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Formula: TlAg2(As,Sb)3S6
Sulphosalt, thallium-, silver-,
arsenic- and antimony- bearing mineral
Crystal System: Orthorhombic
Specific gravity: 5.26 calculated
Hardness: 3
Streak: Dark brown-red
Colour: Dark grey, black
Environments
Metamorphic environments
Hydrothermal environments
Localities
At the type locality, the Lengenbach Quarry, Fäld, Binn, Goms, Valais, Switzerland, sicherite occurs in small
cavities
in a dolomitic rock, associated with abundant
realgar and various other sulphosalts, mainly
thallium-bearing species such as
hutchinsonite, hatchite and
jentschite.
Individual crystals of sicherite reach approximately 0.4 mm, but aggregates may exceed 1–2 mm. Sicherite,
as
well as the other thallium minerals in Lengenbach, presumably represent
products of
a late stage activity of thallium- and
arsenic- bearing hydrothermal solutions during metamorphism
(AM 86.1087-1093).
Gabrielite is another
thallium-bearing mineral found at this locality, visually indistinguishable from
sicherite
(CM 44.135-140).
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