UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

GEOLOGICAL, SURVEY CIRCULAR 

PRIELIMINARY SUMMARY FEVIEW OF THORIUM-BEARING 

MINERAL OCC-NCES IN ALASKA 

By Robert G. Bab and Welmuth Wedow, Jr. 

Thw report wncarna work done on behalf of the U. 8. Atomic Energy 

Cdon and ia published with 

the permhion of the Commineion 

Wmd-hgbn, D. C., 1963 

Free on amliation to the Geologid Survey, Wlahinotpn 26, D. C. 

PRELIMINARY S-Y Rl3VIEW OF THORIUM-BEARING 

MINERAL OCCURRENCES IN ALASKA 

CONTENTS 

Fage 

Abstract ..................................... 1 

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

Discussion of data.. .......................... 2 

Thorium-bearing minerals ............... 2 

Thorium occurrences worthy of 

possible further study .................. 3 

Salmon Bay area ................... 3 

Tobin Creek-Big Creek area.. ....... 4 

Manley Hot Springs district. ......... 4 

Eurekaarea, ................. 4 

Tofty tin belt.. ................ 4 

Hot Springs Dome area.. ....... 4 

Long area......,.................. 4 

Nixon Fork area. ................... 4 

Fage 

Discussion of data--Continued 

Thorium occurrences worthy of 

possible further study--Continued 

Buckland-Kiwalik district.. ......... 5 

Clem Mountain area.. ......... 5 

Hunter Creek-Connolly CreekFairhaven Creek area.. ...... 5 

Granite Mountain area. ........ 5 

Darby Mountains district ........... 5 

Tubutulik River area.. ........ 5 

Golovin Bay area.. ........... 5 

Cape Mountain area.. .............. 6 

Conclusions .................................. 6 

Literature cited.. ............................ 6 

ILLUSTRATICN 

Fage 

Flate 1. Map of Alaska showing location of thorium occurrences.. ......................... .Inside back cover 

TABLES 

Fage 

Table 1. General descriptio? of thorium-bearing minerals belonging to species that are found in Alaska ..... 2 

2. Cccurrences of thorium-bearing minerals in Alaska,. .......................................... 8 

ABSTRACT 

Thorium-bearing minerals are known at 47 localities in Alaska. At these localities the thorium 

occurs as a major constituent or in minor amounts as an impurity in one or more of the following 12 minerals: 

allanite, columbite, ellsworthite, eschynite, gummite, 

monazite, orangite, mrisite, thorianite, thorite, 

xenotime, and zircon. In addition other minerals, such as biotite and sphene, are rackioactive arld may contain 

thorium. Several unidentified niobate minerals with 

uranium or uranium and thorium as major constituents 

have been recognized at some localities. 

The distribution, by type of deposit, of the 47 

thorium occurrences is as follows: lode, 3; lode and 

placer, I; granitic rock, 3; granitic rock and related 

placer, 14; and placer, 26. Of the four lode occur - rences only the radioactive veins at Salmon Bay in 

southeastern Alaska and the contact metamorphic 

deposit in the Nixon Fork area of central Alaska 

warrant further consideration as possible commercial 

sources, although insufficient data are available to 

determine whether these two deposits have such 

possibilities. 

The remaining occurrences of thorium-bearing 

minerals in Alaska are limited to placer deposits and 

disseminations of accessory minerals in granitic rocks. 

In most of these occurrences the thorium-bearing 

minerals occur in only trace amounts and consequently 

warrant little further consideration. More data are 

needed to determine the possibilities of byproduct 

recovery of thorium-bearing minerals from several 

of the gold and tin placers. 

INTRODUCTION 

Before the beginning of the Trace Elements 

program of the Geological Survey in 1944, little was 

known about the occurrence of thorium-bearing 

minerals in Alaska. Mertie (1925, p. 26~)lreported 

the presence of monazite in the placers of Big Creek 

in the Chandalar district north of Fort Yukon. 

Eschynite, xenotime, and monazite were identified in 

the tin-bearing placers of the Manley Hot Springs 

district west of Fairbanks (Mertie and Waters, 1934, 

pp. 229, 239-240). Durinq World War I1 

'see pge 11 for list of liccrature cited. 

1 
J. H. Skidmore (1944) reported to the Union Mines 

Development Corp. on the radioactivity of various 

Alaskan placers; he noted that concentrates from mining 

operations on Sweepstakes Creek in the eastern Seward 

Peninsula were especially radioactive, Later work 

(Gault and others, 1946; Killeen and White, 1950) by 

the Geological Survey showed that the chief radioactive 

mineral in the concentrates from Sweepstakes Creek 

and other nearby streams is uranothorianite. 

Considerable information has been collected on 

the occurrence of thorium-bearing minerals during 

the course of the Survey's reconnaissance investigations for uranium in Alaska. All available data on 

thorium-bearing minerals in Alaska are now being 

compiled, and the purpose of this report is to present 

a preliminary surr,mary of the data compiled to date. 

The spectrographic and chemical analyses, and most 

of the radiometric analyses and mineral identifications 

used in this report, were made in the Trace Elements 

Section Washington Laboratory; a few of the radiometric analyses and mineral identifications were made 

by members of the Survey's Alaskan 'I'race Elements 

Unit. This work was done on behalf of the Division of 

Raw Materials of the U. S. Atomic Energy Comrr~ission. 

