UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Bulletin 931-1

NICKEL DEPOSIT NEAR RIDDLE 

DOUGLAS COUNTY, OREGON

BY

WILLIAM T. PECORA

AND

S. WARREN HOBBS

Strategic Minerals Investigations, 1941 

(Pages 205-226)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1942

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

CONTENTS

Page

Abstract.................................................. 205

Introduction.............................................. 205

History and development............................... 206

Field work and previous Investigations................ 207

Topography............................................ 208

Geology................................................... 208

PeridotIte............................................ 209

Serpentine............................................ 210

The nickel deposit........................................ 211

Mineralogy............................................ 212

Garnierlte........................................ 212

Enriched garnierlte............................... 213

Quartz............................................ 214

Llmonlte.......................................... 214

Layers of the deposit................................. 214

Brick-red soil layer.............................. 214

Quartz-garnlerite boxwork layer................... 217

Boxwork veins................................. 217

Fracture veins................................ 219

Root layer........................................ 220

Origin................................................ 221

Relation to slopes................................ 221

Formation of boxwork................ .............. 223

Reserves.............................................. 224

Grade............................................. 224

Estimates of tonnage.............................. 225

ILLUSTRATIONS

Page

Plate 37. Geologic map of the vicinity of Nickel Mountain, Douglas County, Oregon................. 208

38. Topographic and geologic map of the nickel deposit near Riddle, Douglas County, Oregon.... 208

Figure 20. Index map showing location of the Riddle nickel deposit................................... 206

21. Diagrammatic sketch of a vertical section of 

the mineral deposit at the Discovery workIngs ......................................... 215

22. Composite and schematic profile of the.southeast side of Nickel Mountain and the adjacent area, showing relationship of ore to 

topography................................... 222

NICKEL DEPOSIT NEAR RIDDLE, 

DOUGLAS COUNTY, OREGON

By William T. Pecora and S. Warren Hobbs

ABSTRACT

The Riddle nickel deposit, on the slopes of Nickel Mountain 

about 5 miles northwest of Riddle, Douglas County, Oreg., was 

discovered in 1864. Since then much prospecting and preliminary 

development work has been done, but no ore has been shipped except small lots used for metallurgical tests.

The deposit is a layered blanket, containing the nickel silicate garnierite, which rests upon unserpentinized peridotite. 

This blanket'ranges in thickness from a few feet to a maximum of 

60 or 70, but with an average of about 20 feet. It is best developed on terraces, flats, and gentle mountain slopes above an 

elevation of 2,000 feet. It consists of three layers, a top 

brick-red soil layer, an intermediate thick yellow limonitic 

layer with some quartz.-garnierlte boxwork, and a root layer composed of quartz-garnierite boxwork in nearly fresh bedrock that 

is a transitional phase between weathered material and fresh 

peridotite. The disposition of the boxwork veins was controlled 

by original blocky jointing in the peridotite. Nickel occurs in 

all three layers of the blanket but is most abundant in the boxwork veins carrying garnierite. The darker green varieties of 

the garnierite contain the highest percentage of nickel.

The nickel is believed to have been derived from olivine in 

the peridotite by decomposition during lateritic weathering, 

which probably took place during late Tertiary time, before the 

present regional surface at an elevation of 2,000 feet was dissected. This process formed limonite and nickel-poor garnierite. 

Under present climatic conditions the original laterite has undergone a.change resulting chiefly in a boxwork of quartz and 

nickel-rich garnierite.

About 162 acres of ground are underlain by a blanket containing over 6,000,000 tons of material, 1 to 2 percent of which 

is probably nickel. Eighty thousand tons have been proved to 

contain 2 to 3 percent of nickel, and 75,000 tons have been 

proved to contain 1 to 2 percent of nickel. A new method of 

treating low-grade silicate material would have to be devised 

before this large deposit could be utilized.

INTRODUCTION

The Riddle nickel deposit is on Nickel Mountain, also called 

Plney Mountain, about 5 miles northwest of Riddle, Douglas

205
206 STRATEGIC MINERALS INVESTIGATIONS, 1941

County, Oreg. (fig. 20). The deposit is an unevenly distributed, 

surficial blanket, containing the nickel silicate garnierite, 

which rests upon peridotitic rocks on the western, southern, and 

southeastern slopes of the mountain above an elevation of 2,000 

feet.

324° 123 122° 17L" 118° 117°

121° 123°

Figure 20.~Inder map showing location of the Riddle nickel deposit.

Riddle, which has a population of about 200, is at an elevation of about 700 feet on the north side of Cow Creek a mile 

west of its junction with the South Umpqua River. It is on the 

Southern Pacific Railroad, and it is about 230 miles by highway 

south of Portland. A poorly conditioned dirt road about 5 miles 

long connects the town with the nickel deposit.

History and development

Since the discovery of the deposit by sheepherders in 1864, 

much prospecting and exploration has been done on NickSl Mountain, but up to the present no nickel o,re has been shipped ex-
NICKEL DEPOSIT NEAR RIDDLE, OREGON 207

cept small lots used for experimental metallurgical tests. Prom 

1880 to 1900, Mr. W. Q. Brown of Riddle owned a large portion of 

the deposit, and under his direction it was actively explored. 

