a salable product.

The pegmatites of Tps. 6 and 7 N., and Rs. 71 and 72 W. have been 

prospected intermittently since about 1934, and it is improbable that 

outcrops of coarse-grained beryl, perthite, or mica have been overlooked. Within some of these pegmatites, however, concealed zones 

may contain crystals that can be hand-cobbed. Three mineralogic 

relationships, which suggest that the pegmatite is zoned, may help 

locate concealed deposits: albite that increases markedly in size and 

developes a platelike structure towards the interior of the pegmatite; 

stringers and patches of fine-grained curved muscovite; and finegrained aggregates of sericite and albite cutting all other minerals.

Many of the pegmatites of this area that contain an unusually high 

proportion of fine-grained beryl in the outer part of the body also 

contain medium-grained beryl in the interior. Beryl is generally 

associated more intimately with plagioclase and muscovite than with 

quartz and perthite; therefore, the plagioclase- and muscovite-rich 

units of zoned deposits and clots of homogeneous pegmatites should 

be examined with care. Certain features of the occurrence of beryl 

are deceptive: in some pegmatites and fracture fillings it is concentrated close to the margin and gives a false appearance of abundance; 

a beryl-bearing fracture filling that cuts across a large barren pegmatite may give the impression that the large pegmatite is rich in beryl.

DESCRIPTIONS OF INDIVIDUAL PEGMATITES

More than 1,300 of the pegmatites mapped in the Hyatt area have

been individually examined and described, and the essential information as to their size, shape, structure, and composition is given in

appendix B. Pegmatite numbers correspond with those on the

index map (pi. 5), and the descriptions are arranged in groups according to mineralogic composition as outlined in table 5. Such pegmatites as exhibit special features or constitute nearly ideal examples of

some typical relationship have been discussed in the appropriate

sections of this report. Most of the pegmatites have characteristics

that fall well within the types considered in preceding sections.

Hundreds of pegmatitic patches, small pegmatites, and quartz 

veins were cored in the course of drilling the three zoned deposits;
DESCRIPTIONS OF INDIVIDUAL PEGMATITES 71

some are satellites and offshoots of the main body, some are barely 

more than pegmatitic impregnations of the wall rock, but others are 

individual pegmatities distinct from the deposits being explored.

The small bodies are mineralogically like the homogeneous deposits 

mapped in the Hyatt area, and many are' also like the wall zones of the 

zoned deposits. Analysis of 32 samples shows that BeO is present in 

amounts ranging from 0.001 to 0.50 percent, and averages about 0.03 

percent. Some of the small bodies are as rich or richer in BeO than 

the wall zones of the adjacent zoned deposits. Samples C 21 to C 25. 

(table 14) are taken from a concealed zoned body; it is closely related, 

mineralogically to the nearby Buckhorn Mica pegmatite, but th& 

structural relations are unknown. It is interpreted as an independent pegmatite, not connected directly with the larger zoned body.

TABLE 14. BeO content of concealed zoned pegmatite cored in drill hole BH-3, 

Crystal Mountain district, Colorado

Sample no.

C21......

C22...._.

C23..._._

C24______

C25._--__

Footage

47. 5-48. 4

48. 4-48. 9

48. 9-50. 4

50. 4-51. 2

51. 2-51. 8

BeO content 

(percent) '

0. 0014

. 0043

. 0011

.058

.036

Internal structure and mineralogy

Wall zone of quartz-plagioclase-muscovite

pegmatite. 

Intermediate zone of cleavelandite-quartz

pegmatite. 

Core of quartz pegmatite.

Intermediate zone of cleavelandite-quartz

pegmatite.

pegmatite.

i Quantitative spectrographic analyses by Saratoga Laboratories.

DEPOSITS EXPLORED BY CORE DRILLING 

HYATT PEGMATITE

The Hyatt pegmatite is about 23 miles by road west of Loveland, 

Colo., in the NEtfNWX sec. 28, T. 6 N., R. 71 W., sixth principal 

meridian. It is reached from Drake on U. S. 34 by going west on the 

Glen Haven road for 500 yards and then turning northward on to a 

private road (fig. 1). The private road goes to the Fred Hyatt ranch 

on which the deposit is found.

The deposit was discovered in 1936 by Roy Hyatt, but little work 

was done until September 1942 when it was leased to the United 

Beryllium Ores and Metals Corp. of Denver. The pegmatite was 

mined intermittently during the fall of 1942, and operations continued steadily from June to December 1943 under a financial arrangement with the Reconstruction Finance Corporation. The mine was 

idle from 1944 to 1948. In the spring of 1948 a lease was granted to 

the Beryl Ores Co. who operated the Hyatt mine from May to October 

1948. The mine was inactive during 1949 and 1950. Since 1936
72 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

about 50 tons of beryl, 30 tons of scrap mica, and 400 tons of potash 

spar have been produced. The potash spar was mined from the core 

of the pegmatite and the other minerals from the inner intermediate 

zone. The deposit has been opened by three opencuts and a number 

of shallow prospect trenches. One of the opencuts has been back 

filled and all but one of the trenches have been destroyed by later 

workings. The Hyatt pegmatite is shown both prior to mining and 

after the 1943 operations in two maps and two photographs by 

Hanley, Heinrich, and Page (1950, pis. 13 and 14). The extent of 

the mine after the activities of 1948 is shown in plate 9.

The Hyatt pegmatite was mapped by Hanley and Page in October 

1942, and additional studies and maps were made in September 1943

and June 1944 by Hanley, Heinrich, and Page (1950, p. 99-102).

.In September 1947 the writer and A. J. Lang remapped the deposit.

GEOIOGY

The Hyatt pegmatite cuts across a small pluglike mass of gray 

biotite granite which crops out along the crest of a small anticline in 

quartz-mica schist (pi. 2). Pegmatites are abundant in the vicinity 

but none are zoned bodies though a few of them are beryl bearing. 

The contact between the granite plug and the schist is not exposed, 

and the contact between the Hyatt pegmatite and the granite is 

visible only in the workings on the northwest (hanging-wall) side.

The contact between granite and pegmatite is gradational and 

somewhat irregular. The feldspars and quartz interlock and are 

indistinguishable even under the microscope, but biotite is restricted 

to the granite. Viewed under the microscope the quartz and feldspars 

of the granite exhibit strain shadows, and the biotite flakes are bleached

for a fraction of an inch beyond the limits of definitely recognizable 

pegmatitic material. The force of intrusion of the pegmatite magma 

probably deformed the grains, and solutions escaping from the peg" 

matite altered the biotite. The pegmatite has no border zone in many

places at the contact with granite, and though the position of the

contact can be fixed within a few inches, the attitude of the contact 

can only be approximated. At the contacts with schist the border

zone is well developed, and the attitude is readily determinable,

The Hyatt pegmatite is 305 feet long and has a maximum width of 

70 feet. It is a roughly lenticular, asymmetrical body whose long

axis trends N. 60° E.; it has an average dip of 60° NW. The northeast 

end has a flat plunge to the southwest which steepens in the granite

(pi. 10). The southwest end plunges about 42° northward, so the

pegmatite has approximately the shape of half a lens tapering downward and to the northwest. The core of the pegmatite is crossed by

a curving and branched fracture filled with granular friable gouge
0 HYATT PEGMATITE 73

about 4 inches thick. The fracture has a general trend of N. 50° E., 

dips steeply southeast, and seems confined to the core of the deposit. 

A few 1- to 4-inch, irregular aplite dikes cut all zones of the pegmatite.

The Hyatt pegmatite is divided into the following zones: A wall 

zone of plagioclase-perthite-quartz pegmatite, an outer intermediate 

zone of perthite-quartz pegmatite, an inner intermediate zone of 

plagioclase-quartz-muscovite pegmatite, and a core of perthite 

pegmatite. The wall zone and inner intermediate zone are continuous 

around the deposit, but the outer intermediate zone is restricted to 

the hanging-wall side of the body. Drilling disclosed that in the 

lower part of the body the wall zone contains almost no perthite and 

confirms that the outer intermediate zone is not present on the 

footwall side. The average composition of the entire pegmatite, calculated from the composition of the individual zones, is plagioclase 

50 percent, perthite 35 percent, quartz 15 percent, and muscovite 

less than 1 percent.

The concentration of perthite in the upper part of the pegmatite 

is so marked that zonal boundaries have been drawn (pi. 10) on the 

basis of its distribution.

The upper wall zone consists of about 50 percent plagioclase (albite), 

25 percent perthite, and 25 percent quartz. This zone has an average 

width of about 25 feet but ranges from 1 to 60 feet. The texture is 

fine grained, and the grains average slightly less than 1 inch in diameter, though perthite grains are as much as 4 inches in length. Muscovite is a common accessory in flakes and books from microscopic in 

size to 2% inches in length. Beryl occurs as irregularly disseminated 

euhedral to anhedral blue-green crystals. The sizes and shapes of the 

beryl grains found in the drill core are shown in figures 7-12. Tourmaline is present near the contact as crystals 0.01 to 0.7 inch long, and 

in the southwestern end of the pegmatite as clusters of columnar 

crystals up to 2 inches long.

A sample of the wall zone, weighing almost 300 pounds, was taken 

from the southwest trench (pi. 9). The BeO content determined by 

quantitative spectrographic analysis is 0.078 percent and by the 

nuclear reaction method it is 0.066 percent. An average of the determinations of index of refraction of beryl in this zone shows that the 

beryl contains about 12.4 percent BeO. The analyses, therefore, 

indicate about 0.6 percent beryl in the sample; this is higher than the 

average for the entire zone but confirms the measurement of beryl 

grains made in and near the trench.

The results of chemical analysis and semiquantitative spectrographic analysis of the same sample are given in tables 15 and 16, 

respectively. The proportions of "standard mineral molecules" or 

"normative minerals" are calculated from the chemical analysis
74 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO4

a.

r

\
 107,0

Crack in core

107.7

Part of grain 

missing

 115.6

Crack in core, 

part of grain 

missing

 116.7

120.0

-120.7

144.7

1461

146.8

-147.7

150.2

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

FIGURE 8. Plan of beryl grains exposed on diamond-drill core from hole HY-2, 
76 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

£ 'O rS

S 1 *

2*

il

f g c 

110 CC
HYATT PEGMATITE 77

% 

% -

r-171.8 *

*

 1.72.7 *

4fc

 1733 £

«

 174.6 

^

 180-2

*

1

** 

 1803

. 

» 

 183.0

. ' 

« 

 1817

 186.6

4

 

 189.7

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

FIGURE 10. Plan of beryl grains exposed on diamond-drill core from hole HY-4, Hyatt pegmatite, Larimer

County, Colo.
-41.2

 81.8

I*

-82.2

Grain outlines traced directly from surface of Bx drill core

Reference marks show depth, in feet, from collar of drill hole

5 Inches

FIGURE 11. Plan of beryl grains exposed on diamond-drill core from hole HY-5, Hyatt pegmatite, Larimer

Ooixnty, Colo.
 32.0 *

*

^

 33.0

 35.6

^

*

 37.8

 38.9 ^

%

 41.4

' 41.6

 43,2 4

 500 -

 50-4

^^

^f

%

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

FIGURE 12. Plan of beryl grains exposed on diamond-drill core from hole H Y-
80 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

according to the system of Cross, Iddings, Pirsson, and Washington 

(Washington, 1917). The differences between the hypothetical norm 

and the actual mode are minor: the muscovite present in the rock 

and not included in the norm is represented by corundum, water, and 

part of the quartz and magnetite; the hypersthene in the norm (but 

not in the rock) reflects the presence of a small amount of MgO, and 

FeO in excess of Fe2O3 , which are probably incorporated in minute 

quantities in the feldspars or in the muscovite.

TABLE 15. Chemical analysis and norm of plagioclase-perthite-quartz pegmatite, 

wall zone of Hyatt pegmatite, Crystal Mountain district, Colorado

[A. M. Sherwood, analyst] 

Analysis

'Si02 _. 

A12 03 . 

Na2 0_ 

K2 0_. 

Fe2 03 . 

FeO_. 

CaO_. 

MgO. 

V2 02 _.

Quartz. __._ _ 

Orth.oclase__- 

Albite____. 

Anorthite___ 

Hypersthene.

Percent 

72. 61 

15. 60 

5.85 

3. 88 

.24 

.43 

.35 

. 12 

.05

No 

Percent 

22.5 

22.8 

49.8 

1. 7 

.8

TiO2 __ ------ ._------

MnO.___.___. ------

BaO__. _ -_ _____

U._ -----._.. _-----_

H2 0-._ -.-_.-_---

H2 0+_ ..-_ _-

Total. _____

rm

Corundum- _ _______

Magnetite. __________

Total_-_---_-_

Percent 

....... 0.01

--_____ .04

--.-_-_ .05

 ... .004

---__-. .04

-___.-- .45

_____ 99.714

Percent 

....... 1.0

--_-._- .2

_____ 98.8

Comparison of the analysis in table 16 with the analyses of the 

granite, samples C 232 to C 241 of table 13, suggests that there has 

been little interchange of trace elements between the pegmatite and 

its wall rock. Manganese, barium, strontium, and chromium are

present in similar proportions in the wall zone of the pegmatite and 

in the adjacent granite; but the other elements, magnesium, lead, 

calcium, gallium, vanadium, titanium, and bismuth, are higher or 

lower by at least one unit in the order of magnitude scale.

The lower part of the wall zone consists of about 60 percent plagio- , 

clase (albite) and 40 percent quartz with accessory perthite, muscovite, and beryl. Except for the decrease in perthite content, it resembles the upper part of the wall zone, including concentrations of 

tke same types of beryl. The lower wall zone has a maximum thickU6SS of about 40 feet in the keel and narrows upward along both 

walls to a featteredge. This troughlike body is shown in plate 10. 

The outer intermediate zone is made up of pertkite (55 percent)

and quartz (45 percent). The grains average between 4 and 12 

inches in diameter, but some are as much as 3 feet. Minor amounts
HYATT PEGMATITE . 81

TABLE 16. Semiquantitative spectrography of plagioclase-perthite-quartz pegmatite, 

wall zone of Hyatt pegmatite, Crystal Mountain district, Colorado

[Helen Worthing, spectrographer]

Elements

Over 10.0......_________________ Si

1.0 to 10.0..___._.__...-..__ Al, Na

0.1 to 1.0.___..____...___..__.._. K, Fe

0.01 to 0.1_.___.-___-_---._--._.. Mn, Ba, Mg, Pb, Ca, Gu, Ca, V

0.001 to 0.01______________________ Sr, B, Ti, Bi, Cr

of fine-grained plagioclase, muscovite, and quartz fill interstices and 

fractures in the large grains. Assays of drill core from this zone 

show small amounts of BeO, which probably indicate small grains 

of beryl in the interstitial filling; no beryl has been observed in the 

perthite-quartz pegmatite exposed in the drill core or the upper 

opencut. .The zone extends about 130 feet along the hanging-wall 

side of the deposit and a distance of about 110 feet down the dip. 

Its width ranges from, less than an inch to 7 feet.

The inner intermediate zone of coarse-grained plagioclase-quartzmuscovite pegmatite contains coarse-grained beryl and scrap mica 

that has been mined .intermittently since 1942. This pegmatite 

consists of 50 percent plagioclase, 40 percent quartz, 7 percent 

muscovite, and 3 percent beryl and other accessories. The inner 

intermediate zone pinches and swells, ranging from 2 to 8 feet wide. 

Several gentle folds plunge at low angles to the southwest (pi. 9) 

and probably reflect irregularities in the crest of the pegmatite.

Beryl occurs typically in clusters of both large and small crystals. 

A few small grains are scattered at random in the rock between clusters. Pockets 6 to 12 feet long and extending the full width of the 

zone have been discovered some 10 to 35 feet apart during mining. 

There are poorly exposed parts of the pegmatite as much as 70 feet 

long, in which beryl shoots are not apparent but which have not been 

prospected to confirm the absence of beryl. The beryl ranges in 

diameter from 1 inch to 1 foot, although some crystals are as much 

as 5 feet long. Both anhedral and euhedral beryl are common.

Estimates of rock moved from the inner intermediate zone compared to the tons of beryl produced indicate a beryl content of 2.3 

percent recoverable by hand sorting.

The inner intermediate zone also has yielded scrap mica from 

shoots and streaks of fine- to very coarse-grained muscovite. The 

streaks are from 1 inch to 5 feet wide and from 1 to 30 feet long. The 

largest books are as much as 15 inches long and 6 inches thick, but 

no sheet mica has been obtained from them; the books are heavily 

ruled and wedged and have "A" structure and many mineral inclusions. The zone is estimated to contain an average of 7 percent
82 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

muscovite, and perhaps a quarter of it is recoverable by hand sorting. 

The fine-grained material consists of flakes and books ranging from 

microscopic to 3 inches in diameter, intimately intergrown with 

quartz, plagioclase, tourmaline, and beryl, and oriented at random.

The plagioclase of the inner intermediate zone has a medium 

texture. It is albi-te with a somewhat platy habit, and there are 

small patches which become cleavelandite with white curving plates 

as much as 6 inches in long dimension.

Minor accessory minerals approximately in order of decreasing 

abundance are tourmaline, microcline, garnet, apatite, lithiophilitetriphylite and other phosphates, bismuthinite and its alteration 

products, and uraninite and its alteration products. The accessory 

minerals constitute less than 1 percent of the zone, and no attempt 

has been made to estimate the abundance of tourmaline, microcline, 

garnet, and apatite. The rarer minerals exposed during mining 

operations in 1948 were estimated to be of the following orders of 

magnitude: phosphates other than apatite O.OOX to O.OX percent; 

bismuth compounds 0.008 percent; and uranium-bearing minerals 

O.OOOX percent.

The core of the Hyatt deposit is about 96 percent perthite, 3 percent quartz, and 1 percent of plagioclase, muscovite, tourmaline, 

and garnet. The perthite is very coarse grained and attains lengths 

of as much as 10 feet. Quartz occurs in very coarse masses as much 

as 4 feet in greatest dimension, and as fine-grained inclusions in the 

perthite, and as interstitial fillings. In addition, plagioclase, muscovite, and tourmaline are included in the perthite and fill the spaces 

between perthite grains. Beryl has been found along the margins 

of the core but not in the interior; however, it may be present in the 

center either as small grains in the interstitial material or as inclusions in the perthite, because small amounts of BeO are found in 

spectrographic analyses of the drill samples. The miarolitic cavity 

from the core Of the Hyatt deposit contained bertrandite, a rare 

hydrous beryllium silicate, indicating that a beryllium-bearing 

mineral was deposited at a late stage in the crystallization of the

pegmatite.

The maximum dimensions of the core are 240 feet long, 25 feet

wide, and 100 feet in the plane of dip.

EXPLORATION

The Hyatt deposit was explored by six holes drilled from the hanging wall side of fcKe pegmatite (pi. 9). The elevation of the collar inclination of the hole, and depth drilled are indicated on the map

(pi. 9), the drill logs (appendix A, 1-6), the assay plans (figs. 13-17), 

and the cross sections (pi. 10). For analysis, 58 sludge samples and
RESULTS OF SPECTROGRAPHIC 

ANALYSIS

Sample

S 9 

S 10 

S 11 

S 12 

S 13 

S 14 

S 15 

S 16 

S 17

Sample

C219 

C220 

C221 

C222 

C223 

C224 

'C225 

C226 

C227 

C228 

C229 

C230 

C231

SLUDGE SAMPLES

Depth

(feet)

48. 5 - 52. 1 

52'. 1-55.0 

55.0 - 60.0 

60.0 - 65.0 

65.0 - 67.0 

67.0 - 72.0 

72.0 - 77.0 

77.0 - 80.2 

80.2 - 85.0

CORE SAMPLES

Depth

(feet)

48.2 - 49.0 

50.4 - 53.7 

53.7 - 55.0 

55. 0-56.8 

56.8 - 57.4 

57.4 - 60.0 

60.0 - 62.0 

62.0 - 67.0 

67.0 - 73.1 

73.1 - 76.8 

76. 8-80.2 

80. 2-85.0 

85.0 - 90.0

BeO

content 

(percent) 

0.011 

.023 

.021 

.026 

.029 

.038 

.043 

.045 

.044

BeO

content

(percent)

0.033

.026

.010

Tr.

.011

.013

Tr.

.029

.02

.027

.013

.019

.015

Drill hole HY-1

Elevation 8130 feet

Inclination 52°

Depth 105 feet

20

Horizontal and vertical scale

Analyses of wall rock samples are given in table 2

FIGURE 13. Assay plan of diamond-drill hole HY-1, Hyatt peg
DRILLHOLE HY-2

RESULTS OF SPECTHOGRAPH1C 

ANALYSIS

Sample

S 22 

S23 

S 24 

S 25 

S 26 

S 27 

S 28 

S29 

 S30 S3l'

532

533

534

535

Sample'

C201 

C202 

 C203 

C204 

C205 

C206 

C207 

C208 

C209 

C210 

C211 

C212 

C213 

C214 

C215 

C216 

C217 

C218

.SLUDGE SAMPLES.

Depth

(feet)

105.0 - 111.6 

111.6- 113.6 

113.6 - 117.0 

117.0 - 122.0 

122.0- 127.0 

127.0 - 132.0 

132.0 - 136.5 

136.5 - 141.0 

141.0 - 146.0 

146.0 - 150.5 

150.5 - 153.0 

153.0 - 158.0 

158.0 - 163.0 

163.0 - 168.0

CORE SAMPLES

Depth

(feet)

104.0 - 1O4.9 

104.9 - 108.5 

108.5 - 112.3 

112.3 - 1 13. 3 

113.3 - 1 14.9 

114.9 - 116.2 

116.2 - 122.0 

122.0 - 127.0 

127.0 - 132.0 

132.0 - 136.5 

136.5 - 141.0 

141.0 - 146.0 

146.0 - 150.5 

150.5 - 153.0 

153.0 - 158.0 

158.0 - 163.0 

163.0 - 165.6 

165.6 - 166.S

BeO

content 

(percent) 

0.028 

.016 

. 018 

.070 

.048 

.018 

.030 

.063 

.034 

.026 

.060 

. 14 

.074 

.050

BeO

content

(percent)

0.008

.05

.017

.023

Tr.

.11

.021

.045

.041

/ -7

/I V-f

FIGURE 14. .

Horizontal and ve

Assay plan of diamond-drill hole HY-2, Hyatt pegm
DRILL HOLE HY-3

RESULTS OF SPECTROCRAPHIC ANALYSIS

S 36 

S 37 

S 38 

S 39 

S -id 

S 41 

S 42 

S 43

544

545 

S 46 

S 47 

S48 

S 49

92

93 

C194 

C195 . C196 

C197 

C198 

C199 

C200

SLUDGE SAMPLES

Sample

C174 

C175 

C176 

C177 

C178 

C179 

C180 

C181 

C162 

C183 

C184 

C185 

C186 

C187

(teet

33.0 -

39.0 -

43.5 -

47.0 -

52.0 -

56.0 -

62.0 -

67.0 -

72.0 -

udge re

17.5 -

86.0 -

89.0 -

94.0 -

01.0 -

ORE SAJ

Dept

(feet

96.8 -

31.8 -

32.5 -

39.4 -

44.6 -

48.2 -

51.2 -

53.0 -

54.9 -

57.9 -

59.2 -

62.5 -

64.4 -

67.0 -

72.0 -

77.5 -

78.7 -

83.6 -

86.9 -

89.0 -

94.5 -

39.0

43.5

47. 0

52.0

56.0

62.0

67.0

72.0

75.0

overed

86.0

89.0

94.5

01.0

08.8

tPLES

00.8

32.5

39.4

44.6

48.2

51.2

53.0

54.9

57.9

59.2

62.5

64.4

67.0

72.0

77.5

78.7

83.6

86.9

89.0

94.5

99.3

99.3 - 201.0

01.0 - 202.6

02. 6 - 204. 4

204.4 - 207.9

207. 9 - 209. 6

209.6 - 210.6

(percent

0.020

.017

.0069

. 18

.92

.22

. 11

.046

.045

.064

.055

.055

.074

.064

BeO

content

(percent

0.004

.004

.016

.013

.001

.04

.013

.96

.072

.044

.037

.003

Tr.

.001

.001

.001

.042

.009

.001

.012

.03

.009

.03

.016

.02

.049

.008

H 

+ + ^% + + + 

% 

+ + «r\ + -I- + *

\ /(

\ / . T 

Horizontal and verti

FIGURE 15. Assay plan of diamond-drill hole HY-3, Hyatt pegmati
86 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

05gwo N »nn*,, 0 g > o , ffi , ,,_ 

SsKSSSSSSSSS ngfegSSSSSS-SSS

J§ 3

S £M&

3

D £3 s 

w ^ ^

!sgS5:sge2G*e5ss^£Ja:E;s

J fe< L. JO H r- r* «* w U "-1 " ki ii w

H,, 3 ~-*-.-,NNNNN 0

1-t-OfflOO-lNN e> H to » « »' N « « » o e
HYATT PEGMATITE 87

RESULTS OF SPECTROGRAPHIC 

ANALYSIS

Sample

S69 

S 70

Sample

cm 

cm

C113 

C114 

C115 

C116 

C117 

C118 

C119 

C120 

C121 

C122 

C123

SLUDGE SAMPLES 

Depth 

(feet)

36.0 - 45.0 

45.0 - 55.0

BeO

content 

(percent) 

0.037 

043

CORE SAMPLES

Depth

(feet)

29.0 - 30.0 

30.0 - 34.0 

34.0 - 34.4 

34.4 -.35.5 

35.5 - 39.2 

39.2 - 40.5 

40.5 - 43.5 

43.5 - 48.2 

48. 2-50.0 

50.0 - 50.4 

50.4 - 51.8 

51.8 - 54.0 

54.0 - 55.0

BeO 

content 

(percent) 

0. 0180 

.077 

.034 

.15 

.007 

.0055 

.063 

. 12 

.042 

.0089 

.097 

.025 

.0033

Drill hole HY-6

Elevation 8146 feet

Inclination 45°

Depth 78 feet

F-F

'> '£' ^ ,/

Plagioclase-perthite-quartz pegmatite

Quartz-mica schist

Drill hole location, plate 9 section E-E'

60 Feet

Horizontal and vertical scale 

FIGURE 17. Assay plan of diamond-drill hole HY-6, Hyatt pegmatite, Larimer County, Colo.

121 core samples of pegmatite including the immediately adjacent 

country rock were taken together with 10 core samples for a spectrographic study of the wall rocks.

MINERAL DEPOSITS

The beryl at the Hyatt pegmatite is present in the wall zones, both 

upper and lower, and in the inner intermediate zone. The wall zones 

contain about 0.35 percent beryl, all in grains less than 3 inches in 

size and averaging less than 1 inch. The drill samples from the 

inner intermediate zone indicate the rock contains slightly more than 

1 percent beryl. Production of beryl from the same zone at the surface indicates a recoverable grade of about 2.3 percent beryl. The 

zone was sampled by drilling in three places, but only one rich shoot 

of beryl such as those from which most of the production of beryl 

has been derived was cut. The drilling, however, does indicate that 

shoots of beryl are present in the lower parts of the zone and are not 

restricted to the exposed parts.

The core of the pegmatite contains beryl along its margins. If 

this beryl is enclosed as fine grains in perthite, it may not be recovered except by milling the perthite.

The Hyatt pegmatite also contains scrap mica and perthite resources. Inclusions and interstitial materials are abundant in the
88 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

perthite which is not of the best grade. Minor constituents that are 

of byproduct value are bismuthinite and uraninite.

The dumps at the Hyatt mine are not large but are estimated to 

contain considerable beryl and potash spar. Potash spar could be 

recovered by hand sorting, but not much of the beryl could be recovered economically by this method.

The milling of pegmatite to recover beryl and associated minerals 

of economic value is not within the scope of this report, but it should 

be pointed out that the fine-grained beryl of the wall zones, the 

existing dumps, and the residue of future ; hand-cobbing operations 

in the inner intermediate zone all constitute accessible mill feed. 

Milling of the pegmatite would undoubtedly yield higher recoveries 

of potash spar and mica than those calculated for the resources of 

recoverable minerals. Milling of the perthite of the core might also 

improve the grade of the potash spar by, reducing the content of 

interstitial minerals. !

BIG BOULDER PROSPECT

The Big Boulder prospect is about 37 miles by road southwest of 

Fort Collins, Colo., in the SE% sec. 36, T. 7 N., K. 72 W., sixth 

principal meridian. The prospect is reached from the town of Masonville by going west on the Buckhorn Creek road for 21 miles to a 

bridge and then turning south on an unimproved ranch road to the 

property (fig. 1). The prospect is on State land and is under the 

jurisdiction of the Colorado Board of Land Commissioners with 

offices in the State Capitol, Denver.

The Big Boulder pegmatite was opened in 1936 by Roy Hyatt and 

H. A. Snider. In 1941 about 600 pounds of beryl was mined and 

stockpiled by the United Beryllium Ores and Metals Corp., but the 

mine was idle from 1942 to 1950.

The workings on the property consist of four shallow pits, a small 

cut, and a 10-foot discovery shaft. A large beryl crystal was mined 

from the round pit northwest of the discovery shaft (p. 11).

The wartime investigations Of the United States Geological Survey 

included mapping the Big Boulder pegmatite by Hanley and Page on 

October 2, 1942, and the results of this study are described by

Hanley, Heinrich, and Page (1950, p. 02-03). In August, 1947 the

deposit was remapped by A. J. Lang and the writer,

GEOLOGY

The Big Boulder pegmatite is concordant throughout mOSt Of iliS

length in quartz-mica schist which has af'northward strike and steep

CUP I (S66 Pi. HO The SOUth.ern. end. of tb.e Big Boulcler pegmatite is

in contact with a perthite-plagioclase-quartz pegnlatllG, Dllt ttl6
BIG BOULDER PROSPECT 89

structural relations are poorly exposed; a scale of fine-grained muscovite-rich pegmatite which is continuous with the border zone of 

the east-trending pegmatite (pi. 11) leads the writer to regard the 

perthite-plagioclase-quartz pegmatite as intrusive into the Big 

Boulder pegmatite along a 'plane dipping eastward at an angle of 

about 25°.

Most of the Big Boulder pegmatite is weathered and eroded to 

the level of the surrounding terrain, but the north end forms a prominent knob standing about 30 feet above the flat hilltop (pi. 11). 

A considerable amount of the border zone is exposed on the northern 

half of the knob indicating that the present exposure closely approximates the original shape of the north end of the pegmatite. In some 

places where the border zone has been removed, the muscovite books 

of the wall zone show a preferred orientation, so the position and 

attitude of the contact can be inferred within a few inches of the border.

The Big Boulder pegmatite is a zoned deposit about 245 feet long 

and with a maximum width of 80 feet. It strikes N. 10° E., has an 

over-all dip to the east, and plunges southward the crest more 

steeply than the keel (pis. 11 and 12).

The deposit consists of five zones in addition to the border zone: 

a wall zone of plagioclase-quartz pegmatite, an upper intermediate 

zone of plagioclase-perthite-quartz pegmatite, a lower intermediate 

zone of'cleavelandite-quartz pegmatite, a hood of perthite-quartz 

pegmatite, and a core of quartz pegmatite.

The border zone is well developed along most of the exposed contact 

but rarely exceeds an inch or two in thickness. It is rich in muscovite, 

and is essentially a muscovite-quartz-plagioclase pegmatite with 

grains ranging in size from 0.01 to 1 inch. In a few exposures, the 

schist at the contact with the pegmatite has been converted to granulite, and the border zone is unusually thin or absent.

The wall zone is composed of 55 percent plagioclase and 45 percent 

quartz with accessory perthite, muscovite, tourmaline, beryl, garnet, 

and apatite. Although the texture is fine grained, the grains range 

from 0.01 to 3 inches in length. Anhedral and euhedral beryl crystals 

average 0.7 inch in length, but some are as much as 2.5 inches long. 

Muscovite books are more abundant in the outer few inches of the 

zone than in the inner part and are roughly oriented normal to the 

contact. The zone has a maximum width of 25 feet and averages 

about 12 feet wide, but it is absent in some places. It thickens along 

the keel and toward the south end of the deposit. Although perthite 

is only an accessory mineral in the zone, it occurs principally in local 

concentrations rather than uniform disseminations: for example, 

perthite composes 10 to 25 percent of the material in elongate clots 

at or close to the contact in several places along the east contact
90 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

south of the intruding pegmatite, and at an off-shoot from the west 

contact west of drill hole BB-3 (pi. 11) and at the west contact in 

drill hole BB-4. The perthite is, nevertheless, not abundant enough 

to be classed as an essential mineral in this zone.

The intermediate part of the deposit is essentially an aggregate 

of albite, perthite, and quartz in two zones. Plagioclase-perthitequartz pegmatite forms the upper intermediate zone and plagioclasequartz pegmatite the lower zone. In both intermediate zones the 

plagioclase has the composition of albite, but in the lower part it has 

a platy habit and is of the type designated as cleayelandite. The 

upper intermediate zone is well exposed only in the knob, but the 

lower intermediate zone is poorly exposed and crops out only in the 

weathered southern part of the pegmatite.

The upper intermediate zone is composed of plagioclase (50 percent), 

perthite (30 percent), and quartz (20 percent) with accessory muscovite, tourmaline, beryl, apatite, relict spodumene(?), and uranium 

minerals. The zone is present in the upper part of the body (pi. 12) 

and attains a maximum thickness of 50 feet in the northern bulbous 

part; the average is about 15 feet. The texture is medium grained, 

but the grains are as much as 8 inches in size. Beryl crystals range in 

diameter from 0.1 to 4.5 inches and average about 1.5 inches in 

length. An area 4 feet wide and 25 feet long between the knob and 

the east contact is composed principally of fine-grained albite, with 

some perthite and quartz, which weathers more rapidly than the 

surrounding material and has a different appearance, but grades 

imperceptibly into material typical of the zone. This unit seems to 

be an integral part of the zone that crystallized under some locally

anomalous conditions. The uraninite and its alteration products and 

relict spodumene(?) are exposed on the east wall of the discovery 

shaft along the boundary between the intermediate zone and the

hood.. The amounts of each are negligible.

The lower intermediate zone of cleavelandite-quartz pegmatite is 

composed of about 65 percent cleavelandite and 35 percent quartz. 

Muscovite, perthite, beryl, tourmaline, and garnet are accessory

minerals. Two minute plates of tantalite-columbite were found in 

a core sample. Muscovite occurs as large flakes and books and also

as minute scales with low refractive indices indicating the presence 

of some lithium. The zone forms a troughlike body with a maximum

thickness of 25 feet at tne south end and tapering upward to a knife

edge. The texture is coarse because the common plates of cleavelandite range between 4 and 12 inches in length, though a lew in the 

drill core may be as much as 30 inches long.

The inner edge of tKe lower intermediate zone contains relict

spodumene(?). It is exposed in the eastern end of the northwest-
BIG BOULDER PROSPECT 91

trending trench (pi. 11) and in two places in the drill core of hole 

BB-5. In all places it is within a few feet of the quartz pegmatite 

of the core. The relict spodumene(?) is composed of a very finegrained aggregate of albite and sericite which contains almost 1 

percent lithium. Veinlets of fine-grained albite with a few euhedral 

garnet crystals and some dark phosphatic material cut the cleavelandite-quartz pegmatite.

A hood in the northern part of the Big .Boulder pegmatite is composed of 70 percent perthite and 30 percent quartz. It has a maximum 

thickness of 60 feet (pi. 12). The rock is coarse grained, for the" 

minerals average more than 1 foot in diameter and some perthite 

grains are as much as 6 feet in diameter. Beryl, muscovite, plagioclase, tourmaline, garnet, alteration products of lithiophilite, and 

traces of gummite, autunite, and torbernite are present in the hood. 

A 10.5-ton crystal of beryl was mined from the small pit in this unit 

northwest of the discovery shaft. In addition to this large crystal, a 

number of beryl crystals 12 inches in diameter have been found. 

Some of the quartz in the large shallow pit south of drill hole BB-3 

is dark gray and minutely fractured, but it is not believed to be a 

tectonic breccia. The "breccialike" material is found in masses 

1 to 6 feet in diameter that grade outward into typical light-gray to 

white quartz cut by a few widely spaced joints. The fractures are 

filled with fine-grained perthite. Streaks of fine-grained muscovite 

from an inch to a foot wide and 1 to 5 feet long cut the perthite and 

quartz. Irregular pockets, Yz to 3 feet across, containing garnet as 

the principal mineral, are scattered through this unit. The garnet 

is euhedral to anhedral, closely packed, dark colored, and stained 

with manganese oxides; associated with the garnet are quartz, muscovite, tourmaline, plagioclase, and iron and manganese phosphates.

A fracture filling of perthite-quartz pegmatite extends from the 

northern part of the hood, across the upper intermediate zone and 

wall zone to the contact between pegmatite and schist, and possibly 

into the schist (pi. 11). It is as much as 4 feet wide, has a sinuous 

trace, and probably dips steeply. The fracture filling can be traced 

about 4 feet inward from the boundary between the upper intermediate 

zone and the hood, and there it merges with the perthite-quartz 

pegmatite of the hood.

