GEOLOGICAL SURVEY CIRCULAR 624 

Platinum, Palladium, and 

Rhodium Analyses of 

Ultramafic and Mafic Rocks 

from the Stillwater Complex 

Montana 

Platinum, Palladium, and 

Rhodium Analyses of 

Ultramafic and Mafic Rocks 

from the Stillwater Complex 

Montana 

By Norman J Page, Leonard B. Riley, and Joseph Haffty 

G E 0 L 0 G I C A L 5 U R V E Y C I R C U L A R 62.4 

Washington 1969 
United States Department of the Interior 

WALTER J. HICKEL, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
Abstract-------------------------------

Introduction----------------------------

Acknowledgments ---------------------- Sampling and analytical methods---------

CONTENTS 

Page 

1 Pt, Pd, and Rh assay data-----------------

Conclusions-----------------------------

References cited-------------------------

ILLUSTRATION 

Figure 1. Platinum, palladium, and rhodium ratios for each specimen from the Stillwater 

Page 

2 

3 

3 

Page 

Complex, ~ont------------------------------------------------------------------ 2 

TABLES 

Page 

Table 1. Subdivisions and terminology used for the Stillwater Complex, ~ont--------------------- 1 

2. Platinum, palladium, and rhodium analyses of rocks from the Stillwater 

Complex, ~ont ------------------------------------------------------------------ 6 

3. Arithmetic averages of Pt, Pd, and Rh_,in parts per billionJfor zones, members, 

and rock types of the Stillwater Complex, ~ont ------------------------------------- 12 

III 

Platinum, Palladium, and Rhodium Analyses of Ultramafic 

and Mafic Rocks from the Stillwater Complex, Montana 

By Norman J Page, leonard B. Riley, 

and Joseph Haffty 

ABSTRACT 

An a 1 y s e s by a combination fire- assa~solution-optical· 

emission spectrographic method of 137 rocks from the Stillwater 

Complex, Mont., indicate that platinum, palladium, and rhodium 

are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per 

billion, w-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a 

maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb 

Rh. 

INTRODUCTION 

The occurrence of minor amounts of platinum -group 

metals in the Basal, Banded, and Upper zones of the 

Stillwater Complex was first documented by Howland 

(1933) and Howland, Peoples, and Sampson (1936). As 

part of the Heavy Metals program ofthe U.S. Geological Survey, a study of the distribution of the platinumgroup metals within the complex resulted in the discovery of platinum-bearing minerals in the Peridotite 

member of the Ultramafic zone (Page and Jackson, 

1967). Some of the platinum-group metals occur as 

the minerals laurite, cooperite, and a platinum-iron 

alloy which are included within cumulus olivine and 

c h r om i t e of the G and H c h r o m i t it e zones. The 

platinum-bearing minerals are associated with ironnickel-copper sulfide minerals and are concentrated 

in chromite relative to olivine. Recently, Grimaldi and 

Schnepfe ( 1969) have proposed that most of the rhodium 

and some of the platinum are in chromite either as 

solid solution or as small inclusions. 

In order to survey the other petrologic environments 

within the complex, large bulk rock samples were collected for Pt, Pd, and Rh assays. The results from 137 

samples are given in this report (table 2). 

Samples have been located relative to coordinate 

systems used on the maps of the complex which appear in the following reports: Peoples and Howland 

(1940), Howland, Garrels, and Jones (1949), Jackson, 

Howland, Peoples, and Jones (1954), Peoples, Howland, 

Jones, and Flint (1954), Howland (1955), and Jones, 

Peoples, and Howland (1960). Designation of geographical areas follows the usage of these reports. Stratigraphic terminology is shown in table 1 and follows 

that of Hess (1960), Jones, Peoples, and Howland 

(1960), and Jackson (1961); cumulus terminology is 

from Jackson (1967). 

Table 1.--Subdivisions and terminology used for the 

Stillwater Complex, Mont. 

Zone Member 

Upper zone -----

Banded zone -----

Bronzitite member 

Ultramafic zone l[ontain' about 15 cy- Peridotite member clic units,each of 

which normally has 

Basal zone a chromitite zone, 

labelled A through 

Hornfels ----- K from the base 

upward. 

ACKNOWLEDGMENTS 

The contribution of samples taken previous to 1968 

by E. D. Jackson is warmly acknowledged. 

