TIN-BEARING PLACER DEPOSITS NEAR TOFTY,

HOT SPRINGS DISTRICT, CENTRAL ALASKA

BY BRUCE 1. THOMAS

t * * Sl * * *t * Report of Investigations 5373

UNITED STATES DEPARTMENT OF THE INTERIOR

Fred A. Seaton, Secretary

BUREAU OF MINES

Marling J. Ankeny, Director

Work on manuscript completed May 1957. The Bureau of Mines will welcome reprinting of this paper, provided

the following footnote acknowledgment is made:"Reprinted from Bureau of MinesReportof Investigations5373"

December 1957
TIN-BEARING PLACER DEPOSITS NEAR TOFTY,

HOT SPRINGS DISTRICT, CENTRAL ALASKA

by

Bruce 1. Thomasi/

CONTENTS

Page

Summary ...................................................... I

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

Acknowledgments ............................................. 4

Location and accessibility .................................. . 4

Physical features and climate ...... .......................... 5

History and production ....................................... 6

Property and ownership . ................................. .... 7

Water supply .............. . . .......... ................... .... 7

Description of deposit ................................ ..... 8

General geology . ................................... . .... 8

Physical characteristics and mineralization ............ . 9

Bureau of Mines work ................................... .... 12

Objectives and procedures ............................. 12

Churn-drill sampling methods and results . . ..... 12

Tailing-pile-sampling methods and results-.... -. ': ..... 37

Mine examinations ........ .............................. 48

Tin reserves . .............................. .............. 55

ILLUSTRATIONS

1. Index map of Alaska ..................................... 2

2. Index map, Tofty tin belt, Alaska ....................... 3

3. Tofty tin belt, Alaska .................................. 10

4. Index of topographic maps, showing churn-drill-hole

sites . ................................................ 11

5. Topographic map, with churn-drill-hole sites, Miller

Gulch and Deep Creek .................................. 14

1/ Mine examination and exploration engineer, Bureau of Mines,

Region I, Juneau, Alaska.

Report of Investigations 5373
ILLUSTRATIONS (Con.)

Fig. Page

6. Topographic map, with churn-drill-hole sites, Miller

Gulch and Deep Creek ....... .......................... 15

7. Topographic map, with churn-drill-hole sites, line 300,

Sullivan Creek ................... .................... 16

8. Bedrock topographic map, with churn-drill-hole sites,

Miller Gulch and Deep Creek .. ........................ 18

9. Bedrock topographic map, with churn-drill-hole sites,

lower Miller Gulch ... ............................. . 19

10. Placer sections, drill lines 11-1/2 and 6-1/2. 20

11.. Placer sections, drill lines 15, 5, 6, and 7 .20

12. Placer sections, drill line 17,Miller and Idaho Gulches. 21

13. Placer sections, drill lines 8, 19, and 20-1/2 21

14. Placer sections, drill lines 300 and 9 22

15. Topographic map, with churn-drill-hole sites, Tofty and

Idaho Gulches. 32

16. Bedrock topographic map, with churn-drill-hole sites,

Tofty and Idaho Gulches .33

17. Placer sections, drill lines J, R, C-R, and K. 34

18. Placer sections, drill lines M and N .34

19. Placer sections, drill lines 0 and Q. ... 35

20. Placer sections, drill lines 1-A, 07, 03, and O-Q 35

21. Placer sections, drill lines 02, 01, and 02-1/2. 36

22. Placer sections, drill lines 2 and 6. 36

23. Placer sections, drill lines 8 and 10. 37

24. Topographic map, with churn-drill-hole sites, Sullivan

Creek ..... ........ .38

25. Bedrock topographic map, with churn-drill-hole sites,

Sullivan Creek. .. 39

26. Placer sections, drill lines S-5 and S .40

27. Placer sections, drill lines S-P, 3, 5, and C. 40

28. Placer section, drill line A .41

29. Placer sections, lines 7-1/2, 8-1/2, 11, 9-1/2, and

10-1/2 .41

30. Placer sections, drill lines 13, 14, and FH-DF 42

31. Placer sections, drill lines E, F, and G .42

32. Placer sections, drill lines H and I . .43

33. Index map of tailing-pile sampling .44

34. Sample and topographic map, tailing pile A .49

35. Sample and topographic map, tailing pile B .50

36. Sample and topographic map, tailing pile C .50

37. Sample and topographic map, tailing pile D .51

38. Sample and topographic map, tailing pile E .51

39. Sample and topographic map, tailing pile F .52

40. Sample and topographic map, tailing pile G. 52

41. Sample and topographic map, tailing pile H .53

42. Sample and topographic map, tailing pile I .53

43. Sample and topographic map, tailing pile J .54

44. Sample and topographic map, tailing pile K. 54

45. Cross section through Larsen shaft, Deep Creek. 56
TABLES

Page

1. Mineral production from Tofty placers through 1956 ...... . 7

2. Summary of drilling and sampling results, Miller Gulch

and Deep Creek .... ..................................... 17

3. Summary of drilling and sampling results, Sullivan Creek . 22

4. Summary drill-hole prospect data, Miller Gulch ..... ...... 23

5. Summary drill-hole prospect data, Tofty and Idaho Gulches. 24

6. Summary drill-hole data, Sullivan Creek ........ .......... 27

7. Assay of tin cobbles ..................................... 43

8. Spectrographic analyses of concentrates from Deep Creek

area . ................................................... 45

9. Summary of channel-sampling results, tailing pile A,

Miller Gulch ................. 45

10. Summary of channel-sampling results, tailing pile B,

Miller Gulch ............... 46

11. Summary of channel-sampling results, tailing pile C,

Deep Creek ................ 46

12. Summary of channel-sampling results, tailing pile D,

Deep Creek ............... 46

13. Summary of channel-sampling results, tailing pile E,

Deep Creek ...... ......... 47

14. Summary of channel-sampling results, tailing pile F,

Deep Creek ............... 47

15. Summary of channel-sampling results, tailing pile G,

Idaho Gulch ...... ......... 47

16. Summary of channel-sampling results, tailing pile H,

Woodchopper Creek ............... 47

17. Summary channel-sampling results, tailing pile I,

Dalton Gulch ............... 48

18. Summary of channel-sampling results, tailing pile J,

Cache Creek ............... 48

19. Summary of channel-sampling results, tailing pile K,

Harter Gulch ...... ......... 48
SUMMARY

As a part of the United States Department of the Interior program for develop- ing natural resources in Alaska, the Bureau of Mines studied the tin-bearing goldplacer deposits in the Tofty area of the Hot Springs district in central Alaska.

The principal objective of the Bureau's work was to obtain facts about the extent

and character of the placer deposits (including tailing) to indicate the economic

or strategic tin-production potential of the Tofty "tin belt." A secondary objective was to determine (if possible) the bedrock source of the cassiterite and other

minerals found in the placer deposits.

The placer phase of the work was begun in July 1954 and was continued during

the 1955 and 1956 field seasons. Extensions to, and connections between, known

placer channels were sought by 82 churn-drill holes. The Bureau drilling did not

expand the placer deposits beyond the limits established by drift-mining operations

and by previous drilling done by private concerns.

Extensive prospect-drilling data submitted by private operators were compiled

by the Bureau's engineer and are included with this report by special permission of

the owners. These data designate the holes in which cassiterite was noted (in relative amounts only) and infer a strategic reserve of tin within the drilled areas;

additional unmined reserves in other parts of the Tofty area may be inferred on the

basis of geologic evidence and the results of former mining operations.

Eleven tailing piles, representative of former drift mining along the principal placer channels, were trenched by tractor dozer, and the sides of the trenches were

systematically channel-sampled; average tin content of the sampled piles ranged

from a trace to as much as 6.9 pounds per cubic yard. Inferred reserves of all

drift-mine and open-pit tailing throughout the length of the tin belt are estimated

to be 1,259,000 cubic yards containing 733,000 pounds of tin; the tailing also may contain as much as 17,700 ounces of gold.

In addition to gold and cassiterite, spectrographic and petrographic studies

of concentrates from the placer deposits established the presence of small amounts

of ilmenite, rutile, chromite, magnetite, scheelite, zircon, monazite, columbite,

eschynite, and ellsworthite.

INTRODUCTION

The association of tin minerals with gold in the extensive placer deposits near

the abandoned mining town of Tofty in the Hot Springs district of central Alaska

(fig. 1) has long been known, and some cassiterite has been recovered as a "nuisance"

byproduct of gold mining. Few systematic attempts to save the cassiterite were made,

and much of the tin was wasted. Mining records are scarce and incomplete.
1500 30

Figue ndexmapof 1 lask. (rro ponsroTftoieae.
E o ft y~~~51 15o 5 40 d

N/ote: A fter P/a~te / Geo/. Survey| lYois

i Manleycale M//es of 

Figure 2. - Index mop, Tofty tin belt, Alaska.
4

Because wartime demands for tin focused much attention on the Tofty tin belt,

the Bureau of Mines began systematic sampling of tailing in the area during the

early spring of 1943. The work was discontinued after the dumps from one large

opencut on Sullivan Creek2/ had been sampled. The results of the work were inconclusive but indicated that the numerous tailing dumps and potentially large, unworked gold placers in the Tofty area may contain an important strategic reserve

of tin that could be recovered in an emergency or, with proper equipment and favorable markets, as a byproduct valuable enough to stimulate additional mining and

exploration. The character of the placer deposits and other geologic evidence

strongly suggested a local or nearby bedrock source of the cassiterite and other

placer minerals.

As a part of the Interior Department's continuing program for developing

Alaska natural resources, particularly strategic mineral deposits, the Bureau of

Mines resumed its work in the Tofty area in July 1954 and continued it during the

1955 and 1956 field seasons. The principal purpose of the work was to indicate the

tin-production potential of the placer deposits, but attention also was given to

determining the lode sources of the placer minerals. The lode phase of the investigation is still in progress and will be described later. This report presents data

resulting from the placer phase of the Tofty investigation; it includes information

obtained from work by the Bureau of Mines and pertinent data contributed by private

operators.

ACKNOWLEDGMENTS

The Alaska Road Commission gave unstinted cooperation in providing much needed

repairs to the access roads and lending camp equipment for use by the Bureau crew.

Special acknowledgment is extended to Harold Strandberg of Strandberg Mines,

Inc., for making available many valuable drilling data and to Tom Dean for the use

of camp facilities and for drill-hole sampling records.

Appreciation is expressed to Clyde Larson and A. W. Pringle for the use of

equipment and parts; such use prevented much lost time and was of great assistance

in promoting the efficiency of the mechanical phases of the investigation. Lloyd

Hubbard and Frank Jones gave valuable help and extended many courtesies to members

of the Bureau of Mines crew.

LOCATION AND ACCESSIBILITY

The Tofty tin belt (named after the abandoned mining town of Tofty) is about

32 miles east of the confluence of the Yukon and Tanana Rivers at longitude 1510001

W., and latitude 65°05' N. (figs. 1 and 2). The nearest settlement is Manley Hot

Springs, which has a population of about 25 in winter and about 50 in summer. It

has a small general store, where bulk quantities of fuel oil and gasoline can be

purchased, a roadhouse, a post office, a commissioner and recording office, a

weather and radio station, and a small, commercial airfield. Small truck gardens

supply the local demands for in-season vegetables and fruits. A good truck road

about 20 miles long connects Tofty with Manley Hot Springs; an adequate telephone

system also connects both localities. During the summer freight is brought in from

the coast by railroad to Nenana, where it is transferred to river boats that deliver

2/ Thorne, R. L., and Wright, W. S., Sampling Methods and Results at the Sullivan

Creek Tin Placer Deposits, Manley Hot Springs, Tofty, Alaska: Bureau of

Mines Rept. of Investigations 4346, 1948, 8 pp.
5

it to Manley Hot Springs landing; from there it is hauled to Tofty by truck. Freight rates differ widely according to commodity but are generally high by Stateside standards. Most travel is by airplane in summer as well as in winter. A small air- field near Miller Gulch serves the immediate area.