DISCUSSION CF DATA 

Thorium-bearing minerals 

Twelve minerals containing thorium, either 

as a major constituent or in minor amounts as 

an impurity, are known in Alaska, These 

minerals are allanite, columbite, ellsworthite, 

eschynite, gummite, monazite, orangite, par isite, 

thorianite, thorite, xenotime, and zircon. For 

the convenience of the reader, brief general 

descriptions of these minerals, summarized from 

Ford (1932), Frondel and Fleischer (1950), 

George (1949), and Falache and others (1951) are 

given in table 1. It should be emphasized that 

these mineral descriptions, particularly the 

thorium percentages, refer to mineral occurrences 

outside Alaska; few data are available on the 

thorium-bearing minerals in Alaska beyond the 

fact that their presence at a particular locality has 

been noted. In addition, other minerals, such as 

biotite and sphene, are radioactive and may contain 

thorium. Several unidentified niobate minerals with 

uranium or uranium and thorium as major constituents 

have been recognized at some localities. 

Table 1.--General description of thorium-bearing minerals belonging to species that are found in 

Alaska 

Mineral 

Hydrous silicate of 

aluminum, calcium, 

and the cerium metals 

Chemical composition 

Nlobate of iroq and 

manganese. 

Thorium 

(percent) 

Complex hydrous oxides 

of niobium, tantalum, 

sodium, calcium, with 

hydroxyl and fluorine 

may contain as much 

as 17 percent uranium 

Complex oxide of nlcbium, tantalum, and 

the rare earths with 

varying amounts of 

thorium and uranium. 

Uranium with minor 

amounts of thorium, 

lead, and hydroxyl. 

3are -earth phosphate 

with some thoria and 

silica. 

as much as 3 

much as 22 

Description 

Color: brown to black. 

Luster: resinous to submetallic. 

Fracture: uneven to subconchoidal. 

Habit: tabular, also Long and slender, 

also masslve. 

Specific gravity: 2.7-4.2. 

Color: black, grayish and brownish black. 

Luster: submetalllc to subresinous. 

Fracture: subconchoidal to uneven. 

Habit: short prismatic grains. 

Specific gravity: 5.2-7.9. 

Color: amber yellow to dark brown. 

Luster: adamantine. 

Fracture: subconchoidal to splintery, 

uneven. 

Habit: rounded grains, also massive. 

Specific gravity: 3.8-4.2. 

Color: brownish yellow to black. 

Luster: submetallic to resinous, nearly 

dull. 

Fracture: small conchoidal. 

Habit: mostly masslve, also prismatic. 

Specific gravity: 4.9-5.2. 

Color: orange, yellow, orange yellow. 

Luster: dull to greasy. 

Fracture: uneven to subconchoidal. 

Habit: massive, dense, also in rounded 

or flattened masses or crusts. 

Speclflc gravity: 3.9-6.4. 

CoLol: yellowish or reddish brown, golden 

yellow. 

Luster: resinous. 

Fracture: concholdal to uneven. 

Habit: small, often flattened grains. 

Specific gravity: 4.9-5.3. 
Thorium occurrences worthy of 

possible further study 

Table 1.--General description of thorium-bearing minerals belonging to species that are found in 

Thorium is known to be present because of the 

identification of thorium-bearing minerals, or assumed 

to be present because of discrepancies between equivalent uranium and uranium analyses, at 47 localities 

in Alaska. Fertinent data on these occurrences are 

given in table 2, p. 4. The distribution of the 47 

occurrences by type of deposit is as follows: 

Lode., ............................. 3 

Lode and placer.. ................... 1 

Granitic rock.. ..................... 3 

Granitic rock and placer. ............ 14 

Flacer only.. ........................ 26 

Mineral 

Oranglte------ 

Papisite------ 

Thorianite---- 

Thorite------- 

Xenotime------ 

Zircon-------- 

Thirteen of these localities may be worthy of further 

study because samp$s from them have a relatively 

high thorium content, or because thorium-bearing 

Alaska--Continued 

Thorium 

(percent) 

63 

0-? 

34-63 

25-63 

0.4-3.3 

Usually low, 

but as much 

as 13.1 

Chemical composition 

Thorium silicate, a 

variety of thorite. 

Fluocarbonate of calcium 

and the cerium group. 

Oxide of thorium and 

uranium. 

Thorium silicate-------- 

Essentially yttrium 

phosphate. 

Zirconium silicate, 

usually with some ferric 

oxide and often some 

thorium and uranium. 

--- 

minerals occur in more than trace amounts. The 

distribution by type of deposit of these 13 localities 

is as follows: 

Description 

Color: bright orang& or orange yellow. 

Luster: vltreous to glassy when fresh, 

dull to greasy when altered. 

Fracture: conchoidal. 

Hablt: square prismatic crystals, also 

massive. 

Specific gravity: 4.1-6.3. 

Color: brownish yellow, brown, wax :ellow. 

Luster: vitreous to resinous. 

Fracture: subconchoidal to splintery. 

Habit: crystals small and slender, 

pyramidal or prismatic. 

Specific gravity: 4.4. 

Color: black, brownish,or grayish. 

Luster: submetallic to dull or g~asy. 

Fracture: uneven to subconchoidal. 

Habit: cubic. 

SpBcific gravity: 9.3. 

