COVER PHOTOGRAPHS 

1 2 3 4 

5 6 

7 8 

9 10 

11 12 13 14 

1. Asbestos ore 

2. Lead ore, Balmat mine, N.Y. 

3. Chromite-chromium ore, Washington 

4. Zinc ore, Friedensville, Pa. 

5. Banded iron-formation, Palmer, 

Mich. 

6. Ribbon asbestos ore, Quebec, Canada 

7. Manganese ore, banded 

rhodochrosite 

8. Aluminum ore, bauxite, Georgia 

9. Native copper ore, Keweenawan 

Peninsula, Mich. 

10. Porphyry molybdenum ore, Colorado 

11. Zinc ore, Edwards, N.Y. 

12. Manganese nodules, ocean floor 

13. Botryoidal fluorite ore, 

Poncha Springs, Colo. 

14. Tungsten ore, North Carolina 
Rutile in Precambrian 

Sillimanite-Quartz Gneiss 

and Related Rocks, 

East-Central Front Range, 

Colorado 

By SHERMAN P. MARSH and DOU1GLAS M. SHERIDAN 

GEOLOGY AND RESOURCES OF TITANIUM IN THE UNITED STATES 

GEOLOGICAL SURVEY JPROFESSIONAL PAPER 959-G 

Geologic and geochemical study of 

rutile-bearing rocks in Colorado 

and a description of their 

occurrence elsewhere 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976 
UNITED STATES DEPARTMENT OF THE INTERIOR 

THOMAS S. KLEPPE, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Main entry under title: 

Geology and resources of titanium in the United States. 

(Geological Survey Professional Paper 959) 

CONTENTS: Force, E. R. Titanium contents and titanium partitioning in rocks.-Force, E. R. Metamorphic source rocks of 

titanium placer deposits.-Black, M. C., Jr. and Morgan, B. A. Rutile and sphene in blueschist and related high-pressure facies 

rocks.-Herz, N. Titanium deposits in anorthosite massifs.-Herz, N. Titanium deposits in alkalic igneous rocks.- Force, E. R. 

Titanium minerals in deposits of other minerals.-Marsh, S. P. and Sheridan, D. M. Rutile in precambrian sillimanite-quartz 

gneiss and related rocks, east-central Front Range, Colorado. 

Includes bibliographies. 

Supt. of Docs. no.: I 19.16:959 A-G 

1. Titanium ores-United States. 2. Petrology-United States. 

I. Series: United States Geological Survey Professional Paper 959. 

QE390.2.T5G46 553'.462 75-619269 

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

Washington, D.C. 20402 

Stock Number 024-001-02834-4 
APPRAISAL OF MINERAL RESOURCES 

Continuing appraisal of the mineral resources of the United States is 

conducted by the U.S. Geological Survey in accordance with the provisions of 

the Mining and Minerals Policy Act of 1970 (Public Law 91-631, Dec. 31, 

1970). Total resources for purposes of these appraisal estimates include 

currently minable resources (reserves) as well as those resources not yet 

discovered or not currently profitable to mine. 

The mining of mineral deposits, once discovered, depends on geologic, 

economic, and technologic factors; however, identification of many deposits 

yet to be discovered, owing to incomplete knowledge of their distribution in 

the Earth's crust, depends greatly on geologic availability and man's 

ingenuity. Consequently, appraisal of mineral resources results in 

approximations, subject to constant change as known deposits are depleted, 

new deposits are found, new extractive technology and uses are developed, 

and new geologic knowledge and theories indicate new areas favorable for 

exploration. 

This Professional Paper discusses aspects of the geology of titanium as a 

framework for appraising resources of this commodity in the light of today's 

technology, economics, and geologic knowledge. 

Other Geological Survey publications relating to the appraisal of resources 

of specific mineral commodities include the following: 

Professional Paper 820-"United States Mineral Resources" 

Professional Paper 907-"Geology and Resources of Copper Deposits" 

Professional Paper 926-"Geology and Resources of Vanadium Deposits" 

Professional Paper 933-"Geology and Resources of Fluorine in the United States" 

CONTENTS 

Page 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G 1 

Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Geologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Precambrian metamorphic rocks . . . . . . . . . . . . . . . . . . . . . . . . 2 

Sillimanitic biotite gneiss (unit A) . . . . . . . . . . . . . . . . . . . 3 

Biotite gneiss (unit B). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Interlayered feldspar-rich gneiss, hornblende gneiss, 

and amphibolite (unit C).......................... 3 

Hornblende gneiss and amphibolite (unit D)........... 3 

Feldspar-rich gneiss (unit E)........................ 3 

Rutile-bearing gneisses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Chemical composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Geochemistry of rutile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Origin of metamorphic rocks . . . . . . . . . . . . . . . . . . . . . . . . 12 

Major lithologic groups . . . . . . . . . . . . . . . . . . . . . . . . 12 

Precambrian metamorphic rocks-Continued 

Origin of metamorphic rocks-Continued 

Page 

Rutile-bearing gneisses .......................... G13 

Other localities of rock types similar to those in the 

east-central Front Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

Farmville district, Virginia . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Kings Mountain district, North CarolinaSouth Carolina.................................. 14 

Graves Mountain, Georgia. . . . . . . . . . . . . . . . . . . . . . . . . . 14 

White Mountain, California......................... 14 

Yuma County, Arizona. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Santa Cruz County, Arizona . . . . . . . . . . . . . . . . . . . . . . . . 15 

Other United States occurrences . . . . . . . . . . . . . . . . . . . . 15 

World occurrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 15 

Economic potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

ILLUSTRATIONS 

Page 

FIGURE 1. Map showing distribution of Precambrian igneous and metamorphic rocks in east-central Front Range, Colo. . . . . . . . . . . G2 

2. Generalized geologic map showing distribution of Precambrian rutile-bearing gneiss, east-central Front Range . . . . . . . . 4-5 

3-8. Photomicrographs: 

3. Rutile alined parallel to foliation in biotite-quartz-plagioclase gneiss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

4. Rutile alined parallel to foliation in sillimanite-quartz gneiss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

5. Fibrolitic sillimanite partly replaced by topaz and partly recrystallized to prismatic sillimanite . . . . . . . . . . . . . . . . 7 

6. Rutile associated with topaz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

7. Prismatic sillimanite intergrown with rutile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

8. Rutile associated with corundum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

TABLES 

Page 

TABLE 1. Analytical data for rutile-bearing gneiss and for other Precambrian metamorphic rocks, east-central Front Range, 

Colo.................................................................................................. G9 

2. Semiquantitative spectrographic analyses of rutile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

3. Standard of purity for rutile................................................................................. 12 

4. Ionic substitution factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

METRIC-ENGLISH EQUIVALENTS 

Metric unit 

centimetre (em) 

metre (m) 

kilometre (km) 

= 0.3937 

= 3.28 

= .62 

English equivalent 

inch (in) 

feet (ft) 

mile (mi) 

v 

GEOLOGY AND RESOURCES OF TITANIUM 

IN THE UNITED STATES 

RUTILE IN PRECAMBRIAN SILLIMANITE-QUARTZ 

GNEISS AND RELATED ROCKS, 

EAST-CENTRAL FRONT RANGE, COLORADO 

By SHERMAN P. MARSH and DOUGLAS M. SHERIDAN 

ABSTRACT 

Unusual rutile-bearing gneisses are thinly interlayered with 

metasedimentary and metavolcanic gneisses of Precambrian age in 

the east-central part of Colorado's Front Range. Layers and lenses 

of rutile-bearing gneiss range in thickness from 15 em to 30 m and 

in rutile content from trace amounts to about 5 percent. Rutile is 

most abundant in a sillimanitic topaz-quartz gneiss but is also found 

in sillimanite-quartz gneiss and biotite-quartz-plagioclase gneiss. 

The rutile-bearing sillimanitic gneisses have a simple but unusual 

mineral and chemical composition because they contain little else 

but quartz, sillimanite, ±topaz, and accessory rutile. Spectrographic analyses of rutile from the east-central Front Range and 

from eleven other localities in the United States indicate that the 

Front Range rutile is relatively pure, that is, it contains fewer 

metallic cations. 

We believe that the rutile-bearing gneisses originated from 

intermediate to basic tuffs and flows; intense weathering resulted 

in clays enriched in titania, alumina, and silica. These weathering 

products were reworked by surface waters, and fluorine from 

volcanic sources was adsorbed locally. Subsequently, the entire 

sequence of interlayered sedimentary and volcanic rocks was 

folded and metamorphosed to the sillimanite zone by regional 

metamorphism. 

Although the majority of known occurrences of rutile-bearing 

gneiss in the east-central Front Range may never be mined, owing 

to environmental and economic factors, this type of rutile occurrence is also found elsewhere and may represent potential rutile 

resources. 

INTRODUCTION 

Rutile occurs in thin layers and lenses of 

light-colored sillimanite-quartz gneiss and related 

rocks within a thick succession of Precambrian 

metamorphic rocks in the east-central Front Range, 

Colo. The known occurrences are in a belt, 3 km wide 

and 26 km long, that extends east-southeast from the 

vicinity of Idaho Springs to 4 km south of Morrison 

(figs. 1, 2). Layers and lenses of rutile-bearing gneis,s 

range in thickness from 15 em to 30 m and in rutile 

content from trace amounts to 5 percent. 

The presence of rutile in an unusual sillimanitic 

topaz-quartz gneiss located 10 km northwest of 

Evergreen, Colo., was noted in March 1968 by D.M. 

Sheridan during petrographic studies related to a 

program of regional mapping. D. M. Sheridan, S. P. 

Marsh, and R. B. Taylor reported the results of a 

preliminary geologic investigation of this deposit in 

U.S. Geological Survey Circular 567 (Sheridan, Taylor 

and Marsh, 1968). Marsh and Sheridan continued 

searching for additional deposits of rutile during field 

studies in 1968-69. Because the rutile-bearing rocks 

described here are rather undistinguished in 

appearance, they might very easily be overlooked, 

even by a trained geologist. 

