Tofty Tin Belt 

Manley Hot Springs 

District, Alaska 

By RUSSELL G. WAYLAND 

MINERAL RESOURCES OF ALASKA 

GEOLOGICAL SURVEY BULLETIN 1058-I 

Occurrence and exploitation of 

r;assiterite-bearing gold placer 

deposits 

TNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961 
UNITED STATES DEPARTMENT OF THE:INTERIOR 

FRED A. SEATON, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

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

Washington 25, D.C. 
CONTENTS 

Pa£e 

Abstract---------------------------------------------------------- 363 

Introduction------------------------------------------------------ 364 

GeologY---------------------------------------------------------- 365 

Bedrock------------------------------------------------------ 366 

Alluvium----------------------------------------------------- 368 Economic geology _____________________________ - _____ - ___ - _- __ -- _-- 369 

Lodedeposits------------------------------------------------- 369 Placer deposits__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 370 

Individual placers ___________________________________ ------____ 374 

Cache Creek---------------------------------------------- 374 Dalton Gulch_____________________________________________ 376 

Harter Gulch ____ ----- _______________________ -------______ 376 

Sullivan Creek-------------------------------------------- 377 

Tofty Gulch---------------------------------------------- 379 

Idaho Gulch---------------------------------------------- 382 Miller Gulch______________________________________________ 384 

Deep Creek----------------------------------------------- 385 VVoodchopper Creek_______________________________________ 392 

VVest of VVoodchopper Creek _______________________ --------- 394 

Gold Basin and Killarney Creeks ______________ ------________ 394 

Cassiterite outside the Tofty tin belt_____________________________ 396 

Origin of the cassiterite----------------------------------------- 398 

Recovery of the cassiterite__________________________________________ 403 

Sampling of tailings __________________________ -- _________________ M -- 407 

Cassiterite reserves __________________________________________ ----__ 411 

Selected references __________________ ---- __________ -- ______ -----____ 412 

Index------------------------------------------------------------ 413 

ILLUSTRATIONS 

PLATE 40. Geologic map of the Tofty area, Manley Hot Springs district, Alaska ______________________________________ In pocket 

41. Tofty tin-belt placers and sections along selected drill 

holes-------------------------------------------- lnpocket 

42. Aerial photograph of Tofty tin-belt workings in 194L __ Facing 406 

43. A, Sluicing on Deep Creek, 1941; B, Reworking a Deep Creek tailings pile, 194L _________________________ Facing 407 

FIGURE 48. Index map showing location of mapped area________________ 364 

m 
IV CONTENTS 

TABLES 

TABLE 1. Rock types, physical shapes, and relative abundance of grav- Page 

els and boulders in individual placer tailings______________ 371 

2. Summary of drilling by Adolph Bock, 1926 through 194L___ 389 

3. Cassiterite and gold in tailings from Tofty tin belt__________ 408 

4. Vertical samples through Cache Creek tailings_ _ _ _ _ _ _ _ _ _ _ _ _ 409 
MINERAL RESOURCES OF ALASKA 

TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT, 

ALASKA 

By RussELL G. WAYLAND 

ABSTRACT 

Buried placer deposits in a belt about 8 miles long by 1 mile wide at Tofty, 

near Manley Hot Springs, Alaska, have yielded a few hundred tons of cassiterite 

as a byproduct to the recovery of several million dollars in placer gold. 

The placer deposits are at the base of unconsolidated gravels of early Quaternary age lying on an erosion surface of moderate relief cut on phyllite of Cretaceous age. The gravels are buried beneath 10 to 170 feet of frozen muck and 

silt of Quaternary age. The closest known outcrops of igneous rocks are a few 

small serpentinized mafic dikes about a mile north of the belt of placer deposits, 

some monzonite masses about 4 miles north of the easternmost placer, and a 

biotite granite body about 6 miles southeast of the tin belt. Known lode mineralization exposed near the tin belt consists chiefly of small, discontinuous 

quartz veins containing a few accessory minerals. 

The Quaternary gravels consist largely of graywacke, phyllite, sandstone, 

light and dark quartzite, and quartz pebbles derived locally from the Cretaceous bedrock. The basal gravels which contain placer gold and cassiterite are 

well rounded and have more pebbles of quartz and light quartzite; they also 

contain a few cobbles and pebbles of granite and quartz-tourmaline rock. Many 

pebbles containing brown tourmaline also contain cassiterite; conversely, nearly 

all cassiterite pebbles also contain brown tourmaline, as well as quartz and 

altered fragments of country rock. A suite of pebbles grading from predominantly cassiterite to mostly brown tourmaline is brecciated throughout. Chromite is common in gravel from the Deep Creek part of the tin belt. 

Many individual placer concentrations are related to details of the drainage. 

system cut on the bedrock surface, particularly to minor gullies and terrace 

slopes. Nearly all cassiterite particles and most gold particles are well rounded 

and polished. 

Although a major Tertiary stream may have brought cassiterite-bearing 

gravels and some gold into the tin belt from the Hot Springs Dome area or 

from some unexposed granite body nearer the tin belt, the writer considers it 

much more likely that the placer gravels were derived from unexposed quartz 

veins immediately north of the tin belt which were brecciated and mineralized 

with tourmaline and cassiterite during Tertiary intrusive activity. Subsequent 

prolonged erosion of perhaps several thousands feet of the mineralized bedrock 

by streams of moderately low gradient resulted in residual deposits with local 

363 
364 MINERAL RESOURCES OF ALASKA 

concentration. The mantle of Quaternary silt now conceals the roots of these 

lodes. 

The total indicated and inferred reserves of cassiterite remaining in the 

buried placers of the district are estimated to be about 2,000 tons. Recoverable reserves would be a fraction of this figure, depending on mining and recovery methods and economic conditions. However, cassiterite would probably 

remain a byproduct to gold recovery. 

Sampling of tailings piles by the Geological Survey indicates an additional 

reserve of about 222 tons of cassiterite, and about $118,000 in gold. 

INTRODUCTION 

Placer deposits (pl. 42 and fig. 48) at Tofty, near Manley Hot 

Springs, Alaska, yielded about 315 tons of cassiterite concentrates 

through 1941 as a byproduct to the recovery of gold worth several 

IQO 200 MILES 

FIGURE 48.-Index map showing location of mapped area. 

million dollars. Although gold was discovered in 1907, the first tin 

shipment was not made until1911. The most active gold mining and 

the largest output of tin took place before 1919, by which time 262 tons 

of cassiterite had been produced. From 1919 through 1941 the most 

notable mining development in the area was the use of strip-mining 

methods in two of the shallower pay streaks. 

Cassiterite has been produced from many buried placer deposits 

in a belt about 8 miles long and 1 mile wide. Cache, Sullivan, and 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISXRICT 365 

Woodchopper Creeks, and their branches, all tributaries of Patterson 

Creek, cross the tin belt (pl. 40) . A road 20 miles long links the tin 

belt with the town of Manley Hot Springs on a slough of the Tanana 

River. In 1941 there were 2 landing fields for small aircraft served 

frequently from Fairbanks, 95 miles east. The 1941 summer population of the tin-belt area was about 40 persons. 

The need for a critical evaluation of the cassiterite reserves of the 

United States caused the Geological Survey to undertake a field examination of the Tofty tin area during the summer of 1941. The 

geology and mining operations had previously been described by 

Eakin ( 1913), Mertie ( 1934) and Waters ( 1934), but it was hoped 

that a more detailed study emphasizing cassiterite reserves might 

provide some quantitative data and indicate the feasibility of further 

exploration and development. Topographic maps (pls. 40 and 41) 

were made by J. E. Mundine in the early stages of the work, after 

which all tailings pile in the belt were systematically sampled. Old 

workings were sketched (pl. 41), and some information on their 

histories, production, depths, and other features was acquired from 

the older prospectors and mining operators living in the region. 

Drill records were collected and studied. The writer was ably assisted in the sampling by Morton C. Smith and by Joseph Wilson, 

James Lisca, James Noble, and Robert J. Rogers. For other information the writer is indebted especially to Messrs. R. E. Wyer, H. H. 

Thurston, and S. L. Cotton of the Cleary Hill Mines Co. and to 

Messrs. Adolph Bock, Otto Hovley, and Fred Hanson of Tofty. The 

kindness of Messrs. Gus Benson, Jack Donahue, Tom Dean (Dimnic), 

J. W. Farrell, William Albrecht, James Cessford, and Patrick 

McLaughlin was also appreciated. 

The results of the work were made available to war agencies in 

early 1942. The mining problem and most of the estimates of tin 

reserves discussed in this report are still valid (in 1958), because 

only 2 of the 6 streams discussed have been mined since the fieldwork was done. 

GEOLOGY 

The placer deposits are at the base of unconsolidated gravels of 

early Quaternary age lying on phyllite of Cretaceous age, and are 

buried beneath 10 to 170 feet of frozen muck and silt of Quaternary 

age. Except for a few small serpentinized and chloritized mafic 

rocks found locally in a belt just north of the placer deposits, the 

only igneous rocks cropping out in the region are the Tertiary intrusive rocks of Roughtop Mountain northeast of the area and of 

Hot Springs Dome to the southeast. The principal relations of these 

units are shown on plate 40, and are discussed briefly below. Further 
366 MLNERAL RESOURCES OF ALASKA 

information on distribution, lithology, structure, thickness, age, and 

correlation was given by Mertie ( 1937, p. 156-172, 186-198, 219-226). 

BEDROCK 

The rocks of Cretaceous age that make up the bedrock of most of 

the area are generally covered with sphagnum moss and other vegetation and by a heavy creeping mantle of distintegrated rock where 

they are not buried beneath Quaternary silts. It is possible, however, to study them in mine openings and in a few outcrops along 

oversteepened banks of streams in the more hilly areas. The predominant rocks are soft, dark-gray phyllite and slates interbedded 

with discontinuous lenses of graywacke. Some phyllite beds are 

light greenish gray or light yellowish gray. Less common than the 

phyllite but more conspicuous among the outcropping rocks are beds 

of dark, dense quartzite. At the top of the ridge north of the placer 

belt is a thick massive bed of light-buff or yellow cemented sandstone 

and quartzite which for part of its length is shown as a separate unit 

on plate 40. A similar quartzite, interbedded with light-colored 

phyllite, crops out in the bluffs at the junction of Blowback and 

Baker Creeks. A lens 100 feet thick of light-yellow crystalline lime_: 

stone containing magnetite and apatite crystals has been exposed by 

prospecting at the head of Harter Gulch, and a few pebbles of similar limestone were noted in the gravels of upper Cache Creek. 

The intrusive rock of Roughtop Mountain has an outcrop area of 

about 8 square miles. The rock is dominantly a coarse-grained, 

porphyritic biotite monzonite. Many large crystals of andesine feldspar stand nearly vertical, suggesting that the present erosion surface 

has truncated the monzonite body at a level far below its top. Several mafic and aplitic segregations have been described by Mertie 

(1937, p. 219-226), but these lack both cassiterite and tourmaline, 

and no cassiterite appears in the gravels of present streams draining 

the outcrop area. 

The intrusive body of Hot Springs Dome, which is somewhat 

larger than the Roughtop Mountain body, crops out over an area 

of about 20 square miles. It is elongate and its major axis trends 

about N. 65° E. The rock is a biotite granite rather than a monzonite, and associated with it are several salic segregations containing 

conspicuous dark tourmaline needles. No cassiterite has been found 

in the intrusive body, the adjoining phyllite, or the gravels of the 

streams draining the outcrop area. However, chemical analyses 

given by Mertie (1937, p. 222) and the presence of tourmaline show 

that the granite of Hot Springs Dome is more typical of source rocks 

of cassiterite-bearing veins than the monzonite of Roughtop Mountain. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 367 

The phyllite beds at the south border of Roughtop Mountain are 

compressed and crenulated for 1,000 feet, and within 200 feet of the 

border they are recrystallized locally to spotted schist containing 

brown biotite. At the contact with the intrusive mass the country 

rock is in some places converted to a dense hornfels. At Hot Springs 

Dome similar changes occurred in the phyllite northward as far as 

a mile from the granite. Metamorphism is even more intense of the 

intrusive rock along the bedding planes of the rocks of Bean Ridge, 

where garnet, andalusite, tourmaline, brookite, monazite, and zircon 

were found by Waters (1934, p. 242) in the stream gravels. No 

phyllite beds that are similarly metamorphosed crop out near the 

cassiterite-bearing placers or elsewhere in the Tofty area. 

The only igneous rocks observed near the placer deposits are three 

small dense, serpentinized and chloritized mafic dikes, one of which 

contains a core of metadiorite consisting chiefly of hornblende, albite, 

chlorite, and epidote. These dikes all lie about 1 mile north of the 

placer belt, and are shown on plate 40. A fourth dike crops out 

on the crest of the Boulder Creek drainage divide near the American 

Creek trail. At two of the outcrops the metamorphism adjacent to 

the dikes is very slight, but the outcrop at the head of Harter Gulch 

reveals a poorly exposed zone of serpentinized country rock of undetermined width containing cross-fiber veinlets of serpentine, some 

soft white chlorite, and a small amount of calcite and magnetite; 

a bed of crystalline limestone exposed at a point 300 feet to the 

south contains some magnetite and apatite. 

Sporadic cobbles and pebbles of metadiorite in most buried placer 

gravels of the tin belt indicate that unexposed bodies of metadiorite 

may occur in several places in the placer belt. In the gravels of 

Cache Creek oxidized cobbles of a coarse-grained serpentinized gabbroic rock similarly indicate an unexposed gabbroic body. Chromite, 

picotite, ilmenite, and magnetite found in the buried gravels of Deep 

Creek, Sullivan Bench, and elsewhere may be derived from serpentinized igneous rocks, but it is unlikely that the cassiterite of the 

placers was derived from these mafic rocks. 

The structure of the phyllite is too complex to be determined from 

the few available outcrops. Bedding planes are inconspicuous, and 

the dominant physical feature of the rocks is the foliation. Where 

observed the bedding is commonly parallel to the principal cleavage. 

In one outcrop on Sullivan Creek the foliation plane was parallel 

to the bedding in small drag folds, and in another outcrop the foliation was parallel to the axial plane of the drag folds. In general 

the strike of foliation is N. 60° to 75° E., nearly parallel to the trend 

of the placer belt. The dip of the foliation averages about 65° N. 

in the vicinity of the placers, and the axes of minor folds and crenu551722-61-2 
368 MLNERAL RESOURCES OF ALASKA 

lations pitch about 15° to 30° NE. North of the light sandy quartzite cropping out along Woodchopper Creek the cleavage and bedding 

dip southward at moderate angles, indicating a possible syncline. 

ALLUVIUM 

Most of the material composing the gravel deposits is of local 

derivation. The gravel deposits vary widely in thickness, in the 

amount of silt and clay, and in degree of stream wear and polishing. 

In the cross sections, plate 41, an attempt was made to distinguish 

deposits of angular gravels containing silt and clay from cleaner, 

more rounded gravels. The cleaner gravels contain most of the 

cassiterite and gold, but smaller amounts are contained in the angular, clayey gravels. Both types of gravel consist dominantly of 

graywacke, phyllite, sandstone, light-colored and dark quartzite, and 

quartz pebbles and fragments. The well-rounded gravels have more 

pebbles of quartz and light-colored quartzite and contain a few 

cobbles of granite and quartz-tourmaline rock. Rounded boulders 

of quartzite and sandstone were found at altitudes as high as 900 

feet along the west side of the canyon of Sullivan Creek. 

Angular gravels containing silt, muck and clay and some angular 

boulders occur most commonly along the hillsides. Some are interbedded with the rounded gravels, others lie on bedrock buried beneath undisturbed Quarternary silts and mucks, and still others are 

interbedded with the mucks or are forming by disintegration, creep, 

and wash acting on the bedrock areas. Hence, they have a wide 

range in age. 

The Quaternary silts and mucks that bury much of the Tofty area 

are partly massive and uniform in texture and partly interbedded 

in an irregular manner with angular gravels, peaty layers, silts containing much vegetal material, and even buried forests or forest 

debris. The total thickness along the placer belt ranges from a few 

feet in Tofty Gulch to 170 feet at Deep and Woodchopper Creeks. 

The origin and mode of accumulation of these deposits have been 

discussed by Mertie (1937, p. 186-198), Taber (1943, p. 1464-1548), 

and Tuck ( 1940, p. 1295-1310). The massive silts are loess, derived 

from glaciofluviatile outwash during the Pleistocene epoch. They are 

characteristically perennially frozen and contain large wedge-shaped, 

tabular, and irregular masses of clear ice which pinch out downward 

and are flat topped at the level of summer melting. The interbedded 

silts, sands, mucks, forest debris, and gravels occur most commonly 

along the borders of the deeply buried areas, partly in Recent alluvial 

fans. They are the result of the wash or creep of silt, muck and 

disintegrating bedrock from the higher areas. In the upland areas, 

silt forms a veneer a few feet thick. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 369 

ECONOMIC GEOLOGY 

The Tofty urea contains both lode and placer deposits, but as yet 

only the placer deposits have been worthy of exploitation. Much of 

the gold in the placer deposits was undoubtedly derived from the 

known types of lode deposits, but the source of the cassiterite in the 

placers is obscure. 