The core of the deposit is essentially quartz pegmatite with minor 

amounts of cleavelandite, muscovite, tourmaline, and garnet. Spectrographic analyses of drill core from- this zone reveal the presence 

of BeO, but no beryl has been recognized. The long axis of the core 

of the pegmatite plunges 45° S. and is 200 feet long; the maximum 

width is 35 feet, and the greatest thickness is 100 feet. The size of

295165 55-
92 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

the quartz grains is not known, but continuous masses of quartz 5 

feet in length can be seen in the drill core.

Small grains of tourmaline and muscovite form fillings in steeply 

dipping fractures that cut all minerals and zonal boundaries of the 

northern part of the Big Boulder pegmatite (pi. 11). The muscovitetourmaline fillings are as much as half an inch wide, are discontinuous 

along the strike, and occur singly or in groups a foot wide and 6 feet 

long. The long groups of fractures exhibit a "horsetail pattern" of 

gently curving planes diverging from a central line. Individual fillings 

rarely exceed 6 inches in length and are generally straight. The 

horsetail groups are largest and most abundant directly north of drill 

hole BB-3 and decrease in length and abundance northward and outward to the walls of the deposit. The relations of the fractures to the 

mineral boundaries of the intermediate and wall zones show the 

openings formed after these zones had solidified. The muscovitetourmaline fillings are not found in the hood or core. The fractures 

could have formed any time between the solidification of the outer 

zones and the final solidification of the core. These fissures are 

radially arranged and restricted to the northern quarter of the pegmatite, so it does not seem likely that they were caused by regional 

deformation. It may be presumed they are contraction or cooling 

cracks, as suggested by Cameron and others (1949, fig. 52, p. 71), 

which formed in the northern lobe of the body because it solidified 

first and lost heat faster than the main mass of the pegmatite. The 

zoning as shown in plate 12 indicates that the lobe was fully crystallized before the core in the main part of the pegmatite solidified. The

presence of tourmaline and muscovite in the core of the pegmatite 

indicates that material was available at the last stages of crystallization for filling the fractures,

EXPLORATION

The Big Boulder prospect was explored by 5 core holes totaling 

682 feet. The elevation of the collar, inclination of the hole, and 

depth drilled are indicated on the map (pi.. 11); the drill logs (tables

(appendix A, 7-9); the assay plans (figs. 18-20); and the cross sections 

(pi. 12). The drilling provided 32 sludge samples, 48 core samples

of pegmatite including the immediately adjacent country rock, and 7

core samples for a spectrographic study of the wall rock.

MINERAL DEPOSITS 

The Big Boulder prospect averages approximately 0.5 percent

beryl j the core is almost barren, but tKe wall zone contains an. amount

greater than the average. ' ','
BIG BOULDER PROSPECT 93

-X

Dr II hole BB-3

Elevation 8707 feet

Inclination 90°

Depth 96 feet

_r--r<^ '

""" *^T,\ /\7 \/

1^ H|^ N ' ~~ r V

VvX!\ M ' ^ V

i Sludge somples /

l~-i T T i - / \/ \.

£T T> K\ J U\

n~* i V/N. / \/

L* j./^-vW'' 1 1 ^ ^

\XKIK(V^ /-

^ ^\ v r V^-*^._ "

\ < \f sTj^ * '* ,.

\ ""V vv "* 1*-* -

\ "V-^^ f v

\ ^ * ?~--b^

Vy* " *<*

-~i_^_^

"

\ \ / ^ . |/ ^ /^v'i i\ jr ^~~'^^~\,

'" * 1 J ^v V ^ ^,3 Schist

/*f 1 J < / I ^v' ^v^

Core somples ^ >>V RESULTS OF SPECTROGRAPHIC

^ "'^ ^/7lVv-* V

Ct7 V^ T ^ V/</

A ^ sX-l 1V"V V Sample

X'/Vv^/)

J/^\-yy ' S7i

Vj .^j NJ / v C 7 9 

'/'/TV / O ' <5

</^YK S73

^.i^V S74 ? //14/

-1 % r s 75

'V' S 76

2r

= S77

S 78

S79

S 80

EXPLANATION

i ^- i Sample

 4

Perthite-quartz pegm atite

* +*,*. C 97 

^ » sr C 98 

 ^ P QQ

Cleavelandite-quartz pegmatite 

C100

K ? C101

-i ^ C 102

Plagioclase-perthite-quartz pegmatite C 103

1 n C104 

 ^^ w ,, C105

A C106

Plagioc ase-quartz pegmatite C 107

C108

C 109

C110

20 0

ANALYSIS

Sludge Samples 

BeO

Depth Content

(feet) (percent)

2.7- 10.. 0 0. 0030

10.0-15.0 0.026

15.0-24.0' 0.0040

24.0-32.0 0.0037

No sludge recovered

37.8 - 47.0 0.0032

47.0-54.8 0.0044

No sludge recovered

56.2 - 62.0 0.010

No sludge recovered

 67.2 - 68.0 0.0019

No sludge recovered

68.9 - 76.7 0.012

76.7 - 86.7 0.0065

Core Samples

Depth Content

(feet) (percent)

2.7-9.0 0.00085 

9.0 - 15.0 0.0068

15.0 - 24.0 0.0072 

24.0-32.0 0.0031

32.8 - 38.0 0.00085

38.0 - 42.7 0.0037

42,7 - 50.6 0.00085 

50.6 - 54.8 0.0012

54.8 - 59.2 0.0090

59.2 - 67.2 0.0053

67.2 - 77.0 0.0011

77.0-81.8 0.00090

81.8 - 82.4 0.0015

82.4 - 03. 2 0.0027

40 Feet i i

Drill hole location, plate 1 1 section B-B' Horizontal and vertical scale

FIGURE 18. Assay plan of diamond-drill hole BB-3, Big Boulder prospect, Larimer County, Colo.

The wall zone contains.0.75 percent beryl, each crystal less than 3 

inches in maximum length. The lower intermediate zone contains 

rock with 0.37 percent beryl, in grains less than 5 inches in size. The 

core and upper intermediate zone have about 0.06 and 0.07 percent 

beryl, respectively. Beryl is visible in the outcrop of the upper intermediate zone, but neither the drill core nor the outcrop of the coro 

reveal any beryl.
94 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Drill hole BB-4

Elevation 8690 feet

Inclination 45°

Depth 144 feet

RESULTS OF SPECTROGRAPHIC

ANALYSIS 

Sludge Samples

Sample

581

582

583 

S 84 

S85 

S 86

587

588

589 

890 

S ai 

8 92

Sample

c 79 

C80 

C 81 

C82 

e aa 

C84 

C 85 

C86 

C 87 

C 88

C89

C 90 

C 91 

C 92

C93

C94

Depth 

(feet)

56.0 - 

62.0 - 

66.5 - 

72. a - 

78.2 - 

88.2 - 

95.0 - 

101.5 - 

111.0 - 

121.0 - 

128.6 - 

132.5 -

62.0

66.5

72.8

78.2

88.2

95.0

101.5

111.0

121.0

128.6

132.5

138.5

Core Samples

Depth 

("feet)

56.0 - 

57.0 - 

58.0 - 

62.0 -

60. 1 - 

72.8 

78.2 - 

88.2 - 

95.0 - 

96. 0 -

57.0

58.0

62.0

68.1

72.8

. 78.2

88.2

95.0

96.0

102. 0

102.0- 111.0

111.0 - 116. 0

116.0 - 118. 2

118.2 - 120.7

120.7 - 124.6

124.6 - 130.8

13O. 8 - 133. O

133.0- 134.1

BeO

content 

(percent)

0.0033 

.0022 

'.013 

.026 

.048 

.044 

.015 

.0080 

.028 

.044 

.023 

.0064

 BeO

content 

(percent)

0.0027 

.0017 ' 

.0023 

.0014 

.013 

.31 

.039 

.0033. 

.0034 

.00075

.0021

.0033

.29

.0057

.015

.0034

EXPLANATION

lartz pegmatite

40 Feet

Horizontal and vertical scale

plate 11 section D-D*

FIGUBE 19,-Assay plan of diamond-drill hole BB-4, Big Boulder prospect.

County, Colo.
BIG BOULDER PROSPECT 95

Drill hole BB-5

Elevation 8671 feet

Inclination 45°

Depth 192 feet

RESULTS OF SPECTROGRAPHIC

ANALYSIS 

Sludge Samples

BeO

Depth content 

(feet) (percent)

Sample

S 93 

S 94 

S 95 

S 96 

S 97 

S 98 

S 99 

S 100 

S 101 

S 102

Sample

C 63 

C 64 

C 65 

C 66 

C 67 

C 68 

C 69 

C 70 

C 71 

C 72 

C 73 

C 74 

C 75 

C 76 

C 77 

C 78

110.5 - 114.7 

114.7 - 122.0 

122.0 - 128.8 

128.8 - 134.9 

134.9 - 143.4 

143.4 - 150.0 

150.0 - 156.6 

156.6 - 165.0 

165.0 - 173.0 

173.0 - 183.0

Core Samples

Depth

(feet)

107.7 - 109.0 

109.0 - 112.8 

112.8 - 122.0 

122.0 - 125.0 

125.0 - 128.8 

128.8 - 133.3 

133.3 - 136.8 

136.8 - 143.2 

143.2 - 150.0 

150.0 - 155.3 

155.3 - 161.7 

161.7 - 163.4 

163.4 - 167.0 

167.0 - 174.0 

174.0 - 178.1 

178.1 - 179.1

0.011

.064

.73

.10

.048

.022

.0084

.0067

.024

.0074

BeO

content 

(percent)

0.0019 

.0018 

.026

1.2

0.90 

.0046 

.0042 

.0016 

.0035 

.0020 

.0021 

.0024 

.048 

.0073 

.0042 

.0046

EXPLANATION

Quartz pegmatite

Cleovelandite-quartz pegmatite

Plagioclase-quartz pegmatite

10

Analyses of wall rock samples are given in table 2'

Horizontal and vertical scale

Drill hole location, plate 11 section B-B

FIQURE 20. Assay plan of diamond^drill hole BB-5, Big Boulder prospect, Larimer County, Colo.
96

Only one drill hole cut through the hood of the deposit, and it did 

not core any beryl crystals (figs. 21, 22). The analyses show 0.04 

percent beryl in the drill sample, but the production data show a 

grade of about 1.68 percent beryl.

No other economic mineral resources are present in the Big Boulder 

deposit. Muscovite is scarce and of scrap grade; perthite is intimately 

intergrown with other minerals, and tantalite-columbite is rare and 

fine grained.

-78.2

Broken core, complete 

reconstruction not possible

 78.4

 117.0

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

10 5 Inches 

I . . f . I_____|_____i_____i____|_____i

FIGURE 21. Plan of beryl grains exposed on diamond-drill core from hole BB-4, Big Boulder 

prospect, Larimer County, Colo.

BUCKHORN MICA MINE

TJb.6 BllCkllOrn Mica mine is reached from the town of Masonville 

by going west on the Buckhorn Creek road for 21 miles to a bridge

and turning south on an unimproved ranch road to the property

(fig. 2). The Buckhorn Mica mine is in the SW % sec. 29, T. 7 N., 

R. 71 W., sixth principal meridian.
BUCKHORN MICA MINE 97

Tapering beryl crystal with the ends 

showing on the cylindrical surface 

-120.7 0( thi core. The sides were exposed by accidental flaking and 

breaking of drill core

A*

Grain outlines traced directly from surface of Bi drill cor* 

Reference marks show depth. In t**t, from collar of drill note

FIOURE 22. Plan of beryl grains exposed on diamond-drill core from hole BB-5, Big Boulder prospect,

Larimer County, Colo.

The mica deposit was discovered in 1884 and was mined for a short 

period by the Buckhorn Mica Mining & Milling Co. The mine 

is now owned by Roy Hyatt, who relocated it in 1942 as the Emerald 

Gem claim. The records of past production are not available, but it 

is reported that at least 180 tons of ground mica, a few hundred 

pounds of sheet mica, and 2 or 3 tons of beryl have been produced 

during different periods of operation. In recent years beryl has been
98 PEGMATITES OF THE .CRYSTAL MOUNTAIN DISTRICT, COLORADO

handpicked from the dump, and the amount is estimated at about 

1 ton.

The mine has been described by Sterrett (1923, p. 59-60) and by 

Hanley, Heinrich, and Page (1950, p. 88-90). It was mapped by 

L. R. Page and J. B. Hanley on September 29 and 30, 1942, and was 

reexamined by the writer in September 1947. The map by Page and 

Hanley is reproduced with minor modifications by the writer as 

plate 13.

The workings consist of three shafts, a series of shallow, more or 

less interconnected opencuts, and five trenches. The eastern shaft is 

reported to have been 50 feet deep, and according to Sterrett (1923, 

p. 59) drifts were made from this shaft, but the underground workings 

are inaccessible. The observable parts of the caved and backfilled 

shafts are vertical, and undoubtedly they were sunk in the micarich part of the pegmatite. Most of the pegmatite is eroded to the 

level of the surrounding terrain, but the contacts are well exposed at 

the east end, and the interior zones can be examined in the larger 

workings.

GEOLOGY

The Buckhorn Mica pegmatite is a multiple intrusion consisting of 

the main body 530 feet long, a smaller member at the west end and a 

poorly exposed member south of the workings in the eastern part of 

the deposit. The main body and the south member are vertical and 

concordant in the quartz-mica schist of the area that strikes N. 70° E. 

The western member is partly concordant as a western extension 

of the main body and partly discordant, lying in a plane striking 

N. 50° W., dipping 45° NE. The main body has a maximum width 

of 32 feet and probably averages about 20 feet in width. The western 

member has an average width of about 10 feet and reaches a maximum of 16 feet. The full extent of the south member is not known,

but it is at least 100 feet long and has a maximum width of 9 feet, 

probably tapers to a knife edge at both ends, and extends to a depth of

120 feet or more. . ,

The outer part of the main body contains plagioclase, quartz, and

perthite, but the perthite is concentrated in the upper and outer parts

Of the deposit as at the Hyatt and Big Boulder pegmatites. The

pegmatite forming the outer part of the deposit can D6 divided HltO

two zones based on the abundance of perthite: the wall zone exposed

at the Surface IS plagioolase-pei-tlvite-qua.rtz pegmatite wKiok grades

inward and downward into Ae outer intermediate zone of plagioclasequartz pegmatite (pi. 13),. The inner intermediate zone is eieaveiandite-quartz pegmatite, and the core is cleavelandite-quartz-spodu- 

.mene(?) pegmatite.
BUCKHORN MICA MINE 99

The plagioclase-perthite-quartz pegmatite has a maximum width of 

15 feet and extends' to a maximum depth of 110 feet below the surface. 

The average grain size is less than 1 inch, but some grains are as much 

as 3 inches in long dimension. The texture and appearance of this 

zone are unusual: the bulk of the material is exceedingly fine grained 

and encloses coarser grained minerals in streaks and patches elongated 

roughly parallel to the walls. The matrix has an average grain size 

of less than 0.3 inch, but the minerals in the streaks are as much as

3 inches in length though the same minerals are common to both 

parts. The fine-grained matrix is somewhat darker than the common types of fine-grained pegmatite, and the color is irregular giving 

a blotchy appearance to the rock..

The 70-foot east-trending tongue at the east end of the main body 

is a zoned fracture filling. The pegmatite was fractured after most 

of the wall zone had solidified and pegmatite solutions escaped from 

the unconsolidated interior. The material crystallized to form 

zones continuous with the rest of the body. This interpretation has 

been proposed previously by Cameron and others (1949, p. 76). 

The fracture which breached the wall zone is a conspicuous surface 

coated with fine-grained green muscovite which separates the wall 

zone from the intermediate zone on the north side of the large opencut. The wall zone has an average width of about 7 feet in most of 

the main body but is only 0.2 to 1 foot wide in the fracture filling. 

The writer concurs with Cameron and his coauthors in explaining the 

origin of this body and adds the data regarding the thin perthitebearing wall zone to restrict more closely the relative chronology and 

eliminate the possibility suggested by Hanley, Heinrich, and Page 

(1950, p. 89) that the interior zones were formed by a separate injection of magma distinct from the pegmatite forming the wall zone.

The wall zone contains about 0.4 percent beryl according to the 

drilling data, but only a few crystals, all less than 1 inch in length, 

are visible in the outcrop. The major beryl content would seem to 

reside in finely disseminated grains. The proportions of minerals in 

the fine-grained wall zone are difficult to estimate but appear to be 

about 55 percent plagioclase, 30 percent perthite, and 15 percent 

quartz. Muscovite forms less than 1 percent of the wall zone. Other 

accessory minerals are tourmaline and garnet.

The outer intermediate zone of plagioclase-quartz pegmatite is as 

much as 10 feet wide but is absent in many places along the outcrop; 

it extends to the keel of the pegmatite, a maximum depth of 155 feet 

below the surface. The outer intermediate zone is composed of 65 

percent plagioclase and 35 percent quartz in grains ranging from 

0.01 to 12 inches in size. Most of the grains, however, range from 1 to

4 inches. Muscovite is abundant in local concentrations: the old
workings were sunk on one or more muscovite shoots, but existing 

exposures do not indicate that muscovite is an essential constituent 

of the remainder of the zone. Undoubtedly mica-rich pockets and 

streaks exist in concealed parts of the deposit, but mica probably 

constitutes less than 5 percent of the total rock. Many muscovite 

books from the dump are 1 to 8 inches across and as much as 3 inches 

thick, but all are ruled, wedged, and stained. Perthite in grains 2 to 

20 inches across is present in this zone. Tourmaline and purpurite 

(a hydrous phosphate of iron and manganese) and related phosphatic 

compounds are minor accessory minerals.

Beryl makes up about 0.5 percent of the outer intermediate zone 

and occurs in anhedral and euhedral crystals 0.1 to 5 inches in length. 

Many of the euhedral crystals enclose a large amount of quartz, 

plagioclase, and muscovite, and some are hardly more than hexagonal 

rims of beryl around a core of other minerals (see figs. 23-27).

The plagioclase of the outer intermediate zone is albite with an 

average composition of Ab94 . It becomes coarser and somewhat platy

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

5 Inches

.-p]an of beryl grains exposed on diamond-drill core from hole BH-1, Buckhorn Mica mine,

Larimer County, Colo.
101

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth. In feet, from collar of drill hole

FIGURE 24. Plan of beryl grains exposed on diamond-drill core from hole BH-2, Buckhorn Mica mine,

Larimer County, Oolo.

inward toward the inner intermediate zone, and grades gradually 

into cleavelandite. The boundary between the two intermediate 

zones is drawn more on average texture and decline of muscovite 

content than on differences in the essential minerals.

The inner intermediate zone of cleavelandite-quartz pegmatite is 

exposed for 490 feet on the surface and extends out in the eastern 

tongue of the main body; it is well exposed in the trench at the east 

end as well as in the main workings. It has a maximum width of 

16 feet and is interpreted to have a maximum depth of 110 feet below 

the outcrop. The inner intermediate zone contains about 55 percent 

cleavelandite, 43 percent quartz, and 2 percent accessory minerals. 

The cleavelandite has an average albite content of Ab95 to Ab96 , and 

forms plates as much as 0.3 inch wide and 12 inches long. Muscovite, 

beryl, columbite-tantalite, and perthite are accessory components. 

Muscovite forms thin books, 1 to 6 inches in diameter, and minute 

scales. Columbite-tantalite occurs in plates and blades, 0.01 to 0.6 

inch thick and 0.02 to 1 inch long.
-66.5

67.3

70-4

 71.0

74.0

--75,5

77.2

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

1

i i

FIGURE 25. Plan of beryl grains exposed on diamond-drill core from hole BH-3, Buckhorn 

Mica mine, Larimer County, Colo.

The beryl of the inner intermediate zone is white to pale greenish 

blue and occurs in grains and crystals 0.1 to 10 inches in length and

as much, as 6 incites in diameter. Assays of drill samples indicate

that the zone contains at least 0.8 percent beryl and locally as much

as 2 percent.

The core crops out in the workings for a distance of 85 feet. It

has a maximum width of 10 feet and an average width of about 4 feet,

tapers downward, and extends about 75 feet below the surface. The

core was intersected in drill hole BH 1 but not in the other holes. 

It is interpreted to have a maximum length of 180 feet in the direction

of plunge, that is, 22° S. 68° W. 

The core of the main body contains 50 percent cleavelandite, 45

percent quartz, 3 percent relict sPodumene(?), arid 2 percent accessory

minerals. Tie cleavelandite of the gttiwdmW Wig® ID COm])OSltiOH 

from Ab96 to Ab99 and forms plates as much as 20 inches long. Were
BUCKHORN MICA MINE 103

 19.7

21.7

 22.9

27.5

Broken out of core

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

5 Inches

TIGURE 26. Plan of beryl grains exposed on diamond-drill core from hole BH-4, Buckhorn 

Mica-mine, Larimer County, Colo.

it not for the relict spodumene(?), this zone would differ from the 

zone surrounding it only in being somewhat coarser grained. The 

spodumene is replaced by cleavelandite and. :by lithium-bearing 

pseudomorphous aggregates of fine-grained albite (Ab97 ) and sericite. 

The fine-grained aggregate preserves in many places the lamellar 

structure of spodumene, but cleavelandite growing inward into the 

.space occupied by the spodumene preserves only the outline of the 

lath. Some of the relict laths are 3 feet long and 2 to 4 inches thick. - 

Quartz in the core occurs in larger masses than in the inner intermediate zone, some of the clusters attaining a length of 5 feet. The 

quartz is cut by streaks and veinlets of fine-grained pale scaly mica. 

Beryl is an important accessory and in the workings is estimated to 

constitute 1 percent or more of the zone. The beryl crystals are 

white to pale blue, are commonly coated with very fine-grained muscpvite and albite, and enclose fewer grains .of other minerals
 15.7

 122.8

Grain outlines traced directly from surface of Bx drill core 

Reference marks show depth, in feet, from collar of drill hole

0 5 Inches

FIGURE 27. Plan of beryl grains exposed on diamond-drill core from hole BH-5, Buckhorn 

Mica mine, Larimer County, Colo.

beryl in the surrounding zones. Columbite-tantalite occurs in plates

which range from 0.01 to 0.23 inch thick, 0.2 to 3 inches long, and

0,1 to 2 inches wide. One block of rock from the core contains an

estimated 11 cubic inches of columbite-tantalite in three clusters of

tabular crystals.

The south member of the Buckhorn Mica pegmatite branches off

from the main body along the westward extension of the schist parting that is exposed on the south side of the main workings. It is

made up of plagioclase-perthite-quartz pegmatite like the wall zone 

of the main body with which it merges. Like tke Wall Z0u6 of the

main body, it is also fine-grained, tan to cream, and mottled. It

Contains plagioclase (55 percent), pertnite (3O percent), and quartz

(15 percent). It is known to extend westward to drill holeBH-2 

and may connect with the two small pegmatites farther west. Assays

indicate a beryl content of about 0.5 percent; but beryl is not readily
BUCKHORN MICA MINE 105

discernible in the outcrop, so it is probably very fine grained. Muscovite and tourmaline are minor accessory minerals. ;

The west member branches off from the main body at the end of a 

schist parting that is exposed in the westernmost pit. Much of the 

pegmatite in this part of the deposit is concealed, and some of the 

relations are obscure. The part of the member that trends northeast 

parallels the main body and is concordant in the schist. The northwest-trending part is in a plane striking N. 50° W., dipping 45° NE. 

According to the data obtained by drilling, the strike and dip of the 

discordant branch changes slightly to the northeast. (Compare 

cross sections in pi. 13.) The concordant part of the west member 

forms the connecting link between the main body and the discordant 

part. The northwestward extent of the discordant part may be 

greater than is shown in the sections (pi. 13), and its northeastward 

extent in the plane of dip may also be somewhat greater. The intersection of the northeast-dipping plane with the plane of the main 

body may modify the shape of the keel of the main body; the shape 

suggested in the sections (pi. 13) assumes that there has been no 

modification, but the dotted areas are not included in the calculations 

of reserves.

At the surface the west member consists of a perthite-bearing wall 

zone of plagioclase-quartz pegmatite and a core of cleavelanditequartz pegmatite. In drill holes BH-4 and BH-5 the wall zone does 

not contain perthite. In hole BH-3 there are relicts of schistose 

structure which are interpreted as pegmatitized material at the junction of the west member with the main body.

Drill holes BH 4 and BH-5 pass beneath the mam. body at such 

points that the possibility of a westward-plunging crest is eliminated 

and a narrow limit set on the probable extent of the main body.

The zonal boundaries shown in plate 29 differ in detail from those 

on the original map by Hanley, Heinrich, and Page (1950, pi. 11). 

The drilling reveals that the zones are more uniform and symmetrical 

than the weathered outcrop suggests, and the float has been reexamined and reinterpreted accordingly.

EXPLORATION

The Buckhorn Mica deposit was explored by five holes. The elevation of each collar, the inclination of each hole, and the depths 

drilled are indicated on the map (pi. 13), the drill logs (appendix A, 

10-14), the assay plans (figs. 28-32), and the cross sections (pi. 13). 

The drilling provided 15 sludge samples, 62 core samples of pegmatite and the immediately adjacent country rock, and 7 core samples 

for a spectrographic study of the wall rocks.
Drill hole BH-1

Elevation 8103 feet

Inclination 45°

Depth 110 feet

Cleavelandite-quartz-spodumene(?) pegmatite

Depth

(feet) 

75. 0 - 81. 0 

.81.0 - 86. 5 

86.5 - 95.0

Analyses of wall rock samples are given in table 2

FIGURE 28. Assay plan of diamond-drill hole BH-1, Buckhorn Mica mine, Larimer County, Colo.

MINERAL DEPOSITS

The most important beryl-bearing zones are the core and inner 

intermediate zone of the main body. The core is relatively small and

is estimated to have the same beryl content as the surrounding zone, 

SO that they are considered" as one deposit in the calculations of tonnage and grade. The drilling indicates that beryl-rich pockets are

present below the workings, but there is no evidence to assume that

they are present in the western part of the deposit. Assays of the drill

.samples are combined with assays of samples taken at the surface to 

arrive at estimates of beryl content west of the -workings. Samples of

the dumps from the main .workings confirm the high beryl content 

indicated by drilling beneath the workings. The beryl content 

calculated from the drilling data ranges from 0,01 to 1,97 percent and 

averages 0.86 percent; when combined with other sample data the
BUCKHORN MICA MINE 107

X

Drill hole BH-2 

Elevation 8109 feet .^

Inclination 45°. ^/^ °s\ 

Depth 147 <ee^^0<?x^Qve)

^SSSSf^

-f^^ \1 X^f "!* 'fcl'V ^ Overb^e^53^^

V* "^ ! ^1 ^ 'r IV ^1 

\ ?* '-y 7* 1 ji ~H* **'!'^ 1 4 '

\ US . : ^A iX"'1 **!* '-> ^

^v* n <!' <' ^1

<5^: ST^VC^ !

vi iy i' 1! ( . iiv vi

. RESULTS OF SPECTROGRAPHIC fXl*JvV/ ,K v\ '

ANALYSIS

Sludge Samples

Sample Depth

(feet)

S 5 86.2 - 95.0

S 6 95.0 -100.0

S 7 100.0 -110.0

S 8 110.0 -117.2

S 9 117.2 -127.0

UK!v>,/IV I ' Wl 1^ ^

Beo rCiJSLi^d

content I'lTU''!^ 'ix 1 V

(percent) '!> ^l*]^/' I<C<|

0.016 iVi (i-iy/ |T \l , ' oi ° r^v^i/ i-CrK .15 1"",} O| \

.077 u'Nf"' k-f" \ ' '

.067 //;» \ ^

. No sludge recovered ^^i.

S10 129. 2*-l'40. 0

'Core Samples

Sample Depth 

(feet)

C40 84.0 - 86.8

C41 86.8 - 90.5

C42 90.5 - 93.5

f*Ai no c no n

v^*±j yo. o ~ yy. u 

C44 99.0-101.5

C45 101.5 -103.9 

C46 103.9 -107. 3

C47 107.3 -112.7

C48 112.7 -114.4

C49 114.4-115.1 

C50 115.1 -120.0

C51 120.0-121.6

C52 121.6 -125.0

C53 125.0-130.3

C54 130.3 -132.0

C55 132.0 -133.2

.033 ^ i' A |

»"$<'

BeO ^ * )

content ^ / 

(percent) ^^ . EXPLANATION

0.041 =* "-*

.0078 * x *

. 036 Cleavelandite-quartz pegmatite

Tr ^A ^ ^

0012 A

' 25 Plagioclase-quartz pegmatite

.050 A ^

 015 H^. A

 °49 Plagioclase-perthite-quartz pegmatite

.043

 °41 20 0 40 Feet .045 I i i i I : I i

03g Horizontal and vertical scale

.0038

Drill hole location, plate 13 section C-C'

FIGURE 29. Assay plan of diamond-drill hole BH-2, Buckhorn Mica mine, Larimer County, Colo.

range is from 0.29 to 1.97 percent and the average is 1.06 percent 

beryl.

Other resources of the Buckhorn Mica mine are scrap mica and 

columbite-tantalite.

The columbite-tantalite content of the core and inner intermediate 

zone has not been tested analytically, but an examination of the 

workings and dumps suggests that the mineral is present in concentrations of the order of 0.00001 percent.

295165 55-
108 PEGMATITES OF THE-CRYSTAL MOUNTAIN DISTRICT, COLORADO

' Drill hole BH-3

Elevation 8104 feet

Inclination 45°

Depth 110 feet

' RESULTS OF SPECTROGRAPHIC

Sample

S 11

S 12

S 13

Sample

C21 

C22 

C23

C24

C25

C26 

C27 

C28 

C29

C30 

C31 

C32 

C33

C34 

C35 

C36 

C37 

C38 

C39

ANALYSIS 

Sludge Samples

Depth 

(feet)

. 65.0 - 75.0 

75.0 - 85.0 

. 85.0 - 91.0 

Core Samples

Depth 

(feet)

47.5 - 48.4. 

48.4 - 48.9 

48.9 - 50.4 

50.4-51.2 

51.2 - 51.8 

64. 0 - 65. 2 

65.2 - 67.7 

67.7 - 69.1 

69. 1 - 70. 1

70.1 -73.4 

73.4 - 74. 3 

74.3 - 74.7 

74.7 - 77.3 

77. 3-77.5 

77. 5-80.6

80.6 -82.6

82.6 - 85.6 

85.6 - 89.O 

89. 0 - 9O. O

EXPLANATION

BeO

content

(percent)

0.041

.048

.047

BeO

content 

(percent)

0.0014 

.0043 

.0011 

.058 

.036 

. 0028 

.043 

.066 

.0044

.062

. 30

.010

.054

.60 

.028

.038

.037

. 037

. 0021

Plagioclase-perthite-quartz pegmatite

Horizontal and vertical scale

Drill hole location, plate 13' section £ £'

so. Assay plan of diamond-drill hole BH-3, Buckhorn Mica mine, Larimer County, Colo.
SELECTED BIBLIOGRAPHY 109

Drill hole BH-4 

Elevation 8081 feet 

 Inclination 45°

Depth 110 feet

Drill hole location, plate 13 section F-F'

FIGURE 31. Assay plan of diamond-drill hole BH-4, Buckhorn Mica mine, Larimer County, Colo.

j

The dumps at the Buckhorn Mica mine have been partly reworked 

and the larger pieces of beryl removed, but they are estimated to 

contain a few tons of beryl too small to recover by hand sorting.

Perthite grains and crystals might be hand sorted as a byproduct, 

but the deposit could not be mined for potash feldspar alone.

The relict spodumene(?) contains less than 1 percent lithium and 

is not a marketable product.
110 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO
SELECTED BIBLIOGRAPHY 111 

SELECTED BIBLIOGRAPHY

Anderson, Olaf, 1931, Discussions of certain phases of the genesis of pegmatites: 

Norsk geol. tidsskr., Bind 12, p. 1-55.

Ball, S. H., 1908, General geology in Spun-, J. E., Garrey, G. H., and Ball, S. H., 

Economic geology of the Georgetown quadrangle: U. S. Geol. Survey Prof. 

Paper 63, p. 29-96.

Bannerman, H. M., 1943, Structural and economic features of some New Hampshire pegmatites: N- H. Min. Res. Survey, pt. 7, New Hampshire State 

Plan, and Devel. Comm. Concord, p. 1-22.

Bastin, E. S., 1911, Geology of the pegmatites and associated rocks of Maine:

. U. S. Geol. Survey Bull. 445, p. 10.

 1950, Interpretation of ore textures: Geol.. Soc. America Mem. 45, 101 p.

Bjorlykke, H., 1937, The granite pegmatites of southern Norway: Am. Mineralogist, v. 22, p. 241-255.

Boos, M. F., and Boos, C. M., 1934, Granites of the Front Range-rThe Longs 

Peak-St. Vrain batholith: Geol. Soc. America Bull., v. 45,. p. 303-332.

 1948, Pre-Cambrian structural geology of the Mount Olympus quadrangle

area, Larimer and Boulder Counties, Colo. [abs.]: Geol. Soc. America Bull.,

v. 59, p. 1398. 

Burbank, W. S., and Levering, T. S., 1933, Relation of stratigraphy, structure,

and igneous activity to ore deposition of Colorado and southern Wyoming, 

in Ore deposits.of the Western States (Lindgren volume): Am. Inst. Min.

Met. Eng., p. 272-311. 

Cameron, E. N., and others, 1945, Structural and economic characteristics of

New England mica deposits: Econ. Geology, v. 40, p. 369-393.

 1949, Internal structure of granitic pegmatites: Econ. Geology, Mon.

2, 115p. . . 

Fersman, A. Ye., 1931, Ueber die Geochemisch-Genetische Klassification der

Granit Pegmatite: Min. pet. Mitt., Band 41, p. 64-83.

 1940, Pegmatites, .Tom'1, Granite pegmatites: Akad. Nauk Izv., SSSR,

Moscow-Leningrad, 712,p. 

Fuller, M. B., 1924, General features of the pre-Cambrian structure along the

Big Thompson River in Colorado: Jour. Geology, v. 32, p. 49-63. 

Gevers, T. W., and Frommurze, H. R., 1929, Tin-bearing pegmatites of the

Erongo area, South-West Africa: Geol. Soc. South Africa Trans. and Proc.,

v. 32, p. 111-149. 

Grout, F. F., 1932, Petrography and petrology: 522. p., New York, McGraw-Hill

Book Co. ... 

Hanley, J. B., Heinrich, E. W., and Page, L. R., 1950, Pegmatite investigations

in Colorado, Wyoming, and Utah, 1942-1944: U. S. Geol. Survey Prof.

Paper 227, 125 p. .

Harker, Alfred, 1932, Metamorphism: 360 p., London, Methuen & Co. 

Hess, F. L., 1925, The natural history of pegmatites: Eng. and Min. Jour.-Press,

v. 120, p. 289-298. 

Ingerson, Earl, 1950, The water content of primitive granitic magma: Am.

Mineralogist, v. 35, p. 806-815.

Jahns, R. H., 1946, Mica deposits of the Petaca district, Rio Arriba County, 

: N. Mex.: N. Mex. Bur. Mines Bull. 25, p. 39-51, p. 289.

 1951, Geology, mining, and uses,of strategic pegmatites: Am. Inst. Min.

Met. Eng. Trans., v. 190, p. 45-59. 

Johnston, W. D., Jr., 1945, Beryl-tantalite pegmatites of northeastern Brazil:

Geol, Soc. America Bull., v. 56, p. 1015-1070.
112 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Kelley, V. C., and Branson, 0. T., 1947, Shallow high-temperature pegmatites, 

Grant County, N. Mex.: Econ. Geology, v. 42, p. 699-712.

Knopf, Adolph, 1913, Ore deposits of the Helena mining region, Montana: 

U. S. Geol. Survey Bull. 527, 143 p.

Krieger, Philip, 1932, Geology of the zinc-lead deposit at Pecos, N. Mex.: Econ. 

Geology, v. 27. p. 344-364, 450-470.

Labuntzov, A. N., 1939, Pegmatites of northern Karelia and their minerals in 

Pegmatites of the U. S. S. R.: Akad. Nauk, SSSR, Inst. Geol. Nauk, Tom 2, 

260 p.

Landes, K. K., 1925, Paragenesis of the granite pegmatites of central Maine: 

Am. Mineralogist, v. 10, p. 355-411.

 1928, Sequence of mineralization in the Keystone, South Dakota, pegmatites: Am. Mineralogist, v, 13, p. 519-530, 537-558.

1933, Origin and classification of pegmatites: Am. Mineralogist v. 18,

p. 33-56, 95-103. 

Levering, T. S., 1929, Geologic history of the Front Range, Colo.: Colo. Sci.

Soc. Proc., v. 12, p. 61-111. 