Mr. Brown also experimented with concentration and treatment of 

the ore. The property that contains most of the deposit is now 

owned "by Mr. Edson F. Adams of Oakland, Calif.

The accessible workings include 75 small pits and trenches, 

6 adits, 3 shafts, and about 5 large open cuts. The longest 

adit is 300 feet long and the deepest shaft is 83 feet deep. 

The dump piles contain about 4,000 tons of material practically 

all that has been excavated from the workings in which the 

nickel content ranges from 1/2 to 3 percent. If garnierite ore 

of this low grade could be successfully concentrated or treated, 

there would be a huge potential reserve of nickel in the deposit. 

Mining of the deposit would involve no unusual problems; the 

principal obstacle to operation is the difficulty of profitably 

treating such low-grade ore.

Field work and previous investigations

During September and October 1940, the writers made a detailed study of the mode of occurrence of the nickel and prepared a map of the deposit. The geology of the Riddle quadrangle, in which the deposit is situated, has been described by

Diller and Kay, and the nickel deposit has been described by

2/ 3/ 4/ 5/ 6/ Clarke, Von Poullon,-^ Austin, Ledoux,-' and Kay.

I/ Diller, J. S., and Kay, G. F., U. S. Geol. Survey Ceol. Atlas, Riddle 

folio (No. 218), 1924.

2/ Clarke, F. W., Some nickel ores from Oregon: Am. Jour. Sci., 3d ser., 

vol. 35, pp. 4g3-4gg, Iggg; U. S. Geol. Survey Bull. 60, pp. 21-26, Ig90.

2/ 7on Foul Ion, E. B., On Riddle, Oregon: K. K. Geologische Relchsanstalt, Jahrb., vol. 42, pp. 224-234, Vienna, Ig92.

4/ Austin, ft. L., The nickel deposits near Riddle's, Oregon: Colorado 

Sci. Soc. Proc., vol. 5, pp. 173-196, Ig96.

^/ Ledoux, A. R., Notes on Oregon nickel prospects: Canadian Min. Inst. 

Jour., vol. 4, pp. Ig4-lg9, 1901.

6/ Kay, G. F., Nickel deposits of Nickel Mountain, Oregon: U. S. Geol. 

Survey Bull. 315, pp. 120-12g, 1906.
208 STRATEGIC MINERALS INVESTIGATIONS, 1941

The authors are Indebted to F. C. Calkins and H. G. Ferguson, 

of the Geological Survey, for many helpful suggestions during 

the preparation of this report. The chemical analyses were made 

by Victor North, also of the Geological Survey.

Topography

The topography of the Riddle quadrangle is typical of a 

large part of the Pacific Coast Ranges. The relief is about 

3,000 feet. The summit of Nickel Mountain has an altitude of 

3,533 feet and rises a few hundred feet above the neighboring

ridges. The ridge crests are fairly uniform in altitude and

7/

were believed by Diller -1 to represent the widespread Klamath

peneplain of late Tertiary age. Dissected erosion surfaces, the 

chief of which has an elevation of about 2,000 feet, are also 

recognizable at lower altitudes. In a detailed analysis of the 

topography of Nickel Mountain, given in a later section, the 

distribution of the ore is correlated with the topography. The 

physiographic history of the region has been an important factor 

in the formation and localization of the nickel deposit.

GEOLOGY

The areal distribution of the rocks in the vicinity of Nick-

§/ el Mountain is shown on plate 37. A large irregular body of

peridotite and serpentine, which extends northeast and southwest 

from Nickel Mountain, is of principal interest, because the 

nickel deposits are related to the peridotite. The peridotite 

and serpentine body is intrusive into Jurassic sandstone and 

late Jurassic greenstone and related rocks, and is probably late 

Jurassic. The structure of these older rocks has a predominant 

northeasterly trend. They are unconformably overlain by the 

Knoxville formation and younger sedimentary rocks.

jj Diller, J. S., Mineral resources of southwestern Oregon: U. S. Geol. 

Survey Bull. 54b, pp. 12-11, 1914.

£/ The geology shown on plate 37 is modified from Diller and Key, op. cit.
4-3°00

UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY 

R.7 W. R.6 W.

BULLETIN 931 PLATE 37 

123° 20' R.5W. 43°00'

2 MILES

Geology modified from Diller and Kay, 

Folio 218, Riddle, Oregon

EXPLANATION

SEDIMENTARY ROCKS

Greenstone, gabbro, 

and related rocks

Boundary of area 

mapped in detail

GEOLOGIC MAP OF THE VICINITY OF NICKEL MOUNTAIN, DOUGLAS COUNTY, OREGON

U. S. GOVERNMENT PRINTING OFFICE: 1942 O - 430320 (FaCBS P. 208)
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY R.6W BULLETIN 931 PLATE 38

EXPLANATION

NICKEL MOUNTAIN

(Areas for future exploration. Probable

nickel content 1 percent or more)

T.

30

S.

Possible ore

(Includes scattered remnants of boxwork 

as roots in unweath-ered country rocks)

Open cut with dump

^^ss^J:-^-y-'--

Contour interval 50 feet

T.

30

S.

R.6W.