LODE DEPOSITS 

Quartz veins ranging in width from minute seams to veins several 

feet wide are common in nearly all the exposed Cretaceous rocks of 

the tin-belt area. Most are small and discontinuous, following the 

bedding and cleavage planes of the phyllite for short distances. In 

the quartzite beds they are generally larger and more persistent. A 

few large bull-quartz veins in the hills west of the upper canyon of 

Sullivan Creek strike N. 10° E. and dip 35° W., following cross fractures or jointing in the sandstone and graywacke. The veins in the 

phyllite are easily broken away from their wallrock along graphitic 

partings, but the quartz in quartzite beds has tight contact with its 

walls, resulting from partial replacement of the quartzite by vein 

quartz. Most of the quartz veins consist of milky-white quartz and 

show little or no sign of metallization. Except for limited local 

sericitization and silicification such as that a mile upstream from the 

Sullivan Creek placers, the walls of the quartz veins have not been 

altered. Some contain a few scattered cubes of pyrite, and several 

contain localized calcite crystals which weather out of veins leaving 

irregular cavities. Arsenopyrite occurs rarely in the veins, and 

galena is probably present since it is seen in some placer concentrates. 

No cassiterite or tourmaline have been found in place in any of the 

veins, although both occur in a few angular fragments of phyllite 

and sandstone in the gravels of several streams. Many veins have 

been sampled and assayed for gold by miners, but only a few assays 

have shown more than traces. A random sample collected and assayed by the Geological Survey from a small gossan zone in quartzite 

at the west side of Idaho Gulch near its head showed a tenor of 1.34 

ounces of silver per ton but no gold. No gold particles were seen 

during the panning of almost every exposed quartz vein or veinlet 

in the Tofty Gulch pit. 

Pyrite cubes, which apparently are not directly related to individual quartz veins, are sparsely disseminated throughout most of 

the phyllite and graywacke. 

At the northwest border of the intrusive mass at Hot Springs 

Dome are some quartz-siderite-galena veins, one of which was traced 

for 1,500 feet and another for 500 feet. Calcite, pyrite, chalcopyrite, 

and pyrrhotite also were noted among the primary minerals, but 

most of the outcrops consist of a heavy hematite gossan with a few 
370 M~ERAL RESOURCES OF ALASKA 

stains of malachite, azurite, and erythrite (cobalt), and a few small 

anglesite masses formed from galena. 

PLACER DEPOSITS 

The proved tin-bearing placer deposits of the Tofty area are restricted to a belt about 12 miles long and 1 mile wide, trending 

N. 60° E., from Woodchopper Creek across l\t[iller Gulch and Deep, 

Sullivan, and Cache Creeks of the Patterson Creek drainage basin, 

and extending across a divide to Gold Basin and Killarney Creeks, 

tributaries of Baker Creek. Most of the tin and gold have come 

from the 8-mile-long Patterson Creek part of the belt. Nearly all 

the deposits are buried beneath 10 to 170 feet of frozen Quaternary 

silt and muck. 

The placer deposits within this belt are restricted to several pay 

streaks 1 which in general are related to the drainage basin that 

existed before silt buried the area. Some features of the drainage 

basin are illustrated on plate 41. Many of the richest parts of individual placer deposits were found where an old channel had cut 

headward into a bench or terrace in the bedrock surface. In Miller 

Gulch, for example, the channels cut across a system of bedrock 

terraces causing local enrichment of the gravels at each terrace. But 

not all such intersections are rich, and conversely some of the richer 

deposits have no such existing physiographic relations but seem to be 

simply areas in which gold and cassiterite were concentrated in 

stream channels after which the adjacent upland surfaces were lowered by continued slow erosion under low stream gradients. 

Cassiterite and gold are most frequently found at the base of the 

lowest gravel. In some places particles of the two minerals, particularly gold, are worked into fractures and foliation in the soft weathered bedrock for several inches or even feet. Most gold particles in 

pay streaks at bedrock level are rounded and yellow. Cassiterite 

and gold are not abundant higher in the basal gravels, in gravel 

lenses in the silt and muck, or in the silt. Much of the gold in the 

upper part of the Quaternary deposits overlying the bedrock is very 

fine grained and well rounded, but angular gold with attached quartz 

particles is common, and some gold of this type has a greenish cast. 

The cassiterite particles in the silt are as well rounded and polished 

as those in the pay streaks lying on bedrock. 

The shape and relative abundance of the different rock types of 

gravels and boulders found in tailings piles are summarized in 

table 1. 

1 The word "pay streak" is used in this report as a convenient term for a natural 

concentration of gold or cassiterite. Whether a pay streak could be mined profitably 

would depend upon its grade, the mining method proposed, and economic conditions at 

the time. 
~ABLE 1.-.tWCIC types, snapes, ana retatwe aounaance oj gravels ana boutaers zn znazvzauat placer taztzngs 

[Numerals indicate relative abundance, in tenths. Letters represent: a, angular, sa, subangular, sr, subrounded, r, rounded. Lack of a numeral indicates less than 1 in 15, or, for boulders east of Idaho Gulch, no estimate of relative abundance] 

Gravels Boulders 

Locality Phyllite Quartzite Graywacke Sandstone Quartzite Quartz Quartz Sandstone Graywacke 

Dark Light Dark Light 

Cache Creek: 

Ferguson Draw __________ 2sr lsa 5sa r sa sr r sr -------- sr -------- Upper workings __________ 4a-sr sa 4a-sr sr sa sa-r sr sa sa sr a Lower workings __________ 2sa-r sa 6a-sr r sa sa-r sr sa sa r a Dalton Gulch _____________ lsa-sr sa 7a-sa sr sa a sa-sr sa sa sr a Harter Gulch (lower) _______ 3a-sr r 4sa lr sa sa sa-r sa sa sr sa Sullivan Bench ____________ 3a-sr sr 4a-sr lr sr sa sr-r sr sr sr-r a Tofty Gulch: 

Upper workings __________ 3a-sr sr 5sa sr a-sa a-sr a-sr sa sa sr sr Lower workings _________ 3sa-r sr 4sa-sr lsr sa sa a-sr sa-sr sa-sr sr-r -------- Idaho Gulch ______________ lsa 5sr 3sa-sr lr sa sa 3sa-sr a-sr 2sr-r 3r -------- Miller Gulch: 

Upper workings __________ 5a r 3a-sr 2r sr a-sr sa-sr sr sr 8r lsa 

Central workings ________ 4a sr-r 2a-sr 3r lsr sa-sr 3sa-r sr-r 3sr-r 4sr-r a-sr Lower workings __________ 

Innesvale Gulch (Deep 

Creek): 

3a lsr 2sr-r 4r lsr sa-sr 4sa-r lsr-r 2sr-r 3r a 

Good Hope claim ________ la lsa-r lr 5r lr lr 4sr -------- lsa-sr 5r a Olga claim ______________ 3a lr 3a-sr 2r sr lsr 4sa-r -------- 2sr 3r la-sr 

Borghill claim ___________ 6a sr 3sr -------- -------- a 4sr sr sr r 5a-sr 

Hokeley Gulch (Deep Creek): Cleopatra claim _________ 6a lsr-r lsr lr r la-r 5r lr 4r -------- -----·-- Lake claim ______________ 3a 2sr-r lsr 2r r la-r 6sa-r sa-r 2r lr -------- Golden Straw claim ______ 4a-r la-r lsa-r 2r la-r la-r 4r 2a-r lr 3r a VVoodchopper Creek: 

Upper workings __________ la-r 3a-sr r 3r 2r lsa-r 3r la 4r lr lr 

Central workings ________ 2a 2a-sr r 3r 2a-r la-r 3r la 3r 3r -------- Lower workings _________ la 3a r 3r 2a-r a-r 3r sa lsr-r 5r --------

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372 MINERAL RESOURCES OF ALASKA 

In the gravel sizes, angular to subrounded phyllite and graywacke 

of local derivation predominate, and the ratio of phyllite to graywacke increases westward through Deep Creek. Of the more resistant gravels, subrounded to rounded sandstone predominates and constitutes about a third of all gravels from Miller Gulch west. Along 

Idaho Gulch and to the east, subangular quartz and quartzite gravels 

are common in the tailings and pay streaks. West of the creek such 

gravels are more abundant and better rounded. Boulders on most 

creeks are subangular to rounded and are composed of quartz. In 

parts of the Miller and Innesvale Gulches and the Woodchopper 

Creek workings most of the boulders are rounded sandstone. Rounded 

light-colored quartzite boulders are common, although some angular 

dark quartzite boulders are found, especially in Hokeley Gulch and 

on Woodchopper Creek. Quartz boulders weighing 1 ton or more 

are common impediments to mining. 

The gravels lying on bedrock and containing local concentrations 

of cassiterite and gold range in thickness from 0 to 4 feet at Ferguson Draw, from 2 to 14 feet at Sullivan Bench, and from 30 to 40 

feet in lower Idaho Gulch and on much of Deep and Woodchopper 

Creeks . 

. Gravels of the placer deposits are locally iron stained by oxidation 

of pyrite eroded from the bedrock. For example, the gravels at the 

northeast corner of the Sullivan Bench pit, as it was in 1941, consisted of subrounded pebbles of phyllite, graywacke, sandstone, 

quartzite, and quartz interbedded with short gray sand lenses, the 

whole cemented weakly by reddish-yellow iron oxide. The underlying bedrock consisting of soft, weathered, dark graphitic phyllite 

was not notably iron stained. 

Among the gravels and boulders of the placers are less abundant 

rock types worthy of special mention because of their possible genetic 

association with the cassiterite. On lower Deep Creek, in Idaho 

Gulch, and on Cache and Killarney Creeks, cobbles of coarse-grained 

biotite granite were found in the tailings and gravels. Monzonite 

pebbles and cobbles occur in the gravels of Killarney Creek, the 

headwaters of which drain the Roughtop Mountain monzonite area 

in the present physiographic cycle, but monzonite has also been found 

in Cache Creek gravels. Pebbles and cobbles of green and white 

metadiorite are common in the gravels of most of the creeks. As 

seen in this section, they consist largely of hornblende partly altered to chlorite and of calcic feldspar partly altered to zoisite and 

albite; some fresh hornblende crystals have augite cores; and most 

metadiorite contains small amounts of epidote, titanite, and apatite. 

In the Cache Creek gravels are cobbles of a coarse-grained gabbroic 

rock, similarly altered, but also serpentinized. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 373 

Well-rounded pebbles and cobbles of equigranular quartz and black 

tourmaline are sparsely but uniformly distributed throughout the 

gravels of the tin belt. The uniform texture of many of the cobbles 

suggests derivation from dikes of quartz-tourmaline rock or tourmalite. Many of the quartz-tourmaline pebbles, however, show relict 

structures suggesting replacement of folded schistose rocks. One 

subangular stone found by Waters ( 1934, p. 241) in Cache Creek 

tailings showed orthoclase, microcline, and quartz in sharp contact 

with a band of quartz and tourmaline. 

Pebbles containing brown ( dravite or magnesian) tourmaline are 

more closely associated with the cassiterite than the pebbles containing black ( schorlite or iron) tourmaline. Nearly all cassiterite pebbles contain brown tourmaline, and a small amount of quartz and 

altered fragments of country rock. Pebbles in which tourmaline is 

dominant are abundant in the gravels of Deep Creek and Miller and 

Idaho Gulches. They may be 6 inches or more in diameter. Some 

are subangular or subrounded, but most are as well rounded as the 

pebbles having a high concentration of cassiterite. A graded suite 

of cobbles ranging from cassiterite containing a small amount of 

tourmaline to brown tourmaline with a small amount of cassiterite 

could be assembled readily from the gravels and concentrates of most 

creeks. The cobbles would show similar brecciated textures throughout, and except for a slightly less metallic luster, stronger brown, 

and less density at the tourmaline end, the specimens would be difficult to distinguish by eye. 

Most cassiterite particles or pebbles range from ¥16 to 1¥2 inches 

in diameter and almost all are well rounded, but a few are definitely 

subangular. The cassiterite in the pebbles is largely very fine grained 

and is gray tinged by brown. It has a submetallic luster on wet or 

freshly broken surfaces. Some cassiterite is coarser grained, showing crystals as large as ¥3 2 inch. The coarser grained cassiterite is 

brown, and specimens may contain small vugs of cassiterite and 

quartz crystals. The gangue in the cassiterite pebbles commonly is 

brecciated quartz or tourmalinized sedimentary rocks ; the fractures 

are filled with tourmaline, quartz, and cassiterite, and the breccia 

fragments are partly replaced. Some cassiterite pebbles contain a 

small amount of yellow fluorite. 

Of particular genetic significance are the rare specimens of altered 

country rock in the placer gravels that show tourmaline and cassiterite. In a subangular brownish-gray phyllite fragment from Miller 

Gulch which was studied in thin section, fine brown tourmaline replaces all formerly micaceous layers, and dense tourmaline fills fractures across the schistosity. In and near the fractures are many 

small irregular elongate cassiterite crystals and also some bladelike, 
374 M~ERAL RESOURCES OF ALASKA 

almost opaque, poorly crystallized cassiterite grains. In the To:fty 

Gulch pit the writer :found a rounded cobble of brownish altered 

phyllite with a quartz-tourmaline veinlet, and a cobble o:f dark 

quartzite with an irregular quartz vein and a :few coarse crystals o:f 

tourmaline. In the Hokeley Gulch gravels an angular piece o:f sandstone was :found containing micaceous layers altered to tourmaline 

and a :few tiny cassiterite grains. 

Heavy minerals in plac~r concentrates include chromite, ilmenite, 

pyrite, and some magnetite. Chromite was identified in the Sullivan 

Bench and Tofty Gulch pits and is abundant at Deep Creek, exceeding 10 percent o:f the concentrates obtained by the Survey sampling 

o:f the tailings o:f the Wild Goose, Golden Straw, and Marietta 

claims (pl. 41). It occurs as subrounded pebbles and is coarse 

grained with submetallic luster, lavender alteration, and a parting 

resembling a poor cleavage. Less abundant minerals in gravel-size 

concentrates are galena and arsenopyrite. Minerals in the pebblesize or sand-size concentrate, besides those mentioned above, include 

picotite (chrome spinel), zircon, aeschynite (niobate and titanate, 

chiefly o:f cerium metals), monazite, xenotime, apatite, epidote, brookite, anatase, barite, garnet, titanite, andalusite, and hypersthene. 

INDIVIDUAL PLACERS 

The creeks o:f the tin belt, particularly in the Patterson Creek 

drainage basin, were each studied in detail to find similarities or 

progressive variations that might determine their origin and assist 

in their :further exploitation. Mining operations in 1941 were being 

conducted on only five of the creeks. All unworked drift mines in 

the district quickly fill with water and ice and become inaccessible. 

Thus for most creeks, the sketches, statements, and deductions were 

made on the basis of the tailings on the surface, the recollections of 

miners of long experience, records o:f :former Survey investigations, 

and miscellaneous records. Not even in the open-pit mines currently 

operating were the exposures, tailings, and records entirely adequate 

for the study. 

CACHE CREEK 

Discoveries of cassiterite and gold were made on Cache Creek in 

1909 and 1910, and the principal pay streak on upper Cache Creek 

(pl. 41) was largely worked out between 1911 and 1913 by Sylvester 

(Jake) Howell and Gene Sullivan. Early work on the lower end 

of the pay streak was done by Cameron and Midgeley, according to 

Otto Hovley, owner of most of the claims in 1941. Since the First 

World War, Hovley and others have prospected on all sides of the 

original pay streak and in Ferguson Draw, a minor tributary. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 37 5 

Parts of the original pay streak were very rich. Hovley took 26.3 

ounces of gold and a large amount of cassiterite from a pillar, in 

1 day's work. Other parts were of low grade, restricting early 

mining to small areas of rich ground. Cassiterite and gold were 

generally found together, but prospecting showed a small streak 20 

feet east of the head of the main gold-cassiterite pay streak that 

yielded 10 to 12 pounds of cassiterite to the pan or about 1,500 pounds 

per cubic yard, but it contained too little gold to be of economic 

interest at the time. On the other hand, some pay streaks worked 

at the upper end of Cache Creek in the 1920's contained coarse gold 

and very little cassiterite. The cassiterite occurred as polished pebbles with a brecciated texture similar to that found on other creeks. 

Most of the gold at the head of the Cache Creek pay streak was the 

size of bird shot; some nuggets were as large as 4 ounces, whereas 

at the tail and in Ferguson Draw the gold was finer and in well-worn 

flakes. One prospector found a cassiterite concentration of low gold 

content 300 feet south of the southernmost tailings on Cache Creek, 

under 70 feet of Quaternary muck. 

The gravels of Cache Creek are mostly phyllite and graywacke of 

local derivation and are angular to subangular. For the most part 

the pay-streak gravels are well stream sorted and are overlain by 

about 4 feet of poorly sorted graywacke fragments, muck, and ice. 

The channel of the main pay streak is sharply cut into the phyllite 

and graywacke bedrock and is buried about 50 feet under Quaternary 

silt and muck. Parallel to it and sometimes branching from it or 

returning to it are other channels, about 10 or 20 feet deeper or 

shallower than the pay-streak channel, in which placer concentrations have not been found. 