SAMPLING AND ANALYTICAL METHODS 

Ten to 40 pounds of rock was collected from surface 

outcrops as hand-specimen samples (a single large 

block), as chip samples (chips at specified intervals 

perpendicular to the foliation over the outcrop extent), 

and as channel samples. The specimens were crushed 

to a size fine enough to pass through a 50-mesh screen 

and then split and put in paper containers. One-quart 

splits of screened material were then submitted for 

analysis. 

The combination method of analysis of Haffty and 

Riley ( 1968) was used to obtain the v a 1 u e s of the 

platinum-group metals reported in this paper. In this 

method, fire-assay techniques are used to collect the 

Pt-Pd-Rh of the sample into a gold bead; this bead is 
Rh EXPLANATION 

• 

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I 0 0 

I 0 

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e 

~· e ee 

e ~ e 

~ e e e 

e e 

e 

• •• 

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e 

e 

e 

0 • 

Oe 

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ee e 

e 

e ~ If ~ 

£0 • ~ • • 

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e 

~e 

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e 

e 

~ a 

Ill 

Q) 

~ 

0 

N 

u 

4: 

ttl 

E 

ttl 

s... 

+-' 

Banded and Upper zone 

0 

Bronzitite member 

e 

Chromite cumulate and 

chromite-olivine cumulate 

• 5 Olivine cumulate or olivineorthopyroxene cumulate 

e 

£ 

Norite and hornfels 

• Norite and sulfides 

~ 

Hornfels 

3 samples • 2 samples o 

-3 samples • 

18 samples • 

Figure 1.--Platinum, palladium, and rhodium ratios for each specimen from the 

Stillwater complex, Mont. 

d i s so 1 v e d in aqua regia, and an optical-emission 

spectrographic analysis is made of this solution. As 

shown by Haffty and Riley, samples of certain types 

of materials and especially samples rich in chromite 

are more difficult to fire assay than routine gold ores. 

Several expedients have been used to overcome these 

difficulties, such as varying the flux composition, reducing the amount of sample taken (as from 15 g (gram) 

to 3 g), or increasing the amount of flux. Fine grinding 

helped on some of the chromitites. Another helpful 

variation for many chrome-rich samples was the addition of a small amount of molten flux to the main charge 

a few minutes before pouring, so that it could act as a 

"wash." 

PT, PD, AND RH ASSAY DATA 

Table 2 lists the results of the fire-assay-emissionspectrographic analyses of the rocks from the com2 

plex as values in parts per billion (10-9). Included are 

coordinate locations of the sam p 1 e s, brief rock descriptions, and sample-collection types. The analyses 

are grouped in geographic areas from east to west in 

the complex and are listed, as closely as possible, 

within the groups in stratigraphic order from the base 

of the complex upward. Figure 1 is a plot of Pt, Pd, 

and Rh ratios for all the samples; rock types and zones 

are designated by symbols. Examination of figure 1 

and table 2 shows that the Pt, Pd, and Rh ratios for 

the three main zones vary widely and that a s i n g 1 e 

value or range of values is probably not representative of a particular zone, whereas the total amount of 

platinum metals tends to correlate well with rock type 

and zone. The amount of platinum metals seems to correlate with stratigraphic position, the larger amounts 

being found at low stratigraphic positions. The general 

order of concentration of platinum metals, from the 
most enriched rocks to the least enriched rocks, is 

(1) chromitites, (2) other Ultramafic zone rocks, (3) 

Basal zone norites and massive sulfide pods, (4) hornfels, and (5) Banded and Upper zone rocks. 

Table 3 gives the arithmetic averages for Pt, Pd, and 

Rh. Average mill concentrates and tailings are included 

because they represent combined samples of the G and 

H chromitite zones. The sum of the averages of Pt, Pd, 

and Rh tends to decrease from the A chromitite zone 

to the G chromitite zone and tends to increase from 

the G chromitite zone to the J chromitite zone. From 

the A to the G zone, there is an increase in the Rh/ 

(Rh+Pt+Pd) ratio, whereas from the G to the J zone 

the Rh/(Rh+Pt+Pd) ratio remains fairly constant. 

Examination of the other samples analyzed shows no 

definite trends of Pt, Pd, and Rh ratios with stratigraphic position or rock type. 

