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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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