UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall. Director

Bulletin 931-L

TIN DEPOSITS OF

NORTHERN LANDER COUNTY

NEVADA

BY

CARL FRIES, JR.

Strategic Minerals Investigations, 1941 

(Pages 279 -294)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1942

For sale by the Superintendent of Documents, Washington, D. C. -------- Price 20 cents

CONTENTS

Page

Abstract.................................................. 279

Introduction.............................................. 279

Geology................................................... 282

Porphyritic rhyolite.................................. 282

Basalt................................................ 285

Alluvium.............................................. 285

Tin depos its.............................................. 285

Veinlets in bedrock................................... 285

Distribution...................................... 285

General character................................. 286

Mineral and chemical composition.................. 287

Origin............................................. 288

Prospect pits..................................... 289

Outlook........................................... 291

Placers............................................... 293

ILLUSTRATIONS

Page

Plate 48. Topographic and geologic map of the principal 

part of the tin-bearing area in northern 

Lander County, Nevada........................ 282

Figure 26. Index map of Nevada showing location of tin

deposits..................................... 281

27. Plan and section of the incline shaft.......... 289

28. Plan and section of the east shaft............. 291

III

TIN DEPOSITS OF NORTHERN LANDER COUNTY, NEVADA

By Carl Fries, Jr.

ABSTRACT

Tin-bearing veinlets are exposed in a small area near Izenhood Ranch, 22 miles north of Battle Mountain, Nev. They occur 

in thick rhyolitlc flows of Miocene (?) age, and wood tin, found 

in the gravels of arroyoa that head in the surrounding rhyolite, 

presumably comes from other veinlets not yet discovered. The 

exposed veinlets are about 20 feet in maximum length and a quarter of an inch in average thickness. Parallel and reticulating 

veinlets form lodes 4 to 6 feet thick and 15 or 20 feet long. 

Virtually no cassiterite is disseminated in the wall rock.

The veinlets contain specularite, cassiterite, sanidine, andradite, cristoballte, tridymite, quartz, chalcedony, fluorite, 

and opal. All these minerals, except possibly cassiterite, together with topaz and pseudobrookite, are likewise present in 

cavities that are widely distributed in the rhyolite The similarity of the mineral assemblage in the veinlets to that in the 

cavities indicates that the tin originated in the rhyolite magma, 

and spectrographic analyses indicate that the average rhyolite 

contains about 0.001 percent of tin. It is therefore believed 

that the incrustations were deposited in fumarolic vents along 

fissures formed by differential contraction during the cooling 

of the lavas.

There is no record of any production of tin from the area. 

Possibly a few tons of the metal might be produced from the exposed veinlets by narrow stoping and hand sorting. No large 

body of rock in the area, however, contains even 0.2 of a pound 

of tin to the ton; and the amount of tin recoverable would be 

only a small part of that shown by assay, for not all of the tin 

is in grains of cassiterite large enough to be concentrated by 

ordinary methods.

Placer deposits of commercial grade occur in small draws 

that head in the area where the veinlets are exposed, but as 

they are only a few inches thick and of small volume, they could 

yield only a few tons of cassiterite. There is a large area of 

alluvium in the valley bottom.below the tin-bearing veinlets 

that has not been thoroughly sampled, but a few tests indicate 

that the tin content of the upper 40 feet is less than 0.1 of a 

pound to the cubic yard.

INTRODUCTION

Tin-bearing veinlets occur in rhyolite at the northern end 

of the Sheep Creek Range in northern Lander County, Nevada

279
280 STRATEGIC MINERALS INVESTIGATIONS, 1941

(fig. 26). The tin-bearing area is at the base of a low ridge 

about half a mile' north of the Izenhood ranch and spring, which 

are 22 miles by narrow dirt road north of Battle Mountain, a 

town on the main highway from Salt Lake City to Reno'and on the 

Southern Pacific-and Western Pacific Railroads. There is no 

record of any production of tin from the area. The principal 

claims were owned in 1940 by Mrs. R. R. Gamble and associates, 

of Battle Mountain.