Color: commonly black, brown, less 

commonly green. 

Luster: vitreous to glassy when fresh, 

dull to greasy when altered. 

Fracture: conchoidal. 

Habit: square prismatic crystals, also 

massive. 

Specific gravity: 4.1-6.4. 

Color: shades of brown, yellow, green, 

grayish white, pink. 

Luster: resinous to dull or earthy. 

Fracture: uneven and splinter7 

Habit: long or short prismatic crystals. 

Specific gravity: 4.5-4.6. 

Color: various shades of red, brown, 

and gray when thorium bearing. 

Luster: usually dull or subreslnous 

when thorium bearing. 

Fracture: conchoidal. 

Habit: prismatic, commonly long, less 

commonly stout, also massive. 

Specific gravity: 3.6-4.7. 

 ode .............................. 1 

Lode and placer.. .................. 1 

Graditic rock and placer.. .......... 5 

placer. ............................ 6 

Summary descriptions of these 13 localities are 

given below, 

Salmon Bay area 

In the vicinity of Salmon Bay (2 on pl. 1 and table 2) at 

the northern end of Prince of Wales Island, southeastern 

Alaska, radioactive hematite-carbonate veins cut metamorphosed sedimentary rocks of Silurian age (Houston, 

1952a, p. 13). Most of the veins are less than 5 inches 

wide, but at one locality a vein 0 to 10 feet wide is exposed 

for about 300 feet. A sample from a 2- to 3-inch vein 
contains 0.07 percent equivalent uranium but only 0.003 

percent uranium. The difference is probably due to thorium. In addition to thehematite and carbonates, the 

veins contain small amounts of pyrite, and locally minor 

amounts or traces of purple fluorite, chalcedony, feldspar, and mica. Parisite (afluocarbonate of thecerium 

metals) has been identified in samples from a 6- to 10-fool 

thick vein (Houston, 1952b). The radioactive elements 

in these veins are thought to be substitutingfor iron in the 

hematite or carbonates or may also occur as impurities in the fluorite or prisite. 

Tobin Creek-Biq Creek area 

Flacer concentrates from the Tobin Creek-Big 

Creek area (26 on pl. 1 and in table 2) of the Chandalar 

district on the south flank of the Brooks Range in 

northeastern Alaska contain as much as 15 percent 

monazite (White, 1952), which is associated with 

variable amounts of hematite, pyrite, scheelite, ar senopyrite, galena, chalcopyrite, and gold. The 

maximum equivalent uranium content of any of the 

placer concentrates so far obtainedfrom the Chandalar 

district is 0.05 percent. The source of the monazite 

may be "a highly acidic granitic rock, possibly of 

pegmatitic character" (Mertie, 1925, p. 263). 

Manley Hot Springs district 

Eureka area. --In the Eureka area (28 on pl. 1 

and in table 2) of the Manley Hot Springs district in 

central Alaska, Moxham (195213) found monazite and 

radioactive zircon in granite at Elephant Mountain. 

This granite averases about 0.004 percent equivalent 

uranium. Concentrates from placers in the Eureka 

area contain frorn 0.004 to 0.042 percent equivalent 

uranium and average about 0.02 percent equivalent 

uranium. The radioactivity is attributed mostly to 

thorium because monazite constitutes as much as 10 

percent of the concentrates and is the chief radioactive 

mineral. The monazite in the Eureka placers was probably derived from the granite at Elephant Mountain. 

Toft tin belt --Concentrates frorn placers of 

the To*ri9 on pl. 1 and in table 2), southwest of the Eureka area in the Manley Hot Springs 

district, contain rnonazite, xenotime, columbite, 

ellsworthite, eschynite, and radioactive zircon 

(Moxham, 195213). A concentrate from Idaho Gulch was found to contain as much as 2.3 percent equivalent uranium although generally the radioactivity of 

the concentrates from the Tofty tin belt is in the O.OX 

range of percent equivalent uranium. Moxham (1952b) 

indicates that the eschynite contains less than 1 percent thorium and no uranium; the columbite has an equivalent uranium content of about 0. I percent; the 

equivalent uranium content of the monazite does not 

exceed 1 percent; and the zircon averages about 0.07 

percent equivalent uranium. 

The bedrock source of the radioactive minerals 

in these concentrates has not been discovered but may 

be a differentiate phase of the intrusive at Rough Top 

Mountain to the north or the granite at Hot Springs 

Dome to the south or both (Mertie and Waters, 1934, 

pp. 244-246). 

Hot Springs Dome area. --In the Hot Springs 

Dome area (30 on pl. 1 and in table 2) monazite and 

xenotime are found in most of the placers of creeks 

draining the granite area of Hot Springs Dome 

(Moxham, 1062b). The equivalent uranium content. 

of this granite averages 0.003 percent. 

Although the radioactivity of the heavy-mineral 

fractions (those,greater than 3.3 specific gravity) of 

the placer concentrates from the Hot Springs Dome area is in the 0. OX range of percent equivalent 

uranium, one concentrate from a tributary of Hot 

Springs Slough on the south side of the Dome contains 

0.3 percent equivalent uranium, about 20 percent 

monazite, and 5 percent xenotime. Another concentrate from glacial material just east of Blowback 

Creek on the north side of Hot Springs Dome contains 

0.155 percentequivalent uranium ,-nd about 20 percent 

monazite. 