Comparison of the geographic areas in which Pt, Pd, 

and Rh are more enriched in chromitites to the lateral 

variations in the thicknesses of chromitite zones and 

the Peridotite member (Jackson, 1963, fig. 3) indicates 

that the enriched areas are on the edges of basinlike 

structures. If the Rh/ (Rh+Pt+Pd) ratios are compared 

with the Fe+3; (Fe+3 + Fe+2) ratio in chromite from the 

chromitite zones (Jackson, 1963, fig. 6), then it appears 

that low Rh/ (Rh+Pt+Pd) ratios cor r e 1 at e with low 

values of oxidation ratios. Tentatively, low Fe+3 concentrations in the chromite, which probably reflect low 

p a r t i a 1 pressures of oxygen in the differentiating 

magma, tend to favor the concentration of Pt and Pd 

with respect to Rh. This is to be expected if Pt and Pd 

occur as platinum -metal-iron alloys which require low 

partial pressures of oxygen for their formation. 

Each sample was an a 1 y zed by a semiquantitative 

spectrographic method (R. H. Heidel, analyst). The 

following list of 54 elements were looked for: Al, Ag, 

As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, 

Ge, Hf, In, Ir, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, Os, 

P, Pb, Pd, Pt, Re, Rh, Ru, Sb, Sc, Si, Sn, Sr, Ta, Te, 

Th, Ti, Tl, U, V, W, Y, Yb, Zn, Zr. Preliminary examination of the spectrographic results suggests that 

only V has a correlation with the sum of Pt, Pd, and 

Rh, as determined by the quantitative fire-assayspectrographic method; that is, increased V is associated with increases in the platinum metals. It is possible that V may be a favorable geochemical tracer 

for these metals within the Stillwater Complex. 

CONCLUSIONS 

The A chromitite zone of the Stillwater Complex is 

enriched in Pt, Pd, and Rh, has an average platinummetal content of 3.5 ppm (parts per million) along the 

strike (Jackson, 1963, 1968), and ranges in thickness 

from a few inches to a couple of feet. Samples of the 

A chromitite zone taken in the eastern end of the West 

Fork area to Crescent Creek (a linear distance of about 

1 1/2 miles) have an arithmetic average of 4.6 ppm 

platinum metals; this zone has not been sampled from 

Crescent Creek west to the B o u 1 de r River. This 

3 

average value is comparable with averages of 8.6ppm 

platinum metals from the Merensky Reef, 3.4 to 5.1 

ppm from the Great Dyke, and 0.86 ppm from Sudbury 

(Allen, 1960). 

More systematic reconnaissance and geochemical 

exploration is necessary to define more promising targets within the lower chromitite zones than has been 

reported here. The present data only suggest zones of 

economic interest. 

REFERENCES CITED 

Allen, C. C., 1960, The platinum metals: CanadaMineral Resources Division, Department of mines and 

technical surveys: Mineral Rept. 3, 68 p. 

Grimaldi, F. S., and Schnepfe, M. M., 1969, Mode of 

occurrence of Pt, Pd, and Rh in chromitite: U.S. 

Geol. Survey Prof. Paper 650-C. (Inpress). 

Haffty, Joseph, and Riley, L. B., 1968, Determination 

of palladium, platinum, and rhodium in g eo 1 o g i c 

materials by fire-assay and em i s s ion spectrography: Talanta, v. 15, p. 111-117. 

Hess, H. H., 1960, The Stillwater Igneous Complex, 

Montana, a quantitative mineralogical study: Geol. 

Soc. America Mem. 80, 230 p. 

Howland, A. L., 1933, Sulphides and metamorphic rocks 

at the base of the S t i 11 water Complex, Montana: 

Princeton Univ., unpub. Ph.D. thesis, 76 p. 

1955, Chromite deposits in the central part of 

---rile Stillwater Complex, Montana: U.S. Geol. Survey 

Bull. 1015-D, p. D99-0121. 

Howland, A. L., Garrels, R. M., and Jones, W. R., 1949, 

Chromite deposits of the Boulder River area, 

Sweetgrass County, Montana: U.S. Geol. Survey 

Bull. 948-C, p. C63-C82. 