TOPOGRAPHIC AND GEOLOGIC MAP OF THE NICKEL DEPOSIT NEAR RIDDLE, DOUGLAS COUNTY, OREGON

Topography and geoiogy by 

S.VV^hobbs and W.T. Pecora
NICKEL DEPOSIT NEAR RIDDLE, OREGON 209 

Peri.dotite

In the ultrabasic intrusive mass of Nickel Mountain, peridotite is far more abundant than its derivative, serpentine. This 

is true of the entire intrusive body as well as the small part 

shown on plate 38, with which the nickel deposits are associated. 

In previous geologic reports on this region, "serpentine" is 

commonly used as a collective term for all the ultrabasic intrusive rocks, but as the nickel ore is associated only with the 

unserpentinized peridotite, it is essential to discriminate in 

this report between true serpentine and the peridotite from 

which the serpentine is derived. The name serpentine is therefore applied only to the serpentinized ultrabasic rocks, and the 

unaltered rock is called peridotite.

The peridotite is partly dunite and partly saxonite. Dunite 

contains more than 90 percent of blivine, ((Mg,Fe)pSi04 ), and 

saxonite contains, with its dominant olivine, as much as 40 percent of the orthorhombic pyroxene enstatite, ((Mg,Fe)Si03 ). 

Dunite and saxonite are not shown separately on the geologic 

map (pi. 38). Field study revealed no system in the distribution or structural orientation of masses of the two rocks. Although no fine-grained or chilled varieties were seen, large irregular masses of saxonite appear in places to be intrusive into 

dunite. Probably both rocks were formed in the same intrusive 

episode, but the saxonite crystallized later than the dunite.

The saxonite and dunite are coarse-grained and hard, and 

both contain a little scattered chromite, (PeCrpO.), but the few 

segregations of chromite are always associated with the dunite. 

Both rocks are dark yellow green on unweathered surfaces. In 

weathered outcrops the dunite is brownish green and exhibits a 

fine-textured lattice-work of joints. The weathered saxonite is 

dark reddish brown and has a coarse blocky jointing that makes 

it more resistant to weathering than the dunite, and it is further distinguished by a pitted surface, because the pyroxene in

430320 O 42 - 2
210 STRATEGIC MINERALS INVESTIGATIONS, 1941

it is more resistant to weathering than the olivine. This feature is especially noticeable where decay of the rock is far advanced, the olivine being completely changed to yellow limonite 

whereas the pyroxene remains in recognizable crystals.

As the nickel content of olivine is greater than that of enstatite (see table on p. 211), unweathered dunite has a higher 

nickel content than unweathered saxonite. Under certain conditions of weathering the nickel originally contained in the olivine became concentrated in the nickel-magnesium silicate garnierite, which, together with quartz, forms veinlets in both rocks. 

These veinlets are more abundant in the dunite than in the saxonite, as the dunite is the more closely jointed. The ratio of 

garnierite to quartz is also higher in the veins cutting dunite, 

as the larger olivine content affords a larger supply of nickel.

A brick-red soil which is developed on the surface of the 

nickel deposits is described In the section that deals with the 

deposits.

Serpentine

A band of partly or completely serpentinized peridotite, 

from 10 to several hundred feet in width, separates the unaltered parts of the intrusive body from the older rocks wherever 

the contact was observed. This border facies of the ultrabasic 

intrusive rock consists mainly of a black, fine-grained serpentine. In many specimens the pyroxene is unaltered although the 

olivine is completely serpentinized, but commonly the pyroxene 

also is serpentinized, being altered to lustrous bronze-colored 

pseudomorphs of bastite. Some of the partly altered peridotite 

contains veins of serpentine.

In places within the border zone of the intrusive there are 

masses Of green slickensided serpentine. This material encloses 

rounded blocks of the black, fine-grained serpentine, from which
211

it evidently was derived. A similar association was observed by

9/ Palache in the serpentine of the California Coast Ranges.

Analyses of two samples of serpentine show that it contains 

more nickel than the olivine samples that have been analyzed 

(see table below). However, no nickel deposit has been found in 

serpentine. Both varieties of serpentine weather to a graybrown soil that is conspicuously different from the soil over 

peridotite.

Analyses of rocks and minerals from Nickel Mountain

SiOg........................

Feo03 .......................

FeO. ........................

CaO.... .....................

MgO.........................

NiO.........................

Cr2 03 .... ...................

Ni..... .....................

1

41.43

.04

2.52

6.25

.55

4^ 74

.10

.76

4.41

QQ ftO

.08

.2

42.81

Not det.

2.61

7.20

45.12

.26

7Q

R7

99.36

?0

3

0.32

.25

4

0.05

.04

5

0.45

_

.35

6

0.33

.26

1. Peridotite (sazonite) with more than two-thirds olivine. Clarke, 

F. W., op. cit. (Iggg), p. 485.

2. Olivine, not entirely free from enstatite and chromite. Clarke, F. W., 

op. cit. (Iggg), p. 4g5.

3. Oliyine. Von Foullon, H. B. , op. cit., p. 226.

4. Orthorhombic pyroxene ("bronzite"). Von Foullon, H. B. , op. cit., 

p. 226.

5. Serpentine from locality near border east of stock. Von Foullon, 

H. 0., op. cit., p. 233.

6. Serpentine from locality northeast of Nickel Mountain. Kay, G. F. , 

op. cit., p. 126. George Stelger, analyst.