The deposits were described by Adolph Knopf -'In 1916, only

2/ 2 years after their discovery, and W. 0. Vanderburg 'visited

the area for the Bureau of Mines in 1938 Little new exploratory work has been done on the deposits since 1916: the depth 

of the shaft on the old Mayflower claim has been increased from 

10 to 50 feet, several shallow pits have been dug as assessment 

work, and some exploratory shafts as deep as 40 feet have been 

put down into the alluvium bordering the main ridge.

The deposits are similar to the tin deposits in the Black 

Range in New Mexico, which were studied in detail by the Geological Survey in 1939 and 1940 and explored by the Bureau of Mines

3/ in 1939, and preliminary accounts of which have been published.

The area is roughly rectangular, extending about 2 miles 'from 

north to south and 3t=r miles from east to west. Only the more 

important part was mapped In detail. The writer, assisted by 

A. P. Butler, Jr., spent 3 weeks in the tin-bearing area in late 

July and early August 1940. The topography and geology of the 

area were mapped with telescopic alidade and plane table. Specimens of rhyolite, six channel samples across tin-bearing lodes 

and a dozen pannings of stream gravel were collected. Laboratory

I/ Knopf, Adolph, Tin ore in northern Lender County, Nevada; U. S. 

Seol. Survey Bull. 6UO-C, pp. 125-138, 1916.

?/ YandertUTg, ft, 0M Reconnaissance of mining districts in Lender 

County, Nevada: U. S. Bur. Mines Inf. Circ. 70^3, pp. 5^-57, IfobrUflry 1939.

2/ Pries, Carl, Jr., Tin deposits of the Black Range, Catron and Sierra 

Counties, N. Mex., a preliminary report: U. S. Geol. Survey Bull. 922-M, 

PP. 355-370, 19HO.

Strategic minerals investigations, progress report on exploration of 

tin deposits: U. S. Bur. Mines Inf. Circ. 715U, pp. U-5, March
TIN DEPOSITS OP NORTHERN LANDER COUNTY, NEVADA 281

Figure 26. Index map of Nevada showing location of tin deposits.
282 STRATEGIC MINERALS INVESTIGATIONS, 1941

studies were made by the writer and Miss J. J. Glass of the Geological Survey. Owing to the scarcity of cassiterite in the 

samples, heavy minerals were concentrated from crushed rock with 

heavy liquids and examined microscopically. Quantitative spectrographic assays for tin were made of some of the concentrates.

Thanks are due Mrs. R. R. Gamble of Battle Mountain and Mr. 

P. S. Crocker of Dayton, Nevada, for information on sampling in 

the placer area. Many helpful suggestions and criticisms were 

contributed by H. G. Ferguson, P. C. Calkins, and Ward C. Smith, 

of the Geological Survey, during the preparation of this report.

GEOLOGY 

Porphyritic rhyolite

The oldest formation, in which all the tin-bearing veinlets 

occur, is a coarsely porphyritic rhyolite, light gray to pink in 

fresh exposures and dark gray to brown where weathered. The 

thickness of rhyolite exposed is about 200 feet, but the base is 

not exposed. The formation probably includes several flows, for 

in many places it contains masses of flow breccia, lithophysal 

structures, and zones in which the matrix is black glass. Continuous primary layering In the high ridge above the incline 

shaft (see pi. 48) indicates that one flow of rhyolite is more

than 500 feet thick. No interbedded tuffs are present in the

i/ area examined. The age of the rhyolite is probably Miocene.

Primary flow layering is well-developed in many parts of the 

rhyolite. The layers are highly irregular in strike and dip; at 

many places the dip changes within a short distance from nearly 

horizontal to vertical. Owing to the small extent of the area 

studied and the lack of continuous exposures, it was not possible to work out the structure of the flows in detail, The apU/ Emmon3, V. H., A reconnaissance of some mining camps in Elko, Lander, 

and Eureka Counties, Nev.: U. S. Ceol. Survey Bull. UOS, p. 35, 1910.
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parently confused structure is largely due to the high viscosity 

of the lavas at the time of extrusion.