Howland, A. L., Peoples, J. W., and Sampson, Edward, 

1936, The Stillwater igneous com p 1 ex and associated occurrences of nickel and platinum metals: 

Montana Bur. Mines Misc. Contr. 7, 15 p. 

Jackson, E. D., 1961, Primary texture and mineral 

associations in the Ultramafic zone of the Stillwater Complex, Montana: U.S. Geol Survey Prof. 

Paper 358, 106 p. 

1963, Stratigraphic and lateral variation of chro-

---rTihe composition in the Stillwater Com p 1 ex: Mineral. Soc. Am. Spec. Paper 1, p. 46-54. 

1967, Ultramafic cumulates in the S t i 11 water, 

-creat Dyke, and Bushveld intrusions, in Wylie, 

P. J., ed., Ultramafic rocks: New York, John Wiley 

& Sons, Inc., p. 20-38. 

1968, The chromite deposits of the S t i 11 water 

-complex, Montana, in Ridge, J. D., ed., Ore deposits of the United States 1933-1965: New York, 

Am. Inst. Mining, Metall., and Petroleum Engineers, p. 1496-1510. 

Jackson, E. D., Howland, A. L., Peoples, J. W., and 

Jones, W. R., 1954, Geologic maps and sections of 

the eastern part of the Stillwater complex, in Stillwater County, Montana: U.S. Geol. Survey open-file 

rept. 
Jones, W. R., Peoples, J. W., and Howland, A. L., 1960, 

Igneous and tectonic structures of the S t i 11 water 

Complex, Montana: U.S. Geol. Survey Bull. 1071-H, 

p. H281-H335. 

Page, N. J, and Jackson, E. D., 1967, Preliminary report on sulfide and platinum-group minerals in the 

chromitites of the Stillwater Complex, Montana: 

U.S. Geol. Survey Prof. Paper 575-D, p. Dl23-

Dl26. 

4 

Peoples, J. W., and Howland, A. L., 1940, Chromite 

deposits of the eastern part of the Stillwater complex, Stillwater County, Montana: U.S. Geol. Survey 

Bull. 922-N, p. N371-N416. 

Peoples, J. W., How land, A. L., Jones, W. R., and 

Flint, Delos, 1954, Geologic map, sections, and 

map of underground workings of the Mountain View 

Lake area, Stillwater County, Montana: U.S. Geol. 

Survey open-file rept. 
TABLES 2 and 3 
Table 2.--Platinum, palladium, and rhodium analyses of rocks from the 

Stillwater Complex, Mont. 

[Analysts: Joseph Haffty, W. D. Goss, and 0. M. Parker. Samples were analyzed by a combination 

fire-assay-optical-emission spectrographic method. 

System: ACM, based on SE corner of NEl/4 sec. 21, T. 55 S., R. 15 E., as 50,000 N.-50,000 E. 

(Peoples and others, 1954). BM, based on section corner common to sees. 25, 36 of R. 15 E. 

and sees. 30, 31 of R. 16 E., T. 5 S., as 120,000 N.-120,000 E. (Jackson and others, 1954). 

NB, based on SE corner of NEl/4 sec. 21, T. 55 S., R. 15 E., as 50,000 N.-50,000 E. (Jackson 

and others, 1954). MS, Montana (South) rectangular coordinate system, Mount Douglas and 

Mount Wood 15-minute quadrangles. WF, based on Wl at east end of West Fork base line assumed 

as 20,000 N.-20,000 E. (Howland, 1955). GM, based on Flat north end of Boulder River base 

line assumed as 20,000 N.-20,000 E. (Howland and others, 1949). 

Rock type: Cr, chromite; ol, olivine; br, bronzite or orthopyroxene; cpx, clinopyroxene; pc, 

plagioclase. 

Sample type: H, hand-specimen samples; CH-10',1.5', chip sample; first number is the width of 

outcrop, second number, the chip interval; C-10', channel sample for distance specified, 

width and depth of channel varies to yield enough rock for analysis; var., varying interval. 