Fairbanks, the largest town in central Alaska and the principal source of sup- plies and labor, is approximately 90 miles east of Tofty. Regular air-mail and

passenger service is maintained between Fairbanks and Manley Hot Springs; flights direct to Tofty may be made by special arrangement. Light freight,as well as fresh meats and produce, is usually transported from Fairbanks by plane. Heavy freight is shipped from Fairbanks by river boat direct to Manley Hot Springs or by railroad to Nenana, thence by river boat to Manley Hot Springs landing.

A highway now being constructed will connect the local road network at Manley Hot Springs with Livengood, about 70 miles northeast. When this highway is com- pleted, the Tofty area will be connected to the main interior Alaska highway system; thereafter, landed-freight costs should be substantially decreased.

PHYSICAL FEATURES AND CLIMATE

The Tofty tin belt is near the western extremity of the Yukon-Tanana upland; it consists of low, rounded ridges that rise from the broad valley floor of Patterson Creek. Patterson Creek and its tributaries flow in valleys that are much larger than would be required for their normal streamflow. Two prominent landmarks, Rough- top Mountain (altitude 3,179 feet) and Hot Springs Dome (altitude 2,682 feet) flank the placer area to the northeast and southeast, respectively.

The climate is typical of the subarctic region of central Alaska; winters are long and cold, and summers are short and relatively warm. The alluvial deposits

are permanently frozen, except along the courses of some streams and in some areas that have been drift-mined. In summer the ground thaws to a depth of only a few feet; this relatively thin mantle of thawed ground usually freezes down to the permafrost level during the winter. The penetration of seasonal frost, over per- manently thawed areas, is controlled to a great extent by the depth of snow in winter. The snow provides a layer of protective insulation, which restricts the depth to which the ground freezes. A thick layer of moss, which blankets much of the area, also provides effective insulation against the seasonal freezing and restricts the depth of seasonal thawing. Natural (solar) thawing can be acceler- ated during the summer by removing the moss and by periodic removal of thawed muck.

The annual precipitation (12 to 13 inches) is comparable with that in other

areas in central Alaska. Snow covers the region from mid-October until early May; its depth ranges from 3 to 4 feet on the level. The spring runoff is rapid, because the frozen ground prevents normal absorption or underground circulation of-the sur- face water. In summer the moss retards drainage; consequently, much of the precipi- tation is held on or near the surface. The broad valley floors and gentle slopes a

are marked with numerous small lakes, potholes, and large areas of swampland or "muskeg," which make overland travel during the summer season difficult - particu- larly for heavy equipment.

Dwarf spruce is distributed widely over the region; sparse growths are found high on hill slopes and along valley courses. Occasional patches of spruce trees 2 feet or more in diameter grow along Patterson Creek near the lower end of the valley. Thick growths of birch and poplar are on unfrozen ground along the south- ward-facing hill slopes. An occasional birch or poplar grows among the thickets of willow and alder that line the stream courses.
6

Except in thickly timbered areas, on some southward facing slopes or in the

occasional grassy meadows, the ground is covered with moss, brush, and creeping

plants. Timber for mining purposes and for fuel is obtained from lower Patterson

Creek to the southwest and from the headwater tributaries of Baker Creek to the

northeast. Large areas have been cut over to supply wood fuel for the steam boilers used in the mining operations.

HISTORY AND PRODUCTION

The original discovery of gold in the placers was made on Tofty Gulch in the

winter of 1906-07. Considerable prospecting with churn drills and shafts and a

large amount of underground drift mining, as well as some opencut mining, have been

done in the area during the past 50 years; much of this work was done within a few

years after the stampede that followed the original discovery of gold. No permanent

records were made of the early prospecting results or of early drift-mining accomplishments. The first systematic churn-drill sampling of which there is a permanent

record was done in the early 1930's to block out opencut reserves, but only sketchy

mention of tin or other heavy-mineral content was incorporated in the recorded

drill-hole data. A permanent record was also made of churn-drill hole sampling

done a few years later. Some of these data have been made available to the Bureau

of Mines for limited use in preparing reports covering the area.

Cassiterite was a plentiful byproduct of the early operations but because of

the generally unprofitable market was seldom saved; nevertheless, some clean concentrate was sold to local merchants at prices as low as 5 cents per pound delivered

to boat landings. Wagon or pack-animal freight from the mines to points of delivery

consumed a considerable proportion of the sales price. In 1929 a shipment of Tofty

concentrate assaying 57.9 percent tin is reported to have been sold for 123 pounds

sterling in Singapore; net proceeds to the shipper at Tofty were about $400.00 a

ton. Most recorded tin production from the area occurred after 1929. No special

equipment or methods were employed to recover the cassiterite; the production resulted from such heavy-mineral concentrates as could be recovered conveniently in

the conventional sluicebox used in gold-placer washing methods.

Numerous piles of drift-mine tailing along upper Cache Creek, Idaho Gulch,

Miller Gulch, Deep Creek, and Woodchopper Creek mark the positions of old shafts

and roughly outline the course of the pay channels followed during the early period

of intense underground activity. Relatively little drift mining has been done in

recent years; but occasionally a working shaft is sunk during the winter by 2 or 3

men working as partners. The volume of material mined by these partnerships usually

is small; the value of the gold recovered rarely exceeds wages or a small grubstake

for each partner. Inefficient wood-fired boilers were, and still are, used to furnish steam for hoists and pumps and for thawing equipment. Because of the small

size, poor quality, and sparse distribution of the native timber, fuel cost for the

wood-burning boilers is exceptionally high.

During the winter of 1953-54 a working shaft was sunk on Deep Creek by two

partners. Mining operations were conducted from this shaft during the winter of

1954-55. The operation was visited by the writer and is described on pages 48 and 55

of this report. According to reports, Strandberg Mines, Inc., plans to reopen

the pits at Tofty Gulch and Sullivan Creek and to develop other mineral-bearing

areas along the tin belt.

The total recorded mineral recovery from placers in the Tofty tin belt, as

compiled from old and recent records, is tabulated by pay channel or location as

follows:
7

TABLE 1. - Mineral production from Tofty placers through 1956

Cassiterite

Gold, Silver, concentrate,

Place ounces ounces pounds

Sullivan Creek .58,13 58,136 5,463 215,445

Miller Gulch .17,57 17,576 2,668 101,875

Deep Creek .6 8 6 4 6,864 ...... 653 56,200

Woodchopper Creek ...... ..... 28,501 3,402 40,300

Patterson Creek .2 599 2,599 385 20,282

Tofty Gulch ............ 8,855 1,376 19,600

Hokeley Gulch 820 8,000

Cache Creek .3,650 409 5,155

Dalton Gulch .466 3,000

Idaho Gulch . .61 ....... 6300

Total 127,528 14,356 470,157

According to reports, the average tin content of the cassiterite was 60 percent.

On this basis the recorded tin recovery from the Tofty area is approximately 280,600

pounds or 125.3 long tons of metal.

PROPERTY AND OWNERSHIP

Pay channels along the tin belt are covered by both patented and unpatented

mining claims.

Mining claims on Sullivan Creek, Tofty Gulch, and Idaho Gulch are owned by

L. V. and Helen McGee of Reno, Nev.; these claims currently are leased to Strandberg

Mines, Inc., of Anchorage, Alaska. Claims in Miller Gulch are held by the Tom Dean

estate and the George Millianich estate of Manley Hot Springs, Alaska. The A. Bock

estate holds mining claims on both Woodchopper and Deep Creeks; these claims now are

leased to Strandberg Mines, Inc. Henry Besonen of Fairbanks, Alaska, has claims on

Deep Creek, and the George Rolke estate holds mining claims on Woodchopper Creek.

Fred Hansen and associates, of Fairbanks, Alaska, hold a group of claims on Deep

Creek. Claims on Cache Creek are owned by Gus A. Benson and associates, of Manley

Hot Springs, Alaska.

The records of unpatented mining claims are on file at the recording office at

Manley Hot Springs; records of patented mining claims are on file at the office of

the Bureau of Land Management, Anchorage, Alaska.

WATER SUPPLY

During most of the summer enough water flows in Sullivan Creek to supply the

demands of open-pit operations at Sullivan Creek and at Tofty Gulch. During dry

periods it is practical to recirculate water from settling ponds. Gravel dumps

accumulated from winter drift mining usually are sluiced in the spring, while runoff

water is abundant in the numerous small ponds and streams.

If opencut mining develops to the extent that the present water supply becomes

inadequate, small dams could be built to impound water from the upper drainage

basins of Sullivan and Woodchopper Creeks.
8

DESCRIPTION OF DEPOSIT

General Geology

The geology of the Tofty area and that of the gold-tin placer deposits have

been described in detail by Eakin,3/ Mertie,A/ Waters,5/ and others. The following

brief discussion is based on a summary of the geological information contained in

the various publications and on field observations by Bureau of Mines engineers.

The Tofty placers are along the north side of the valley of Patterson and

Sullivan Creeks, which occupies a broad, alluvial-filled depression between Roughtop Mountain and Hot Springs Dome. Both mountains are prominent uplifts composed

of granitic rocks believed to be of Tertiary age. The area, known as the "tin belt"

because cassiterite is a prominent constituent of the placers, extends from Woodchopper Creek on the southwest to Killarney Creek, a headwater tributary of Baker

Creek on the northeast. The belt includes parts or all of the valleys of Woodchopper

Creek, Deep Creek, Miller Gulch, Idaho Gulch, Tofty Gulch, Sullivan Creek, and Cache

Creek, with its upper tributaries Harter Gulch, Dalton Gulch, and Ferguson Gulch;

all these creeks are tributaries to Patterson Creek or to its principal branches

(fig. 3). The tin belt, about 12 miles long, trends S. 700 W.; the long axis of

the belt roughly parallels the dominant structure of the country rock.

Nearly all of the placer workings are along the gulches that drain the hills

on the north side of the Patterson Creek-Sullivan Creek Valley, or more commonly

the ground lying along the sides of such gulches; consequently each group of workings trends normal to the tin belt (fig. 3). Individual pay streaks cut off rather

abruptly as they were followed northward or upstream; however, although the northerly economic limits of the deposits were rather sharply defined, additional prospecting has indicated that rapidly diminishing but appreciable amounts of gold and

tin extend considerable distances beyond the formerly accepted line of sharp cutoff.

Where the gulches merge southerly into the main valley, the gold and tin content

decreases gradually - probably because of dispersion; furthermore, the greater depth

to bedrock in the main valley imposes limitations on mining.

The country rock of the tin belt, where exposed on the surface and in mine

workings, is sheared and contorted phyllite, schist, quartzite, graywacke, and

slate, in which lenses and stringers of quartz are numerous and pyrite is abundant.

These rocks are believed to be of Cretaceous age; where observed in underground

workings and in cuttings from churn-drill holes, they have been subjected to intense

and deep-seated weathering. Quartz veins and stringers that contain trace amounts

of tin have been found in and adjacent to the placer area, and some lodes that contain small amounts of gold and silver have been found near the granite of Hot Springs

Dome; however, very little lode prospecting has been done along the tin belt because

rock outcrops are scarce and the deep frozen overburden makes exploration by trenching slow and expensive.

Granitic intrusives and associated dikes are exposed on Roughtop Mountain

about 6 miles north of the placer deposits and on Hot Springs Dome, which at its

3/ Eakin, Henry, M., A. Geologic Reconnaissance of a Part of the Rampart Quadrangle,

Alaska: Geol. Survey Bull. 535, 1913, pp. 35-38.

4/ Mertie, J. B., Jr., Mineral Deposits of the Rampart and Hot Springs District

Alaska: Geol. Survey Bull. 844-D, 1934, pp. 163-224.