The rhyolite is fairly uniform in composition throughout the 

area mapped. Phenocrysts of quartz, oligoclase, and potash 

feldspar, dominantly sanidine, make up from 25 to 35 percent of 

the rock. The rock contains a few microscopic aggregates of 

hematite dust, quartz, and feldspar; probably some of these represent biotite and others hornblende. The ground mass is a microcrystalline aggregate of feldspar, quartz, and chalcedony. 

The accessory minerals include magnetite, hematite, zircon, apatite, and sphene. Vesicles or lithophysae are present everywhere, although the rock is in general fairly dense. The minerals most abundant in the cavities are quartz and chalcedony, and 

specularite, topaz, pseudobrookite, and fluorite are somewhat 

less abundant. Sanidine, garnet, tridymlte, cristobalite, opal, 

and possibly cassiterlte occur in cavities in a few places.

A partial chemical analysis of the normal rhyolite given by 

Knopf ' shows:

SiOp............. 76.25

K9 Q.............. 5.18

NaoO............. 4.05

CaO.............. 0.44

Spectrograms of lithophysal rhyolite and of average rhyolite 

show, in addition to the ordinary rock-forming elements and iron, 

between 0.2 and 0 0 001 percent each of titanium, manganese, zirconium, barium, copper, zinc, tin, and vanadium. Fluorine, 

which is not recorded on the spectrograms, probably is present 

in similar quantity. Strontium, molybdenum, lead, boron, gallium, chromium, nickel, and cobalt are present in quantities between 0.001 and 0.0001 percent. There is a trace of silver. ' 

Arsenic is absent, and sulphur appears to be absent.

The greater part of the rhyolite is unaltered. In some 

places both quartz and sanidine crystals show minor enlargement.

Knopf, Adolph, op. clt., p. 128.
284 STRATEGIC MINERALS INVESTIGATIONS, 1941

The feldspars show internal change only at the present erosion 

surface, where fractures in the crystals are filled with caliche. 

Red and brown iron stain is present in rock adjacent to fractures in the northeastern part of the area. Chalcedony and opal 

partly fill the cavities in the ground mass of the rhyolite on 

the upland bench below the high ridge, as indicated on plate 48. 

It seems probable that the deposition of the silica was related 

to an old erosion or contact surface, as the quantity of silica 

is greatest around small remnants of the overlying basalt, and 

as the rhyolite in the small draws that head in this area does 

not contain such secondary silica.

Some parts of the veinlets in the incline shaft at the west' 

end of the area mapped (see pi. 48) are almost completely filled 

with chalcedony and opal, which have also partly replaced the 

ground mass of the rhyolite of the walls for half an inch. The 

silicification of the wall rock extends only about 10 feet below 

the surface. The veinlets appear to be composed of angular 

fragments of vein material and wall rock cemented by silica. 

Microscopic examination of a veinlet further shows that deposition of the silica began as an incrustation on the walls of an 

open fissure and on its loosely held angular filling. The present surface at the shaft is possibly no more than 10 feet below 

an erosion surface that was overlain by basalt, of which a few 

patches remain. In view of the marked increase in the quantity 

of chalcedony in the rhyolite near the contact surface, it is

probable that the silica in the veinlets is similar in origin to 

that in the body of the rock.