This report summarizes the results of field and 

laboratory examinations of rutile-bearing gneisses of 

the east-central Front Range. These gneisses 

constitute a large resource of rutile. Rocks such as the 

sillimanitic topaz-quartz gneiss could be mined 

principally for topaz and sillimanite, both of which can 

be used by high-alumina refractory industries for the 

manufacture of mullite; salable byproducts of such an 

operation would be rutile, crushed quartz, and 

fluorine. The fact that these gneisses have not as yet 

been mined may be attributed to the high cost of 

hard-rock mining and milling (compared to the 

low-cost methods used in obtaining rutile from 

Australian beach sands); rising land values due to the 

westward spreading of suburban Denver; and likely 

objections of local residents. Although the rutile 

deposits described in this report may never be mined, 

similar deposits may be found in other gneissic 

terranes where mining might be possible. 

ACKNOWLEDGMENTS 

A major part of this investigation was conducted 

under a comprehensive research program authorized 

Gl 
G2 GEOLOGY AND RESOURCES OF TITANIUM 

, - ---, I -._ 

[ DENVER 

I 

Llfl I Morrison - --tJ 

0 10 20MILES 

0 10 20KILOMETRES 

EXPLANATION 

D 

Sedimentary rocks 

Pikes -Peak Granite 

1,040 m .y. 

Silver Plume Granite 

1,440 m .y . 

Boulder Creek Granite 

and related rocks 

1,710 m .y . 

Metamorphi c rocks 

Contact 

} 

CENOZOIC, 

MESOZOIC, 

AND 

PALEOZOIC 

PRECAMBRIAN 

45' 

FIGURE I.-Distribution of Precam):>rian igneous and metamorphic rocks in the east-central Front Range, Colo. (faults and 

Tertiary igneous rocks omitted). 

by the Office of Emergency Planning and undertaken 

by the Department of the Interior under the Defense 

Production Act for the purpose of developing a 

domestic source of rutile. U. S. Geological Survey 

colleagues W. N. Sharp, J. W. Adams, R. B. Taylor, 

Mary E. Mrose, and R. L. Erickson have helped with 

mineralogy and report preparation. 

GEOLOGIC SETTING 

The rutile-bearing gneisses lie within a broad area 

of Precambrian metamorphic and intrusive rocks in 

the east-central Front Range (fig. 1). Metamorphic 

rocks in this part of the Front Range are principally 

biotite gneisses and feldspathic gneisses, but 

amphibolite, hornblende gneiss, and calc-silicate 

gneiss are abundant in the east. All the area shown in 

figure 1 is in the sillimanite zone of regional 

metamorphism. Most of the pelitic rocks of the report 

area (fig. 2) are characterized by the stable pair 

sillimanite and potassic feldspar, but rocks of 

somewhat lower grade, characterized by the pair 

sillimanite/muscovite are common in areas to the 

northeast (Sheridan, Maxwell, and Albee, 1967, p. 

37 -38) and southeast (Bryant and others, 1973, p. 3.) 

In the east-central Front Range this high-grade 

metamorphism accompanied a long period of 

deformation involving two stages of plastic folding, 

the first of which formed tight to open folds trending 

west to northwest; these trends predominate in the 

report area (fig. 2). Elsewhere, these folds were 

modified subsequently by cross folds trending 

north-northwest to north-northeast (R. B. Taylor, oral 

commun., 1964). Late in this long period of tectonism, 

bodies of Boulder Creek Granite (largely granodiorite) 

were intruded; isotopic dating by Rb/Sr determinations indicates that the Boulder Creek Granite is about 

1,710 ±40 m.y. old (Hedge, 1969, p. 79). A third 

episode of folding, also accompanied by regional 

metamorphism and followed closely be cataclastic 

deformation, affected parts of the east-central Front 

Range at about the time the Silver Plume Granite was 

emplaced (R. B. Taylor, oral commun., 1967; Moench 

and others, 1962, p. 45-54; Sheridan, Maxwell, and 

Albee, 1967, p. 69-70); the age of the Silver Plume is 

about 1,400 ± 40 m.y. (Hedge, 1969, p. 81). This late 

deformation has only minor expression in the area of 

figure 2 (see zone of cataclastically deformed gneisses, 

Sheridan, Reed, and Bryant, 1972). The Pikes Peak 

Granite, youngest of the major Precambrian 

intrusives, was emplaced about 1,040 ± 10 m.y. ago 

(Hedge, 1969, p. 83). Late in Precambrian time 

extensive northwest-trending faults-the "breccia 

reefs" of Lovering and Goddard (1950, p. 79)-were 

formed (Tweto and Sims, 1963, p. 1001); some were 

reactivated during the Laramide orogeny. 

PRECAMBRIAN METAMORPHIC ROCKS 

In addition to the rutile-bearing gneisses, 

metasedimentary and metavolcanic gneisses occur in 

the report area and are divided herein into five 

principal units, units A to E of figure 2. Because 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G3 

primary sedimentary and volcanic features have been 

largely obliterated by high-grade metamorphism, 

stratigraphic relations among the five units are 

unknown. 

SILLIMANTIC BIOTITE GNEISS (UNIT A) 

Rocks of unit A are approximately coextensive with 

the rutile-bearing gneisses (fig. 2). Unit A is composed 

of gray fine- to medium-grained sillimanitic biotite 

gneiss containing abundant darker gray layers, 60 em 

to 15 m thick, of garnetiferous sillimanitic biotite 

gneiss and of cordierite-bearing sillimanitic biotite 

gneiss. Lenses of dark-colored coarse-grained 

cordierite-gedrite-garnet gneiss, 60 em to 15m thick, 

are present locally. 

BIOTITE GNEISS (UNIT B) 

Thick sections of unit B, biotite gneiss, occur in the 

southwestern part of the area (fig. 2). There and in the 

northwestern part of the area the adjacent rocks are 

commonly hornblende gneiss and associated rocks of 

unit D. In general lithology, unit B is somewhat 

similar to unit A but lacks the abundance of 

dark-colored layers of garnet-rich gneiss and 

cordierite-bearing gneiss. Unit B is composed of fineto medium-grained light- to medium-gray strongly 

foliated biotite gneiss containing 10-50 percent mica, 

with biotite generally predominant over muscovite. 

Two major varieties, commonly as alternating layers a 

few centimetres to 15 m thick, are biotite-quartzplagioclase gneiss and sillimanitic biotite-quartz 

gneiss. Some of the rocks are microcline-bearing and 

some are sparsely garnetiferous. Lenses of 

calc-silicate rock occur locally. Thin conformable 

seams of granitic material are abundant locally but are 

usually erratically distributed in this map unit. 

Granitic material, however, forms 25 to 50 percent of 

an especially migmatitic variety of biotite gneiss in the 

northeastern part of the area. 

INTERLAYERED FELDSPAR-RICH GNEISS, 

HORNBLENDE GNEISS, AND AMPHIBOLITE (UNIT C) 

Unit C is composed of feldspar-rich gneiss, 

hornblende gneiss, and amphibolite similar to those of 

units D and E, with which unit C is intercalated. In 

unit C these rocks are interlayered in approximately 

equal thicknesses on a scale of several centimetres to 

10 m or more; locally one or another rock type 

predominates. Interlayers of medium- to dark-gray 

biotite-quartz-plagioclase gneiss are locally abundant. 

Layers and lenses of the relatively dark-colored 

hornblende gneiss, amphibolite, and biotite gneiss are 

common in the feldspar-rich gneiss (unit E), but even 

in unit E they form less than 25 percent of the total 

rock exposed. 

HORNBLENDE GNEISS AND AMPHIBOLITE (UNIT D) 

The rocks of Unit D are commonly interlayered on a 

scale ranging from 30 em to 30 m. Hornblende gneiss 

and amphibolite are dominant, but interlayers of 

calc-silicate gneiss, impure marble, and quartz gneiss 

are common in the southern half of the area. 

Cordierite-bearing biotite gneiss is common as 

interlayers in- unit D shown terminating westward 

against unit B (fig. 2). Feldspar-rich gneiss, especially 

the medium-gray plagioclase-rich variety, is also 

present in parts of unit D. 

Fine- to medium-grained medium- to dark-gray or 

greenish-gray hornblende gneiss contains, in addition 

to hornblende and plagioclase, 15 percent or more of 

other minerals-clinopyroxene, quartz, biotite, or 

epidote-group minerals. Compositional layers range in 

thickness from 6 mm to a metre or more; parallel 

planar alinement of hornblende defines the foliation. 

Fine- to medium-grained dark-green to black 

amphibolite, consisting predominantly of hornblende 

and plagioclase, is unlayered but variably foliated. 

Fine- to coarse-grained calc-silicate gneiss displays a well-developed compositional layering on a 

scale of a millimetre to a metre. Colors of 

the calc-silicate gneiss are dark gray, light green, 

yellowish green, white, gray, pinkish, or black, 

depending upon the various proportions of plagioclase, hornblende, epidote, clinopyroxene, microcline, 

quartz, sphene, garnet, calcite, vesuvianite, scapolite, cummingtonite, tremolite, and magnetite-ilmenite. The coarse-grained variety of calc-silicate gneiss 

is common as pods or lenses rich in garnet, 

epidote, and quartz. Lenses of medium-grained 

impure marble are abundant locally and contain 

garnet, epidote, clinopyroxene, and other minerals of 

the calc-silicate gneiss assemblages in addition to 

calcite. Lenses and layers of fine-grained quartz 

gneiss are common near contacts with other rock 

units, range in thickness from 0.3 to 6 m and contain 

variable amounts of magnetite-ilmenite and garnet. 

Fine- to medium-grained biotite gneiss contains 

cordierite, variable amounts of sillimanite, and palebrown biotite. 

FELDSPAR-RICH GNEISS (UNIT E) 

UnitE is composed of fine- to medium-grained lightto medium-gray, tan, or pinkish-gray feldspar-rich 

gneiss and is characterized by the predominance of 

feldspar and quartz over biotite. A closely spaced 

foliation is formed by planar alinement. of biotite, 

which commonly forms less than 10 percent of the rock 
G4 GEOLOGY AND RESOURCES OF TITANIUM 

though locally as much as 15 percent. Light-colored 

granitic-appearing varieties of the rock contain as 

much as 50 percent microcline; somewhat darker 

plagioclase-rich varieties contain only traces of 

microcline. Conformable dark layers and lenses of 

hornblende gneiss, amphibolite, or biotite-quartzplagioclase gneiss, 13 mm to a metre or more thick, 

are locally abundant but generally are not continuous 

for more than 100 m. Much of the feldspar-rich gneiss 

is similar to rocks mapped as microcline-quartz-plagioclase-biotite gneiss in nearby areas (Moench, 1964, p. 