In Ferguson Draw the gravels are thin or absent, and approximately 40 feet of Quaternary muck lies directly on bedrock placer 

concentrations in some places. Silicified phyllite is common in the 

gravels, and several well-rounded boulders of quartzite and quartz 

as large as 3 feet in diameter have been found. The pay streak 

yielded approximately 0.3 to 0.4 ounce per square foot in gold and 

0.1 to 0.4 pound per square foot in cassiterite. It terminates upstream against bedrock terraces, above which the paystreak is buried 

by Quaternary muck reduced from 40 to about 18 or 20 feet in the 

line of the channel. Drilling showed some cassiterite on the shallow 

north bench of the Ferguson Draw channel. . 

Unusual gravel fragments and boulders found in the tailings of 

Cache Creek include biotite granite, weathered monzonite, me.tadiorite, serpentinized gabbro, tourmalite, chromite, and ilmenite, all 

mentioned in the general discussion on placer deposits. 

551722-61-3 
376 MINERAL RESOURCES OF ALASKA 

DALTON GULCH 

Pay streaks in the Dalton Gulch area were first worked about 

1910. Since the First World War they had been neglected except 

for scattered prospecting. None of the miners and prospectors who 

did the work remain in the district. The northernmost tailings 

shown on the sketch, plate 41, were produced by Dick Richards, who 

made one of the earliest cassiterite shipments from the Tofty district; the other tailings were produced by Dietz, Kobich, and others. 

One pay streak was reportedly 60 feet wide, but most were small 

and discontinuous. The gravel was only 2 to 4 feet thick, and the 

total overburden was about 60 feet. The bedrock was terraced, with 

the richest placer concentrations on the steeper slopes. Most of the 

pay streaks averaged $0.50 per square foot in gold at the old price 

of $20.67 per ounce, but some yielded $10 per square foot. From the 

recollection of local residents and from the tailings samples collected 

by the Survey, it seems that cassiterite was less abundant in Dalton 

Gulch than on neighboring creeks. 

East of Dalton Gulch toward upper Cache Creek are scattered 

prospect holes reportedly 60 feet deep. Panning by the Survey dis-

~losed cassiterite and gold on two dumps near Dalton Creek and on 

most dumps near Cache Creek. Observation of the dumps near the 

shafts verifies the recollection of the miners of the district that the 

gravels in this area were thin or absent and that the silt and muck 

deposits lay directly on bedrock and on the local small tin cassiterite 

and gold concentrations. 

Gravels at Dalton Gulch consist largely of angular graywacke and 

phyllite of immediate local derivation but include some subrounded 

sandstone and quartz cobbles. 

HARTER GULCH 

The principal work on Harter Gulch (pl. 41) was done by Richards in the early years of mining in the area. He reportedly produced $90,000 in gold in one summer from one small area but found 

only low concentrations adjoining it, and comparatively little cassiterite. The Survey tailings sampling indicated a low cassiterite 

content in the Harter Gulch workings and showed more gold remaining in the tailings than in those from most other creeks. The gravels are largely angular phyllite and graywacke, containing some 

rounded sandstone. 

Half a mile northward from the Richards workings along the 

center of the valley of Harter Gulch are small gravel piles containing some cassiterite and considerable gold. Their appearance 

suggests that the gravel piles were not well washed by the prospector and that this accounts for their high cassiterite and gold content. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 377 

SUIJ.IV AN CREEK 

The principal pay streak on Sullivan Bench 2,000 feet east of the 

present course of Sullivan Creek (pl. 41) was located shortly after 

the original discovery of gold in Tofty Gulch in 1907. Its drift 

mines supplied a large part of the early output of the Tofty district. Ground worth $20 per square foot (gold at $20.67 per ounce) 

reportedly was mined in one place, although the ground averaged 

more nearly $3.50 per square foot. More than 16 men filed in 

August and December 1907 as owners of the several single or association claims that covered the pay streak, but claim ownership was 

later consolidated. The principal drift mines were operated for 

several years by Howell. Production was curtailed in 1912 and 

1913 by flooded mine workings and from 1918 to 1921 by high cost 

of labor, material, and freight. Hydraulic operations were started 

in the early twenties. About 1928, options were taken by the Alaska 

Gold Dredging Co., Ltd., a British firm which in 1929 conducted 

extensive testing of Sullivan Bench. Much of their drilling program is shown in plan and in cross section on plate 41. They were 

not satisfied with the results of their drilling, and the property 

passed to Hans Tilleson and Arthur L'Heureux who operated from 

1929 through 1931. After the price of gold rose from $20.67 to $35 

they sold to the Cleary Hill Mines Co., which operated a lode mine 

in the Fairbanks district. The Cleary Hill Mines Co. started extensive stripping and ditch building in 1934, and brought in bulldozers, dragline, scrapers, and large pumps. Stripping with hydraulic giants was done every summer and mining in the pit was 

done about every alternate summer. 

Much of the area originally drift-mined had been stripped and 

reworked by 1941; the gold recovery has been $0.40 to $0.55 per 

square foot at $35 per ounce, and the cassiterite recovery about 0.02 

pound per square foot. The old workings are outlined by a network of clear ice tracing the drifts, crosscuts, and small stoped areas; 

ice impedes open-pit operations because it does not thaw as rapidly 

as the adjacent virgin gravels. The gravels are 2 to 14 feet thick, 

averaging about 6 feet, and are overlain by 40 to 50 feet, locally 70 

feet, of silt and muck. Almost all the gold and cassiterite are in 1 

to 2 feet of gravel lying directly on bedrock, but some cassiterite 

has worked down into fractures and bedding planes for a few inches, 

and gold may be found in the bedrock to a depth of 2 feet. The 

bedrock is largely soft graphitic phyllite, which below a depth of 

1 or 2 feet is not weathered enough to oxidize the disseminated 

pyrite crystals. Some gravels are iron stained or weakly cemented, 

probably from oxidation of pyrite eroded from bedrock when the 

gravels were deposited. The gravels are 30 to 40 percent sub-
378 MINERAL RESOURCES OF.ALASKA 

angular to rounded dark phyllite, 40 to 50 percent subangular to 

subrounded graywacke similar to some observed in the bedrock of 

the pit, 10 to 15 percent rounded yellowish sandstone pebbles, and 

a few percent each of subrom:ided light-colored phyllite not represented in the pit bedrock, subrounded dark quartzite pebbles, and 

angular to subrounded quartz pebbles. Boulders up to 30 inches in 

diameter of quartz, dark and light-colored quartzite, and lightcolored sandstone, all subrounded to rounded in shape, are common. 

Cassiterite pebbles are characteristically well rounded and polished. 

Many pebbles of quartz and quartzite can be found, even 8 to 10 

feet above bedrock, that are as well rounded as the cassiterite. In 

addition to the abundant cassiterite, the concentrates contain ilmenite, picotite, chromite, pyrite, magnetite, and more rarely galena, 

.arsenopyrite, native copper, zircon, monazite, aeschynite, xenotime, 

apatite, brookite, and anatase. 

The frozen silts and mucks overlying the gravels are nearly uniform in texture and appearance, but show certain minor color differences. At the west edge of the pit in 1941, the silt is predominantly brown and gray. Tints of green and greenish-yellow are 

less common. At most places the brown-tinted silts lie either directly on the top of the gravel layer or on top of local lenses of 

mixed gravels and silts, and are about 10 feet thick. Overlying 

them is a layer of gray-tinted silt 10 to 25 feet thick, followed by 

15 to 30 feet of brown-tinted silt up to the moss roots. However, 

drilling shows rapid and substantial thickening and thinning or 

pinching out of the various layers, both horizontally and vertically, 

in a highly irregular manner, also local inversion of the stratigraphic order described above, and local inclusion of lenses of one 

tint within layers of the other tint. At the northeast corner of the 

pit as it was in 1941 and on the M-M' cross section (pl. 41), the 

silts are more complex in structure, due particularly to lenses of 

creep and wash material, mixed with muck and silt, washed down 

from the higher hillside to the northeast while the more uniform, 

massive Quaternary silts were accumulating. The remains of extinct vertebrates, including the mammoth, bison, and horse, as well 

as much forest debris, are common. in the muck and silt. 

In the Sullivan Bench area, section L-L', plate 41, shows the pay 

streak to have been on the top and west slope of a bedrock bench, 

but not to have been in the deeper bedrock channel to the east. The 

same relatively barren channel was found at the southeast corner 

of the pit. Drilling shows bedrock altitudes in the barren areas 

west of the pay streak, sections K -K' and G-G', plate 41, to be 

about the same as those in the pay streak, with the same normal 
TOFTY TIN BELT, MANLEY HOT SPRINGS. DISTRICT 379 

gradient from north to south in the direction of the streak~ -· Iri. 

general the cassiterite concentration varies directly with the gold 

concentration, but at the north end of the pit there were notable 

local variations in ratio, and south of the pit the cassiterite concentration remains the same, whereas the gold concentration lessens. 

The bedrock in Sullivan pit shows no direct genetic association 

with the cassiterite. It consists of dark-gray phyllite, some of 

which is graphitic, and a few graywacke beds. The bedding _and 

cleavage largely coincide. The dip ranges from 37° to 71° NW., 

averaging 50° to 55°, and the strike ranges from 47° to 58° NE. 

Crenulations where present pitch 30° to 33° N., and a drag fold 

observed at one point has the same pitch. Locally minor fracture 

or shear zones are parallel to the strike. Discontinuous quartz veins 

or lenses are present, seldom exceeding 10 feet in length or 6 inches 

in thickness, and are generally localized in or near zones of fractures and shear. In addition to milky quartz the lenses include 

some calcite and pyrite, but no biotite or tourmaline was found. 

The walls of the lenses 'are sharp and in most places are defined by 

a graphitic seam, which is a plane of easy parting. 

TOFTY GULCH 

The first gold discovery in the tin-belt area was made in Tofty 

Gulch by C. P. Snyder and George Kemper in the winter of 1906-7. 

Kemper posted his notice for the Discovery claim on July 20, 1907, 

and filed his claim on September 18 in the Rampart recording district. Snyder also posted a location notice, on the adjacent American 

Eagle claim, on July 20, 1907. Claims were located by M. ·Harter 

and Adolph Bock 3 and 4 days later, respectively, and in August 

of that year the remaining Tofty Gulch area plus the Idaho Gulch 

and Sullivan Bench areas were staked by other prospectors coming 

into the district, especially from Eureka and Rampart. The Discovery and American Eagle shafts were on the lower or south end 

of the Tofty Gulch pay streak just below a bedrock bench shown 

on section D-D', plate 41. In 1908 a mile of ditch from Sullivan 

Creek was constructed, and in 1909 about 75,000 square feet of bedrock was uncovered by Joseph Eglar, H. C. Wallick, and others. 

These operations upstream on Tofty Gulch from the Discovery claim 

were described in 1911 by Eakin (1913, p. 33) as follows: 

On Tofty Gulch a considerable open cut has been made on a bench on the 

h1llside about 1,000 feet from Sullivan Creek. The deposit consisted of 4 to 6 

feet of gravel covered by several feet of yellow silt and black muck. Large 

boulders were very common in the top layers of the gravel and some were 

found in the lower part of the silt. The black muck contained a great many 
380 MINERAL RESOURCES OF ALASKA 

remnants of trees, which added considerably to the difficulty and expense of 

mining. In working the deposit the top layers of muck and silt were groundsluiced otr, dynamite being employed to break up the tangle of wood debris in 

places, after which the gravels were carried to the sluice boxes with a steam 

scraper. 

The first 1,200 pounds of cassiterite was shipped from the district by Eglar in 1911. Ground sluicing of Tofty Gulch continued 

through 1912, and some drift mining was done in adjacent ground. 

For many years there was very little mining or exploratory activity, except for the limited drilling program of the Alaska Gold 

Dredging Co., Ltd., in 1929, until the acquisition of the property 

in 1934 by the Cleary Hill Mines Co. The pit in 1941 represented 

a reworking and upstream extension of the old pit. The upper 2 or 

3 feet of the soft bedrock was sluiced along with the gravel to 

recover the gold and cassiterite that had worked down into fractures and cleavage planes. Cleary Hill Mines Co. brought in bulldozers to move the soft bedrock, used hydraulic giants instead of 

ground sluicing, extended water ditches, and deepened drains. A 

caterpillar dragline bucket stacked the tailings. 

Both in the present erosion cycle and in the older cycle represented by bedrock configuration, Tofty Gulch is a minor physical 

feature, a small draw entering Sullivan Creek from the northwest. 

The slope of the gulch in both cycles averages about 5 percent or 4°. 

No sharply defined channel confines the placer concentrates. Rather, 

as may be seen on plate 41, the pay streak or streaks have limited 

accord with terraces a few feet high and with minor channels in the 

bedrock. The richest pockets are said to have been found on the 

slopes of the terraces, but as plate 41 shows, concentrations of cassiterite and gold were found both above and below such terraces, 

with the apparent axes of the pay streaks crossing the terraces at 

an oblique angle. The terraces are stream cut, forming angles of 

30° to 90° with the prevailing strike of the bedrock. 

In Tofty Gulch most gravels are angular graywacke, phyllite, 

and quartz, of immediate local derivation, particularly those gravels near the steeper side slopes of the gulch or off to the side of the 

pay streaks. Gravels lying directly on bedrock and containing the 

cassiterite and gold concentrations, however, include a significant 

percentage of well-rounded, resistant rocks, particularly sandstone 

and graywacke but also contain quartz and quartzite, especially 

among the coarser gravel. The abundant boulders of Tofty Gulch 

are mostly angular to subangular, but a few are subrounded. Yellow-stained milky to glassy quartz boulders predominate and are as 

large as 2 tons. Large dark quartzite boulders are also abundant, 

and some are more rounded and polished than most of the quartz. 

Unusual rock types among the gravels and boulders. include meta-
TOFTY TIN BELT, MANLEY HOT SPRINGS'" DISTRICT 381 

diorite, tourmalite, and two cobbles of special interest, one of brown 

altered phyllite containing a quartz-tourmaline veinlet and the other 

of dark quartzite containing an irregular quartz vein and a few 

coarse crystals of tourmaline. 

Gravel thicknesses are as much as 7 feet, and average about 3 

foot. Iron staining of gravels is widespread but not universal. Be· 

neath the stained gravels the upper foot of weathered bedrock at 

places is also somewhat iron stained. 

Bedrock exposures in the Tofty Gulch pit were the best in the 

district at the time of the investigation, and were studied in detail. 

The quartz veins observed largely conform with the strike of the 

cleavage and bedding of the phyllite and graywacke. Except in the 

vicinity of drag folds and in zones of shearing, the prevailing strike 

ranges from N. 70° E. to S. 80° E., averaging about N. 85° E., and 

the dip ranges from 55° to 80° N., averaging about 68°. Crenulations and drag folds where present pitch about 20° to 50° NE. 

One such drag fold is domed, and has a local pitch of 3° SW. for 

10 to 2o feet. Reliable observations on such structures could be 

made only along the drainage ditches which are dug from 5 to 10 

feet into the bedrock, as the bulldozers and dragline scraper have 

completed the disturbance of the higher bedrock layers that was 

started by natural processes before burial beneath the gravel and 

silt, or else they have covered the bedrock with tailings. Zones of 

shearing occur along these drainage ditches at about 50 feet, 200 feet, 

and 400 feet north and northwest of the highway bridge in the pit, 

and 75 feet, 150 feet, and 350 feet southeast of the bridge. Minor 

shears were observed at many other places. The shear zone 200 feet 

north of the bridge is comparatively extensive; it is about 60 feet 

wide and shows displacement in its southernmost 15 feet. Some 

subsequent minor cross shearing of northwest strike was observed 

here and in the northernmost shear zone exposed, but most shear 

planes nearly parallel the phyllite bedding. 

The rocks exposed along the drainage ditches in Tofty Gulch pit 

were studied in detail. The dominant rock is phyllite, which ranges 

in color from medium gray to black. Interbedded gradationally 

with the phyllite are beds of graywacke, a few feet thick, spaced 10 

to 100 feet apart, similar in color to the gray phyllite, and not 

much more resistant to weathering. The graywacke beds thicken 

and thin or pinch out along their strike und are some what difficult 

to trace. The black phyllite, which occurs especially in the lower 

500 feet of the pit area, is more massive and has poorer cleavage 

than the common gray phyllite, and is relatively free of graywacke. 

At a point 400 foot south of the bridge, however, it surrounds a 

lens of light-gray phyllite and light-colored graywacke. These rock 
:382 ;MINERAL RESOURCES OF ALASKA 

types were observed in the gravels but not elsewhere in the bedrock 

areas of the tin belt proper exposed at the time of investigation. 

South of the black-phyllite area is a massive graywacke bed. 

Biotitization, tourmalinization, or other mineral alteration commonly associated with tin mineralization were not found. The only 

mineralization consists of small discontinuous quartz veins lying 

mostly in or near the shear zones and parallel to the bedding, and 

the abundant, widely disseminated pyrite found everywhere in the 

phyllite below depths of 1 to 3 feet. The quartz veins are milky and 

contain a small amount of calcite and pyrite, rarely chlorite. Most 

of the veins and shear zones were panned by the writer, and none 

showed either gold or cassiterite. Pyrite is used as a depth index in 

both mining and drilling in the pit and elsewhere; when the bulldozer, dragline scraper, or drill hits pyrite, it is assumed to be in 

relatively fresh bedrock below the depth to which placer gold and 

cassiterite have penetrated. 