There are no areas of porous leached rock, suck ftS th096 111

* 6/ the Black Range tin deposits in New Mexico.-^

Fries. Carl, Jr.. op. cit.. p. 36!.
TIN DEPOSITS OP NORTHERN LANDER COUNTY, NEVADA 285 

Basalt

The rhyolite is unconformably overlain by nearly horizontal 

flows of basalt (pi. 48). There are six small remnants of basalt in the vicinity of the incline shaft near the northwest 

corner of the area mapped, and a larger patch near the valley 

bottom in the southern part of the area. It covers the upland 

bench west of the incline shaft and is the dominant rock in the 

Sheep Creek Range, south of the area mapped. The basalt must

have flowed over an erosion surface of strong relief. It is

7/ possibly Pleistocene in age.

Alluvium

The alluvium In the valley bottom at the south edge of the> 

area mapped is composed .of poorly sorted rhyolitic and basaltic 

material with boulders varying in size up to as much as 4 feet 

in diameter. Pits have been sunk as. deep as 40 feet without 

reaching bedrock.

TIN DEPOSITS 

Veinlets in bedrock

Distribution.--Gassiterite (SnOo) occurs at eight places in 

an east-trending belt about 2 miles long and half a mile wide. 

Distinct veinlets were found at only four of these places. (See 

plate 48.) A small prospect cut shown at the southwest edge .of 

the map also contains cassiterite. A pit, located on a hillside 

about a mile east of the east shaft but not included in the area 

mapped, exposes a veinlet. The veinlets probably have a wider 

distribution than is shown by the'se prospects, for cassiterite 

is found by panning in arroyos that head on the north side of 

the high ridge shown in plate 48. As cassiterite is also found

Personal communication from E. 0. fferguaon 'of the Geological Survey.
286 STRATEGIC MINERALS INVESTIGATIONS, 1941

in arroyos heading on a ridge southeast of the area mapped, 

veinlets probably occur in the watershed of these arroyos.

General character. The veinlets have a characteristic open 

texture and might be described as incrustations on the walls of 

fissures. The thickness of the incrustations is variable, averaging about a quarter of an inch. It is reported that pieces of 

vein material as thick as 6 inches have been found, but such 

bodies are apparently pod-shaped and at most only a few feet 

long. The incrustations are not limited at all places to a single fissure, but follow some of the cross and parallel fractures 

as well. At one place, where the rhyolite is broken into small 

blocks, some of the blocks are almost completely incrusted. 

Lodes from 4 to 6 feet thick that contain several nearly parallel or reticulated veinlets occur, but none were seen to extend 

for more than 20 feet either vertically or horizontally. It is 

possible that the vein material might appear again beyond a barren section, as some of the fissures continue beyond the incrusted sections. Although cassiterite has penetrated the wall 

rock as much as half an inch in a few places, in general it was 

not deposited in the walls, none of it being found in heavy-mineral concentrates of samples 'from which the incrusting material 

was cobbed off.

The fissures that contain the veinlets are generally erratic 

in strike and have steep dips. Measurements of the average 

strike of four tin-bearing fissures gave: N. 80° W., N. 35° E., 

N. 50° E., and N* 85° W. Irregularity in strike and dip along 

the individual fissures is so great that no appreciable movement 

could have taken place without strong brecciation of the walls.

There is no such brecciation along any of the exposed fissures 

that carry vein material. Closely spaced, nearly parallel fractures and broken rock near the bottom of the incline shaft suggest faulting, but the movement was not along the tin-bearing 

fissures. Slickensides have not been found in the area mapped.
TIN DEPOSITS OP NORTHERN LANDER COUNTY, NEVADA 287

Mineral and chemical composition. The incrustations are 

largely specularite and cassiterite. In some places cassiterite 

is nearly or entirely absent, but specularite is present everywhere. The greater part of the cassiterite was deposited on and 

around specularite, but the minerals are intergrown so intimately that they appear to have been deposited at essentially the 

same time. The cassiterite forms tiny red, pale-yellow, or dark 

yellow-brown crystals, and botryoidal masses known as wood tin. 