Long area 

In the Long area (31 on pl. 1 and in table 2) 

of the Ruby-Foorman district in central Alaska, 

allanite and thorite are the chief radioactive minerals 

found in granite and in placers derived from the 

granite (White and Stevens, 1952b). The equivalent 

uranium content of the granite averages 0: 005 percent; 

heavy-mineral fractions (those greater than 2.8 

specific gravity) of the placer concentrates contain 

as much as 1.6 percent equivalent uranium and 

average 0.3 percent equivalent uranium. The thorite 

content of the heavy-mineral fractions from both the 

granite and placer concentrates ranges from a trace 

to about 10 percent. 

Qualitative spectrographic analysis of the thorite 

indicates uranium(?), thorium, and siliconas major 

constituents; and calcium, iron, titanium, and yttrium as 

minor constituents. Chemical analysis of the thorite shows 

the uranium content to be about 8 percent. No analytical 

data are available on the allanite except that it gives a positive flux test for uranium. 

Fork area 

Uranium-bear ing thorianite, allanite, and 

other radioactive minerals have been reported 

from the Nixon Fork area (33 on pl. 1 and in 

table 2) in central Alaska (White and Stevens, 

1952a). The thorianite occurs in placers, where 

it is associated with uraniferous hematite, 

malachite, sphene, and zircon. The concentrate 

exhibiting the greatest radioactivity contains 0.078 

percent equivalent uranium, most of which is 

attributed to the uraniferous thorianite. The 

bedrock source of the radioactive minerals has 

not been located. 

Large fragments of an altered limestone on the 

dump of the Whalen mine contain a high percentage 

of radioactive allanite. The altered limestone is 

apparently closely associated with contact-metamorphic gold-copper ores along a contact between limestone and rnonzonite. The altered limestone contains as much as 0.05 percent equivalent 

uranium, which is ascribed to thorium, because 

chemical analyses show a content of only 0.004 percent uranium. About a quarter of the altered limestone consists of minerals of greater than 2.8 

specific gravity. Of this heavy fraction 98 percent 

is allanite; zircon, kyanite, and scheelite constitute 

the remaining 2 percent. 
Near the shaft of the Whalen mine a highly 

altered phase of the limestone is exposed; it contains 

about 0.025 percent equivalent uranium and 0.002 percent uranium. The radioactive mineral here is parisite, 

which in the samples taken, makes up about 95 percent 

of the heavy-mineral fraction (that greater than 2.8 

specific gravity) of the rock. 

Buckland-Kiwalik district 

Clem Mountaln area. --Uranothorianite and 

traces of thorite have been identified in several placer 

concentrates from the Clem Mountain area (36 on pl. 1 

and in table 2) in the northern part of the BucklandKiwalik district (West ahd Matzko, 1952) of the eastern Seward Feninsula. 

Heavy-mineral fractions (those greater than 2.8 

specific gravity) containing more than 0.025 percent 

equivalent uranium were obtained from concentrates 

of placers in Duck, East Clem, and West Clem Creeks. 

The heavy-mineral fraction with the greatest radioactivity (0. 106 percent equivalent uranium) was 

obtained on Duck Creek above the mouth of West Clem 

Creek. 

Although the source of the radioactive minerals 

is not known, it is likely that they are disseminated 

accessory minerals in the granitic intrusives that 

form the backbone of the Buckland-Kiwalik divide, 

because the radioactive minerals are found only in the 

creek gravels containing granitic pebbles, 

Hunter Creek-ConnoUy Creek-Fairhaven 

Creek area. --Flacer concentrates from creek gravels 

within the headwater drainage of Hunter, Connol.ly, 

and Fairhaven Creeks (37 on pl. 1 and in table 2), 

south of the Clem Mountain area, contain thorite, 

uranothorianite, gummite, and traces of orangite 

(West and Matzko, 1952). Concentrates with heavymineral fractions containing more than 0.025 percent 

equivalent uranium were obtained from numerous sites 

in the Hunter Creek-Connolly Creek-Fairhaven Creek 

area. The sample with the greatest radioactivity was taken on Muck Creek, a left-limit tributary of Hunter 

Creek, and contslins 0. 16 percent equivalent uranium. 

The bedrock source of the radioactive minerals 

is not certain but, as in the Clem Mountain area, is 

presumed to be the granitic rocks in-the drainage 

basins of the streams with radioactive placers. The 

thorite and orangite apparently are restricted to the 

gravels in the headwaters of Fairhaven Creek, and 

the liranothorianite and gummite seem to be limited to 

placers in the headwaters of Hunter and Connolly Creeks 

Granite Mountain area. --Granite Mountain 

(38 on vl. 1 and in table 2) in the eastern Seward 

~eninsula is composed largely of a syenitic stock 

which was intruded into a complex of andesitic flows 

and intrusives (Gault and others, 1946; Killeen and 

White, 1950; West and Matzko, 1952). The average 

radioactivity of the syenite is about four times that of 

the andesitic rocks. The chief radioactive minerals 

in placer and bedrock samples from the Granite 

Mountain area are allanite, uranothorianite, t hor ite, 

and gummite. The equivalent uranium content of the 

heavy-mineral fractions (those greater than 2.8 

specific gravity) of the placer concentrates is generally 

O.OX percent. Concentrates with more than 0.025 

percent equivalent uranium have been obtained from 

the placers of headwater tributaries of the Feace 

River, Anzac Creek, Rube Creek, Sweepstakes Creek: , headwater tributaries of the Kiwalik River, South 