5/ Waters, A. E., Jr., Placer Concentrates of the Rampart and Hot Springs Districts:

Geol. Survey Bull. 844-D, 1934, pp. 224-246.
9

nearest point is 5 miles south of the tin belt. Although cassiterite has not been

found in the intrusives or their associated dikes, trace amounts of tin have been

identified in concentrate panned from the headwaters of streams directly draining

the granitic exposures. A study of the intrusive rocks by Waters6 / indicates that

the granite of Hot Springs dome is similar in chemical composition and quantitative

classification to the granites with which most of the major tin deposits of the

world are associated. The Roughtop Mountain intrusive is classed as a monzonite

which differs considerably from typical tin granites; therefore it is considered a

less likely source of the tin minerals. Quartz-tourmaline rocks, similar to those

found near Ohio Creek, which cuts the granite 3 miles southeast of Hot Springs dome,

are found as cobblestones in the drift tailings on Woodchopper Creek and Deep Creek.

Thus far the dominant evidence points to the granite of Hot Springs dome, or a related but unexposed intrusive, as the most likely source of the tin minerals found

in the placer deposits.

Physical Characteristics and Mineralization

The gravel in most creeks along the tin belt is composed chiefly of subangular

to poorly rounded pebbles and cobbles of phyllite and slate, but it also contains

well-rounded fragments of quartzite, graywacke, and quartz. However, the gravels

of lower Woodchopper and Deep Creeks near the western end of the tin belt are composed chiefly of quartz; these are known as "white gravels."

The shallower parts of the deposits contain 3 to 10 feet of gravel overlain

by 10 to 20 feet of silt, commonly referred to as "muck"; the deeper parts of the

deposits contain 5 to 45 feet of gravel overlain by 10 feet to 120 feet of muck.

On lower Woodchopper Creek the depth to bedrock is reported to be over 200 feet.

In most places the gravel and muck are permanently frozen.

In general, the gravel contains only a moderate amount of clay; consequently,

it is easily mined when thawed. However, according to reports, the gravel in lower

Woodchopper Creek contains considerable, tightly compacted clay, which makes it

difficult to mine.

The frozen muck is essentially silt which contains veins and lenses of ice,

frozen plant and animal fossil remains, and considerable sand and gravel, some of

which is in thin layers and some of which is mixed with the silt. Sand and gravel

in the muck do not interfere seriously with drift-mining operations but do add considerably to the expense of open-pit mining because, when the silt is removed by

the usual hydraulic methods, the contained sand and gravel accumulate on underlying

muck sections where they impede stripping progress; if not removed they dilute the

underlying pay gravel.

The bedrock is principally weathered phyllite and black slate, with some quartzite and graywacke; in places the slate contains much pyrite. Gold, cassiterite, and

associated heavy minerals usually are found in the lower 2 feet of the gravel and

the upper 2 feet of bedrock. The surface of bedrock is irregular; in places it

rises abruptly as much as 20 feet. On the slopes of the abrupt rises, muck rests

directly on bedrock without intervening gravel. Little or no gold, cassiterite,

or other heavy minerals are found where there is no gravel.

6/ Work cited in footnote 5, p. 8.
~~~ ~~Legend\

CD0,en-poz; orcas- 'in oeorI17.

Or rif-r7/neareas- t/n Dear//7q

im roapect7eaf oreo- fin indic<7teO

~~~~ ~~~by churn7 dri/llng ondp/rOspeCt 0 ~~ ~~~~~~~~~ Hot Srig

S c ale of tni/es

7.-~. -3)3e 9Fgu4 

Figure 3. - Tofty tin belt, Alaska.
Legel7d

Opencuts

Lokes

1/00

60

70o

600

U

00

70o

1.

60

C Cr 100 0

0

00 Q)

0 3,000 6,000 9,000

'Po 0 Cr 0

SC 0/6 of Aes t 0 Cantou interval- /00 feet

0 0

0 0

Figure 4. - Index of topographic maps, showing churn-drill-hole sites.
12

The gold and cassiterite in the placer deposits occur together or in proximity.

A high concentration of gold usually indicates a similar concentration of cassiterite

in the same area or in proximity but not necessarily together; tin enrichment containing little gold and vice versa has been noted in recent underground workings on

Deep Creek. Areas of separate gold and tin enrichment are so small, however, that

the minerals are recovered together in mining.

The cassiterite ore occurs as well-rounded to slightly subangular gravel ranging in size from microscopic particles to cobbles as much as 6 inches in diameter.

The larger particles and cobbles contain vein quartz and numerous angular fragments

of rock believed to be of sedimentary origin; the cassiterite, with associated tourmaline, fills fractures in the quartz and the spaces between the angular fragments

of sedimentary rock. The smaller particles of cassiterite ore, minus-4-mesh and

smaller, are fairly free from gangue minerals; they can easily be concentrated to aproduct assaying 60 percent or more tin. The larger particles and cobbles vary considerably in tin content (see table 7, p.43); they would have to be crushed to produce a high-grade concentrate.

BUREAU OF MINES WORK

Objectives and Procedures

The objectives of the Bureau of Mines work at Tofty were to indicate the tin

and other heavy-mineral production potential of the placer deposits (including

tailing), to determine if the tin mineralization extended beyond the limits established by early drift-mining operations, and to determine, if possible, the bedrock

source of the placer minerals. Fieldwork consisted of churn drilling, sampling and

surveying of drift-mine tailing piles, examination of active underground operations,

topographic mapping, angledozer trenching, and accumulation and compilation of extensive drill-hole data resulting from exploration by former operators. Laboratory

work included further concentration of field samples by tabling and analyses of the

resulting concentrates by chemical, spectrographic, and petrographic processes.

Churn-Drill Sampling Methods and Results

Churn-drill sampling (fig. 4) was begun on Miller Gulch with line 11-1/2,

about 2,500 feet upstream and north of the pay channel, as indicated by evidence of

old underground workings. Successive lines were drilled downstream in accessible

places until unfrozen, swampy ground made further drilling impractical in this area.

Reconnaissance drilling was continued on higher ground along the northern margin of

the placer deposits, into Idaho Gulch, and down the gentle slope normal to Sullivan

Creek Valley, as well as across the head of Deep Creek. The sum of all drilling

completed was 3,198 linear feet in 82 holes. The locations of drill lines are shown

in figures 5, 6, and 7; the bedrock topography is shown in figures 8 and 9; placer

sections through drill lines are shown in figures 10 through 14, inclusive. The

extension of line 17 is shown in figure 15.

A portable-type, modified, 6-inch churn drill was used. Thin placer bits,

forged to 5-5/8 inches, were used in open and cased holes. Heavy, special, 6-inch

drive pipe with a 7-1/2-inch shoe was used when thawed ground was tested.

Bulk samples were reduced to a concentrate of heavy minerals by a hand-operated

gold pan and rocker. Drill-hole logs show the character of materials drilled and

the depth of each change in material. Muck overburden is barren; therefore it was

discarded without being sampled. Gravel was sampled at intervals of 2 feet until
13

panning revealed the presence of gold, cassiterite, or other heavy minerals; then

the sampling interval was reduced to 1 foot. Holes were drilled into bedrock for at

least 5 feet.

Each pumping was deslimed, measured loose in a special measuring bucket, and

panned. Concentrate from each panning was examined in the field, then combined for

a composite panning concentrate for each hole. Tailing from panning was put through

a rocker, from which a sample identified as "rough concentrate from rocker" was

recovered. Rocker tailing was pipe-sampled at each hole. Slime was tested in the

field from time to time to determine if any heavy minerals were being carried away

in the fines.

Panning concentrate, rough concentrate from rocker, and pipe samples of rocker

tailing were shipped to the Bureau of Mines laboratory at Juneau, Alaska. At Juneau

the rough concentrates from rocker and pipe samples of rocker tailing were concentrated further on a laboratory-size, Deister-type table to recover such heavy minerals as may have been lost in the field; however, little or no valuable heavy minerals were recovered by tabling. Gold particles were separated from heavy-mineral

concentrates by visual methods to conform with standard placer-evaluation procedure;

gold so obtained was weighed and recorded in milligrams.

Concentrate samples were assayed for tin and given preliminary examinations

for other heavy-mineral content. Drilling and sampling results are summarized in

tables 2 and 3. The small amounts of tin, gold, and other heavy minerals obtained

from most of the drill holes did not justify quantitative estimates for each hole.

The Bureau drilling did not locate extension of known pay channels within the

area investigated.

All cuttings from drilling in bedrock were examined carefully for evidence of

lode mineralization; no valuable ore minerals were identified.

Basic churn-drill-hole data from 348 placer prospect holes drilled during

former mining operations were made available to the Bureau by present operators and

property owners for use in preparing placer sections and bedrock topographic maps.

This information was compiled and, by permission of the owners, is included with

Bureau of Mines data to indicate the depth of overburden, thickness of gravel section, and bedrock topography of the tin-placer deposits; gold values have been

omitted, except where specifically permitted by the operator.

A summary of data obtained from early drilling on Miller Gulch, compiled from

prospect logs furnished by Tom Dean, is given in table 4 (p. 23); no quantitative

estimates of tin were entered on the original drill logs. Although much of the

area drilled has been mined, these data are included with this report to indicate

the characteristics of a typical "pay channel" on Miller Gulch. Sampling results

from tailing piles A and B, summarized in tables 9 and 10, are roughly representative of the tin content of gravels mined from the area. Bedrock topography is shown

in figure 8; placer sections through drill lines are shown in figures 11 and 13.
00~~~~~~~~

\ Dr/l/-line number\

\ o8 DrIll-hole, number'

\ \X;< ' ~Out/&n0 dr/ft-rnine, fal&7 ,, , \\9v /

0 300 600 900 /,200 9 X \ \,

'\ Scale 7f of ieX h f ooo~~-. C~Ont-our' Interval- 20 fe-et

Oeep Cre -0

e '"1 ;go \ * \ 0 2 ~~~~0 t Hi 60 -

Figure 5. - Topographic map, with churn-drill-hole sites, Miller Gulch and Deep Creek. ) .~~~~~~~~~~~~~~~~~0
<~~~~

0, ; \ & , Y . < 0 \

)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

< \ Ox / \ ,/ f g,, ~~~~~~~~Scale of feet

Figure 6. - Topographic map, with churn-drill-hole sites, Miller Gulch and Deep Creek. 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I.
TABLE 2. - summsary of drilling and sampling results, Miller Gulch and Deep Creek 17

6-inch holes, drilled open (without casin)

Total Depth Depth Depth Value/cu. Yd. Surface

Line Hole depth, 0.B., gravel, bedrock Conc., Gold, Tin, Tin, Gold, Ground elev.,

No. No. ft. ft. ft. ft. 9m MR. percent lb. troy oz. condition ft.