 1935, Geology and ore deposits of the Montezuma quadrangle, Colo.:

U. S. Geol. Survey Prof. Paper 178. 

Lovering, T. S., and Goddard, E. N., 1950, Geology and ore deposits of the Front

Range, Colo.: U. S. Geol. Survey Prof. Paper 223. 

Olson, J. C., 1942, Mica-bearing pegmatites of New Hampshire: U. S. Geol.

Survey Bull. 931-P, p. 336-403.

Page, L. R., 1950, Uranium in pegmatites: Econ. Geology, v. 45, p. 12-34. 

Page, L. R. and McAllister, J. R., 1944, Tungsten deposits, Isla de Pinos, Cuba,

in Geologic investigations in the American Republics, 1941-1943: U. S. Geol.

Survey Bull. 935, p. 177-246. 

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Quirke, T. T., and Kremers, H. E., 1943, Pegmatite crystallization: Am. Mineralogist, v. 28, p. 571-580. 

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v. 10, p. 269-279. 

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Smith, W. C., and Page, L. R., 1941, Tin-bearing pegmatites of the Tinton

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Spurr, V. E., Garrey, G. H., and Ball, S. H., 1908, Economic geology of the

Georgetown quadrangle: U. S. Geol. Survey Prof. Paper 63. 

Staatz, M. H., and Trites, A. F., 1954, Pegmatites of the Quartz Creek district,

Gunnison County, Colo.; U. S. Geol. Survey Bull, 265,

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740, 342 p.

Uspensky, N. M., 1943, On the genesis of granitic pegmatites: Am. Mineralogist,

v. 28, p. 437-447.

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U. S. Geol. Survey Bull. 360, p. 824.

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APPENDIX A

113
114 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

LOGS OF DRILL HOLES

1. Drill hole HY-1

Altitude of collar: 8,129.7 feet. 

Bearing: S. 24° E.

Feet

0-48.2

48.2-49.0

49.0-50.4 

50.4-55.0

55.0-56.8

56.8-57.4 

67.4-60.0

60.0-62.0

62.0-85.0

90-105.0

Inclination: 52°. 

Total length: 105 feet.

Beryl: area on core 

surface, in square

Description feet (see fig. 7) 

Biotite granite. Light-gray, medium-grained. Biotite flakes in some __....

parts alined in planes cutting ' at as much as 32°, indicating flow 

structure in granite; foliation dips 50° to 85° southward. Many quartz 

veins 0.01 to 0.2 foot wide, many Joints; six pyrite fracture fillings 

between 19 and 20 feet. 

Plagioclase-quartz-muscovite pegmatite. Fine-grained. Plagioclase .........

(50 percent), quartz (45 percent), muscovite (5 percent). 

Biotite granite.........-..-- - -- --..... ------ . . .....

Pegmatite, mainly plagioclase-quartz. Fine-grained.

50.4-53.7 Plagioclase (85 percent), quartz (12 percent), 0.0016 

muscovite (3 percent). Muscovite in clots 

and streaks. 

53.7-55.0 Plagioclase (75 percent), quartz (12 percent), .........

perthite (10 percent), muscovite (3 percent). 

Schist. Oranitized, contorted, with many small veins and blebs of .........

quartz. 

Granite. Foliation prominent, cutting at 40°_____________ .........

Plagioclase-perthite-quartz pegmatite. Fine-grained. Plagioclase .0015 

(50 percent), perthite (25 percent), quartz (20 percent), muscovite 

(15 percent). Plagioclase and quartz in graphic intergrowth. 

Schist. Granitized, and impregnated with pegmatite_______.. ..-.- 

62.0 Pegmatite contact; gradational, cuts at 35° to

40°. 

Pegmatite, mainly perthite-plagioclase-quartz. Fine-grained.

62.0-67.0 Plagioclase (45 percent), perthite (30 percent), 

quartz (22 percent), muscovite (3 percent). 

Cluster of tiny red-brown garnet grains at 

65.6 feet.

67.0-73.1 Perthite (45 percent), plagioclase (30 percent), 

quartz (22 percent), muscovite (3 percent).

73.1-76.8 Plagioclase (50 percent), perthite (25 percent), 

quartz (15 percent), muscovite (1.0percent).

76.8-85.0 Perthite (50 percent), plagioclase (25 percent), 

quartz (22 percent), muscovite (3 percent). 

Between 80.2 and 80.6 feet streaks of finegrained mica cut at 35°.

85.0 Pegmatite contact not preserved.

Biotite granite with apatite, and beryl-bearing pegmatite.

85.1 Fracture cuts at 57°_________

88.0 Small pegmatite dike cuts at 59°-.._____ 

OQ fl Garnet-bearing pegmatite dike 0.05 foot wide

O5.U

cuta at 33°. 

Granite and pegmatitic granite with gradational contacts.-..______

Altitude of collar: 8,163.7 feet.

Bearing: S. 24° E.

. Drill hole HY-2

.0003

.0017

.0056

.0004

Put

Inclination: 70°.

Total length: 176 teet.

Beryl: area on core

surface, in square

feet (see fig. 8)

0-9

9-104.9

Description

Overburden_--_--____________.__.------------------------- - "

BiOtite granite. Light-gray, medium-grained, with quartz veins less

than 0.2 foot wide and a few stringers of feldspar-rich pegmatite less

than o.i root -wide. Few joints, planar features range in cut' from

15° to 55°.

104.9 Contact between granite and pegmatite;

quartz-rich, gradational cut may average 

about 60°. 

See footnotes at end of table.
APPENDIX A 115

2 Drill hole HY-2 Continued

Beryl: area on core 

surface, in square

Feet Description feet (see fig. 8) 

104.9-165.6 Pegmatite, mainly plagioclase-quartz.. Fine-grained.

104.9-108.5 Plagioclase (60 percent), quartz (29 percent), 0.0057 

muscovite (10 percent), tourmaline (1 percent). Muscovite books as much as 0.2 foot 

in diameter. 

108.5-112.3 Plagioclase (65 percent), quartz (32 percent), .........

muscovite (3 percent), tourmaline (X).a 

Graphically intergrown plagioclase and 

quartz in irregular patches. Tourmaline 

occurs in muscovite-rich clots. 

112.3-113.3 Quartz (80 percent), plagioclase (12 percent), . ....

muscovite (8 percent). 

113.3-114.9 Quartz (99percent), plagioclase (1 percent)_. .. ....

114.9-116.2 Quartz (60 percent), cleavelandite (30 percent), .0136

muscovite (10 percent).

116.2-165.6 Plagioclase (60 percent), quartz (40 percent). .0134 

Muscovite (X) and tourmaline (X) in streaks 

and patches. Graphic intergrowths of plagioclase and quartz common. Clot of muscovite and quartz in irregular intergrowth at 

124 feet. Clusters of garnet grains common 

from 164 to 165.6 feet.

165.6 Pegmatite contact cuts at 32°.

165.6-166.8 Granite; with quartz veins and pegmatite patches...__._ _.. . _. 

166.8-176 Biotite granite. Foliation cuts at 50° to 65°__....._..._...__. . _.

3 Drill hole HY-S

Altitude of collar: 8,179.5 feet. Inclination: 50°.

Bearing: S. 25° E, Total length: 217 feet.

Beryl: area on core 

surface, in square

Feet Description feet (see fig. 8) 

0-4 Overburden... _.._...__..__..__.... _..._ ..... _......

4-96.8 Biotite granite. Light-gray, medium-grained_____________ .........

17-18 Biotite flakes alined in two sets of planes.

One is parallel to core and the other cuts * at 

22°; the strike of one set is at 15° to the strike 

of the other.

27 Cluster of pyrite grains. . 

30 Band of quartz and pyrite 0.05 foot wide cuts at

15°.

38 ' Biotite flakes alined in two sets of planes, one 

parallel to core and one cutting at 35°; planes 

strike at 35° to each other.

47 Quartz pegmatite 1.5 feet wide, cuts at 22°. 

67 Biotite flakes alined at cut of 40° and at cut of 

' " 90°; planes strike at 40° to each other.

80 . Streak of dark minerals 0.01 foot wide, cuts at 36°.

85 Biotite flakes parallel the core.

94 Biotite flakes alined hi two planes parallel to

' the core, striking at 20° to each other. 

96.8 Pegmatite contact cuts at 48°. 

96.8-100.8 " Perthite-plagioclase pegmatite. Medium-grained__________.. __....

Perthite (60 percent), plagioclase (38 percent), quartz (2 percent). 

100.8 Biotite-granite contact cuts at 80°. 

100.8-132.5 Biotite granite..._______..____________________ .........

110 Biotite flakes parallel the core.

120 Two seams of quartz and pyrite, 0.02 foot'wide,

cut at 62°. 

132.5 Pegmatite contact is irregular; minimum cut is

65°, maximum is 80°. 

See footnotes at end of table.
116 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

3. Drill hole HY-3 Continued

Feet

132.5-144.6

144.6-148.2 

148.2-162.5

162.5-178.7

178.7-189.0

189.0-200.6

209.6-217

Beryl: area on core

surface, in square

Description feet (see fig. 9)

Pegmatite, mainly plagioclase-quartz-perthite.

132.5-139.4 Plagioclase (60 percent), quartz (25 percent), 0.0004 

perthite (10 percent), muscovite (5 percent). 

Fine-grained; graphic textures common. 

Garnet grains as much as 0.005 foot in diameter and tourmaline grains as much as 0.03 

foot long from 132,5 to 133.5 feet.

139.4-144.6 Quartz (90 percent), plagioclase (7 percent), ._..... 

muscovite (3 percent). Plagioclase forms 

thin interstitial stringers. Tourmaline common between 139.4 and 140.5 feet.

Perthite-quartz pegmatite. Quartz with dark-green apatite____ .........

Pegmatite, mainly quartz-plagioclase-muscovite. Medium-grained.

148.2-151.2 Quartz (70 percent), platy plagioclase (20 per- .0299 

cent), muscovite (10 percent).

151.2-153.0 Quartz (85 percent), platy plagioclase (15 per- .........

cent), muscovite (X).' Muscovite in 

wedged books as much as 0.3 foot long.

153.0-164.9 Quartz (65 percent), platy plagioclase (20 per- .1836 

cent), muscovite (15 percent). Small areas 

of dark-gray quartz.

154.9-157.9 Plagioclase (65 percent), quartz (35 percent) . 0011 

muscovite (X), tourmaline (X). Graphic 

intergrowth of plagioclase and quartz.

157.9-159.2 Quartz (55 percent), plagioclase (45 percent). .0037 

Coarser grained than units above and below.

159.2-162.5 Plagioclase (50 percent) and quartz (50 per- .0077 

cent) in graphic intergrowth.

Pegmatite, mainly perthite. Coarse-grained____________ .........

162.5-164.4 Plagioclase (55 percent), quartz (38 percent), 

muscovite (5 percent), tourmaline (2 percent). Fine, irregular grain and involute 

banding; white feldspar around pink feldspar, muscovite-rlch selvage on feldspar.

164.4-178.7 Perthite.

Perthite-plagioclase-quartz pegmatite. Medium-grained.

178.7-183.6 Perthite (45 percent), plagioclase (30 percent), 

quartz (25 percent), muscovite (4 percent), 

tourmaline (1 percent).

183.6-189.0 Perthite (60 percent), plagioclase (20 percent), 

quartz (15 percent), muscovite (4 percent),

tourmaline (1 percent). Clusters of tiny

garnet crystals at 187.0 feet. 

Plagioclase-quartz pegmatite.

189.0-199,3 Plagioclase (70 percent) ana quartz (30 percent) in graphic Intergrowth. 

199.3-201.0 Plagtodase (97percent), quartz (3percent)....

201.0-202.6 Plagioclase (60 percent) and quartz (40 percent) in graphic intergrowth.

202.6-204.4 Pegmatltized granite (fine-grained quartz and

204.4-207,9

207.9-2O9.6

mica) with plagioclase-Quartz pegmatite in>

pregnations and stringers. Contains 1 percent tourmaline. A. roll In the footwall.

Plagioclase (96 percent), quartz (4 percent).

A. very fine-grained aggregate of quartz and 

muscovite veins the mass, giving a faint 

marblelike shadowing.

Plagioclase (85 percent), quartz (15 percent)..

Biotite granite. 

209.6-212

212-217 

See footnotes at end of table.

.0162

.0037

,0031

.0005

Biotite flakes alined almost parallel to core 

In two planes striking at 40° to each other. 

Foliation parallel to core.
APPENDIX A 117

Altitude of collar: 8,171.5 feet. 

Bearing: 8. 25° E.

4 Drill hole HY-4

Feet

0-10 

10-170

170.0-213.4

Overburden. 

Biotite granite.

19

19-21

21.5

21-170

58.8 

61

62-63 

71.8

78.7

88.2-89.8

91.2

92.8

97

103-110

112.2

127-130

140

140.5-143

143-149 

149 

163 

170.0

Description

Inclination: 50°. 

Total length: 242 feet.

Beryl: area on core 

surface, in square 

feet (see fig. 10)

Light-gray, medium-grained _ ............

Biotite flakes parallel to core. 

Closely spaced fractures in granite. 

Pegmatite 0.3 foot wide cuts » at 46°. Quartz

(95 percent), perthite (4 percent), plagloclase

(1 percent), tourmaline (X).' 

Fractures, and quartz veins less than 0.1 foot

in width occur at intervals of 0.1 to 1 foot. 

Pyrite fracture filling 0.01 foot wide cuts at 90°. 

Chlorite and pyrite fracture filling cuts at 65°. 

Feldspar-rich pegmatite. Fine-grained. 

Feldspar-rich pegmatite 0.1 foot wide with

pyrite and tourmaline; cuts at 69°. 

Chlorite and pyrite fracture filling 0.01 foot

wide; cuts at 58°. 

Pegmatite 1 foot wide cuts at 72°. Quartz

(98 percent), feldspar (2 percent). 

Pegmatite 0.15 foot wide cuts at 77°. Feldspar

(95 percent), quartz (5 percent), muscovite

(X), tourmaline (X). 

Pegmatite 0.2 foot wide cuts at 50°. Quartz

(80 percent), feldspar (20 percent), apatite (X). 

Biotite flakes alined parallel to core and at 20° to

core; planes strike at 40° to each other. 

Granite much fractured; pegmatitic parts.. 

Biotite alinement cuts at 17°. 

Fractures parallel the core. 

Biotite alinement cuts at 24° to 34°. 

Pegmatite. Quartz, feldspar, apatite. Upper

contact cuts at 60°, lower contact at 48°. 

Massive granite. 

Biotite alinement cuts at 28°. 

Biotite alinement cuts at 18°. 

Pegmatite contact cuts at 46.°

Pegmatite, mainly plagioclase-quartz.

170.0-171.6

171.6-173.6

173.6-176.0

176.0-178.2

178.2-180.6

180.6-190.2

Plagioclase (90 percent), quartz (9 percent), ........

muscovite (1 percent). Tourmaline-rich 

band 0.1 foot wide at 170.3 feet.

Plagioclase (70 percent), quartz (22 percent), 0.0021 

muscovite (8 percent). Muscovite occurs in 

quartz-rich streaks between 171.6 and 172.3 

and between 173.0.-and; 173.2 feet. Tourmaline-rich band cuts at 65° to 70°.

Plagioclase (70 percent), quartz (30 percent), .0012 

muscovite (X). Tourmaline-rich band 0.05 

foot wide cuts at 35°.

Plagioclase (70 percent), quartz (30 percent), . 

muscovite (X). White plagioclase is somewhat platy and forms graphic intergrowth 

with quartz.

Platy plagioclase (97 percent), quartz (2 per- .0024 

cent), muscovite (1 percent).

Plagioclase (70 percent), quartz (30 percent), .0033 

muscovite (X), tourmaline (X). Plagioclase, somewhat platy, In graphic intergrowth with quartz. Cluster of garnet 

crystals 0.001 foot in diameter at 181.9 feet. 

Tourmaline grains as much as 0.06 foot long 

make up 1 percent of the rock from 185.7 

to 186.7 feet.

See footnotes at end of table.
118 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

4- Drill hole HT-4 Continued

Beryl: area on core 

surf ace in square

Feet Description feet (see fig. 10) 

170. 0-213. 4 Pegmatite, mainly plagioclase-quartz. Continued

190.2-194.3 Plagioclase (70 percent), quartz (30 percent), 0.0010

muscovite (X), 2 tourmaline (X). Plagioclase of blocky habit rather than platy.

Three garnet crystals dimensions 0.02 by

0.02 feet, 0.01 by 0.03 feet, and 0.03 by 0.03

feet at 191.0 feet. Cluster of tiny garnet

crystals at 192.0 feet. At 193.0 feet a garnetrich band cuts ' at 50°. 

194.3-201.0 Plagioclase (60 percent), quartz (30 percent), .0016

muscovite (10 percent). Plagioclase platy.

Muscovite in masses as much as 0.2 foot long. 

201.0-204.3 Quartz (98 percent), plagioclase (2 percent), __ . ....

muscovite (X). 

204.3-208.8 Plagioclase (80 percent), quartz (20 percent), .0923

muscovite (X), tourmaline (X). Plagioclase

granular to blocky. 

208.8-212.0 Plagioclase (80 percent), quartz (20 percent), ..... ....

in part graphic. Garnet band cuts at 90°

at 212.0 feet. 

212.0-213.4 Plagioclase (70 percent), and quartz (30 per- .0020

cent). Scattered clusters of tiny garnet

crystals. At 213 feet minute anhedral to

euhedral pyrite grains.

213. 4 Granite contact cuts at 42°. 

213. 4-234. 3 Granite with small pegmatite bodies.

213. 4-217. 5 Granite with foliation parallel to core ____ .........

217. 5-218. 7 Pegmatitized granite.

218.7-220.9 Plagioclase-quartz-perthite pegmatite. Upper ..... ....

contact cuts at 75°, lower cuts at 50°. 

221.8-222.2 Plagioclase-quartz pegmatite cuts at 70°..... .....-.-.

224.4-227.8 Perthite-plagioclase-quartz pegmatite. Perth- .0003

ite (60 percent), plagioclase (30 percent),

quartz (9 percent), muscovite (1 percent).

Muscovite boots as much as 0.1 foot across.

Upper contact cuts at 25°, lower at 80°.

228. 2-234. 3 Plagioclase-perthite-quarz pegmatite. Plagio- . 0022 

. clase (55 percent), perthite (30 percent),

quartz (15 percent), muscovite (X). At .

230.0 feet rock in a 0.6 foot interval contains

 ' very fine-grained green mica in greenishtinted platy plagioclase. Upper contact

ovits at 8O°, and lower at 64°.

234.3-242 Biotite granite.- _____________________ . ________ _____

Altitude of collar: 8,138.7 feet. Inclination: 60°. 

Bearing: S. 25° E; ' Total length: 101 feet

. Beryl: area on core

surface, in square

Feet ' Description feet (set fig. 11) 

0-13 Deeply weathered and. partly eroded; core recovery low; contacts . ....

approximate. 

g_9 PlagiOClase-perthite-quartz pegmatite. Plagioclase (45 percent), perthite (35 percent), 

quartz (15 percent), muscovite (5 percent). 

9-11 Quartz.

11-13 Plagioclase-quartz-muscovite pegmatite. 

Fine-grained. Plagioclase (60 percent), 

quartz (35 percent), muscovite (5 percent). 

Patches of graphic material. 

See footnotes at end of table.
APPENDIX A 119

5. Drill hole HY-5 Continued

<Feet

.13-55.6

35.6-62.4

'62.4-83.6

-83.6-101

Description

Beryl: area on core 

surface in square 

feet (see fig. 11)

Pegmatite

13-16

16.0-16.4

16.4-27.5

27.5-33.0

33.0-39.0

Quartz.

Quartz (98 percent), plagioclase (2 percent). 

Coarse-grained, pinkish-white perthite. 

Pink perthite.

Medium-grained quartz (90 percent), with interstitial cleavelandite (8 percent) and muscoyite (2-percent).

39.0-45.0 Platy plagioclase (75 percent), quartz (23 percent) , muscovite (2 percent). Fine-grained. 

Band of tourmaline 0.2 foot wide at 45.0 feet.

45.0-49.0 Graphic, fine-grained intergrowth of plagioclase (75 percent) and quartz (25 percent).

49.0-50.0 Plagioclase (60 percent), quartz (30 percent), 

musco vite (20 percent).

50.0-55.6 Perthite (50 percent), plagioclase (25 percent), 

quartz (15 percent), muscovlte (9 percent), 

tourmaline (1 percent).

Pegmatite, mainly plagioclase-quartz-muscovite.__ .

65.6-60.0 Platy plagioclase (80 percent), quartz (16 percent), perthite (2 percent), musco vite (2 

percent).

60.0-61.2 Fine-grained aggregate of plagioclase, quarti, 

and muscovite.

61.2-62.4 Dense granular albite.

Plagioclase-quartz pegmatite.___________... ....

62.4-70.7 Plagioclase (90 percent), quartz (6 percent), 

muscovite (4 percent), tourmaline (X).J

70.7-72.5 Fine-grained mica and tourmaline laced 

through plagioclase (80 percent), quartz (17 

.percent),.muscovite,(3 peccent).

72.5-78.2 Plagioclase (80 percent), quartz (17 percent), 

muscovite (3 percent).

78.2-83.6 Plagioclase (80 percent), quartz (19 percent), 

muscovite (1 percent).

83.6 Pegmatite contact cuts ' at 70°.

Biotite granite with'quartz veins and small pegmatites. .....

83.6-87.0 Quartz veins less than 0.05 foot wide, cut at 

10°, 40°, and 50°.

93.0 Irregular quartz vein 0.5 foot wide, rich In 

pyrite.

96.0 Pegmatite 0.1 foot wide. Plagioclase (70 percent), quartz (30 percent). Cuts at 65°.

97.0 Pegmatite 0.05 foot wide, cuts at 28° in opposite 

direction to pegmatite at 96.0 feet. Plagioclase (85 percent),'quartz (16 percent).

6. Drill hole HY-6

0.0047

Altitude of collar: 8,145.7 feet. 

Bearing: S. 24° E.

Feet Description 

Overburden..___________________________......

Quartz-mica schist. Dark-gray, fine-grained, fine banding. Cuts' 

. at 70° to 90°.

Granite with irregular disconformable contact-____._ _.. 

Quartz... ._.................__...._......... ... ....

Quartz-mica schist. Foliation cuts at 80° to 90°________.......

Tourmalinized schist_..._________...__..._____. 

Plagioclase-perthite-quartz pegmatite. Fine-grained. Plagioclase (40 

percent), perthite (30 percent), quartz (26 percent), muscovite (6 

percent). Upper contact irregular, cut averaging about 70°. 

See footnotes at end of table.

Inclination: 45°. 

Total length: 78 feet

Beryl: area on core

surface, in squari

feet (see fig. IS)

'0-6 

.5-16

16-16.6

16.5-18.9

18.9-29.9

-.29.9-30.0

.30.0-34.0 0.0009
120 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

6. Drill hole HY-6 Continued

34.0-34.4 

34.4-39.2

39.2-40.5 

40.6-54.0

Feet Description

Schist, tourmalinlzed and silicifled.....__...__________ _...

Plagioclase-quartz pegmatite .._________..

34.4-35.5 Plagioclase (70 percent), quartz (25 percent), 

muscovite (5 percent).

35.5^39.2 Plagioclase (75 percent), quartz (22 percent), 

muscovite (3 percent). Fine-grained graphic 

intergrowth of plagioclase and quartz.

Tourmaline schist______._______________....

Pegmatite, mainly plagioclase-quartz. .............................

40.5-43.5

Beryl: area on core 

surface in square 

feet (see fig. 12)

0.0018

54.0-56.3 

56.3-78

Plagioclase (68 percent), quartz (22 percent), 

perthite (7 percent), muscovite (3 percent). 

Irregular, flne-grained.

43.5-48.2 Graphic intergrowth of plagioclase (80 percent) 

and quartz (18 percent); muscovite (2 percent).

48.2-50.0 Plagioclase (70 percent), quartz (20 percent), 

perthite (9 percent), muscovite (1 percent). 

Plagioclase and quartz in graphic interfro wth.

50.0-50.4 Perthite with brown dendritic discoloration..

50.4-51.8 Plagioclase (80 percent), quartz (19 percent), 

garnet (1 percent). Graphic intergrowth of 

plagioclase and quartz.

51.8-54.0 Plagioclase (80 percent), quartz (20 percent). 

Graphic.

54.0 Contact of pegmatite with granite cuts at 77°.

Biotite granite. Coarse-grained; foliation cuts' at 15°______..

Biotite granite with many quartz veins less than 0.06 foot wide, and 

feldspar-rich pegmatites 0.2 to 0.3 foot wide at 73, 76.3, and 77 feet. 

Light-gray aplite dikes at 61 and 70 feet, less than 0.2 foot wide.

.0009

.0002

.0036

.0028

7. Drill hole BB-S

Altitude of collar: 8,707 feet. 

Bearing: Vertical.

Inclination: Vertical. 

Total length: 96 feet.

Beryl: area on core

surface, in square

Feet Description feet

0-2.7 Overburden..__.... .. .

2.7-59.2 Pegmatite, mainly perthite-quartz... ................. .....

2.7-9.0 Coarse-grained perthite with flne-grained interstitial Quartz.

9.0-15.0 Dark-gray quartz in pebbly breccialike aggregate with perthite fillings; hematite stains;

muscovite (X).8 

15.0-18.0 Quartz in progressively larger fragments with

wider perthite fillings, that is. gradation to

unit below.

18.0-38.0 Coarse-grained perthite with a dozen wedgeshaped blades of light-colored quartz 0.02 

foot wide.

38.0-42.7 Coarse-grained graphic granite.

42.7-47.0 Coarse-grained pink perthite; 

47.0 48.0 Dark-gray quartz.

48.0-59.2 Coarse-grained perthite, a little very fine

grained quartz and museovite. Nodule of

iron-manganese phosphate 0.1 foot in diameter at 51.0 feet.

BO.2-67.2 Cleavelandite-cuiartz pegmatite. Medium-grained. White to cream

cleavelandite (65 percent), quartz (30 percent), very fine grained 

muscovite (3 percent), salmon-colored perthite (2 percent). 

See footnotes at end of table.
APPENDIX A 121

7. Drill hole BB-S Continued

Beryl: area on core 

surface, in square

. Feet Description feet 

67.2-77.0 Plagioclase-perthite-quartz pegmatite. Plagioclase (55 percent), ......

perthite (25 percent), quartz (20 percent), muscovite (X). 

77.0 Band 0.05 foot wide of tiny tourmaline needles;

cuts' at 70°. 

77.0-82.4 Plagioclase-quartz pegmatite. Fine-grained. Plagioclase (60percent), .........

quartz (35 percent), perthite (3 percent), muscovite (2 percent). 

82.4 Pegmatite contact cuts at 37°.

82.4-96.0 Quartz-mica'schist. Medium-gray, medium-grained. Cuts at 40°. 

95-96 Schist contorted; vague foliation cuts at 32°.

8. Drill hole BB-4

Altitude of collar: 8,690 feet. Inclination: 45°. 

Bearing: S. 77° E. Total length: 144 feet

Beryl: area on core 

surface in square 

Feet Description feet (see fig. 21)

0-3 Overburden........_................................___..___ .___

3-S7 Quartz-mica schist.......... ............ ....._...._... __.....

3-20 Quartz (70 percent), mica (20percent), feldspar 

(10 percent). Coarse-grained. Very lightgray quartzose bands alternate with darkgray to black micaceous bands. Foliation 

cuts' at 35°. Schist gradually becomes 

lighter and finer grained downward.

20-56 . Quartz (75 percent), mica (15 percent), feldspar (10 percent). Medium-grained, lightgray, fine banding. Foliation cuts at 25° to 

40°.

56-57 Dense quartz-mica rock with a few tiny garnet 

crystals and a feldspar-rich pegmatite 0.05 

foot wide sutting at 22°.

57 Pegmatite contact, embayed and Irregular;

average cut about 55°. 

57-68.1 Plagioclase-quartz pegmatite _ ... ..._...

57.0-57.4 Clot, with graphic structure, of plagioclase 

(50 percent), perthite '(25 percent), quartz 

(25 percent).

57.4-68.1. Plagioclase (85 percent), quartz (12 percent),

perthite (3 percent), muscovite (X).' 

Plagioclase and quartz in graphic intergrowth. 

68.1-96.0 Cleavelandite-quartz pegmatite. Medium-grained.

68.1-74.5 Cleavelandite (50 percent), quartz (50 per- .........

cent). '

74.5-96.0 Cleavelandite (80 percent), quartz (20 per- 0.0101

cent). 

96.0-116.0 Pegmatite, .mainly quartz. Coarse-grained.

96.0-102.0 Quartz (90 percent), Cleavelandite (9 percent), 

tourmaline (1 percent).

102.0-106.0 Quartz (96 percent); some massive, grading 

 into breccialike with interstices ifllled with 

flne-grained white albite and fine-grained 

muscovite. A few crystals of garnet and 

tourmaline.

106.0-111.0 Quartz with small blades of white and pink 

(iron-stained?) Cleavelandite, sugary flnegrained albite, muscovite in books as much 

as 0.1 foot in diameter, and exceedingly finegrained, pale-green mica.

111.0-116.0 Quartz (60 percent), Cleavelandite (25 percent), 

muscovite (10 percent), perthite and microcline (4 percent), garnet (1 percent). 

See footnotes at end of table. 
122 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO 

8. Drill hole BB-4 Continued

<Feet

Beryl: area on core

surface in square

feet (seeflg. £1)

116.0-124.6

124.6-130.8

130.8-144

Description 

Cleavelandite-quartz pegmatite. Medium-grained. 

116.0-121.7 Cleavelandite (60 percent), quartz (40 percent).

121.7-124.6 . Cleavelandite and quartz in graphic intergrowth.

Plagioclase-quartz pegmatite. Fine-grained. Plagioclase (90 percent), quartz (10 percent), muscovite (X). 

130.8 Schist contact cuts at 70°. 

Quartz-mica schist, some pegmatized.. ___..____._____ 

Pegmatized schist. Foliage cuts at 68° to 

73°.

Pegmatite. Fine-grained. Feldspar (85 percent), quartz (15 percent). 

Medium-gray schist. Foliation cuts at 55°. 

Light-gray schist. Dense; faint banding.

0.0708

130.8-131.4 

131.4-133.0

133.0-134.1 

134.1-144

9. Drill hole BB-5

Altitude of collar: 8,671 feet. 

Bearing: S. 77° E.

Inclination: 45°. 

Total length: 192 feet.

Fed

0-6.5 

6.5-109.0

109.0-128.8

Beryl: area on core 

surface, in square

Description feet (see fig. £8) 

Overburden__ _____.________.. _______ .........

Quartz-mica schist. Light-gray, medium-grained. Quartz (70 percent), biotite (15 percent), muscovite (10 percent), feldspar (5 percent). Foliation cuts ' at 35° to 55°; foliation contorted in narrow 

zones at 12.0, 25.4, and 65 feet. Quartz stringers and blebs at 12.0, 

54.0, 65.0, and 93 feet.

98-101 Foliation cuts at 60°.

109.0 Pegmatite contact, embayed and irregular; 

cut ranges from 40° to 75°.

Plagioclase-quartz pegmatite.

109.0-112.8 Plagioclase (50 percent), quartz (50 percent), 0.2619 

pale-green muscovite (X),» in minute flakes 

and in books as much as 0.06 foot in diameter.

112.8-113.0 Muscovite books__...____________ .........

113.0-121.0 Much of quartz and plagioclase is in graphic .0101 

intergrowth. Irregular 1-inch masses of 

microcline between 113 and 114.5 feet.

122.0-125.0 Large incomplete crystals of beryl ... .1245

123.0 125.0 Tourmaline grains and crystals as much as ____.. 

0.2 foot in size.

125-128.8 Plagioclase becomes progressively more platy. . 1273

109.9-149.0 Peematite. mainly cleavelandite-quartz__._____ ...... .........

128.8-133.3 Cleavelandlte (80 percent;, quartz. <io percent?.

133.3-136.8 Cleavelandite (95 percent), quartz (5 percent); 

cut by veinlets of very fine-grained albite,

euneOral garnet, <it»rk pnospnatlo material.

Stained by manganese oxides.

136.8-142.5 Cleavelandite with manganese oxide dendrites. 

142.5-143.2 Relict spodumene (?) (90 percent), quartz (6

percent), Cleavelandite (4 percent). 

143.2-155.3 Quartz pegmatite. Coarse-grained____ ...

149.0 Stringer of very fine-grained, albite with tiny

garnet crystal cuts quartz almost parallel to

axis of drill core. 

150.7 Mass or relict spodumene (.T) O.I foot in diameter.

151.7 and 153.0 Stringer of albite and garnet as at 149 feet;

patches of very fine-grained green mica. 

155.3-161.7 Cleavelandite-quartz pegmatite. Cleavelandite (50 percent), quartz .........

(40 percent), albite with garnet (10 percent) in patches. 

See footnotes at end of table.
APPENDIX A 123

9. Drill hole BB-5 Continued

Feet

Beryl: area on core 

surface in square 

feet (see fig. 22)

161.7-178.1

178.1-179.1 

179.1-192.0

Description

Plagioclase-quartz pegmatite. Fine-grained. 

161.7-163.4 Plagioclase (45 percent), quartz (40 percent), __.__

muscovite (15 percent).

163.4-178.1 Plagioclase (50 percent), quartz (50 percent), 0.0007 

muscovite (X). Graphic intergrowths common. 

Quartz-mica rock, without foliation. Fine-grained, medium-gray. .........

Joints cut at 50°, crude layering cuts at 70°. 

Quartz-mica schist. Finergrained, medium-gray, thinly banded. .........

Quartz (90 percent), mica (10 percent). 

187-192 Slightly contorted schist.

10 Drill hole BH-1

Altitude of collar: 8,103 feet. 

Bearing: S. 21° W.

Feet

0-10 

10-73.5

78.3-87.8

$7.8-92.2

 92.93-93.2

 93.2-97.9

 97.9-110.0

Description

0 verburden... _... 

Quartz-mica schist. 

10.-21.8

Inclination: 45°. 

Total length: 110 feet.

Beryl: area on core 

surface, in square 

feet (see fig. 23)

Medium-gray, medium-grained_ ___. __ 

Light bands contain as much as 15 percent 

feldspar. At 18 feet quartz pegmatite 0.9 

foot wide cuts ' at 30°; foliation cuts at 65° ' 

above quartz pegmatite but parallels it 

below. At 21 feet schist is contorted; quartz 

lenses and pods are common.

24.5-30 Foliation cuts at 10° to 25°. At 25.5 feet 

quartz pegmatite 0.3 foot wide, cuts at 25°.

30.-38.5 Foliation and bedding form arc with secondary foliation cutting at 10°. Possible axis of 

isoclinal fold at 38 feet.

38.5-41.5 Schist cuts at 25°-30°.

41.5-43. Quartz pegmatite with trace of feldspar and 

mica; relict (?) foliation cuts at 40°-55°.

56-58.3 Contorted and tourmalinized schist.

73.5 Pegmatite contact, irregular; cuts about 50°.

Plagioclase-quartz pegmatite.

73.5-77.5 Very fine-grained pink plagioclase (75 percent), 

quartz (25 percent), muscovite (X).3 Faint 

banding cuts at 45°; streaks and patches of 

fine-grained quartz and muscovite.

77.5-78.3 Plagioclase (45 percent), quartz (35 percent), 

muscovite (20 percent). Fine-grained.

Pegmatite, mainly cleavelandite-quartz.

78.3-79.5 Plagioclase (95 percent), muscovite (5 percent). Plagioclase, pale-pink and platy.

79.5-87.8 Pale-pink cleavelandite (57 percent), quartz 

(35 percent), muscovito (8 percent). Medium-grained. Exceedingly fine-grained 

green mica in cracks and cleavages. Relict 

spodumene (?) 0.1 foot wide at 82 feet.

Plagioclase-quartz pegmatite. Plagioclase (85 percent), quartz (10 

percent), perthite (5 percent), muscovite (X). Fine-grained, dirtytan. Some manganese oxides; banding cuts at 70°.

Quartz-mica schist impregnated with pegmatite. Foliation cuts at 

60°.

Plagioclase-perthite-quartz pegmatite. Pink plagioclase (60 percent), 

pink perthite (30 percent), quartz (10 percent), muscovite (X). 

Fine-grained, mottled.

97.9 Schist contact, embayed; average cut about 

70°.

Quartz-mica schist._ . ........

99.2-100.5 Schist contorted.

100.5-110.0 Cut of foliation decreases from 50° to 25°.

See footnotes at end of table. 

295165 55 9

0.0005

.1037
124

Altitude of collar: 8,109 feet. 

Bearing: S. 21° W.

Feel

0-6

6-90.5

90.6-93.5

63.6-99.0

89.0-103.9

103.9-107.3 

107.8-112.7

11 Drill hole BH-2

Description

Inclination: 45°. 

Total length: 147 feet.

Beryl: area on core

surface, in square

feet (see fig. t4)

Overburden. _ ____ .. 