5 M ILES 

5 KILOMETRES 

FIGU RE 2.-Generalized geologic map showing distribution of 

A19-A24; Sims and Gable, 1967, p. E8-Ell; Sheridan, 

Maxwell, and Albee, 1967, p. 16-17). 

RUTR.E-BEARING GNEISSES 

Several conformable layers and lenses of rutilebearing gneisses are shown in figure 2. The 

rutile-bearing gneisses are most commonly associated 

with rocks of units A and D, and locally with unit C; 

some are along contacts between the main rock units. 

The longest and most continuous layers are in the 

western half of the area (fig. 2). The southwestern-
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G5 

EXPLANATION 

Sedimentary rocks 

Unconformity 

Leucosyenite 

2 Related to Pikes Peak Granite 

f: ±!: :> l s Silver Plume 

Granite 

+ 

} a 

z 

.. 

>-} 1 ntruded about 

~ 1,040 m.y. ago 

a: 

a> 5} Intruded about If 1,440 m.y. ago 

L_------------'----------+-------139°37'30" ~ + 

Boulder Creek Granite 

and other plutonic rocks 

Pegmatite } 

Intruded about 

1,710 m.y. ago 

I I 

I I I I I 

5 MILES 

I 

0 l 2 3 4 5 KILOMETRES 

Geology simplified from the foll.owing sources: 

1. Geology of the Squaw Pass quadrangle 

Mapped by 

4 

Amphibolite Gneiuic hornblende 

quartz monzonite } 

Probabl.y intruded 

pnor to 

1,710 m.y. ago 

S Douglas M. Sheridan, 1961-70, 1972, unpublished information 

M Sherman P. Marsh, 1968-69, 1972, unpublished information 

Rutile-bearing light-colored gneisses 

2. Sheridan, Reed, and Bryant (1972) 

3. Gable (1968, Plate 11 

4. Bryant and others (1973) 

Precambrian rutile-bearing gneiss, east-central Front Range, Colo. 

most layer ranges in thickness from 30 em to 21 m and 

has an outcrop length of about 13 km. About 0.15 km 

north of the eastern end of this layer is a rutilebearing lens 3.5 km long and as much as 150 m 

thick; this lens is actually composed of numerous 

smaller lenses of rutile-bearing gneiss, 6 to 30 m thick, 

separated by variable amounts of sillimanite-rich 

biotite gneiss. In the area between the southwesternmost layer and Interstate Highway 70 are three other 

lenses of rutile-bearing gneiss, ranging in length from 

2 to 3 km and in thickness from 30 em to 9 m. Other 

UnitE 

Feldspar-rich gmtiu 

Unit 0 

Hornblende gneiss and amphibolite interiiJyered 

with 11ariable amounrs of calc-liliciJttl gneiss, 

cordierite·bearing biotite gneiss, impure mar· 

ble, and quartz gneiss 

Unit C 

lnter/ayered feldspar-rich gnttiu, hornblende 

gneiss, and amphibolite, with locally abun· 

dant biotite gneiss 

Unit B 

Biotite gneiss 

Unit A 

Silfimanitic biotite gneiss containing garnetbearing /eyers end cordierite-bearing layers 

Contact 

Fault 

Dashed where inferred 

.9 .F 

Sample localities 

Numbers refer to sample numbt~rs in tebles 

1 and 2. Letters designate localities 

from which two or more samples (tables 

1 and 2} were taken: 

A-1,11,12 

B-2, 17 

C-3, 16, 20 

0-4, 13, 14, 21 

E-22, 26, 27 

F-23, 24 

G-28, 30, 31 

H-34, 35, 36, 37 

X 

z 

~ 

g; 

:li 5 Complexly 

w interlayered and 

~ intergradational 

J 

units- no 

stratigraphic 

order implied. 

Deposited prior 

to 1,710 m.y. ago 

lenses shown on figure 2 are short; they range in 

length from 60 to 780 m and in thickness from 15 em to 

30m. 

The rutile-bearing gneisses are generally lighter in 

color than the adjacent rocks. Whereas this 

characteristic is a useful megascopic feature when 

doing field studies in this region, it is by no means 

infallible. Other light-colored Precambrian rocks 

which occur similarly as thin layers and lenses but 

which are generally devoid of rutile are numerous 

varieties of feldspar-rich gneiss, calc-silicate gneiss, 
G6 GEOLOGY AND RESOURCES OF TITANIUM 

cordierite-bearing biotite gneiss, and quartz gneiss as 

well as pegmatite and aplite. A hand lens is nearly 

always necessary to check for the presence or absence 

of tiny splendent grains of rutile, which most 

commonly is red but which also can be black, orange, 

or pale orange-yellow; the rutile grains are generally 

anhedral and less than 0.5 mm in size. Sillimanite is 

commonly present in noteworthy amounts in several 

varieties of rutile-bearing gneiss. Although some of 

these gneisses resemble other layered quartz gneisses 

which are common in this region, they lack the 

magnetite, ilmenite, or garnet which usually occur in 

the local quartz gneisses. Where biotite is present, it 

commonly is pale brown under the hand lens in 

contrast to its black color in most biotite gneisses and 

feldspar-rich gneisses of the region. Generally, the 

biotite content of rutile-bearing gneiss is less than that 

of the more common biotite gneisses of the region. 

The rutile-bearing gneisses are generally fine- to 

medium-grained; some appear coarse grained owing 

to the presence of large crystals of prismatic 

sillimanite and, more rarely, corundum in a fine- to 

medium-grained matrix. Some of the lenses are 

composed of one variety of gneiss but most layers and 

lenses are composed of several interlayered and 

intergradational varieties. Most common among the 

varieties are biotite-quartz-plagioclase gneiss, sillimanite-quartz gneiss, and rocks gradational between 

these two. In these rocks rutile commonly occurs in 

amounts of0.5 percent or less but locally as much as 2 

percent. Rutile-bearing sillimanitic topaz-quartz 

gneiss is the principal variety in the eastern part of 

the longest rutile-bearing layer (from sample locality 

A to D, fig. 2), in short lenses at and near sample 

locality 33, and in two partially exposed layers or 

lenses at sample locality H. The rutile content of the 

sillimanitic topaz-quartz gneiss is commonly in the 

range 1 to 2.5 percent and locally is about 5 percent. 

Rutile-bearing biotite-quartz-plagioclase gneiss is a 

light-gray moderately well-foliated rock that is rich in 

plagioclase (commonly 45 to 55 percent). The 

plagioclase is albite-oligoclase rather than the 

oligoclase-andesine usually found in other biotite 

gneisses and feldspar-rich gneisses of the region. 

Biotite, most often a pale-brown phlogopitic variety, 

generally comprises less than 15 percent of the gneiss. 

Locally the gneiss grades to a darker gray color, 

corresponding to the presence of some layers 

containing black biotite. Andalusite, in blocky grains 

of 1 mm or less, is present locally as a rare accessory 

mineral. As viewed in thin section (fig. 3) subparallel 

grains of biotite define the foliation in rutile-bearing 

biotite-quartz-plagioclase gneiss; elongate grains of 

rutile are alined parallel to the foliation. 

Rutile-bearing sillimanite-quartz gneiss is a white to 

creamy-white rock consisting dominantly of quartz 

and typically 20 to 30 percent sillimanite. The rock 

might also be called a sillimanitic quartzite because 

feldspar is rarely present in noteworthy amounts 

except in rock gradational to biotite gneiss. Muscovite 

is more common than biotite but the total mica content 

is generally less than 2 percent. The sillimanite is in 

fibrolitic needles that form interlensing laminae 

between thin granular quartz septa, giving the rock a 

thinly layered and moderately well-foliated appear-

~mce. As viewed in thin section (fig. 4), elongate grains 

of rutile are alined parallel to the foliation defined by 

the fibrolitic sillimanite. 

Rutile-bearing gneisses gradational in composition 

between sillimanite-quartz gneiss and biotite-quartzplagioclase gneiss are light gray to gray and 

moderately to well foliated. Although the principal 

minerals occur in variable amounts, most commonly 

quartz predominates greatly over plagioclase, 

sillimanite ranges from 5 to 20 percent, and biotite is 

15 percent or less. 

Rutile-bearing sillimanitic topaz-quartz gneiss is a 

white fine- to medium-grained rock composed chiefly 

of quartz and topaz and lesser amounts of sillimanite, 

rutile, and apatite; muscovite and zircon are accessory 

minerals. Medium-grained white or glassy quartz 

layers 2 mm to 4 em thick alternate with discontinuous 

thinner layers of finer grained creamy granular 

topaz-rutile rock and with radiating coarse-grained 

aggregates of prismatic sillimanite. The rock is similar 

in appearance to a layered sillimanitic quartzite and is 

not readily distinguished except by its greater heft, 

owing to the high specific gravity of topaz (::::::::3.5). 

Rutile commonly is concentrated in thin layers colored 

pale reddish by the tiny splendent rutile crystals. 

Samples of the gneiss contain rutile in amounts 

ranging from 0.3 to 5.3 percent (TiOz determined by 

X-ray fluorescence) and topaz from 22 to 67 percent 

(mineral separation by heavy liquid). Fibrolitic 

sillimanite forms a linear orientation in some 

sillimanitic quartz laminae. Prismatic crystals of 

sillimanite, as much as 2 square mm in cross-sectional 

area and 3 em in length, are in irregular to radiating 

aggregates flattened parallel to the layering but they 

lack linear orientation. Locally the gneiss contains thin 

laminae as much as 5 mm thick composed of a green 

crhomium-bearing muscovite. Viewed microscopically, fibrolitic sillimanite is partly replaced by topaz 

and is partly recrystallized to large grains of prismatic 

sillimanite (fig. 5); rutile is molded around topaz 

grains (fig. 6) and is intergrown with prismatic 

sillimanite (fig. 7). Thin seams of kaolinite were seen 

in thin sections of gneiss obtained from sample locality 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G7 

FIGURE 3.-Photomicrograph of elongate grains of rutile (R) 

alined parallel to foliation defined by planar alinement of biotite 

(B) in biotite-quartz-plagioclase gneiss from sample locality F 

(fig. 2). Other minerals are plagioclase (P), quartz (0), and 

apatite (ap). Plane-polarized light. 

