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Formula: Ag3SbS3
Sulphosalt, proustite group, the low-temperature monoclinic
paramorph of trigonal
pyrargyrite and monoclinic
pyradoketosite
Crystal System: Monoclinic
Specific gravity: 5.94 measured, 5.97 calculated
Hardness: 2
Streak: Orange-yellow
Colour: Red
Environments
Pyrostilpnite occurs in low-temperature hydrothermal veins as a late-stage mineral. Associated minerals include
pyrargyrite, stephanite,
acanthite, silver,
miargyrite, xanthoconite,
andorite and fizelyite
(HOM).
Localities
At the Silver tunnel, Van Silver Property, Brandywine Creek, Vancouver Mining Division, British Columbia, Canada,
pyrostilpnite is common but crystals are only up to 0.6 mm in size. It is one of the last minerals to
crystallise and has been observed on most other minerals; it often grows from cracks in
sphalerite
(Minrec 31.3.228). Pyrostilpnite is stable only below about 192°C
(Mindat).
The type locality is the Churprinz Friedrich August Erbstolln mine, Großschirma, Mittelsachsen, Saxony, Germany.
At the Rand Mine, Red Mountain, Rand Mining District, San Bernardino county, California, USA, pyrostilpnite
has been found in small amounts among the silver minerals. A specimen has been
found composed largely of a vein of massive miargyrite. The vugs are lined
with a botryoidal coating of cervantite. There is also a considerable amount
of cervantite here as a coating of microscopic crystalline grains, usually
surmounting the amorphous crust.
Partly on this coating, and partly enveloped by it, occur sparsely scattered grains and crystals of pyrostilpnite,
and also a few crystals of pyrargyrite. The crystals of pyrostilpnite
are all very small, ranging in length from 0.5 to 0.1 mm
(AM 26(2).130-132).
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