Quartz-mica schist. Medium-gray, fine- to medium-grained____. 

15-17 Biotite bands cut' at 90° and a faint foliation

cuts at 45°.

17-20 Stringers of quartz cut at 5° to 20°. 

24.5 Pegmatite 0.8 foot wide cuts at 20° to 40°. 

Fine-grained. Plagioclase (75 percent), quartz

(20 percent), muscovite (5 percent). 

25.1-29.4 Schist. Medium-gray, fine-grained. Quartz

(70 percent), mica (20 percent), feldspar (10

percent). Lenses of quartz and biotite 0.04

foot wide. 

29.4-47.8 Schist. Medium-gray; light and dark bands

0.005 to 0.01 feet wide; many quartz veinlets

and lenses. Quartz (90 percent), mica (10

percent),

47.8-53.8 Schist not banded as above.

53.8-63.0 Banded schist.

63.0-66.0 Contorted schist with quartz stringers and

blebs.

66.0-83.0 Schist with light and dark bands. 

83.0-84.0 Quartz blebs in deformed schist. 

84.0-84.5 Tourmalinized and pegmatitized granulite.

Cuts at 30°. 

84.5-85.9 Plagioclase-quartz-muscovite pegmatite.

Fine-grained; stained by manganese oxides;

contains schist relicts. 

85.9-90.0 Schist. Light-gray, fine-grained. Quartz (75

percent), mica (25 percent). At 86.5 feet,

plagioclase-quartz pegmatite 0.3 foot wide

cuts at 60°.

90.0-90.5 Quartz-impregnated schist. 

90.6 Pegmatite contact cuts at 60°. 

Plagioclase-perthite-quartz pegmatite. Fine-grained; pink-mottled. 

Plagioclase (55 percent), perthite (30 percent), quartz (15 percent), 

muscovite (X); J green mica in fine scales in cracks and cleavages.

Relicts of schist cut at 58°.

Pegmatite, mainly plagioclase-quartz. ..------------ . ...

93.5-97.5 Pegmatite is fine grained; plagioclase somewhat platy. Platioclase (85 percent), quartz 

(13 percent), grains of perthite (2 percent), 

flakes of muscovite (X).

07.S-QO.O Quartz ,_ . (95 ........ percent), ... pertHite (Spercent) . .

stitial plagioclase and muscovite (2 percent). 

Pegmatite, mainly quartz-cleavelandite99.0-100.5 Quartz (99 percent) with many fine fractures 

filled with cleavelandite (1 percent); very

fine-grained green mica (X).

100.5-101.5 Quartz (50percent), cleavelandite (50 percent).

Medium-grained. 

101.5-103.9 Cleavelandite, white and pint.

PlagiOClase-quartZ pegmatite. Fine-grained. Plagioclase (65 percent), quartz (36 percent), musoovite (X).

PlagiOClaSe-perthite-quartZ pegmatite. Fine-grained, tan. Plagioclase (60 percent), perthite (15 percent), quartz (15 percent), mus112,7 Schist contact cutset so0.

0.0004

.0035

.0290

See footnotes at end of table;
APPENDIX A 125

Feet

112.7-120.0

11. Drill hole BH-S Continued

Description 

Quartz-mica schist, pegmatitized. .

Beryl: area on core

surface, in squart

feet (see fig. S4)

114.5

120.0-132.0

132.0-147.0

Plagioclase-perthite-quartz pegmatite 0.7 foot 

wide, concordant with foliation; cuts at 45°.

114.5-118.0 Schist. Medium-grained, light-gray, prominently banded. Light bands are quartz (60 

percent), feldspar (40 percent). Dark bands 

are quartz (70 percent), biotite (25 percent), 

tourmaline (5 percent). 

118.0 Fracture cuts at 60°. 

118.0-120.0 Foliation cuts at 25° to 30°. 

120.0 Pegmatite contact, discordant with schist

above, cuts at 45°.

Perthite-plagioclase-quartz pegmatite. Fine-grained, pink to tan. 

Perthite (45 percent), plagioclase (35 percent), quartz (20 percent), 

muscovite (X). 

121.6-122.3 Micaceous streaks, parallel to contact, may be

schist relicts.

130.3-132.0 Tan and mottled, very fine grained. 

132.0 Pegmatite contact, irregular; average cut

about 30°.

Quartz-mica schist. Grades downward from fine-grained and medium-gray to coarse-grained, light-gray, and banded. Cut increases gradually from 20° to 60°.

0.0016

. Drill hole BH-S

Altitude of collar: 8,104 feet. 

Bearing: S. 21° W.

Inclination: 46°. 

Total length: 110 feet.

Feet

0-6

6-47.6

47.5-51.8

Beryl: area on core 

surface, in square

Description feet (see fig. IS) 

Overburden..__..__.. .. ..__.. .........

Quartz-mica schist. Medium-grained, light-gray; prominent banding. .........

6-12 Foliation cuts»at 60° to 60°.

12-21 Coarse banding cuts at 60°, and a fine foliation 

of alined biotite flakes cuts at 30°.

21-30 Foliation and banding cut at 55°.

30-33.6 Bands are lenticular and anastomosing.

33.5 Tourmaline-quartz-biotite schist 0.1 foot wide.

33.6-45.5 Banded schist.

45.5 Quartz vein 0.2 foot wide with biotite-rich 

margins.

45.5-47.5 Quartz-mica schist. Medium-grained, medium-gray, containing tourmaline (5 percent). Two equally well developed directions of banding cutting at 35° and 50°.

Concealed zoned pegmatite; see table 14. Contact destroyed...___. .........

47.6-48.4

48.4-48.9

48.9-50.4

50.4-51.2

Quartz (50 percent), muscovite (30 percent), 

plagioclase (20 percent). Fine-grained.

Cleavelandite (90 percent), quartz (10 percent). Dendrites of manganese oxides in 

cleavelandite. Fine-grained.

Quartz (98 percent), pale-green lithia-bearing 

mica (2 percent). Medium-grained.

Cleavelandite (85 percent), quartz (12 percent); 

muscovite (3 percent). Fine-grained.

Quartz (50 percent), plagioclase (30 percent),, 

muscovite (20 percent). Fine-grained. Last, 

0.3 foot of pegmatite shows preferred mineral 

orientation normal to contact. Contact 

cuts at 60°.

See footnotes at end of table.
126 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Feet

51.8-65.2

65.2-70.1

70.1-89.0

12. Drill hole BH-S Continued

Beryl: area on core 

surface, in square

Description feet (see fig. SS)

Quartz-mica schist. Fine-grained, dense. Quartz (90 percent), mica .____. 

(10 percent) predominantly biotite, tourmaline (X).2 Fine evenly 

spaced micaceous bands cut' at 55° to 60°.

60.2 Tourmaline-rich band 0.1 foot wide; tourmaline 10 percent.

60.3-65.2 Tourmaline-bearing (2 percent) schist. 

65.2 Pegmatite contact marked by 0.01 foot quartzenriched schist, cutting at 65°. 

Pegmatite, mainly plagioclase-quartz. 

65.2-65.5 Quartz (50 percent), plagioclase (48 percent), .........

muscovite. (2 percent). Border zone with 

relict foliation parallel to wall rock and contact. 

65.5-66.2 Platy plagioclase (70 percent), quartz (30 per- o. 0008

cent). Some manganese oxide. 

66.2-66.9 Platy plagioclase (95 percent), quartz (5 per- .........

cent). 

66.9-67.6 --._.-----_. Platy plagioclase (70 percent), quartz (20 per- .........

cent), muscovite (10 percent). Very finegrained; faint banding cuts at 70° to 90°. 

67.6-69.1 Quartz (50 percent), muscovite (45 percent), .........

plagioclase (5 percent). 

69.1-70.1 Plagioclase (90 percent), quartz (10 percent), .........

muscovite (X). Dense, fine-grained, tan. 

Pegmatite, mainly plagioclase-quartz.

70.1-73.4

73.4-74.3

74.3-74.7

74.7-77.3

77.3-77.5

77.5-89.0

89.0

97-100

102.3 

ioa-ioe 

See footnotes at end of table.

Plagioclase (65 percent), quartz (30 percent), 

muscovite (5 percent). Fine-grained. Micaceous streaks and patches cut core at 55° 

to 80°, and look like relict schist.

Platy plagioclase (60 percent), muscovite (40 

percent). Medium-grained.

Plagioclase (65 percent), muscovite (30 percent), quartz (5 percent). Fine-grained,

with relict schist.

Platy plagioclase (85 percent), quartz (12 percent), muscovite (3 percent). Fine-grained; 

banding cuts at 45°.

Muscovite (60 percent), quartz (35 percent), 

plagioclase (5 percent).

Plagioclase (80 percent), quartz (17 percent), 

muscovite (3 percent). Fine-grained, pink;

some manganese oxide.

Pegmatite contact cuts about 40° 

Quartz-mica schist. Fine-grained, light-gray;

widely spaced fine banding. Quartz (85

percent), mica (15 percent). Foliation cuts

at 35° to 50°.

Banding irregular.

Quartz vein 1 foot wide with biotite selvagea,

Contorted schist.

.0033

.0004

.0006
APPENDIX A 127

IS. Drill hole BH-4

Altitude of collar: 8,081 feet. 

Bearing: S 21° W.

Inclination: 45°. 

Total length: 110 feet.

Beryl: area on core 

surface, in square

Feet Description feet (see fig. £6) 

0-5 Overburden....__ _ ..... .

5-18.8 Quartz-mica schist. Fine-grained, medium-gray; fine even banding. .........

Quartz (75 percent), feldspar (15 percent), mica (10 percent). Foliation cuts i at 50° to 75°.

11.3 Drag fold of 0.05-foot amplitude strikes at right 

angles to maximum dip of foliation, that is, 

may be horizontal drag fold. 

18.4-18.8 Tourmalinized schist. Foliation cuts at 55°

and 75°.

18.8 Pegmatite contact not recovered. 

18.8-20.4 Pegmatite, mainly plagioclase-quartz.

18.8-19.5 Plagioclase (80 percent), quartz (15 percent), ..... .

muscovite (X),2 Fine-grained, tan; 

banding cuts roughly at 70°. 

19.5-20.4 Quartz (50 percent), muscovite (30 percent), 0.0021

plagioclase (20 percent). 

20.4-23.0 Pegmatite, mainly cleavelandite-quartz.

20.4-21.6 Cleavelandite (97 percent), muscovite (3 per- .........

cent). Dark stains. 

21.6-23.0 Cleavelandite (85 percent), quartz (12 per- .0022

cent), muscovite (2 percent). 

23.0-35.0 Pegmatite, mainly plagioclase-quartz.

23.0-24.0 Quartz (60 percent), plagioclase (38 percent), .........

muscovite (2 percent). 

24.0-25.8 Fine-grained sugary-white plagioclase (80 .........

percent), quartz (10 percent), muscovite (10 

percent).

25.8-35.0 Tan plagioclase (85 percent), quartz (10 per- .0010 

cent), muscovite (5percent). Fine-grained; 

irregular grain size. Contorted micaceous 

streaks between 26.5 and 27.5 feet. 

35.0 Contact not preserved. 

35-110 Quartz-mica schist_______________________.__ .........

35-35.5 Black-spotted (biotite and magnetite) schist

in silvery (muscovite-rich) schist.

35.5-110 Quartz (97 percent), mica (3 percent). Thin 

widely spaced mica bands in fine-grained 

dense quartz schist. Between 76 and 77.2 

feet, biotite and tourmaline bands, irregular, 

slightly contorted; small lenses and blebs of 

quartz. Between 93 and 110 feet banding 

becomes more irregular, mica more abundant.'

Altitude of collar: 8,088 feet. 

Bearing: S. 20° W.

14. Drill hole BH-5

Inclination: 40°. 

Total length: 240 feet.

Beryl: area on core 

surface, in square

Feet Description feet (see fig. ST) 

0-10 Overburden_______.._..._._______..____ . __ . 

10-14 Quartz-mica schist, contorted. Weathered. Contact not recovered.. .........

14-16 Plagioclase-quartz-muscovite pegmatite. Fine-grained. Plagioclase .........

(80 percent), quartz (15 percent), muscovite (5 percent). Contact not 

recovered. 

16-114.5 Quartz-mica schist. Fine-grained, light-gray, dense. Quartz (95 ..... .

percent), mica (5 percent). Foliation cuts ' at 55°. 

20 Plagioclase-quartz pegmatite 0.15 foot wide. 

27-28 Two quartz veins 0.05 foot wide cut at 18°. 

See footnotes at end of table.
128 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Feet,

14, Drill hole BH-5 Continued

Beryl: area on cmt 

surface, in square

Description feet (see fig. S7) 

Quartz-mica schist. Fine-grained, light-gray, dense. Quartz (95

percent), mica (5 percent). Foliation cuts ' at 55° Continued 

28-42 Hi-denned banding.

42-63 Quartz (90 percent) and mica (10 percent) in 

fine bands. Dense and fine-grained. Foliation cuts at 40° to 60°. 

60.5 Perthite-plagioclase-quartz pegmatite 0.05

foot wide cuts at 18°. 

53 Quartz-muscovite pegmatite 0.05 foot wide

cuts at 25°. 

61 Quartz vein 0.02 foot wide cuts at 18°.

Foliation adjacent to its cuts at 45°. 

63 Quartz vein 0.02 foot wide cuts at 25°.

63-64 Contorted schist.

64-67 Schist slightly contorted.

67-73 Schist much contorted; many irregular patches

of quartz.

73-80.5 Quartz-mica schist. Medium-gray, mediumgrained, evenly banded; bands lenticular. 

Quartz (80 percent), mica (15 percent), feldspar (5 percent).

80.6-89 Schist contorted; many irregular patches of 

quartz.

89-92 Schist evenly banded.

92-97 Schist slightly contorted.

97-101 Schist evenly banded. Two concordant 

quartz veins 0.04 and 0.06 foot wide cut at 30°.

101-102.9 Contorted schist with quartz blebs.

102.9-114.5 Evenly banded schist; cut foliation increases 

from 45° to 70°.

114.5 Pegmatite contact not preserved.

Pegmatite, mainly plagioclase-quartz_.._____._____.._ .........

114.5-116.7 Plagioclase (85 percent), quartz (13 percent), 

muscovite (2 percent). Fine-grained; faint 

banding normal to core.

116.7-117.6 Muscovite (70 percent), quartz (15 percent), 

plagioclase (15 percent). Fine-grained. 

Muscovite in books as much as 0.06 foot in 

 diameter. Faint banding cuts at 75°.

117.6-118.8 Graphic intergrowth of plagioclase and quartz.

Pegmatite, mainly cleavelandite-quartz.. .........

118.8-119.0 Cleavelandite (95 percent), quartz (5 percent).

119.9-120.2 Quartz (65 percent), cleavelandite (30 per- 

. cent), muscovite (5 percent).

120.2-121.9 Cleavelandite (95 percent), quartz (5 percent).

Plagioclase-quartz pegmatite.

121.9-124.0 Platy plagioclase (75 percent), quartz (20 percent) , muscovite (5 percent). Many minute

rod-brown garnet grains at 123.6 feet.

124.0-131.5 Plagioclase (85 percent), quartz (12 percent), ..... 

muscovite (3 percent). Very fine-grained,

tan, Irregular texture. Clots and streaks of

fine-grained, regular-textured white pegmatite composed of quartz (75 percent), plagioclase (20 percent), muscovite (5 percent). 

Quartz-mica schist. Fine- to coarse-grained, light- to medium-gray; .........

fine foliation, well-banded, with many narrow zones of crumpling 

and contortion and small lenses and blebs of quartz. A few feldsparricti pegmatites less than o.e root in width.

J The angle between the axis of the drill core and a planar feature (such as bedding and foliation) is referred to as the cut. 

' (X) indicates less than 1 percent.

114.5-118.8

121.9-131.5

131.6-240

0.0001
APPENDIX B

129
130 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PLAGIOCLASE-PERTHITE51

62

63

82

85

86 

125

131

148

180 

181

182

185

190

191

194

203 

213

214

215

224

230

234

238

247

254 

255

308b

330

331

<un

363

365

369

370

384

386

388

3Qn

428

436

438 

446

452

4 S3

456 

417

460

489

500

eno Ovv 

509

.510

Schist.......

Schist.......

 do 

.....do .... 

.. do. 

.....do ..

.....do ....

Schist. 

.....do ...

.....do ....

.....do.... ...

.....do... ....

.....do.......

 do 

.....do....... 

.....do.......

.....do.......

 do 

.....do ...

.....do.......

 do 

-....do ..

.....do.......

Granite..... 

.....do......

--...do......

.....do ....

... ..do ...

 do.. do .

.....do......

.....do......

.....do......

 do 

.....do ..:

.....do......

.... .do.- 

 do.......

 do.. 

. _ .do......

 do... 

.....do ..

_ _ _ _ do_ _ _ _

. .do.......

... ..do.. 

 do... ... 

..... do .

.....do......

.....<to...... 

.... .do... ...

 do......

N"OTIC

.-do.....

T ....

.-do .

 do 

T.......

T .

T .__

T _ 

T.. ..

T.. ..

... do 

T 

 do 

...do 

... do 

... do 

 do 

 do 

... do 

.-.do .

 do .. "T "I"

T.. ... ..

T . 

T 

T -_._

T.. 

T... 

T. -.--..

T.......

T... 

T.......

T.. ....

T.... 

None

...do....

...do....

... do 

... do 

 do .

. __do__-_

... do .

...do.....

--do-...

 do.....

T 

... ao- 

...do .

...do 

sill. 

Joint-controlled. 

 do 

 do 

... ..do 

Discordant _ -..

 do 

---do .--.

 .do . -----

 do., 

...-do -----

...-do -----

Joint-controlled . 

 do..- 

.. --do..-. ... .

cordant in sill.

 do... . ------

.....do...... 

 .do..... .....

 do.. 

 do...... .

Joint-controlled .

 do.... 

Irregular... 

 .do..- 

.. do .. . .

 .do ... .. .

.... .do ....

.... .do 

-.-__do-_-...-_-.

Concordant.----

Dominantly

concordant, 

----.do...... _ .

-.-do....---

.Discordant-. -

Concordant 

 .do.... 

Tabular... ..... ...

Tabular..... ..

 do --- ...

-. do .... 

-..-do .... .... .

mg.

Lenticular........ 

....-do .. ... .

 .do 

--...do -.

-. do . ..

-...do .. 

 ..do 

 . do .. 

 .do..... 

-- do.. ...

 do ...

 .do. ..... ....

--.-do -- ..

__ .do .. ...... 

 do.... 

Tabular. ..........

 .do 

 .do...... 

.... .do. .....

Ing.

.... .do...... .

Tabular, branching. 

_ .do.... __ 

 ..do. 

 .do...... 

Irregular..........

Lenticular.... -...

Tabular?.. 

IrreEiilar. .---.._--

--..-do. .--------._

Branching.... ....

Lenticular. .......

 .do.... .... ....

.--..do.. ------

---..do ----------

Lenticular.........

.--do..-.... .

-..-do ...............

.... .do ....- 

--... do ....

.---do ...

--..do... ... ....... 

 do....... ......

 do -...

 do... ......

Multiple, homogeneousHomogeneous

 do.. 

Homogeneous ...

.--do ---,-.

 .do .. ___ .... 

Multiple, banded

Homogeneous

Banded __ i...

Homogeneous

-.--do.--..-.- _ .

Multiple, homogeneous

Homogeneous

__ .do .. ....

---do. ..- . 

.--do. --.

----do........

-----do.... .-.-

.....do .....

 .do..... ...

 ..do...... ......

..... do. ......

...-do.-. .. ....... ...

- do............ .,

 .. do...... ... ....

 .do........... ..

 .do- .. ___ ....

 ..do.... ...........

- do...-.-.. . ...

Multiple, homogeneous

Homogeneous. ....

 - do-. - _ _ .... 

 -.flO ............

- do..-..-- . ...

---do-....--- - ...

 do . .... 

.....do... ...............

-----do.-..-.--..-.......

 -do...... 

Homogeneous. ........

.....do. ...... ......

-- do......- 

F

M

F

F

F

M

F

M 

M

M

M

M

M

M 

M

M

M

M

M

M

M 

M

F

M

F

F

M

F

M

M

M

F

F

M

F

F

F

F

F

F

F

F

F

M

M

M

M

M
APPENDIX B 131

pegmatites

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Qarnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES 

QUARTZ PEGMATITES

59

50

50

52

55

51

58

50

46

45

45

45

45

45

45

45

50

48

45

50

45

50

50

45

49

49

40

49

50

49

54

51

53

55

49

51

49

51

50

49

55

50

49

n

58

50 ;

48

48

48

4f.

50

50

50

fiO

39

0 7

4

40

40

40

38

35

39

30

39

38

30

30

30

35

35

30

35

33

40

35

3?

35

30

40

35

35

35

35

35

4?

4?,

37

35

38

35

39

41

30

41

40

40

38

30

40

39

90

3?

40

40

35

40

38

36

40

30

90

30

2

3

' 

8

10

9

10

10

10

19

11

Ifi

25

25

95

?090

19

90

Ifi

12

90

IS

90

9010'

90

Ifi

15

15

15

8

9

9

14

9

10

12

8

8

10

10

15

10

12

8

10

10

11

1fi

12

15

14

10

?0

19

30

2

2

x

X

X

J£

J£

X

1

J£

J£

X

^

X

X

J£

X

X

X

1

1

^

1

1

1

X

0,9

1

x

x

1

1

X

X

Beryl......

----.do .-

Beryl......

...do........

Beryl......

Beryl......

.....do.. .

Beryl......

.. do.....

. .do..._-

Beryl......

.....do.....

.....do.....

0.08

Tr.

Tr.

.07

.1

Tr.

Tr.

Tr.

Tr.

.03

Tr.

Tr.

.01

.07

Tr.

Tr.

fO. 8

tO. 6

tl.l

0. 1-2. 4

tO. 9

tO. 8

tl.5

tO. 6

tO. 7

0. 1-0. 7

0. 1-0. 6

0. 1-0. 5

0. 2-0. 5

0.1-1.8

0. 2-2. 4

0. 2-2. 3
132 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

(Alteration column: T, tourmalinized1. Texture column: F, fine, less than 1 Inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PLAGIOCLASE-PJERTHITE511

617

518 

519

520 

521 

522 

526

535

636 

537

638

539 

544 

546 

547 

548 

555

557

658

660

£63

664

566

fifi?

572 

, 573 

576 

619

624

626 

627 

«qn

goo

647 

654 (Hyatt) >

fiQfl

692 

603

695

696

697

699

702

703

Schist- 

 ..do 

.... .do.. 

 .do 

 do 

.... .do.-..- 

..... do - 

 ..do .

 -do. -

 do 

.... .do-.. 

... -do 

 do... 

 -do 

 -do 

... -do. - 

.... .do. - 

. do-.. 

.....do....-

 do -

 do 

.... . do. 

.... .do..---

 do 

... ..do 

..... do 

.....do 

..... do -

 do -

 do 

. do ..

 do 

..... do 

.....do......

 ..do 

.....do - 

Granite and

Schist 

..... do ... 

..... do ...

__ -do __

. __ do ____

___ do .....do....... . do. : .....do.......

... do.... .

 do 

...do.....

...do..... 

... do 

 do 

 do.....

 do 

 do..... 

...do ..

...do ..

 do 

 do 

...do... .. 

 do..... 

...do... .. 

...do ..

 do....

 do.....

-..do. .

 do ._

 do ..

 do.....

 do 

 do 

T. ...... 

None _ . 

 do..... 

 do do. .

 do 

 do ...do... .. 

T.......

 do 

T......:

Mntio

 do 

 do.....

 do.....

_ do __

_ do __ ...do.....

 do.....

... do 

 do. 

 .. do .... ... . 

 do 

 do.. 

.....do....- . 

 .do.. 

 do.. 

Concordant..,..

 do-.. 

 do.. ----- 

 do.. 

.... . do..-.. . 

 do 

 do.. 

..... do....- 

Discordant. .....

 do...- ...

 do.. 

 do---... .

 .do..- ...

 do.-. .

..... do- ...

Concordant ... 

.... .do.- ... 

..... do. ... ... 

Discordant ... . 

 do...- 

..... do.-..- 

Discordant __ ..

Concordant 

 .do ...

 ..do' ..... ... 

Discordant and

Concordant.....

.....do*.......... 

.... .do ......

Concordant? ....

Concordant..... 

. do.. 

... ..do.. ... ...

 do... 

 do 

 do 

 do...- .

 do.... ... 

 do...... ...

 ..do.... 

 do.. 

 do.... 

 do.... 

 do... 

 do 

 do..... 

 . do..-- 

 do.... 

 do.... 

. do .- 

TrrAunlflr

Lenticular ...---..

 .do... ... 

..... do.... - ....

.....do .

 do.. 

 do._ 

Tabular .

Lenticular........

.... .do ... .... 

..... do... ... 

.....do 

.....do... ....... 

..... do... ...... ....

 do 

.....do... ... ... .... 

 .do... .

__ .do . ...

-..-do...-.- 

.....do. --- --. 

 do. 

 do....- . .... .

 do..--..-- ...

 ..do... ..... ..... .

 .do...- 

 do...... ...

 .do.... 

 ..do... ...

..... do....- - 

 do...- 

 do... 

 do.. 

Multiple, banded ____

. do-...- 

Zoned{^-:::::::::::-

ZonedfS----

Zoned/Wall...... .......

--..-do...- -- 

.... .do... .... ... 

 .do...- ..... 

Multiple, homogeneousMultiple, homogeneous 

. _ -do... ------- - ....

Homogeneous. -

Multiple homogeneous. . 

Zoned:

Outer intermediate .... Inner intermediate....

Homogeneous. ... ... . Multiple homogeneousHomogeneous.... .......

___ do __________ .

___ do- _ - Multiple homogeneous 

Homogeneous........... Multiple homogeneous _

M

F

P 

F

F 

M 

F 

F

M

M 

M

M

M 

M 

M 

M 

M 

F

F

F

MF

M

F

M

M

C

M

F

M 

M 

P

F

F

P 

F 

F

F

F

F

F

C 

C

C

F

F 

F

F

F 

F

rp

i Contains O.OOX to O.OX percent lithiophillite-triphylite which has an average size Of 0.2 Inch,
APPENDIX B 133

pegmatites Continued

0, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

QUARTZ PEGMATITES Contlnuea

45

62

63 

52

65

54

60

52 

45

65

50

45

60

59

50

40

40

5260 

50

45

60

50 

50

50

17

40

5

45

61

AQ

48

65 

52

55 

46

60

55 

68 

45

50

60

50

60

60

48

60

52

62

48 

60 

50

.....

.....

0 3

.1

.4

,5

1

.6

.7

,7

.1

.1

^

^^

t3

t!2

24

36

38 

36 

34

33

41

36 

30

10

30

oc

29

10

35

30

30

38

30

25

30

4

30 

35

30

53

30

65

35

38

40

40

29 

33

35 

38

32

34 

30 

34

25

65

X

96

29

40

40

3?

36

36

39 

40 

40

07

3

6 

3

4

5

4

9

.....

.3

.3

^

^j

t36

t!2 

t!20

30

12

9 

12 

10

12

9

12

?5

24

20

1 Q

20

30

15

30

30

10

10

25

25

35

19 

15

20

30

29

30

20

11

12

1?

16 

15

10 

15

8

10 

12 

26

25

40

45

40 

3

11

10

12

8

12

12

12 

10 

10

 

0.5

1

4 

2

2

3

3

6

.....

.2

.2

^^ i

t36

teo

+48

 ...

1

X 

X

1

X 

X

1

1

1

X

X

1

1

X

1

1

X

1

X 

X

1

7

1

X 

X

.....

0.1

.2.11

2

.1

.5

 .

.1

.1

^

<^J

t3 0. 01- 

lS

001-3

.....

X

X

.... .

.....

X

X

 -

 -

.1

1

 -

 -

n

X

X

X

X

1

X

X

.....

 .... .

 ....

 - -

0.01-2

 - 

Beryl. ..... 

 .do . 

 do ...

 do ...

Beryl.. 

Beryl. .....

 -do.....

 do.....

Beryl......

Beryl...... 

 do.....

Beryl. ... ..

.....do.....

 do.....

 do.....

 do.....

Beryl. . ....

Beryl. . . 

 do.....

Beryl. ..... 

. do.....

Beryl......

 do... ...

 do 

Apatite .... 

Bismuthinite 

Uraninite

Beryl... ... 

.....do 

.07

Tr. 

.7 

Tr.

.13

.08 

.01

Tr.

.07

Tr.

Tr.

Tr. 

Tr.

.07

.31

.00

.07

Tr.

Tr.

Tr. 

Tr.

Tr. 

Tr.

.35

.35

Tr.

1.7

X

.008

.OOOX 

Tr.

Tr. 

Tr.

0. 2-1. 7

0. 1-0. 4 

0. 1-0. 6 

0. 1-0. 8

0.1-1.0

0.1-1.2 

0.1-0.8

*0.1

0. 1-0. 6

0. 1-0. 4

0. 1-0. 4

tO. 9 

0. 2-1. 2

0. 1-0. 8

0. 1-2. 7

0.1-3.0

0. 1-2. 4

 0.2

tO. 8

tO. 4 

tO. 7

tO. 4 

0. 1-0. 5

*<1

*<1

0. 1-«0

0. 1-0. 6 

0.1-3

0.01-1.5

tO. 3 

tO. 6
134 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

(Alteration column: T, tourmalinized. .Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmai|tite 

[(Pi. 5)

WaU rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PLAGIOCLASE-PERTHITE708 

712 

 715 

719 

847 

856 

867 

874 

876

877 

878 

879 

894 

905 

906 

907 

908 

1010 

1011 

1015

1025

1026 

1031 

1105 

1109

mi

1146 

1170

1171 

1172

1174

1175 

1176 

1177 

1179 

1203 

1204 

1205 

1215

1246

1248

1274

Schist. ...... 

.. do .

.....do ....

.....do.......

. do 

.....do.......

.....do.......

.....do....... 

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

-...do.......

.....do..... ..

.....do.......

 do 

..... do... ....

___ do. .

__ -do 

.....do.......

 -do 

 do 

... -do 

... ..do ... 

 -do 

.....do.......

___ do. ......

.....do.... ...

.....do.......

 -do... ... .

.....do ..

 -do 

__ -do- _ .-

__ .do. __ ..

Granite

Schist.......

None. 

 do.....

 do 

 do 

 do 

T__ 

 doNone .... 

T. 

...do.....

 do 

 do 

 do 

... do 

... do 

...do.....

 do 

... do 

 do 

... do 

 do__

 do... ..

T. ..____

None 

 do 

...do 

... do 

 do- 

... do 

... do 

_ do 

_ do ...do 

...doConcordant _ .. 

..... do... .... 

Discordant? _ -. 

..... do..... ......

Concordant.-... 

..... do .....

..... do 

Discordant ...... 

Concordant- ....

.... .do.... ... ....

.....do .... .

 do ......

..... do... ..... ...

..... do..... 

..... do .....

Discordant.. ...

- do. . ..

 do..... .....

 . -do ....

..... do.... .... ..

 -do... 

Concordant. ....

Discordant _ ... 

Concordant ..

.....do... ........

 do -

Discordant _ ... 

.... .do ......

....-do- -..-.

.....do ... ...

..... do..... ..... .

___ do . ....

Concordant. 

Discordant 

 _do ... Concordant... _.

..... do ......

Irregular?.... 

..... do... ....... . ..

Lenticular. . .

.... . do ...... ...

.....do 

 do... 

. .do. ... .....do.... .........

.... .do .......

.... .do .......

 .. do... ....

..... do ... ..-

 ..do ....

 do ...

.-. do ..- .

 do . 

. do . .. .

Lenticular 

branching.

__ .do ...

.....do .......

 do ......

__ do .

 do 

__ .do ___ ...

Branching lenticular.

 -do Irregular branching. 

...-do ........

Lenticular..... .. .

 .-do ... ,.

... ..do ---.....

.....do .........

Lenticular

Lenticular

branching.

Multiple homogeneous..

. _ .do _ . ..... 

.--do . _ Multiple homogeneous. 

__ do _ . ...

 do ......

Homogeneous. _ .. .. ..

__ do _ . ....

..... do.... 

.....do ... .

.....do.. ..............

Multiple homogeneous.. 

Homogeneous. _ . _

__ -do. . ___ .

Multiple homogeneous. . 

. ..do .............

Homogeneous. ...

 do...... .... .......

- do ... .

Multiple homogeneous.

Homogeneous. .

Multiple homogeneous..

1 Multiple.- ...

with one zoned memu nr/Wall ., ......

ber(Core.... .....

Multiple homogeneous.. 

Horn ogeneous. . .

Multiple homogeneous- Homogeneous. -.......-.

..... do ...... .... 

 ..do ..... ....... ....

 do . .. ..

--.do ------- ..

... ..do....... . ...........

-..-do -. _ 

__ .do ---. _ . .

Homogeneous. . .....

 do 

__ .do.. _________

F 

F 

F 

F 

F 

F 

F 

F 

M 

F

F

M

F 

F 

F 

F 

F 

F "M 

F

F

F

F 

F 

F 

F

P 

MF

F 

F.

F

M

M 

M 

F 

F 

F 

M 

F

F 

F

MF
APPENDIX B 135

 pef/m a fifes Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perth ite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size;

PEGMATITES Continued 

QUARTZ PEGMATITES Continued

50 

45

48

48

KK

4*

53

CA

48

55

55

RK

fiO

60

59

50 

50

52

52

52

55

48

48

50

52

45

55

in

 fi9

50

48

59 

v>

58

60 

54

CO

50

52

49 

55

.....

.....

0 3

.6

-----

.....

-..-.

35 

35

40

33

35

38

35

38

37

37

37

37

38

28

25

37 

37

38

30

40

34

40

30

34

30

35

20

en

qo

30

38

40

5 

5

40

32

28 

34

40

41

18

40 

30

-----

2

5

-----

.....

.....

15 

20

1?

18

10

16

12

14

8

8

8

19

12

15

13 

13

10

18

8

12

22

16

18

18

24

17

17

8

12

12

35 

in

9

12 

12

9

18

28

11

15

.....

.....

1

4

-----

.....

.....

X

X

x

j£

1

X

1

1

1

J£

^

1

1

X

1

X

.....

.....

0 1

-----

.....

.....

.....

.....

^

.....

jj

X

.....

.....

-----

.....

.....

.....

X

1

X

X

1

2

}£

-----

X

.........

.........

ti.fi

0. 1-1. 5

---------

.........

.........

Beryl......

Beryl......

Beryl......

.....do......

.....do......

Beryl......

Beryl......

Beryl......

Beryl......

Apatite.... 

Beryl......

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr. 

Tr.

fO. 4

0. 1-0. 4

0. 1-0. 9-

0. 1-0. 5

0. 1-0. »

tO. 9-

0. 1-0. 5

tar

0. 2-2. 4

0. 1-0. 2 

tO. 5
136 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinlzed. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PiLAGIOCLASERATIO OF PERTHITE TO PLAGIOCIASE

10 

21 

46

-47

-48 

49 

-50

54 

56 

57 

58 

69

60 

.61 

 64 

. >68

75 

80

93 

101

102 

103

104 HO 

112 

120 

- 121 

122 

123 

137 

145 

147 

149

156 

160

163

164 

197 

207

220 

228 

233

239

240 

242 

243

OA9

Schist 

.... do ..

....do ...

.... do 

.... do 

Schist... ....

Granite.....

... .do 

___.do 

.... do -

Schist- ...... 

Granite. .

 do.... 

_ .do... _ .

....do 

Schist... . 

.... do 

 dO - 

Schist and 

granite. 

Granite and 

schist. 

Granite .....

 do 

.... -do 

.....do 

.... do 

.... do 

.....do 

 doGranite-. ...

..... do .

 doGranite and 

schist. Schist. 

__ do 

..... do -

 do 

..... do. 

... ..do 

 do .

flmnltfl

-do 

..do 

T. 

T. 

T ... None - 

T.......

T..' 

T 

T. ......

None 

..do 

T 

T 

T. __ . None 

..do.....

..do - 

..do -

..do - 

..do 

..do 

..do ~ 

-do 

T-- -

None 

... do .

..do 

T -

..doNone . 

T. ......

None 

...do .....

...do 

...do-..

...do 

...do 

...do 

... do 

...do....

... do ...do - 

...do 

... do 

r\n

....do 

Concordant in 

sill.

....do 

Concordant. .... 

Concordant in 

sill.

....do 

....do 

Concordant ..... 

Concordant in 

sill.

Joint controlled. 

Discordant __ . 

__ do ___ .

Concordant In 

sill, in part.

Concordant 

 do 

.... do 

....do ...

Concordant In 

sill.

Discordant ___

__ do ........

.... do 

.... do 

....do - 

....do............

.... do ... ... . 

.... do .... 

Concordant __

___ do. 

Concordant In sill.

Concordant.....

IHIIdoI -!--

..... do 

__ .do- - __ Concordant, in 

part. Concordant. ... .....do. . _ .. 