11-1/2 2 29.0 4.0 21.0 4.0 17.6 0 < 0.05 Tr. Tr. Fr. 711

4 29.0 4.0 11.0 14.0 10.9 0 < .05 do. do. do. 698

5 40.0 6.0 29.0 5.0 62.8 Tr. .10 do. do. do. 684

6 28.0 3.0 21.0 4.0 131.8 do. .10 do. do. do. 677

7 20.5 3.0 13.0 4.5 11.3 do. .20 do. do. do. 672

8 16.0 3.0 13.0 0 33.8 5.75 .10 do. do. do. 665

9 12.0 1.0 11.0 D 9.9 Tr. - do. do. do. 661

10 15.0 5.0 6.0 4.0 6.7 2.10 .20 do. do. do. 658

11 6.0 3.0 Aband. 0 5.3 Tr. - -- Fr. & Th. 654

V ~~~ ~~12 8.0 7.5 do. 0 - ---- do. 653

13 17.3 9.0 2.0 6.3 11.9 Tr. .20 Tr. Tr. Fr. 648

14 15.0 5.0 4.0 6.0 11.1 5.50 .10 do. do. do. 643

15 17.4 3.0 11.0 3.4 14.1 Tr. .10 do. do. do. 637

16 14.5 3.0 6.0 5.5 15.3 do. < .05 do. do. do. 631

17 15.3 5.0 6.0 4.3 33.5 do. < .05 do. do. do. 627

18-1/2 19.5 7.0 5.0 7.5 48.9 do. .05 do. do. do. 625

19-1/2 18.0 7.0 8.0 3.0 6.6 do. .05 do. do. do. 628

14 6-1/2 47.0 8.0 36.0 3.0 22.4 0 < .05 do. 0 Fr. & Tb. 565

8-1/2 40.9 9.0 31.9 0 20.6 Tr. .10 do. Tr. Fr. 554

10 23.5 8.0 9.0 6.5 47.02 1.0 < .05 do. do. do. 551

10-1/2 24.5 4.0 11.0 9.5 45.74 6.41 < .05 do. do. do. 552

11 22.0 4.0 14.0 4.0 28.88 0 .48 0.002 do. do. 552

11-1/2 22.0 2.0 11.0 9.0 76.88 57.0 1.12 .013 0.013 do. 551

12 20.0 2.0 13.0 5.0 118.93 192.0 1.98 .020 .023 do. 550

13 12.3 1.0 6.0 5.3 34.66 12.12 .66 Tr. Tr. do. 549

14 15.4 3.0 4.0 8.4 27.50 3.84 .17 do. do. do. 550

15 18.5 3.0 4.0 11.5 21.20 .98 < .05 0 0 do. 548

16 15.0 5.0 2.0 8.0 12.00 0 < .05 0 0 do. 548

17 16.4 6.0 1.0 9.4 30.30 0 < .05 0 0 do. 548

18-1/2 22.0 5.0 2.0 15.0 30.60 7.14 < .05 0 Tr. do. 549

19-1/2 18.0 7.0 6.0 5.0 20.00 6.09 < .05 0 .Tr. do. 553

20-1/4 19.0 7.0 6.0 6.0 21.30 .0 .10 Tr. 0 do. 553

15 12-1/2 22.0 6.0 5.0 11.0 1.60 Tr. Tr. 0 0 Th. 559

13 12.0 7.0 2.0 3.0 7.60 do. do. 0 0 Fr. 560

14 17.25 7.0 5.0 5.25 18.60 0 do. 0 0 do. 560

15 19.75 1.5 9.5 8.75 43.80 Tr. do. 0 0 do. 555

16 16.7 4.0 7.7 5.0 21.60 do. do. 0 0 do. 554

17 13.0 4.5 3.5 5.0 7.30 do. do. 0 0 do. 555

17 4 6.0 6.0 0 0 0 0 0 0 0 Th.

7 27.0 11.0 11.0 5.0 90.7 0 < .05 0 0 Fr. 537

8 27.0 8.0 14.0 5.0 83.6 0 .05 Tr. 0 do. 536

9 31.0 10.0 14.0 7.0 19.0 0 1.1 do. 0 do. 534

10 37.0 12.0 20.0 5.0 29.3 0 do. 0 0 do. 533

11 43.0 10.0 28.0 5.0 20.4 2.0 .2 Tr. Tr. do. 534

12 48.0 12.0 30.0 6.0 39.5 3.0 .6 do. do. do. 534

15 40.0 7.9 32.2 0 103.9 12.0 Tr. 0 do. Fr. & Th. 527

15-1/2 16.0 12.0 4.0 0 41.9 0 0 0 0 do. 526

16 12.0 12.0 0 0 30.6 5.0 Tr. 0 Tr. do. 526

16-3/4 22.0 6.9 15.2 0 20.6 1.0 0 0 do. do. 525

17-3/4 18.0 8.0 10.0 0 19.0 Tr. 0 0 0 Th. & Fr. 527

18-3/4 50.0 9.0 36.0 5.0 26.5 2.0 Tr. 0 Tr. Fr. 527

19 18-1/2 20.0 20.0 0 0 - - - Tb. 505

20 82.0 35.0 43.0 4.0 3.2 59.0 34.3 Tr. 0.006 Fr. 507

22 79.0 34.0 40.0 5.0 22.9 1.0 Tr. 0 Tr. do. 506

10-1/2 30 79.2 29.0 42.0 8.2 74.4 0 < 0.05 Tr. 0 Fr. 507

2 59.0 42.0 10.0 7.0 50.1 Tr. Tr. 0 0 do. 507

3 56.0 42.0 8.0 6.0 25.9 0 do. 0 0 do. 505

20 17 95.9 45.0 42.0 8.9 101.7 2.0 < .05 0 Tr. do. 497

24 105.0 36.0 64.0 5.0 55.1 0 Tr. 0 0 do. 499

20-1/2 17 110.0 45.0 60.0 5.0 44.1 18.0 2.7 Tr. Tr. do. 493

19 115.0 44.0 66.0 5.0 97.1 Tr. Tr. 0 0 do. 493

* ~~~9 14 34.0 18.5 5.0 10.0 - 0 -- 0 do. 504

18 42.0 15.0 14.0 13.0 - 0 - -0 do. 505

22 72.0 30.0 31.0 11.0 23.7 0 0.10 Tr. 0 do. 515

26 98.0 43.0 48.0 7.0 19.1 0 .05 0 0 do. 513

28 101.0 51.0 38.0 12.0 7.2 0 .05 0 0 do. 513

17 6 48.0 5.0 36.0 7.0 108.5 26.0 2.3 Tr. Tr. do. 555

10 54.0 10.0 39.0 5.0 130.4 1.4 .14 do. do. do. 555

14 55.0 10.0 41.0 4.0 28.3 Tr. < .05 0 0 do. 555

15 56.0 8.0 43.0 5.0 32.1 0 .10 0 Tr. do. 557

16 21.0 8.0 8.0 5.0 41.3 0 < .05 0 0 do. 556

17 25.0 7.0 13.0 5.0 97.6 0 < .05 0 0 do. 555

18 8.0 7.0 1.0 0 Fr. & Th. 554

19 21.0 5.0 9.0 7.0 30.4 0 < .05 0 0 Fr. 555

20 23.0 10.0 8.0 5.0 53.4 Tr. < .05 0 0 do. 554

Fr. = Frozen.

Th. = Thawed.

Tr. = Trace.

< = Less than.
0o

00

6 Drill-/lne number

o 6 DrI//-ho/e nunmber

0 ~300 600 900 1200Y

Sca/e of feet

Contotur inerva- /-0 feet h/

0gr8-Bdokoorhcawtcu-rlhlstsMleGlhaDepre Q~~~~~1

Figue 8 - apwit edrck oporapic chrn-dillhol siesMiler ulc an Dep Ceek
0 ~ ~ ~ 0

Legend

6 DrIll-line number o 8 Dr//l-hole, number

0 300 600 900 ,200

Scal-e of fee- Contour /ntervol- /0 feet

0 30

Figure 9..- Bedrock topographic map, with churn-drill-hole sites, lower Miller Gulch.
20

/91X/ey2 17 5 30

i; i t;9/9; 0{wJ1L ne 14

14) /9y2 /7 /5 /3 //Y /Ova 6 z L egend

20Y4 /8a /6 /4 /2 // /0 8&2 1=-=1 Grve U~~~~ 560 ~ 1 -|Grolvel ~~~~~ T- -- --- Be drock =-/ Ll 

I Drill hole5 ____________ ~~~~530

0 200 t400 600 0 30 60 90

Horiz 5co/e Infeet Vert 5ca/e,/n feet

Figure 10. - Placer sections, drill lines 1PA2 and 6A2.

Line- /5 Line S

/6 /¢ /12 7 9 /I

560 6 8 / 560

~~~~~~~~~541 J40 JJ

Llne 6 Line 7

3 5 7 9// 3 5 6

2 4W 6 8 /0 5 4 JYa 8S

JZO 510 L~~~~ eqend

_ _ _ _ _z -- - - - - - _ E si/f

- - Eli G~ravel

-F°-490 * Bedrock

71M, F O~~~~~~~~~~~rill ho/es

0 /00 200 300 thmbeS 0 20 40 60

Horiz.scale in feet Vert sca/e in feet

Figure 11. - Placer sections, drill lines 15, 5, 6, and 7.
21

L/ne /7

0 Z0 40 60 /71 /6/5 // 9 7

r | * | , /8% /61 /Y4 /2 /0 8 540

Vert sc Cale in f e e f

0 200 400 600

H-or/z 5 c a/e in fe e

Legend Line /7 Idaho Gulch

E 5i/t

1= Gravel /9 /7 /5 6

11 Bedrock 20 /8 /6 /4 /0

|Drill h o/e s_5=7 - 0

ifri~~~~~~t;,~~ '' I v1A I;:':'-. 7- -I,..: a

Figure 12. - Placer sections, drill line 17, Miller and Idaho Gulches.

L ine 8 Li7ne /9

30 22 20 18 y

3 4 5 7 530 - _ ____

____=___- _ - 40-= 70

0 30 60 90

Li/ne 2?0~ 1/Vert s cale /n feet

/9 /7 /7 Legend

_-=- Si/f

_ _ _ _ _ _ _ _ _ _ _ - I:E ':: i=Grave/

_ Bedrocl( __ _ __ _. -I0 D Dri// holes

4Z0 0 40 80 /20

Vert scale In feet

30 0 100 200 300

Hor/z. sca/e /n feet

Figure 13. - Placer sections, drill lines 8, 19, and 20A2.
22

Li/ne 300

538 55S 4

_ _-=_- _ _- _ _ = ~~~~~~~~~~~30 1500

a , ''':''''~~ ,,,'-tVAy'4V.S '.<','S'.t," a d0X

L eqend

L /ine 9

e Z 8 J-3 J Gravel /4 /6' 2Z 26 28 3? 33 1-. 6Bedrock

Or./! hole5

-f - -<:< =-= 470 0 30 60 90

- ._ . : -. _ _ Vert scale infeet

.a : .- . 440

0 /00 200 300

Hforiz. sc ale, In fe et

Figure 14.- Placer sections, drill lines 300 and 9.

TABLE 3. - Summary of drilling and sampling results, Sullivan Creek

Depth

Total Depth Depth bed- Tin, Value/cu. yd. Ground Surface

Line Hole depth, O.B., gravel rock, Conc., Gold, per- Tin, Gold, condi- elev.,

No. No. ft. ft. ft. ft. gm. mg. cent lb. troy oz. tion ft.

300 30 78.5 15.0 53.0 10.5 213.83 11.44 0.20 Tr. Tr. Fr. 489

45 106.5 37.0 44.0 25.5 606.8 Tr. .06 do. do. do. 502

53 112.2 49.0 38.0 25.2 848.1 56.16 .20 do. 1/0.0004 do. 508

55 108.3 44.0 42.0 22.3 486.0 33.00 .19 do. Tr. do. 512

58 83.5 43.0 30.0 10.5 80.72 Tr. .05 do. 0 do. 516

Fr. = Frozen.

Th. = Thawed.

Tr. = Trace.

1/ Mining section, 45 ft.
23

Drill-hole data from prospecting on Tofty and Idaho Gulches and on Sullivan

Creek were made available by Harold Strandberg of Strandberg Mines, Inc. These data

are summarized in tables 5 and 6, respectively; no values are given, but relative

amounts of tin are shown. The locations of drill lines and holes, bedrock topography, and placer sections on Tofty and Idaho Gulches are shown in figures 15-23,

inclusive; similar graphic data for Sullivan Creek are shown in figures 24-32.

TABLE 4. - Summary drill-hole prospect data, Miller Gulch

5-inch holes drilled open (without casing)

Data published with permission of owner:

Total Depth Depth Depth Tin, Valu /cu. yd. Surface

Line Hole depth, O.B., gravel, bedrock, Gold, per- Tin, Gold, Ground elev.,

No. No. ft. ft. ft. ft. mg. cent lb. troy oz. condition ft.