THE NICKEL DEPOSIT

The .typical ore of the nickel deposit is a blanket of 

deeply weathered peridotite, now almost entirely altered to 11- 

monite, which is host to an intricate lattice boxwork of quartzgarnierite veins. The deposit was formed during the weathering

2/ Palache, Charles, Lherzolite and associated rocks of the Potrero, 

San Francisco: California Univ., Dept. Geology, Bull. 1, pp. 161-lgO,

IO/ The term "ore" is not used here in the strict sense, being applied 

for convenience to material not rich enough to be worked profitably, in 

place of such cumbersome phrases as "potential ore", "nickel-bearing material".
212 STRATEGIC MINERALS INVESTIGATIONS, 1941

of the unserpentinized perldotite upon which it rests, by a twofold supergene process which involved the release of nickel from 

the primary minerals and its combination in nickel-poor secondary minerals under a humid tropical climate, and its subsequent 

'concentration in nickel-rich garnierite under a humid temperate 

climate. The deposits are the remains of a once more extensive 

blanket, which probably at one time covered most or all of the 

peridotite in the area. Landsliding, rill wash, and slope wash 

have stripped parts of the deposit from the unweathered peridotite. The weathered blanket is constantly undergoing further 

chemical change, so that in small areas further enrichment in 

nickel is being effected, apparently by the breaking down of 

early formed garnierite that contains relatively little nickel 

and the formation of nickel-rich garnierite and quartz. Garnierite does not seem to be forming directly from the peridotite 

under present climatic conditions.

Mineralogy

The principal minerals of the nickel deposit are garnierite 

(hydrous nickel-magnesium silicate), quartz, chalcedony, and 

chert (three varieties of silica), and llmonite (hydrated iron 

oxide). A small quantity of chromite (FeCrgO^) and manganese 

oxide are also present.

Garnierit-e. The garnierite ranges in color, even in the 

same vein or hand specimen, from yellowish green through apple 

green to blue green. The darkest variety, which presumably has 

the highest nickel content, occurs in some places as veinlets in 

the_yellowish-green variety. When the mineral is wet it is 

darker-colored than when it is dry. Some of it then crumbles 

under slight pressure, and some spreads like paste. The dry 

garnierite is soft but brittle, and will adhere to the tongue. 

Analyses of garnierite from Nickel Mountain are shown in the table on page 213.
NICKEL DEPOSIT NEAR RIDDLE, OREGON 

Analyses of garnierite from Nickel Mountain

213

Si02 .................................

AlpO-* + FepO-* ........................

MgO..................................

NiO..................................

H2 0+. ................................

HoO....... ...........................

Ni...................................

1

44.73

1.18

10.56

27.57

fi QQ

8.87

99.90 

PI fi7

2

48 ?1

1.38

19.90

23.88

} 6.63

'

100.00 

18.77

3

40.55

1.33

21.70

29.66

7.00

100.24 

23.31

4

48.82

i06

1 R 4Q

1 Q O4

12.29

98.70 

MQ7

1. Clarke, F. W., op. clt. (1SSS), p. UgU'.

2 and 3. Blake, W. P., Nickel: Mineral Resources U. S., 1SS2, p. ^

U. Von Foullon, H. B., op. cit., p. 2?2. (Apple-green garnierite.)

Enriched garnierite. Much of the garnierite of the main ore 

zone shows evidence of recent enrichment in nickel through the 

breakdown of an earlier-formed, nickel-poor variety. Near the 

base of the decomposed mantle rock a greenish-yellow to colorless variety of garnierite has been found in partly weathered 

dunite. This material is always below the ore and is well-exposed along the road bed and road cuts in the southeastern part 

of the deposit, in some places on the steep slopes in fresh peridotite, and on the bed-rock areas of the summit of Nickel Mountain. Quartz and green garnierite are both absent or rare at 

these localities, but if one is present, the other is also. 

Both enriched garnierite and quartz may occur as veins in the 

pale garnierite, but the quantity of the enriched material increases toward the surface and develops a network of cross-cutting quartz-garnierite veins. This is well shown at the Discovery and West Workings. The order of formation in all places is 

from pale garnierite to deeper-colored garnierite, and a rude 

zoning indicates a progression from pale varieties at depth to 

deeper-colored varieties toward the surface. This indicates a 

process of supergene nickel enrichment in garnierite, and the 

pale, unenriched garnierite, which is accompanied by limonite, 

is believed to be the source of both the nickel and the silica 

concentrated by the recent enrichment process.

430320 O - 42 - 3
214 STRATEGIC MINERALS INVESTIGATIONS,

Quartz. The quartz which is persistently associated with 

the garnierite in the boxwork veins is commonly white and finegrained. The quartz of the thin, flaky veinlets in the garnierite is porcellaneous, while that of the thicker veins is coarser 

and partly brownish. Brown chalcedony or cherty silica is common near the surface of the deposit. Quartz is generally more 

abundant than garnierite in the boxwork, but its relative abundance decreases downward from the surface.