Fork Quartz Creek, Cub Creek: and an unnamed 

tributary of West Fork Buckland River. In all the 

radioactive concentrates the uranothorianite appears 

to be the main radioactive mineral. Although allanite 

is relatively abundant in a pegmatitic facies of the 

granitic rock near the top of Granite Mountain, and 

traces of uranothorianite have been identified among 

the accessory minerals of a specimen of syenite from 

the north flank of Granite Mountain in the headwaters 

d Quartz Creek, no lode concentrations of the mdioactive minerals have yet been found. However, several 

placer concentrates from the extreme headwaters of 

the Feace River on the east flank of Granite Mountain near the contacts between the andesite and syenite 

have an equivalent uranium content of about 0.2 to 

about 0.8 percent or approximately 10 times that of 

the average uranothorianite-bearing concentrates 

found elsewhere in the eastern Seward Feninsula. 

These more radioactive concentrates, particularly 

uranothorianite, contain a higher content of the radioactive minerals than the other radioactive concentrates; 

in addition they contain copper sulfide minerals, 

silver, and bismuth, which have not been identified in 

the average uranothorianite-bearing samples. The 

greater amount of uranothorianite and the occurrence 

of minerals believed to be of hydrothermal origin in 

placers less than a mile from stream divides suggest 

the presence of a lode containing radioactive minerals. 

Darby Mountains district 

Tubutulik River area. --The chief radioactive 

minerals found in the placers of the Tubutulik River area (40 on pl. 1 arld in table 2), in the northeastern 

part of the Darby Mountains district in the eastern 

Seward Feninsula, are allanite and unidentified niobate 

minerals (West, 1952). The heavy -mineral fractions 

(those greater than 2.8 specific gravity) of the oon- centrates contain as much as 0. 1 Percent equivalent 

uranium but average only about 0.02 percent equivalent 

uranium. In three samples from the area the niobates are estimated to constitute from 5 to 10 percent of the 

heavy-mineral fractions of the concentrates. Qualitative spectrographic analyses show that in two 

samples the niobates contain uranium as a major 

element with no thorium recognized; in the third 

sample the niobate contains both uranium and thorium as major constituents. A spectrographic analysis of 

the allanite in one sample shows thorium as a major 

constituent with no uranium found. The bedrock . source of the allanite is unknown but is assumed to 

be differentiate phases of granitic rock in the drainage 

areas of the streams from which the samples were 

obtained. The presence of topaz and traces of cassiterite along with the niobates suggests that these 

minerals may be genetically related to lode tin occurrences. It is also possible that these minerals may 

have originated in pegmatitas. 

Golovin Bay area. --The most radioactive 

minerals in various tvnes of alacers alona the east 

shore of Golovin Bay "(42 on 61. 1 and in &le 2), in 

the western part of the Darby Mountains district, are allanite, monazite, and an unidentified niobat~ mineral 

(West, 1952). The equivalent uranium content, of the 

heavy-mineral fractions (those greater than 2.8 
specific gravity) of concentrates from these placers 

ranges from 0.001 to about 0.08 percent. 

The niobate mineral has been recognized only 

in a concentrate from slope wash on the beach about 

midway between Cheenik and Mission Creeks. The 

sample location is near the contact of a younger 

granite with an older intrusive complex. The heavymineral fraction of this concentrate has an equivalent 

uranium content of about 0.08 percent and is the most 

radioactive heavy-mineral fraction taken in the area. It is estimated that the unidentified niobate mineral 

comprises about 5 to 10 percent of the heavy-mineral 

fraction, which also contains minor amounts of 

sphene, topaz, hematite, allanite, and scheelite. 

Qualitative spectrographic analysis of the niobate 

shows uranium and thorium as major constituents. 

Farther south along the Golovin Bay coast 

monazite and traces of allanite are found in a slopewash concentrate of which the heavy-mineral fraction 

contains about 0.05 percent equivalent uranium. This 

sample was taken near the contact of granite with an 

older intrusive complex. 

The remaining radioactive concentrates from 

the Golovin Bay area have equivalent uranium contents 

that range from about 0.01 to about 0.03 percent. 

This radioactivity is ascribed largely to traces of 

uranium or thorium in minor amounts of allanite, 

sphene, and zircon. 

Cape Mountain area 

The major radioactive minerals in placer con- oentrates from the Cape Mountain area (47 on pl. 1 

and in table 2), in the western Seward Feninsula, are monazite, xenotime, and zircon. The concentrates 

contain as much as 0.9 percent equivalent uranium 

and average about 0.03 percent equivalent uranium 

which, because of the monazite content of the concentrates, is ascribed mostly to thorium. The source 

of the radioactive minerals is probably the granite 

at Cape Mountain, although they may be ,genetically 

related to the tin deposits in the area. 