Limits of determination: <10 ppb Pt, <4 ppb Pd, <5 ppb Rh. tr indicates element is present but 

below limits of determination and too low to assign a value, all values based on a 15g sample weight] 

Coordinates 

Northerly Easterly System 

Rock Sample Parts per billion 

type type Pt Pd Rh 

BASAL ZONE 

BENBOW AREA 

119,245 117,880 BM Chill norite H ll 12 <5 

119,245 117,880 BM Hornfels H tr 15 <5 

117,645 121,017 BM Gossan C-3 1 <10 17 <5 

117,595 121,036 BM Norite, sulfjde, hornfels H tr 88 <5 

117,512 121,162 BM Diabase dike H <10 <4 <5 

119,433 117,645 BM Gossan H 10 30 <5 

121,413 116,470 BM Gossan in norite H <10 14 <5 

119,704 117,965 BM Br cumulate H <10 tr <5 

NYE LIP AREA 

48,000 54,395 NB Norite H "10 15 <5 

47,740 54,570 NB Chill nori te H 13 11 <5 

MOUNTAIN VIEW AREA 

47,822 44,193 ACM Quartz monzonite H <10 <4 <5 

47,817 44,190 ACM Hornfels H <lO 7 <5 

47,842 44,115 ACM Massive sulfides CH-40 1 ,4 1 <10 55 tr 

"A" tunnel mine dump Massive sulfides H 24 84 10 

"A" tunnel mine dump Nor~te with sulfides H tr 56 <-5 

47,886 43,919 ACM Nori te CH-30 1 ,2 1 <10 18 <5 

47,892 43,815 ACM Hornfels CH-20 I ,1 I 16 15 <5 

48,040 43,622 ACM Nori te <10 <4 <5 

509,780 1,898,130 MS Norite and hornfels CH-50 1 ,5 1 <10 19 <5 

47,060 49,409 ACM Norite H 10 16 <5 

42,755 49,409 ACM Norite H tr 33 <5 

6 
Table 2. -Platinum, palladium, and rhodium analyses of roaks from the 

Stillwater Complex, Mont.-Continued 

Coordinates Rock Sample Parts per billion 

Northerly Easterly System type type Pt Pd Rh 

•BASAL ZONE-Continued 

BLUEBIRD PEAK AREA 

505,020 ~1,880,380 MS Hornfels H <10 9 <5 

WEST FORK AREA 

21,070 15,500 WF Hornfels H 13 15 <5 

GISH AREA 

542,300 1,814,440 MS Hornfels H 17 25 tr 

542,440 1,814,450 MS Norite H tr 7 <5 

ULTRAMAFIC ZONE 

BENBOH AREA 

Peridotite Member 

119,582 118,615 BM Chromitite, A zone C-0.83 1 26 180 21 

120,485 117,663 BM Chromitite, B zone H 71 67 63 

117,665 121,260 BM Chromitite, B zone H 82 51 67 

117,755 121,450 BM 01-br cumulate, B zone CH-20' ,1 I <10 tr <5 

120,387 118,025 BM Chromitite, c zone C-2' 45 36 42 

118,443 121,485 BM Chromi ti te, E zone C-4' 10 5 ll 

119,020 121,340 BM Chromitite, G zone C-6 1 42 9 65 

Benbow mill site Chromite concentrate H 42 5 34 

Benbow tailings pond Mi 11 tailings H 53 17 69 

121,734 118,967 BM Chromitite, H zone H 180 81 12 

119,427 121,525 BM Gabbro-pegmatite, CPI-9' ,1' 32 45 15 

J zone 

119,410 121,520 BM Chromitite~ J zone CH-2' 330 270 190 

119,450 121,545 BM 01-br cumulate, J zone CH-20' ,0 .5' <10 14 11 

119,695 121,597 BM Chromitite, K zone C-3" <10 <4 37 

119, no 121,586 BM 01 cumulate, K zone CH-8 1 ,0.5 1 <10 <4 6 

119,830 121,580 BM Br cumulate, K zone CH-20 1 ,1 I <10 9 tr 

Bronzitite Member 

-500,000 -1,995,000 MS Br cumulate CH-1700' ,60 1 38 16 9 

123,203 120,408 BM Br-cr cumulate C-2.5' 17 16 23 

NYE LIP AREA 

Peridotite Member 

48,736 55,612 NB Chromitite, A zone H 20 89 100 

7 
Table 2.--Platinum, palladium, and Phodium analyses of Pocks fPom the 

StillwateP Complex, Mont.--Continued 

Coordinates 

Northerly Easterly System 

49,014 

48,588 

48,722 