Limonite.--Most of the limonite is soft and easily removed 

from the boxwork, but at a few places near the surface part of 

the limonite is silicifled to a brown, chert-like mass. One 

sample of limonite from between the quartz-garnierite veins of 

the boxwork contained about 1 percent of nickel.

Layers of the deposit

The nickel deposit is layered, as is well shown in the vertical section exposed at the Discovery workings and represented 

in figure 21. A top layer of brick-red soil, 2 to 3 feet thick, 

covers the main layer, 40 feet thick, of quartz-garnierite boxwork in limonite. Locally .the boxwork layer contains "boulders" 

of peridotite, which are incompletely altered residuals. The 

base of the boxwork layer is very irregular, but is approximately parallel to the hill slope. Below the boxwork layer is the 

basal or root layer. In it prongs of the peridotite project upward, and, conversely, roots of the boxwork project downward into fresh peridotite. The maximum depth of boxwork roots in peridotite is not known but is estimated to be about 150 feet.

Brick-red soil layer

The top layer of the deposit averages 2 to 3 feet in thickness and ranges from a thin veneer up to 9 feet, It consists of 

brick-red soil, soft and'incoherent, containing small round pellets of red iron oxide and, at the surface in a few places,
NICKEL DEPOSIT NEAR RIDDLE, OREGON 215

Leached surface 

Brick-red soil layer

Grades through 

orange to yellow 

col or of zone below

3'

Quart z-garnierite 

box work layer

Peridotite altered 

to soft yel low I imonite. Former 

joint cracks filled 

with ramifying network of quartzfarnierite veins, 

cattered residual 

"boulders" of fresh 

peridotite.

40'

\ Open cut

Shaft

Root layer

Root or ribs of , 

boxwork project ~{ ' 

down into fresh 

peridotite. Controlled by fractures L .____________ . 

or rock composition

Figure 21. Diagrammatic sketch of a vertical section of the mineral deposit 

at the Discovery workings.

small pieces of dull quartz or larger fragments of spongy quartz. 

The quartz, which is commonly stained with much manganese oxide, 

is a residue of weathered boxwork, and hence may be an excellent 

guide to unexposed boxwork ore.

The brick-red soil layer, originally derived from peridotite, 

supports a moderately heavy growth of vegetation, which con-
216 STRATEGIC MINERALS INVESTIGATIONS, ±941

trasts with the scant growth on areas underlain by serpentinized 

peridotite. Many of the trees that grow on it are tilted and 

curved, showing that even on gentle slopes the soil tends to 

creep, and as a consequence of this creep and the action of 

plant roots all structures of the original peridotite are obliterated in the soil layer.

Analyses of three composite samples of the brick-red soil 

show that they contain 0.95, 1.10, and 1.02 percent of nickel. 

(See table below.) The mineral in the soil that contains the 

nickel is unknown. It is reported that the soil contains between 0.75 and 2 percent of Cr 0 , which is probably in the form

Ci 3

of chromite. No complete analysis of the red soil is available.

Nickel content of red soil and red-soil wash, Nickel Mountain 

[Victor North, analyst]

Sample 

No.

1

2

4

Description

TVn 1f*V T*pH <3 n 1 ~l

....do.... ..........

....do.....*........

Location

Composite samples from surf*Q r* f* Q r\i 1 1* Vi o Q a 4~ ^ f* "HVi ^

Discovery area.

face near summit of 

Nickel Mountain.

face of 2 acres around 

Discovery shaft.

open cut, 4 ft. below 

surface, 3 ft. above 

boxwork ore.

Ni 

(percent )

[ 0.61

1 .71 

.95

1.10

1 OP

Wash derived from the brick-red soil layer of the upper 

slopes partly covers terraces and the bottoms of small valleys 

on the lower slopes of Nickel Mountain. Analyses of two composite samples of this wash material collected southeast of the 

Discovery area (see pi. 38. and fig. 22) show that they contain 

0.61 and 0.71 percent of nickel. The wash also contains very 

small grains of chromite.
NICKEL DEPOSIT NEAR RIDDLE, OREGON 217 

Quartz-garnierite boxwork layer

The boxwork layer attains a thickness of 40 feet at the Discovery workings, but it is between 10 and 20 feet thick in most 

other places. At several places, boxwork ore can be seen to 

project downward like roots into the underlying peridotite. 

This is well shown at the West shaft where a narrow irregular 

root of boxwork extends downward from the surface for at least 

85 and possibly 100 feet. Scattered patches of boxwork ore in 

areas of fresh peridotite are common in the vicinity of the main 

ore bodies, and probably represent the lower ends of the root 

zone of a once more extensive boxwork layer 

Two striking f.eatures characterize the boxwork in both the 

boxwork layer and the roots: (1) The intimate quartz-garnierite 

veins form a honeycomb in yellowish, hard or soft limonitic material weathered from peridotite, and (2) local fractures and

\v 

fracture veins with slickensideri walls are common.

Boxwork veins, Individual veins in the boxwork layer consist mainly of intergrown quartz and garnierite, and they range 

from paper-thin sheets to veins 2 inches or more in thickness. 