... ..do - 

Discordant.. ...

do -----

 do ... .......

Lenticular 

branching. 

Tubular branching. 

....do.....-. ....

.... do 

Tabular........ 

... .do....... ......

....do... .......... 

 do ..........

Tabular, branching. 

Branching.... ....

.... do ......... .

 do ...

Tabular 

Irregular ... .....

 do 

....do.... .... 

.....do ... ... 

..... do .... ....

...... do 

.... do ..... ....

Lenticular.. . .....

..... do 

. __ do- ____ .

Lenticular........

 ..do 

.... .do ..

 -do 

 ..do 

... ..do 

.... .do 

.... .do . 

.....do 

.... .do .......

Irreeular __ 

_ .do ..............

... .do ...

... .do ... ..... ......

.... do... ,. .....

....do.... ...............

....do... ................

.... do .......... ....

.... do ... ........

....do .... -... .... ... 

....do ...... ... ......

....do ......... .

.... do ... 

....do 

.... do ... 

 do ....... 

 do ..... ... .

 do 

Multiple, homogeneous- -

....do.. ..........

....do 

.... do ... ......

Multiple, homogeneouS-

 do ___ ---..--.__...-

..... do 

..... do ... . 

..... do 

Banded 

Banded - 

Homogeneous . 

 do 

 do... .....

.....dO .....- : 

"Multiple, 'homogeneous

..... do ... 

 do .... 

Multiple, homogeneousHomogeneous .... 

 do - 

.... - do ... .....do.......... ..... 

.....do.... ...........

F 

M 

M

M

M

M 

F

M

M 

M 

M 

F 

M

M 

M 

M 

F

M

MF 

F 

F

M 

F

P 

F

F

F 

F 

M 

F 

F 

M 

M 

M 

MMV

F

M

F

F 

F 

M

M 

M 

M 

M

M
APPENDIX B 137

pegmatites Continued

0, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent ' Size

PEGMATITES Continued

QUARTZ PEGMATITES

IS ABOUT 1 TO 1

4n

40

47

49

AK

4^

47

41

49

AZ

49

47

42

42

39

43

37

42

40

38

4fi

41

44

43

48

48

42

40

42

49

42

37

35 

an

40 

35

39

40

40

40

40

40

40

47

45

40

40

42

40

0,3

.....

41

45

4R

45

45

47d<*

49

46

45

4fi

45

4fi

47

44

44

45

50

45

43

4?

49

48

48

44

50

49

51

40

. 4?

46

43

40 

48

40 

45

45

45

45

45

44

40

45

40

40

45

40

38

40

0 7

.....

.....

1?,

14

9

11

10

9

9

ft

12in

12

8

12

11ifi i?

17

8

14

18

12

10

8

ft

8

12

9

9

9

9

12

1ft

23

12

20 

10

15

14

15

14

Ifi

20

15

13

15

15

20

20

20

0.5

.....

.....

3

1

1

1

1

X

1

1

X

1

X

X '

X

X

X

X

1

1

1

X

1

X .

X

X

X

X

X

.

0 1

.....

.....

X

-----

.....

!

i

.....

.....

1

1

X

X

1

.....

0.1

.........

.........

,

Beryl. 

_ .do... 

Beryl.. 

 ..do......

Beryl.. 

Beryl.. .... 

__ do ......

.....do......

.-.Tr.

0.06

Tr.

Tr.

Tr.

 Tr.

Tr.

0.2

.03

Tr. 

Tr.

Tr.

Tr.

l; _

i

-| 0.1-0.4

0.1-0.9

0.3-1.8

i

0. 2-1. 8

0.1-0.9

! '

0. 1-1. 8

, 0. 2-0. 4

i 0. 1-1. 8

0. 4-1. 7

t4.2

i 0

0.1-4.0

0. 1-0. 5
138 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent-. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

jormation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Tex- 

'ture

FELDSPAR-RICH

PEKTHITB-PLAGIOCLA8E-QUARTZ

RATIO OF PEBTHITE TO PIAGIOCIASE

?fi6

268

272

273

278

284

292

OQO

294

296

300

309

oir»

311

01 0

O10

310

320

321

343

141;

346

351

oco

357

359

360

w367

OQC

Qfi7

389 

392

407

420 

421

flU f) 41 J

45/i

.....do.. -.

.....do.. ..

..... do 

 do ..

 do _

.....do .

 do 

. ._ do... 

 do 

.....do.......

.....do... ... .

schist.

.....do 

__ _ do 

 do 

... ..do 

 do 

.....do.......

.....do 

.....do. ...

.....do.. .

.....do......'.

... ..do...... .

.....do.......

..... do .

 ..dO. 

_. do. 

.....do...... .

.....do. . -

.....do....... .....do .... 

.....do 

.....do... .

___ do...... 

... ..do......

... ..do......

Qranite..... 

 ..do......

.....do......

.....do......

T. ......

T.......

T_ .

...do...-.

...do.....

T...... .

T.......

T.. ..

T. ......

T. ......

...do.....

...do.....

...do.....

...do.....

...do.....

... do.....

...do.....

...do.....

T. ----..

T......

T. ...

T...:...

T.......

T. ...... 

T.......

T. ------ 

T.. 

...do.... .

T. ...... 

T.......

...do. .

... do .

None. 

...do 

_ do. . 

...do .

,..flo..«.

...do.....

.....do... ........

.....do .......

.....do ......

.....do ........

Discordant---.--

..... do ......

.....do ........

.....do .......

ant.

.....do ......

ant.

.....do ......

.....do..... ......

.....do ......

.....do .......

.... .do ..--.-

 do .......

......do..........

.....do..... ......

 do 

... ..do ......

.....do ......

.....do ....... 

.....do ......

Discordant......

.. do. _____ . 

.....do... ... .....

.....do. .....

Concordant In

sill. 

Discordant.. ....

Concordant in

sill.

-.--.do..-...--..

... do it ,,,ftv- .....----

Concordant?.....

Tabular, branching. 

.... .do 

 do . 

.....do. ...... ..

.....do ... .....

.-...do ..-....

.....do ... _____

.....do ... ....

.....do ........

.....do ........

....-do .......

..... do ... .....

Irregular. -.--.--..

ing.

Lenticular, branching. 

Lenticular.... ....

 ..do ... ... .

ing.

.....do .--...

ing. 

Tabular--

Tabular, branching. 

.... .do 

Tabular.... ..... ..

.....do .......

 .do- . _.__. 

Tabular.. ...

 .do ...

..... flO ....- ....

Tabular, branching.

Tabular--

Irregular, branching.

Tabular,. ____ ..

Irregular, branch- ing.

 ..do---- -- 

Irregular, branching.

.....clo-. ----------

Lenticular, branch- ing.

..... do 

.....do . .......... ...-

..... do... ... 

..... do . 

.....do .... ......

... ..do 

.....do .............

.....do .... ...

 do .

...-do .... ......

.....do ... . ........ .

...-do ... ...........

.....do -.--.. ......

.....do ..

.....do ..... ..... ....

.....do .............

Homogeneous- . . __

.....do. ..-.. .......

Banded-.---.-.---......

.....do.... ...............

..... do ........ 

.....do ..... ........

.....do .....

.....do .-.....-

.....do _ 

.....do ..-. --

.....do . 

.....do ................

...--<JO----..__-_._______.

.....do. . -....do ...... -------

Multiple, homogeneous 

Homogeneous ...........

__ .do...... ... 

. .do...-.... ......

 .--do.-.--.- -------- 

.....do:.....------ -

do ____

....A... 

M

M

M

M

M

M

M

F M

M

M

M

M

F

F

F

F

M

M

F

M

M

M

M

M

M

F

M

M

M

M

F

F

M 

M

C

F

M

F

F

F

F

V

M
APPENDIX B 139

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

f, maximum; *, average]

Pegmatite Continued

Mineralogy

.Plagiov clasc

Percent

Size 

(in.)

Pcrthitc

Percent

Size 

(in.)

.Quartz

Percent

Size 

(In.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Toucmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued

PEGMATITES Continued 

IS ABOUT 1 TO 1 Continued

38

40

40

40

45

43

40

49

40

37

40

42

47

43

43

43

42

41

44

44

4?

48

45

48

45

4?

39

48

40

48

45

42

45

40 

47

40

QQ

35

QQ

**S

^4

40

0 5

.5

.....

43

40

45

45

42

48

45

4?

45

48

45

47

45

48

48

48

48

47

48

49

45

4ft

4?,

45

45

48

49

47

45

4?

48

42

47

47

48

40

43 

42

40 

41

40

45

4?

40

47

3

5

 ...

19

20

15

15

13

9

15

9

15

15

15

11

8

9

9

9

10

12

8

7

11

9

10

10

7

7

10

11

1fi

101?

10

8

12

9

15

16 

11

11

19 

Ifi

24

15

19

OK

3

4

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

1

1

J£

1

1

1

1

2£

x

0,2

.3

 

X

x

----- -----

X

X

x

x

X

X

X

X

X

X

X

X

X

X

1

X

X

X

1

X

X

X

X

6.3

---------

-.....-..

Beryl......

.....do......

Beryl......

......do 

.....do......

Beryl......

Beryl......

Beryl......

Beryl.......

Beryl......

Beryl......

Beryl......

Beryl......

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0.2

1.0

0.9

02

Tr.

1. 7-2. 4

fO. 8

.0.1-0.3

 ' '0- 2-1. 2

0.4-0.8

0. 2-1. 3

0.1

0.5-2.4

0. 1-1. 7

0. 2-2. 1

0.2-8.4

0. 7-3. 6

1x1.3

295165 55- -10
140 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmallnlzed. Texture column: F, fine, less than 1 inch; M, medium, 1-4 Inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation'

Alteration

Pegmatite

Eelation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTHTTE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

463

464

465 

466

468 

471 

472 

474 

476 

477 

478 

482

486 

492

 493 

496 

604 

512 

515

516 

523

627

tno {US 

541 

553a 

553b 

554

559 

561 

502 

570

571

578 

579 580 

585 

586 587 '588

 -1Q1 i)yi 

592 

. 601 

606 

610

612

618

620 

623

Granite ... 

.....do......

 do 

 do 

 do.. 

 do.. 

... ..do.. 

 do.. 

 -do.. 

 -do.. 

----do...... 

 ..do.----

Schist and 

granite.

 - do. .. 

Schist ... 

.... .do..--- 

 .do. .. 

. do.- 

 do.. 

.... .do ..

 _db 

 do .

 do.. 

_ ..do..---. 

 do. - 

... ..do 

 do 

Granite 

Schist . 

. do .. do --- 

 -do 

. do.. 

..... do... 

.....do-...

__ .do - 

 . .do.. 

 ..do.. 

. do.. 

..... do 

 do.. 

... ..do .

None.... 

 do.....

... do 

 do 

... do 

...do....

... do - 

 _ do 

... do 

 do 

 . do - 

 do ..

 . do 

T 

 doNone. 

 do 

 do. . 

 do....

 do 

...do 

 do .

...do 

... do. 

...do. . 

... do -

... do 

... do 

 do 

T 

None. 

...do .. 

... do 

 . do 

_ do, __

_ do . 

...do ...do 

 do. 

... do 

... do 

... do -

...do 

... do 

...do 

 .do 

 do.. .... .

Concordant and 

discordant.

-. do......... 

Discordant ... .

 do..... - 

Concordant and 

discordant.

Concordant in 

sill. 

... ..do... ...... .

Discordant?. --

Concordant and 

discordant. 

Discordant? .. 

Discordant.. .

 do.. 

Concordant 

 do- 

 ..do 

 .do 

..... do...... .

DiscordantConcordant in 

sill. 

Concordant.. ....

 do 

 do...... -

..... do... ... .... 

 do 

___ do. __ ____

... -do...- .....do. 

Discordant. 

 do 

Discordant?.....

Discordant .. ..

Concordant.....

.....do... .......

Discordant _

Irregular, branching.

 ..do...... .

 do 

... -do...... 

- do....-- .. 

 -do......-. . 

 do-.._._ 

- do........ .

... ..do... ... 

 do....- .

 .do 

.... .do...... 

 -do-..- 

Lenticular.... . 

Irregular 

 do.... ....

.....do .,..-

Lenticular? _....--

... ..do.... ..... . - 

...... do... ...... ...

 do 

 .do 

... -do....-. 

 .do. 

.....do...... ..... -

 -do-.-. - 

__ .do-...- 

.... .do -

.....do...... ......

... ..do.... _ 

Lenticular.. 

__ .do.... . -

.....0,0...... 

 do... ......... 

Branching _ . ...

,,..-,.,., /Wall... _ . __ ..

ZonedlCore.- .....

Multiple, homogeneous.-

 do......... .... .. 

 -do......- .... .. 

Multiple, homogeneous..

 do....- . 

 do.... 

 do 

Multiple, homogeneous-

 .do. ...... ..

Banded. -------- ____ 

Zoned{^---"-: - -

Multiple, tanded .... .

(Wall.. .... ....

Zoned-j Core (discontinl uous).

Homogeneous.. .........

 .. do-...- 

Multiple, homogeneous- Homogeneous ----------- 

Multiple, homogeneousHomogeneous. ...

Homogeneous ...........

 ,,/Wall. .. . Zonedj r

Multiple, homogeneous- . 

 do.-.. 

 do .............

__ .do--.. ___ ...

Banded.--- Homogeneous.. -

 do.-.-- 

..... do..... 

.... .do.... ....... ... ... .

.---do....---- 

.... .do -

Multiple, homogeneous..

... ..do ... .... ........

M

M 

C 

F

M

F 

F 

F 

F 

F 

F 

F 

F

F

F

M 

M 

F 

F 

M 

F

M

M 

F 

M

F 

M 

F F 

F 

M 

F 

M 

M

F 

M 

F 

F 

F 

F 

F 

F 

M 

F

P 

F 

F 

F 

F 

F

F 

M
APPENDIX B 141

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagloclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued

IS ABOUT 1 TO 1 Continued

42

SO

Q7

3R

40

la

39

40

^a

7Q

38

40

36

37

43

4Q

4fi

dd

64

31

40

48

42

45

35

35

4?l

39

At)

44

45

44

45 

50

14

41

48

41

38

38

39

O7

QQ

37

36 

42

Q7

^Q

45

41

44

0,5

.4

2

6

2

.4

4

,6

,3

,5

.4

46

34

52

44

4(1

43

44

42

41

44

45

40

41

40

49

42

40

47

10

39

48

50 

35

60

<in

39

49

45

50

46

48

45

37 

34

50

48

49!

48

41

41

42

A*)

44

44

43

38

44

AS

40

40

48

6

8

5

.fi

5

.5

4 

2

5

3

5

5

.....

12

1fi

10

17

1Q

19

17

17

20

17

16

20

91

22

8

9

14

ft

OR

29

12

108' 

17

QO

9>;

25

9

15

8

10

7

9

17 

15

OK

11

10

11

21

21

18

20

10

19

21

20

10

1Q

14

10

8

4

7

4

5

1

4

.3

3 

1

4

3

1

4

4

.....

1

1

1

X

1

1

1

X

3

1

1

1

1

1 

1

1

1

X

1

X

0.2

,1

2

1

.7 

1

3

.6

1

2

X

X

1

0.1

.1

1

1

.....

X

X

.....

X

tl.3

.........

.3

.........

Beryl......

.....do.....

Beryl.. _ .

Beryl.. ....

Beryl. .....

.....do.....

.....do.....

Beryl...... 

.....do.....

.....do.....

.....do.....

.....do.....

Beryl...... 

.....do.....

Beryl...... 

.....do-.-..

Tr.

Tr.

0.01

Tr.

Tr.

.28

.05

Tr.

.06 

.1

Tr.

Tr.

Tr.

Tr. 

Tr.

Tr. 

.4

2.1

0.2-0.6

0. 1-0. 7

0. 1-1. 7

0. 1-1. 3

0. 1-0. 3

0.2-0.9

0.2

0. 1-0. 4 

0. 1-1. 2

0.3-0.9

0. 1-0. 6

0.5

0.1-0.4 

0. 4-1. 0

0.2 

0. 2-2. 7
142 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine* less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

 fer.mation

. Alteration

Pegmatite

Relation to wall 

: rock Shape Internal structure Tex- 

.' ture

FELDSPAR-RICH 

PERTmTE-PLAGIOCLASE-QUARTZ

RATIO OF PEBTHITE TO PLAGIOCIASE

628

640

fi41

644 

646

653

659

'660

661

662

fifid

674

A7*\

676

677

686

689

700

7(U

707

709

710

716

717

718

721 

722

793

724

725

726

728

729

730 

731 

732

733 70 e

740

761

770

780 

849

855

857

861

862

863

864

805

866

070 Olu

CC1

882

883

Schist 

 do-. 

 .do 

- do..--- 

 do.-.--

 .do.. 

 .do.... -

 -do.._.-

 do 

.. do .-

..- do- ..

... -do 

__ do 

.....do ..

.....do .

... ..do 

...-.do. ...

....-do ....

..... do -

.--..do.. ..

--...do. ...

 do 

 do -

.....do ...

-.-do -.

---.-do. . ..

... -do .

 do 

- do 

... ..do ...

..-i.adO ....

 do 

... ..do 

..... do -

 .do -

 dO ____ --

 do. 

..... do 

 do 

 -do. .......

--.--do.. -.

..... do... 

..... do_ 

.....do. ..

 do _

..... do -

- do 

.....do ___ -.

... ..do -

 do. 

 do 

...-do -

 do 

 do 

.....ao.~ . 

 do ....

..--do.......

.... .do 

...do... ..

... do 

... do 

... do -

... do -

 do -

 do ..

... do 

... do 

L-.do .

-..do 

___ do 

...do .

...do... ..

..-do 

 do 

...do 

.-do 

...do 

... do 

...do 

... do 

...do.....

--do 

... do 

_ do .

...do.....

...do 

... do. 

....do... - 

.:.do-,-

...do 

...do 

...do 

 do... ..

...do 

.-do.....

 do 

...do .

... do 

-do 

 do ...do ..

... do 

 do 

-- Clo

clo

..-do- 

...do..... 

...do .

....do 

... do.....

.-do.....

_ ao _ .

...do 

...do.....

....doDiscordant..--..

... ..do.-.. -_ -

... ..do......... .

...-.do..........

-..-do..........

.....do ......

..--do .......

-..-do .....

.....do ......

...-.do ......

Discordant? 

discordant.

.....do..... ......

..-..do... ........

.....do .......

..--do ..--.

.....do...........

.---do. ...

--..do. ......

Discordant?, .

..... do ........

.....do... ........

Concordant .

.....dot 

-....do .- .:

.... .do... 

-.-do. --....

. .do ......

. _ .do ..

. __ do ......

..... do ...... 

 do .... .. 

.....do. ......

.... -do ....... .....do.. ..

.....do........ 

.-...do.. ......

---..do ........

..... do. .....

 ..do .

--...do . .....

.....do. __ ------

 ..dO -

 do ......

----do ..--..

Discordant......

Concordant. .

Discordant. _ .

Concordant- _ .

Tabular... .....

Irregular. ...... .-.

Irregular.. ------- .

..... do.. ....--....

.....do...... 

... ..do .....

laj-.do . .- ..

--...do ........

.-.-do ....... ..

.... .do..... .

..--do --- .

...-do . ... ...

.... .do... ... 

... ..do 

.....do 

 . do .. -

-..-.do ........

.... ..do ... .

 ..do ........

. _ .do- .........

- _ _do . .........

 --do.-. _ . .....

Lenticular..- _ .; ..'...do:..... 

. -..do:. ...... .i

 ..do. 

... ..do... ...

..... do 

. do .........

 .-do. -. .......

--- do .... 

.....do... 

.-...do. ........

.--..do... ..........

... ..do 

.....do...... 

.....do ... ....

.---.do ---------

.....do 

..... do ... ...

.....do... ..........

..-do....... -

.. do. .... ...

.....do---.. -----

branching.

Lenticular........

 . do........ .... .

..... do ... ...

Multiple, homogeneous.

Homogeneous. ----------

-- do.-....---..--....

Multiple, homogeneous.. 

-. do---.-..--..- ...

 ..do...... ... ...

.-...do.......-.-.. ..

 .do.. - ___ . _ ...

...-do . .... ... ,^.:jio.. .

...-do .- . ....

-....do -. .......

..... do .. - -.

... -do ... ...... ....

 -.do .... ..... ......

..-..do ..........

.....do..... ..............

Multiple, homogeneous..-

.....do ... _ ..... ..

Homogeneous _ . ...._

. .do.... .. 

Multiple, homogeneous- .

 do .. .

.... .do ... ...

... ..do.... . ... ... 

Multiple, homogeneous . .

 do... .... 

...... do ..... ... 

.....do -.-.. .......

 do ........ .... .

-. do. --...........-.

 do 

.- _ do.-_-_ .._- ...

..... do.... .. 

..... do ....... ..... ..

.....do... ... ..........

.....do . .. _._

Homogeneous--... _ ....

Multiple, homogeneous.. 

Homogeneous...-.....-

 .do .. ____

Multiple, homogeneous-

.... .do -.... 

.....do...... 

-....do ..... . ....

Homogeneous.- ------ 

.....do ...... .......

MUHipTe, noraogeneousHomogeneous. .......

Multiple, homogeneous..

F

F

F

F 

F

F

F

F

M

M

F

M

F

F

F

F

M

F

F

F

F

M

F

M

¥

M

F 

F 

F

F 

F

F

F

P 

F 

F

F

F

F 

F

F

M

F

F

F

F

P

F

V

F

M

F
APPENDIX B 143

pegmatites Continued

 C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Percent

Size 

(in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES ContLrmed 

IS ABOUT 1 TO 1 Continued

40

40

49

40

47

45

4?

46

40

40

40

37

37

34

38

38 

39

38

38

42

52

40

45

40

45

45

40

40

40

40>

40

50

50

50 

4fi

50

50

50

50

50

50

3fi

3fi

34

37

28

43

36 

40

42

42

42

42

42

41

44

42

49

42

-----

0 2

- 

48

47

41

40

40

40

48

40

43

44

44

45

44

45

45

44 

38

44

45

50

40

40

45

AK.

45

44

44

44

50

50

40

40

40 

42

40

40

40

40

40

40

45

45

41

43

31

36

48 

47

47

47

47

47

48

47

39

48

41

49

-----

1 5

.....

12

12

9

20

12

14

10

13

15

18

18

?0

18 

21

18

8

8

20

10

15

10

10

16

16

10

10

10

10 

12

10

10

10

10

10

10

18

19

24

19

40

11

16 

12

10

10

10

10

9

11

17

10

10

9

-----

1

.....

1

1

1

1

1

1

1

1

1

X

?,

X

X

J£

X

X

J£

X

X

1

X

X

1

1

1

1

1

1

1

X

-----

0 1

.....

X

X -----

-----

J£

J£

X

JJ

X

J£

X

X

J£

X 

X

J£

J£

X

---------

 ......

Beryl......

Beryl......

.....do..-..

.....do.....

Beryl...... 

...do........

...do.... ....

--do....--

Beryl. . ....

Beryl. ... -

Beryl..--

Beryl. .. ...

Beryl. .. ...

Beryl. .....

Beryl. .....

0.01

.04

Tr.

Tr.

Tr.

Tr.

.06 

.02

.06

Tr.

Tr.

«

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0. 1-0. 6

0. 1-0. 8

0. 1-3. 6

0. 1-0. 7

0.5

0.9

0. 1-1. 0 

0. 2-0. 6

0.1-1.0

0.4

0.5

0. 1-0. 6

0.4

0.2

0.5

0.3

0.4
144 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHTTE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASB

884

886 

898

903

909

911

912

919

941

945

949

951

973

976

977

980

988

990

997

998

999

1000

1002 

1003 

1005

1008

1009

1018

1019

1020

1022 

1027 

1029

1030

1035

1041

1047

1049

1052

1061 

1076

1108

1 1 V*

1157

1161

1163

1181

1226

1238 

1247

1260

Schist.......

... ..do 

..... do 

..... do 

... ..do ...

 do 

 do ....

. .do .

.....do..... ..

.....do... ....

.....do ...

 do 

.....do.......

.....do.......

.....do ...

.....do.......

 do 

.....do..... ..

.....do.......

.....do ...

.....do 

.....do.......

.....do.... ... 

.....do ... 

.....do.......

.....do.....;.

.....do.......

.....do.......

.....do.......

.....do.......

.....do .... 

.....do....... 

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

.....do.......

.... .do... ....

.....do ....

.....do.......

 .do.......

.....do.......

.. do 

___ do _

.....do.......

 do 

Schist.. .....

T 

None. ... 

...do ..

...do.....

...do... ..

... do .

... do 

.-do 

...do.....

...do 

 do 

...do 

...do 

...do... ..

 do 

... do 

... do.....

 do 

...do... ..

... do 

... do 

...do 

.-do . 

... do 

 do 

 do 

...do 

...do.....

 do 

...do 

_ do 

 do 

 do 

...do .

...do .

... do 

... do 

 do 

,-do 

...do 

 do.. 

...do.....

 doll 

...do 

...do... ..

_ do _-

...do.....

...do . 

...do .

...do 

.....do ......

 ..do 

... ..do... ... .... .

 do 

.....do . ...

.....do ......

.....do ......

 do . 

.....do ......

.....do .......

.....do .... 

...-do ..

.....do ......

..... do ..

.....do ......

... ..do... 

... ..do ...... 

... ..do ......

.... .do .......

.....do..... ......

.....do .

Concordant, 

.-..do ... 

..... do ... ... .

... ..do 

.....do... ... ... ..

.... .do ... ...

.....do ....

 ..do ... .

..... do ...

Concordant . . . . .

.....do...........

D iscordant 

... ..do 

 do. 

Concordant

.....do...........

.... .do 

Concordant.....

..... do... ..

..... do... ..... ..

.... .do... ..........

.... .do... 

..... do... .... 

..... do -

..... do .

 do. ..

..... do. ...

.... .do .... ... .

 do... ... ...... .

.....do. ........

branching.

..... do ... . 

.....do... ... ... ....

... ..do....... ..... .

..... do .... ....

.... .do ..... 

.....do. ........ 

.....do ..... ....

... ..do... ...... ....

Lenticular ........

.....do ........

Lenticular .._- 

 do... .... ..... .

..... do ..... ...

..... do ......

..... do... ... ... ....

..... do ....

.....do ........ .

ing.

 do. ..... .

..... do ... -

.....do.............

Irregular. _..__ 

branching. 

Lenticular... .....

ing.

Lenticular ....-.-.

Lenticular........

..... do 

Lenticular........

Multiple, homogeneous..

... ..do .... ... ... ... .

... ..do.... ... ... ... ......

.....do... .... ........ 

 ..do. 

..... do ... ... 

... ..do. ..... ... ... ...

... ..do .... ... .... .

... ..do ..............

... ..do. ... .... ....

..... do ....

Multiple, homogeneous.. 

__ do ____ . ___ ....

..... do .... 

.... .do.... ....... ... .... .

. __ do.. .. 

..... do 

... ..do ... .... ... ....

..... do ... 

Multiple homogeneousHomogeneous ...........

.....do.... ... ... ..... ....

..... do ........ .

..... do.... ... ....

 do.... .... .... .. 

___ do _____ . ___ 

.. .do. ---------- .....do...................

___ do ___________ 

.... .do. - 

..... do ...... .... .....

.....do 

Multiple homogeneous 

Multipleliomogeneous...

..... do ... 

Homogeneous. . .. . 

Multiple homogeneous...

F

F 

F

F

F

F

M

F

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M 

M 

M

M

M

M

F

F

F 

F 

F

F

F

V

F

F

F

R

F

F

MF

F 

F

P

F

F 

F

F

F

F

M

F
APPENDIX B 145

pegmatites Continued

0, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued.

IS ABOUT 1 TO 1 Continued

39

41

48

41 

43

SO

35

39

29

37

34

37

37

36

37

35

3fi

35

41

43

36

38

40

30

3fi

45

45

4?

4?

45

44

4?:

46

38

4?

36

37

37

35

37

38

37

40

39

4?

34

36

38

4?

44

39 

38

38

37 

44

36

.....

.....

.....

.....

44

47

4?

48 

43

41

47

45

37

4?

4?

43

4?

43

44

44

45

45

41

40

46

45

44

43

45

49

47

46

46

43

45

44

38

40

45

4?

43

4?

43

43

45

43

43

43

48

45

40

43

47

44

38 

43

4?,

43 

44

40

.....

.....

.....

.....

16

1?

10

11 

14

9

18

15

34

21

94

20

21

21

19

91

19

20

16

16

18

16

15

21

19

13

12

12

12

11

13

16

22

13

22

20

21

22

20

17

20

17

18

10

21

24

19

11

12

23 

19

20

20 

12

22

.....

.....

......

.....

X 

X

2

1

1

1

1

1

X

X

X

.....

.....

.....

.....

X

X

X

.....

X

....:

.....

.....

.....

X

X

X

X

.........

.........

.........

.........

Beryl......

Beryl......

Beryl......

Beryl......

Beryl......

......do....

Beryl......

Beryl......

Beryl......

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0.1

Tr.

Tr.

0.2

0.2

0. 3-0. 9

0. 3-3. 6

0. 3-2. 4

0. 3-0. 9

0. 7-1. 2

0. 1-1. 4

0.2-0.7

0. 3-1. 4

0. 6-1. 3
146 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. . Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTHITE-PLAGIOCLASE- QUARTZ

RATIO OF PERTHITE TO PIAGIOCLASE

1

5 

6 

9 

11 

18 

19 

22 

34 

35 

37 

38 

40 

41 

42 

45 

52 

55 

66 

67 

69 

70 

71 

72

73 

76

77

78 

79 

81. 

83 

84 

87

88

89

90

01 

04 

95 

96 

100

106 

107

108

109 

111 

113

114

115 

116a 

H6b

117

118

119 

124 

126

.....do.......

...__ do 

..... do .

.. do 

......do.......

 do 

.....do ..

.....do... ....

 do .

 do 

.....do.......

.....do ....

.....do... ....

.....do..... ..

.. do 

 do .

.....do.......

 do 

.....do... ....

.....do ....

 do 

...-.do.......

 do 

 do 

..---do ..

....do... ... .

.....do 

.....do .. .....do.......

...-.do.-.--.

... .do 

 ..do 

..-.-do ...

_ do 

Schist and

granite.

... ..do..... ..

..... do... 

.....do 

 do .

----do...... 

.....do - 

 -do...... 

----do......

--- <lo .....do.. ~.

 ..do------ 

 do...... 

 ..do......

... do. .

... do 

... do 

... do 

... do 

... do 

... do 

... do 

... do 

 do 

... do 

... do 

... do 

... do 

... do 

 doT 

T 

__. do 

 do 

... do -

 do 

.-.do .

T 

... do 

... do 

... do 

... do 

... do 

... do 

 do 

 .do .....

...do 

...do 

 -do. 

.--do-. 

...do.....

...do.....

..do ..

...do ..... ...do 

....do....

...do . 

...do _

...do.....

 do 

 -do ...do. : 

...do .

... do 

-.doDiscordant......

-.-do 

.....do ...

.....do .....

.....do ......

..... do . ...

.. do ......

.....do ...

..... do . 

..-.do .... ...

-- do ...

..... do . ...

...--do ------

Concordant.....

..... do -

...-.do .....

 --_do._-. ...

Concordant.....

-...do ... ...

Discordant..-.-.

Concordant. ....

Discordant. ..... 

..-_do ...... 

.....do.... .......

.. do.. 

. Discordant -...do... -...:;:

....do 

- do ...... 

Concordant.. 

 ...do ._- .....

Discordant.......

Concordant. .

.....do .... 

Discordant...... 

.....do....---.:

...do....... - 

 - do .... .

--.-.do..-..-.... .....do . 

- do.. ........ 

-- _ do.......... --do::::::^--

 do...... . 

.....do....... 

Irregular..........

Lenticular........

..... do... 

.....do .........

..--do .. ........

..... do. 

.....do ....... ..

.. do ....

.... .do.... .... 

...... do . 

.....do.............

Tabular...... ... ..

.... -do. ........

.....do . ......

Lenticular.. ------

Tabular,, __ .....

Lenticular. .-

-.-.do ........

Tabular, branching.

. __ do.--,,. .

Irregular....... .

Lenticular..... 

. -do. .....,...

Tabular....... -

.....do...'.. .... ....

.-...do.. ........ 

 ..do . ..... ...

..... do ...... ...

 do.... ........ .

__ -do-...-,- __ -_

...do .......

Irregular.. 

Lenticular 

-----do .. __ ". " 

Tabular... _ ....-

 do . 

Xyontioular...

Tabular, branch-" 

ing.

Tabular

..... do..... -

....do....----

.... .do. ........... 

-----do............

.....do...... 

 do............ 

m^doi:::::::::::

.....do........ 

Tabular, branching.

Multiple banded.. ... ... .

Homogeneous. ------....

_ ..do.. ___ . ___ ...

..... do... ...... .... ... ...

.....do. ........ .......

Multiple homogeneous ... 

-..-.do ..............

Homogeneous. .... ___

Multiple homogeneous ...

Multiple homogeneous ... 

.... .do _ .........

.....do. .. _ . _ .. ...

..... do... ..... .. 

..... do ............

.....do ...

.....do ........... ...

.....do... .... ............

.....do ..... ..

 ..do... ................

..... do 

Multiple homogeneous. . .

.__._ do ___ ... _ Homogeneous. . .........

.. do.... .... ... ........

..... do -...... 

.....do ... ... - 

.....do ... ... 

. ...do 

.....do ..............

...do. .-... ...... 

 do ... ......

_ ..do. ...

..... do ... .... Multiple homogeneous. .

. __ do. -- _____

....do.... 

. .do ............

-.. do _ -...

---do...... .......

_ .do. __ ;~:; ------ 

.....do...... -

.....do..... -

 do ,.....

-....do--.-.--.-...

.....do..... .............

 -do..................

;;;;:uo:::::::::::::::::: 

.....do........ ... .... ... 

.1

M 

M 

M 

F 

M 

M 

M 

F 

M 

M 

F 

F 

M 

F 

F 

M 

M 

M 

F 

F 

F 

F 

F 

F

F

M 

M

M 

M 

F 

F

F

M 

M 

F 

F

F 

F

M

MF 

M

F

F

F

F

F

F

F

F

F 

F 

F 

P

M

M
APPENDIX B 147

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

 f, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PE QM ATITES C ontinued 

PEGMATITES Continued 

IS ABOUT 3 TO 2

30

3?

30

35

30

40

30

35

35

35

34

3?

35

37

37

40

40

3?

33

30

30

30

30

31

31

85

S5

37

39

40

40

35

40

40

37

37

42

33

34

34

34

33

37

41

39

38

40 

3fi

40

41

35

38

40

40

38

50

0 4

2

.....

45

55

40

55

55

50

50

55

55

55

55

55

55

50

50

50

48

53

48

4f>

50

49

4fi

53

50

5?

50

55

53

50

49

54

48

48

54

54

50

57

55

55

54

fifi

55

51

52

53

53

55

49

50

55

51

48

48

49

42

3

1

.....

24

13

28

10

15

10

20

10

10

10

11

12

10

12

12

10

12

15

19

18

20

21

24

Ifi

19

12

15

8

8

10

11

11

12

12

9

9

8

10

11

11

12

11

8

8

9

9

7 

9

11

9

15

11

12

12

13

8

3

7

.....

1

2

x

X

X

1

1

X

X

X

1

X

X

Jf

0 4

1

..... ..... .....

X

^

X

X

X

X

.........

Beryl.......

Beryl __.__.

.....do......

Beryl......

.....do......

.....do......

Beryl.......

Beryl......

.....do......

Beryl......

Beryl......

Tr.

Tr. *0.3

.01

Tr.

Tr.

Tr.

Tr.

Tr.

.06

Tr.

Tr.

 0 4

0.2-0.6

0. 2-1. 6

0. 2-0. 6

0. 5-1. 2

0.2

0. 1-0. 3

0.7

0. 01-1

0.2-0.6

0.2 x 0.7
148 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmallnlzed. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PLAOIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCLASE

127

128

129 

130

132

133

134

140

146

151

152

154

157

158

159 

161 

169

170

172 

173

174 

176 

178

179

184 

186

192

193 

195 

198 

199

200

216

217 

218 

219

m227

231 

235

236

244

245

246

249

250

251

ocq

256

257 

261

265

 ..do......

. do.. 

.....do......

.... .do ...

 do 

 do......

.. do......

.... .do......

 ..do......

 do......

.. do... 

.. do... 

.....do......

 do... ... 

.....do...... 

Schist. 

.. do......

. do ... 

.....do......

.. do... ... 

 do.. 

.....do......

.....do......

.....do...... 

 do.. 

.....do...... 

..... do...... 

 do... ... 

Schist and 

granite.

 -do. 

 do... ... 

 do... ... 

 do... 

.....do.......

 do.. 

.. do......

.....do......

.....do......

 do 

___ do 

 do ... .....do......

 do 

.... .do 

 -do... ...

 do

... do.....