48,792 

49,063 

48,236 

48,236 

48,172 

49,200 

48,124 

49,823 

49,838 

49,878 

50,235 

50,236 

50,240 

50,314 

50,527 

55,555 

53,205 

53,295 

53,338 

57,030 

39,578 

39,578 

39,538 

42,925 

42,890 

40,801 

40,785 

40,720 

40,428 

40,222 

40,418 

40,406 

40,214 

Mouat chrome stockpile 

Mouat Mill Tailings pond 

512,540 

512,700 

512,760 

505,140 

1,896,540 

1,896,700 

1,896,900 

1,887,650 

NB 

NB 

NB 

NB 

NB 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

ACM 

MS 

MS 

MS 

MS 

Rock 

type 

Sample 

type 

ULTRAMAFIC ZONE--Continued 

NYE LIP AREA--Continued 

Peridotite Member--Continued 

Chromitite, B zone C-3 1 

Chromitite, G zone C-4.3 1 

Chromitite, H zone C-3 1 

Chromitite, I(?) zone C-0.83 1 

Chromitite, K zone C-1.3 1 

MOUNTAIN VIEW AREA 

Peridotite Member 

Gossan H 

Sulfide box work H 

Chromitite, A zone C-2.3 1 

01 cumulate~ H 

serpentinite 

Chromitite, A zone C-.75 1 

01 cumulate H 

01-br cumulate H 

Br cumulate H 

Gabbro pegmatite, G zone H 

Chromitite, G zone C-10 1 

Chromitite, G zone C-3 1 

01 cumulate, G zone CH-30 1 ,2 1 

Chromitite, H zone C-5 1 

Chromite concentrate 

Mill tailings 

Bronzitite Member 

Br cumulate 

Br cumulate 

Br cumulate 

INITIAL AREA 

Peridotite Member 

Chromitite, A zone 

8 

CH 

CH 

CH-220 I ,3 I 

CH-205 I' 5 I 

CH-190 1 ,3 1 

C-3 1 

Parts per billion 

Pt Pd Rh 

33 

45 

35 

52 

110 

220 

32 

450 

<10 

85 

tr 

tr 

42 

<10 

36 

ll 

<10 

46 

31 

51 

<10 

16 

41 

93 

49 

9 

12 

40 

72 

330 

79 

2300 

14 

360 

6 

4 

20 

<4 

<4 

<4 

<4 

52 

8 

21 

8 

9 

14 

25 

42 

61 

29 

38 

50 

160 

34 

160 

<5 

50 

5 

tr 

38 

<5 

60 

46 

tr 

48 

37 

53 

12 

19 

8 

170 
Table 2.--Ptatinum, pattadium, and rhodium anatyses of rocks from the 

Stittwater Comptex, Mont.--Continued 

Coordinates Parts per billion 

Northerly Easterly System 

Rock 

type 

Sample 

type Pt Pd ~ 

506,ll0 

505,940 

21,284 

20,415 

21,286 

21,773 

21,285 

21,285 

20,480 

21,284 

21,284 

21,284 

21,284 

21,284 

21,850 

21,284 

21,323 

21,320 

21,633 

21,776 

dl,979 

22,439 

22,439 

22,439 

21,738 

1,883,120 

1,880,980 

17,684 

15,350 

17,686 

14,288 

17,684 

17,684 

15,350 

17,684 

17,684 

17,685 

17,685 

17,685 

14,388 

17,684 

15,665 

15,670 

14,776 

14,720 

15,228 

14,745 

14,745 

14,745 

15,938 

MS 

MS 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

WF 

ULTRAMAFIC ZONE-Continued --- -------- -- ---~---

INITIAL AREA--Continued 

Peridotite Member--Continued 

Chromitite, B zone H 140 

BLUEBIRD PEAK AREA 

Peridotite Member 

Chromitite, B zone H 460 

WEST FORK AREA 

Peridotite Member 

01 cumulate CH-10' ,0.6' 11 

Chromite, A zone, lower H llOO 

Chromitite, A zone, lower H 400 

Chromite, A zone, lower H 350 

Chromitite, A zone, lower C-1' 520 

01 cumulate CH-10' ,0.6' 98 

Chromitite, A zone, lower H llO 

Chromitite, A zone,upper C-0.75' 1900 

Chromitite, A zone, upper C-0.75' 2100 

Chromitite, A zone, upper C-9" 2300 

01-cr cumulate, A zone upper C- 4" llOO 