Quartz commonly forms the walls of th«e veins and encloses the 

garnierite, but it also forms intricate networks of very thin, 

white, porcellaneous veins in the nickel mineral. The relative 

proportions of the two minerals in the veins vary greatly from 

place to place. The boxwork layer on the north face of the Discovery open pit, which is exceptionally rich in garnierite, is 

estimated to contain 5 percent of garnierite, 15 percent of 

quartz, and 80 percent of limonite. Here, the boxwork layer 

averages between 3 and 4 percent of nickel. Elsewhere, garnierite commonly makes up 5 to 10 percent of the individual boxwork 

veins, but less in the veins near the surface in which leaching 

or rain wash have been active. Below the surface the veins are 

compact, but near and at the surface they contain open spaces
218 STRATEGIC MINERALS INVESTIGATIONS, 1941

whose walls are coated with brown-stained quartz. Brown quartz 

locally replaces the white quartz.

The garnierite varies in color and composition in the same 

vein. Green is the predominant color, and the shade of green is 

darker when the boxwork is wet. Both the percentage of garnierite in the veins and the nickel content of the mineral itself 

must be estimated before any evaluation of a boxwork exposure 

can be made -by inspection in the field.

In some places the boxwork, naturally exposed on the surface, 

is almost entirely leached of its garnierite, and there remains 

a heavy, spongy mass of brown and white quartz. When this 

leached outcrop material is broken;, small angular or rounded 

fragments of garnierite are frequently found within the protective quartz. Much of the boxwork ore of the dump piles also 

shows this feature. The exposed garnierite is more easily 

washed from the boxwork by rain than leached by the chemical 

activity of the water. Large masses of the sponge-quartz outcrops are exposed on the surface of the gentle slope immediately 

below the summit. Prospect pits prove conclusively that such 

leached outcrops can be used as guides for location of unexposed 

boxwork ore, but it is reported that the boxwork ore exposed beneath such leached outcrops contains less than 2 percent of 

nickel.

Joints and fractures in the fresh peridotite have been the

main factor in controlling the pattern as well as the thickness

of the veins. The coarse rectangular joint plan of the saxonite 

supports a very coarse boxwork. The largest observed joint 

block of saxonite is about 4 feet in diameter, many are 1 to 2 

feet, but most of the blocks are only a few inches across. The 

thickness of the individual veins of the boxwork varies in proportion to the size of the joint blocks that the veins enclose. 

The thickest of the veins of the boxwork are about 2 inches; the 

thinnest are mere films a fraction .of an inch across. The in-
NICKEL DEPOSIT NEAR RIDDLE, OREGON 219

dividual cells of the boxwork frequently contain a core of unweathered peridotite in a soft limonitic matrix, and this relationship is evidence of the process by which the peridotite 

was altered to form the ore. The closely spaced joints of the 

dunite, on the other hand, support a finer-textured boxwork of 

thinner septa; the joint blocks are rarely more than an inch 

across, are completely weathered, and are enclosed in a lacework 

of quartz and garnierite.

The limonite interstitial to the boxwork veins is soft and 

crumbly in the boxwork layer but is hard and compact at some 

places in the boxwork roots. A carefully collected sample, 

weighing about an ounce, of soft limonite from the boxwork deposit at the portal of the Discovery adit contained 1.3 percent 

of nickel (see table on p. 220).

Fracture veins, Open fractures are numerous in the boxwork 

ore and also in the peridotite that contains the boxwork root. 

Brown and white quartz and light- to dark-green garnierite form 

veins along these fractures, and both minerals show slickensides. 

The thickest vein, observed at the West shaft, ranges in thickness from 6 inches to a foot in a distance of 30 feet. Some 

fragments of the vein on the dump are 14 inches wide and consist 

predominantly of white and brown quartz, which encloses scattered small pellets of garnierite. The brown quartz is banded 

and flinty and clearly replaces the white quartz. Some cavities 

in quartz are lined with mamlllary crusts of dark-green garnierite and brown quartz.

Along some parts of the veins apple-green to blue-green garnierite has been deposited. The thickest vein of garnierite was 

observed on the south wall of the West open cut, where it ranged 

in thickness from 1 to 3 inches in a distance of 15 feet. The 

veins are not persiatant in depth and commonly extend less than 

20 feet along the strike. Boxwork is characteristically present 

in the wall rock and at the edges of the fracture veins.
220 STRATEGIC MINERALS INVESTIGATIONS, 1941

The attitude of the veins in the deposit is not systematic. 

Low dips are commoner than high ones for veins near the surface, 

but high dips are most characteristic for fracture veins in the 

r'oots. Where slickensides are present, movement is indicated in 

a direction down the present slopes of Nickel Mountain. The 

fractures that contain the fracture veins are possibly results 

of slumping, landsliding, or local collapse of the mineral deposit.

Nickel content of samples from boxwork and root zone,

Nickel Mountain 

[Victor North, analyst]

Sample 

No.

Description and Location Nl 

(percent)

1

2

3

4

5

6

7

8

9

10

11

Limonite between boxwork, portal of Discovery 

adit.

Rich pocket of garnierite ore from fracture vein 

in west wall of Discovery shaft.

Composite of five channel samples of boxwork ore 

from walls of Discovery open pit, representative of upper 15 ft. of boxwork.

Composite sample from 30 ft. of boxwork ore in 

Discovery shaft.

From bottom 5 ft. of Discovery shaftj part boxwork ore and part peridotite.