... do 

...do 

... do 

.__ do....

 do 

... do. 

 do 

... do -

... do 

... do... -

 do .

... do~ 

... do 

... do 

... do 

... do ..

___ do - 

 do 

... do.... . 

...do 

 do.... .

... do 

 do..... 

... do 

..-do. . 

 do 

 do ._ 

__. do 

... do 

...do 

...do . 

.-do... .. 

... do 

... do .

...do.....

_ do .

 do.... . 

...do.....

... do... ..

... do 

 do ..

-..do- ...

...do.....

... do 

... do.....

.--do.....

None

. do... 

..... do....... 

..... do....... 

.....do.... 

.....do.... 

 ..do... 

 do..... 

-.-do..... ..

 do...... .

 do.... 

.... . do... -

.... .do.... 

 do... -

 do... -

..... do.... 

...-do.... 

..... do.... 

..... do..... -.

 ..do... 

 .do.... 

 ..do.... 

 ..do.... 

 -do 

..... do...... . 

Concordant?. --- 

Discbrdant. 

 ..do.... 

Concordant 

... .. do...... . 

 do. 

Concordant and

discordant.

 do. ....

.. do.-. -------

... ..do... 

Discordant.. .

Concordant 

Discordant .. .

 do.... 

. __ .do..---- 

Concordant.....

Concordant?..-.

 do..... 

 -do....... 

.....do.. ...... 

__- do ' .......

Tabular, branching. 

Tabular __ ...

 -do..... . 

 .do. 

... .do.... ------

 -do... 

 do..... ..

 do...... .

.... do....... -----

.... .do...... ... ...

 do.... - 

Lenticular. .... _. .

..... do....... .. 

.-.-do.....-- .. 

... . .do..... .

 do.....-- 

 do .......

..... do..... 

 do....... . 

 -do...... 

----- do.... .

. do.... .

... -do.... .. 

... ..do.... -

___ do.... 

. ....do-... ------- 

... ..do.... 

 do.... 

... '..do.... .... ..

 do.. ..........

.....do............

..... do...-. .... 

..... do....... .. 

 do..... 

 do 

.....do............

. ---do--.... -----

.-.-do.-.. 

 ..do...... ..

..... do...... 

.....do.. ..........

..... do-... 

.....do............

.. do.... -

 do ..

 do. 

ing. 

Tabular .. 

Homogeneous.. __ . 

 do... ...... ... .

 .do.......... ... 

-....do-.... ... .....

 do...... 

- do.... ...

. do.......-- 

..... do..... . . ... ...

Multiple, homogeneous. .

.....do.....- ... 

.....do... ... 

 do.. 

 .do... 

 do...... . 

 .do.... 

 do..... 

.....do.... ..... 

..... do.... ....

... ..do....... 

Multiple, homogeneous..

.. do..... ...... .

... -do... ... 

... -do....... 

. _ .do.-...-. . _ ....

. .do.... __ ... __ .. 

 do... 

- do...-.-. . -- 

Multiple, i homdg^neolus- .

Homogeneous. ..........

.....do.. .. ..............

 do-... 

.....do-.-... ...... 

Multiple, homogeneous..

. .do..... .. 

 do....... - 

 -do...... .

... ..do...... 

... ..do.... 

 do...... 

__ .do..-- _________

.....do....................

.... ..do... 

.....do. ________ .. ...

.... .do .... ...

...-do-....-. .......

... ..do.... 

M

M

M 

M

!M

M

M

M

M

M

M

M

M

M

M 

M 

F

M

M 

M

M 

M 

M

M

F 

F

M

M 

M 

M'M

M

F

M 

F 

F

M

M

M

M

F

F

F

F

F

F

M

P 

M

M
APPENDIX B 149

pegmatites Continued

O, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Percent

Size 

(in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued. 

IS ABOUT 3 TO 2 Continued

35

40

3?

40

4?

4?

33

39

40

37

31

37

30

35

35

34

30

35

35

35

35

30

35

3?

30

35

30

30

30

30

30

39

35

35 

35

30

38

33

35

30 

38

34

33

40

34 

34

38 

35

35

35

30

30

30

35

29

30

0.5

.....

.....

.....

.....

.....

.....

.....

55

54

55

5?

50

48

55

50

50

45

55

50

55

45

45

50

55

55

50

50

50

55

50

48

55

45

55

55

50

55

55

50

45

55 

55

57

50

50

45

55 

50

43

47

49

50 

48

46 

50

44 

4fi

50

45

55 

5?

45

50

2

.....

.....

.....

.....

.....

.....

9

6

13

8

8

10

1?

10

10

18

9

13

14

20

20

15

15

10

14

14

14

15

14

20

15

20

15

15

20

14

14

10

20

10 

10

13

12

17

20

15 

11

20

19

11

15 

18

16 

14

19 

18

19

23

14 

13

25

19

2

.....

.....

.....

.....

.....

.....

X

X

1

X

1

X

1

X

1

1

1

X

1

X

1

1

1

X

X

1

3

X

X

1

1 1

1

2

1

X

1

1

0.5

.....

.....

.....

.....

.....

.....

.....

.....

X

.....

.....

X

.....

.....

.....

.....

.....

.....

X

X

X

.....

X

.....

.....

.....

X

.........

.........

.........

.........

.........

.........

Beryl.. _ .

__ do. _ .

Beryl......

Beryl......

Beryl......

Beryl

Beryl......

Beryl......

Beryl......

Beryl......

Beryl.......

.....do.....

0.06

.2

.4

.15

Tr.

Tr.

Tr.

.1

Tr.

Tr.

Tr.

Tr.

.02

.18

Tr.

Tr.

Tr.

0. 1-0. 9

0. 1-1. 1

0. 1-0. 7

0. 1-2. 1

0. 2-2. 4

0. 2-1. 7

0. 1-0. 3

0. 1-0. 7

0. 1-1. 2

0. 1-1. 4

0. 1-0. 8

0.3 x 0.5

.5-1.6
150 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch: M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite .

(pl- 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

 rock , 'Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

267

271

274

280

OO1

283

OQK

287

288

289

290

291

295

9Q7

298

OQQ

301

OflO

OfiO

304

306

Ofl7

314

315

316

Q1 0

322 

323 

324 

326

327

328 

990

332

334

336

338

339

341

344

347

QJQ

340

350 

354

Q/Jl

368

 -do-____.

- do_____-

 . _do____-

.....do......

- .do... 

..... do......

 do 

.....do... .

.....do ....

.....do . ...

 do ..

. do 

.....do .

... ..do ..

 do 

.....do. ...

 do 

 do 

.....do.......

 do -

... ..do ...

.....do.......

... ..do 

- do 

..... do -

.....do... .... 

.....do ... 

.....do....... 

.....do.......

 ..do. .

-.-- do ... .

. .do.... 

_ ..do ..

..... ..do 

.....do... .

 -do 

 ..do 

.....do ....

... ..do.... ...

 do 

 do .

 ..do... .... 

..... do 

... do 

T... ....

T.......

T. ......

T 

...do 

... do.... .

...do. :

 do 

 do 

... do 

...do 

... do... ..

... do 

 do 

...do 

... do 

...do.....

T. 

T. ......

T. ......

None _ 

T

None. 

...do.....

... do 

...do 

 do 

 do 

...do.....

...do 

T.. ___

 do 

_ do.. ... ...do.....

 do.. 

..-do 

...do 

...do -

...do.. 

None .-_

... do.....

...do .

... do 

. -.-do.. --------

 -do . 

... -do.. --------

 -do..-.- -

... -do .....

...-do. ...

.....do 

.....do -..-..

.....do ... .....

-...do ------

-.-..do ......

.....do .--..-.

 do ... 

 -do .

 -do. 

 .do ...... 

.....do. . .... .....do...........

... ..do ..... . 

.....do.... .......

...-do ... ...

 do .... 

- _do -.--... 

.....do. .- .

Discordant......

___ do . ___ .. 

Concordant in

sill.

Discordant .....do.... .......

 .do ... ... ..

Joint-controlled.

-.do - ---

.... . do ------ 

.....do ----- 

..... do ......

.. do .....

-....do.. -. ...

. ....do-.. -------

...-do....... -.

ing. 

--..do...-. --.

Tabular, branching.

 .._ do... .

... do ......

..... do... - ...

..-.do - ...

.....do ------

ing. 

..... do 

.-..do ------

.... .do ... ...

.....do ........

Tabular. ___

Irregular, branching. 

Tabular. _

ing. 

Len ticular. ...... .

.....do...... 

 -do .

.-...do ..... .-- 

..... do ..... 

 do ...... 

Len ticular, branch- ing.

.---.do -.---.-... 

.--.-do... ____ ...

Tabular, branching.

Tabular _ ____ _. 

Iventicular .....___

Irregular. ....... ~

......do. ...... 

Tabular, branch- ing.

'Pabular __ ___ ..

Tabular, branching.

Tabular . 

ing.

.-...do ------- 

-_-__do .. ... Tabular..... ......

Irregular, branching.

 -.do..... . ------- 

.... -do...-...---- ...

 -do.-...------- -

 -do...-.--. ------

..... do...... 

-. do.-..-----. .

 do 

 do.... .

 - do . ----- -- 

 . -do 

- do ... ...

.... .do.... ... 

-..-do ..............

 -do .. 

 .do ....

.....do ... -----------

..-..do... -----

.-..do -----

 .do ... 

.....do... .... . . 

 do .. . 

..... do:.. ... ... ..... .....

 ..do ----------

... ..do. 

 Homogeneous.- . 

.. _ -do... ___ -

... ..do... .... ... .... - 

.... .do... ....... .... 

Multiple, homogeneous.

.... .do... .-- ..... -

Homogeneous. . - -__ _ 

--.--do __ -. _ ____ .

.....do ..... ....

___ do .-. -- ..

----.do_. --.-----....

 do ... -

 do 

do ......do .::..::::::::::

ao

..... do.......----

..-.-do. - .-. ..

..... do ... ....... ....

--..do ...... ..... ... .,

.....ao . . . 

.....do ....... .......

M

M

M

M

M

M

M

F

F

F

M

F

M

M

M

F

M

M

F

M

M

F

M

F

F

F 

F

M 

M

M

F

F

M

F

M

M

M

F

F

MJF

M

M

M

MM

M
APPENDIX B 151

pegmatites Continued

 C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent ;Tr., less than 

f, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Percent

Size 

(in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued. 

IS ABOUT 3 TO 2 Continued

35

40

37

42

30

40

35

39

36

36

35

35

38

35

34

40

39 

39

37 

40

33

4?

25 

41

36

36

32

40

40

37

40

38

40

35

37

40

38

35

41

41

38

42

40

41

37

35

36

42

.....

45

50

50

50

55

50

55

52

50

50

50

59

50

55

58

50

52 

5?

53 

54

50

50

35 

50

53

53

53

50

.52

50

51

48

51

55

55

49

54

52

51

,50

54

50

53

51

51

50

55

49

48

.....

.....

.....

20

10

13

8

15

10

10

9

14

14

15

6

10

8

10

9 

9

10 

6

17

8

40 

8

10

11

14

10

8

9

13

9

10

8

11

8

12

8

9

8

8

7

8

12

15

9

9

- 

.....

.....

X

X

X 

JJ

X

1

1

1

1

.....

.....

.....

.....

X

.....

.....

.....

.....

JJ

X

X

JJ

1

JJ

JJ

JJ

JJ

.........

.........

.........

Beryl......

Beryl......

Beryl......

Beryl......

Beryl...... 

... ..do... ...

.....do......

Beryl......

Beryl......

Beryl...... .

Beryl......

.....do......

Beryl......

-...do 

Tr.

0.3

Tr.

.08

Tr. 

Tr.

.1

Tr.

Tr,

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0. 4-1. 3

0. 1-1. 1

0. 2-0. 4

0. 1-0. 3

0. 1-0. 2 

0. 2-0. 6

0. 2-3. 6

0. 2-0. 3

0.2x0.3

0. 1-0. 4

0. 1-0. 4

0. 2-0. 4

0.5x0.3

0. 1-0. 3
152 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmallnlzed. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pi. 5)

Wall rock

Type.and 

formation

Alteration

Pegmatite

Kelation to wall 

rock . Shape Internal structure Texture

FELDSPAB-BICH 

PBRTHTTE-PLAQIOCLASE-QUARTZ

RATIO OF PEETHITE TO PLAQIOCIASE

O71

372

Q7<<

379

380

382

383

OQ1

ana

^0*

396 

397 

4 on

403

405

406

409

410

411

412 

413 

415 

417 

418 

423

424

426

427 

431

433 

435

437

439

440 

441

442

444

447

448

450

4151

468

459

461

462

469

4711

473

475

.... .do......

..... do 

..... do......

.....do ..

..... do... 

... ..do... ...

..... do.... ..

..... do...... .

..... do 

..... do.... ... 

 do 

 do. 

..... do ...

.... .do ...

..--do ...

Granite and

schist.

..... do 

..... do 

.... do 

 do .... 

.... do 

 do 

 do 

-.--do... ....

 do......

....do......

__ do.... _. 

__ do......

"-do""- 

 do......

. _ do......

."" do"--"

"""do.".".""."."

.... do......

... .do....... 

.... do......

 do......

do

.... do......

 do......

... do 

 do 

 do 

T......

 do 

T. 

T. 

... do 

 do 

... do 

 do 

 do 

T. 

- - do

 do 

... do 

 do 

... do 

-0.0 .

-do..... 

..do 

-do 

..do .

T--..-_.

None _

..do.....

-.do __ 

 do _ __

..do 

..do 

..do. 

T...... .

-do 

-do!::::

..do..... 

..do.....

..do.....

_.do___

T 

T__-._

None....

..do 

..do.....

 do ......

.....do 

.....do .....

..... do.... ......

 do. 

 do 

 do... .... . ..

 do... .... ...

 ..do 

.. do ..... . 

 do. ... 

 ..do .....

..... do 

.. do .... .

Discordant ......

 do ....do ...... 

.... do..... ... ... 

 do... ........ 

 do ... . 

....do ........

Concordant

Discordant. 

Concordant? . - _ 

Discordant- _ _ . . .

.... do...... 

 do..... 

....do.... ......

 do._.__ ......

 _do___ _______

__ do.... , ..

.... do... 

....do...... ....

... .do...... .

 _do._. .......

Concordant

....do...... 

Concordant 

Discordant?. .

ing. 

Tabular... .-.

ing. 

. _ _do_- _ . ....

Tabular... ...

. .inging. 

Tabular........ ..

 do... ......... 

 do... ..... .... 

 do 

..... do ..... ....

.....do... ... ......

Lenticular.......

..... do ...... ..

.... do... .. ..

....do. .. _ ...

 do. .....

.... do -. ...

....do 

""do -

.... do... ... ... .... 

....do... 

 do. . 

Lenticular ......__

Irregular.. ...

 do. ...

Lenticular ________ 

Irregular.. .--.____ 

....dO......----.

....do.-... 

Irregular. .

Lenticular _______

 do.-.-- -

Irregular, branch- ing.

Irregular. .. .......

....do............

 do..... ...

__ do...- .. ....do..:.........

 do... 

.... .do... ... .... ..

.... -do... .

.... .do 

 do .... ..

-... do.... .... ......

 do ... ....

..... do... .... .... .

 do 

 do ..... .....

-...do .... ......

..... do 

Homogeneous ........ 

..... do 

.....do... ...... .

..... do ....

 do... 

....do . . ....

.... .do.. ...... 

.....do .... ...... .... - .....do. ... ......... -

.... . do ...

Multiple, banded. ______

Homogeneous. .-..-.-_..

.... do.. ......

....do. ...- 

__ do.... __ _ 

-...do.. ----- ---.

.... do... ....... ....

7 ,fWall ..... .

Zoned p

Homogeneous- _.._._.__.

... .do..... 

... .do .... -

- .do.. ___.--- ....-

Banded. 

Multiple, homogeneous..

... .do........ .... ..... .

.... do... ..........

M

M

M

M

M

F

M

M

F

F

M

F 

F

F

F

M 

F

F

F

F

F 

F 

F 

F 

. F 

F

F

F

F 

M

M 

F

F 

F 

F 

F

F

M

F

F

F

F

F

F

M

F
APPENDIX B 153

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PE OM ATITES C on tinned 

PEGMATITES Continued.

IS ABOUT 3 TO 2-Continued

36

40

4n

39 

40

34

915

41

QQ

27 

35

30

35 

35

31 

<1

3fi

3?

35

30

34

29

QC

34

3fi

34115

30 

33 

35

30

35

qe

40 

38

38

 58

40

4?

30

3fi

40

30

38

37

33

0(3

40

39

35

32

37 

32

.....

.....

0.5 

ft

.3

.5 

3

.....

-----

5

7

3

ft

.3

.....

55

50

CO

50 

48

52

50

49

Crt

48 

50

45

46 

47

43

<1

48

4fi

47

w>

44

50

44

cn

49

47

4fi

50 

48 

50

52

49

AQ

49

CO

48

39

51

48

50

52

50

52

51

53

52

CA

50

49

45

48

45 

48

.....

.....

.....

1

1

1 

1

.7

.....

.... .

1

4

1 2

3

9

.....

9

10

8

11

14

15

9

19

25 

15

25

18 

18

26

QQ

16

99

1 Q

20

20

20

20

Ifi

15

18

1Q

20 

19 

15

18

16 

Ifi

11

10

14

9

10

14

12

10

18

11

10

15

12

10

12

10

19

17 

20

.....

.....

.....

0.8

5

1 

1

6

.....

.....

,6

1

9

3

.6

.....

X

X

1

X

X

1

X

X

x

2

1

X 

X

X

1

X

1

X 

X

.....

.....

.....

60.1 

1 3

.4 

.2 

.1

.....

.....

,4

1 5

5

1

3

.....

.....

.....

X

X

.....

.....

.....

.....

.....

60.1

..... 

1

.....

.....

.....

X

X

1

X

X

X

.....

X

.........

.........

.........

0.4

.........

.........

.........

.8

1

.........

Beryl...... 

.....do-. .

Beryl......

Beryl....... 

..-.do. . .

f--.do......

Beryl...... 

.....do. ..

.....do.. .

Beryl...... 

.....do.. .

Beryl.. __

Beryl......

Beryl......

.....do.....

Beryl...... 

 .do......

Tr. 

Tr.

Tr.

0.09 

Tr.

.7

Tr. 

.04 

Tr.

.09

.08 

.05

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr. 

Tr.

0. 5 x 0. 7 

0.7x1

1.1 x 1.7

0. 6-1. 2

0. 2-3. 6

0. 2-1. 4

0. 1-0. 6

0. 1-1. 2 

0. 1-1. 6

0.2-0.7

0. 5-2. 4

0. 8-1. 7

0. 1-3. 7

0.2 x 0.3 

0.2 x 0.3
154 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTmTE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAQIOCIASK

479 

480 

481 

483 

484 

485 

490 

491 

497 

498 

499 

501 

505 

506 

507 

508 

513 

524

529 

530 

531

532 

533 

534 

542 

543 

549 

550 

551

552 

565

569

575 

577 

581

.582 

583

589 

590 

595

596 

597 

 600 

604

 609

 611

 614 

 021

.622

629 

fi31

.632 

.634 

635 

,fi3fi

Schist.... ... 

 do......

 -do.-- 

 .do---.--

- do-...--

-- do......

- do... 

Schist ___

-..-do......

-....do.-.--.

.. do..-.-.

.....do-.-..

 -do... ...

 do ...

.- do......

...-do......

--...do......

.. do.. -.

. .do......

- do......

 -_do_.-___

-....do..--..

...-do......

- do.-. 

 do... ...

.... .do......

.....do...... 

 ..do ...

- do.... ...

. __ do 

 do 

--.-do---...

 do 

 -do... ....

___ do do... 

----do......

.... .do......

.... .do......

--.-do ... ".".'."."do."."."."."."

 do....-

 .do... 

 do 

..... do ..

.... do ...

 -do 

_ None.- 

...do 

_..do ..

...do .

... do 

... do -

T_ 

T 

 do ..

...do .

... do ..

... do .

... do 

...do 

...do 

... do 

___ do 

___ do 

 do ..

 do.. 

.-.do- 

___ do .

... do ..

... do .

...do- 

...do 

...do 

... do 

...do 

... do 

...do 

T . ....

T.......

None.-.

...do ...do - 

-do 

 do 

...do 

..do 

..do .

..do ..do 

..do.....

..do -

..do 

..do 

..do.....

-doConcordant ... 

-...do...-.----.

 .. do..-.-.--..

- do......... .

 do....-. .

 do... .

 -do..-. 

 -do...- 

-. do.... -----

.-...do.. .. .-.-.-

 do-... 

Discordant. ..---

Discordant? _ ..

.. do..-. 

 .do...- 

. -..do._. -------

Concordant and 

discordant. 

Concordant __ 

... ..do.... ...

. -do... 

----do. ------

-----do_..--.----

-.-do.. ....... .

 do.-.. 

 do..-. 

..... do. ... ...

 .do..... 

Discordant and 

condordant.

Discordant.. - ...

Concordant. .

Discordant _ ..-

__ .do.... ......

.... .do.... 

.... .do ..... .

 do. .....do----------

..... do.. .

-- do......

-----do.-.---

Discordant . 

Concordant.... .

Discordant- ...

Discordant and 

concordant.

Concordant?

Discordant do......--

Concordant.. 

... .do 

.... do.... .... ...

. do... .

....do..... ...

 do 

 -do.... .

--...do.:-.-.---

 do...... ..

-....do.-....----..

 -do..... . . 

- do.. . ..-..--

 do..........

 ..do.... 

-.-. .do. -,--.... ...

-- do... ...... 

. -do..........

 do.....-. ..

- do....... .....

- do............

..... do.... ........

.-..do....... .....

 .do...... .

-....do-...- .

.....do. . .

__ .do....... ...

..... do..... ....

...-do. .......... .

-...-do .-. .

..... do... .........

 -do............

 do...- 

.- do ------ 

Lenticular... __ .

 do.:... . 

. do.... ...

.... do ...... ..

--. ..do-.. ..----- .--.-do.--. . . 

....do............

.do.--. ..-.

do Tabular .

Lenticular........

....do .... 

Irregular. .........

Irregular.... 

....do.. ...........

.... do ... 

. do ... -

Branching........

Lenticular..-.-...

 ..do-.-...- ....

- do........ 

 do...... 

..... do........... .......

 -do..... ... 

-....do......-- .......

 -do.... 

Multiple, homogeneous. - 

__ do....... . 

 do, -... . 

Multiple, homogeneous., 

-..-do-....... .......

Multiple, homogeneous.. 

Homogeneous _____

Multiple, banded _ .--.

Multiple, homogeneous.. 

...-do..... ....

Homogeneous ________

.--.do---....- -.

___ do..--.. . -..--do,... -.-.. _ ...

Multiple, homogeneous.- 

 .. do...-. ...

---.do---.--.. ... 

.....do......... .........

Banded...-.-. ...

Multiple, homogeneous.. 

 ^/Wall... .........

ZonediCore .... ....

Homogeneous.. _ ..

 .do...... ... .........

.-..do.... ---------

.--.-do..-- .....do...... ......

 do... 

Multiple, banded.- .-... Homogeneous...... .....

Banded.. .... ______

..... do..... ...... ...

 do.... ... .

Multiple, homogeneous. -

" l^dori-i ::::::::::

 .do .. ..

.-..do _----. _ .

 do.. ..... .... ...

Homogeneous. . . ___

Multiple; homogeneous.. 

 do 
APPENDIX B 155

pegmatites Continued

C, coarse, 4-12 Inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 3 TO 2 Continued "

35

on

3fi

30

36

OA

OA

30

36

36

30

39

3ft

30

33

3ft

QC

40

40

41

40

3fi

40

30

36

qc

qc

3ft

60

on

3ft

40 31

on

30

qe

qo

30

29 

08

qi

OQ

30

33

37

36 

41

40

40

qc

3*

35

<n

33

35

.....

0 4

.3 

fi

-----

6

5

.5

-- 

45

45

46

49

47

48

43

55

55

50 

52

58

53

46

5?

44

KA

50

50

50

48

5?

53

50

. 53

R<1

50

55

50

10

AK

50

48 

47

48

48

47

48

50 

50

AQ

CO

48

50

45

50 

51

CA

50

C7

57

57

fi<t

55

57

.....

0.7

4

.7 

4

.....

3

.....

,7

-----

20

25

18

20

16

16

25

9

9

20 

16

11

9

14

14

35

15

10

10

ft

1?,

1?

20

11

14

1?

30 

24

20

12 

20

20

10

20

21

20 

21

19

17

21

16

13

a

10

10

8

8

8

12

12

8

.....

0 5

.5

.....

3

"."3"

7

.5

.....

1

1

2

X

1

1

1

X

X

1

X

X

1

J£1

1

X

1

X

1

X

.....

0 1

6

.5 

1

.....

1 2

5

.3

.....

X

.....

.....

.....

.....

~o.T

-----

X

X 

X

.....

X

1

1

.....

X

X

.........

.........

.........

.........

---------

Beryl......

Beryl......

Beryl...... 

.....do.....

Beryl......

-...do.....

Beryl......

Beryl......

. .do.....

.....do.....

. .do.....

.....do.....

Beryl......

Beryl......

Beryl......

Beryl...... 

..... do.....

.....do.....

.....do......

.....do......

Beryl......

Tr.

Tr.

Tr. 

Tr.

Tr.

Tr.

Tr.

Tr.

0.03

Tr.

Tr.

Tr.

Tr.

.02

Tr.

Tr. 

Tr.

Tr.

Tr.

Tr.

Tr.

0. 1-1. 7

0.4-0.5 

0.2-0.4

0. 1-0. 6

0.4-0.0

0.2-0.7

0. 1-0. 5

0. 1-0. 6

0. 1-0. 5

0. 1-1. 2

0. 1-1. 2

0. 1-0. 8

0. 1-0. 4 

0. 1-0. 3

0.2-0.4

0. 1-0. 6

0.3 x 0.4

0. 1 x 0. 5

295165 55- -11
156 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinlzed. Texture column: F, fine, less than 1 Inch; M, medium, 1-4 inches;

0.01 percent.: Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTmTE-PLAGIOCXASE-QUARTZ

RATIO OF PEBTHITE TO PIAGIOCIASE

637

CJO

645

648

A4Q

652

656

657

658

666

fifiQ

671 

672

680

681

682

683

685

687

688

698

705

706

711

727

734

736

737

738

739

743

744

746

747 

740

750 751

752

756

759

762

m

771

773

783

787

m

795

.... .do 

 do... 

..... do 

..... do . 

 do 

 do 

.....do 

.... .do ..

 do 

..... do 

 do 

... ..do 

..... do 

.....do. ..

..... do 

 do ..

..... do .

... ..do. 

..... do 

 do 

..... do 

.....do ..

 do ..

..... do 

.... .do .. do. 

 do 

... ..do ...

 do 

..... do 

.....do... ....

..... do 

 do 

.....do... ....

.....do... ....

. do ..

..... do ..

.....do.......

.--dOdo

... ..do -

.....do.......

 do ....