As in the Sullivan Bench pay streak, the downstream extension 

shows gold and cassiterite for several hundred feet, but has not yet 

been worked by open-pit methods because the bedrock is lower there 

than the existing drainage ditch, preventing the disposal of slimed 

tailings. Some drill holes indicate local streaks rich in cassiterite 

and relatively poor in gold. Eastward toward Sullivan Bench the 

drilling shows that fine gold occurs in traces but that cassiterite is 

absent except in three drill holes on section G-G' (pl. 41). 

IDAHO GULCH 

Most development on Idaho Gulch was done early in the history 

of the district by several of the men who made the original discovery on Tofty Gulch. Placer concentrations are distributed over a 

large area of bedrock but are in general small, discontinuous, and 

not particularly rich. An exception was a very small area containing an exceedingly rich pay streak from which a quarter of a 

million dollars in gold were taken in 1911. Such concentrations are 

called spots and were described by Eakin (1915, p. 240) in 1914 as 

follows: 

The simplest forms are rudely elliptical in outline and have a relatively rich 

central area, away from which the gold tenor and the size of particles decrease 

to the margin of profitable ground. Such placer spots are developed locally 

on the surface of bedrock terraces. Some of them appear upon a single terrace. 

More complex forms are in places developed upon several closely spaced terraces, and it is not uncommon to find a great variation in the elevation of 

bedrock in a single mine, the surface being everywhere sensibly flat except in 

the terrace scarps. In one mine $200,000 is said to have been produced almost 

entirely from a space of 5,000 square feet. On higher terraces at the same 

locality several other small areas of but slightly lower tenor were mined. Still 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 383 

other mines have shown small areas containing $10 to $30 in each square foot. 

The minable area of individual spots ranges from a few thousand square feet 

to a few- acres. 

Spots are not confined to the Idaho Gulch area and are indeed characteristic of every creek in the tin belt. 

In the lower Idaho Gulch area the general bedrock slope is very 

gentle and no single channel crosses the bedrock terraces to give 

strong linear control to spot and pay-streak distribution. Furthermore, a gentle southeast slope unbroken by any suggestion of a valley exists on the surface in the area of the spots. 

The Idaho Gulch area was not always known widely under that 

name but was referred to in some earlier reports as "Sullivan Creek 

valley below Tofty." The history of the area is therefore somewhat 

confused with that of the other placer areas. The last-recorded 

extensive drift mining in Idaho Gulch was done in 1912 and perhaps in 1913. Since then several prospecting shafts were sunk and 

a small amount of ore has been produced. From 1917 to 1919, as 

elsewhere in the tin belt, the older tailings dumps were reworked 

for cassiterite. Some drift mining between 1919 and 1921 recovered 

about 0.77 pound of cassiterite per square foot of bedrock. The 

ground in the vicinity of the old workings was drilled in 1929 by 

the Alaska Gold Dredging Co., Ltd., and in 1940 to 1941 by the 

Cleary Hill Mines Co. Most of the prospecting in Idaho Gulch 

from about 1916 to 1941 was done by Jack Donahue. Cassiterite 

was found in small quantities in several of his prospect holes, including several as far up_ the creek as 1,500 feet above the road; 

gold, but no cassiterite, was found beyond that point by Donahue. 

The cassiterite found at the points fartheast upstream was similar 

in most respects to that found in greater concentrations in the principal pay streaks, except that according to Donahue it was all in the 

sand and fine-gravel size range and did not include a large proportion of the coarser gravel sizes as is common in the pay streaks. 

The depth of burial at the upper limit of the cassiterite ranges from 

about 24 to 32 feet, including 8 to 12 feet of gravel-muck wash. 

A.t the lower end of Idaho Gulch cassiterite has been found in 

prospect holes as far as 2,500 feet south of the road (pl. 41), where 

the overburden is 80 to 85 feet and the gravels are only 2 to 5 feet 

thick. A.n 85-foot shaft was sunk and considerable drifting done in 

1915 near the small lake between lower Idaho and Miller Gulches; 

however, no cassiterite and only a very small amount of flour gold 

were reported. Panning of the dump surrounding this shaft by the 

Survey showed no cassiterite. 

In 1941 a small pay streak or spot in Idaho Gulch north of the 

old workings was found and outlined by drilling by the Cleary Hill 

551722-61--4 
384 MITNERAL RESOURCES OF ALASKA 

Mines Co., and was later drift mined under a lease. It was definitely localized by a small buried gully cut back into a bedrock 

terrace. 

Compared with tailings along creeks to the east, the Idaho Gulch 

tailings contain a higher proportion of light-colored gravels and 

boulders. In the gravel sizes, angular to subrounded, light greenishgray chloritized phyllite is more abundant than the typical angular dark graphitic phyllite of the tin belt. Quartz boulders and 

subrounded to rounded light-colored quartzite and sandstone boulders 

are common. Subrounded graywacke gravels are the most abundant 

of the dark gravel constituents. Well-rounded cobbles of brecciated 

quartz containing brown tourmaline and some cassiterite are common in the boulder piles. 

MIIJ.ER, GULCH 

The discovery of the gold and cassiterite placers in lower Miller 

Gulch was the result of drilling in 1912 (Eakin, 1915, p. 241, 243-

244) . The successful drilling program was financed by half the net 

return from the mining of the richest spot in Idaho Gulch the preceding year. Other discoveries were then made by prospect shafts 

upstream in Miller Gulch, and by the end of the year mines were 

located at intervals for almost a mile along the stream. The largest operators were Sy Ivester Howell in lower Miller Gulch, Howell 

and Stewart on the central workings, and Stewart, McLean, and 

McKinzie on the upper reaches of the pay streak. In 1914 there 

were 5 operations in Miller Gulch employing 112 men, but in 1915 

the operations were reduced. Except for recovery of cassiterite from 

the tailings in 1917 to 1920, and prospecting by John Radovich 

about 1923, the creek received little attention until 1930 and 1931 

and again from 1937 through 1940, when there were small driftmining operations. Recorded recent cassiterite recoveries range 

from 0.2 to 0.5 pound per square foot of bedrock. 

The Miller Gulch pay streak is buried under Quaternary silt and 

muck, which is 35 feet thick at the north end and 120 feet deep at 

the south end. The present surface topography is a very gentle 

southward-facing slope; the bedrock slope is the same, with the 

exception of some prominent bedrock terraces of which at least 3 

have 10- to 20-foot south escarpments. Their approximate locations 

are indicated on the sketch of the Miller Gulch workings (pl. 41) , 

as reported by Tom Dean who was for many years a resident and 

prospector on the creek. 

The Miller Gulch pay streak is long, narrow, and continuous compared to those on most creeks. This is unusual considering the apparent lack of a confining major bedrock channel. Depths to bed-
TOFTY TIN BELT, MANLEY HO'l' SPRINGS DISTRICT 385 

rock for several hundred feet east and west of the pay streak are 

nearly the same as depths as the comparable points on the pay 

streak. The only reported channelling consists of some short, sharp 

gullies cut back into the various bedrock terraces, in or near which 

the richest gold and cassiterite concentrations were found. In the 

upper 2,000 feet of workings there were 2 pay streaks about 200 

feet apart, lacking rich spots and lying largely on one terrace. Two 

rich notches were found in the terrace escarpment, below which the 

channels coalesce. 

In 1914 mine operators on Miller Gulch tried to recover cassiterite 

during gold sluicing. About 30 tons of cassiterite concentrates were 

recovered at one drift mine. The proportion of cassiterite in the 

gravels was said to be as high as anywhere in the tin belt, a statement verified by the sampling of tailings by the Survey, particularly in the lower workings. 

In the gravel tailings of Miller Gulch, the dominant rock type is 

angular dark phyllite, constituting half of all gravels at the head 

of the pay streak and a third at the foot. The proportion of angular to subrounded graywacke in the gravels also drops, from a third 

at the upstream end to a sixth at the lower end. Rounded sandstone and subrounded quartz gravels are fairly evenly distributed over 

the mile of tailings dumps. Rounded rnetadiorite pebbles are common in the upstream tailings, and less co:mmon downstream. Among 

the boulders, rounded sandstone predmninates at the head of the 

creek but quartz and light-colored quartzite boulders are equally 

abundant in the lower workings. The gravels lying on bedrock are 

reportedly thick, totaling as much as 40 feet at the south end of the 

pay streak. It is said that they were freer from silt and muck than 

gravels on most other creeks, a condition also suggested by the relatively clean, well-sorted tailings piles. Like gravels on the other 

creeks to the west, the proportion of light-colored quartzite, quartz, 

and sandstone boulders and pebbles arnong the gravels is greater 

than on the creeks to the east. The concentrates contain more heavy 

minerals, other than cassiterite and pyrite, and the boulder and 

gravel tailings contain more brecciated quartz cobbles with brown 

tourmaline and small amounts of cassiterite. 

DEEP CREEK 

Present day Hokeley and Innesvale Gulches and the east tributary, Willow Creek, rise in inconspicuous gulches west of Miller 

Gulch and flow southward, then southwestward to form Deep Creek, 

an equally inconspicuous topographic feature. Ordinarily, as in 

Idaho, Tofty, Harter, and Dalton Gulches, there is little or no continuous flow of surface water, and the stream channels are lost in 
386 MITNERAL RESOURCES OF ALASKA 

the moss and muskeg south of the slope where they rise. However, for lack of any other natural features suitable for geographic 

reference in describing the location of the placers of the area, it has 

been the custom to use the names, "Innesvale" for the eastern and 

"Hokeley" for the western placers along Deep Creek between Miller 

Gulch and Woodchopper Creek. Some placer mining claims of 

Deep and Woodchopper Creeks are plotted on plates 40 and 41 for 

further geographic reference. 

The rich ground of Hokeley Gulch at the junction of the Golden 

Straw, Wild Goose, and Marietta claims was discovered as the result of drilling on the Wild Goose claim by Adolph Bock in March 

1913, and was worked through 1916, during which time an average 

of 50 men was employed. Eakin (1915, p. 243) described the deposit in 1914 as follows: 

The shafts penetrate 130 feet to bedrock, most of the way through light-colored 

stratified and frozen silt. A stratum of gravel 6 to 8 feet thick lies on bedrock beneath the silts. The gold is well concentrated on bedrock and in the 

lowermost gravels. It is well worn and of fine, even texture, indicating considerable transportation and assortment prior to its deposition in the present 

placers. Although the deposit has not been fully outlined, margins have been 

located which indicate that it is not part of a continuous pay streak but is 

irregularly terminated in all directions. The gravels vary in gold content from 

place to place, ranging from those that are barely workable near the margin 

to some of very high tenor about the central shaft. There are considerable 

areas that yield $4 to $6 or more to the square foot, and the entire minable 

area is thought to extend over several acres. Stream tin occurs with the gold, 

but no special attempt was made to recover it. There is considerable difference in depth between the two shafts, though they are only a few score feet 

apart. To the southeastward bedrock drops off to still lower levels. 

The northwestern part of the pay streak on the Wild Goose claim 

was mined in 1916 by Bock and Danielson. Reworking of cassiterite from tailings took place in the next few years. The less rich 

workings, which lie southwestward along the line between the Wild 

Goose and the Golden Straw claims, were operated by Besonen and 

McKenzie in 1916, by Fred Hanson about 1922-25, and by Henry 

Besonen and by Jarvi and Linder in 1938-40. The average cassiterite recovery from some of these later operations was about 0.5 

to 0.6 pound per square foot of bedrock. 

The pay streak northwest of the Cleopatra claim was mined by 

John Neilson and August Johnson in 1915 and 1916, until it was 

flooded as mining continued south onto the Cleopatra. They recovered 0.335 pound of cassiterite and 0.1 ounce of gold per square 

foot of bedrock. The tailings around the lake at the northeast corner of the Marietta claim were produced largely since 1929, by 

Bock and by Hanson and Albrecht. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 387 

In 1941, Hanson was mining the pay streak at the center of the 

northwest side of the Marietta claim (pls. 41 and 43A). The writer 

was present for a cleanup representing the mining of 1,317 square 

feet or 292 cubic yards of placer gravels said by Hanson to be only 

half as rich as other recently mined gravels.;2 The gold recovery 

was $1.85 per square foot or $8.32 per eubic yard for gold at $35 

per ounce troy. The cassiterite concentrate recovery was 0.064 pound 

per square foot or 0.288 pound per cubic yard, about a quarter of 

that recovered in recent years from neighboring operations. The 

mined thickness of gravels was 6 feet, and the overburden, mostly 

silt, was 134 feet. 

Upstream in the Innesvale Gulch area, Dellas and Hanson mined 

in 1918, and a spot west of the center of the Olga claim was worked 

by William Albrecht, Pete l\fellianic, and Tom Dean in 1925. Some 

work had also been done in 1924 on the west end of the Cleopatra 

claim by Sylvester Howell, but most of the mining of the Innesvale 

Gulch area since 1929 was done by Adolph Bock and by Hanson 

and Albrecht. Cassiterite recoveries ranging from 0.2 to 0.5 pound 

per square foot of bedrock were common in these operations. Both 

the north and the south end of the pay streak on the Rachel, Hard 

Luck, and Good Hope claims were flooded, causing loss of the mines. 

The gold and cassiterite pay streaks in the center of the Olga claim 

are spotty and discontinuous, and toward the south edge of the 

claim the gravels are thawed, making drift mining impracticable or 

difficult. 

Mertie (1934, p. 20-212) visited the large drift mine of Hanson 

and Albrecht on the pay streak at the west corner of the Olga and 

the north corner of the Cleopatra claims in 1931 when it was open 

and operating. The following is quoted from his description: 

The overburden consists of 5 or 6 feet of gravel on bedrock, overlain by 60 

feet of muck containing here and there layers of fine gravel, which in turn is 

composed mainly of quartzite, phyllite and slate but also includes vein quartz, 

much of which is vuggy and iron-stained. In places cavities may be seen from 

which pyrite has been dissolved. The gravel is subangular to poorly rounded 

and is not in general heavy, being composed of' cobbles a foot or less in diameter. But here and there in the drift are very large boulders, commonly 

quartz, and one such boulder of pure vein quartz 6 feet in diameter was observed, underlain by 2 feet of small gravel and cobbles. Also in places grea't 

slabs of country rock are found, underlain by g:ravel. Such conditions indicate 

that the concentration of the gold occurred almost in place, neither the gold 

nor the vein quartz having been transported any great distance. The gold occurs in the lower 2 feet of gravel and the upper foot of the bedrock. The surface of bedrock is very irregular and in plaees rises abruptly as much as 20 

feet. On such slopes gravel is usually absent and the muck rests directly upon 

2 The writer is indebted to Mr. Hanson for permh1sion to publish these detailed data 

concerning a part of his 1941 operations. 
388 MINERAL RESOURCES OF ALASKA 

bedrock. The best parts of the pay streak are on the tops of such high bedrock reefs, and the next best places are in the low saddles between the reefs. 

Little or no gold is found on the slopes. The bedrock itself is much weathered 

phyllite but in places is slate. The pieces of gold will average in weight about 

a grain or a little more, but nuggets worth as much as $20 have been recovered. * * * Large amounts of cassiterite are also recovered in the concentrates. 

This material is well rounded and occurs in all sizes from small grains half 

the size of a small pea up to pieces 6 inches or more in diameter. These larger 

pieces are usually of low grade-that is, 'the cassiterite is intimately mixed 

with vein quartz and country rock. * * * The concentrates also include a 

variety of other heavy minerals, of which the most common are ilmenite, 

pyrite, picotite, and magnetite. 

The nature of the bedrock surface and the pay streaks of Deep 

Creek can be only partly understood by reading the descriptions 

and mining history quoted above or by investigating the underground workings in drift mines that may be open and in operation 

at any given time. For complete understanding it would be necessary at least to have access to detailed maps of all workings on the 

creek and to have the location and log of all drill holes. Unfortunately this information is not available. From the records it is 

possible to locate recent drill holes only by reference to the claim 

on which they were drilled; this does not permit delineation of 

bedrock channels and terraces or the reconstruction of bedrock 

contours. 

Only by adding to existing records the recollections of the men 

who did the work and who remain in the district, Adolph Bock and 

Fred Hanson in particular, was it possible to draw the rough 

sketches of the Deep Creek placer deposits shown on plate 41. If 

the drill holes could have been surveyed, it would be possible to 

contour the entire bedrock area of Deep Creek and much of Woodchopper Creek. The most useful information the old drilling now 

affords to others than those who did the drilling is a record of 

depths of unconsolidated deposits in areas the size of a claim or 

larger and the frequency of gold and cassiterite in the drill cuttings. Such information is summarized in table 2. Records covering the 15 years of drilling before 1926 were not available for 

tabulation. 