H and from a small lens 1 km east-southeast of sample 

locality 33 (fig. 2). 

A local variant of the more common types of rutilebearing gneiss is a corundum-bearing sillimaniteplagioclase gneiss which occurs as lenses in rutilebearing biotite-quartz-plagioclase gneiss at sample 

locality G and also 0.3 km northwest of sample locality 

29 (fig. 2). The sillimanite-plagioclase gneiss is a white 

or light-gray fine- to coarse-grained rock that is poorly 

FIGURI::. 4.-Photomicrograph of elongate grains of rutile (R) 

alined parallel to foliation defined by alinement of fibroliti~ sillimanite (fs) in sillimanite-quartz gneiss from sample localtty 25 

(fig. 2). Other minerals are quartz (0) and biotite (B). Planepolarized light. 

FIGURE 5.-Photomicrograph of fibrolitic sillimanite (fs) partly 

replaced by topaz (T) and partly recrystallized to prismatic si?imanite (S) in sillimanitic topaz-quartz gneiss from sample locality 

D (fig. 2). Other minerals are quartz (Q) and the rutile (R). Planepolarized light. 

foliated and texturally complex. Grains of pinkish to 

gray corundum, as long as 2.3 em, and aggregates of 

prismatic sillimanite, as muc? as 12 c?I long ~nd 1 em 

thick are diversely onented m a fme- to 

medi~m-grained matrix rich in plagioclase (albite, 

An6-8) and fibrolitic sillimanite. Rutile forms 1 to 2 

percent of the gneiss (mineral ~eparations and th~nsection modal analyses, 1,000 pomts each). At locahty 

G the corundum-bearing gneiss contains wagnerite, a 

rare magnesium fluophosphate (Sheridan, Marsh and 

others, 1971). Other constituents of the gneiss are 

muscovite, apatite, monazite, zircon, tourmaline, and 

FIGURE 6.-Photomicrograph of rutile (R) associated with topaz 

(T)in topaz-quartz gneiss from sample locality B (fig. 2). Other 

mineral is quartz (0). Plane-polarized light. 
G8 GEOLOGY AND RESOURCES OF TITANIUM 

FIGURE 7.-Photomicrograph of prismatic sillimanite (S) inter· 

grown with rutile (R) in sillimanite-quartz gneiss that occurs as a 

layer in sillimanitic topaz-quartz gneiss at sample locality D (fig. 

2). Other minerals are quartz (0), and biotite (B). Planepolarized light. 

locally, chlorite. The tourmaline is in small 

yellowish-brown to pale-greenish-blue grains having 

refractive indices that suggest the mineral to be 

dravite. Foliation in the sillimanite-plagioclase gneiss 

is commonly obscure in the outcrops, owing to the 

diversely oriented large grains of corundum and 

aggregates of prismatic sillimanite. The foliation, 

however, is well shown in some thin sections and is 

defined by elongate grains of plagioclase, aggregates 

of fibrolitic sillimanite, and oriented flakes of 

pale-brown biotite. Tiny anhedral grains of rutile are 

alined in rows parallel to this foliation. Larger grains 

of rutile are subhedral and are associated with 

corundum (fig. 8). 

Layered hornblende gneiss associated in many 

areas with the light-colored rutile-bearing gneisses 

typically contain sphene and magnetite-ilmenite but 

no rutile. One exception to this occurs at locality G, 

where the hornblende gneiss adjacent to rutilebearing light-colored gneiss also contains rutile in 

addition to sphene and magnetite-ilmenite. 

CHEMICAL COMPOSmON 

Chemical and spectrographic analyses of four 

samples of rutile-bearing sillimanitic topaz-quartz 

gneiss and of six samples representing other lithologic 

types of Precambrian metamorphic rock are shown in 

table 1. The localities from which the samples were 

obtained are indicated in figure 2. 

The analyses of rutile-bearing sillimanitic topazquartz gneiss show this to be a rather unusual rock, 

FIGURE B.-Photomicrograph of subhedral g~·ains of rutile (R) 

associated with blocky grain of corundum (C) in sillimaniteplagioclase gneiss from sample locality G (fig. 2). Other minerals 

are plagioclase ( P), fibrolitic sillimanite ( fs), biotite (B), monazite 

(M), and wagnerite (W). Plane-polarized light. 

for it is rich in silica (63-76 percent), alumina (18-27 

percent), and fluorine (4-7.5 percent) and contains 

1.47-2.76 percent titanium oxide. The rock contains 

little iron, alkali metals, and alkaline earths, reflecting 

the fact that, unlike many other quartz-rich rocks of 

the Front Range, it contains no magnetite, ilmentite, 

or garnet and very little biotite and feldspar. Small 

amounts of CaO and P2 0 5 are present as accessory 

apatite, and small amounts of zirconium are present as 

accessory zircon. Small amounts of rare earths may be 

in monazite. Although monazite was not identified in 

thin sections of topaz-quartz gneiss, it has been 

found as an accessory mineral in other types of 

rutile-bearing gneiss. Small amounts of chromium are 

in green chromium-bearing muscovite found as thin 

laminae in some of the sillimanitic topaz-quartz gneiss. 

A sample of material rich in this green mica from 

sample locality H (fig. 2) contains 0.2 percent Cr20a, 

as determined by J. S. Wahlberg, U.S. Geological 

Survey, by X-ray fluorescence. 

The petrography of the rutile-bearing sillimanitequartz gneiss indicates high silica and alumina, 

accessory titania, and very little of any other 

constituents. The rutile-bearing biotite-quartz-plagioclase gneiss is somewhat richer in Na and poorer in Ca 

than other biotite gneisses of the east-central Front 

Range. Also, it probably is richer in Mg and poorer in 

Fe than most other biotite gneisses. Corundumbearing sillimanite-plagioclase gneiss is an aluminarich rock also characterized by high Na and Mg 

relative to Ca and Fe. 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G9 

TABLE 1.-Analytical data for rutile-bearing gneiss and for other Precambrian metamorphic rocks, east-central Front Range, Colorado 

Rock type .... Rutile-bearing sillimanitic topaz-quartz gneiss1 Other Precambrian metamorphic rocks 2 

Sample No. 1(A) 2(B) 3(C) 4(D) 5 6 7 8 9 10 

Laboratory 

serial no ... D102280 D102281 D102282 D102283 P127511W D127512W D127516W D127517W D127518W D127519W 

Field no .... R-22A R-23A R-24A R-25A S-C-6 S-C-7 S-C-11 S-C-13 S-C-14 S-C-15a 

Chemieal analyses (weight pereent) [Analyses of sample 1-4 are standard rock analyses by Elaine L. Munson. Analyses of samples 5-10, except for fluorine determinations, are rapid-rock analyses by Paul Elmore, Samuel Botts, Gillison Chloe, John Glenn, Lowell Artis, and Hezekiah Smith. Fluorine determinations in samples 5-10 are by Johnnie Gardner and Adolph Haubert using specific ion electrode method. All analysts are afflliated with the U.S. Geological Survey. Dashed line in table indicates no data] 

Si02 ....... 67.36 76.02 73.31 78.6 78.3 74.0 44.3 44.2 48.1 

Al20a ...... 23.57 18.01 20.65 26.99 13.9 12.8 13.1 13.7 17.8 15.0 

Fe20a ..... .01 .13 .09 .22 .29 .68 1.0 4.8 2.4 2.0 

FeO ....... .10 .08 .09 .12 1.1 3.2 1.6 2.4 21.8 8.2 

MgO ....... .01 .01 .04 .11 2.7 1.5 .55 2.0 8.9 4.1 

CaO ....... .28 .31 .31 1.10 .39 .09 1.8 21.0 .31 14.8 

Na20 ...... .02 .07 .05 .11 .97 .13 3.7 1.5 .76 2.9 

K20 ....... .03 .05 .12 .18 .80 1.6 3.1 2.8 .33 .85 

H20+ ..... .41 .61 .61 .59 .85 .80 .42 .33 1.2 .68 

H20- ..... .04 .08 .05 .05 .15 .05 .05 .10 .10 .07 

Ti02 ....... 2.76 1.47 1.47 2.71 .05 .49 .21 1.9 1.5 1.8 

P20s ...... .23 .26 .23 .87 .00 .00 .06 .82 .12 .35 

MnO ....... .01 .02 .02 .02 .00 .00 .07 .28 .43 .13 

C02 ....... .02 .01 .01 .01 <.05 <.05 .12 4.0 <.05 .92 

Cl ......... .00 .00 .00 .00 . . .. . . . . . . . . . ..... . . . . . . ...... . ..... F .......... 7.50 4.00 4.35 5.80 .07 .15 .07 .08 .12 .09 

Subtotal 102.35 101.13 101.40 102.25 

LessO .. 3.16 1.68 1.83 2.44 

Total ... 99.19 99.45 99.57 99.81 100 100 100 100 100 100 

Semiquantitative spectrographic analyses (parts per million)3 

[Analyses of samples 1-4 by R. H. Heidel, U.S. Geological Survey. Analyses ofsamples 5-10 by G. W. Sears, Jr., U.S. Geological Survey] 

Ba 7 7 70 150 150 

Be N N N N 2 

Ce N N N 300 N 

Co N N N N N 

Cr 70 15 7 10 1 

Cu 70 3 3 7 <1 

Ga N 5 5 5 20 

La N N N 150 30 

Nb L L 10 L N 

Nd N N N 200 N 

Ni N N N N N 

Ph L N N N 15 

Sc 10 5 15 30 N 

Sr 7 N 7 15 70 

v 70 30 30 70 N 

y 30 10 30 70 20 

Yb 1 2 3 7 3 

Zn N N N N N 

Zr 300 150 150 700 70 

1An samples are splits of bulk samples, originally about 50 pounds (22.7 kg) in the 

table each. Each of the bulk samples was obtained by taking a composite sample across the exposed width of the rutile-bearing gneiss. Localities are shown in figure 2. These 

localities, indicated in the table by letter symbols, (A) through (D) following the sample numbers designate localities from which two or more samples were taken and are shown 

in ~igure 2 by the letter symbols only. All samples are grab samples. Localities are shown in figure 2. The lithology represented by each of these samples is as follows: Sample 5, Biotite-quartz-plagioclase gneiss containing cordierite and sillimanite; 6, Sillimanitic biotite-quartz gneiss; 7, Microcline-quartz-plagioclase-biotite gneiss; 8, Calc-silicate gneiss; 9, Gedritecordierite-garnet gneiss; 10, Hornblende gneiss. 