5 4-1/2 40.0 19.0 19.0 2.0 Tr. 0

6 43.0 13.0 27.0 3.0 28.0 0.004 Fr. 555

7 37.0 17.0 16.0 4.0 Tr. do. 556

8 38.0 18.0 17.0 3.0 57.0 .015 do. 556

9 39.0 19.0 16.0 4.0 Tr. do. 555

10 41.0 15.0 23.0 3.0 32.0 .009 do. 554

11 35.0 26.0 6.0 3.0 Tr. do. 553

6 2 46.0 27.0 15.0 4.0 10.0 Tr. do. 539

3 43.0 26.0 15.0 2.0 7.0 do. do. 539

4 43.0 26.0 14.0 3.0 27.0 do. do. 539

5 42.0 25.0 11.0 6.0 185.0 .085 do. 539

6 41.0 20.0 18.0 3.0 20.0 .007 Fr. & Th. 538

7 40.0 25.0 13.0 2.0 100.0 .049 Fr. 538

8 40.0 26.0 10.0 4.0 35.0 .021 do. 538

9 39.0 20.0 16.0 3.0 43.0 .014 do. 538

10 40.0 15.0 22.0 3.0 30.0 .008 do. 540

11 37.0 18.0 16.0 3.0 0 do. 540

7 2 54.0 30.0 20.0 4.0 27.0 .005 do. 531

3 53.0 30.0 17.0 6.0 58.0 .018 do. 531

4 48.0 24.0 21.0 3.0 112.0 .034 do. 531

5 47.0 22.0 19.0 6.0 Tr. Tr. Fr. & Th. 530

5-1/2 45.0 21.0 21.0 3.0 57.0 .012 do. 528

6 49.0 35.0 10.0 4.0 Tr. Tr. Fr. 528

8 52.0 30.0 16.0 6.0 15.0 .005 do.

8 3 58.0 36.0 16.0 6.0 15.0 .006 do. 526

4 59.0 33.0 20.0 6.0 205.0 .060 do. 525

5 59.0 30.0 25.0 4.0 18.0 .004 do. 525

7 50.0 30.0 20.0 0 Tr. I Tr. Fr. & Th. 522

Fr. = Frozen.

Th. = Thawed.
24

TABLE 5. - Summary drill-hole prospect data, Tofty and Idaho Gulches

Published with permission of owner:

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin, Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

J 8 6.5 13.5 No Fr. 530 523 509.5

9 7 14 No do. 531 524 510

10 9 9 Yes do. 531 522 513

11 6 22 No do. 531 525 503

13 10 16 No do. 530 520 504

14 8 12 No do. 530 522 510

15 9 12 No do. 530 521 509

16 8 16 No do. 532 522 506

17 13 16 No do. 534 521 505

18 10 14 No do. 535 525 511

19 10 14 No do. 539 529 515

20 16 6 No do. 543 527 521

K 11-1/2 7 16 Yes do. 526 519 503

14 9 19 Yes do. 527 516 497

15 10 18 No do. 524 514 496

16 10 18 No do. 522 512 494

17 8 20 No do. 524 516 496

18 11 17 No do. 523 512 495

CR C27 20 6 do. 532 512 506

R28 23 9 do. 530 507 498

R27 32 2 do. 528 496 494

R26 28 5 do. 526 498 493

R R29 30 13 do. 525 495 482

R30 27 16 do. 523 496 480

R31 38 3.5 do. 528 490 486.5

M 0 14 34 No do. 550 536 502

2 17 29 No do. 543 526 497

4 18 4 No do. 537 519 515

6 20 16 No do. 529 509 493

8 29.5 18.5 Yes do. 525 495.5 477

9 28 16 Yes do. 521 493 477

10 26.5 20.5 Yes do. 518 491 471

11 25 20 No do. 516 491 471

12 18 27 No do. 514 496 469

13 19.5 26.6 Yes do. 512 492.5 466

15 10 30 Yes do. 507 497 467

16 10 16 Yes do. 504 494 _

N 8 30 25 Tr. Fr. 531 501 476

10 26 28 Tr. do. 525 .499 471

12 20 35 Yes do. 523 503 468

14 21 2 No Fr. & Th. 521 500

16 14.5 31.5 Yes Fr. 514 499.5 468

18 4 37 No do. 505 501 464

0 06 22 14 No do.

04 19 24 No do. 560 541 517

02 15 30 No do. 554 539 509

0 14 34 No do. 550 536 502

Fr. = Frozen. Th. Thawed.
25

TABLE 5. - Summary drill-hole prospect data, Tofty and Idaho Gulches (Con.)

Published with permission of owner:

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin, Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

0 2 19 34 No Fr. 545 526 492

(Con.) 4 27.5 18.5 No do. 542 515 496

6 19 25 No do. 539 520 495

8 30 29 Yes do. 537 507 478

10 30 30 Yes do. 532 502 472

12 22 34 No. do. 525 503 469

14 25 27 No. do. 522 497 469

16 24 27 No. do. 519 495 468

18 12 37 No. do. 512 500 463

1-A 1 8 39 No do. 563 555 516

2 7 37 No do. 565 559 521

3 8 35 Yes do. 566 559 523

4 12 33 Yes do. 567 555 522

5 10 36 Yes do. 568 558 522

6 10 33 No do. 568 558 525

7 20 20 No do. 569 549 529

07 6 10 45 No do. 560 550 505

7 10 38 Yes do. 560 550 512

8 8 32 Yes do. 561 553 521

03 10 8 28 No do. 553 545 517

11 12 25 No do. 554 542 517

12 20 18 Yes do. 554 534 516

13 18 21 No do. 554 536 515

14 15 23 No do. 554 539 515

02-1/2 12 22 15 Yes do.

13 23 20 Yes do.

14 16 22 No do.

02 5 9 39 No do. 547 538 499

7 5 42 No do. 549 544 502

9 7 37 No do. 551 544 507

10 9 32 Yes do. 551 542 510

11 7 36 Yes do. 551 544 508

12 10 37 Yes do. 552 542 505

13 15 32 Yes do. 552 537 505

14 18 22 No do. 552 534 512

15 20 25 No do. 552 532 507

17 10 31 No do. 552 542 511

19 12 34 No do. 553 541 507

21 14 24 No do. 553 539 515

01 8 10 33 Yes do. 546 536 502

9 6 37 No do. 545 539 502

10 15 30 Yes do. 545 530 500

11 9 30 Yes do. 547 538 508

12 8 34 Yes do. 549 541 507

1 13 12 30 Yes do. 549 537 507

Fr. = Frozen. Th. = Thawed.
26

TABLE 5. - Summary drill-hole prospect data, Tofty and Idaho Gulches (Con.)

Published by rmission of owner:

Top Top

Depth Depth Surface gravel bedrock

Line Hole 0.B., gravel, Tin, Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

2 5 24 20 Yes Fr. 538 514 494

7 10 34 Yes do. 540 530 496

9 12 38 Yes do. 542 530 492

11 18 30 Yes do. 541 523 493

13 18 22 No do. 542 524 502

15 18 21 No do. 542 524 503

17 16 22 Yes do. 543 527 505

19 18 20 No do. 544 526 506

21 16 25 No do. 545 529 504

6 03 32 6 No Fr. & Th. 530 498

01 40 32 Yes Fr. 530 490 458

1 34 38 Yes do. 529 495 457

5 28 40 Yes do. 530 502 462

7 33 34 Yes do. 529 496 462

9 34 25 Yes do. 529 495 470

11 39 19 No do. 531 492 473

13 12 46 Yes do. 532 520 474

15 33 34 Yes do. 534 501 467

17 28 33 Yes do. 542 514 481

19 28 27 Yes do. 537 509 482

21 25 30 Yes do. 538 513 483

8 1 33 38 Yes Fr. 526 493 455

5 26 41 Yes do. 526 500 459

7 28 38 Yes do. 527 499 461

9 34 31 Yes do. 529 495 464

11 36 27 Yes do. 528 492 465

13 34 29 Yes do. 530 496 467

15 36 30 Yes do. 533 497 467

17 43 24 Yes do. 537 494 470

19 40 22 No do. 537 497 475

21 30 29 Yes do. 536 506 477

10 1 40 30 Yes do. 523 483 453

3 35 35 Yes do. 523 488 453

5 36 32 No do. 525 489 457

7 35 33 No do. 527 492 459

9 35 34 No do. 529 594 460

11 29 40 Yes do. 528 499 459

13 30 36 No do. 529 499 463

Q 04 5 40 No do. 552 547 507

02 8 44 Yes do. 546 538 494

0 7 44 No do. 542 535 491

2 12 38 No do. 537 525 487

4 18 36 No do. 534 516 490

6 33 28 Yes do. 529 496 468

8 31 42 Yes do. 527 496 454

O-Q 2 15 20 No do. 560 545 525

4 17 27 No do. 559 542 515

6 12 24 No do. 558 546 520

8 10 30 Yes do. 554 544 514

Fr. = Frozen. Th. = Thawed.
27

TABLE 6. - Summary drill-hole data, Sullivan Creek

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin, Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

s-5 11 22 5 Fr. 617 595 590

12 20 5 do. 616 596 591

13 27 5 do. 621 594 589

14 29 8 do. 632 603 595

15 34 2 do. 635 601 599

16 41 5 do. 638 597 592

17 42 2 do. 641 599 597

18 42 4 do. 644 602 598

19 48 4 do. 647 599 595

20 50 6 do. 651 601 595

21 48 8 do. 655 607 597

22 52 13 do. 658 606 593

23 55 13 do. 662 607 594

24 62 4 do. 665 603 599

25 67 3 do. 668 601 598

26 66 6 do. 672 606 600

S 11 36 4 do. 624 588 584

12 35 9 do. 627 592 583

13 36 9 1/ 630 594 585

14 39 10 1/ 634 595 585

15 43 6 1/ 636 593 587

16 47 4 Ti 640 593 589

17 53 3 T/ 645 592 589

18 57 4 T/ 648 591 587

19 60 0 I/ 652 592 592

20 66 2 T/ 658 592 590

21 65 4 Fr. 662 597 593

22 68 2 do. 666 598 596

23 67 9 do. 668 601 592

24 70 9 do. 670 600 591

25 71 8 do. 670 599 591

26 68 9 do. 670 599 592

27 70 15 do. 670 600 585

28 72 15 do. 671 599 584

29 75 11 do. 674 599 587

S-P S-8 37 5 do. 608 571 566

S-7 39 1 do. 610 573 572

S-4 41 4 do. 614 573 569

S-3 44 4 1/ 612 568 564

P-2 8 4 T/ 579 571 567

P-6 9 4 Ti 581 572 568

P-7 13 0 1/ 584 571 571

Fr. = Frozen.

1/ = Mined out.
28

TABLE 6. - Summary drill-hole data, Sullivan Creek (Con.)

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin, Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

3 6 44 2 Fr. 609 565 563

7 46 5 do. 609 563 558

8 50 2 do. 612 562 560

9 50 2 do. 614 564 562

10 48 8 do. 616 568 560

11 54 0 1/ 618 564

5 5 43 6 do. 605 562 556

6 45 4 do. 605 560 556

7 43 6 do. 606 563 557

8 44 7 do. 607 563 556

9 43 6 do. 607 564 558

10 45 3 do. 608 563 560

11 45 4 do. 608 563 559

7-1/2 4 38 9 2/ 593 555 546

5 40 10 2/ 595 555 545

6 43 6 2/ 596 553 547

7 42 9 2/ 599 557 548

8 42 8 2/ 598 556 548

9 43 8 2/ 599 556 548

10 41 10 2/ 599 558 548

8-1/2 3 45 5 2/ 597 552 547

5 43 12 2/ 596 553 541

6 39 14 2/ 596 556 542

7 40 12 2/ 596 556 544

8 38 11 2/ 595 557 546

9 40 7 2/ 595 555 548

10 43 6 2/ 596 553 547

9-1/2 6 39 12 2/ 594 555 543

7 40 9 2/ 592 552 543

8 39 9 -2/ 591 552 543

9 40 7 2/ 591 551 544

10 48 2 2/ 592 544 542

11 45 3 2/ 593 548 545

12 47 1 2/ 594 547 546

13 47 1 2/ 594 547 546

14 45 1 2/ 596 551 550

Fr. = Frozen.