Chromitite, A zone, upper C- 1" 150 

Chromitite, A zone, upper H 52 

01 cumulate CH-10' ,0.6' 18 

Chrom:i t i te, A zone, upper H 8000 

Ol clLwulai;e H <10 

Chromitite, A zone, lower C-3' 710 

Chromitite, A zone, upper C-l' 490 

Br cumulate H <10 

01 cumulate H <10 

Chromitite, G zone C-0.92' 45 

01 cumulate H 24 

Chromitite, G zone H 32 

9 

23 

120 

17 

1300 

810 

1900 

860 

190 

440 

5000 

5400 

8200 

4300 

840 

220 

160 

nooo 

ll 

1200 

1900 

8 

<4 

14 

45 

18 

86 

310 

tr 

llO 

130 

150 

130 

40 

56 

480 

430 

640 

220 

64 

32 

5 

1700 

5 

110 

200 

12 

<5 

59 

15 

54 
Table 2.--Platinum~ palladium~ and rhodium analyses of rocks from the 

Stillwater Complex~ Mont.--Continued 

Coordinates Parts per billion 

Northerly Easterly System 

Rock 

type 

Sample 

type Pt Pd Rh 

21,737 

21,802 

21,882 

22,432 

506,460 

506,78C 

511,260 

526,520 

524,130 

16,958 

l7 ,109 

17,078 

16,595 

17,380 

16,705 

17,200 

16,918 

499,080 

501,540 

501,280 

501,760 

15,937 

16,000 

16,026 

15,803 

1,865,740 

1,865,970 

WF 

WF 

WF 

WF 

MS 

MS 

1,857, 850 MS 

1,839,100 

1,838,180 

21,635 

21,710 

21,688 

22,378 

21,782 

22,375 

22,058 

22,675 

1,923,880 

1,925,570 

1,925,870 

1,926,950 

MS 

MS 

GM 

GM 

GM 

GM 

GM 

GM 

GM 

GM 

MS 

MS 

MS 

MS 

ULTRAMAFIC ZONE--Continued 

WEST FORK AREA--Continued 

Peridotite Member--Continued 

Chromitite, G zone 

Chromitite, H(?) zone 

Chromitite, I(?) zone 

Bronzitite Member 

Br cumulate 

CRESCENT CREEK AREA 

Peridotite Member 

H 

C-0.13' 

C-0.67' 

H 

62 

110 

<10 

15 

Chromitite, A zone 

Chromitite, B(?)zone 

C-2" 640 

IRON MOUNTAIN AREA 

Peridotite Member 

Chromitite, A(?)B(?) 

CHROME MOUNTAIN AREA 

Peridotite Member 

Chromitite, G zone 

Mafic dike 

GISH MEMBER 

Peridotite Member 

01-br cumulate 

Intrusive dunite 

Br cumulate 

Br cumulate 

Chromltite, G zone 

Chromitite, G zone 

01 cumulate 

Chromitite, H(?) zone 

BANDED AND UPPER ZOJ':W 

BENBOW AREA 

Br-pc cumulate 

Br-pc cumulate 

Pc cumulate 

Pc cumulate with sulfides 

10 

CH-L5' ,var. 79 

C-0.75' 71 

C-1. 67' 25 

H <10 

H <10 

H <10 

H <10 

H <10 

C-16' 40 

C-5' 290 

H 20 

H 210 

H 23 

H <10 

H <10 

C-7' <10 

48 

36 

8 

9 

1500 

140 

270 

9 

<4 

9 

<4 

<4 

28 

400 

14 

68 

12 

tr 

<4 

59 

73 

23 

14 

170 

24 

40 

33 

<5 

<5 

tr 

11 

<5 

28 

48 

10 

260 

tr 

<5 

<5 

<5 
Table 2.--Platinum, palladium, and rhodium analyses of rocks from the 

Stillwater Complex, Mont.--Continued 

Coordinates Rock Sample Parts per billion 

Northerly Easterly System type type Pt Pd Rh 

BANDED AND U~PE~ZONE--Continued 

BENBOW AREA--Continued 

501,840 l. 927,020 MS Pc cumulate with sulfide~ H <10 <4 <5 

501,720 1,926,900 MS Pc-cpx cumulate H <10 <4 <5 

MOUNTAIN VIEW AREA 

512,840 1,897,020 MS Pc-br cumulate H 17 13 <5 

512,000 1,899,400 MS Pc-br cumulate CH- 45 1 ,2' 19 15 <5 

512,000 1,899,580 MS Pc-br cumulate H tr 8 <5 

513,260 1,899,890 MS Pc cumulate CH-10'1] <10 <4 <5 

513,550 1,900,000 MS Pc cumulate CH-7', l' 