Analyses of six other Precambrian metamorphic 

rocks are given in table 1 to illustrate the 

300 500 300 30 50 

N 1 N N N 

N N N N N 

10 N 20 15 50 

30 1 150 30 150 

50 N 5 1 30 

30 20 20 20 20 

50 N 30 N N 

10 10 10 N N 

N N N 

10 N 50 15 30 

N 15 10 N N 

15 7 20 30 30 

7 70 ,30Q 5 300 

70 N 150 200 300 

20 70 30 15 30 

3 7 <3 <3 <3 

N N N 300 N 

150 200 150 20 70 

3Minor elements were determined by semiquantitative spectrographic methods 

described by Myers and others (1961). Results of the spectrographic analyses are to be 

identified with geometric intervals having the boundaries 1200, 830, 560, 380, 260, 180, 120, etc., in parts per million but are reported arbitrarily in the table by approximate geometric midpoints such as 1000, 700, 500, 300, 200, 150, 100, etc. Precision of a reported value is approximately plus-or-minus one interval at 68-percent confidence, or plus-or-minus two intervals at 95-ercent confidence. N, not detected at limit of 

detection; L, detected but below limit of determination; .. , not looked for. 

composition of some of the other lithologies in the area 

of rutile-bearing gneisses. Samples 5, 6, and 7 

represent, respectively, cordierite-bearing sillimanitic 

biotite gneiss, sillimanitic biotite gneiss, and feldspar-
G10 GEOLOGY AND RESOURCES OF TITANIUM 

rich gneiss; they contain only 0.05 to 0.49 percent 

Ti02. Samples 8, 9, and 10 represent, respectively, 

calcsilicate gneiss, gedrite-cordierite-garnet gneiss, 

and hornblende gneiss; they contain 1.5 to 1.9 percent 

Ti02, amounts that are comparable to Ti02 in some 

rutile-bearing sillimanitic topaz-quartz gneiss. Except 

for a rare occurrence of rutile in hornblende gneiss at 

locality G, no rutile has been observed in these rocks. 

Petrographic studies of hornblende gneiss and 

calc-silicate gneiss indicate that sphene and 

magnetite-ilmenite are common accessory minerals 

and probably account for much of the Ti02 reported. 

Opaque iron oxides in gedrite-cordierite-garnet 

gneiss may be ilmenite or magnetite-ilmenite. Some of 

the titanium in these rocks probably is in biotite, 

amphibole, and other minerals but detailed analytical 

studies of minerals have not been made. The fluorine 

content of samples 5 through 10 ranges from 0.07 to 

0.15 percent, or 700 to 1,500 ppm. This range falls 

within the range, 60 to 1,500 ppm, reported by 

Fleischer and Robinson (1963, p. 63) but is higher than 

the average, 380 ppm, of 69 analyses of metamorphic 

rocks compiled from the literature. 

GEOCHEMISTRY OF RUTILE 

String~nt regulations imposed by the Office of 

Emergency Planning concerning chemical impurities 

in rutile and the lack of published information on trace 

elements in rutile prompted a study of rutile 

specimens from the Evergreen locality and several 

other localities where similar environments are found. 

Twenty-nine samples of rutile from the east-central 

part of the Front Range, and eleven samples 

from three other United States localities were 

anlayzed spectrographically and the results are 

reported in table 2. These analyses show the 

similarities of trace-element content in rutile samples 

from similar environments in several areas of the 

United States and also show chemical impurities. A 

table of impurities permitted in rutile is used to 

demonstrate the usability of rutile from high-grade 

metamorphic environments. Following is a discussion 

of factors influencing the substitution of these trace 

elements in the rutile structure. 

The rutile samples analyzed in this report, with the 

exception of crystals from Graves Mountain, Ga., 

were separated from whole rocks. Each Graves 

Mountain, Ga., sample is from large crystals that were 

sent to us by Mr. P. Bennett of Aluminum Silicates 

Inc., Washington, Ga. The rock samples were 

crushed, ground, washed, and sieved to -65, + 150 

mesh and then separated into light and heavy 

fractions by heavy liquids (bromoform). The heavy 

fraction was separated magnetically, and the 

nonmagnetic fraction was examined for rutile. The 

heavy nonmagnetic fraction commonly contains 

kyanite, andalusite, sillimanite, and topaz as well as 

rutile. Rutile grains were carefully hand-picked under 

a microscope and analyzed spectrographically. Most of 

the rutile in the whole-rock samples was in small 

anhedral grains, less than 0.5 mm across, and the color 

varied from black to pale orange-yellow. A few 

euhedral doubly terminated stubby prisms were seen, 

some of which exhibited the typical "knee shaped" 

rutile twins. Color is not consistent with a given 

sample and two or more colors are often present. 

Impurities in the analyzed rutile ranged from iron, 

found in all samples, to cobalt, found only two. The 

maximum impurities permitted in rutile purchased by 

the United States Government are listed in table 3 as 

stipulated by the Office of Emergency Planning. 

Although a number of analyzed samples exceeded the 

limits for one or more of the listed impurities, many of 

these are due to sample contamination rather than 

impurities in the rutile. Calcium and magnesium are 

considered contaminants for two reasons: they do not 

fit into the rutile structure and they are not present in 

the single crystals from Graves Mountain, Ga. 

Zirconium was present in all samples analyzed except 

those from Graves Mountain. Zirconium can 

substitute for titanium but most zirconium 

contamination of the samples is probably due to 

zircon. Zircon was observed in most of the heavy, 

nonmagnetic fractions. Some of the samples from the 

east-central Front Range contained lanthanum. A 

comparison of samples 1(A) and 4(D) in tables 1 and 2 

indicates that the lanthanum is an impurity probably 

caused by monazite contamination. Small amounts of 

. monazite were observed in the rocks. Antimony, 

tungsten, colbalt, and bismuth were also found in the 

analyzed rutile samples, although no standards of 

purity for these elements are given. 

Most of the trace elements found in the analyzed 

samples can substitute into the rutile structure. These 

substitutions can be influenced by several factors 

(table 4). One element can substitute extensively for 

another, in this case titanium, if their atomic radii do 

not differ by more than 15 percent. If the radii differ 

by more than 15 percent, but the valence of the 

substituting ion is within one unit (Ti +4 ) , then some 

substitution may occur (Krauskopf, 1967, p. 585). 

Substitution may also occur if the ratio of the 

substituting ion to the ion being substituted for 

(titanium) is within limits determined by the 

structure of the mineral involved (Pauling, 1929). This 

ratio is expressed by RAIRx where RA is the radius 

of the substituting metal ion and R x is the radius of 

the coordinating anion. Minerals having the rutile 
Sample 

No. 

TABLE 2.-Semiquantitative spectrographic analyses rutile 

[Analyses of samples R-1 to R-4, R-6 and R-7 by A. L. Sutton. All other analyses by E. 0. Mosier. Elements were determined by semiquantitative spectrographic methods described by Myers and others (1961). Results of the spectrographic analyses are to be identified with geometric intervals having the boundaries 1200, 830, 560, 380, 260, 180, 

120, etc.in parts per million but are reported arbitrarily in the table by approximate geometric midpoints such as 1000, 700, 500, 300, 200, 150, 100, etc. Precision of a reported 

value is approximately plus-or-minus one interval at 68-percent confidence, or plus-or-minus two intervals at 95-percent confidence. N, not detected at limit of detection. L, detected but below limit of determination. Localities in Colorado are shown on figure 2. Those localities indicated on the table by letter symbols (A) through (H) after sample numbers designate localities from which two or more samples were taken and are shown on figure 2 by the letter symbols only. Other localities are indicated by numbers) 

Rutile from Evergreen area, east-central Front Range, Colo. 

Main rutile-bearing gneiss North Beaverbrook 

I ll(A) 12(A) 13(D) 14(D) 15 16(C) 17(B) 18 19 20(C) 21(D) 1(A) 4(D) 22(E) 23(F) 24(F) 25 26(E) 

Field No. I R-1 R-2A R-3 R-4 R-5 R-6 R-7 R-9 R-11 R-13 R-14 R-22A R-25A NBB-1 NBB-3 NBB-4 NBB-9 NBB-11 

Fe 

J;rcent 0.3 0.5 0.5 0.5 1.0 0.5 0.7 0.7 0.7 0.5 0.7 0.5 0.5 0.3 0.3 0.1 0.2 0.2 

J'aercent 0.01 0.015 0.03 0.015 0.015 0.03 0.007 0.005 0.015 0,01 0.01 0.002 0.02 0.0005 0.015 0.01 0.03 0.02 

percent 1.0 1.5 1.5 0.5 ........ 0.5 0.7 0.7 L 0.05 0.2 "'0.5 0.1 L 0.02 0.02 0.015 0.2 0.015 

Ag N N N N L N N 1 N 1 1 N 1 N N N N N B N N N N N N N N N N N N N N N N 50 N 

Be N N N N N N N N 1 N N N N N N N N N 

Bi N N N N N N N N N 15 N N 10 N N N N N 

Co N N N N N N N N N N N N N N N N N N 

Cr 200 20 10 50 30 500 300 20 70 20 15 200 20 70 N 50 N 20 

La 2,000 200 L 500 150 1,000 L N 100 N 200 N N N N N 300 100 

Mo 3 3 2 N N 3 20 20 20 15 10 15 N 30 N 10 N 15 

27(E) 

NBB-12 

0.5 

0.002 

L 

N 

N 

N 

N 

N 

30 

N 

20 

Nb 500 700 500 500 2,000 500 1,500 "'10,000 5,000 700 500 700 50 2,000 1,000 1,000 700 1,000 ....... 10,000 