The drilling summary and the sketches on plate 41 show that the 

richer placer concentrations of Deep Creek were buried about 120 to 

140 feet and that they lie in a zone a few hundred feet wide, along 

a bedrock terrace that trends about S. 60° W., corresponding to the 

strike of the bedrock phyllites. In general the individual rich 

spots are localized by gullies cutting across the face of the terrace, 

but in detail their reference to bedrock configuration is at many 

places obscure. Mertie is quoted above as pointing out that on 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 389 

steep bedrock slopes in the mine visited by him the muck rests directly on bedrock, and that the pay streaks are on the high bedrock 

reefs or in the low saddles between reefs. The writer concludes 

that the rich pay streaks were concentrated by gullying but not 

necessarily in the particular gullies most prominent at the exact 

time of burial of the deposits by the muck. After a pay streak was 

emplaced in a gully where it was later found by mining, either the 

gullies filled with gravel or, for other reasons, the streams coming 

from across the major terrace were diverted in many instances and 

began cutting in the adjacent weathered phyllite. These subsequent gullies concentrated whatever gold and cassiterite happened 

to lie in their minor drainage areas. If they deepened and grew 

sufficiently they could start to cut into the principal pay streaks or 

isolate them on local reefs. Such activity was then interrupted by 

deposition of muck. 

TABLE 2.-Summary of drilling by Adolph Bock, 1926-41 

Depth of drill holes 

(feet) 

TotaL___________________ 85 220 135 43 

Percentage _____________________ ------------ ------------ ---------- 100 

Number of drill holes 

20 

47 

21 

49 

5 

12 

t About 120 additional holes were drilled in this gulch north of the placers in search of a bedrock source of the cassiterite. 

NOTE.-Of the 241 holes drilled inside the area of the listed claims on Deep Creek that are shown on plates 40 or 41, 190 of them contained gold whether or not they contained cassiterite; 172 of them contained 

cassiterite whether or not they contained gold; and 3 contained cassiterite without containing any gold. 
390 ;MINERAL RESOURCES OF ALASKA 

The most important topographical feature in localizing the zone of 

the Deep Creek pay streaks is the terrace along whose frontal scarp 

most of the spots are distributed. The average depth of burial of 

the top of this terrace just north of the placers is between 80 and 

100 feet. The upper edge of the scarp nearly coincides with the 

north claim lines of the Good Hope, Olga, Cleopatra, and Marietta, 

dying out on the Wild Goose. The top of the main, upper terrace 

contains no large known placer concentrations. Drilling shows that 

both gold and cassiterite are widespread on top of this terrace, but 

are dispersed in small concentrations unsuitable for mining under 

1941 prices and costs. The relief near the escarpment is in general 

between 10 and 25 feet, and the slope is as steep as 45° in places. 

The escarpment is irregular in detail, owing to gullies which cut 

back into the terrace for as much as several hundred feet. Gold, 

cassiterite, and gravel concentrations in the gullies cut off sharply 

at the upper ends, and the top of the gravels in the gullies coincides 

with terrace level at many places. Pay streaks in general emerge 

from the gullies and disperse across the lower bedrock to the southwest amid other minor benches, terraces, and ridges. 

A lower terrace escarpment starts near the southeast corner of 

the Wild Goose and follows the Golden Straw claim line southwestward. One rich pay streak, at the junction of the Wild Goose, 

Marietta and Golden Straw claims, lies along this lower escarpment. 

In lower bedrock areas, many workings and drill holes penetrate 

about 150 feet of frozen ground and are flooded with water from 

the unfrozen ground below. For example, 4 of 12 drill holes were 

abandoned by Bock for this reason before reaching bedrock. 

The location of the principal bedrock drainage course in the Deep 

Creek area was not known in 1941, and pending geophysical work 

or more extensive drilling, it may remain uncertain. In the placer 

area the deepest ground is south of Pearl Fraction where several 

holes reach a depth of 170 feet or more. Bedrock drainage from 

the rich pay streak at the Wild Goose-Golden Straw claim corner 

would apparently have been eastward south of the Marietta claim. 

The main drainage course probably then swings southward toward 

the present low silt hill about a mile from the centerline of the tin 

belt (pl. 40). All that is known of the altitude and nature of the 

bedrock under this hill is that a few drill holes south of the crest 

reached bedrock generally at only 80- or 90-foot depth. 

The gravels lying directly on bedrock in the Deep Creek placers 

commonly range from 6 to 8 feet in thickness, but at many places 

gravels are in the muck as high as 25 to 40 feet above bedrock; they 

are interbedded with the muck in a manner which indicates that 

they were swept off the terraces. Mertie (1934, p. 212) observed 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 391 

gravel 40 to 80 feet above bedrock in the Golden Straw workings 

in 1922. Several drill holes have shown gold in layers of interbedded gravels high above bedrock. A hole drilled 500 feet southwest of the lake on the Pearl Fraction claim showed coarse gold of 

a greenish cast in a gravelly layer in the muck 30 feet above bedrock. Adolph Bock sunk a shaft on the line of the drill hole, but 

the extent of the gold in the gravelly layer was found to be very 

limited. 

Gold is also found above bedrock in the following places, among 

others: 80 feet below the surface in a 116-foot hole on the Cleopatra 

claim; 130 feet below the surface in a 140-foot hole near the west 

point of the Cleopatra claim; a rich streak of green gold 120 feet 

down in a 140-foot hole on the Marietta claim; and at severallev~ls 

in a second 135-foot hole on the Marietta claim. Cassiterite also 

occurs above bedrock locally, as in an 80-foot hole on the Olga claim, 

and 80 feet down in a 105-foot hole on the Wild Goose claim. 

In the tailings of Deep Creek, angular dark phyllite is the predominant gravel. It is particularly abundant from workings nearest 

to or cut into the crest of the terrace escarpment, where it constitutes 

40 to 60 percent of all the gravels. A few hundred feet away from 

the escarpment crest the tailings show a marked decrease in the proportion of angular dark phyllite. At the Innesvale end of the area, 

angular graywacke makes up most of the rest of the gravel near the 

terrace crest, but it is not abundant anywhere in Hokeley tailings. 

If the angular phyllite and graywacke of immediate local derivation 

are ignored, a pattern is seen in the distribution of the other, more 

rounded gravels. In the Innesvale area, sandstone gravels are the 

most abundant, particularly away from the top of the terrace escarpment. Quartz and light quartzite gravels are common, and lightcolored phyllite is found. In the Innesvale area, disregarding angular graywacke boulders, rounded and subrounded sandstone and 

quartz boulders predominate, light-colored quartzite boulders are 

common and dark quartzitB boulders are scarce. Among the uncommon rock types are quantities of quartz-tourmaline rock and some 

metadiorite. In the tailings from the heads of the gulches cut back 

into the terrace, such as those north of the Olga and Good Hope 

claims (pl. 41), rounded gravels are scarce or absent and the tailings 

show a few boulders and much angular phyllite. 

The rounded gravels in Hokeley tailings show an even distribution of rock types, with sandstone slightly predominant. The boulders are mostly quartz. Light-colored quartzite is common on and 

north of the Cleopatra claim, and sandstone is common on the Wild 

Goose and Golden Straw Claims. Unusual constituents include much 

quartz-tourmaline rock, with both black and brown tourmaline rep-
392 MINERAL RESOURCES OF ALASKA 

resented, much chromite, and rarely coarse-grained biotite granite. 

Chromite is found in most of the concentrates, but is especially 

abundant in the rich gravels at the north corner of the Golden Straw 

claim. It occurs as subrounded, coarse-grained pebbles and cobbles 

with submetallic luster, fair parting, lavender alteration, and high 

density, and makes up 5 to 20 percent of the concentrates. Its bedrock source may be some phase of one of the small basic intrusive 

bodies found in the belt along the slope of the ridge 2 miles to the 

north. The tailings are among the richest in cassiterite in the Tofty 

area; sampling by the Survey showed that 1 pile contained 4.3 pounds 

per cubic yard. 

Waters (1934, p. 238-239) found concentrates from both the Hokeley and Innesvale areas to contain cassiterite, ilmenite, picotite, zircon, pyrite, magnetite, aeschynite, and gold. In addition he found 

well-rounded monazite pebbles in Innesvale concentrates. 

WOODCHOPPER CREEK 

Gold and cassiterite were discovered on Woodchopper Creek in 

1913, and prospected and developed the following year. In 1915 and 

1916 the largest operations in the tin belt were those of Sylvester 

Howell, who worked these mines and others under the name of Howell 

and Cleveland, with Jennie Cleveland as his partner. They employed more than a hundred men on large-scale drift mining. For 

a few months they increased cassiterite recovery by duplicating 

sluicing, that is, by sluicing through one string of boxes while cleaning up a second. The town of Woodchopper grew rapidly, and 

died just as rapidly when the Howell and Cleveland operations were 

shut down. 

From 1917 until1919, F. Jorgenson and C. H. Clegg mined in the 

deep ground of the Lorain claim at the south end of the pay streak 

recovering much cassiterite, but they found that water flooded all 

mining attempts south of their workings. They recovered about 1.2 

to 1.3 pounds of cassiterite per square foot of bedrock. Jorgenson 

also worked at the north end of the principal pay streak on the 

Mohawk claim in 1915, and Hanson and Hasler continued work in 

this area in 1921. In 1926 and 1927, Hanson, Tilleson, and Linder 

mined extensively at the northwest corner of the present lake formed 

by surface subsidence over the lower Howell and Cleveland workings (pl. 41), and in 1941 Matt Jarvi mined for 2 months along the 

west side of the pay streak on the Mohawk claim. 

The ground on all sides of the Woodchopper pay streak has been 

prospected by drilling and shaft sinking by several people. These 

operations include the drilling by Adolph Bock summarized in 

table 2, as well as a line of prospect shafts crossing the Woodchopper 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 393 

Creek valley on claims of William Bargery 3,000 feet upstream from 

the north corner of the Mohawk. Cassiterite and gold have been 

reported at or near Bargery's shafts, and gold is found upstream, 

reportedly unchanged in character except that it is no longer found 

with cassiterite. At the upper end of the Mohawk claim 1 drill hole 

in 7 showed cassiterite and gold. 

The nature of the principal pay streak, which was largely worked 

out by Howell, is shown in the sketch on plate 41 as it was described 

to the writer by Adolph Bock and others. The bedrock on the 

Mohawk claim has considerable relief, but southward on the Lorain, 

except for a minor eastward-trending terrace on the west side it is 

nearly flat. The head of the Mohawk channel is buried about 100 

feet, whereas 0.3 mile south at the Lorain claim line it is buried 

about 150 feet, indicating about a 5-percent slope (allowing for the 

gently sloping surface). West of the Mohawk pay streak, bedrock 

rises rapidly for about 600 feet to the top of a bench that is buried 

only about 50 feet. The escarpment of this terrace swings away 

from the pay streak downstream, and west of the north Lorain claim 

line has a southwesterly trend. Half a mile west of the claims it is 

said to swing to the northwest, and more deeply buried ground is in 

line with the projected trend of the tin belt. East of the Mohawk 

pay streak some local, nearly barren channels were found below the 

bedrock terrace that extends from the Wild Goose claim on Deep 

Creek. South and southwest of the pay streak area the present surface is almost flat, sloping gently southward, and spotty records of 

drilling and shaft sinking indicate that the bedrock surface, buried 

170 to 220 feet or more, has about the same slope as the present 

surface. Many holes in this area were abandoned before they reached 

bedrock when they penetrated the upper layer of frozen silts and 

gravels. One 220-foot hole half a mileS. 60° W. from the southwest 

corner of the Lorain claim showed cassiterite and a small amount 

of coarse gold in thick gravels. 

The gravels in the Woodchopper pay streak are reportedly relatively thick. On the Lorain claim they are 40 feet thick. In the 

angular gravels of local derivation in the tailings, light-colored 

phyllite predominates over dark phyllite, and dark quartzite is abundant in the central and lower workings. Angular quartz pebbles 

are common. The rounded and sub rounded gravels consist mainly 

of sandstone, with small amounts of light-colored phyllite, graywacke, quartzite, and quartz. In the debris of boulder size, rounded 

quartz boulders are a third of the volume. Rounded light-colored 

quartzite boulders are ablmdant in the upper workings and decrease 

downstream, but the distribution of rounded sandstone boulders is 
394 MINERAL RESOURCES OF ALASKA 

the reverse. Unusual rock types such as the quartz-tourmaline rocks 

and metadiorite were much less abundant than on the creeks to the 

east. 

WEST OF WOODCHOPPER CREEK 

Part of the area west of Woodchopper Creek in the projected 

course of the tin belt has been discussed in the preceding section. 

Half a mile west of Woodchopper Creek a bedrock terrace impinges 

on the north side of the area, and cassiterite and gold were found in 

a 220-foot hole half a mile west-southwest of the lower Lorain corner. 

Several holes have been drilled a quarter to a half mile west of the 

Mohawk workings. Logs of some of these holes are summarized in 

table 2. Most of them are 130 to 152 feet in depth; 6 of 10 holes 

showed cassiterite; 5 of them did not show any gold. Mr. Bock reports, however, that cassiterite did not predominate in the heavy 

concentrate from those holes as it does in concentrates from holes 

to the east. 

In a shaft just west of the southernmost lake 2 miles west of 

Woodchopper bedrock was reached at a depth of 120 feet but no 

gold or cassiterite was found. Another shaft a short distance farther west penetrated gold lying on bedrock 210 feet below the surface; a boulder resembling cassiterite, probably brown tourmaline 

and quartz was found in the shaft, but no cassiterite. Cassiterite 

reportedly has been found in this area and for miles to the west, but 

no reliable confirmation could be obtained. 

GOLD BASIN AND KILLARNEY CREEKS 

In the Baker Creek drainage basin east of the Patterson Creek 

part of the tin belt (pl. 40), prospectors have found cassiterite and 

gold in a belt trending more eastward than the belt in the Patterson 

Creek drainage basin. The earliest recorded prospecting in this area 

was in 1912, when a large area of very low grade ground with 

irregular gold distribution was reported on Cooney Creek, tributary 

of IGllarney Creek. Both Gold Basin and Killarney Creeks were 

drilled in the next few years by Fred Hanson and Adolph Bock and 

by Sylvester Howell and William Bargery. Many shafts were sunk 

by different prospectors. Interest subsequently lagged until the price 

of gold rose, when random prospecting was resumed. The locations 

and logs of drill holes and prospect shafts were not available. Except for a few muck dumps at the collars of some of the old prospect 

shafts, a visitor in 1941 saw nothing in the area indicating the nature 

of the deposits on bedrock. The following comments are taken largely 

from the experiences of Fred Hanson, Otto Hovley, A. H. Rieder, 

and others who have worked and lived in the area. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 395 

In general cassiterite with gold is found on phyllite bedrock from 

south of where the main trail crosses Gold Basin Creek, to Killarney 

.Creek (pl. 40). Along Killarney Creek, cassiterite is abundant for 

1,000 feet but it is fine. One prospector says that it occurs in a belt 

half a mile wide north of the junction of Killarney and Gold Basin 

Creeks. The Survey field party panned a cassiterite pebble from a 

prospect dump near this stream intersection. Opinions differ on the 

eastward extension of the tin belt. One may says that there is no 

cassiterite east of l{illarney Creek. Another says it has been found 

as far east as half a mile beyond the largest of the small lakes east 

of Killarney Creek but that 2 miles of drilling farther eastward 

toward Utah Creek showed no cassiterite. Others say that it is found 

for 3 miles east of Killarney Creek or nearly to Utah Creek and that 

in this area the concentrate is finer grained, more disseminated, and 

without much gold; any gold is light and fine. 

An east-west line of drill holes reportedly showed the bedrock altitudes to be about equal between Gold Basin and Killarney Creeks 

in the area of proved cassiterite occurrence. Farther east bedrock 

altitudes drop. The depth of burial of the bedrock on Gold Basin 

and Killarney Creeks ranges from 40 to 80 feet, varying more with 

surface topography than bedrock topography; at Utah Creek bedrock is about 100 feet below the surface. 

Compared with the placers in the Patterson Creek drainage basin, 

the placers of Baker Creek, more particularly those west of Killarney 

Creek, yield cassiterite mostly in finer sizes. The coarsest piece 

found by drilling was an inch in diameter. Some drill holes showed 

as much cassiterite as many of the drill holes in the producing areas 

to the west, but indications are that the average amount of cassiterite 

per unit area is less. Furthermore, the accompanying gold is very 

fine and was not sufficiently plentiful to be mined profitably under 

1941 economic conditions. 

A divide between Gold Basin Creek and Cache Creek has a minimum altitude of about 930 feet. This divide is about 500 feet higher 

than surface altitudes at the Woodchopper Creek placers, 200 feet 

higher than surface altitudes on Cache Creek 1 mile west, and 120 

feet higher than Gold Basin Creek. It overlies a bedrock divide 

indicated by prospecting to be about 900 feet above sea. level, or 145 

feet above bedrock in Gold Basin where the principal trail crosses 

the creek, and 220 feet above bedrock in the principal Cache Creek 

workings. Evidently, no bedrock stream channel connects Gold 

Basin and Cache Creeks in the line of the tin belt at the level of 

the principal placer deposits. Cassiterite on this divide has not been 

reported by the prospectors. The depth of burial ranges from 28 to 

65 feet, averaging about 40 feet. 
396 MINERAL RESOURCES OF ALASKA 

CASSITERITE OUTSIDE THE TOFTY TIN BELT 

Outside of the Tofty tin belt the closest placers where cassiterite 

is relatively abundant are those of Morelock Creek on the north side 

of the Yukon River, 16 to 20 miles north of the Woodchopper Creek 

workings. Cassiterite is a minor constituent in placer concentrates 

from Hunter and Troublesome Creeks north of Wolverine Mountain 

in the Rampart area and about 34 miles northeast of Killarney Creek 

(Waters, 1934, p. 232, 235-6). There the cassiterite occurs as darkamber to golden-yellow or nearly colorless crystals, or as wood tin, 

in either form unlike the Tofty cassiterite. In the Eureka Creek 

area east-northeast of the Tofty tin belt and in line with it geographically and structurally, cassiterite has not previously been reported. However, according to A. H. Rieder, a few pebbles of cassiterite were found by Johnson and Johnson on Glen Creek 14 miles 

from Killarney Creek in 1939, and appear to be the same as the 

Tofty cassiterite. In 1941 Samuel L. Cotten, engineer for the Cleary 

Hill Mines Co., showed the writer a small pebble of cassiterite 

panned from the area then being prepared for sluicing at the junction of Eureka and Pioneer Creek 15 miles east-northeast of Killarney Creek. The cassiterite pebble is dense, is well rounded, and 

includes dark breccia fragments, like much of the cassiterite at 

Tofty. It is possible that these few pebbles were planted by pranksters, but the writer is inclined to agree with the finders that the occurrences are genuine. 