1/ = Old workings.

2/ = Mined out.
29

TABLE 6. - Summary drill-hole data, Sullivan Creek (Con.)

Top ToP

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

10-1/2 6 32 13 Fr. 584 552 539

7 38 8 1/ 585 547 539

8 40 6 1/ 588 548 542

9 42 3 1/ 589 547 544

10 42 4 1/ 589 547 543

11 40 4 T/ 590 550 546

12 44 3 T/ 591 547 544

13 43 3 T/ 592 549 546

15 41 6 I/ 594 553 547

17 6 3 Yes Fr. 562 556 553

18 5 5 No do. 562 557 552

19 5 8 No do. 562 557 549

20 0 8 Yes do. 563 563 555

21 0 9 Yes do. 563 563 554

22 0 18 Yes do. 570 570 552

11 8 38 8 do. 586 548 540

9 39 7 do. 587 548 541

10 39 8 do. 588 549 541

11 40 8 do. 590 550 542

12 41 6 do. 591 550 544

13 46 3 do. 592 546 543

18 0 12 do. 561 561 549

19 0 13 do. 562 562 549

13 7 46 11 Yes do. 590 534 523

9 50 8 No do. 592 542 534

11 52 10 Yes do. 595 543 533

13 53 12 Yes do. 600 547 535

15 56 9 Yes do. 601 545 536

14 9 49 10 Yes do. 590 541 531

11 50 8 No do. 592 542 534

13 53 7 No do. 595 542 535

15 56 8 Yes do. 597 541 533

17 60 10 Yes do. 603 543 533

19 64 9 Yes do. 606 542 533

21 67 9 Yes do. 611 544 535

23 75 2 No do. 617 542 540

Fr. = Frozen.

1/ = Mined out.
30

TABLE 6. - Summary drill-hole data, Sullivan Creek (Con.)

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

A 14 49 8 No Fr. 634 585 577

16 53 8 No do. 632 579 571

18 50 18 No do. 638 588 570

20 59 12 No do. 641 582 570

22 68 12 No do. 647 579 567

24 61 9 No do. 652 591 582

26 26 4 No do. 660 634 630

28 23 2 No Fr. & Th. 669 646 644

30 24 30 No Fr. 674 650 620

32 41 1/ 6 No do. 668 1/627 621

34 35 1/ 9 No do. 661 1/626 617

36 20 1/20 655 1/645 625

38 33 1/25 No - 647 1/614 589

40 46 T/ 4 No Fr. 641 1/595 591

C 2 23.75 7 No do. 582 558 551

3 25 6 No do. 583 558 552

4 27 7 No do. 584 557 550

5 29.5 7 No do. 585 555 548

6 30 9 No do. 589 559 550

7 35 11 No do. 594 559 548

D-F 2 41 16 Yes do. 614 541 531

3 73 10 Yes do. 612 539 529

4 73 10 Yes do. 609 537 526

6 72 11 Yes do. 607 535 525

8 72 10 Yes do. 606 538 519

10 68 19 Yes do. 600 532 513

F-H 2 67 14 Yes do. 594 527 513

6 65 14 Yes do. 594 529 515

8 61 18 Yes do. 588 527 509

E 9 23 10 No do. 568 545 535

10 23 12 No do. 571 549 537

11 22 11 No do. 571 549 538

12 26 10 No do. 572 546 536

13 24 15 No do. 577 553 538

14 30 12 No do. 577 547 535

Fr. = Frozen.

Th. = Thawed.

1/ = Slide.
31

TABLE 6. - Summary drill-hole data, Sullivan Creek (Con.)

Top Top

Depth Depth Surface gravel bedrock

Line Hole O.B., gravel, Tin Ground elev., elev., elev.,

No. No. ft. ft. present condition ft. ft. ft.

F 11 22 8 No Fr. 565 543 535

12 27 10 No do. 568 541 531

13 24 16 No do. 570 546 530

G 2 6 10 No do. 548 542 532

3 10 6 No do. 548 538 532

4 4 11 No do. 547 543 532

5 9 8 Yes do. 548 539 531

6 11 10 Yes do. 548 537 527

7 9 13 Yes do. 548 539 526

8 6 15 No do. 547 541 526

9 8 14 No do. 549 541 527

10 16 12 No do. 551 535 523

H 8 7 14 No do. 541 534 520

9 7 14 No do. 543 536 522

12 15 16 No do. 545 530 514

14 18 17 No do. 549 531 514

16 21 20 No do. 557 536 516

18 26 21 No do. 561 535 514

20 38 18 No do. 569 531 513

22 46 18 No do. 575 529 511

24 56 21 No do. 582 526 505

26 67 20 Yes do. 594 527 507

28 75 22 No do. 602 527 505

30 79 10 No Fr. & Th. 607 528 518

I 1 16 10 No Fr. 554 538 528

3 14 8 No do. 546 532 524

5 13 6 No do. 538 525 519

7 7 14 No do. 538 531 517

8 5 15 No do. 538 533 518

9 9 11 No do. 537 528 517

Fr. = Frozen.

Th. = Thawed
0 I~

\C) OQ 0O-1-

00~~~~~~~~~~~~~~~

0 0

Legend\ tf, ~~~~~ol 6 0o o (/e 70 L egend 0 027 N ~ ~~~~~~ 0L:::0

6 Dr///-11ne-tnumber \ JO >\/°3'_< - _ 9

DrIrn-hoseo number F \ a a Gulches. ~t-Out/ine- drift-mine to///ng \_

--- Ou111ne open-pit taillng / < e'/ v W> / Y o \

<u, 0 300 600 1° 200<o\

00 Contour intervo/-ZO/ )\/0

Figure 15. - Topographic map, with churn drill-hole sites, Tofty and Idaho Gulches.
tX X

0~~~~~~~~~~~~~~~~~~

0 :WE T0' tX Oc aX} S0Al0 

O 300 600 900 goc 42'00 / / / I I

Scnle of feeft

Contour /r terva/- /0 feeft / g / 0 / 0/ | | \ \ /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ V~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Figure 16. - Bedrock topographic map, with churn-drill-hole Col 00 0 0 O 8 0 sites, 0 0 Tofty 0 and 2 Idaho Gulches. (5 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~J
34

LIne,d

9z 1/ /4 /6 /8 20

8 /O 13 /5 17 /9Q

Line R L/ne C-R t Llne K

R30 ~ R28 P26

R29 p31 C27 R27 // 1 /6 57

Legend

r--== Silf

rn Grovel 0 200 d00 600 0 30 60 90

EO Bedrock

Z0ri// ho/es //loriz. ccale In feet Vert scale n feet

Figure 17. Placer sections, drill lines J, R, C-R, and K.

Line, M c

0 2 4 6 83 9 /0 /2 /3 /5 /6

~530

tn.N ci

8S /0 /2 /4 /6C /8 53 0

L e-gend

_---1 S/'/ l_ =500

Gravel 1. Bedrock

12ri// Ho/e5 70

0 200 400 boo 0 30 60 90

horiz scale in fee t Vert 5cale in fee t

Figure 18. - Placer sections, drill lines M and N.
35

j _ _ _ L ine 0- 06 04 02 0 a 4 6 a /0 /2 14 16 /8 ; 5~~~~~~~~~~~~~~~60

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5~ ~~~~~~~3 0

-=7 '~~~~~~5001 . _ _ ~~~~~~~~~~~~~~~~~~~-7 -- 7 ,7 _

Line,

0.4 Oa 0 Z 4 6 8 3 L egend

1 . | ,., , . . drock . .. . ._ __ 1 Ae 

0 /00 0000 00 /0 0 0 30 60 go orl sco/c ale fene fe H Vert oceo/e in feet

F igure 19. Plcer sections, drill lines 0 and Q.

Line /-,A I/n OZ, LIne, 03

/e 3 4 S5 5 7 __ _ _ -r _ . ~~~6 7 6 /0 1// 3 14 6

_ 

_~~~~~~~~~~~~~~~~~~77, 

_ .s__ 0,

_ 5 t"<r ~~~~~~~~~~~~~~~~~5

.Leg9end L ine O- 47

mSilt

= 6ra~vel 4 2

GEI Bedrock 560

Dril/ ho/es ____===-

,500

0 /00 e00 300 0 130 60 90

H6oriz. .5c a/e in fe at Vert scalc in feet

Figure 20. Placer sections, drill lines I-A, 07, 03, and O t;.
36

LZ 61 02

02 5 7 9 /0//2 /3 /S /7 /9 2/ 02

560

_ _~~~~rvl w' '" vr-- 500

L/ne 0/ Line 02&,

8 9 /0/ /2 /3 /2 /3 /4 560

-- ~~~530

__ _ _ _ _ _ L e gend 500

0 /00 200 300 OBedrok 0 30 60 90

- ' ~~~~~~I Dri// ho/es Maoriz. s ca/e in feet 1 Vert ScC7/e In feet

Figure 21. - Placer sections, drill lines 02, 01, and 02X2.

Legend L /7 e -

ff SW a2 .5 7 9 / 1 /3 /5 /7 /9 2/ 2

= Gravel --

BedrocA - - - ---- - ---- 530

Drill hole ___----- - -

Line 65

0.3 0/ / 6 7 9 // 3 /5 /7 /9 2/ 6

7 /00 E00 300 0 30 60 90

Horiz. scale in feet Vert sco/e in feet

Figure 22.- Placer sections, drill lines 2 and 6.
37

Line 6

/ 8 5 7 9 1I /3/5 /7 /9 8

A __ = ~530

Lin e /0

i 3 5 7 9 / / 1/3 5,/ mGravel

E_2Bedroclk _ __ _ _ _ _ ~500 I DrIll ho/es

O 30 60 90 _ , - .: - .- : : : .4 70 |

Vert scale in feet

7Jr, 'i^\V/A 0/00 200 t 300 A//\ \\'&O /0 

l-/orlz. scole In feet

Figure 23. - Placer sections, drill lines 8 and 10.

Tailing-Pile Sampling Methods and Results

Sampling was done on 11 drift-mine tailing piles (fig. 33), which were selected

as representative of the numerous underground mining operations on the several prin- cipal placer channels along the tin belt; many tailing piles were not tested but are

believed to be of similar composition.

Except during the occasional periods when tin commanded high prices, the cassiterite customarily was discarded with the gold-placer tailing. The tailing piles are

therefore a potential source of tin and also are roughly indicative of the tin content of mining sections in unworked portions of the various pay channels.