Sb N N N N N N N N N N N N N N N N N N N 

Sn 70 300 200 200 150 150 200 200 150 100 200 50 150 200 150 70 200 200 200 

v 1,000 300 150 500 200 700 200 700 1,000 700 500 1,000 200 1,000 500 2,000 700 700 200 

w N N N N 2,000 12~ N 1,000 500 500 700 500 300 200 L 100 300 200 y 200 50 100 200 150 50 30 50 50 70 10 50 200 70 150 300 500 150 

Zr 1 000 3 000 3 000 3,000 1500 1500 1 500 1,500 1,000 1,000 1000 1,000 N 1,500 1,500 1,000 1,000 2,000 -w.ooo 

Rutile from Evergreen area, east-central Front Range, Colo.-Continued Rutile from other United States localities 

Sante Fe Mountain Troublesome Turkey Creek Graves Mountain, Ga. Yuma County, Ariz. Santa Cruz County, Ariz. Gulch 

Sample I No. 28(G) 29 30(G) 31(G) 32 33 34(H) 35(H) 36(H) 37(H) 38 39 40 41 42 43 44 45 46 47 48 

Field No.I SF -2 SF-3 SF-6 SF-12 SF-17 TG-4A TC-2 TC-3 TC-4 TC-5 706 707 1 2 OMC-12 OMC-13 OMC-17 OMC-19 DC-1 DC-2 DC-3 

Fe 

percent 0.5 0.15 0.1 0.2 0.15 0.3 0.05 0.3 0.2 0.5 0.5 1.5 1.0 1.0 1.5 2.0 1.0 2.0 0.7 0.5 1.0 

Mg L 0.007 0.007 0.015 0.003 0.01 0.001 0.005 L L 0.00,7 0.001 0.05 0,07 0.01 0.05 0.002 0.002 0.002 percent 0.03 0.01 

Ca percent O.Dl 0.07 L 0.03 0.02 0.15 L 0.02 0.01 0.015 L L L L 0.05 0.05 0.05 0.15 L L L 

Ag N N N N N N N N N L N 5 2 2 1 1 N N N 

B N N N N N N N N N N N N N N 30 30 20 20 N N N 

Be N N N N N N N L N N N N N N N N N N 5 7 5 

Bi N N N N N 300 15 N 10 N N N N N N N N N 30 30 20 

Co N N N N N N N N N N N 30 15 N N N N N N N 

Cr 100 70 70 N 10 50 1,500 30 50 50 100 50 1,000 200 70 20 50 20 70 100 100 

La N N N N N 200 N N N 500 N N N N N N N N N N N 

MO N 15 30 N 10 N N N 10 10 N N 10 10 50 70 20 30 30 20 150 

Nb ...... 5,000 1,000 1,000 700 500 2,000 500 ........ 7,000 2,000 ...... 5,000 700 700 700 700 300 500 50 300 700 500 1,500 

Sb N N N N N N N N N N 300 200 300 300 2,000 1,000 1,000 2,000 200 200 1,500 

Sn 500 50 150 200 150 100 300 200 200 200 500 700 1,000 1,000 200 150 150 200 150 200 500 

v 300 500 500 300 700 300 700 1,500 500 300 700 700 2,000 2,000 500 500 500 500 1,000 1,000 500 

w 1,500 100 300 1,000 700 1,000 500 300 200 100 100 100 500 300 300 300 200 200 300 200 3,000 

y 20 20 50 20 15 I 20 N 500 200 150 N N 15 20 20 30 N 30 20 20 20 

Zr 2,000 1,000 700 1,000 1,500 700 700 1,000 1,500 2,000 N N N N 300 300 100 300 700 500 1,000 

!:0 

§ 

t"" 

t_:l:j 

z 

~ 

z 

t_:l:j 

-

00 

00 

~ t:l 

!:0 

t_:l:j 

~ ~ 

t_:l:j 

t:l 

~ a 

~ 

sn 

~ 0 

z 

~ 

~ z 

~ 

~ 

a 

0 

t"" 

0 

!:0 

E; 

0 

C) 

1-' 

1-' 
G12 GEOLOGY AND RESOURCES OF TITANIUM 

Table 3.-Standard of purity of rutile 

[From National stockpile purchase specifications P-49-R5 (National Materials Advisory 

Board, 1972)] 

Weight percent 

Impurity impurity permitted 

Fe~3-....................................... 1 

Nh203....................................... .4 

Zr02......................................... 1 

V205 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 

Cr2·03 _....................................... .75 

MgO+CaO... .. . . .. . . . . . . . . .. . . . . .. . . .. . . . . . . . .25 

Sn............................................ .1 

Mn ........................................... .75 

structure have radius ratios (RA!Rx) ranging from 

0.41 to 0.73 for the octahedrally coordinated cations. 

In the rutile structure each cation is coordinated to six 

anions, and each anion forms a ligand to three cations. 

In the case of rutile, R x (for oxygen with a 

coordination number of three) equals 1.36A (Shannon 

and Prewitt, 1969) and R A (for titanium with a 

coordination number of 6) equals 0.61A (Shannon and 

Prewitt, 1969). This gives a radius ratio of 

RA/Rx=0.61/1.36=0.45. Other octahedrally coordinated cations whose radii fall between the limiting 

radius ratio values of 0.41 and 0. 73 can also 

substitute into the rutile structure. All but one of the 

elements listed in table 3 have radius ratios within the 

limits of the rutile structure and probably substitute 

for Ti in rutile. A fourth factor than can affect 

substitution into the rutile structure is that most of 

the trace elements found in the analyzed rutile belong 

to the transition elements and are related to titanium. 

All the trace elements listed in table 3 satisfy one or 

more of the factors for substitution. Chrome, iron, 

molybdenum, niobium, and vanadium satisfy all four 

and all but chrome and molybdenum are found in 

every sample analyzed (table 2). These five elements 

also make up most of the trace elements found. A 

second group of elements found in trace amounts in 

rutile satisfy three of the four listed factors: tin, 

tungsten, yttrium, and zirconium. Elements satisfying 

Table 4.-Ionic subsitution factors 

[Elements are listed in order of decreasing likelihood of substitution] 

Valence Ionic radius Radius ratio Transition 

Element (Ti+4) ± 15 percent= 0.52 to 0.70 RA!Rx element 

Titanium Ti +4 0.61 0.45 Yes 

Iron Fe +3 .64 .47 Yes 

Niobium Nb +3 .70 .51 Yes 

Vanadium v +4 .59 .43 Yes 

Chrome Cr +3 .62 .45 Yes 

Molybdenum2 Mo+4 .64 .48 Yes 

Tin Sn +4 .69 .51 No 

Tungsten w+4 .58 .43 Yes 

Yttrium y +3 .89 .66 Yes 

Zirconium y +4 .72 .53 Yes 

Antimony Sb +3 .77 .57 No 

Cobalt Co +2 .73 .54 Yes 

Bismuth Bi +3 1.02 .75 No 

only two of the factors are much less common and are 

unevenly spread throughout the samples. Cobalt 

occurs in only two samples, whereas antimony occurs 

in the rutile from all localities except the east-central 

Front Range. Bismuth satisfies only the valence 

factor. 

ORIGIN OF MEfAMORPIHC ROCKS 

We believe that the thick section of metamorphic 

rocks in the east-central Front Range was originally 

an assemblage of inter layered shales and graywackes, 

and local carbonate layers, associated with abundant 

mafic and felsic volcanic rocks which probably 

accumulated near their source. Although the origin of 

the thin lenses and layers of rutile-bearing gneiss is 

debatable, we believe that most likely they were 

originally the products of intense subaerial 

weathering that occurred during the accumulation of 

the thick succession of sedimentary and volcanic 

rocks. 

MAJOR LITHOLOGIC GROUPS 

The numerous varieties of metamorphic rock in the 

five principal map units shown in figure 2 comprise 

three major lithologic groups: biotite gneiss (units A 

and B), hornblende gneiss and amphibolite (units C 

and D), and feldspar-rich gneiss (units C and E). 

Biotite gneisses and schists in the Front Range were 

considered to be metamorphosed shaly sediments 

(Ball, in Spurr, Garrey, and Ball, 1908, p. 44) and 

subsequent authors have reached the same 

conclusions. Features that correspond to many 

present-day successions of sedimentary rock are the 

wide areal extent of these rocks, the lithologic 

variation across layers, close interlayering, the apparently conformable contacts, and the composition. 

Relict sedimentary features are present in some 

areas, for conglomeratic lenses were noted in mica 

schist (a lithologic unit traceable laterally to biotite 

gneiss of this report) in the Ralston Buttes quadrangle 

(Sheridan, Maxwell, and Albee, 1967, p. 10), and 

conglomeratic quartzite is interlayered with quartzite 

and schist in the Coal Creek area (Wells and others, 

1964, p. 7-8). In accordance with all these 

investigators, we interpret the biotite gneiss of the 

report area as metasedimentary. The sillimanitic 

biotite-quartz gneiss was an alumina-rich shale and 

the intimately interlayered biotite-quartz-plagioclase 

gneiss was a sandy shale or graywacke. The 

sillimanitic biotite gneiss containing cordierite- and 

garnet-bearing layers was an alumina-rich shale 

having some layers relatively rich in magnesium and 

iron. Gable and Sims (1969, p. 57-59) have also 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G13 

ascribed a metasedimentary origin to similar 

cordierite-bearing rocks in the Front Range. 

Hornblende gneiss and amphibolite very likely are 

metamorphosed intermediate to basic tuffs and flows, 

and the commonly associated calc-silicate gneiss and 

impure marble were once sedimentary rocks ranging 

from calcareous shale to argillaceous limestone. 

Quartz gneiss, commonly containing magnetite and 

garnet, is a metamorphic rock equivalent to one type 

of iron formation. 

The feldspar-rich gneisses are thought to have been 

felsic volcanics. Hedge (1969, p. 12, 120-123) noted 

that their chemical composition favors an origin as 

acid volcanic rocks similar to some found in island arc 

association with basalts. Some authors (Moench and 

others, 1962, p. 38; Sheridan, Maxwell, and Albee, 

1967, p. 23) have postulated a metasedimentary 

origin. Sedimentary features and a rock of volcanic 

composition are not necessarily incompatible; parts of 

the feldspar-rich gneiss are probably metavolcanics, 

but other parts were formed by metamorphism of 

sedimentary tuffs and volcaniclastic rocks. 