 do 

~~~~"ciu~~~~~ ~~

.....do.......

 do.......

.....do.......

... do 

.._ do 

... do 

...do.. 

 do 

... do 

...do 

... do 

...do 

...do 

... do 

... do 

...do 

...do 

...do 

... do 

... do 

... do 

T. ......

None ..

...do 

...do. 

...do 

...do .

...do ~

...do 

... do 

...do 

...do..... 

 do 

... do 

...doNone 

...do 

...do ...do 

... do 

 do. 

... do 

...do 

 do 

... do 

 do 

...do.....

...do 

...do.....

Concordant _ ...

concordant.

Concordant?....

concordant.

..... do 

..... do 

Discordant. ... 

.... .do 

Concordant and

discordant.

 do .

 do..... 

 do... .... 

... ..do 

 do. .

 do 

 do .

.....do ~

.....do... ........

..... do ... ...

 do..... .... . .

 do .......

... ..do ..... . 

 do 

... ..do :...... 

.....do.... .......

..... do... .. 

.....do... ........

.....do ......

..... do ... ...

..... do 

 do 

.... .do 

.-.do.___

 do 

-....do..... ......

 do ...

Concordant.....

.....do.. 

Branching... .....

Lenticular.... _ .

Irregular. .........

Branching........

Irregular . . ....

Lenticular... .....

Irregular .__..._. 

..... do ........

Branching... .....

Lenticular.... ....

.. do .......

Irregular..... __ .

Lenticular........

... ..do ..... ...

.....do .......

 ..do... ...

... ..do 

Lenticular........

.....do ......

___ do ______

..... do... ..........

 ..do .

.. do. ...

.....do. ......

.....do ..........

.....do... ..........

.....do. ...

.....do .... ....

.....do .... . 

 do.. ..

___ do .............

.....do.'............ 

.....do..... ........

 do ..... ...

.....do.... ......... 

..... do ......

.....do ...

... ..do .....

Tabular. _____ .

Lenticular........

.....do ........

.....do........ .....

___ do.. _______

.....do.... .........

.....do .........

.....do.............

Multiple, homogeneous.

-....do...................

- do ................

Multiple, homogeneousHomogeneous. __ . __

__ do.-.. __ . ........

....-do..................

-...do ................

.. do ............... 

.....do ................

Multiple, homogeneous..

.....do ................

 -.do..... ... .......... .

-...do ..............

.-..do........... .....

Multiple, homogeneousHomogeneous. --...----.

Multiple, homogeneous..

. __ do... _________ .

... ..do ...............

.....do. ...............

Homogeneous. ....... _

Multiple, homogeneous..

 do ..............

.. do...................

..... do... .......... ......

 do...... .........

__ .do __________

Homogeneous. . ....

Multiple, homogeneous..

 do....... - ....

.....do........ ........

Homogeneous... ........

Multiple, homogeneous.

Homogeneous.

Multiple, homogeneous..

-. do.. - _ .

.....do...................

.....do ..............

z &:::::::::::

Multiple, homogeneous..

.....do....... ...... ......

-..do.................

Multiple, banded........

F

M

F

F

F

F

C

M

F

F

M

F

M

F

F

F

F

F

F

M

F 

F

F

M

F

F

F

F

F

M

F 

F

F 

M

M

M

F

F

F

F

F

F

F

F

F

M 

F

F

F

?
APPENDIX B 157

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PE QM ATITES C ontinued 

PEGMATITES Continued 

IS ABOUT 3 TO 2 Continued

^ft

qo

38 

<*fi

OQ

41

33

to

34

32

on

DO

32

36

Oft

an<in

qq

35

00

qC

43

40

32 

41

qq

qo

qc

qc

33

qi

3*

3ft

34

39

35

35 

34

qo

qft

33

'l(\

Q3

qn

31 in

28 

30

Oft

35

Oft

30

30 

34

30

-----

.....

.....

.....

.....

.....

0.3

.....

.2

48

50

52 

51

50

50

50

48

47

50

49

46

47 

47

50

40

49

47

55

50

50

55

50

55 

50

48

4fi

48

49

47 

45

45

45

46

48

45

45 

48

48

45

47

50

47

50

46 

50

48 

50

51

46

50

50

50 

47

4fl

-- 

.....

.....

.....

.....

.....

1

1

.....

1

14

18

10 

13

1?

8

17

13

19

18

16

20

20 

17

20

28

20

20

10

1?

15

12

10

13 

ft

19

22

17

16

20 

?3

20

24

20

20

20

20 

18

20

25

20

20

20

20

23 

20

24 

20

20

100

19

20

?0

20 

20

21

-----

.....

.....

.....

.....

.....

.....

0 7

4

.....

6

X

1

X

X

3

X 

X

2

1

X

X

1

1

X

X

X

X

X

-----

.....

.....

.....

.....

......

.....

0 2

5

.....

. 1

-----

X

.....

X

.....

X

X

X

-----

.....

.....

.....

.....

.....

.....

.....

,02

X

X

X

-----

.....

X

X

X

X

X

.........

.........

.........

.........

.........

.........

.........

0.7

.........

.5

Beryl......

Beryl......

.....do......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl...... 

.....do......

Beryl...... 

.....do......

.....do......

Tr.

0.1

Tr.

Tr.

Tr.

.08

Tr.

.02

Tr.

Tr. 

Tr.

Tr.

Tr. 

Tr.

Tr. 

Tr.

Tr.

0. 1-2. 0

0. 1-0. 5

0. 6 x 0. 7

0.2-0.3

0. 2-0. 6

0. 6-1. 6

1.4 

0. 3 x 0. 5

0. 5-1. 2

0. 2-1. 5 

0. 2-1. 4

0. 1-0. 2 

0.1-1

0. 1-1. 4
158 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of,

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches:

0.01 percent. Size columns

Pegmatite

{pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Eelation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTmTE-PLAGIOCLASE-QUAKTZ

RATIO OF PEBTHITE TO PLAGIOCLASE

796

797 

798 

801 

805 

806 

807

818 

819 

822 

826

827

829 

833 

836 

838 

840 

841 

843 

844

845 

846 

«50

«53 

854 

858

859 

860

80S

869 

870 

871

872

S75

880

885

887 

888 

889 

890

892 

895

896

897 

eoo

904

914

015

§17 

918 

920

Schist... ... 

.... do 

 do 

....do.......

.... do 

....do 

.... do 

 do .

....do.......

.... do ..

....do 

.....do 

.... do 

....do 

....do... ... .

....do -

.... do ..

.... do 

.... do 

 do 

.... do 

..... do......- 

 do . 

..... do 

..... do 

..... do .

 do 

.....do . 

.....do ..

-___dO__ _

 do 

.... .do .

 do 

-..-do .. .....do...... 

.....do . 

..... do..... .

----_<10 ____ -

ao . 

.....do .

.....do .

 do 

. __ do _ ...

.... .do 

____ .do _

.....do......

.....do ..

 ..ao......

None 

..do .

..do ..

..do 

..do 

..do 

..do ..

..do 

..do. .

..do -

..do 

..do 

..do 

..dp 

..do .

__do ~

..do. .

..do 

..do 

..do ..

..do 

..do . 

..do 

..do.....

... do 

...ao 

...do 

...do 

...do 

T. ____

None 

... do.... 

... do 

_ ao 

...do.... 

... do 

I do 

 do ...do....

...do 

_ do..-.

...do 

-_do .

:::ao::::

...do....

...do....

Concordant and 

discordant.

Concordant- _ . 

.... do .-.--

....do - 

... .do 

....do. -.

....do .

....do ..

 do .

.... do .

Concordant and 

discordant.

....do ...... 

.... do ......

....do -

....do ....

....do .... 

.... do .

Concordant and 

discordent.

...-do. -----

Concordant and 

discordant.

....do...... .... . 

... . do ......

....do......-. 

... ..do... ..... 

-.-do .....do __ __ .. 

.. do .--.

Discordant ..

Concordant.. ...

Discordant and

concordant.

.... .do. 

..... do 

.. __ do. _ . 

.... .do.......... 

... ..do 

Concordant 

Biscordant ..

C oncordan t, . _ - _

.....do..........

. do. .

:::;:ao----: 

.....do..........

.....do.. .

Lenticular... .....

....do .

Tabular.. _ . .....

Lenticular... .....

....do. ...

....do.... .........

....do ...... ...

.... do ... ......

....do ... ...

.... do ........

.... do ...... .

.... do ........

....do ....

....do ... 

 do .........

....do ......

....do ........

....do .... ...

.... do .....

....do 

.-.do. _ . .

.-..do ...-...-.

..... do... ......

 do ........

.... .do ..... ...

Lenticular........

Irregular . .....

Irregular... _ .... Lenticular........

.... -do... .........

..... do . 

..... do .......

do-

.... .do......... ... 

..... do .......

Lenticular _____ __

..-..do. 

Trrpgiilar

Lenticular--. _._. .....do.. .....

... ..do ...

 .do............

.... .do... ....... .

....do ...... ..... .... .

.... do.. . 

Multiple, homogeneous.. 

Homogeneous ___ . _

Multiple, homogeneous. . 

 do ... ...... ...

Homogeneous. ..........

Multiple, homogeneousHomogeneous. ____ ..

 ..do- .. __ .. _ ..

ZonedfflJS------

Multiple, homogeneous..

Multiple, homogeneous..

Multiple, homogeneous..

Multiple, homogeneous- . 

 do 

-. .do ____ ......

. _ .do..........- ......

-...do .

 do .... .. .....do ....... ....... .

ZonedlgSJ------

Multiple, homogeneous..

i--do^-iy.r.-----

..... .do .... . -

.....do...........- -

Multiple, homogeneous..

Multiple, homogeneous- Homogeneous- - - .....do.. . 

Multiple, homogeneous.

Homogeneous, .........

Homogeneous. . ......

.....do.. ... ... ...

 dO ......

 do ....... 

Multiple, homogeneous..

Multiple, ioniogeneoiis..

 -do _ _ _____

F

F 

F 

F 

F 

F

F

F 

F 

F 

M 

M 

C 

F 

F 

F 

F 

F 

F 

F 

F

.F 

M 

F

F

M 

F 

F 

M 

M 

F

F

F 

M 

M

M

F 

F 

M 

F

M

M

F

F

F

F

M

F

F 

F

F

F

F
APPENDIX B 159

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Percent

Size 

(in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 3 TO 2 Continued

29

33

29

30

34

33

Q^

33

34

29

31

30

35

32

40

28

32

32

39

39

39

39

40

40

38

40

33

37

34

3fi

38

33

40

38

40

40

40

30

34

37

34

38

38

42

38 

39

31

30

30

33

32

34

0.6

.6

3

5

- 

50

47

50

50

47

50

47

48

48

43

50

40

48

50

49

49

55

55

51

50

50

49

48

48

53

49

50

50

55

50

48

55

49

47

50

52

49

5fi

50

53

55

52

52

50

52 

50

47

50

53

48

50

47

3

1

05

.5

- 

21

20

21

20

19

1fi

19

19

18

24

17

30

100 

17

18

11

22

12

12

10

11

11

12

12

12

9

10

12

99

13

11

14

14

12

11

14

10

8

11

14

Ifi -10

11

10

10

8

10 

11

21

20

17

18

18

19

2

6

0 7

3

.....

1

4

2

X

1

1

X

1

5

1

X

1

1

X

0.8

-----

3

1

.....

X 0.1

.1

.....

X

X

1

X

0.6

1

.........

Beryl.......

/Beryl......

\Apatite....

jBeryl......

Beryl......

Beryl.. _ .

Beryl......

Tr.

Tr.

Tr.

0.15

Tr.

Tr.

Tr.

Tr.

0. 3-1. 4

0. 1-1. 2

0. 1-0. 7

0.3-2.4

0.1 x 0.2

0.5x0.9

0.7x1.2
160 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinlzed. Texture column: F, fine, less than 1 Inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmat itite*

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTHTTE-PLAGIOCLASE-QUARTZ

RATIO OP PERTHITE TO P1AOIOCIASE

921 

923 

929 

930 

931 

933 

938

939

940 

942 

943 

944 

946 

948 

950 

952 

954 

955 

957 

958 

959 

960 

961 

962 

963 

965 

966 

968 

969 

970 

971 

972 

974 

978 

979 

084 985 

986

987

989 

991

992

993

995 

996

1001 

1006

1007 

1012

1016

1017 

1021 

1024

1032 

1O34

1040

1045 

1046

Schist .

.....do.......

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Concordant. .

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..... do ... .

.....do 

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 do ........

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Lenticular........

. do ........

 .do ........

 do .... ...

..... do .......

.-..do ...... .

.... . do ... .. 

Tabular. 

.....do....... ......

.. do .....

Lenticular..... . 

.....do . -.-.... 

.....do . ........

 do 

..... do. ... . 

.....do ... ..... . 

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Lenticular....... .

. do ........

Lenticular...... 

..... do ...

 do . 

.....do ........

.....do ........

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.....do ..... .

.. do --------

. __ do .........

..-do..' .......

Irregular _ __ _

Lenticular....... .

.....do.............

"Tabular! ! !-

Lenticular........

Multiple, homogeneousMultiple, homogeneous. . 

__ do. ........... 

.....do ..............

^MK-.::::::::::::

--.do .-.--- -------

Multiple, homogeneous. . 

.--do- .. . ........ -..

.....do .... ............

.. do .... 

Multiple, homogeneous.. 

.....do ..............

.....do . . ........ 

..... do ............... .

. do ......

Homogeneous- _____

. do . .- .

Multiple, homogeneous. .

.....do ... .--

. do .- ....

. _ -do-... ...- ....... 

Multiple, homogeneous. . 

.. _ do.. _________

. .do . 

..... do ... -- . 

..... do ....... .... .... 

Homogeneous ..... . ..

Multiple, homogeneous. . 

.-...do ..... . -.

-. do ..............

Multiple, homogeneous -.

.....do 

_-__ -do__ _-_____- __-_-

Multiple, homogeneous. -

Banded....... - 

.Multiple, homogeneous. .

Homogeneous.. 

.. do .. . ....-

Multiple banded... __.._ 

Homogeneous ------_--.. a«i(gj-"--

..... do . -- ~

....do. ...........

Multiple, homogeneous Homogeneous

..... do. ..... ........

.....do........ ...........

F 

F 

F 

M 

F 

F 

F 

F 

M 

F 

M 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

M

F 

F 

F 

F 

F 

F

r

F 

F 

F 

F

F

F 

F 

F 

F 

F

r

MF

F 

F

F 

F 

F

M

M 

F 

F

F 

r

F 

F
APPENDIX B 161

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent, (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 8 TO 2 Continued

35

33

3032

35

30

33

30

Tr

31

25

32

31

31

31

29

30

32

30

32

34

33

31

31

32

32

25

35

33

33

32

36

34

32 

30

30

31

30

30

30

28

32

32

32

32

33

33

3fi

36

40

34

55 

25

34

31

36

39

35

30

34

0 4

4

.6

.....

1

1

.4 

.6

45

47

50

50

44

50

47

45

Tr

49 

40

48

49

53

48

50

50

48

50

48

47

47

48

48

48

48

41

45

48

48

48

44

48

48 

51

50

49

50

50

50

51

48

48

49

52

46

49

47

46

50

55

34

57

48

51

53

51

50

49

47

0 9

7

.7

.....

3

.4

1 

4

19

20

20

18

19

20

20

25

100

20 

35

20

m

16

21

21

20

20

20

20

19

?0

21

21

20

20

32

20

19

19

20

20

18

20 

19

20

20

20

20

20

20

20

20

19

16

20

18

17

17

10

11

11 

18

18

18

11

10

15

21

18

0 7

,6

3

.....

.3

,3

1 

3

1

2

Tr

x

X

X

2

X

J£

1

1

X

1

03

.....

.....

.1

.1

.5 

1

X

x

j£

-----

.....

.....

.....

X

X

X

0.6

.........

.........

.........

Beryl......

Beryl......

Beryl... ... 

. __ do......

Beryl. __ .

Beryl......

Beryl......

Beryl......

Beryl...... 

.....do......

Tr.

Tr.

Tr. 

.....do...

Tr.

Tr.

Tr.

Tr.

Tr. 

Tr.

0.3 x 0.5

0. 2-1. 4

0.2-0.5 

1. 2-1. 7

0. 2-1. 2

0. 5-1. 2

0. 4-1. 8

0. 2-1. 7

0.3x0.7 

1.6x1.9
162 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 Inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTHITE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

1048 

1050

1051 

1062 

1067

1068

1069 

1071 

1074 

1077 

1078 

1079 

1080 

1081 

1083 

1084 

1085 

1086 

1087 

1088 

1091 

1092 

1093 

1094

1095 

1098 

1102 

1104 

1107 

1113 

1117 

1118 

1119

1123

1125 

1126

1129 

1131

1133

1134

1135 1138

1140

1141

1144

1147

1148

1150

1154

1155 

1158

116O

1162 

1166 

1180

1182a

.....do. ...

.....do . ...

.- do .... 

.....do ....

.--.do -.

.....do. ...

..... do ....

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....-do 

.....do ..

.. do 

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.....do .. 

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Concordant.. ... 

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.....do..... -

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.....do... 

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.....do.. -

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discordant. 

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 Tabular. ..... _

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T onfipnlftr

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.-.-do -.-- - 

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. do ..

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. .do -------------- 

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 do 

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... ..do ...

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-.--.do . . . ---------

..... do .... ... ........ 

. do 

___ do. . __ . ___ ...

- .do ----- 

 do .... 

Multiple, homogeneous. .

Homogeneous -------

.... .do ...... 

 .do ...... 

.....do ------- 

_ . .do -

Multiple, homogeneous. ,

. do. 

_ -.do..... __ . _____ . 

Multiple, homogeneous.. .do..... ...... -

Multiple, homogeneous 

.... .do.... 

Homogeneous. ... _

.... .do..... -

.....do....- ------

..... do..... ....... -

.....do ..............

.... . do.... 

..... do.... .

F 

M

F 

F 

F 

M 

M 

F 

F 

F 

F 

F 

F 

F 

F 

M 

F 

M F - 

F 

F 

F 

F 

F

F 

F 

F 

F 

F 

M 

F 

M 

F 

F 

F F F

F

M

F 

F 

F

MF

F

F

F 

K

F

F 

F

F 

F

F

F 

M

F
APPENDIX B 163

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 3 TO 2 Continued

34

35

30

30

30

30

Tr2s

25

35

31

30

32

3?,

33

30

30

35

35

30

30

35

33

31

?8

34

34

29

30

40

30

34

30

32

34

3?

30

34

34 

30

3?

34

31

34

29

' 33 

35

30

30

34

31

32

32 

31

3fi

35

30

0.7

7

.....

.....

.....

50

4fi

.50

50

50

49

X

51

40

45

50

.50

52

50

47

50

.50

47

47

50

47

4fi

49

49

,50

47

4ft

48

53

48

50

44

5?

51

49

50

50

45

45 

52

48

46

48

47

.50

49 

45

50

50

4ft

47

46

50 

49

52

55

.56

?,

2

.....

.....

.....

1ft

19

20

20

20

21

100

?1

35

19

19

20

16

17

20

20

20

18

18

20

23

18

18

20

22

19

19

22

17

12

20

21

18

17

17

18

20

19

19 

18

20

20

21

19

21

18 

20

20

20

20

22

22

18 

20

12

10

14

2

3

.....

.....

_---.

x

Tr

1

1

x

1

1

1

2

2

x

x

j£

X 

X

x

X

1

.....

-----

X

' X

^

x

X

J£

-----

0 3

.....

::::

]£

X

X

JJ

X

1.3

.........

.........

---------

.....do......

Beryl......

Beryl. ......

Beryl......

Beryl.......

Beryl......

/Beryl. ..... 

\Chrysoberyl 

Beryl.... ..

Tr.

Tr.

Tr.

0.02

Tr.

Tr.

Tr.

Tr.

.25

Tr.

Tr.

Tr.

Tr.

Tr. 

Tr. 

.08

*. Tr Tr<

0. 7-1. 4

1.-2.4

0. 2-5. 4

0. 3-1. 2

0. 6 x 0. 9

0.2-0.6

0.1-1.4

0. 1-2. 9

0.2-0.7

0. 6-2. 4

0. 1-0. 5

0. 1-0. 6

0.2-0.6 

0. 1-0. 5 

0. 1-2. 5
Mineralogy of

[Alteration column: T, tourmalinlzed. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTmTE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

1182c

1184 

1187

1190

1191 

1193

1195 

1196

1197

1 1QQ

1200

1206 

1207 

1210

1211

1214

1216

1217 

1220 

1221

1227 

1228 

1230

1231

19^9

1236

19T7

123O

1240

1243 

1944

1261a

1 OCO

10CO

1264

1266

1267

1269

1270

1271

10(31

100C

1207

Schist ..

 do... 

..... do 

 do......

. .do.- 

.---do--....

 -do -. 

 -do ..

. do... 

. do 

.. do......

 .do....- 

 do...... 

 do... 

.. do... 

 .do... 

- do... 

 .do. 

 do.. .. 

----do......

 -do..- .do......

 -do-----.

 -do 

 do......

 do.. 

 -do 

 -do... 

.....do......

Schist 

 do... ....

.....do......

- -- do- -- -.do... 

.... .do......

-.--do.---.

. .do- 

. do.- 

.....do......

Oranito-.- _

... do -

T 

T........

T ... 

T...... .

T.... ... 

T -

T 

...do..... 

 do... - 

... do ..

...do ..

...do ..

... do .

 do 

 do 

 do 

 do. .

...do.....

 do 

 do 

... do 

-do 

 do 

-.do. 

...do . 

...do.....

T 

NOD.6

...do.....

... do 

... do 

 do 

_ do 

... do -

...do.....

...do 

... -do.... 

Discordant 

..... do...... 

 ..do-.- ---- 

 do... 

 .do....... 

concordant.

 do.... -

 do..... 

 ..do... 

 ..do.... 

 .do-... 

-..-do..... -

 do.... 

 -do-... 

Discordant------ 

Concordant-----

-.--do----------

..... do...... ....

- . do... ------

 ..do .. .

 do.. 

 -do.... 

 do.-.. 

 .do.... 

...-do... 

.... .do. 

 .0:0-.-..-- 

.... .do.... ...

.. do.-...--..

___ do----.- . 

Concordant. 

Tabular... ........

.. do.... 

Lenticular.. ...... .

.... .do.. ..........

 do. 

.---do-... 

-- do...- . 

Branching.... ..

----.do... --.

 do... - 

 -do 

----do-... --.

Tabular - .-.

. do...-. --.

. do.... . 

 do.... 

 do.... -

.--..do. ------ 

 do.... 

 -do. . .......

 -do... -----

-- do.....-. .

 .dO ........

 do.-.. 

 - do... ----- 

-- do. -------- 

-- do.... .

Tabular __ .__,- _.

Tabular .

 do.. 

__ .do __ ... .... .....do...... 

 do...- 

Lenticular. __._- 

Lenticular........

Lenticular, branch- ing.

Homogeneous. __ .....

 . do.... ... 

.....do....... ....

Multiple, homogeneous. .

 .do.... 

.---do....- --...-

 do.. 

.---.do... .

 do.... 

 -do.... ... 

 do...-. -

 .do... 

 . do.... 

 do 

Homogeneous. -..-......

 .do...-- .. ...... 

 do... ... 

Multiple, homogeneous..

 .do-. ! -I- 

 .do..... 

 do.... . ........ .----do..--. __ . _ -..--

----do------ .. . Multiple, homogeneousMultiple, noraogeneous 

-.-..do. -..------------.-

-..-.do-.--- _ . --..-

 do.... 

Multiple, homogeneous- .

 - ao ----..------.-----

Multiple, homogeneous..

-----do. .- ---------------

 do.... -...---

.... .do...... ......

.....do .......... ...

F

F 

F

F

F

F

F 

F

F

F

F 

F 

F

F

F

F

F 

F

F

F 

F

F

F

F

F

F

F

F 

F 

F

F

F

F

F

F

F

F

F

F

7

8 

12

.....do......

.....do......

 do... 

.--..do.. .-

...do.....

... do 

 do... ..

_ do- ...

 do...- 

Concordant and

discordant.

Tabular .. -

Irregular.. .--.. 

-.-.do.. -------

RATIO OF a^ERTHI

Homogeneous... ........

Multiple, homogeneous.- 

--.-.do __ --------------

TE TO

M

F

M

M 

F
APPENDIX B 165

pegmatites Continued

O, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

f, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Percent

Size 

(in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 3 TO 2 Continued

36

3?

3ft

34

3?

30

34

32

34

34

33

35

36

32

38

4?

3?

3?

33

3?

31

3R

33

34

3?

34

3?

3?

34

30 

31

33

38

3?

33

33

30

32

30

3?

31

36

3?!

3?

31

 -

44

49

45

4fi

48

fiO

47

49

48

48

49

45

46

50

55

50

49

50

47

48

51

45

49

48

48

48

48

48

4647' 

45

47

50

48

47

46

48

48

44

51

50

50

48

48

50

.....

?0

19

1920202020

19

18

18

18

20

18

17

17

8

19

182020

18

19

18

18

20

18

2020

20

23 

24

90

12

20

20

?,1 22?o

26

17

19

14

20

20

19

.....

X

X

jj

X

X

X

X 

X

X

X

.....

X

X

----- .....

X

x

X

X

J£

.........

Beryl......

Beryl......

.....do.....

Beryl......

Beryl......

Beryl. .... .

Beryl. .....

Beryl.. ....

.....do.....

Beryl......

/Beryl......

\Biotite-- 

Beryl. .....

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0.3-1.4

0. 3-1. 2

0. 1-2. 7

0.5-12

0. 4-1. 2

0.2-0.6

1. 2-1. 9

0.4 x 0.9

0.2-1.4

0. 7-4. 9

0. 1-2. 7

0.8-2.9

0.2-0.5

0.3-1.3

0. 1-0. 5

0. 2-1. 2

0.3 x 0.7

0.4-4.2

PIAOIOCIASE IS ABOUT 2 TO 1

25 

30 

29 

32 

25

0.2

! 55

GO 

65

60

50

0.4

19

10 

6'8

23

0.3 X

2

0.2 ..... ..... ..... ......... Beryl...... Tr. 0.5 x 1.1
166 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegma1 tite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

17

20 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

36 

39 

44 

65

92 

97

98 

99

105 

135 

136 

138

139 

141

142 

143 

144 

150

153

155

162

IBS 

166 

171

175 

177

183 

187

188 

189 

196

202

204

2O9

210 

211 

212 

232 

237

Schist. 

. do -

.....do . 

.....do ..

..-..do. ..

 -do... ... - 

.....do.. .. 

.....do .. 

.....do .. 

..... do .. 

.....do ..

.....do . 

...-do -. 

.. do ....

.....do ..

.....do.. ..

Granite and 

schist.

 do 

..-..do .. 

 -do 

 do 

..... do ..

.-...do ... .

.--..do .. 

 do 

Schist and 

granite. 

Granite.. 

 ..do 

...-do .. 

... -do... .

Schist. ------

Granite 

Schist 

... ..do 

..... do 

.....do 

Granite --- 

 do 

Schist ___

 do 

 . .do ..

 -do -

 _do 

.....do .... 

 .. do. . 

 do 

...do ..

 do... - 

 do -

 do -

 do - 

 do 

 do 

 do - 

 do 

 do 

... do 

 do 

... do 

... do -

... do -

T. ......

None 

 do 

...do... .. 

... do 

 do 

... do -

 do -

 do - 

 do 

...do 

...do. .

... do - 

... do 

... do 

 do .

...do.....

 do 

...do 

... do 

... do 

...do 

_ do 

..-do.. ...do 

...do 

 do--

 do 

...do 

...do .. 

...doConcordant and 

discordant. 

Concordant.- . 

 ..do ----- 

 -do . 

-.-..do ----

. do 

.....do ------- 

--...do ..... 

-.--do ----- 

-....do ----- 

-.-..do .---

 do - 

.---do ----- 

--...do -----

.-...do ..

-....do ... --.-

.- do -------

Concordant in 

sill. 

Concordant and 

discordant. 

Concordant in 

still.

 do 

- do -----

-- do -- 

 do ... 

Concordant ... ..

Discordant- -- -

-.... do ------- 

--... do. 

.....do 

--.-.do ------ .....do -.

-.-..do----.----.

Concordant and 

discordant.

Discordant... ... 

Concordant.- 

Concordant in sill

Discordant. .-. Concordant.....

 do ... 

. __ do.. _ _ ___

..... do ....

 -do... ..... ... .

.. do ....--.

 ..do 

..... do ......

 do 

.--..do -------

---..do... ... ---...

 do -. - 

- do - -.. 

 .do 

----do --. 

.....do --- -. . 

 -do .--. ..

-...do ... 

 ..do ----- 

 ..do 

--...do -------

 . -do... 

Lenticular, 

branching.

Lenticular, 

branching.

T^flTiiilnr

.... . do .... .

-- do ------

Tabular, branching. 

Lenticular, 

branching.

......do......... ...

-. do .. . ------

.....do... ----- 

 -do .... .-.-do ----.. .....do.....- 

 do. . .

Lenticular. ...._.._ 

 ,dO 

Irregular. -... 

Lenticular.... ....

-. do ___ ----

.....do --------

..... do..... ....

... ..do. 

. __ do --. ---

 .do ....... .

 .do -

.--..do --------- 

 do . 

.....do ------

..-..do .... ... ....... .

 -do- .

Multiple, homogeneous.. 

---..do... ------- ___ .

-.-do . .. 

-...do -- 

-...do ----- -...

.. do.. ... -------- 

--..do . .... 

--...do -------.---...

. do -- ... .....

.. _ do.. - __ ... __ .

-.-do ------------

----do ------

...-.do .......... 

 do .

-. do ---------

 do - .

.....do .... 

 .do ... ...... .

.. do 

 --do. __ ---- ___ ---. 

..... do -- -. .

.....do.....--- ------

.... .do ..... ......

..... do ----------- 

 do 

 do . 

 do . 

. __ do ..

... ..do ------------ 

... do 

Homogeneous. -.---._...

Multiple, homogeneous. . 

-...-do ---------- ... Banded.. -------....---.

Multiple, homogeneousMultiple, homogeneous.- 

.....fl0.....» 

Multiple, homogeneous.. Multiple, DandeQ ....

Homogeneous _____

-----do ___ -------.... -..do . .::

 ..do ... 

F

M 

M 

M 

M 

M 

M 

M 

M 

M 

F 

F 

F 

F 

M 

F 

F

F 

F

F 

F

F 

M 

M

M

M 

F

M 

M 

M 

M 

M

M

M 

F

F 

M

M 

MF

F

F

F

M

M

M

M 

F 

F

F

?
APPENDIX B 167

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Per- Size 

cent (in.)

Muscovite

Percent

Size 

(in.)

Garnet

Percent

Size 

(in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 2 TO 1 Continued

32

80

30

30

30

30 

30

30

30

30

30

30

30

30

20

27 

22

25

25

9>i

?a2520

20

20

90

27

25

18

23

22

20

^n

25

25

24

9";

20

30

28

9^

?,8

25 <tn

oc

30

32

21

21

25 

30

.....

0 3

-----

2

 ..

.4

.....

58

00

00fin

fin

fiO

60 

fiO

fiO

fiO

fiO

00

fiO

fiO

55

05

53

fi8

00

fiO

00

00

05

00

75

75

74

00

55

75

00

05

00

00

05

00

00

60

00

00

00

KR

00

55 

00

55

55

00

70

70

58 

51

---

0.6

.6

-----

.....

8

- 

10

10

10

10

10

10 

10

10

10

10

10

10

15

15

20 

10

15

15

in

12

10

20

5

5

0

13

20

7

17

13

10

10

10

15

15

19

10

1?,

19

1 9

19 

10

in

15

8

9

9

17

19

.....

0.4

-----

.3

.....

,0

.....

x

jj

X

X

JJ

X

X

1

1

1

1

1

X 

X

.....

0.2

.1

.....

,1

.....

2

.....

.....

X

.....

-----

-----

-----

.....

.....

.....

X

X

.....

X

.........

.........

.........

.........

Beryl......

Beryl......

Beryl.--...

-. _ do -.

Beryl......

Beryl......

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0.2-06

0. 2-1. 2

0. 2-0. 6

0. 5-1. 1

0. 2-1. 9

0. 3-0. 5
168 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAB-BICH 

PERTHITB-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASB

252 

258 

259 

263

264 

275

276 

277 

279 

282

286 

305

317 

355

359 

362 

374

375 

376 

377 

378

381 

399 

401 

402

414 

416 

425

429

430

432 

434 

443 

449

467 

487 

488 

494

514 

B40

556 

574

694

599

602 

603

Schist _ ... 

 do.. 

.....do.... ... 

Granite. ....

 . .do. ... 

 .do 

 do 

... -do... .... 

.....do.......

.. do -

.... .do... .... 

 .do 

Schist... 

.....do... ....

 do 

 do. 

.....do .

 do 

.....do 

.....do.... ...

.....do.......

.....do ....

 do .

..... do... .....do ...

__ -.do .... ...

..... ao .

.....do .. 

... ..do 

.. do ..

 do- 

..... do 

.....do ...

-.-do. .. do 

.-.dpgraiiitu. Schist.......

..... do.......

.....do 

..... do 

..-.doNone . . . 

... do 

 do 

T ...

None 

... do 

...do 

T 

 doNone

 do 

T ...

None 

... do .

...do 

... do 

 do .

... do .. 

...do .

... do 

...do 

... do .

... do 

... do 

...do 

...do _ ..

 do. .

... do 

...do :

T

T. ......

None 

...do.....

...do.....

...do 

None 

...do.....

...do, ..

... do 

... do .

... ..do... ..... 

... ..do..... ... 

 .do 

 do 

... ..do 

..... do.... . 

 ..do ..... . 

.....do .... 

.... ..do ..... 

.. do. 

... ..do ....

Concordant and 

discordant.

Joint-controlled.

Joint-controlled . 

--...do. -.--.

--...do ..... 

Joint-controlled .

.....do ....... 

Discordant ......

Concordant? ... . 

..... do ...

Concordant

 ..dO ....

.. do .

Discordant _ ... 

___ do. ..........

.....do... ....... .

.....do .......

___ do .... 

 ..do____

Concordant.. ...

.....do -.. . .

.....do .......

.....do... ........

.....do .......

.....do ..... - 

.....do 

--..-do ......

.....do .......

Discordant ...

Lenticular... .....

.....do... ........ . . 

 do ........ 

Irregular, branching. 

Tabular ... 

Tabular, branching. 

 do .... . 

.....do ........

Tabular, branching. 

Len ticular .-..-.-- 

Tabular, branching. . Lenticular, 

branching. 

Tabular, branching. 

..... do ... 

Tabular... ----

Tabular, branching. 

__ do.. __ .... ...

 ..do...... .......

Tabular .. __ . 

Tabular, branching. 

..... do. .... .... 

..... do . .....

Lenticular........

 do ....

__ _do .....do ... :

Tabular..... 

T Atiti/»lllQP

Irregular, branching.

__ do... _____

T DTitipnlcir

__ -do .........

Irregular... --

. _ .do ....... .

.....do ......... 

.....do 

.....do .... . ...

..... do.... ....... ..

..... do ... 

Tabular..... ......

Lenticular..-----. Tabular...... 

Lenticular..... ...

Multiple, homogeneous..

 .do.... _ . 

 ..do ..... .... ....

.....do ..... ...... ...

 . .do .... ....... ... .

-...do ..... .... ..... 

.....do..... 

.....do .... 

 -do - 

 ..do ... ... .. 

 . .do .

Homogeneous. ... 

..... do 

 do ...

.... .do 

.....do ....... . 

.... . do ....... ...

.....do ... .... ...

..... do ... .... .... ... 

..... do ... . .

.... .do ... ............ 

... ..do . ... ... .....do............ -

.. do .... ..... ..... 

.....do ... .... ...

.. __ CO ... ....

.....do .... - 

Multiple, banded.... 

Multiple, homogeneous..

..... do .... . 

.....do... ....... ...... 

Z°ned(S!e--~----~-

Multiple, homogeneousHomogeneous __ .

." do I I 

.....do ............

__ _do _ .

.....do .... ...

.....do ...............

;::;:5o i;~~^-~."

-....do .. .............. Banded. ... ---

Homogeneous. ..........

M

F 

F 

M

M 

M

M 

M 

M 

M

M 

M

F 

F

M 

M 

M

M

M 

M

M

M 

M 

M 

M

F

F

M 

P

F

F 

F

M 

o

F

F

F F

F

F

M

F

M

F

3=~

F

F

F

F
APPENDIX B 169

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent, Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued 

IS ABOUT 2 TO 1 Continued

?ft

91

QO

OK

oe

18

20

18

15 

32

9fi

26

25

qq

oe

21<in

99

25

25 

?,5

97

20 

20

15

20

1 Oft

OR

30

30

30

on

5

qo

30

25 

3090

35

15 

27

30

30

1Q

24

OK

15

15

25

.....

-----

.....

.....

0.4

.....

.....

.....

.2

56

60

55

55

55

70

65

70

65 

fiO

< >«

55

63

56

4fi

55

6?

65

60 

63

Rn

58 

50

15

60

56

55

65

53

53

58

75 

50

6?,

50 

55

55

57

35 

48

fi(\

58

55

56

50

65

65 

50

.....

.....

.....

0 7

.....

.....

.....

.4

19

15

15

20

20

1?,

15

11

20

8

1?,

18

12

11

12

33

15

15

10

15 

12

1?,

22 

30

68

?0

16

20

14

16

16

13

20 

12

8

25 

15

1f>

8

50 

25

10

12

OK

20

25

20

20 

25

.....

-----

.....

0 5

.....

.....

.....

.4

1

X

X

1

X

?,

1

1

1

X

X

X

X

.....

.....

.....

0 3

.....

.....

.....

.1

.....

.....

.....

.....

.....

.....

.....

-----

.....

.....

.....

.....

.....

.....

X

1

X 

X

1

X

1

X

X

X

X

X

X

X

X

.....

1

.....

X

1

.....

.........

.........

.........

.........

.........

.........

Beryl......

.....do......

.....do......

Beryl......

Beryl......

Beryl......

Beryl......

Beryl.. ....

Beryl...... 

__ do ......

.....do......

Beryl.. ....

Beryl.......

Beryl...... 

__ do.....

.....do......

Beryl.. ....

0.05

Tr.

Tr.

.06

.2

Tr.

Tr.

.1

.16 

1.7

.5

Tr.

Tr.

Tr.

.18 

Tr.

Tr.

Tr.

Tr.

0. 1-2. 8

0. 3-1. 3

0.3-1.3

0. 2-1. 3

0.1-1.9

0. 6-1. 2

0.1 x 0.6

0.9-4.8

0. 2-5. 4

2. 4 x 3. 6

0. 1-0. 8

0. 1-1. 2 

0. 1-0. 4

0.2-0.8

0.2-0.7
170 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PLiAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

605 

607 

608 

613 

638 

639

642

663 

667 

668 

670 

673

684 

691 

694 

714

748

753 

754 

755 

757 

758 

764 

765

766

768 

769 

772

774

776

777

778 

779

781

782 

784 

785

790 

791 

792 

793 

794 

799 

800 

802

803 

804 

808 

809 

810 

811 

812 

813

.....do. ...

.....do.....-'

.....do ....

..... do 

 do 

..... do. 

 do . 

... .do .

 do 

..... do 

 .do 

.....do ..

 do 

 .do 

 do 

 do 

 do 

 do 

..... do - 

 do 

..... do 

.... .do 

..... do .

..... do 

... -do ..

. _ .do ..

 .do 

 do... ....

 do 

.... -do 

.. do 

___ do ...

 do 

.....do... 

..... do - 

.... .do -

 . do -

 .do 

... -do - 

.. do 

.....do.. --

..... do 

..... do... ... .

.....do 

 .do.... ... 

.... .do .. do .- 

.... .do..... ..

- do ... 

..... do... 

..... do ...

... do... ..

 do -

...do 

... do... -

___ do... -

 do -

...do ..

... do. .

...do 

 do. .

T..---..

... do 

... do ..

... do ..

... do ..

...do. .

... do 

... do. . 

...do 

...do .. 

... do 

... do 

... do 

 do ..

 do 

...do 

... do 

...do 

... do .

.-do. .

.-.do.. 

T. 

None. ...

...do 

...do . 

... do 

... do 

...do 

...do 

...do . 

...do 

...do 

...do 

...do 

 do 

... do 

 do..... 

 do 

 doConcordant?.... 

Concordant .....

..... do. ....--

.....do. -....

......do ... .-.

..... do ... -- 

Discordant and 

concordant. 

Concordant ..... 

 do .....

...-.do ... ...

..... do ... 

.--..do .-..-.

. .do. . 

.. do ... - -

...-do ------ 

 ..do ... .. 

.. do- ----- 

..... do -

.. do -..-.

..... do ----- 

--...do -----

... ..do. 

 do 

 do ..

..... do ..... - 

..... do .....

-- do - 

Concordant?.. -. 

Concordant.-...

.....do...........

.... .do... 

 do 

.. do -----

.... .do.... 

-.--do .......

..... do - 

...... do ... ....

---..do.... ...

.....do....... ....

.... .do .... 

.....do - --. 

.....do ------

 do ...... 

-...do ...... 

 do .....

.-...do ... .....

..... do 

..... do .....

 .do 

..... do... .. 

.... .do. ...

.. do .... .

 do .

...-do . 

-...do ...----

. do -....--

 .do . 

.....do _._ -

 ..do ..---- 

..... do...... 

.... .do 

 do -.-.. 

 do ... 

.. do ..... ...

__ .do. - ......

Lenticular --------

Tabular ______

.... .do 

.... do 

Lenticular, 

branching.

Tormlsir

..... do ......

Lenticular... 

.... .do ------

... -do... -------

Lenticular. ------- 

Tabular... . ----- -

Lenticular.. ... ...

.. do -------

"Tabular!."."."--^

....-do ------ .....do ------

..... do ... .....

 do - 

..... do 

 ..do 

 -do ... 

 do... ... ...

ZonedfgJl---- 

..... do .

 ..do .

 ..do 

 ..do -. .- _._.

.....do ------------

Multiple, homogeneous. . 

-...do - .-.

--'..do 

~ ,/Wall - ...

Multiple homogeneous . . 

-...-do ------ ----- 

.... .do ... 

 do.. 

Homogeneous. ----------

Multiple, homogeneous 

(

Wall oSv:r.:::::::::

zonedK---;::::;:::::

..... do.... ..... ....... 

... -do... ..... ... .....

Zoned/ WaJ1 - --

ZonedK------

Multiple, homogeneous. .

.... .do.. 

Multiple, homogeneousHomogeneous. - - - - ...

Multiple, homogeneous.. 

__ .do .--- ....-..

.....do __ --------- __ -

..... do 

.... .do... ... ... .... ...

 do- ___ _- -- . Multiple, homogeneous..

.....do -- - .. 

__ .do..... . .............

.....do ... -

Multiple, homogeneous.. 

Homogeneous. . . ___ ..

F 

F 

F 

F 

F 

F 

F 

M 

F 

F 

F 

M 

M

F 

F 

M 

F 

F 

M 

F 

F 

F 

F 

F 

F 

F 

F 

M 

F 

F F 

F 

M 

F 

F 

F

MM 

M

M 

F 

F

F 

F 

F 

F 

F 

F 

F 

F

F 

F 

F

F

F 

M 

F

M 

F
APPENDIX B 171

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Pcrthitc

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(in.)

GarnetPercent

Size 

(in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES-Contiimed 

IS ABOUT 2 TO 1 Continued

262628

30

30

30

64

30 

27

25

27

20

21

31

32

26

27

27

22

28 