Because of the generally flat topography, sluicebox grade was obtained by elevating the boxes. The placer gravels were lifted to the head of the elevated

box, usually by means of a bucket operating on a cable suspended from a ginpole

at the head of the box. As washing proceeded, the tailing boxes were extended outward from the ginpole, and sections were added as necessary to deflect the washed

material away from the riffle boxes. Consequently, most of the tailing piles are

roughly elliptical and are deepest along the long axis of the piles.
p00 0 d SX slSS / if 000 /0

\/ _c \ X\A 02~~~~~~~~~~~~~~~~~

o 0

0~~~~~~~~~~~~~~~~~~~~~~~~~~

\ Contour mfervai 20 

0ef \\ < X 0 0 0 ~~~~~~~0 0

o 

0 

0

0

Figure 24. -Topographic map, with churn-drill-hole sites, Sullivan Creek.
Q -0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

00

02 0 0 0 t 0

At0 0 0 0 02 000 00 0 00 00z

0 0

H 0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~00 0 ~~~~0 0

0 0 0~~~ 0

/~~~~1 /0 tO o o 0 

0/0~~~~~~~~~~0 Figure _o0 0 0 ~ ~~~~~~~~~~~0 0

0 0 0 0 0

0 ~~~~13 0 0 00

0 >o 00o

0 000 0~~~~~~~ 

0~~~~~~~~~~~~~~~~~

0 ~~~~~~~~~0 3 011-oeum e

0~~~~~~~~~~~~~~~

0 0

(~~~~~~~~~~~~~~~~~j~ ~ ~

10~~~~~~~~~~~~~~~

0 ~~~~~~~~~~~0 4

Figue toogrphi 2. Bdroc map wih curndril-ho ste 0 8ulia Cr/l-oee nu be
40

Line' s-5 2z02/ 22 23 z4 z5 26

12 /3 14 15 16 /7 18 /9 _L egend

= = =Grovel

. _______ r-_ _ _ _ -_ 0 1, Bedrock __ _ _ _ = _ _= _ _ _ _ _ W 6ZO0 Drill holes

Lin&s 5 20 2/ 22 23 24 Z5 06 27 28 29

// /2 3 /4 /5 /6 /7 /B I /9_ __ 5

0 /00 200 300 0 30 60 90

Hor/z. scalee In feet Vertsco/e in feet

Figure 26. - Placer sections, drill lines S-5 and S.

Llne 5-P Line, 3

5-7 5-3 7 9 II

S-8 5-4 6 8 /0 620

Po'R P-7 - 5 0 

_ =-1- \-------1_II_

A -- - R 560

Ol/d driff

timbhers

Line 5

5 87 /0 Line C

5- 7_1-q~l-l=l 95 2 3I4 6 7 590

5500

-b ; - 1 =Legend

tE: tGrovel

0 /00 200 300 0 30 60 90 mBedrock

PN = qDPri//I holes

/loriz. Scale in feet Vert sccle in feet 1

Figure 27. - Placer sections, drill lines S-P, 3, 5, and C.
41

Liner A

28 30 32 34. 36 38 40

/4 /6 /8 20 2 2426

-i- - X X ~~~~650

D1 - ---X -- rE - / W1A 620

L __ _ __ j .XS = - A, F ~~~590

> < t ......... .., 2 3~~~1 60

L eqeod 0 300 600 900 0 30 60 90 ;l Si/f ,_ _ _ _ __ _ _ _ _ __ _ _ _ __ _ _ _

F .G6r-ave/ /-oriz. sca/e in feet Vert cai/e in feet I Bedrock

DrI// hole s

Figure 28. - Placer section, drill line A.

Line 7Y. Line 8Ya Line //

6 8 9/0 3 S 7 89 9 //13

7 // ~ 9 / 3 6 8 // /3

4 8 6 2 /0 /4 6 8 /2 /0 /

: S , 11 ~ 'wt ~ -t ~ | / ~~~~~~~~ J60 _- 530 7 9 1I 3 7 9 1I 3

6 8 /0 le /4 608 /0 30 6

ii ~~~~~~~~~~~~~~18 20 e-.50 T 7 /I II

__________ 3~~~~~~~~~60

Pd' -~~~~~~ ~~ Op~~~~ . . : .' ~~~~ 53 0

Legend

E< ravel 0 /00 200 300 0 30 60 900

Bedrock

Drill ho/es5 /oriz 5ca/e/n feet Vert Scnlein feet

Figure 29. - Placer sections, drill lines 71,2, 8Y/2, 11, 9Y2, and 101/2.
42

Line /3 L/ne& /4

/ 7 /9 Z/ Z3 620

7 9 //13 /5 9 // 3 /5,

Lines F//- DF

8 6 2 /O 8 6 ' 3 2 L egend

- -- - - Gtravel 5 

_ _ ...- _ = = _ _ =_ _ _ 590 Wvl tedrock

___- I Ori//I ho/e5

/-/oriz Scale, /n feet Ve rt s cale In f -eet

Figure 30. - Placer sections, drill lines 13, 14, and FH-DF.