Mining and prospecting on the streams a few miles north and south 

of the Tofty tin belt have thus far failed to show cassiterite of the 

Tofty type. A few small angular clear-brown grains of cassiterite 

were reported by Waters ( 1934, p. 240) from the bottom of a prospect pit on the Quartz Creek bench 2 miles north of the Sullivan 

Bench pit. This area was drilled and prospected extensively in about 

1940 by the Cleary Hill Mines Co., but cassiterite was not mentioned in the logs of 185 drill holes. The gold in the basin of upper 

Sullivan and Quartz Creeks, which was developed by this drilling 

program, has a greenish cast and is more angular than most of the 

gold in the tin belt 2 to 3 miles to the south. The depth of burial 

between streams in the area is only 5 to 10 feet; most of the overburden is creep and wash material. 

In the Boulder Creek drainage basin which parallels the tin belt 

6 or 7 miles to the north and rises on Roughtop Mountain, no cassiterite was found in the concentrates from the several placer operations conducted there in the past 30 years. American Creek, south 

of lower Boulder Creek and about 6 miles northwest of the Woodchopper Creek workings, also shows no cassiterite. It has been extensively dredged for gold since 1917. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 397 

South of the tin belt most of the bedrock is so deeply buried by 

Quaternary alluvium that it has received only a fraction of the 

testing that was given areas to the north. No placer concentrates 

were available in 1941 to the Survey for study from deposits on 

bedrock of lower Sullivan, Cache, and Patterson Creeks or from Big 

Denver (Rock) and Little Denver Creeks. Together these streams 

drain the area from 1 to 6 miles south of the tin belt (pl. 40), in· 

eluding the northwest slope of Hot Springs Dome. Sands from the 

present streambeds evidently contain no cassiterite. Prospectors who 

reached bedrock in this area have never reported finding cassiterite, 

according to the 1941 inhabitants of the Tofty and Hot Springs dis:-

tricts. Nevertheless this mineral could possibly occur here. The 

same statements apply to Blowback Creek which drains northward 

from Hot Springs Dome into Baker Creek. 

In the 2-mile-wide belt occupied largely by shallow muck and 

creep material, immediately north of the tin belt, there has been much 

prospecting for the lode source or sources of the cassiterite and gold. 

In the early days of the district, Eakin (1913, p. 37-8, and 1915, 

p. 93-4) repeatedly stated that the source of the cassiterite was veins 

and dikes in the immediate area of the placers. He directed the 

attention of the miners and prospectors to the bedrock in the neighboring hills and to that exposed in the mines rather than to the 

Roughtop Mountain area which was then receiving much attention. 

Mertie (1934, p. 207-9, 216-17) also directed attention to the neighboring area, but added that the quartz-cassiterite veins in this belt 

may have been removed by erosion, leaving the heavy cassiterite 

behind as residual deposits. Thus encouraged, many men have spent 

much of their time and resources prospecting this area since the 

early days of the district. 

The negative results thus far (1941) attest either to the effectiveness of muck and creep material in concealing the character of the 

bedrock, to the correctness of Me.rtie's hypothesis that cassiterite lodes 

no longer exist, or to the incorrectness of the general theory. For 

most of the work done on the hillside area, neither actual records. 

nor first-hand recollection are available. The best existing records 

are those of Adolph Bock which relate to the drilling of about 20(} 

unsurveyed holes in the upper Innesvale Gulch area, 84 drill holes 

of which are briefly summarized in table 2. In the summer of 1941,. 

a few drill holes were sunk in the upper Hokeley Gulch area and 

on the west side of Tofty Gulch by Cessford, Albrey, and Amalon. 

From time to time prospect shafts have been sunk in upper IdahoGulch by Jack Donahue and in the Cache Creek area by Otto Hovley, but almost all reported observations of bedrock showed only the 
398 MINERAL RESOURCES OF ALASKA 

common dark phyllite or sporadic graywacke, sandstone, quartzite, 

and rarely a barren quartz stringer. 

Exceptions to this generalization are seen in small mafic intrusive 

bodies uncovered by Donahue in upper Idaho Gulch and by Patrick 

McLaughlin on the ridge between Harter Gulch and Sullivan Creek 

(fig. 48). The Idaho Gulch intrusive body appears from the limited 

exposure to be a very small plug with a serpentinized diorite or 

gabbro core and a finer grained shell, but the Harter outcrop is dikelike in shape and is conformable with the country rock. McLaughlin 

also exposed a crystalline limestone bed a hundred yards south of the 

metadiorite, containing magnetite and hematite. The writer found 

a metadiorite dike along the west side of Woodchopper Creek valley, 

20 feet wide, exposed for 150 feet, and apparently conformable with 

the bedding. But mafic rocks, although they may be the source of 

the chromite, picotite, ilmenite, magnetite, and several other minerals 

in the placer concentrates, are not known sources of cassiterite. However, they show limited igneous intrusion in the belt just north of 

the placers and strengthen the possibility that complementary acidic 

dikes, perhaps containing tourmaline, and quartz-tourmaline veins, 

will also ultimately be found. 

As an estimate, it may be said that despite 30 years of prospecting 

and the evidence obtained from outcrops, shafts, and drill holes, 

probably less than 1 in 300 square feet of bedrock of this 2-mile-wide 

tin belt had been seen or tested by 1941. It is true that much of the 

covered area near outcrops and test holes may be excluded by inference, but a very large, unknown area still exists that could contain 

narrow dikes, veins, or beds of cassiterite-bearing rocks. 

ORIGIN OF THE CASSITERITE 

Although one hypothesis of the origin of the cassiterite is preierred, two must be considered until the discovery of conclusive evidence such as a bedrock source of the ore. 

The hypotheses briefly are: 

1. A Tertiary stream brought the cassiterite into the area of the tin 

belt :from an outside source. 

2. A primary bedrock source exists, or :formerly existed, in the line 

of the tin belt or within a mile or more north of the belt. 

According to the first hypothesis, a major Tertiary stream flowing 

above the 900-:foot altitude of the present Cache Creek-Gold Basin 

Creek divide brought the cassiterite-bearing gravels and some gold 

into the line of the tin belt. This master stream subsequently 

-changed its course or was captured during the lowering of regional 

base level in late Tertiary time. Headwater tributaries of the then 

entrenching Patterson and Baker Creeks cut back into bedrock in the 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 399 

belt of the main placer deposit and redistributed the cassiterite and 

gold into placers related to their own courses and nearly at right 

angles to the older major placer belt. This process of redistribution 

was interrupted in early Quaternary time by a raising of regional 

base level and by heavy aggradation of glaciofluviatile deposits from 

the Alaska Range, resulting in burial of the placers. The area of 

quartz-tourmaline-cassiterite veins from which the major Tertiary 

stream derived the cassiterite is generally assumed under this theory 

to have been Hot Springs Dome or an unexposed granite body nearer 

the tin belt. The monzonite intrusive rocks of Roughtop Mountain 

are not as acidic as those generally associated with tin mineralization 

and they furthermore lack the abundant tourmaline of the ores and 

of the Hot Springs Dome intrusive rocks. 

This hypothesis accounts for the almost universal rounding and· 

polishing of the cassiterite pebbles with no notable increase in angularity upstream in individual gulches; for tourmaline dike rocks, 

granite, monazite, aeschynite, and large zircons among the gravels 

a.nd sands; and in general for placer deposits along what was perhaps 

the course of a major stream in Tertiary time, which can be inferred 

from the lineation of bedrock valleys west of the Tolovana River 

region. 

The weaknesses of the hypothesis are several. The most significant is the failure to find cassiterite of the Tofty type outside the 

tin belt, with the rare exception of a few pebbles in the Eureka area. 

Hot Springs Dome has much tourmaline and quartz but thus far 

cassiterite has not been found in either its outcrops or its drainage 

area. The length and narrowness of the tin-belt area and the sharpness of the upstream tin cutoff cannot easily be explained under the 

hypothesis of a major Tertiary stream, which would not normally 

be expected to confine itself for such a distance to such a narrow, 

comparatively straight channel throughout the entire period of its 

cassiterite deposition. The presence of larger amounts of low-grade, 

less dense, cassiterite-bearing pebbles in the gravels of the creeks at 

the west end of the tin belt has been cited as evidence of major 

stream deposition from east to west, but the pebbles are as easily 

accounted for by variation in mineral deposition under the other 

hypothesis. There is no increase in angularity of cassiterite pebbles 

toward a supposed remote source; the cassiterite of Gold Basin and 

Killarney Creek is fully as rounded as the cassiterite of W oodchopper Creek. A few subangular tourmalinized phyllite fragments with 

quartz-tourmaline-cassiterite veinlets in the placer gravels are also 

not explained. 

Another difficulty with the hypothesis is that of stream grade. To 

move coarse cassiterite pebbles and coarse gold for 5, 10, or perhaps 
400 MINERAL RIBSOURCES OF ALASKA 

15 miles downstream requires either a very large stream with a moderate grade or a fairly large stream with a steep grade. A detailed 

geomorphic study of Tertiary drainage may possibly show that such 

a stream might have flowed over the site of the tin belt, but a combination of such conditions seems unnecessary in explaining the general Tertiary drainage. A confined major stream large enough or 

steep enough to erode a cassiterite deposit and transport it for miles 

might be expected to have left other evidence in the region such as 

prominent high-altitude terraces and scattered, thick boulder and 

gravel deposits of rounded resistant rock types such as quartzite. 

The known gravel and boulder deposits of rounded, resistant rock 

types are comparatively limited and local in distribution and derivation, with the possible exception of rare igneous types. Such gravels 

may exist, however, in the lower Patterson and Baker Creek valleys, 

having been swept there by later Tertiary runoff related to the present stream pattern. 

According to the second hypothesis, certain quartz veins in the area 

of the tin belt or in a narrow belt immediately north of the tin belt 

were brecciated not long after their emplacement in Tertiary time. 

The openings thus created were filled during a brief intense period by 

tourmaline with cassiterite, more quartz, and a small amount of 

fluorite emanating from an unexposed granitic magma of the Hot 

Springs Dome type formed somewhere under the tin belt. Minor 

tourmalinization of the intruded phyllite and other sedimentary 

units of the Lower Cretaceous country rock occurred near the brecciated quartz veins, accompanied by some filling and replacement of 

these altered rooks with cassiterite, tourmaline, and quartz. However, such mineralization was not extensive. 

Later in Tertiary time, after a lowering of the regional base level 

of erosion, the several thousand feet of Cretaceous sedimentary rocks 

above the present bedrock surface were slowly eroded by streams of 

various sizes but of moderately low gradient. The cassiterite had 

originally been deposited largely in the upper parts of the quartz 

veins which were eroded away during this period. Most of the 

Cretaceous country rock disintegrated comparatively rapidly under 

conditions of weathering and erosion. Very little of the phyllite 

and softer graywacke resisted weathering and abrasion long enough 

to become rounded, so that at any given time the existing gravels of 

such material, whether rounded or not, were comparatively recently 

exposed and could be expected to break down quickly to sand and 

silt sizes and to be carried away in suspension in the Tertiary 

streams. On the other hand, some of the more indurated sandstones, quartzites, and vein quartz, and especially the cassiterite, 

resisted disintegration. Under the relatively low stream gradients, 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 401 

fragments of such material remained intact and moved only comparatively short distances from the sites of their host veins, some 

of the cassiterite pieces gradually moving down with the eroding 

surface for as great a distance as they were moved laterally by 

streams. Although they moved such short distances, the cassiterite 

pebbles and a few of the other boulders, gravels, and pebbles were 

rounded and polished by abrading action of lighter weight, detrital 

material under the influence of creep, sheet wash, and stream action. 

Gold from the quartz veins of the belt, not necessarily the same 

veins as those containing cassiterite, underwent the same treatment 

and also remained behind in residual deposits. Stream action during the Tertiary period concentrated the gold and cassiterite into 

several placer deposits of different sizes. Fluctuations in regional 

base level and other changing local conditions caused several periodic changes in the rate of erosion, resulting sometimes in aggradation for a period and in changes of stream course. Thus, a 

concentration of cassiterite, gold, and gravels could be abandoned 

temporarily by its parent stream which might then cut another 

channel nearby leaving the placer on a minor bench, later to be reconcentrated as the lateral drainage into the new stream course cut 

back into the older placer area. 

By early Quaternary time the topography of the region corresponded to the present bedrock topography of the region. The cassiterite-bearing parts of the quartz veins had been largely eroded 

away, leaving the cassiterite behind, whereas almost all other rocks 

except those recently exposed were disintegrated and carried from 

the region by the streams. At this time the regional base level was 

raised, with some fluctuation, and the glacio:B.uviatile silts were deposited, burying all the valleys and the low hills including the 

slopes of those north of the tin belt. Owing to the subsequent lowering of base level, the hillside areas have been freed of much of 

their Quaternary silt cover but are masked with weathering detritus 

and creep material several feet thick that impinge upon the edges 

of the remaining Quaternary silt deposit. 

The greatest difficulty with this theory is that cassiterite-bearing 

quartz-tourmaline veins, or their roots, have not yet been recognized 

in or just north of the tin belt. It has also been argued that the 

cassiterite pebbles are too rounded and polished to be residual and 

that there is an absence of the fine cassiterite that is generally found 

in a residual deposit. Another stated objection is that the cassiterite pebbles are larger, lighter, and lower grade at the west end of 

the belt, indicating sorting from east to west. 

The first objection, that the veins have not yet been found, has at 

present two answers, both previously discussed : first, that only 
402 MINERAL RESOURCES OF ALASKA 

about 1 in 300 square feet of the hillside belt has been seen by man 

or tested by drilling, and second, that the cassiterite-bearing parts 

of the quartz vein system have been eroded away, leaving the residual cassiterite, whereas the quartz veins and lenses now exposed 

were formed at greater depths and are not necessarily representative of the particular group or belt of veins that were brecciated,. 

and then filled by the cassiterite and associated minerals. Strongly 

supporting evidence for the existence of such veins, even in the 

present bedrock area, is the small amount of angular cassiteritequartz-tourmaline fragments in the gravels and concentrates, and 

the rare angular pieces of tourmalinized, cassiterite-bearing country 

rock. The argument that the pebbles are too rounded to be residual 

is answered by the previous explanation, and by the realization that 

the Tofty cassiterite pebbles are at least 2.7 times as heavy in water 

as the country rock fragments. A headwater stream of small volume and relatively low gradient could round them and leave them 

behind more readily than it could move them. The widespread belief that there is an absence of fine cassiterite probably results from 

the failure of prevailing sluicing methods to recover much of the 

cassiterite. The Survey sampling found small amounts even in the 

coarse tailings on every creek in the district, and samples of much 

of the rest of the fine cassiterite that was mined and lost may be 

panned short distances down the drains from the lower end of sluice 

boxes. 

That the density of the cassiterite is less on the western creeks is 

true; otherwise the cassiterite concentrate recovered by Survey sampling from Woodchopper Creek tailings was nearly the same as that 

from Cache Creek. From Idaho Gulch to Deep Creek the gravels 

contain more than the usual amounts of pebbles from the tourmaline 

end of the tourmaline-cassiterite scale. Most of these are too light 

to be caught in the rifHes, but a few are intermediate in density, 

and their inclusion in the cassiterite concentrates handpicked from 

the rifHes by the miners lowers the grade. However, as such hybrid 

pebbles are uncommon in the tailings of Woodchopper Creek, the 

westernmost creek of the belt, variations in the regional distribution of tourmaline-rich cassiterite-bearing pebbles are perhaps better explained by differences in local sources than by east-to-west 

sorting by a master stream. 

Additional factors supporting the second hypothesis are the sharp 

upstream cutoff of the deposits on individual creeks and the discovery of altered intermediate and mafic igneous intrusive rocks in 

the bedrock area north of the placers. The intrusive rocks, although 

of types not directly associated with cassiterite deposits, nevertheless indicate igneous activity and strengthen the possibility that 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 403 

small acidic igneous dike rocks, notably tourmalite, may later be 

found. 

The granite cobbles and the monazite, aeschynite, apatite, and zircon can be accounted for under either hypothesis. Quartz veins, 

pyrite, and the rare arsenopyrite and galena cannot be shown to be 

restricted to the tin belt. 

