Hollingworthite

hollingworthite

sperrylite

geversite

irarsite

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Formula: RhAsS
Sulphide, cobaltite group, forms a series with irarsite, arsenic and rhodium bearing mineral
Crystal System: Isometric
Specific gravity: 7.86 calculated
Hardness: 6 to 6½
Colour: Medium grey
Common impurities: Pt,Ir,Ru,Fe
Environments

Plutonic igneous environments
Pegmatites

Hollingworthite occurs in platinum deposits in dunite pipes, layered ultramafic intrusives, chromitites and in copper-nickel sulphide ores (HOM).

Localities

At the Bird River Sill, Manitoba, Canada, hollingworthite occurs from platinum group mineral parageneses with magnetite and with serpentine and pentlandite interstitial to chromite (AM 76.1694-1700).

At the Two Duck Lake intrusion, Coldwell complex, Thunder Bay District, Ontario, Canada, hollingworthite was found in close association with chalcopyrite in coarse-grained to pegmatitic olivine gabbro. The hollingworthite is complexly zoned. Iridium and arsenic rich hollingworthite is progressively zoned to pure hollingworthite followed by partial dissolution, replacement, and overgrowth; the processes have caused the replacement of up to half of the rhodium atoms by osmium and ruthenium and, in one of the grains, of 0.4 of the arsenic atoms by sulphur. This type of zoning cannot result from simple exsolution of hollingworthite from interstitial magmatic sulphide; it is interpreted to reflect the effects of fluids that may have transported and precipitated different proportions of the platinum group elements at different times (AM 76.1694-1700). Associated minerals include chalcopyrite, cobaltite, gersdorffite and pyrrhotite (HOM).

At Østhammeren, Røros, Trøndelag, Norway, hollingworthite occurs in chromite (AM 76.1694-1700).

At the type locality, the Driekop mine, Sekhukhuneland, Burgersfort, Fetakgomo Tubatse Local Municipality, Sekhukhune District Municipality, Limpopo, South Africa, hollingworthite occurs as small grains, with maximum diameter about 40 microns, closely intergrown with rhodium-rich sperrylite, rhodium-free sperrylite and geversite. Other associates include erlichmanite, irarsite and platinum-iron alloys (AM 50.1068-1074, HOM)

At the Stillwater Complex, Montana, USA, hollingworthite is associated with a gold-silver alloy, braggite, sperrylite, cobaltite, pyrrhotite, pentlandite, pyrite and chalcopyrite (HOM).

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