CONCLUSICNS 

At 47 localities Alaska thorium occurs as a 

major constituent or in minor amounts as an impurity 

in one or several of 12 minerals, These minerals 

are allanite, columbite, ellsworthite, eschynite, 

gummite,' monazite, orangite, parisite, thorianite, 

thorite, xenotime, and zircon. At some localities 

sphene and biotite are also radioactive and may contain thorium; unidentified niobate minerals with 

uranium or uranium and thorium as major constituents 

have also been recognized. Lode thorium occurrences 

warranting possible further consideration are in 

radioactive hematite-carbonate veins in the Salmon 

Bay area on Frince of Wales Island, southeastern 

Alaska; and in a contact zone between limestone and 

rnonzonite in the Nixon Fork area in central Alaska. 

Data on these two deposits, however, are not 

sufficient to determine their potentialities. 

The remaining thorium occurrences of any significance are in placers or as accessory minerals in 

granitic rocks. It is possible that thorium might be 

obtained as a byproduct from gold or tin placer 

operations in the following localities: 

Major thoriumbearing minerals 

Tobin Creek-Big Creek Monazite 

area, Chandalar district, 

northeastern Alaska. 

Manley Hot Springs district, Columbite 

central Alaska. Ellsworthite 

Eschynite 

Monazite 

Xenotirne 

Long area, central Alaska---- Thorite 

Nixon Fork area, central Uranothorianite 

Alaska. 

Buckland-Kiwalik district, Uranothorianite 

west-central Alaska Thorite 

(Seward Feninsula). 

Cape Mountain area, west- Monazite 

central Alaska (Seward Xenotime 

Fenins ula). 

More data are needed, however, to determine the 

thorium potentialities of these placer localities. 

LITERATURE CITED 

Ford, W. E. , 1932, Dana's textbook of mineralogy, 

4th ed, , New York, John Wiley and Sons, Inc. 

Frondel, J. W., and Fleischer, M., 1950, A 

glossary of uranium- and thorium-bearing minerals: 

U. S. Geol. Survey Circ. 74. 

Gault, H. R. , 1949, Trace elements reconnaissance 

in the Candle Creek area, Fairhaven district, Seward 

Feninsula, Alaska: U. S. Geol. Survey Trace 

Elements Inv. Rept. 41. [Unpublished. ] 

Gault, H. R., Black, R. F., and Lyons, J. B., 1946, 

Preliminary report on trace elements investigations 

in the Sweepstakes Creek area, Koyuk district, 

Seward Feninsula, Alaska: U. S. Geol. Gurvey Trace 

Elements Inv. Rept. 25. [Unpublished. ] 

George, D'Arcy, 1949, Mineralogy of uranium- and 

thorium-bearing minerals: b. S. Atomic Energy 

Comm. RMO-563. 

Harder, J. O., andReed, J. C., 1945, Freliminary 

report on radioactivity of some Alaskan placer 

samples: U. S. Geol. Survey Trace Elements Inv. 

Rept. 6. [Unpublished. ] 

Houston, J. R. , 1952a, Ft. 4, Southeastern Alaska, 

- in Freliminary summary of reconnaissance for 

uranium in Alaska, 1951: U. S. Geol. Survey Circ. 

196, pp. 13-17. 

1952b, Interim report: radioactive 

hematite-carbonate veins in the Salmon Bay area, 

Frince of Wales Island, southeastern Alaska: U. S. 

Geol. Survey Trace Elements Memo. Rept. 

356. [Unpublished. ] 

Killeen, F. L., and Ordway, R. J., 1946, Trace 

elements investigations at Ear Mountain, Seward 

Feninsula, Alaska: U. S. Geol. Survey Trace 

Elements Inv. Rept. 27. [Unpublished. ] 
Killeen, F. L,, and White, M. G., 1950, Trace 

elements reconnaissance on the South Fork of 

Quartz Creek, northeastern Seward Feninsula, 

Alaska: U. S. Geol. Survey Trace Elements Inv. 

Rept. 42, pt. 2. [Unpublished. ] 

Mertie, J. B., Jr., 1925, Geology and gold placers 

of the Chandalar district, Alaska: U. S. Geol. 

Survey Bull, 773-E, pp. 215-263. 

Mertie, J. B., Jr., and Waters, A. E., Jr., 1934, 

Mineral deposits of the Rampart and IIot Springs 

districts, Alaska, by J. B. Mertie, Jr. ; Flacer 

concentrates of the Rampart and Hot Springs districts, 

by A. E. Waters, Jr. : U. S. Geol. Survey Bull. 

844-D, pp. 163-246. 

Moxham, R. M., 1952a, Pt. 3, Radioactive minerals 

in the Yakataga beach placers, in Reconnaissance 

for radioactive deposits in south-central Alaska, 

1947-49, U. S. Geol. Survey Circ. 184. pp. 11-14. 

195213, Reconr~aissance for radioactive deposits in the Manley Hot Springs-Rampart 

district, central Alaska: U. S. Geol. Survey Trace 

Elements Inv. Rept. 54. [Unpublished. ] 

Moxham, R. M., and Nelson, A. E., 1952, Pt. 2, 

Radioactive pegmatite minerals in the Willow Creek 

mining district, j~ Reconnaissance for radioactive 

deposits in south-central Alaska, 1947-49, U, S. 

Geol. Survey Circ. 184, pp. 7-10. 

Moxham,R. M., and West, W. S., 1949, Trace elements 

investigations in the Ser pentine-Kougarok area, 

Seward Feninsula, Alaska: U. S. Geol. Survey Trace 

Elements Inv. Rept. 39. [unpublished. ] 

Falache, C., Berman, H.; and Frondel, C., 1951, 

Dana's system of mineralogy, 7th ed., vol. 2, 

New York, John Wiley and,Sons, Inc. 

