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Formula: Pb2Bi2S5
Sulphosalt of lead and bismuth
Crystal System: Orthorhombic
Specific gravity: 6.86 to 6.99 g/cm3 measured, 7.12 calculated
Hardness: 2½ to 3
Streak: Black
Colour: Grey
Common impurities: Cu,Fe
Environments
Pegmatites
Metamorphic environments
Hydrothermal environments
Cosalite occurs in hydrothermal deposits formed at medium temperatures and is also found in
contact metasomatic replacements, epithermal replacements, and
also in pegmatites. Associated minerals include
sphalerite, chalcopyrite,
pyrite, skutterudite,
cobaltite, bornite,
enargite, stromeyerite,
bismuth, bismuthinite,
calcite, tremolite,
diopside, epidote and
quartz
(HOM).
Localities
At the Wolfram pipe, Kingsgate, Gough county, New South Wales, Australia, cosalite occurs as a minor phase
associated with galena,
galenobismutite and native
bismuth. Cosalite also carries inclusions of
bismuth and bismuthinite. XRD
analysis has also identified intergrowths of cosalite with kobellite
(AJM 14.1.21).
At the Cariboo Gold Quartz Mine, Wells, Cariboo Mining Division, British Columbia, Canada, cosalite is
relatively well known in association with gold
(R&M 96.3.218).
At Lauriéras, Saint-Yrieix-la-Perche, Limoges, Haute-Vienne, Nouvelle-Aquitaine, France, cosalite occurs with
gold and arsenopyrite
(R&M 96.3.218).
At the Trepča Stari Trg mine, Trepča complex, Trepča valley, Mitrovica, Mitrovica District, Kosovo, lustrous
steel-grey to lead-grey acicular cosalite crystals up to 2 cm long were found in a void in a mass of
pyrrhotite, pyrite and
marcasite, coated by calcite and
galena
(Minrec 38.4.281-283).
The type locality is the Cosalá mine, Cosalá, Cosalá Municipality, Sinaloa, Mexico.
At the Bessie G mine, La Plata Mining District, La Plata county, Colorado, USA, cosalite occurs with
tellurides
(R&M 96.3.218).
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