Irarsite(Ir, Ru, Rh, Pt)AsS
c 2001-2005 Mineral Data Publishing, version 1

Crystal Data: Cubic. Point Group: 2/m 3.
hollingworthite or laurite.

As grains, to 1 mm, and intergrown with

Physical Properties:
Tenacity: Brittle. Hardness = Not scratched with a steel needle.
VHN = 976 D(meas.) = n.d. D(calc.) = 11.92
Optical Properties: Opaque. Color: Iron-black; in polished section, grayish white with abluish tint. Luster: Metallic.
R: (400) 47.6, (420) 47.3, (440) 47.0, (460) 46.8, (480) 46.6, (500) 46.4, (520) 46.2, (540) 45.9,(560) 45.6, (580) 45.4, (600) 45.1, (620) 44.9, (640) 44.6, (660) 44.3, (680) 44.0, (700) 43.7
Cell Data:

Space Group: P a3. a = 5.777

Z=1

X-ray Powder Pattern: Onverwacht mine, South Africa.
3.32 (100), 2.87 (100), 1.74 (100), 2.04 (90), 1.112 (90), 2.57 (80), 1.021 (80)
Chemistry:
IrRu
Rh
Pt

(1)
23.0
9.4
7.2
12.6

(2)
43.5
5.5
1.4
11.7

(3)
62.35

(1)
PdCu
AsS

34.5
11.6

(2)
0.4
0.6
26.0
9.6

(3)26.60
11.47

Total 98.3
98.7
100.42(1) Driekop mine, South Africa; by electron microprobe, corresponding to (Ir0.29 Ru0.23 Rh0.17
Pt0.16 )Σ=0.85 As1.12 S0.88 . (2) Papua New Guinea; by electron microprobe, corresponding to(Ir1.01 Ru0.03 Fe0.02 Os0.01 )Σ=1.07 As0.89 S1.11 . (3) Ioma placer, Shetland Islands; by electronmicroprobe, corresponding to Ir0.91 As1.00 S1.00 .
Polymorphism & Series:
Mineral Group:

Forms a series with hollingworthite.

Cobaltite group.

Occurrence: In chromite in hortonolite dunite (South Africa); as inclusions in chrompicotites(Bulgaria); and as rims around Pt-group alloys.
Association: Platinum, ruthenian hollingworthite, sperrylite, laurite, iridarsenite,ruthenarsenite, rutheniridosmine, chalcopyrite, chalcocite, pyrrhotite, cobaltite, gersdorffite,pentlandite, nickeline, magnetite, chromite, olivine.
Distribution: In South Africa, in the Merensky Reef, Bushveld complex, Transvaal, from theOnverwacht [TL] and Driekop mines. At the Hitura Ni–Cu deposit, western Finland. FromVourinos, Greece. In the Pletene chromite deposit, Bulgaria. From the Kapitanov chromite
deposit, near Zvenyhorodka, Ukraine. At Chromwerk, Kraubath ultramafic massif, Styria,Austria. In the Cliff and Harold’s Grave quarries, Shetland Islands. In the USA, from theAmerican River, Sacramento Co., and in the Stanislaus River near Knight’s Ferry, Stanislaus Co.,
California; from Fox Gulch, Goodnews Bay, Alaska. In Canada, at Werner Lake and Sudbury,
Ontario, and the Pipe mine, in Manitoba. From the Anduo chromite deposit, Tibet, China. At
the Baimka placers, Chukota, Far Eastern Region, Russia. From the Ioma placer, Waria River,Yodda goldfield, Papua New Guinea.
Name:For IRidium and ARSenic in the composition.

Type Material:n.d.

References: (1) Genkin, A.D., N.N. Zhuravlev, N.V. Troneva, and I.V. Murav’eva (1966)
Irarsite, a new sulfarsenide of iridium, rhodium, ruthenium, and platinum. Zap. Vses.
Mineral. Obshch., 95, 700–712 (in Russian). (2) (1967) Amer. Mineral., 52, 1580 (abs. ref. 1).
(3) Tarkian, M. and H.M. Prichard (1987) Irarsite-hollingworthite solid-solution series and otherassociated Ru-, Os-, Ir-, and Rh-bearing PGM’s from the Shetland ophiolite complex. Mineralium
Deposita, 22, 178–184. (4) Cabri, L.J., Ed. (1981) Platinum group elements: mineralogy, geology,recovery. Can. Inst. Min. & Met., 110–111. (5) Criddle, A.J. and C.J. Stanley, Eds. (1993)
Quantitative data file for ore minerals, 3rd ed. Chapman & Hall, London, 252.
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