The brown crystals appear almost black and are easily mistaken 

for specularite. The wood tin ranges in color from nearly white 

through all shades of yellow and red brown to dark brownish 

black. A spectrogram of a few small pieces of wood tin that 

were picked out of a veinlet in one of the prospect pits near 

the center of the area mapped shows, in addition to tin and iron, 

small quantities of manganese, lead, antimony, tungsten, and 

zinc. The specularite is all in well-formed, splendent, black, 

platy or bladed crystals, some of which are corroded and partly 

replaced by cassiterite. Analyses indicate that the specularite 

contains small quantities of tin either as a part of the mineral 

or as submlcroscopic grains of cassiterite which cannot be identified under the microscope.

Although much of the cassiterite and specularite is not 

coated with later minerals, both have been incrusted in some 

places with cristobalite, tridymite, sanidine, quartz, chalcedony (Including the variety known as lussatite), opal, and fluorite. Sanidine, cristobalite, and tridymite appear to be relatively more abundant in the tin-bearing fissures than in the 

cavities in the rhyolite, but the other minerals named, and 

specularite, are rather evenly and widely distributed throughout 

the rhyolite. Small grains of a zeolite attached to vein material in the east shaft appear to have been formed by pseudomorphic replacement of the incrusting sanidine. Vertical planes of 

parting parallel to the primary flow layering in the prospect
288 STRATEGIC MINERALS INVESTIGATIONS, 1941

pit near the southwest corner of the map (see pi. 48) are sparingly studded with brown crystals of andradite garnet. Heavymineral concentrates of small pieces of rock from here with attached garnet also contain a little cassiterite. Andradite garnet incrusting cassiterite occurs in a velnlet in the Black 

Range of New Mexico.

Heavy-mineral concentrates of two channel samples taken 

across veinlets in the incline shaft (see fig. 27) contain hematite, zircon, topaz, fluorite, pseudobrookite, apatite, cassiterite, and sphene. Spectrograms show that the only essential 

chemical difference between these samples and those of the average rhyolite is in the relative quantity of tin, which is about 

10 times as great in these channel samples as in the rhyolite.

The wall rock adjacent to most of the veinlets is wholly unaltered.

Origin. There is little doubt that the cassiterite was deposited before the extrusion of the basalt, since the veinlets 

in the incline shaft appear to have been eroded before the basalt was extruded. No veinlets, moreover, have been found in 

the basalt, and no placer tin has been found that could be derived from bodies Of basalt in tile area mapped, or- fx-om. la.r»ge:r»

bodies in the vicinity. The source of the vein material appears 

to have been the rhyolite, for spectrograms show that the chemical elements in and near the veinlets are the same as those in 

the average rhyolite, which contains about 0.001 percent of tin. 

The mineralogy of the veinlets is similar to that of the vesicle 

fillings in the average rhyolite. These similarities and the 

absence Of SUlfide minerals indicate that the fissures had no 

deep connections.

It is believed that the cassiterite-bearing incrustations 

were deposited along the walls of fumarolic vents which probably 

were not major breaks. Such an origin is suggested by the discontinuity and the extreme irregularity in strike and dip of the
TIN DEPOSITS OP NORTHERN LANDER COUNTY, NEVADA 289

individual fissures, and by the absence of brecciatign and detectable faulting along them. It is probable that most of the 

fissures were formed by differential contraction during the 

cooling of the solidified lavas, though some of them may have 

resulted from minor adjustments in the basement rocks.after extrusion of the lavaso

Prospect pits, The incline shaft near the northwest corner

8/ of the map (see pi. 48 and fig. 27) is 45 feet deep -'but is

Prospect trench 

No cassiterite visible

Contains blocks 

incrusted with 

cassiterite. No 

veinlets visible

 Fractures incrusted with 

cassiterite and specularite

Channel sample on east wall 

contains 0.003 percent tin'

 Channel sample on west wall 

contains 0.02 percent tin

 Channel sample on east wall 

contains 0.005 percent tin

 Channel sample on west wall 

contains 0.002 percent tin

Zone of irregular fractures

Note: All rock is porphyritic rhyolite 

30 Feet

SECTION 

10 55 0 10 20 

Contour interval lOfeet

Figure 27. Plan and section of the Incline shaft.