Composite sample from outer 150 ft. of Discovery 

adit; part boxwork ore and part peridotite.

Prom breast of Discovery adit, 175 ft. from portal; part boxwork ore and part peridotite.

Composite sample from upper 35 ft. of West 

shaft; mostly boxwork ore.

Prom bottom 4 ft. of West shaft (84-88 ft. below 

surface); mostly peridotite with films of garnierite and glassy quartz along fractures in 

rock.

Composite sample from outer 155 ft. of West 

adit; mostly boxwork.

Composite sample from inner 145 ft. of West 

adit (to face at 300 ft. from portal); mostly 

peridotiteo

1.31

8.09

2.07

2.81

1.84

2.06

1.35

1.94

.83

1.04 

.34

Root layer

The lowermost part of the blanket of ore is a zone in which 

root-like extensions of the boxwork material above penetrate the

underlying fresh peridotite. The zone is very irregular and 

marks the transition from ore to bedrock. The boxwork roots 

project downward into the fresh peridotite to an unknown depth.
NICKEL DEPOSIT NEAR RIDDLE, OREGON 221.

In the boxwork deposits of the West area and of the steep slope 

northwest of the Discovery deposit, which are interpreted as 

parts of the root zone, the greatest known depth of the roots is 

about 85 feet. This figure depends on the fact that the breast 

of the West adit, which lies about 40 feet directly below the 

bottom of the West shaft, ib in partly weathered peridotite with 

thin flakes of quartz and garnierite.

Only the boxwork roots need be explored in the root zone. 

Except where enrichment has taken place, the boxwork roots reportedly contain less than 1 percent of nickel.

Relation 'to slopes

It is generally recognized that the best deposits of garnierite lie on terraces and gentle slopes at altitudes above 

2,000 feet, and such ground therefore has been the most thoroughly prospected. (See fig. 22.) Some terraces cut on fresh 

peridotite below 2,000 feet, are mantled with wash,, consisting 

partly of boxwork and partly of red soil derived from upper 

slopes. The West area and the steep slope northwest of the Discovery area contain root deposits of a former gentle surface of 

higher elevation which, before erosion to the present slope, was 

probably rich in boxwork ore. Debris from the West area boxwork 

is abundant on a 2,500-foot terrace west of the mapped area of 

plate 38.

The dissected terrace at 2,000 feet is part of a widespread 

erosion surface,, and it is evidently much older than the' stream 

terraces, at least 500 feet lower, from which Pleistocene vertebrate remains have reportedly been collected. The deposits are 

probably not much younger than the .2,000-foot terrace, for no 

garnierite and limonite layer is known to have formed on any 

terrace cut on peridotite below the 2,000-foot terrace level. 

All local terraces in peridotite between 2,000 feet and the
N

fiq

-^ in Q. -Q

_ >-i f- inr}

§ 

o^e

in 3

If} 

^Dlgs» 

v £ (0

U0(j O'~_

r- ._ .A t-

»b 

«§ 

 s* 

s?

9*

-P

0) A

OS C

I. <w g°
NICKEL DEPOSIT NEAR RIDDLE, OREGON 223

summit of Nickel Mountain, on the other hand, have deep roots of 

boxwork ore. The writers therefore believe that the weathering 

of peridotite to a lateritic soil made up chiefly of limonite 

and nickel-poor garnierite took place during the time interval, 

probably late Tertiary, in which the Klamath Upland Surface was 

uplifted and dissected, to form ultimately a widespread mature 

erosion surface whose base, level in the area near Nickel Mountain is now represented by the 2,000-foot terrace. According to 

this interpretation, the present nickel deposit is largely a 

partially reworked remnant of a lateritic soil blanket, which 

originated in late Tertiary time, and no further weathering of 

this kind occurred in the- peridotite that was later exposed by 

dissection of the 2,000-foot terrace.

Formation of boxwork

Either of two conditions may have produced a deeply weathered llmonitic blanket on the peridotite during the formation of 

the late Tertiary 2,000-foot erosion level: (1) climatic conditions differing from that of later, presumably Quaternary time, 

or (2) longer weathering under the same climatic conditions. 

The writers favor the first alternative, and believe that the 

late Tertiary weathering was lateritic. A humid and tropical to 

subtropical climate would produce laterite on a peridotite surface of low relief. While the olivine was decomposing under 

these conditions, magnesium, nickel, and silica combined with 

water to form nickel-poor garriierite, and iron oxidized to form 

limonite. In true laterites, quartz is not precipitated within 

the deposit.

Under Recent humid-temperate climatic conditions new laterite did not form, but the laterite already formed became further 

altered. Decomposition of garnierite at the surface released 

silica, magnesium, and nickel. Much of the silica was precipitated as quartz, some magnesium was leached and lost, and much
224 STRATEGIC MINERALS INVESTIGATIONS, 1941

nickel was redeposited lower down to form green nickel-rich garnierite associated with quartz. In the root zone the nickelpoor garnierite has been partly decomposed and enriched in place.

The quartz-garnierite boxwork is therefore attributed to 

Recent weathering of the lateritic product of Tertiary weathering. Garnierite and quartz are being deposited at the present 

time along fractures in peridotite below the boxwork.