RUTILE-BEARING GNEISS 

We believe that the light-colored rutile-bearing 

gneisses of the east-central Front Range originated by 

intense weathering of intermediate to basic tuffs and 

flows. This resulted in thin layers of bentonitic clays 

enriched in titania (leucoxene), alumina (clay), and 

silica (clay and quartz). These weathering products 

were reworked by surface waters, and fluorine, 

emanating from volcanic sources, was adsorbed locally. Clays produced by weathering are commonly low 

inCa and high in A1 and Ti (Rankama and Sahama, 

1950, p. 209, 563). Rankama and Sahama (1950, p. 764) 

stated that fluorine is strongly adsorbed in soils, 

bentonite, and bottom muds and that fluorine is added 

to the "exogenic cycle by volcanic processes." 

Serdyuchenko (1968) believes that many schists and 

gneisses containing sillimanite, kyanite, or corundum 

in numerous occurrences around the earth are 

metamorphosed kaolinite-bauxite weathering crusts. 

Dunn (1929, p. 248) thought that some of the 

kyanite-quartz rock in India was originally a surface 

decomposition of basalt to bauxitic clay. Espenshade 

and Potter (1960, p. 24-25) concluded that kyanite 

quartzite in the Farmville district, Virginia, and 

kyanite quartzite and sillimanite quartzite in the 

Kings Mountain district, North Carolina-South 

Carolina, originated from sediments composed of 

quartz sand containing clay or bauxite. 

In the east-central Front Range the intergrading 

and int~rlensing of several varieties of rutile-bearing 

gneiss and their variability in rutile content, from 

trace amounts to over 5 percent, are best explained by 

reworking of the original weathered materials. We 

believe that fluorine from volcanic emanations or from 

fluorine-rich volcanic rocks was introduced locally into 

these weathered materials during or shortly after 

reworking. 

In a preliminary report (Sheridan, Taylor, and 

Marsh, 1968, p. 6), we postulated that rutile-bearing 

sillimanitic topaz-quartz gneiss was formed by the 

action of fluorine metasomatism on a gneissic 

progenitor, such as a sillimanitic quartz-rich gneiss. 

Such metasomatism seemed necessary to explain the 

high fluorine content of the gneiss and to account for 

textural relations indicating that topaz, prismatic 

sillimanite, and rutile formed at the expense of a 

previously formed regional metamorphic suite (see 

figs. 5, 6, and 7 of this report). However, as R. H. 

Moench (oral commun., 1973) observed, the textural 

relations do not demand a separate later metamorphic 

event, because the principal regional metamorphism 

may have continued long enough after the two early 

stages of folding to cause the observed textural 

features. The relations suggest redistribution of 

primary amounts of fluorine within the affected layers 

during regional metamorphism, not a metasomatic 

event related to some later plutonic episode. 

OTHER LOCALITIES OF ROCK TYPES 

SIMILAR TO THOSE IN THE 

EAST-CENTRAL FRONT RANGE 

Many terranes in the United States and throughout 

the world contain rock types similar to the Evergreen 

occurrence. Rutile is reported from many of these 

occurrences and, although they are low-grade deposits 

(1-4 percent rutile content), they form a potential 

resource. The rocks are reported as metasediments, 

metavolcanics, or metamorphosed weathering crusts, 

the metamorphism being regional or contact. 

Although the age of the metamorphosed deposits 

ranges from Precambrian to Mesozoic, most of 

reported deposits are in Precambrian rocks. The 

mineralogy of these rocks is remarkably similar -

chiefly quartz, aluminum silicate (andalusite, kyanite, 

and sillimanite) and a variety of accessory minerals. 

Rutile is present as disseminated fine grains and as 

scattered larger crystals. Topaz is common and is 

locally abundant, as in localities described in this 

report. Phosphate minerals such as apatite, monazite, 

lazulite, and wagnerite are commonly found. Other 

accessory minerals found but not universally present 

are pyrophyllite, ilmenite, magnetite, tourmaline, 

pyrite, chrome-bearing mica, and zircon. Pegmatites 

are common in these areas but are younger and do not 
G14 GEOLOGY AND RESOURCES OF TITANIUM 

display the distinctive mineralogy of the rutilebearing units. Several of the known occurrences of 

rutile-bearing rocks are described below. 

FARMVILLE DISTRICT, VffiGINIA 

In the Farmville district of central Virginia 

(Espenshade and Potter, 1960, p. 34-53), layers of 

rutile-bearing kyanite quartzite in Precambrian rocks 

occur in a northeast-trending belt about 8 km wide and 

50 km long. Individual layers range in thickness from a 

few metres to as much as several hundred metres 

where repeated by folding. A percent or less rutile is 

disseminated in the kyanite quartzite as small grains 1 

mm across or smaller. As much as 1 percent of topaz is 

present locally. Principal associated rock types are 

hornblende gneiss and biotite gneiss, both containing 

small amounts of rutile. The chemical nature of these 

units indicates that they probably were originally 

graywackes and clay-bearing sandstones interspersed 

with basaltic or andesitic lava flows. The Farmville 

district accounts for 50 percent of the known kyanite 

resources in the southeast United St~tes and, at 0.5 to 

1 percent rutile, represents a potential titanium 

resource. 

KINGS MOUNTAIN DISTRICT, 

NORTH CAROLINA-SOUTH CAROLINA 

In the Kings Mountain district located on the border 

between North Carolina and South Carolina about 40 

km west of Charlotte, N.C. (Espenshade and Potter, 

1960, p. 64-94), rutile occurs as a common accessory in 

kyanite quartzite and sillimanite quartzite. These 

units form the upper part of a complexly folded series 

of schists and gneisses which are dominantly biotite 

schist and gneiss and hornblende gneiss. These schists 

and gneisses have been derived principally from 

volcanic rocks. In the kyanite quartzite the rutile is 

evenly disseminated as small grains and crystals. No 

topaz has been reported from this unit but lazulite and 

tourmaline are rare accessories. The kyanite quartzite 

layers range in thickness from 6 to 10 m but appear 

thicker where repeated by folding. 

Rutile is an abundant accessory in the sillimanite 

quartzite. This unit ranges in thickness from 3 to 9 m 

and where undeformed extends along strike as much 

as 900 m. Topaz is a rare accessory and lazulite is 

locally abundant. The sillimanite quartzite may 

represent a later more intense metamorphism of 

kyanite quartzite. Both units are sedimentary in 

origin; probably they were clayey sandstones. The 

Crowders Mountain-Henry Knob area and the Reese 

Mountain-Clubb Mountain area are the most 

important in the district and they account for 40 

percent of the known kyanite resources in the 

southeast United States and represent a potential 

rutile resource. 

GRAVES MOUNTAIN, GEORGIA 

Some of the finest rutile specimens in the world 

come from northeast Georgia at Graves Mountain 

(Hurst, 1959). The rutile occurs in sericite-kyanitequartz rock and is most abundant in the coarse 

kyanite-quartz facies cropping out along the top of the 

mountain. The rutile occurs as small individual 

disseminated grains and occa$ionallarger crystals and 

constitutes 0.5 to 1 percent of the rock. Topaz has not 

been reported from the kyanite-quartz rock, but 

pyrophyllite and lazulite are common accessories. 

Some zones contain as much as 15 percent lazulite. 

The kyanite-quartz rock crops out in large lenticular 

bodies as much as 120 m wide and 550 m long and is 

associated with quartz sericite schist and quartz 

conglomerate. The Graves Mountain area is underlain 

by a thick sequence of metamorphosed volcanic and 

sedimentary rocks. The kyanite quartz rock was 

probably volcanic in origin, possibly a tuff and it 

belongs to the Little River Series of Crickmay (1952) 

which may be of Paleozoic age. The unit was folded 

and regionally metamorphosed to quartz-sericite 

schists early in its history. A period of fracturing 

followed the metamorphism and kyanite, lazulite, and 

rutile were deposited. A late-stage period of cross 

fractures developed with attendant deposition of 

pyrophyllite. Most of the rutile is found in a zone 30m 

wide and 150 m long and represents a small but 

definable resource. 

WIDTE MOUNTAIN, CALIFORNIA 

A commercial deposit of andalusite in Precambrian 

rocks of the Inyo Range near White Mountain, Calif., 

contains rutile (Kerr, 1932). Rutile also occurs in the 

surrounding quartz-sericite schist and quartz-micatourmaline schist. These units are thought to be a 

series of trachytic flows with an interlayering of some 

highly aluminous material (volcanic or sedimentary). 

All the metamorphic units were formed by contact 

metamorphisms by a quartz monzonite porphyry 

intrusive. A second stage of hydrothermal 

metamorphism acted on the area during the late 

stages of the intrusive producing the late 

mineralization of pyrophyllite and sericite and altering 

the quartz-sericite schist in many places to diasporequartz-pyrophyllite rock. The main andalusite deposit 

contains large zones of topaz-quartz, pyrite-quartzandalusite, and trolleite-scorzalite-augelite rock 

(Gross and Parwel, 1968). Rutile is disseminated 

throughout the andalusite body as well as the 

surrounding altered schists in small grains ( 0.1 to 3 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G15 

mm) and scattered larger crystals and is most 

abundant in the diaspore-quartz-pyrophyllite rocks. A 

chemical analysis of rutile from this rock (Gross and 

Parwel, 1969, p. 495) shows that it is relatively pure 

containing minor iron and vanadium and trace 

amounts of tin, chrome, and antimony. Niobium was 

not detected in the sample. These trace elements were 

probably included in the rutile from a magmatic 

source. The scarcity of titanium minerals in the 

unaltered surrounding schists suggest that the source 

of rutile mineralization was probably the quartz 

monzonite porphyry. Deposition of rutile occurred 

after topaz and andalusite and probably continued 

throughout both stages of metamorphism. The 

quantity of rutile present is difficult to estimate, 

inasmuch as no percentages or tonnages have been 

given, but rutile is present throughout the 

metamorphosed area, which covers approximately 2.5 

km2 of relatively high-relief terrane. 

YUMA COUNTY, ARIZONA 

A rutile-bearing kyanite quartzite on the west side 

of the Dome Rock Mountains in the NE 1

/4 of sec. 34, T. 