g/ Khopf, Adolph, op. cit., p. 130.
290 STRATEGIC MINERALS INVESTIGATIONS, 1941

filled for 10 feet with rubble. The shaft follows.the dip of 

four nearly parallel veInlets. Three of the veinlets pinch out 

in the first 10 feet, and the remaining one ends at about 15

feet. At 25 feet there is a zone of broken rhyolite which

9/ 

Rnopf regarded as marking a normal fault; the absence of

slickensides and breccia, however, indicates that the movement 

was slight. As the veinlets die out before they reach the broken zone, their disappearance cannot be attributed to faulting. 

The veinlets cannot be traced on the surface for more than a few 

feet from the shaft. Two prospect pits on either side of the 

shaft show no vein material. The dump of one of the pits north 

of the shaft contains a few blocks that are incrusted with vein 

material, but the veinlets could not be found in place.

Grab channel samples weighing about 3 pounds each were taken 

at four places across the walls of the shaft. Quantitative 

spectrographic analyses of heavy-mineral concentrates from the 

crushed samples indicate that the tin content ranges between 

0.02 and 0.002 percent. The decrease in tin content from the 

top of the shaft downward is shown in figure 27. From the analyses and the length of the veinlets visible, it is estimated 

that about 5 tons of ore containing 10 percent of tin could be 

obtained by narrow stoping and hand sorting.

The east shaft, shown hear the northeast corner of plate 48

10/ and in figure 28, is said to be 50 feet deep but is filled

for 20 feet with rubble. It was not possible to examine the upper part closely, but some small irregular veinlets, which appear to strike nearly west, are visible in the southwest corner; 

they disappear at a depth of 15 feet. The veinlets cannot be

traced on the surface away from the shaft. Vertical primary 

flOW layering having a strike of N. 15° W. is conspicuous at

2/ Knopf, Adolph, op. cit., p. 130. 

10/ Vandertourg, W. 0., op. cit., p. 55.
TIN DEPOSITS OF NORTHERN LANDER COUNTY, NEVADA 291

the shaft. No veinlets or vein material were found in the small 

cut south of the shaft or in the rock excavated from it.

Small grab channel samples were taken across the north and 

east walls of the shaft 25 feet below the surface. Quantitative 

spectrographic analyses show 0.01 percent of tin across the 

north wall and 0.005 percent across the east wall. A few thousand pounds of ore containing 10 percent of tin might be mined 

from the shaft by narrow stoping and hand sorting.

 ix Open cut Primary layering 

A_____^f: >niiiiiiMiiiii,iiiiiinm_____T/KNo cassiterite visible

Close fractures

PLAN

Specularite and cassiterite incrustations

Note: All rock is porphyritic rhyolite

,- Channel sample on east wall 

\ contains 0.005 percent tin 

s»o|i ^Channel sample on north wall 

 contains 0.01 percent tin

10 5 0

Figure 28. Plan and section of the east shaft.

Two small prospect pits just north of the center of the 

mapped area have veinlets exposed in their walls. The wall of a 

nearly vertical northeast-trending fissure in the south pit is 

thinly Incrusted; the vein material could not be traced on the 

surface. An incrusted, nearly vertical fissure wall is exposed 

in the north pit; the vein material appears to continue for at 

least 10 feet southwest on the surface. Possibly a few thousand 

pounds of ore containing 10 percent of tin might be mined from 

these pits.