RECOVERY OF THE CASSITERITE 

Factors governing the recovery of cassiterite in the tin belt are 

the richness of the gravels being mined, the physical properties of 

the cassiterite, and particularly the sluicing method (pl. 43.A). Concerning the richness of the gravels, the foregoing discussions of the 

nature and history of the individual placers need only be summarized. The tin belt yielded about 315 tons of cassiterite concentrates 

through 1941 as a byproduct to the recovery of several million dollars in gold. The richest placers were discovered and worked out 

before 1919, yielding a total recovery of about 262 tons of cassiterite 

concentrates, much of which came from reworking tailings (pl. 

43B). Only scattered records are available to indicate the richness 

of the placer gravels. In 1918 one rich pay streak on lower Woodchopper Creek yielded 1.2 pounds of cassiterite per square foot of 

bedrock or assuming that 6 feet of gravel was removed, about 5.4 

pounds per cubic yard of mined gravel. Small pay streaks of 

bonanza richness in cassiterite are said to have yielded as much as 

8 pounds per square foot or 36 pounds per cubic yard, and it is 

reported that a tiny area yielded 70 pounds of recovered cassiterite 

per cubic yard of gravel. The average yield from the rich pay 

streaks found in the early days of the district, where an effort was 

made to save the cassiterite, was probably more nearly 0.5 pound 

per square foot or 2.3 pounds per cubic yard. Corresponding 

bonanza gold values were $10 to $40 per square foot at the price of 

gold then prevailing, and many of the richer placers reportedly 

averaged $4 to $6 per foot over large areas. Since 1919 more complete records indicate a total cassiterite recovery of 53 tons, mostly 

from original operations rather than from reworking of tailings. 

The drift mines of the district recovered during this period an average of about 0.3 pound per square foot of bedrock mined or about 

1.4 pounds per cubic yard, but the large open-pit operations on 

Tofty Gulch and the bench of Sullivan Creek have recovered only 

0.02 pound per square foot from ground previously drift mined. 

The foregoing figures are based on the amount of cassiterite actually recovered from the placer gravels and do not account for the 

loss of cassiterite in sluicing operations. Records from which to 

compute the total cassiterite content of the individual pay streaks 
404 MINERAL RESOURCES OF ALASKA 

are almost entirely lacking. Rough calculations on combined statistics from drift mines in the last 20 years and on sampling results 

of the tailings indicate an average recovery of about 57 percent, 

including recovery from tailings. The only specific tests on percentage recovery were done by the Cleary Hill Mines Co. during the 

sluicing operations in the Sullivan pit from July 19 to August 9, 

1941, with the following results: 

Test 1 Test2 Combined 

Gravels sluiced, cubic yards _______________ 9,000 4,840 13,840 

Cassiterite in gravels, pounds per cubic yard_ .81 .85 .82 

Cassiterite in gravels, total content in tons __ 3.64 2.07 5.71 

Cassiterite recovered, pounds per cubic yard_ .27 .26 .27 

Cassiterite recovered, total in tons __________ 1.22 .63 1.85 

Gravel tailings, cubic yards _______________ 4, 100 2,900 7,000 

Cassiterite in tailings, pounds per cubic yard_ 1.18 .99 1.10 

Cassiterite in tailings, total content in tons __ 2.42 1.44 3.86 Recovery, percent_ _______________________ 33.5 30.4 32.3 

Test 1 was made largely on old tailings that were left on the 

original surface from drift mining and were washed down during 

strip mining. Because the cassiterite content of the gravels treated 

during these tests was higher than the average found in the open-pit 

operations, an extraordinary effort was made to save it. The cross 

riffies were hand picked for cassiterite twice daily, which accounted 

for two-thirds of the cassiterite actually saved. Thus, it may be 

noted that the percentage recovery by methods ordinarily used in 

this pit would have been much lower, or perhaps 10 percent. In 

these tests, the tails were tested frequently by panning as they 

formed, and the cassiterite content of the heads was computed with 

due consideration of the recovered cassiterite and the sliming ratio. 

The volumes of the heads and tailings were estimated by Mr. H. H. 

Thurston, manager. As the cut was 56,000 square feet in area, the 

indicated cassiterite content of the heads per square foot was 0.203 

pound and the recovered cassiterite 0.066 pound. 

The Cleary Hill Mines Co. tests show not only that two-thirds 

of the cassiterite was lost under comparatively favorable conditions 

for this type of operation but also that the tenor of the tailings is 

higher than that of the original gravels. This is explained by the 

high sliming ratio of the virgin gravels, perhaps 45 to 60 percent 

as mined in the Sullivan Bench pit. It also seems that the content 

of cassiterite in tailings from operations with 50 percent slimes may 

be a fair index of the tenor of cassiterite in the gravels being sluiced. 

Normally the operations in the tin belt area were designed to 

recover gold. Where cassiterite could also be saved by using exist-
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 405 

ing equipment without loss of gold and without increasing costs 

prohibitively, an effort was made to increase its recovery. In many 

operations no cassiterite was saved during sluicing, but many of the 

tailings piles so deposited have since been reworked for cassiterite 

and gold by resluicing the drop areas around the ends of the original 

sluice boxes (pl. 43B). Only rarely has cassiterite been actively 

sought primarily in the original operation. Such instances occured chiefly during the First World War. The most notable example was the double sluicing on Woodchopper Creek by Howell 

and Cleveland at which time the district produced more than 100 

tons. The price of tin at that time more than made up for the 

increased labor costs of the frequent cleanups of a double-sluicing 

system. 

A common practice in the tin belt in 1941 and earlier was to give 

sluice boxes :from 10- to 12.5-percent slopes and to use mostly longitudinal riflles. This was necessary to break :frozen clumps of sandy 

and silty gravel, :free the gold, and carry away most of the coarser 

cobbles that would otherwise have to be removed by hand from the 

boxes. Gravels were sluiced :for 3 or 4 weeks between cleanups, and 

the riflles were quickly packed with angular and rounded gravels 

and cassiterite after a cleanup. The result is that although gold 

recoveries were :fairly satisfactory to the operators, the rounded pebbles of cassiterite were rolled over the top of the packed riflles by 

swift sluicing currents 4 to 7 inches deep. Where cross riffies were 

used, the amount of cassiterite saved in a cleanup increased. On 

longitudinal riffies, cassiterite has been observed to accumulate :for 

a time during sluicing periods and then slide down and out of the 

boxes as a mass, sometimes carrying a :few gold nuggets with it. 

The cleanup in the Tofty Gulch pit on June 18, 1941, by the 

Cleary Hill Mines Co. will serve as an example of larger scale 

sluicing practice and riffie arrangement in the district. The cleanup 

terminated 25 days and nights of sluicing and bulldozing of a bedrock area of 70,000 square feet, 23 feet deep including 17 feet of 

muck, 3 feet of gravel, and 3 feet of bedrock. Nine metal sluice 

boxes, each 10 feet long, had been in place in a steep trench excavated in bedrock during the sluicing period. The lower end was 

10 feet below normal bedrock level and beyond it was a sump 4 feet 

lower. The drop from head to foot of the sluice was about 10 feet, 

or 11 percent. The first 30 feet had 12-pound steel rails placed 

lengthwise, alternate rails being upside down; the next 10 feet had 

26 thick rubber cross riflles made of old tire casings; the next 20 

feet had more longitudinal steel rails, after which there were 15 

feet of more rubber cross riffies and 5 feet of steel-rail cross riflles. 

The last 10 feet of the sluice had a cocoa-matting undercurrent 
406 MINERAL RESOURCES OF ALASKA 

arrangement protected by a sheet screen with hal£-inch holes. The 

riffles were all tightly packed, mostly with angular phyllite fragments of sand to gravel sizes but with conspicuous cassiterite pebbles. Of the total tin recovered in the cleanup, 37 percent was in 

the upper 55 feet of the boxes and 63 percent was in the lower 35 

feet including the undercurrent. The gold was about 4.6 percent in 

nugget size and most was caught in the upper longitudinal riffles. 

Equally steep grades but shorter sluice lengths, ranging from 

about 40 to 60 feet, were used in several sluicing operations observed 

at drift mines operating in 1941 (pl. 43A.). Longitudinal pole riffies 

were common, and any cross-pole or steel-rail riffies used were generally put in the lower end of the sluice boxes where the grade 

might also be somewhat decreased. The depth and swiftness of 

sluicing current were less than in larger scale sluicing practice. 

Most operators agreed that recoveries could be doubled by the 

more extended use of cross riffies, longer sluices, lower grades, much 

more frequent cleanups, and particularly by handpicking the cross 

riffles for cassiterite every few hours during interruptions in sluicing. The reasons why these things were not done were largely economic, partly operational. Under normal conditions many operators 

doubted that the added income from tin would offset the cost of the 

increased necessary labor. There was some fear of the high-grading 

of gold nuggets by the tin pickers. Longer, flatter sluices with 

slower currents would mean more frequently clogged sluices and 

much more work for a sluice attendant. The same type of reasoning 

was applied to duplicate sluicing, which requires extra equipment 

and much cleanup labor. 

Cassiterite concentrates were normally shipped in 125-pound canvas sacks to Seattle for reshipment to Singapore. Approximate 

measurements and determinations of density made on cassiterite concentrates from the Sullivan Bench and Tofty Gulch pits in 1941 by 

the Survey gave the following results : 

Size range, in inches Percent Density, including foreign voids 

particles Material (pyrite and 

other min- Pounds per Specific Maximum Minimum Average erals, and cubic foot gravity metal scrap) 

Shipping concentrate __ 2. 00 0. 05 0. 50 5 225 3. 60 ])o ______________ 2. 00 . 05 . 50 2 230 3. 68 

Hand-picked coarse concentrates _______ 2. 00 . 50 1. 30 0 222 3. 55 

Hand-jigged black sands ______________ . 20 . 06 . 10 15 255 4. 08 ])o ______________ . 20 . 06 . 10 20 247 3. 95 
GEOLOGICAL SURVEY BULLETIN 1058 PLATE 42 

Aerial photograph of Tofty tin-belt workings in 1941, light areas from Woodchopper Creek on the lower 

left to Sullivan Rench on the right center. Yukon River in the background. (Courtesy U.S. Air Force.) 
GEOLOGICAL SURVEY BULLETIN 1 0 58 PLATE 4 3 

A. Sluicing on Deep Creek, 1941. Surface plant of Hanson and Albrecht on the Marietta claim; 

the boiler and pumphouse are behind the low shaft headframe . The elevated flume carries 

returned water to the head of the sluice where the bucket is about to dump against shear 

boards at the automatic tipple. Typical tailings in the foreground. 

B. Reworking a Deep Creek tailings p ile, 1941. Tailings near the center or drop area of this old 

pile on the Marietta claim are being resluiced. Hot Springs Dome is in the background. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 407 

The above figures indicate cassiterite in the black sand sizes is 

more nearly pure than cassiterite in the gravel sizes. The regular 

shipping concentrate, though it contains fewer impurities such as 

pyrite and metal scrap and is apparently comparable in percentage 

of voids to the black sands, is nevertheless of lower density and 

therefore lower tin content. The impurities in the coarse pebbles 

are dominantly quartz and tourmaline. 

A true specific gravity determination, excluding voids, of 24 

pounds of hand-picked coarse cassiterite pebbles from the Sullivan 

pit gave a value of 5.8 compared to 6.8 to 7.1 for pure cassiterite, 

indicating that the coarse pebbles are about 70 percent cassiterite. 

A common practice is to amalgamate the gold in the few tens or 

hundreds of pounds of black sands accumulated in a season at a 

given property and then to throw the sand away. Such sand is 

amenable to treatment in a simple Joplin jig, as shown in experiments by the writer. The jig used was a simple, screen-bottomed 

can placed in a barrel of water and operated by hand in a jigging 

motion. An 8-pound sample screened to the size range between l;16 

and %6 inches was originally 41 percent cassiterite grains, the rest 

pyrite and gravel. In 45 minutes of hand-jigging, including the 

retreatment of middlings and tailings, a concentrate 84 percent cassiterite weighing 3.5 pounds was obtained, representing an almost 

!lO nercent recovery and a grade suitable for shipment. 

SAMPLING OF TAILINGS 

The tin belt was studied in 1941 primarily to find a basis for estimating the reserves of cassiterite in view of the war-time need for 

tin from domestic sources. As the tailings from former operations 

represented a sizable reserve of the most immediate availability in 

the district, and as a systematic study of their cassiterite content 

presented one approach to the problem of the buried placers, the 

writer chose to adopt a sampling system suitable for use on all tailings in the district. It was necessary to process a large volume of 

tailings because of their coarseness and the coarseness of the cassiterite. The apparatus had to be portable and inexpensive and the 

sampling crew small because of fund and transportation limitations. 

A rocker seemed to be the answer, and after some study of the tailings and of a few rockers used in the district in prospector's cleanups, the writer modified a standard Malay design and had one made 

in Fairbanks. This rocker was in everyday use from July 11 through 

September 19, 1941, ordinarily with a crew of three men. It gave 

excellent recoveries of both cassiterite and gold down to fine sizes. 

Fifty-nine separate sample cleanups were made, ranging from 3 each 
408 MINERAL RESOURCES OF ALASKA 

in Dalton and Idaho Gulches to 13 on Deep Creek and 10 In the 

Sullivan Bench pit. 

A summary of the results is given in table 3, in which a liberal 

tenor of 65 percent tin is assigned to the cassiterite concentrate and 

the tin value is assumed to be $0.52 per pound. The gold is assumed 

to be 800 fine or $28 per ounce for these calculations. The ratio of 

the total volume of the samples to the estimated volume of all tailings in the district is about 1 in 10,000. The sampling results cannot be presented in greater detail without revealing the holdings of 

individual owners. 

TABLE 3.-Cassiterite and gold in tailings from the Tofty tin belt 

Woodchopper Miller Gulch Sullivan Bench Total (average and to to or range) 

Deep Creeks Tofty Gulch Ferguson Draw 

Estimated total tailings, cubic yards _____ 

Volume of sample, 

105, 600 131,200 186,700 423,500 

cubic feet ___________ 249 357 554 1, 160 

Indicated total cas- siterite, tons _________ 

Cassiterite, pounds per 

cubic yard: 

84.7 78.7 58.9 222.3 

Alverage ___________ 1.60 1.20 0.63 1.05 Range ____________ o.o-4.3 0.2-3.8 0.0-4.7 o.o-4.7 

Gold, grains per cubic 

yard: Alverage ___________ 10.55 3.62 2.55 4.88 Range ____________ 0.8-34.9 O.D-13.0 0.3-25.2 O.D-34.9 

Value of tailings, dolIars per cubic yard: Cassiterite _________ 0.54 0.41 0.21 0.35 Gold ______________ .62 .21 .15 .28 

TotaL __________ 1.16 0.62 0.36 0.63 

In sampling sluiced tailings, numerous small pits 3 to 5 inches 

deep were dug and half a shovel full of gravel was taken from the 

bottom of each pit. The spacing of the individual sample pits 

ranged from 5 to 20 feet, being closer where the underlying gravels 

were thicker. The entire surface of a tailings pile would be thus 

sampled, and if it was a moderately large pile a rocker cleanup 

would then be made giving a composite sample of the tailings pile. 

For smaller tailings piles, several might be surface sampled before 

a cleanup was made. Pipe samples or auger samples were not used 

because of the coarseness of the gravels and the numerous boulders. 

Shafts and trenches were not used in sluiced tailings because they 

are costly, time consuming, and too concentrated in sample location. 

A shaft located accidentally in the middle of a drop would give very 

high, unrealistic results. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 409 

In the Sullivan Bench pit the tailings had mostly been restacked 

by bulldozers and were therefore sampled by larger, deeper pits dug 

at greater intervals. In the Tofty Gulch pit the tailings had been 

stacked into cones by a dragline and could be sampled by deep pits 

dug at the apex of each pile. The sampling methods used are open 

to criticism but were considered to give reliable average figures 

representative of tailings in large areas of the district. 

As a check on the structure of sluiced piles and on the applicability of surface sampling to the older sluiced tailings, vertical samples were taken by the Survey on a pile on upper Cache Creek. This 

pile of Howell's had been thoroughly reworked for cassiterite and 

gold about 1915 by Ed Erickson, who according to Otto Hovley 

recovered 200 pounds of cassiterite and 20 ounces of gold from a 

cut which by 1941 estimate contained about 370 cubic yards of 

gravel; this represented about 0.54 pound of cassiterite and $1.51 in 

gold per cubic yard at the 1941 prices. Sampling of the surface of 

the rest of the pile by the Survey indicated cassiterite and gold contents of only 0.19 pound and $0.28 respectively per cubic yard remaining in the less-rich parts of the pile. Along the edge of the 

reworked cut the Survey dug 2 vertical pits for the thickness of the 

pile and took samples of 1f2 cubic foot every 6 inches. A similar test 

pit was dug by the Survey at a suitable place on another tailings 

pile. The results of these tests are shown in table 4. 