Robinson, G. D., Wedow, Helmuth, Jr., and 

Lyons, J. B. , 1946, Trace elements investigations 

in the Cache Creek-upper Feters Creekarea, Yentna 

district, Alaska: U. 8. Geol. Survey Trace 

Elements Inv. Rept. 26. [unpublished. ] 

Skidmore, J. B , 1944, Freliminary reconnaissance 

survey of Alaska placer deposits: Union Mines and 

Devel. Corp. [Unpublished. ] 

Wedow, Helmuth, Jr. , 1952, Reconnaissance for 

radioactive deposits in the Eagle-Nation area, Eagle 

and Charley River quadrangles, east-central Alaska: 

U. S. Geol. Survey Trace Elements Inv. Rept. 56. 

[In preparation. ] 

Wedow, Helmuth, Jr., and Matzko, J. J., 1947, 

Trace elements reconnaissance along highways in 

the Tanana and upper Copper River valleys, Alaska: 

U. S. Geol, Survey Trace Elements Inv. Rept. 38. 

[~npublished. ] 

Wedow, Helmuth, Jr., and Tolbsrt, G. E., 1952a, 

Radioactivity at the Copper Creek copper lode prospect, Eagle huadrangle, east-central Alaska: 

U. S. Geol. Survey Trace Elements Inv. Rept. 195. 

[ Unpublished. ] 

1952b, Reconnaissance for radioactive deposits in the Fortymile district, Eagle 

quadrangle, east-central Alaska: U. S. Geol. 

Survey Trace Elements Inv. Rept. 196. 

[In ] 

Wedow, Helmuth, Jr., White, M. G., and 

Maxham, R. M., 1951, Interim report on an 

U. S, Geol. Survey Trace Elements Memo. Rept. 

235. [open file. ] 

West, W. S., 1952, Reconnaissance for radioactive 

deposits in the Darby Mountains area, Solomon and 

Bendeleben quadrangles, Seward Feninsula, Alaska: 

U. S. Geol. Survey Trace Elements Inv. Rept. 53. 

[In preparation. ] 

West, W. S., and Berlson, F. D., 1952, Reconnaissance for radioactive deposits in the vicinity of 

Ketchikan, Goddard Hot Springs, Chichagof, Funter 

Bay, and Juneau, southeastern Alaska: U. S. Geol. 

Survey Trace Elements Inv. Rept. 189. 

[In preparation. ] 

West, W. S., and Matzko, J. J., 1950, Radiometric 

and mineralogic studies of the granitic complex in 

the Cape Nome area, Seward Feninsula, Alaska: 

U. S. Geol. Survey Trace Elements Inv. Rept. 45, 

pt. 2. [Unpublished, ] 

1952, Reconnaissance for radioactive 

deposits in the Buckland-Kiwalik district, Candle 

quadrangle, Seward Feninsula, Alaska: U. S. Geol. 

Survey Trace Elements Jnv. Rept. 49. 

[Unpublished. ] 

White, M. G., 1950, Radioactivity and mineralogy 

of placer concentrates from the Fortymile district, 

Alaska: U. S. Geol. Survey Trace Elements Inv. 

Rept. 57-A. [unpublished. ] 

1951, Radioactivity in the l'Okpilak'l 

gneissic grate, Mount Michelson area, northeastern'Alaska: U. S. Geol. Survey Trace Elements 

Inv, Rept. 57-C. f Unpublished. 1 

1952, ~adioactivi't~ and mineralogy 

of placer concentrates from the Wiseman and 

Chandalar districts, Upper Yukon region, Alaska: 

U. S. Geol. Survey Trace Elements Memo. 

Rept. 327. [Unpublished. ] 

White, M. G. , and Killeen, F. L., 1950, Radioactivity and mineralogy of concentrates from the 

placers of Julian, Moore, and Candle Creeks, and 

the Cripple Creek Mountains, lower Yukon-Kuskokwim 

Highlands region, Alaska: U. S. Geol. Survey 

Trace Elements Inv. Rewt. 45. pt. 1. 1 Unpublished. 1 

1952, ~eEonnaissance f& radioactive deposits in the vicinity of Flat, Iditarod 

quadsangie, southwestern~laska: U. S. Geol. Survey 

Trace Elements Inv. Rept. 46. [unpublished. ] 

White, M. G., and Stevens, J. M. ,- 1952a,Reconnaissance for radioactive deposits in the vicinity of the 

Nixon Fork mines, Medfra quadrangle, central 

Alaska: U. S. Geol. Survey Trace Elements Inv. 

Rept. 75. [~n preparation. ] 

1952b, Reconnaissance for radioactive deposits in the Ruby-Foorman district, 

Ruby quadrangle, central Alaska: U. S. Geol. Survey 

Trace Elements Inv. Rept. 192. [~n preparation. ] 

White, M. G., and Tolbert, G. E., 1952, Radioactive 

granite in the Miller House-Circle Hot Springs area, 

east-central Alaska: U. S. Geol. Survey Trace 

Elements Inv. Rept. 194. [Unpublished. 1 

White, M. G., and West, W. S,, 1952, Freliminary 

summary of reconnaissance for uranium on the 

Seward Feninsula, Alaska, during 1951: U. S. Geol. 