26

26

27

27

25

26

23

25

26

20

22

27

20 

x

20

28

20

26

28

24

25

27

25

22

27

25

26

28

25

24

22

27

24

15

0 4

4

.8

.....

-----

.3

5

.5

5

.....

.6

7

.4 

.fi

50

50

5?

50

62

62

35

60 

50

50

50

60

50

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Tr.

Tr.

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0. 2-0. 5

0. 2-2. 5

0. 5-1. 1

0 2-0. 9

0. 2-0. 6

295165 55- -12
172 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PEKTHITE-PLA.OIOCLASE-QUARTZ

RATIO OF PERTHITE TO PLAGIOCLASE

Q1 A

815

816

817

QOA

821

823

824

825

OOQ

830

831

S32

834

S35

S37

839

$42

848

:891

 922

924

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927 

928

934

935

937

OM WO

956

967

981

994

1004

1013

1028

1036

1038

1039

1042

1043

1044

1054

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F

F

F

F

M

F

F

F

F

F

F

F

F

M

M

F

F

F

F

M 

F

F

F

F

F

F

F

F 

F

F

F

F

F

F

F

F

F

F

F

F

F

F

M

F

M

F 

F

F

F
APPENDIX B 173

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthito

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

PEGMATITES Continued

IS ABOUT 2 TO 1 Continued

20

90

? )

9*

OK

23

95

25 

20

15

OO

oe

?,o

93

28 

27 

25

91

28

30

30

27

2fi

?,fi

?6

2fi

28

25

27 

96

26

20

24

25

27

28

97

26

27

OK

28

25

97

20on

09

QA

31

39

10

22

24

?,0

.....

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-----

- 

-----

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55 

58

55

55

55

55

58

55 

fiO

fi5

50

57

60

60

56 

51 

54

55

58

60

55

50

52

52

54

52

55

50 

53

52

57

54

55

53

51

53

52

53

RQ

52

55

CO

55

55

60

65

fin

60

50

50

52

50

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54

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25 

22

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20

20

17

18 

20

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18

20

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Tr.

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Tf.

Tr.

Tr.

Tr. 

Tr.

Tr.

Tr.

Tr.

Tr.

0. 2-1. 9

6. 1-6. 7

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0. 1 x 0. 1

0. 2 x 0. 3

0.2-0.4 

0. 5-1. 2

0. 5-1. 2

0. 3 x 0. 8

0. 05-0. 6
174 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(Pi. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH 

PERTHITE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

1057 

1058 

1060 

1063 

1064 

1065 

1066 

1070 

1072 

1073 

1075 

1089 

1090 

1097 

1099 

1100 

1101 

1103 

1106 

1112 

1114 

1115 

1116 

1120 

1121 

1122 

1124 

1127 

1128 

1130 

1132 

1136 

1137 

1139 

1142 

1143 

1149 

1151 

1152

1156 

1159

1164 

1165

1167

1168

1169 

1173

1178 

1182b 

1183

1185

1186 

1188

1189 

1192 

1201

T202

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branching.

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__ do.... ..............

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--- do....... ..... ...

. __ do.. _ _ . .- .--

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 -do.... ... ... 

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 do.... 

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..... do....... - 

Uo - do... ..] --'.

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. -.. do-.... . ------------ .....do.--- ------- -

Banded 

Multiple, homogeneous. - 

Homogeneous. . 

F 

F 

F 

F 

F 

F 

F 

F 

F 

M 

F 

F 

F 

F 

F 

M 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

M 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F

MF 

F

M

M; 

F 

MF 

F 

F

F

F

F

F 

F

F
APPENDIX B 175

pegmatites^- Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES Continued 

P£GMATITES-Contlnuea 

IS ABOUT 2 TO 1 Continued

26

25

25

23

27

20 

20

27

25

27

20

28 

20

24

25

25

24

25

30

28

27

23

20

28

25

25

25

22

20

20

25

26

25

26 

27

25

17

15

20

22

24

32

29

23

28

31

32

31

20 

28

28

28

28

28

23

28

28

.....

.....

0 6

.....

6

.....

fi

54

55

55

57

55

60 

60

53

55

55

60

52 

60

53

55

55

55

48

58

60

51

60

60

55

58

55

55

57

58

60

48

54

55

52 

52

55

63

65

60

60

58

58

60

fi>;

60

58

62

60

57 

50

52

56

50

52

60

52

52

.....

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1

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1

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8

20

20

20

20

18

20 

20

20

20

18

20

20 

18

23

20

20

21

26

12

12

22

17

20

17

17

20

20

21

22

20

25

20

20

22

21

20

20

20

20

18

18

10

11

12

12

11

8

9

23 

22

20

16

22

20

17

20

20

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8

x

X

X

x

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x

x

x

jj

2

X

X

x

X

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.....

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.....

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J£

X

x

.....

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X

J£

X

X

X

X

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Beryl... ...

Beryl......

Beryl...... 

.....do.....

Beryl......

__ do......

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Beryl......

Beryl......

Tr.

Tr.

Tr.

6.14

Tr. 

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0. 2-0. 4

0.1x0.4

0. 9-2. 4

0.4 x 0.6 

. 0.5x1.2

0.2x0.6

0. 5-1. 2

0. 2-1. 1

0. 4-0. 8
176 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

[Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

FELDSPAR-RICH

PERTHITE-PLAGIOCLASE-QUARTZ

RATIO OF PERTHITE TO PIAGIOCIASE

1208 

1209 

1212

1213 

1218 

1222 

1225

1229

1233 

1234 

1235 

1241 

1242 

1245 

1249 

1250 

1251 

1252 

1253 

1254 

1255 

1257 

1258 

1259 

1261b 

1265 

1268 

1272 

1273 

1275 

1276 

1277 

1278 

1279 

1280 

1282

1283

1284

1285 

1287 

1288

1289 

120O

1291

1292 

1293 

1294

1295 

1296

1298

1299 

1300 

1301

Schist....... 

- do-..-

- do.. 

.... .do 

_ .do... ...

 do-...-

 .do ...

- do --

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. .do 

 . .do...... 

- do ...

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 do 

 do 

.... .do... ....

Granite ..... 

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 do... 

 do. 

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 -do 

Schist 

Granite __

Granite. 

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.--..do ..

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Granite and

schist. 

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 do ... Tabular. 

Multiple, homogeneous- . 

_ .-do...- _____ ...

. . do... ... ...

Multiple, homogeneous..

Multiple, homogeneous 

..... do 

Multiple, homogeneous..

__ do.... __ -------

 _do_ ..

Multiple homogeneous. .. 

...-do- --------------

.. do _ ............

... .. do ..... 

 do. . 

Multiple homogeneous 

 -do . -----

 do 

. do... .... ... ...

..... do 

 do ..... ...

- .do -

Multiple homogeneous- - -

 do... ..... -

..... do ....... 

.... .do -

 .do 

Multiple homogeneous- .

Muittnle homogeneous. .. ZonedK- ---

___ do _________ . ....

..... do - Multiple homogeneous...

--...do ___ -------...--..

.... .do.........-.-.-

Homogeneous. ---._. ... .....do ..... ... -

 do --- 

Multiple homogeneous Homogeneous...........

..... do ........ ..... ..

F 

F 

F

F 

F 

F 

F

F

F 

F 

F 

F 

F 

F 

M 

F 

F 

F 

F 

M 

M 

M 

F 

F F ' 

F 

F 

F 

F 

M 

M 

F 

F 

F 

F 

F

F

F

M

F

F 

F 

F

F

F

F 

F

F

F

F

F

F 

F 

F
APPENDIX B 177

pegmatites Continued

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Percent

Size 

(n.)

Garnet

Percent

Size 

(in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PE OM ATITES C ontinued 

PEGMATITES-Contlnued 

IS ABOUT 2 to 1 Continued

24

25

27

17

28

28

24

26

26

27

28

28

OQ

26

25

3228

9<5

29 

26

94

?,7

22

30

97

26

30

?,5

10

20 

28

30

15

25

20 

10

Tr

19

99

25 

20

24 

20

15

15

15

15

15

25 

15 

20 

17

.....

.....

.....

- 

.....

n 3

6

-----

.....

58

55

53

60

5?,

5?

53

50

54

51

51

5?,

50

52

60

50

54

54

52

56

55

55

58

50

70

55

52

5?,

60

65

60 

50

50

65 

67

67

60 

60

56 

58

54 

60

56 

55

40

40

40

65

40

60 

60 

60 

44

.....

.....

.....

.....

.....

1

.....

..

-----

18

20

20

23

20

20

18

24

20

22

21

?,0

91

2?,

15

18

18

91

19 

18

91

18

20

20

91

18

22

18

15

9S

20

99

20

20

10

18

20

00

22

20

21

20

20

OR

45

AR

45

20

45

15 

25 

20 

39

.....

.....

.....

.....

.....

O K

3

.....

.....

 

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

1

Tr

3

X

X

X

.....

.....

.....

.....

.....

"oT

.3

.....

.....

E

X

X

.....

.....

.....

X

X 

X 

X

.....

.....

.....

.....

.....

 

.....

.....

.....

-----

.....

X

X

X

X

X

X

X

X

X

X

X

X

£

X 

X 

X

.........

.........

.........

.........

.........

.........

.........

.........

.........

.........

Beryl......

Beryl...... 

Biotito--.--

Beryl......

Beryl...... 

.....do. 

Beryl......

.....do .

... ..do 

.....do... 

Biotite.-.-.

Beryl... ...

.....do 

 ..do 

Beryl. ... ..

Beryl... 

Beryl......

Beryl......

.....do..... .

.....do .

.....do - 

.....do. 

.....do... ...

Tr. 

Tr.

Tr. 

Tr.

Tr.

Tr. 

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

Tr.

0.01

Tr.

Tr.

Tr.

Tr.

Tr.

Tr. 

.02 

Tr.

0. 1-0. 4

0.4-0.9

0. 1-0. 2

0. 6-1. 4 

0.2-0.8

0. 3-0. 8

0. 1-3. 4

0. 1-1. 2

0. 1-0. 4

0. 2-1. 3 

0. 2-1. 5

0. 1-0. 6

0. 1-1. 8

0. 2-2. 4

0. 2-3. 5

0. 2-1. 0

0.2-0.8

0. 6-1. 4

0.4-1.3 

0. 2-2. 4 

2.3-4.6
178 PEGMATITES OF THE CRYSTAL MOUNTAIN DISTRICT, COLORADO

Mineralogy of

Alteration column: T, tourmalinized. Texture column: F, fine, less than 1 inch; M, medium, 1-4 inches;

0.01 percent. Size columns:

Pegmatite

(pl. 5)

Wall rock

Type and 

formation

Alteration

Pegmatite

Relation to wall 

rock Shape Internal structure Texture

QUARTZ-RICH

13 

14 

15 

16 

30

35 

43 

167 

168 

199

201 

205 

206 

208 

222 

223 

225 

335 

495 

525 

598 

616 

617 

651 

679 

713 

720 

767 

775 

851 

852

899

901

902 

975 

1014 

1023 

1033 

1053 

1059 

1082 

1110 

1145 

1198 

1210

Schist.... 

... -do 

... ..do ..

 do 

.-...do .

 do 

..... do . 

 do 

 do... ....

 .do . .

 do 

.... .do 

..... do .

 . do ... .

 do 

 do 

....-do ..

Granite. .... 

Schist-. .

 do 

-_._do _

..... do-.-...

 do 

..... do 

..... do .. 

 do ...

 do .....do ... 

 do .. 

 do 

 do ....

.....do.......

.....do 

 do .

..... do 

 .do 

..... do 

.....do .. 

 do 

 do .. 

.... .do 

..... do. . ..

.....do 

.--do 

None 

... do 

... do 

... do 

... do -

...do 

...do 

... do 

... do... -

... do 

...do -

...do 

...do 

...do 

... do 

 do ..

...do 

 do .. 

...do .

-..do .

...do .

... do 

... do 

... do 

...do 

 do 

... do - 

... do 

...do 

... do ..

... do 

...do 

... do 

.-.do -

... do 

... do 

...do . 

... do 

...do 

...do 

...do -

... do 

. do 

...doConcordant .... . 

..... do - 

Unknown-...-..

Concordant. .... 

-...do 

Discordant- . 

Concordant?....

 do 

.... .do 

..... do 

. do -----

Concordant?.-..

Concordant .... .

Concordant?... . 

Discordant?. __ 

Concordant .. . 

. do 

.....do --- 

.... .do -- 

Concordant?....

..... do 

..... do .... ...

Discordant?-.. . 

Concordant?.... 

.... .do 

Discordant ... 

.....do - ... 

.....do ... .

Unknown. .

Discordant. .... . 

-...do 

 do . 

.....do ... ... 

 do . 

 do .

......do . ... - 

 do... 

 do 

.....do. ... ... ...

 do 

.....do. .........

- do 

.....do... .......

.....do... ... .... ...

.....do ... ..... .

.....do... .... ..... .

.....do. .........

.....do. .........

.....do ... .... ..

..-.-do. ...-.

.....do ........ 

.....do ... .......

 do 

.....do .... - 

Lenticular. ....... 

.....do .......... 

.....do. 

 do 

.....do ........ 

....do ..........

.....do......---

Lenticular. ....... 

.....do .......... 

Irregular. ..... ---. 

Oval.. 

... ..do ... ... .

.....do... .......... 

 do . 

-....do-. ..--....--....

.....do ..... ... ... ...-

.....do....... --

One member of multiple 

pegmatite. 

 do 

_ ..do-.. ______ ...

.....do. .............

One member of multiple 

pegmatite.

__ do....... ...........

.....do- ...............

 do 

.....do . ....... ........

.....do ... ........... ..

.....do ..............

.....do ..............

 do 

Multiple... 

..... do.... ...............

 do .. ..... ... 

.... .do. . . 

.....do. 

..... do - 

..... do 

 do - 

 do . 

...-do -- 

.....dO -..- .........

 do . ...

.... . do .... . 

..... do ...... 

.....do. ..... .-..' 

.... -do- --------- 

... ..do ... 

.....do - 

 do 

 do 

.....do ..-.. .. 

...-.do ... ... .........

..... do 

 .do. . - 

 do .

M 

M 

M

M

M

M

M 

M 

M

M

M 

M 

M 

C 

M 

M 

C 

C 

M 

M 

M 

M 

M 

C 

M 

O 

C 

M 

M 

C 

M 

M

M 

M 

C 

M 

M 

C 

M 

M 

M 

C 

M 

M 

F

TOURMALINE-RICH

260

398

404

Granite 

..... do .... 

 _do 

None. 

... do 

 do 

Discordant.. 

..... do..~ 

 do . 

Lenticular .......

Tabular 

Homogeneous .__ .-...do .- --.::::::

.....do -.

M 

F

C
APPENDIX B 179

pegmatites Continued ^

C, coarse, 4-12 inches. Percent columns: x, less than 1 percent but more than 0.01 percent; Tr., less than 

t, maximum; *, average]

Pegmatite Continued

Mineralogy

Plagioclase

Percent

Size 

(in.)

Perthite

Percent

Size 

(in.)

Quartz

Percent

Size 

(in.)

Muscovite

Per- Size 

cent (in.)

Garnet

Per- Size 

cent (in.)

Tourmaline

Per- Size 

cent (in.)

Other minerals

Mineral Percent Size

PEGMATITES

0

0

0

3

0

n

Tr

Tr

Tr

Tr

3

fi

0

0

0

0

0

0

0

Tr

0

(?)

(?)

Tr

25

0

0

0

0

Tr

17

0

n

2

2

2

2

Tr

ft

2

4

4

2

2

12

9

Tr

2

5

3

Tr

Tr

(?)

20

(?)

3

0

?3

0

5

98

98

98

98

100

91

98

9fi

95

99

99

99

99

99

99

99

99

98

98

85

85

100

99

99

98

100

100

95

97

100

99

100

100

100

99

100

55

100

100

97

100

100

60

100

95

0

0

Tr

Tr

Tr

Tr

Tr

Tr

Tr

0

Tr

Tr

Tr

Tr

Tr

Tr

Tr

Tr

Tr

0

Tr

0

f Magnetite..

(.Hematite..

Tr.

Tr.

Tr.

PEGMATITES

Tr

28

0

 2

12

1

8

87

Tr

Tr

90

fiO

12

»

INDEX

Page 

A

Abstract...-.---.----.....--....--.._.__-.. 1-2

Acknowledgements........ .................. 5-7

Age relations of pegmatites.._... __....... 63

Albite........................................ 52

Allanite.-. -- ..- .... ....... 59

Alteration of wallrock........................ 54-56

Alienation of mica- and quartz-rich layers in

schist...__...............__. 12

Amoeboid pegmatites In granite_....--.--.- 58

Analysis, plagioclase-perthite-quartz pegmatite, wall zone of Hyatt pegmatite.

tables 15,16 

Analysis,sercite........................... table 10

Analyses, wall rock........................ table 13

Apatite....... ............................ 49,53,64

country-rock schist.-..--....-..__...... 12

Hyattpegmatlte. r .:!............ ........ 82

Autunltein pegmatite824.....-----.-....-.-.- 61

B 

Banded pegmatites....................._... 30-31

Barium_....--.--.----..---................. 60

Bertrandite... -------.---....-..-.---...... 53

Beryl-.....-..--.-.---..--........... 43-47,68,69,70

colors of.-...-..--.---.............-,..... 43

crystalline form of.-.......-.....-.......- 43

demand for..-.--.-.--.--.-.---.--.-.---.- 2 

distribution, indices.of.................... fig. 6

pegmatites bearing...._..___. table 8

preference....----.-_....__....... 58

with respect to granite intrusives.... table 7

found in zoned pegmatites................. 44

largest crystal of, found in homogeneous

pegmatite.._.................... 44

number of pegmatites containing.......... 46

theoretical and natural formulas of........ 44

grain plans of, Big Boulder prospect., flgs. 21,22 

Buckhorn Mica mine._._._flgs. 23-27 

Hyatt pegmatite....__....,__. flgs. 7-12

Beryl mines and deposits:

Big Boulder prospect................_.. 92

hood................._............. 96

wall zone...--------------_....__ 93

Buckhorn Mica mine, core_............. 106

dumps..........-..-_--..--.-.-...- 108

inner intermediate zone.. --...--...... 106

Hyatt pegmatite. ---.. ....... 81

Beryl No. 5 prospect_....................... 63

Beryllia................... .................. 55

content in H yatt pegmatite wall rock...... 73

Bibliography............-.-..-,..--.--..... 110-112

Bin Boulder prospect................._..... 88-86

beryl in hood of........ .................. 96

beryl in wall zone.__..... ....____. 93

boundary between hood and core._..... 22

core zone in.... ......_............. 26,91

exploration_......._.__.._.. ..... 92

fracture filling at....................... 23-24,91

garnet occuring in pocketsat...-...-...-.- 28

Page 

Big Boulder prospect Continued

geology..-..--..---.-.----..----.---...... 88-92

intermediate zone..................__... 26,00

hood in,--................................ 91

mapofarea . - _ -.. fig. 2 

mineral deposits.................. ___- 92-98

schist around_....-..---...-..-..---,... 9

structure._........- ....... ...... 19

wall zone..-..-.----..----..--------.-..-- 89-90

zonesin.__.. -..........-.----.-..-.... 89

BlgThompsonschist......................... 7

Biotite...... ...... ... ..- ... . 59

and muscovite.... --...-.....--.-...- 41-42

Bismuth......-...-.---....-....---.......... 60

Bismuthinite---.-----.-.------.-.-.----.--- 50-51

Borderzones..- -.--. -....--...--...-.--.--.. 24-25

in Big Boulder prospect.....-.--...-.-.... 89

Boron..--........-.-----.---..------.----.-... 60

Boulder Creek granite gneiss....... .. 8

Buckhorn Mica mine...........___... 21,96-110

beryl in core.... .... - . ...... 106

berylindumps...--...--.-. --.-...--..-.. 108 

beryl in inner intermediate zone. _...... 106

columbite-tantalite...................... 50,107

core......---....--..---.,--.-.- 26.102-104

distinguishing from intermediate zone

in.... .- 31

exploration.-....--..-- ........... .... 105

fracture filling.. ...... . .......... 99

geology...---..-.---- _.. -. 98-105

h istory of - -.. .. . . 97-98 

intermediate zone in. _ .. -- ..... 26

inner ............... ... :- 101

outer .. .-. ....-. 99-100

Iocati0730f- _ . . _. .-.- .-.-- 96

mapofarea...-- ... ...- flg. 3 

mineral deposits..._.... . .. 106-109

perthite in dumps of..--....-... --- 108

schist around.... -. -- 9

scrap mica..--.-.-....-.------------- - 107

south member of-- .---.. - .... 104-105

spodumeno. in dumps of.------- -------- 108

structure of _ 19

wall zone....... 99

west member of . . - 105

Calcium......--....-.

Chromium.._ 

Chrysoberyl ........

Coal Creek quartzite. 

Cobalt...-.. -.

... .- -..--. 60

. . . 60

. . 53

....... 7

... . 60

Columbite-tantalite.---------------- 50,68,69

Buckhorn Mica mine 107

Composition of granite.. ....- ------- 15

Concordant pegmatites, longest _.. 20

widest.........----.----.---.---.-.----- 20

multiple.... _. 20

Contact between pegmatite and granite at

Hyatt pegmatite..._..___.. 72

181
182 INDEX

Page 

Cores. ...'..- .................................. 26-27

beryl in at Buckhorn Mica mine.--.---.. 106 

Buckhorn Mica mine _ . . 102-104

Core drilling, deposits explored by...... _ .. 71-110

Big Boulder prospect--..-------------- ... 88-96

Buckhorn Mica mine _ 96-110

Hyatt pegmatite.. ____ ... ____ . _ 71-88 

Core zone, Hyatt pegmatite.... .-...-------.- 82

Country rocks.... ____ _ . _.___ 9-16

invasion of by pegmatite magma......... 64

quartz schist.. . __ . __ ...... _ . ___ 13

schist. -----..---.-..-...--.-.----.---... 9-14

apatite in- .... __ ... _ ..... _ ... 12

deformation of _ -.----.-........--.-. 14

foliation of __ . . .. ........ 12

lime silicate minerals.. -- - . 13-14 

magnetite in. _ ...................... 12

most abundant type of in. _ ......._ 12

quartz-mica, textural facies of.. ....... 13

tourmaline in _ ..................... 12-13

zircon in. _ ._ ___ 12

Crystallization of pegmatite magma. ......... 65

D 

Deformation __ ............................. 17

Description of the area.......--- ... -----.... 2-4

Diorite . . . .--.-.-..-.........-........ 16

Discordant pegmatites. ... ...--..-.----_-..... 17

Dominant minerals in pegmatites. ........... 9

Drill holes, logs of. .-. -------------------- 114-128

plans of at Hyatt pegmatite.-.--.--, figs. 13-17

Drilling, core, deposits explored by _ ___.._ _ 71-110

Big Boulder prospect.-..-.-...--... ...... 88-96

Buckhorn Mica mine.. ---------------- 96-110

Hyatt pegmatite.-...-------.- _ ........ 71-88

exploration by at Hyatt pegmatite.. _ 82

Dumps, beryl in at Buckhorn Mica mine _ ._ 108 

pethite in at Buckhorn Mica mine... ..... 108

spodumene in at Buckhorn Mica mine.'.. 108

E 

Eruptive rocks. .............................. 63

Exploration, Big Boulder prospect __ ------- 92

Buckhorn Mica mine.- .-...---..--.----.- 105

Hyatt pegmatite-.....----. ------------- 82-87

F

Faults in pegmatites __ ...--....--....... _ 17

Feldspar-rich pegmatites.. ..-..---.---.-..... 35

Fersman classification of pegmatites... ..._... 35

Pieldwork. ...... ....... --_- - 5-7

Flow structure, pegmatites parallel to.!....... A7-58

Fluorite ---- -. 53 

Foliation of schist.. ...--------.------------- 12

Fracture fillings... .__ ........._._......._ 23-24

Buckhorn Mica mine.. .-- - ^

Big Boulder prospect. -......_.........-.. 91

Hyatt pegmatite... --_--.-__.___,___. ._ 72

a

Garnet..... ......................... 47-48,58,59

Composition Of..- ----- --------- r table 9

In schist.................................. 47

Hyatt pegmatite... ...................... go

manganese in..__.__ ..... ..._..._ 48

specific gravity of---.--------.-.-....... 47

Page

Geology. ..-.------_ -------_................ 7-1S

Big Boulder prospect . ............. 88-92

Buckhorn Mica mine. ........... -..... 98-105

historical, summary of_...-...-...----.. 7-S

Hyatt pegmatite..._................... 72-82

G rain sizes, comparison of changes in zone and

homogeneous pegmatites........ table 3

in zoned pegmatites.. ..............^.... table 2

Granite.. ............................... 14-16, 51

amoeboid pegmaties in...____.-. ...... 58

analyzed for BeO..----------------- 65, table 11

composition of_...........--------.-.... 15

contact with schist...-----.-------------- 19

distribution of beryl with respect to..... table 7

longest pegmatite enclosed in..----..---... 20

magma, pegmatite derived from...--..... 04

Mount Olympus.------------.----- 14,15, 59. 63

pegmatites filling joints in...-,.------.--. 57

Pikes Peak............................... 63

quartz veins in...-----------..----------- 1

schist partings in......................... 15

sills structure of--- -------- -- . Hi-17

underlying mass of......----------------- 17

widest pegmatite enclosed in.....--.--.-. 20

Granite and pegmatite contact at H yatt pegmatite -. .-.- .--- 72

Gummite in pegmatite 824...._............ 51

H 

Hematite._................................. 53, 54

Hematite and magnetite.__----------------- 52

History, mining.....-----.--------- ------- 4

production, of Hyatt pegmatite -.-...- 71-72 

summary of geologic.___ .... ----- 7-S

Hood in Big Boulder prospect .___...... 91,96

Homogeneous and zoned pegmatites, relation

between.-.---------...----------- 67

Homogeneous pegmatites--------------------- 28-30

beryl crystals, largest found in .- . 44 

common minerals in____ - --.--- 28

definition of.............................. 28

relative proportions of minerals in........ 28

Hornblende------.--......_ .- -.-- 59

Hyatt pegmatite---------..----__..... 19, 71-88

analysis Of plagioclase-perthlte-quartz pegmatite from wall zone of..- tables 15,10 

apatite in_................... ------ 49,82

beryl grains, plan of.._........----- figs. 7-12

beryllia in wall rock of______- . 73

core zone in_............................. 26, 82

drill holes, plans of. ---------- figs. 13-1-

exploration of___ - _.. - _ _ .. 82-87 

five zones in......._.._.._._.....__......_ 24

garnet in.------------------------- «2

geology.--_...................----.--.... 72"S2

contacts . ______ ___________ 70

history of working---------------------- 71-72

ermediate zone : . ....--- 2G

inner __________

HthiophUite-triphylite in..____.___.__.... W

locationof ... - 71

mapping of............................... 72

miarolitic minerals in.._____._... 53

microclinein..--.-. ........ .... 82
INDEX 183

Page

Hyatt pegmatite Continued

milling of pegmatite........-......-----.- 88

mineral composition of...-------_...... 73

mineral deposits in......_............ 87-88

occurrence of beryl in....__.__...... 81

plagioclase, texture of...__.__..__ 82 

shoots in.................._............ 27

structure of..... . 72

telescoped zone in.---................... 27

tourmaline In........... .-.. - 82

wall zone in....__ __..._ __-_- ._ 73

zones of-------.-....-.----.-------------- 73

Hydrothermal replacement._____.--..... 64

Idaho Springs formation_....-.........-.--. 7,8,9

Intermediate zones....---.--..-----....-..-.. 26

Big Boulder prospect...__........__ 90

inner, Buckhorn Mica mine.--._------- 101

beryl-----..--...----..-.--....------. 106

Hyatt pegmatite--...-..-........-.. 81

outer, Buckhorn Mica mine.-._-_.--_--_ 99-100 

Hyatt pegmatite--...--..._........ 80

Internal structure of zoned pegmatites........ 23-28

Joints, pegmatites filling in graniteLanthanum . 

Lead........

60

Lens--....-----.....---....-.--.....-........ 27

Lime silicate minerals..__..----....-..-.... 13-14

Limonite...-------------.--..---...-....-.... 53,54

Lithiophilite-triphylite.--.__.........__... 49,52,82

Lithium minerals.--....__....___..._ 34-35

Lithium, in relict spodumene................. 52

Logs of drillholes........-...--.......---.. 114-128

M 

Magma...--....-...--.-----.---...-.---..--. 67

crystallization of to form pegmatites__. 63 

pegmatitic__ .....__.-.-..-_.. 64

solidicationof..._____...____ 65 

Magnesium.._.........________.,__ 60

Magnetite and hematite.__. __. _____ 52 

Magnetite in country-rock schist......_.. 12

Manganese, in garnet_.___...._..__.. 48

Metaborbernite._____._______... 51 

Miarolitic minerals___...__._____.... 53-54

Mica, demand for.............__-.-..... 2

preferred orientation in wall zone.._....

scrap...--....---....-.--..---...--.....-. 68

Buckhorn Mica mine.............._ 107

Microcline..._._____._.___._..... 38

Hyatt pegmatite.....___.____._ 82

Milling of pegmatite.....--..---------.----... 88

Mineral composition of Hyatt pegmatite...... 73

Mineral deposits, Big Boulder prospect___ 92-98 

Big Boulder prospect, beryl in............ 92

Buckhoru Mica mine......._____.. 106-109

Hyatt pegmatite.._--......._....._ 87-88

Mineral resources of the area...--....-.-..... 68-70

Page

Mineralogy ...-.-. ... ... 31-54 

descriptions of minerals ............... 36-54

See also names of minerals, 

felspar-rich pegmatites..-___ ..._ 35 

general sequence of assemblage ..........table 6

mineral proportions determined--------- 31

mineralogic types of pegmatites...____ 32-35 

quartz-rich pegmatites. -....--. -.. 35-36

tourmaline-rich pegmatites. 36 

wall-rock, control by.__.. --.._ 58-60 

Mineralogy of pegmatites...-..._. ... 130-179 

Minerals, common in homogeneous pegmatites. 28 

descriptions of (See also names of minerals). 36-54 

dominant in pegmatites....__---..--... 9

general sequence of assemblage..... . table 6

lithium..-..-.--.--..-.----..-----... 34-35

miarolitic_- ..._.. - ..... 53-54

most abundant.--.. --- --------- ... 36

proportions of determined.. _.. ...... 31

relative proportions of, in homogeneous

pegmatites-_ __ ... 28 

Mining, history of in the area..._ ...... 4

Molybdenum... ... 60

Mount Olympus granite.--------- 8,14,15,59,63

Multiple intrusion. _.__.__._____.. 30 

Multiple pegmatites... ... ___..__.... 30

longest...______.____ ____ 20 

Muscovite_ .-... -- -...-.- 59,69

Muscovite and biotite.............. ........ 41-42

Muscovite at Hyatt pegmatite............... 73

Origin of pegmatites...__ __ .... 63-68

Palezoic sedimentary formations....-- _... 7

Pegmatite 137, tourmaline in.__....___ 42

Pegmatite 629, tourmaline in.., ___... __ 30 

Pegmatite 807, apatite in.. __.. .... 49

Pegmatite 824, autunite in.... ..-.---.... 51

Pegmatite 899, hematite and magnetite in.... 52

Pegmatite 1039, chrysoberyl in......... ... 52

Pegmatite 1148, chrysoberyl in...._ ___ 52

Pegmatite 1155, chrysoberyl in......-... ... 52

Pegmatite 1158, chrysoberyl in.......___... 52

Pegmatite 1212, apatite in.. ._ ... 49 

Pegmatite, milling of.___ __ __ 88 

Pegmatites, age relations of------------------ 63

amoeboid, in granite.. -.... ... 58

banded-...-..------.-.-.-...-...-..- 30-31

changes of grain sizes in...__. .. table 3 

classification of by Fersman....--..-..... 35

concordant, longest...-----.......-.._. 20

concordant with schistosity.............. 56

consisting of two zones.----.-.......... table 4

discordant to schistosity-...-....._._ 56-57

distribution-__....--.-__...'.---___ 18

dominant minerals in......._-----..... 9

faultsin. . 17

feldspar-rich......__.______...._ 35

filling joints in granite. ..._ -_ 57 

grain sizes in three_- - -. table 2

gummite in.............................. 51
184 INDEX

Page 

Pegmatites Continued

homogeneous... . ... 28-30 

common minerals in_._........... 28

definition of-_...--------------------- 28

largest beryl crystal found in......_ 44

relative proportions of minerals in..__ 28 

zoned, relation between.............. 67

idealized plans of showing sequence of

types.-.---.-- ----- ----- fig. 4

individual descriptions of.--------------- 70

longest.-.---.---------------------------- 20

longest enclosed in granite................ 20

longest multiple..... .....-. .--.... 20

mineralogic types of..--.--------------.-- 32-35

multiple.-.--------.--------------------- 30

number mapped.-.--------------------.. 70

origin of---------------------------------- 63-C8

parallel to fl,ow structure.. -.. .....'.... 57-58

quartz,-rich_- 35-36,68

relation to wall rocks and structure.------ 54-63

shape and structure.---------- ...-... . 18-20

structure of discordant.-------------- _ 17

textures of. --------------------------- 20-23

tourmaline-rich-...---.------.----.--.--. 36

widest concordant-...-. ........... 20

widest concordant multiple--_-----..--._ 20

widest enclosed in granite................ 20

zoned..---.----- ---------------- 32

dominant units of- - _ -- - 34 

internal structure of----------------- 23-28

Pegmatite and granite contact at Hyatt pegmatite.------------ - ------- 72

Pegmatite bodies, small- . - . 71

Pegmatite magma, solidification of. ---------- 65

Pegmatite minerals produced --------------- table 1

Perthite _- -_-----_. .___ 37-38,68,69

Buckhorn Mica mine dumps.. - ._ 108 

Hyatt pegmatite.-.---.-- -------.. 73

Pikes Peak granite...--------.-------------- 8,63

correlation of variations of composition of. 39 

Plagioclase....... - 38-w, 70

Hyatt pegmatite.-.-------------------- 73

ranges in indices of refraction_.......... fig. 5

texture of at Hyatt pegmatite_-._ ____._ 82

Plagioclase-perthite-quartz pegmatite from

wall zone of Hyatt pegmatite,

analysis of_ - _ tables IS. 16

Pueumatolytic replacement................._ 64

Pocket. .-- 27

Pre-Cambrian rocks........... .- - 7

Previous work in the area...,._- _-_ ..___. 4-5

Quartz...___.__ ___

Hyatt pegmatite...

veins ia granite....

Quartz schist-.. 

Quartz-rich pegmatites.

Q

40-41, 70

... 16,63

... 13 

35-30, 08

Ralston schist.. 

Bare elements, In wall rflCfc, analyS6S Of....... 6H2

part in developing zoning ......_ 68

Relict spodumene..__ - - 52 

Replacement, hydrothermal.. ______ 64 

Replacement bodies..----.-.................^ 23,24

Page

S

Schist.... -------_............__...__. 9-14

alteration of mica- and quartz-rich layers

in...-.-.-..-....-. ...._..... 12

analyzed for BeO._ ___.____.._____ 55, table 12

apatite, zircon, and magnetite in__..... 12

contact with granite...-_............... 19

deformation of..-.---..-....-.--,-........ 14

foliation of...__._________...... 12

garnet in. - - -_ _. ._--___ 47

most abundant type of... _._......... 12

partings-....- - _ _ __ __. 35

in granite-----------..--....-.-.-----. 15

quartz_.----.-... -.-.---.............. 13

quartz-mica, textural facies of_......... 13

sillimanite in......-.---..-.............-- 49,59

structure of... -.... ... .______ 10

tourmaline .--------------------------- 42

 country rock, tourmaline in.............. 12-13

Schistosity, pegmatites concordant with...... 56

pegmatites discordant to....___........ 56-57

Scrap mica, Buckhorn Mica mine............ 107

Sericite - -......'..... 52,53

analysis of... -- ___._ table 10 

Shape and structure of pegmatites.._.._.. 18-20 

Shoot.. -. _ __-._- 27-:

Silicification of granite... 

Sillimanite.----------

in schist.-.-.--------

Silver.-...-... ------

 28 

...... 54

. -..-.. 49 

 ..---.. 59 

........... 60

Solidification of pegmatite magma__..___ 65 

South member of Buckhorn Mica mine 104-105 

Specific gravity of garnet. __.. 47

Spodumene, relict. ..............._._ 52

relict, at Buckhorn Mica mine dumps..-. 108 

Streak______._____________..... 27

Strontium......................... _.....__... 60

Structure ------------_.. 16-17

concordant multiple pegmatite, widest... 20 

faults in pegmatites.. _ _......... 17

flow, pegmatites parallel to............... 57-53

granite sills................... l^~17

Hyatt pegmatite.

internal, of zoned pegmatiteslongest concordant pegmatlte.

longest multiple pegmatite...._........

longest neematite enclosed in granite.....

schist___--.---.--..._---..--.-.-...

wall rock, control by._.__......_.......

widest concordant pegmatite..-.--.- ...

widest pegmatite enclosed in granite...-. 

Structure and shape or pegimiutea . ._______

structure and wall rock, relation to pegmatites.

Structure of internal units..

Surficial deposits.

Tantalum, demand for. 

Telescoped zones .......

Tertiary intrusive rocks..------- 7

Texture of pegmatites-.-... .__ _____ 20-23

size classification.-..-.--.----..--------'- 20-

Textural facies of quartz-mica schist.......... 13-
INDEX 185

Page 

Tourmaline...................... 42-43,53,54,58,59

black, in country-rock schist_...-.....- 12-13

Hyatt pegmatite.-.--.-.---.-.......--... 82

pegmatite 137..-..-...--..-.......-.------ 42

pegmatite 629 .. .. . 30

replacement origin of..............__.-- 42

Tourmal ine-ri ch pegmatites -------- __ -.-.-. 36

U 

Uraninite and related minerals......_____ 51-52

V

Vanadium. 60

W

Wall rock alteration.......................... 54-56

Wall rock and structure, relation to pegmatites. 54-63

 Wall rock, Hyatt pegmatite, beryllia in__.. 73

minor elements in........................ 60-62

spectrographic analyses of-.....-...-... table 13

Wall-rock mineralogy, control by............. 58-60

Wall-rock structures, control by.-.-...--.--.- 56-58 

Wall zones.----.-..........-.__...___... 25-26

analysis of plagioclase-perthitc-quartz 

pegmatite from Hyatt pegmatite..

tables 15, 16 

beryl in, at Big Boulder prospect......... 93

Buckhorn Mica mine._--..-----.--..-.. 99

Hyatt pegmatite-------.-.-------.---..-- 73

preferred orientation of mica in......__ 89

Weathering of Big Boulder pegmatite.-.--... 89 

West member of Buckhorn Mica mine. -.-... 105 

Wisdom Ranch prospect, chrysoberyl at_.. 53

Yttrium.

Page

60

Zircon in country-rock schist................. 12

Zirconium.... _____..--.----..... ...... 60

Zoned and homogeneous pegmatites, relation

between....-.------.-.----- ... 67

Zoned deposit, Big Boulder prospect......... 89

Zoned pegmatites.._........... ....---.. 32

beryl found in.-.....-.----...------...... 44

dominant units of....-----..---- ...... 34

internal structure of-.-----......-....-... 23-28

Zones................--.------------.--...---. 23-24

Big Boulder prospect. . .......... 89

border.................................... 24-25

Big Boulder prospect.____...__ 89 

core......--...-..-.-.---.-.----.-...---. 26-27

Hyatt pegmatite...................... 82

division of, at Hyatt pegmatite...__... 73 

intermediate....__-_.._.__.__... 26

Big Boulder prospect.____........ 90

inner, Buckhorn Mica mine.._..... 101

inner, Hyatt pegmatite...__..__.. 81

outer, Buckhorn Mica mine...--.-.- U9-100

Hyatt pegmatite-___.___.. 80

wall..................................... 25-2»

beryl in, at Big Boulder prospect_.. 93 

Big Boulder prospect................. 89-90

Buckhorn Mica mine_............. 99

O

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