L ne. E L ne, F

9 /0 1/ 2 /3 /d /1/2 /3

_-_- _-_ _-_ _= =_ _= =-_-560

-__ __M - _ _ -:- : . ~530

L in e 6,

' 3 4 5 6 7 8 9 '' 560

L eqelnd

BedrocA 0 /0 200 300 0 30 60 90

OD/il holes

Hooriz scale in feet Vert scc/ein feet

Figure 31. - Placer sections, drill lines E, F, and G.
43

L ine- H

ee 24 26 28 30

~~~-a_

8 9 9 ~ ~ ~ /Zle ~ ~ /4 ~ /6 ~ ~ /8 ~ 2 ~ 0e- ~ ~ ~ -_ ~ - ~ = ~ ~ 9

< __ _ _ _-_ - - = _ §~~-560

Line I

5 7 89 L eqend

A_- 1~~~~~~~~ Grave /

530 1;2 9 Bedrock { Drill ho/e s

500

0 200 400 600 0 30 60 90

H/oriz. scale in feet Vert sc ale 1, 1feet

Figure 32. Placer sections, drill lines H and I.

To obtain uniform samples, bulldozer trenches were cut across the center and to

the full depth of the tailing piles wherever possible. Channel samples 1 foot wide

and 1 foot deep were cut from top to bottom of the vertical-sided bulldozer trenches.

The large samples thus obtained were panned to produce a clean concentrate; tailing

from panning was put through a rocker from which a "rough concentrate from rocker"

was obtained.

Tailings from pan and rocker were carefully examined and all coarse pebbles and

cobbles containing cassiterite were included with the concentrate. The larger cobbles generally are low grade, although the tin content may differ considerably, as is

shown by the following analyses of cobbles picked at random from the tailing piles.

TABLE 7. - Assay of tin cobbles

Cobble weight, Tin assay,

grams percent

398.4 0.1

378.8 .2

321.4 18.0

147.6 38.6
Lege d zof

Under-groC ndo lacer operaw/ons

1000~~~~~~~~~~~~~~~~~~~~~~~~~

50o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

06~~~~~~~~~~~

Figure 33. - Index map of tailing-pile sampling. I a~~~~~~~~~~~~~~~~~~Z
45

The proportion of large cobbles of tin-bearing material in the deposits has not

been determined, but visual inspection of the placer tailing dumps and the small

amount of coarse ore recovered from the channel samples indicates that the percentage of ore in pieces larger than 1 inch in diameter is comparatively small.

All tailing-pile-concentrate samples were sent to the Bureau of Mines laboratory in Juneau for tin analyses, separation of free gold, and preliminary examination for other heavy minerals. A typical sample of concentrate from tailing piles

in the Deep Creek area was sent to the Bureau laboratory at Albany, Oreg., for

spectrographic analyses. Results are reported in table 8 as follows:

TABLE 8. - Spectrographic analyses of concentrates from Deep Creek area

Ag Al As Au B Ba Be Bi Ca Cd Co Cr Cu Fe K Li Mg Mn _ ~ ~ __ ~ ~ ~ ~ *~~ ___ _

F A-B - - E E F - D - - C-D F A I D ID

Mo Na Ni Cb P Pb Pt Sb Si Sn Sr Ta Ti V W Zn Zr

D C-D - D - - A A - - C+ C _ _ C

Legend: A - Over 10 percent E - 0.01 to 0.1 percent

B - 5 to 10 percent F - 0.001 to 0.01 percent

C - 1 to 5 percent G - Under 0.001 percent

D - 0.1 to 1 percent - = Not detected

Petrographic studies of concentrate from tailing piles in the Deep Creek area

and from other parts of the tin belt indicated that, in addition to gold and cassiterite, small but varying amounts of ilmenite, rutile, chromite, magnetite,

scheelite, zircon, monazite, columbite, eschynite, and ellsworthite were present.

Tailing-pile sampling results are summarized in tables 9 through 19; sample

locations and topographic surveys of the sampled piles are shown in figures 34

through 44.

TABLE 9. - Summary of channel-sampling results, tailing pile A, Miller Gulch

Vol. in Conc. Gold Conc. analyses Recovery per cu. d.

Channel place, recovered, recovered, Tin, Cb2O5 , Conc., Tin, Cb2 05, Gold,

No. cu. ft. lb. mg. percent percent lb. lb. lb. oz.

1 4.50 0.340 27.63 21.7 3.1 2.04 0.44 0.06 0.005

2 4.08 .569 79.90 .05 3.77 .00 .017

3 3.65 .068 12.41 23.3 5.3 .50 .12 .03 .003

4 4.41 .377 13.85 16.5 3.9 2.31 .38 .09 .003

5 4.03 .332 138.00 41.0 3.0 2.22 .91 .07 .029

6 3.85 .988 188.00 48.3 6.3 6.93 3.35 .43 .043

7 4.25 1.080 34.80 39.6 6.86 2.72 .007

8 4.66 .852 490.95 43.5 4.0 4.94 2.15 .20 .091

9 4.41 .387 40.32 47.7 1.5 2.37 1.13 .04 .008

10 4.25 .227 23.41 38.8 5.5 1.44 .56 .08 .005

11 5.33 .736 36.28 39.7 2.0 3.73 1.48 .07 .006

12 5.08 .318 5.60 33.2 3.8 1.69 .56 .06 .001

13 4.91 .942 9.20 47.2 3.5 5.20 2.44 .18 .002

Average 3.39 1.26 .10 .017
46

TABLE 10. - Summary of channel-sampling results, tailing pile B, Miller Gulch

Vol. in Conc. Gold Conc. analyses Recovery p r cu. yd.

Channel place, recovered, recovered, Tin, Cb205, Conc., Tin, Cb205, Gold,

No. cu. ft. lb. mg. percent percent lb. lb. lb. oz.

14 4.00 0.053 16.04 7.6 4.1 0.36 0.03 0.01 0.004

15 3.58 .931 36.09 15.7 1.9 7.02 1.10 .13 .009

16 4.86 .215 31.44 28.8 3.1 1.19 .34 .04 .006

17 4.41 .164 143.23 31.6 4.5 1.00 .32 .05 .028

18 4.83 .176 134.78 27.0 2.9 .99 .27 .03 .024

19 3.75 .906 160.23 1.8 .2 .52 .12 .01 .036

20 3.08 .055 112.31 11.6 1.1 .48 .06 .01 .032

21 4.33 .087 21.93 10.0 3.5 .54 .05 .02 .004

22 6.08 1.006 318.39 3.0 .7 4.47 .13 .03 .055

23 4.91 .603 37.04 42.2 1.9 3.32 1.40 .07 .006

24 4.91 .171 70.03 24.6 6.0 .94 .23 .06 .014

25 5.33 .103 44.88 28.4 1.5 .52 .15 .01 .007

26 4.58 .079 82.81 4.0 7.0 .47 .02 .03 .016

27 3.50 .050 25.30 11.7 3.6 .38 .04 .01 .006

28 3.25 .117 17.48 29.7 3.1 .97 .29 .03 .005

29 3.00 .058 60.09 6.6 4.3 .52 .03 .02 .017

Average, 1.88 .29 .03 .018

TABLE 11. - Summary of channel-sampling results, tailing pile C, Deep Creek

Vol. in Conc. Gold Tin Recovery per cu yd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

30 1.95 0.273 29.00 27.2 3.78 1.03 0.013

31 2.25 .197 17.54 21.9 2.36 .52 .007

32 2.45 .680 86.32 37.1 7.49 2.78 .031

33 3.65 13.571 193.69 33.3 100.39 33.40 .046

34 2.55 .067 30.50 18.1 .71 .13 .010

35 2.85 .061 9.10 29.6 .58 .17 .003

36 3.35 .022 21.75 .4 .18 Tr. .006

Average I _ I I I _ 21.07 6.96 .018

TABLE 12. - Summary of channel-sampling results, tailing pile D, Deep Creek

Vol. in Conc. Gold Tin Recove ry per cuyd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

37 3.00 0.167 5.05 48.6 1.50 0.73 0.002

38 2.95 .515 125.64 46.7 4.71 2.20 .037

39 3.00 1.626 89.94 51.4 14.63 7.52 .026

40 2.45 .516 60.30 52.6 5.69 2.99 .021

41 3.05 1.302 130.62 52.4 11.52 6.04 .037

42 3.35 .682 33.84 51.6 5.50 2.84 .009

43 3.55 .190 12.86 43.9 1.44 .63 .003

Average 6.32 3.22 .019
47

TABLE 13. - Summary of channel-sampling results, tailing pile E, Deep Creek

Vol. in Conc. Gold Tin Recove y per cuyd.

Channel place, recovered, recovered, analyses, Conc. Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

44 2.60 0.062 0 39.9 0.65 0.26 0

45 2.65 .015 - .1 .15 Tr. 0

46 2.55 .055 0.42 .1 .59 Tr. 0.004

47 2.65 .016 0 .1 .16 Tr. 0

48 3.05 .022 0 .1 .20 Tr. 0

Average .34 .05 .001

TABLE 14. - Summary of channel-sampling results, tailing pile F, Deep Creek

Vol. in Conc. Gold Tin Recove ry per cuyd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

49 2.65 0.027 0 7.3 0.27 0.02 0

50 2.55 .046 15.31 .4 .48 Tr. 0.005

51 3.40 .110 76.98 7.8 .88 .07 .020

52 3.00 .093 16.26 6.9 .84 .06 .005

53 3.25 .164 3.49 4.9 1.36 .07 .001

54 3.30 .053 3.45 5.5 .44 .02 .001

55 2.63 .015 0 .4 .15 Tr. 0

56 1.95 .015 0 .2 .21 do. 0

Average I II__ .62 .03 .004

TABLE 15. - Summary of channel-sampling results, tailing pile G, Idaho Gulch

Vol. in Conc. Gold Tin Recovery per cu. d.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

57 1.52 0.100 49.34 34.4 1.77 0.61 0.028

58 1.70 .027 2.04 22.0 .43 .10 .001

59 1.90 .028 125.29 22.9 .40 .09 .057

60 1.90 .446 20.84 55.6 .63 .35 .010

61 2.00 .693 14.29 38.1 9.36 3.56 .006

Average I I _ 2.67 1.00 .020

TABLE 16. - Summary of channel-sampling results, tailing pile H, Woodchopper Creek

Vol. in Conc. Gold Tin Recove ry per cu yd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

62 2.40 0.026 92.64 15.8 0.29 0.05 0.034

63 3.38 .104 281.02 42.1 .83 .35 .072

64 3.30 .078 300.58 35.4 .64 .23 .067

65 3.88 .090 208.02 21.1 .63 .13 .047

66 3.20 .027 201.08 5.5 .20 .01 .055

67 3.20 .029 88.64 18.1 .24 .44 .024

68 2.85 .148 52.37 12.7 1.40 .18 .016

69 2.35 .016 59.06 3.0 .18 .01 .022

70 2.85 .511 138.77 50.4 4.84 2.44 .042

71 3.80 .031 172.78 23.7 .22 .05 .040

72 2.90 .022 117.92 8.8 .21 .02 .035

73 2.90 1.035 262.33 53.9 9.64 5.19 .079

Average __ 1.54 .72 .045
48

TABLE 17. - Summary of channel-sampling results, tailing pile I, Dalton Gulch

Vol. in Conc. Gold Tin Recovery per cuyd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

74 2.50 1.266 0 56.8 13.67 7.77 0

75 2.00 .024 31.41 19.6 .33 .06 0.014

76 2.45 2.964 2.64 29.7 32.66 9.70 .001

77. 2.45 .178 0 42.3 1.97 .83 0

78 2.40 .061 153.33 41.4 .69 .29 .056

Average 10.28 3.90 .014

TABLE 18. - Summary of channel-sampling results, tailing pile J. Cache Creek

Vol. in Conc. Gold Tin Recove y per cu- yd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

79 2.90 0.032 21.97 38.4 0.30 0.12 0.007

80 2.70 .145 7.31 37.1 1.45 .54 .002

81 2.45 1.401 273.39 55.7 15.44 8.60 .097

82 2.85 .148 15.46 43.9 1.40 .61 .005

Average 4.27 2.26 .025

TABLE 19. - Summary of channel-sampling results, tailing pile K, Harter Gulch

Vol. in Conc. Gold Tin Recover i per cuyd.

Channel place, recovered, recovered, analyses, Conc., Tin, Gold,

No. cu. ft. lb. mg. percent lb. lb. oz.

83 2.35 0.093 35.43 37.1 1.07 0.40 0.013

84 2.75 .034 9.24 15.2 .33 .05 .003

85 3.00 .104 0 35.8 .93 .33 0

86 2.65 .105 168.21 30.1 1.07 .32 .055

Average I .84 .27 .017

Mine Examinations

The Larsen drift mine on Deep Creek (Fig. 6) was the only underground mining

operation in the district that was active during the Bureau of Mines investigation.

The mine was examined by the Bureau engineer. Because of the similarity to many of

the early-day operations, the development and mining procedures employed at the

Larsen diggings are described briefly as follows:

The shaft was on a 6-inch churn-drill hole that had logged pay in placer gold.

A 3/8-inch open-end pipe or steam "sweater" was inserted to the bottom of the hole,

which had previously been drilled several feet into bedrock. Steam at 100 p.s.i.

boiler pressure was forced through the sweater to the bottom of the hole for a continuous period of approximately 4-1/2 days; the time for completing the thawing was

estimated on a thawing rate of approximately 1 hour per foot of muck and 45 minutes

per foot of gravel. When excavated, the shaft was 119 feet in depth and 6 feet in

diameter. The collar of the shaft was timbered, and the top 17 feet was cribbed;

frost prevented caving below the cribbing.
49

L-een /76 , ,_ 

* //e i'Sample

0 20 40 60

SC al e of fee t

Con/to ur in te rv ax- f eet

Figure 34. - Sample and topographic map, tailing pile A.
ajn

£ egenci 30~ ~~~~~~ e 3~5= Somp/eo

* 2fj 5amp/eX 0 20 40 60

0 *0 . 90 S a/e of feet

6ca/e of f ee t Contour inter va/-2 feet Con tour interval- 2 feet

Figure 35. - Sample and topographic map, tailing pile B. Figure 36. -Sample and topographic map, tailing pile C.

t (
L egend

* 43 = 5mp/e Legend

o C/raim corner , 48 Son p \pe

4 0~~~~~~~~~~~~~

0 d40 80 /20 \~~~~~~~~~~~a I _cale, of fe et

CoScle, of feet Contor 20 0 fee

t Contour J Intervcan-f feetee_

Figure 37. Sample and topographic map, tailing pile D. Figure 38. - Sample and topographic map, tailing pile E.

en
Legend .|L

w 5,5 = 5ample, Legend

40 Pond __ __

"-..=' Swamp * 5c-Sample (

! Shaft

a58

49

50 59

.-53 0

,54

s w \+ 0 S~~~~~~~~~~~~~~~~~~~~cle. of feet

/~ S. IL S0 S. //) :S) ~~~~~~~~~~~~~~~~~~~Confourlnferval-2ec

,J °/ 40 80 /200

SCleS of feeo

Contour Interval- 4 feet

Figure 39. - Sample and topographic map, tailing pile F. Figure 40. - Sample and topographic map, toiling pile G.
Leqend Leqend

*59= Xample U 7,5-6omp/e

,'°-62 6.V

70 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 7

0 2?0 40 60

0 60 /20 /80a

' *. | '_ i. ~~~~~~~~~~5 ca/e, of f e et

-5cole, of feet Cntour In terval- -5 feet

Col-iour lnterval--5 feet

Figure 41. - Sample and topographic map, tailing pile H. Figure 42. - Sample and topographic map, tailing pile 1.
L Leend

L egend * 83= Sample,

83 84

0 30 60 90 ________________ 0 20 0 6 0

5co/e, of feet

Contour Intervol- 4 feet 5co/e of feet Contour onterva/-3 feet

Figure 43. - Sample and topographic map, tailing pile J. Figure 44. - Sample and topographic map, tailing pile K.
55

Mining is done by an advancing room-and-pillar system; very little timber is

used. Wherever possible, mining is advanced up the slope of the bedrock, so that

natural drainage is toward the shaft sump. The gravel is thawed by driving steam

points and "sweaters" into the face. At this particular location about 3-1/2 feet

of gravel and bedrock is excavated and hoisted to the surface. Barren gravel

sloughs from the back and is shoveled into mined-out areas; as thawing continues,

enough barren gravel sloughs from the back to provide 5 to 6 feet of headroom near

9 the face. A 22-hp., wood-fired boiler provides steam for thawing and hoisting during mining and for pumping and elevating during washing.

A graphic section showing the thickness and types of material penetrated by

the Larsen shaft is given in figure 45.

Tin Reserves

Although the Bureau of Mines investigation was neither planned nor executed

to "block out" reserves, the tin production potential of the Tofty tin belt is

indicated roughly by the churn-drill prospecting information submitted by private

operators, by geologic inference, and by the data obtained from the tailingsampling program.

Firm estimates of reserves of tin in place (in unmined parts of the various

pay channels) cannot be made because the available information does not contain

data necessary for such calculations. Former mining and prospecting in the district were concerned with gold only; consequently little or no attention was given

to determining the tin content of the placer gravels. However, the volume of gravel

contained in unmined sections of placer deposits along Tofty and Idaho Gulches and

along Sullivan Creek may be approximated from prospect-drill data, as given in

tables 5 and 6 and as illustrated by figures 15 through 32. Geologic evidence indicates that unmined tin-bearing placer deposits of equal or greater volume than

those mentioned above exist in the Deep Creek-Woodchopper Creek areas (fig. 3);

further prospecting may greatly extend Lhe limits of the tin-bearing placers as

now known.

The tin content of the unmined gravels in the various areas throughout the

length of the belt may be roughly approximated from tailing samples taken from wash

dumps in those areas. The tin content of such samples ranged from an average of

0.24 pound per cubic yard of tailing in the Sullivan Creek open pit (as determined

by Thorne and Wright].) to as much as an average of 2.77 pounds per cubic yard of

tailings in 4 drift mine dumps on Deep Creek (figs. 11-14, inclusive).

The tailing piles sampled were selected as being fairly representative of all

the tailing in a particular area and therefore are considered to be roughly representative of the tin content of unsampled piles in that area. By transit surveys,

b visual estimates, and aerial surveys (including aerial photographs), the ratio of

the volume of tailing sampled to the total volume of tailing available for re-treatment can be determined within reasonable limits of accuracy. Applying such a factor, it is estimated that drift-mine and opencut tailing throughout the length of

the tin belt constitute an "inferred" reserve of 733,000 pounds of tin contained in

1,259,000 cubic yards of gravel; the tailings may also contain as much as 17,700

ounces of gold, as well as small amounts of columbium-tantalum oxides.

The tailings are fairly accessible, and the cassiterite and other heavy minerals can be recovered by conventional gravity methods of separation. Because of the

comparatively small size of the individual dumps, a highly portable washing plant

would be an important factor in economic recovery of the heavy minerals.

7/ Work cited in footnote 2, p. 4.
/1 \ ~~~~~~~~~~E/e, vcf/on

Froz e,7 5//ft with ice /enses

F rozen si/ft witr sond and fine qi-ave!

2 F~~~~~~~~~~~ozen w'ecft/eredph,-1y//ife bedr-ocA

0 20 40o 00

-~~ 4 .,~~~~~~~~~~~~~~~~~~~~ >t Ol, f;ee7

--. ~ ~~~igr 45 - Crs sectionf through/ondsend t shaft Dep rek