Outlook, Selective mining of the tin-bearing veinlets would 

not pay, owing, to their narrowness and discontinuity. None of
292 STRATEGIC MINERALS INVESTIGATIONS, 1941

the veinlets exposed are more than 20 feet long. Although vein 

material may again appear along a fissure beyond a barren section, it is improbable that any individual deposit would extend 

even intermittently for more than a few hundred feet either vertically or horizontally. The maximum vertical extent of a deposit would be limited by the thickness of the rhyolitic lava 

and by other physical factors affecting deposition. Veins of 

this type have been mined in Mexico by hand stoping, but there 

one kilogram of concentrates containing from 25 to 50 percent of 

tin (worth from 30 to 50 cents United States currency in 1940), 

washed from ore containing from 3 to 10 percent of tin, is considered a satisfactory recovery for one man in a day. No vein 

in deposits of this type in Mexico or New Mexico has yet been 

proved large enough to be mined profitably by machine methods. 

In view of the exploratory work that has been done by the Bureau 

of Mines on the deposits in New Mexico 'and the brief examination by the writer of many of the Mexican deposits, it seems 

certain that only a few tons of ore containing 10 percent of tin 

could be produced from any one veinlet by selective mining, disregarding cost of production.

It seems equally certain that the deposits could not be 

mined by bulk methods. Any large body of ore in this area would

consist of rhyollte in which veinlets were closely spaced or in 

which cassiterite was more abundantly disseminated than it has

anywhere teen observed. The largest Dodles of even potential

ore exposed are lodes 4 to 6 feet thick, made up of veinlets

that are no more than 20 feet long. It is doubtful whether

these lodes would average 0.1 percent of tin, judging from six 

3-pound channel samples ranging from 0.02 to 0.002 percent of

tin, each taken across 4 or 5 feet of two of the lodes. Heavymineral concentrates of samples taken from what appear to be the

ll/ Strategic minerals investigations, op. cit.
TIN DEPOSITS OP NORTHERN LANDER COUNTY, NEVADA 293

moat favorable places indicate that no appreciable quantity of 

cassiterite is disseminated in the rhyolite, except very close 

to some of the veinlets. The amount of tin recoverable from the 

rhyolite, moreover, would be only a part of the small quantity 

present, for not all of the tin is in cassiterite that could be 

concentrated by ordinary methods. Some of the tin appears to be 

in the specularite either as a part of the mineral or as submlcroscopic grains of cassiterite, and loss of tin is high In 

smelting concentrates that contain much iron.

Placers

All the small draws that drain the rhyolite in the area 

mapped carry a little cassiterite, particularly the three large 

draws on the east side and the large draw on the west side. 

(See plate 48.) Possibly a few tons of cassiterite could be 

economically recovered from these thin deposits of gravel f which 

are largely in pockets in bedrock and of-very small volume.

The alluvium at the base of the ridge appears to be the most 

favorable large area of placer ground, for it was derived mainly 

from the rhyolite that contains the cassiterlte-bearing veinlets. 

No extensive detailed sampling of the alluvium has been done, 

but panning °by the writer of material excavated from the prospect pits shown on the map Indicates that the percentage of cassiterite is very small. The people who dug some of the pits report that the quantity of cassiterite is negligible. The tin 

content of the gravels to the depth of sampling appears to be 

less than 0.1 of a pound to the cubic yard.

. The alluvium apparently accumulated under conditions that

were not favorable to concentration of the cassiterite. Materi12/ al excavated from two shafts, each 40 feet deep 'and entirely

in alluvium, consists of sand and medium-sized gravel much finer

12/ Vanderburg, Iff. 0., op. cit., p. 56.
294 STRATEGIC MINERALS INVESTIGATIONS, 1941

than that in the alluvium dissected and exposed in small draws 

closer to the ridge north of the shafts. The alluvium probably 

was transported during short, heavy rain storms and deposited 

with little sorting, so that there was no thorough separation of 

materials into layers. Cassiterite may, however, have been 

slightly concentrated at several horizons in the deposit, and 

the deeper unexplored gravels in the valley bottom may have accumulated under different climatic conditions more favorable to 

placer concentration.

Inasmuch as the deep shafts in the alluvium struck the water 

table, it appears that there would be a plentiful supply of water for placer operation.

O