TABLE 4.-Vertical samples through Cache Creek tailings 

[Pounds of cassiterite per cubic yard and dollars in gold per cubic yard] 

Test pit A 

Depth below the surface of the tailings pile J-----.----J 

(feet) Cassiterite Gold 

Test pit B, 1 gold 

o.o-o.5_______________________ o. 69 $0. 01 $0. 01 

0.5-1.0_______________________ . 60 . 04 . 01 

1.0-1.5_______________________ 1. 38 • 12 0 

1.5-2.0_______________________ . 05 . 03 • 01 

2'.0-2.5_______________________ 0 2 4. 98 . 01 

2.5-3.0_______________________ • 08 . 23 0 

3.0-3.5_______________________ • 22 0 0 

3.5-4.0_______________________ . 16 0 0 

4.0-4.5_______________________ . 06 . 50 0 

4.5-5.0_______________________ 0 0 0 

5.0-5.5_______________________ 0 . 02 . 01 

5.5-6.0_______________________ . 22 0 0 

6.0-6.5_______________________ 0 0 0 

6.5-7.0_______________________ 0 0 0 

7.0-7.5_______________________ 0 0 0 

7.5-8.0_______________________ 0 0 . 01 

8.0-8.5 ______ ----------------- 0 0 0 

8.5-9.0 _______________________ -------- -------- --------

Average________________ . 204 

t No cassiterite found in test pit B. 2 Includes a small nugget. 

. 349 . 004 

Test pit C 

Cassiterite Gold 

0 $0. 02 

0 0 

0 0 

0 0 • 93 0 . 21 0 • 19 0 . 08 0 

0 0 

0 0 

0 0 

0 0 

0 0 . 12 0 

0 0 

0 0 

0 0 

0 0 

. 085 • 001 
410 M~ERAL RESOURCES OF ALASKA 

The average cassiterite and gold content shown by test pit A correspondents closely with that indicated by surface sampling. The 

position of this test pit apparently was about 15 feet from a drop 

that existed during the accumulation of the top 4.5 feet of tailings. 

On the other hand, test pit B was evidently not near a drop, as it 

shows no cassiterite and only a trace of fine gold. Test pit C, in 

another pile, was located near a drop that existed when tailings 2 to 

4 feet below the present surface were accumulating. 

The erratic distribution of cassiterite and gold vertically, as shown 

by the Cache Creek test pits, indicates that the location of cassiterite 

and gold within a sluiced tailings pile is determined chiefly by drops, 

that is, the position of the end of the sluice at the time of deposition of the tailings. It is recognized, however, that residual concentration of cassiterite pebbles at the surface of the piles is a factor that would result in the salting of surface samples if nothing 

had offset it. On most of the tailings piles in the district, but particularly on the richer piles of Miller Gulch and Deep Creek, pebbles 

of cassiterite exposed at the surface are easily found. Each year 

more are exposed by the washing away of lighter material around 

them. On the other hand, the tiny round pieces of cassiterite of 

buckshot to pea size are washed from the surface and settle into 

voids between the loose larger gravel fragments, offsetting naturally the concentration of larger pieces of cassiterite at the surface. 

It would therefore seem that surface sampling is reasonably safe 

from residual concentration, but the sampling crew had instructions 

to scrape the surface from each sample and throw the top shovelful 

away. 

In Tofty Gulch pit, tailings were sampled by a panner of the 

Cleary Hill Mines Co. for 6 consecutive days during sluicing in 1941. 

The total volume of samples was 84 pans or about 17 cubic feet. The 

lowest content of cassiterite shown by the tailings in any 1 day was 

0.36 pound per cubic yard. The highest was 4.26 pounds and the 

average was 1.92 pounds per cubic yard. These results are 75 percent higher than Survey figures for the entire pit, but the gravels 

sluiced during the 6 days in reference were considered by the manager to be richer than normal in cassiterite. 

In the Sullivan Bench pit a U.S. Bureau of Mines party under the 

direction of Mr. R. L. Thorne, working under adverse weather conditions in the winter of 1943, sampled the tailings by shafts, gopher 

holes, and channels.3 They determined the content of cassiterite to 

be 0.37 pound and gold $0.042 per cubic yard, less than % and lf2 

respectively, of Survey figures. However, their estimate of yardage 

3 Sullivan Creek tailings, Manley Hot Springs, Tofty, Alaska: U.S. Bur. Mines War 

Minerals Rept. 467, 1945. 
TOFTY TIN BELT, MANLEY HOT SPRINGS DISTRICT 411 

is much greater. The apparent discrepancy may be explained as resulting from the avoidance by the Survey party of sampling or including in tonnage estimates any material in the pit that could be 

distinguished as bedrock excavated for drains or sumps as opposed 

to bedrock sluiced for its included gold and cassiterite. The Survey 

party did not include for sampling about 150,000 tons of alluvium 

which covers much of the bedrock in the south end of the pit. Some 

of this alluvium consists of sluiced gravels and slimes from slueing, 

but most of it is barren muck and hillside ceep material washed 

into the lower end of the pit during hydraulic-stripping operations 

at the upper end. The Bureau of Mines data show that the inclusion of this alluvium would increase the Survey estimates of total 

cassiterite reserves in the Sullivan Bench tailings and would lower 

the average grade to about that shown by the Bureau of Mines. 

Results of sampling by the Survey and the Bureau of Mines in the 

cleaner, sluiced gravels in the north end of the pit checked very 

closely. 

CASSITERITE RESERVES 

The three categories of reserves in the tin-belt area are tailings, 

remaining placers, and lodes. The tailings reserves have now been 

roughly measured by the sampling described in the foregoing section. 

Excluding that in secondary alluvium in the lower end of the Sullivan Bench pit, they total about 222 tons of cassiterite, and about 

$118,000 in gold, distributed as shown in table 3. Any lode reserves 

must be dismissed as entirely speculative in 1941. The remaining 

buried placer reserves are estimated in the following paragraphs. 

In appraising remaining placer reserves it is necessary, in the 

absence of quantitative tin-sampling data, to use the grade of gravels 

found by mining in the district as a yardstick. For operations with 

high sliming ratios and with drains to carry away the slimes, it was 

noted that the tailings are a fair index to the grade of the gravels 

being sluiced. This suggests that the remaining Tofty Gulch and 

Sullivan Bench gravels range from 0.1 to 0.2 pound of cassiterite 

per square foot. These gravels of Sullivan Bench and Tofty Gulch 

had already been drift mined of their highgrade streak. The drift 

mines of the rest of the tin belt had recovered about 1.5 pounds of 

cassiterite per cubic yard on the average in recent years, including 

recovery by reworking of tailings, and their tailings still contain an 

average of 1.42 pounds of cassiterite per cubic yard. Assuming a 

20-percent sliming ratio for sluicing without a drain, as is customary 

at drift mines in the district, the average original gravel sluiced in 

recent years would contain 1.5 plus 80 percent of 1.42 or 2.64 pounds 

per cubic yard, .the approximate equivalent of about 0.59 pound of 

cassiterite per square foot. 
412 MINERAL RESOURCES OF ALASKA 

Considering the foregoing appraisal as well as available drilling 

records, it was estimated in 1941 that the proven and indicated reserves of buried placer cassiterite in areas with systematic drilling 

and in the immediate vicinity of mined pay streaks were about 900 

tons at 0.1 pound per square foot over an area of 18,000,000 square 

feet. Additional inferred reserves between creeks in the drainage 

basins of Patterson and Baker Creeks, and west of Woodchopper 

Creek, were estimated at about 1,100 tons at perhaps 0.05 pound of 

cassiterite per square foot. Recoverable tin-belt reserves would be a 

fraction of this total indicated or inferred reserve of 2,000 tons, depending upon mining and recovery methods and especially upon 

future econmnic conditions. 

As a byproduct to placer gold production and to reprocessing of 

tailings, limited cassiterite shipments were profitable through 1941, 

but the production of cassiterite in quantity as the primary product 

from virgin placers had not been the principal objective of any successful operation up to that time. Except for local concentrations, 

the cassiterite placer deposits were subeconomic because of their deep 

burial under frozen silts, their low grade and small reserves, their 

discontinuity, the poor water supply and tailings disposal gradient, 

and high cost of labor and freight. 

SELECTED REFERENCES 

Eakin, H. M., 1913, A geologic reconnaissance of a part of the Rampart quadrangle, Alaska: U.S. Geol. Survey Bull. 535, 38 p. 

--1915, Mining in the Manley Hot Springs district: U.S. Geol. Survey 

Bull. 622-G, p. 239-245. 

Mertie, J. B., Jr., 1934, Mineral deposits of the Rampart and Manley Hot 

Springs districts, Alaska: U.S. Geol. Survey Bull. 844-D, p. 163-246. 

--1937, The Yukon-Tanana region, Alaska: U.S. Geol. Survey Bull. 872, 

p. 156-172, 186-198, 219-226. 

Moxham, R. M., 1954, Reconnaissance for radioactive deposits in the Manley Hot 

Springs-Rampart district, east-central Alaska: U.S. Geol. Survey Circ. 317, 

6p. 

Taber, Stephen, 1943, Perennially frozen ground in Alaska, its origin and history: Geol. Soc. America Bull., v. 54, p. 1464-1548. 

Thomas, Bruce 1., 1957, Tin-bearing placer deposits near Tofty, Hot Springs district, central Alaska: U.S. Bur. Mines Rept. Inv. 5373, 56 p. 

Thorne, R. L., and Wright, W. S., 1948, Sampling methods and results at the Sullivan Creek tin placer deposits, Manley Hot Springs, Tofty, Alaska: U.S. 

Bur. Mines Rept. Inv. 4346, 8 p. 

Tuck, Ralph, 1940, Origin of the muck-silt deposits at Fairbanks, Alaska: 

Geol. Soc. America Bull., v. 51, no. 9, p. 1295-1310. 

Waters, A. E., Jr., 1934, Placer concentrates of the Rampart and Hot Springs 

districts, Alaska, in Mertie, J. B., Jr., Mineral deposits of the Rampart 

and Manley Hot Springs districts, Alaska: U.S. Geol. Survey Bull. 844-D, 

p. 227-246. 
INDEX 

Page Page 

Access to area._------------------------------ 365 Ferguson Draw, cassiterite deposits on ••••• 372,375 

Aeschynite _____________________ 374,378,392,399,403 mining operations on_____________________ 374 

Alluvium_____________________________________ 368 gold deposits on.-----·----------------- 372,375 

Amalgamation. ____ -------------------------- 407 Fluorite.------------------------------------- 373 

American Eagle claim._______________________ 379 Foliation·----···----------------------------- 367 

Anatase.-----------------------------·----- 374,378 

Andalusite. _ ------------------------------- 367,374 

Anglesite _______ -------------------- _ ----- _ ___ 370 

Apatite _____________________ 366,367,372,374,378,404 

Arsenopyrite_---------------------- 369,374,378,403 

Azurite ________ --------------_________________ 370 

Barite •••••• _. _________ ----·-______ ---_---•••• 

Bedrock, age _________ -------------------·----

374 

366 

exposures _______ -----------------_________ 381 

lithologic description_____________________ 366 

terraces _____________ 370,383,385,388,391,393,394 

Biotite monzonite.--------------------------- 366 Brookite ________________________________ 367,374,378 

Cache Creek, cassiterite deposits_____________ 374 

gold deposits----------------------------- 374 

Calcite.---------------------------- 367,369,379,382 

Cassiterite, association with tourmaline_______ 373 

content_ ____ 375,387,392,393,394,403,404,408,409 

discovery--------------------------- 374,379,392 in gravel deposits _______________ 368,370, 372, 387 

location of deposits_---------------------- 372, 

374, 375, 376, 379, 383, 395, 396, 403 

lode source._----------------------------- 397 origin ___________________________ 367,369,398-403 

outside Tofty tin belt ___________________ 396-398 

percentage recovery_------------------- 403-404 

produced from placer deposits____________ 364, 

375, 376, 379, 386, 387' 403 

recovery of._--------------- 387,403,405,406,408 reserves of __________________________ 365,411,412 

yield._--------------------------------- 364,403 

Chalcopyrite._------------------------------- 369 Chromite ___________________________ 367,374,382, 398 

Cleopatra claim._-------------------------- 386,389 

Copper, native·------------------------------ 378 

Galena.------------------------ 369,370,374,378, 403 

Garnet.----·-------------------------··---- 367, 374 

Gold, association with cassiterite •• ·-------- 365, 369 

content..--------------------------------- 375, 

387, 392, 393, 394, 403, 404, 408, 409, 410 

discovery------------------- 364,374,377,379,384 

in gravel deposits -------------- 368,370,372,387 

location of deposits. 372, 374, 375, 376, 390, 391, 394 

lode source.------·-------------------·--- 397 

outside Tofy tin belt.-------------------- 396 

recovery ________________ 387,403,405,406,407,408 

yield. __ ---·----------------·------------ 403 

Golden Straw claim.----------- 374,386, 389,390,391 

Good Hope claim ••• -------------------- 387,389,390 

Gravel deposits, lithologic description ••• 371, 372, 375 

thickness _______________ ---------------- 377, 387 

Graywacke •• -------------------·-•• 366,368, 376,381 

Hard Luck claim •••• ---·--------------------- 387 

Harter Gulch, cassiterite produced in_________ 376 

gold produced in------------------------- 376 

Hematite •• --------------------------------- 369,398 History of mining in area_____________________ 364, 

365, 374, 375, 382,383, 387, 388, 394 

Idaho Gulch, cassiterite deposits in........... 383 

gold deposits •• -----·--------------------- 382 

gravel deposits in •• -----·----------------- 383 

history of mining_________________________ 382 

intrusive body in.------------------------ 398 

other name for ••• ------------------------- 383 

physiographic features.------------------- 383 

Igneous rocks, location ••• ------------------ 365, 367 Ilmenite ____________________________ 367,374,392,398 

Joplin jig ••••••••• ---------------------------- 407 

Dalton Gulch, cassiterite produced in.------- 376 Location of area •• ----·------------·----------

gold produced in_________________________ 376 Lode deposits--------------------------------

364 

369 

Deep Creek, cassiterite deposits on _________ 372,376 Lorain claim---------·-··-------------------- 393 

gold deposits on._------------------------ 372 

placer claims on .••• 386, 387, 388, 390; pis. 40, 41 

topographic features ____________________ 385,390 

Dikes. ________ --------------------- ____ ------ 367 

Discovery claim______________________________ 369 

Drill holes in area.------------- 389,391,394,395,397 

Eakin, H. M ., quoted __________ 379,380,382,383,386 

Epidote.----------------------------------- 372,374 

Erythrite _________ ---------------- ____ ___ ___ __ 370 

Magnetite •• -------------------- 366, 367,374,392,398 

Malachite •• __ .----___ .-------. ____ ----------- 370 

Marietta claim.------------ 374, 386,387,389,390, 391 

Mertie, J. B., Jr., quoted •. ----------------- 387,388 

Mohawk claim----------------------------- 392,393 

Miller Gulch, cassiterite deposits in__________ 384 

gold deposits in ••• ------------------------ 384 

mining activitY--------------------------- 385 

physiographic features____________________ 383 

413 
414 INDEX 

Page Page 

Monazite ___________________ 367,374,378,392,399,403 Richards workings_-----·-------------------- 376 

Monzonite ________________ ----------------- 366,399 

Niobate _______________ ------ ________________ _ 374 

Olga claim.---------------------------- 387,390,391 

Pearl Fraction ____ -------------------------- 390, 391 

Phyllite______________________________________ 366, 

367, 368, 373, 376, 381, 385, 388, 389, 391, 393, 398 

Picotite. _ -------------------------- 367, 374, 392, 398 Placer deposits, age _________________________ 365,399 

depth oL________________________________ 365 

economic importance_------------------ 369,370 

location __ -------------------------------- 370 

mode of accumulation_------------------- 368 

origin_----------------------- ______ 368, 370,374 

redistribution oL________________________ 399 

relation to drainage basin_________________ 370 

total recovery from _____________________ 403,404 

Population of area____________________________ 365 

Pyrite ______________________ 369,374,379,382,392,403 

Pyrrhotite ______________________________ ------ 369 

Quartzite----------------------------------- 367,368 

Quartz veins_------------------------------ 369,382 

Rachel claim_------------------------------- 3872 

Sluicing __ ---------------------- 403, 404, 405, 406,411 

Specific gravity determinations _____________ 406,407 

Sullivan Bench, cassiterite deposits on_. 377,378,382 

gold produced on ___________________ 377,378,382 

mining activity on. __ ------------------ 377,379 

Tailings, cassiterite content ____ ------------ 404,408 

description of rocks in_------------- 370,371,391 

gold content__-------------------- __ 404,408, 410 sampling oL ___________________ 402,404,407,409 

Terraces ________________ 370,383,385,390,391,393,394 

Titanite ____________________________________ 372,374 

Tofty Gulch, bedrock exposures in----------- 381 

cassiterite deposits in ___________________ 379,380 

gold deposits in------------------------- 379,380 

gravel deposits in_________________________ 380 

physiographic features____________________ 380 

Tourmaline __ ----------------------------____ 366, 

367, 369, 373, 381, 384, 391, 394, 398, 399 

Tourmalite--------------------------------- 375,381 

Wild Goose claim_----------------- 374,386,390,391 

Woodchopper Creek, cassiterite deposits on__ 372, 

392 

gold deposits on __ ---------------------- 372,392 

placer claims ___ ------------------------ 392, 393 

Recovery, methods oL _________________ 403,407,409 Xenotime __ -------------------------------- 374,378 

of cassiterite______________________________ 403 

percentage ______________________________ 403,404 Zircon __________________________ 367,374,378,392,399 

0