Survey Trace Elements Memo. Rept. 322. 

[Unpublished. ] 

apprais$l of the uranium possibilities of Alaska: 
! 

g 

$ 

a; 

0 6 

cumm 

2gb': 

.oa " .- El 4 !-.A drl cl F4 

wcco 

g5 

8% 

V 

a3u&z*m330 

Jemo 

U03JTZ 

eruTvuax 

e3r~om 

e~~uw~dom 

e7TsTJWd 

e%yBu*~o 

a?r zeuo~ 

@?Tnmm9 

a?~dwsa 

03TWJofiQTT8 

@3T9FTO3 

e'4TUQTTV 

+-'. 

d 

r;i 8 - m * m CU rl 3 rr\ rl 

i 6. i 9 

$& C m B 0 NO cd 0 lnm CU 2 rnd Ln 

.- 9 I c 

dS 1 s, sd 0 P) *d 4:b; 

9 9 

P" 8' E r] 

a84 . ame% 

I 

I I 

u l I : to w 0 k 

I m 

cd 1 4 I 2 $ 4gi] * 9 a m " $?a C .QO 8' .g $4 4 0 N sfi CU .nCUv4c 

3 g qa s 

ri =t pt PI L- EL, D, GI GI 0 I4 

I rn I Ln x 'Sc I I 

X I I 

I I I X I I I " I I 

I I I I I I I I I I 

I I I I H I I I I I I 

I 1 I I I I I 

4 N I I I I I 

X I I 

I I I I X I I 

I I 

I I x I I K x 

I I I I I I I I I I 

I I I I I I I I I I 

I I I I I I I I I 

I I I I I I I I I I 

X I X I X I I 

I I - m 1 e. rl I 

PI a Y 

. d 

Zs r0 

V1 V1 
Concentrate contains 0.044 percent thorium. 

HMF; as much as 

0.064. 

Concentrate contains 0.03 percent thorium. 

Concentrate contains 0.044 percent thorium. 

Do. 

Robinson and othe-s, 1946, 

pp. 22, 23, table 5. 

Harder. and Reed, 1945, 

PP- 59 17- 

Harder and Reed, 1945, 

PP. 5, 6, appendix. 

G; 0.004 ----------- i Wedow and Matzko, 1947, 

PP. 31, 58. 

G; 0.004----------- 1 Wedow and Matzko, 1947, 

PP. 31, 60. 

G; 0.004; m-P; 

as much as 0.02. 

HMF; as much as 

0.011, avg. 0.006. 

W; as much as 

0.041. 

Wedow and Matzko, 1947, 

pp. 36, 63. 

G; as much as 0.06, 

avg. 0.004; HMF-P; 

as much as 0.1 

(approx.). 

G; as much as 0.005; 

HMF-P; as much as 

o -096. 

m- 0.013---------. 

Wedow and Matzko, 1947, 

PP- 27, 55-57. 

e 

White, 1950; Wedou and 

Tolbert, 1952b. 

Wedow and Tolbert, 1952b. 

Wedow and Tolbert, 1952a. 

See footnotes at end of table. 
Table 2. --Occwrences of thorlum-bearlng mlnerals in Alasxa--Continued 

Nm: .Explanation of symbols used in rable. 

G: granitic rock. 

L: lode deposit. 

P: placer. 

HMF: heavy-mineral fraction {usually grracer rhan 2.8 specific gmv4ty). 
. ., Lr' Lr' 

?mi 

m? odq cd 0 

5 bb z 6," 3 52"" 6 * * 2 a * 

2 '"" g: ..I 2 

GI 
Table 2.--Occurrences of thorium-bearing minerals in Alaska--Continued 

Nm: Expdauatim d symbol. used in table. 

G: granitic roek. 

L: lcde deporit. 

. P: pIacer. 

HMF: iun~-mimral kactio. (udully greater than 2.8 spcific paw). 

Quadrangle rtkmces arc the new 1:250,000 Ahsku Recoanaissance Series, most of &cb arc available at lnst in pf copy. 
IAllanite occurs in sample from contact copper-iron ore; location in doubt. 

2~arfsite not known td be radioactive, study now in progress. 

3~horiw.n may be replacing Iron in hematite or carbonates. 

4~adioactive hemstite -carbonate veins. 

ho other minerals belonging to zircon group. 

60ther minerals are cgrtolite . Peptites. 6 jor radioactive mineral is biotite;. radioactivity mostly due to uranium. 

g~adioac tive mineral belonging to spinel group. 

10~ontact-metamorphic zone be tween limes tone and monzonite . 11~eavy-mineral fractions containing more than 0.2 percent equivalent uranium restricted to headwaters of Peace River; 'other 

possible thorium-bearing mineral in Granite Mountain area is radioactive sphene. 

12spectrographic analysis shows thorf um and no uranium. 

I3~h-e unidentiried. columbata mine~als; two with uranium and no thorium, one with both thorium and uranium as major constituents . 14~nidentified columbate mineral containing uranium and thorium as major constituents. 

Harder and Reed, 1945, 

p. 9. Also file data. 

-- 47. Cape Mountain area--- -- GP HMF; as much as much as 0.9, 

avg. 0.03. 

-- -- -- -- x - - - - - - - - X X