4 N., R. 21 W., in extreme western Yuma County, 

Ariz., was visited by Marsh in January 1970. The 

rutile occurs as small disseminated grains in kyanite 

quartzite and some larger crystals in small localized 

quartz veins. The rutile-bearing kyanite quartzite 

may be divided into two zones, a northerly belt of 

magnetite-rich quartzite and a southerly belt of 

rutile-bearing kyanite quartzite. These belts are not 

well defined and appear to grade one into the other. 

The rutile zone is approximately 900 m long and 150 to 

300m wide, strikes east, and has a northerly dip of 

about 60°. The rutile zone thickens somewhat to the 

east. The rutile occurs in clots of small grains. These 

clots have a roughly rectangular bladed shape and 

could possibly be relics from some former crystal, 

perhaps ilmenite. Lazulite is locally abundant and 

topaz and wagnerite are present. The texture of the 

rutile-bearing kyanite quartzite is porous and appears 

leached. The area is mapped by Wilson (1960) as 

Mesozoic schists, but similar rocks in the adjacent 

Quartzsite quadrangle have been mapped (Miller, 

1968) as Precambrian. Rocks in the area apparently 

were contact metamorphosed by a quartz monzonite 

probably of Mesozoic age (Wilson, 1960) adjacent to 

the rutile-bearing kyanite quartzite. Several samples 

were collected from the rutile-bearing kyanite quartzite, and four spectrographic analyses of rutile 

separated from these samples are listed in table 2. 

Estimates of the amount of rutile in the deposit have 

not been made, but the outcrop area is sufficiently 

large to make the area a potential resource. 

SANTA CRUZ COUNTY, ARIZONA 

Rutile-bearing quartzite occurs in a contact 

metamorphosed zone of Triassic volcanics ( dacitic and 

latitic flows) and sedimentary rocks (conglomerates, 

sandstones, and quartzites) (Drewes, 1971) in the 

Santa Rita Mountains on the east side of Madera 

Canyon in the NW1

/4 sec. 1, T. 20 S., R. 14 E., in 

northern Santa Cruz County, Ariz. Three samples of 

quartzite from this locality collected by Ed 

Montgomery of Duval Corporation show that 

andalusite is the common aluminum -silicate mineral 

and topaz, lazulite, and rutile are accessory. One 

sample contained as much as 10 percent topaz, 

suggesting fluorine metasomatism of the quartzite. A 

large area of Cretaceous granodiorite immediately 

adjacent to the area was probably responsible for the 

contact metamorphism. Spectrographic analyses of 

rutile separates from the three samples are listed in 

table 2. No accurate estimates of the amount of rutile 

in this area can be made at present, but the area of 

contact metamorphism is about 3 km long and 1 km 

wide. 

OTHER UNITED STATES OCCURRENCES 

Rutile-bearing gneiss has been reported in several 

other areas, an indication that primary rutile is more 

widely distributed in these types of metamorphic 

rocks than previously recognized. · 

Fine-grained and locally abundant rutile has been 

reported in an andalusite, kyanite quartzite of 

Precambrian age at Kiawa Mountain, N.Mex. 

(Heinrich and Corey, 1959). 

A kyanite mine on the western slope of the Cargo 

Muchacho Mountains, Imperial County, Calif., is 

reported to contain euhedral crystals of red rutile 

(Pemberton and Bideaux, 1968). The deposit occurs in 

metamorphosed quartz and arkosic sandstone of 

pre-Mesozoic, possibly Precambrian age. Mesozoic 

granitoid rocks metamorphosed the sediments. Local 

hydrothermal action followed intrustion (Henshaw, 

1942). 

WORLD OCCURRENCES 

The occurrence of rutile-bearing aluminum silicate 

rocks in other parts of the world is difficult to 

document. As with the United States occurrences, 

this rock type is noted in detailed descriptions of 

aluminum-silicate deposits, with rutile being 

mentioned as a minor part of the mineral assemblage. 

A few examples of this type of occurrence are briefly 

described here. 

Australia is the world's largest producer of rutile, 

and most of it comes from beach placers on the east 

coast. These deposits have developed through two 
G16 GEOLOGY AND RESOURCES OF TITANIUM 

stages of weathering and concentration; detritus from 

the Precambrian shield rocks were reconsolidated as 

Mesozoic rocks and then were reworked into the beach 

placers being mined today. This reworking of 

sediments served to concentrate the heavy minerals 

into simpler mineral assemblages because of 

weathering and removal of less-stable minerals, 

resulting in minable placer deposits consisting mainly 

of rutile and zircon. The probable source for the rutile 

was the crystalline rocks of the interior where rutile 

occurs in peJmlatitic veins and crystalline schists of 

Precambrian age (Whitworth, 1956, p. 34). Probable 

commercial amounts of rutile occur in the pegmatites 

of the A von district in Western Australia and at 

Myponga, Parra, and Radium Hill in South Australia. 

Rutile in the crystalline schists occurs mainly in South 

Australia in Blumberg, Yankalilla, and Williamstown. 

The rutile occurs disseminated and along bedding 

planes in biotite and sillimanite schists. In several of 

these occurrences rutile is a byproduct or impurity in 

the mining of aluminous refractory material. As much 

as 4 percent rutile occurs in a chlorite-corundum rock 

from Mount Painter, South Australia (Oliver and 

Jones, 1965). 

The Precambrian shield area of northern India 

contains numerous occurrences of biotite and 

sillimanite schists that contain disseminated finegrained rutile or small clots of rutile along bedding 

planes (Dunn, 1929). No report is made of the grade of 

rutile, but its occurrence is noted at many localities 

and it appears to be common in some. Accessory 

minerals are topaz, tourmaline, green micas, 

corundum, and magnetite. These rutile-bearing rocks 

are thought to be metavolcanic or metasedimentaryprobably basic lavas or bauxitic clays-in origin 

(Dunn, 1929, p. 243-252). 

In Sweden rutile occurs in three areas of 

Precambrian metamorphic quartzite (Geijer, 1964). 

The largest is at Haallsjoberget in southwest Sweden 

where rutile occurs as streaks and veinlets in kyanitebearing quartzite. Lazulite, iron-rich wagnerite, and 

pyrophyllite are also present. No size or grade figures 

are given, but rutile is reported as abundant in some 

of the kyanite concentrations. A similar but smaller 

deposit occurs at Dicksberget, 60 km south of 

Haallsjoberget. Here, quartzite with 15-25 percent 

kyanite has accessory rutile, ilmenite, lazulite, and 

pyrite. The third deposit is at Vastanaa near the 

southern Baltic coast where Precambrian quartzite 

contains commercially worked hematite deposits. 

Here, quartzite is overlain by alumina-rich mica schist 

containing kyanite, andalusite, and sparse sillimanite. 

Rutile is widespread and amounts to about 1 percent 

of the rock. Other accessory minerals include lazulite, 

zircon, and pyrophyllite, These occurrences are 

thought to be high-temperature replacement deposits 

of originally high-alumina and silica rocks. 

Serdyuchenko (1968), described several areas 

where rutile occurs with aluminum-silicate rocks. In 

south Norway at Arendal rutile occurs in amounts as 

great as 1 percent in corundum-bearing gneisses containing lazulite and sillimanite. In the Orange River 

Basin in Namaqualand, South-West Africa, rutile 

occurs as an accessory (1 percent) in sillimanite and 

sillimanite-corundum beds in metamorphic rocks. 

ECONOMIC POTENTIAL 

For reasons cited in the introduction, rutile deposits 

of the Evergreen area may never be mined. Data 

reported below illustrate resources that can be 

expected if continued search elsewhere discloses 

deposits of similar size and mineralogy. 

The sillimanitic topaz-quartz gneiss constitutes the 

most important type of rutile-bearing rock in the 

Evergreen area. The following computations are made 

from the layers of this rock from sample locality A to 

sample locality D (fig. 2), a strike length of 2,100 m. 

The unit is exposed to a depth of 73 m; the thickness 

ranges from 3 to 21m and averages 12m. Chemical 

analyses of four samples (1 to 4, table 2) were used to 

calculate average mineralogic grade: rutile, 2.1 

percent; topaz, 28.5 percent; sillimanite, 12.3 percent. 

The indicated resources, using a rock density of 3.00, 

are 5.5 million metric tons of sillimanitic topaz-quartz 

gneiss. These contain 115,000 metric tons of rutile, 

1,600,000 metric tons of topaz, 670,000 metric tons of 

sillimanite, and 3,115,000 metric tons of quartz. Each 

additional 30 m of depth contains the inferred resources: 47,000 metric tons of rutile, 646,000 metric 

tons of topaz, and 280,000 metric tons of sillimanite. 

Although the rutile is fine-grained (commonly 0.5 mm 

or less in size), laboratory tests show that much of it is 

freed in the crushing stage and much of the remainder 

is freed by grinding to 175 #J. m. 

Extending west-northwestward from the west end 

of the deposit described above (sample locality A, fig. 

2) is the Z-shaped trace of other rutile-bearing 

gneisses that contain 0.5 to 2.5 percent rutile. As 

measured along the trace, these are about 11 km in 

length and range in thickness from 30 em to 9 m. In the 

area to the southeast are several lenses of sillimanitic 

topaz-quartz gneiss that range in length from 60 to 800 

m and in thickness from 15 em to 8 m; the rutile 

content ranges from 0.5 to 3 percent. Other 

rutile-bearing layers typically contain less than 1 

percent rutile and are not considered to be a resource. 
RUTILE IN GNEISS AND RELATED ROCKS, FRONT RANGE, COLORADO G17 

REFERENCES CITED 

Bryant, Bruce, Miller, Rd. D., and Scott, G. R., 1973, Geologic map 

of the Indian Hills quadrangle, Jefferson County, Colorado: 

U.S. Geol. Survey Geol. Quad. Map GQ-1073 7 p. [1974]. 

Crickmay, G. W., 1952, Geology of the crystalline rocks of Georgia: 

Georgia Geol. Survey Bull. no. 58, 54 p. 

Drewes, Harold, 1971, Geologic map of the Mount Wrightson quadrangle, southeast of Tucson, Santa Cruz and Pima Counties, 

Arizona: U.S. Geol. Survey Misc. Geol. Inv. Map 1-614. 

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