Both Von Foullon and Kay 'have argued that garnierite

was formed by the weathering of serpentine derived from perido13/ tite; and Austin 'believed that the quartz-garnierite veins

were of hydrothermal origin. In the writers' opinion, on the 

contrary, field evidence strongly indicates that the garnierite 

was derived from peridotite rather than serpentine and deposited, 

together with quartz, by a secondary supergene rather than hydrothermal action.

Reserves 

Grade

Under present conditions, garnierite ore containing less 

than 5 percent of nickel cannot be worked profitably. Most of 

the deposit at Nickel Mountain contains only 1 or 2 percent of 

nickel, and only a relatively small part, reckoned in minable 

tonnages, contains as much as 2 to 3 percent.

Calculations from samples totaling a few hundred pounds indicate that the boxwork ore at the Discovery workings contains 

between 2 and 3 percent of nickel, but representative samples of 

boxwork ore from other parts of the deposit contain less than 2 

percent of nickel. Samples weighing a few pounds and containing 

3 to 5 percent or more of nickel can indeed be collected one 

taken by the writers from the richest pocket of garnierite obll/ Von Foullon, H. B., op. cit. 

12/ Kay, 0. J., op. clt. 

l^/ Austin, W. L., op. cit.
NICKEL DEPOSIT NEAR RIDDLE, OREGON 225

served contains 8.09 percent of nickel but these samples are

riot representative. The results of the writers' sampling indi-

\ 

cate that the nickel content of the deposit is lower than has

14/ been reported. Kay, for example, states that two specimens,

collected as representing average boxwork ore, contained 5.35 

and 4.94 percent of nickel, and that about 20 tons of ore, 

shipped by the Oregon Nickel Mines Co. for experimental purposes, 

was reported by the company to contain between 5 and 8 percent 

of nickel.

Estimates of tonnage

At the Discovery shaft, adit, open cut, and adjacent

15/ 

trenches there is a proved minimum of 80,000 tons of boxwork

ore in which the nickel content is estimated to be at least 2 

Estimated tonnage of nickel ore at Nickel Mountain

Location

Boxwork : -/

T^1 <3 f* OV A T*"W WOY'lr'1 Tl CT Q

West workings 0 ............

pits, short adits, dumps

"Dl Q P f"\Tr£* Y*"V Q Y»AO

Upper area. ................

Brick-red soil: '

T^l Qf*OTrA"PTT nY*AQ

Proved ore 

( tons )

80,000

50,000

25,000

Probable ore 

(tons )

200,000

2,000,000

500,000

3,000,000

240,000

48,000

300,000

Estimated 

Ni content 

(percent)

2 to 3

1 to 2

1 to 2

1 to 2

1 to 2

1 to 2

1 fn I 1

i (-/-, Ti

 -t-o 1 

I/ Boxwork calculations based on 20 cu. ft. per ton. 

2/ Red soil calculations based oa 23 cu. ft. per ton.

but not more than 3 percent. In the area surrounding the Discovery open cut there is probably at least 200,000 tons of the 

same grade. The exposures over a wider area about the Discovery 

workings indicate that there is probably about 2,000,000 tons

lU/ Kay, 0. F., op. clt.. p. 124.

!£/ Calculations of boxwork ore are based on an estimate of 20 cubic 

feet per ton.
226 STRATEGIC MINERALS INVESTIGATIONS, 1941

more material with a nickel content of 1 to 2 percent. Further 

prospecting within this promising area might justify a higher 

estimate.

At the West workings, the shaft, open cuts, and adit develop 

a proved minimum of 40,000 tons of boxwork ore, and at the open 

cuts north of the West adit there is at least 10,000 tons of 

proved ore, having a nickel content between 1 and 2 percent. 

The probable ore in the area about the West workings amounts to 

about 500,000 tons, of the same grade.

Scattered pits, trenches, short adits and dump piles partly 

block out about 25,000 tons of boxwork ore containing between 

1 and 2 percent; this also may be regarded as proved ore.

For the large area east of the West workings, the estimate 

of probable ore is 3,000,000 tons with a grade of 1 to 2 percent. 

Much of this area is as yet unexplored, so that a larger tonnage 

is possible. In some places, however, the boxwork ore may contain less than 1 percent and in others more than 2 percent.

In all, the Nickel Mountain deposit contains more than 

6,000,000 tons of boxwork ore, composed of limonlte, quartz, 

garnierite, and chromite, with a nickel content of 1 percent o>r 

more. There is, in addition, over 600,000 tons of brick-red 

soil containing 1/2 .to 1^- percent of nickel.

The deposit can be mined by power shovels at low cost, but 

a new method of treating nickel silicate ores or a great increase in the price of nickel would be required to make mining 

of the deposit profitable.

O
The use of the subjoined mailing label to return

this report will be official business, and no

postage stamps will be required

U. 3. GOVERNMENT PRINTING OFFICE 6 9772

UNITED STATES PENALTY FOR PRIVATE USE TO AVOID 

DEPARTMENT OF THE INTERIOR PAYMENT OF POSTAGE. $300

GEOLOGICAL SURVEY

OFFICIAL BUSINESS

This label can be used only for returning 

official publications. The address must not 

be changed.

GEOLOGICAL SURVEY,

WASHINGTON, D. C.