513,560 1,900,000 MS Pc-br-cpx cumulate H <10 <4 <5 

513,830 1,900,480 MS Pc-br-cpx cumulate CH-60'5' <10 <4 <5 

514,510 1,900,940 MS Pc-br-cpx cumulate CH-8' ,0.5' <10 tr <5 

514,510 1,900,940 MS Pc-br-cpx cumulate H <10 <4 <5 

514,550 1,900,990 MS Pc-ol cumulate CH-15' ,0.5' <10 tr <5 

514,540 1,900,990 MS Pc-ol cumulate H <10 <4 <5 

514,550 1,900,990 MS Pc-ol cumulate, altered H <10 <4 <5 

514,560 1,900,990 MS Pc-ol cumulate H <10 <4 <5 

514,560 1,900,990 MS Pc-ol cumulate H <10 <4 <5 

514,590 1,901,030 MS Pc cumulate CH-84',1' <10 <4 <5 

514,590 1,901,030 MS Pc cumulate H <10 <4 <5 

514,590 1,901,030 MS Pc cumulate with sulfides C-30" <10 5 <5 

514,600 l ,901,030 MS Pc cumulate, shear zone H <10 <4 <5 

514,750 1,901,020 MS Pc-br-cpx cumulate CH-40',3' <10 <4 <5 

514,600 1,901,980 MS Pc-br-cpx cumulate H <10 <4 <5 

PICKET PIN PEAK AREA 

531,200 1,859,800 MS Pc cumulate with sulfides CH-15' ,0.5' <10 <4 <5 

GISH AREA 

541,260 1,820,920 MS Br-pc cumulate H <10 7 <5 

11 
Table 3.--APithmetic avePages of Pt, Pd, and Rh, in paPts peP billion, fop zones, membePs, 

and Pock types of the StillwateP Complex, Mont. 

Number 

of 

Zone or rock type---------- samples 

Basal zone-----------------

Ultramafic zone------------

Peridotite member--------

A chromitite-----------

B chromitite-----------

C chromitite-----------

E chromitite-----------

G chromitite-----------

H chromitite-----------

Mil1 concentrates------

Mill tailings----------

1 chromitite-----------

J chromitite-----------

K chromitite-----------

Average chromitite--

Other cumulus rocks----

Bronzitite member--------

Banded and Upper zone------

25 

85 

79 

21 

6 

1 

1 

9 

5 

2 

2 

2 

1 

2 

52 

27 

6 

27 

Arithmetic average 

Pt Pd Rh 

9.4 

286.6 

306.8 

988.9 

144.2 

45 

10 

62.9 

116.2 

36.5 

52 

31 

330 

60 

452.4 

26.4 

21.2 

10.7 

12 

22.9 

601.5 

646.3 

2,290.2 

7 5. 0 

36 

5 

55.0 

41.5 

6. 5 

19 

24 

270 

38 

956.3 

49.2 

12.0 

4.9 

4.8 

91.2 

97.0 

245.9 

98.7 

42 

11 

50.4 

70.3 

35.5 

61 

30.5 

190 

43.5 

137.6 

18.9 

14.2 

4.8 

Sum of 

averages 

Pt+Pd+Rh 

37.1 

979.3 

1,050.1 

3,525.0 

317.9 

123 

26 

168.3 

228.0 

7 8. 5 

132 

85. 5 

790 

141.5 

1,546.3 

94.5 

47.4 

20.4 

Range of 

l:(Pt+Pd+Rh) 

12-118 

4-20 '700 

4-20 '700 

227-20,700 

124-890 

61-7 38 

76-538 

76-81 

125-139 

41-130 

51-2 3 2 

41-20,700 

4-328 

30-63 

19-39 

GPO 87 5·9 41