Calaverite

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Calaverite
Platy calaverite crystals on matrix from the Cripple Creek District (size: 6 x 5 x 3.5 cm)
General
Category	Telluride mineral
Formula (repeating unit)	AuTe2
IMA symbol	Clv[1]
Strunz classification	2.EA.10
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 7.19 Å, b = 4.4 Å, c = 5.08 Å; β = 90.3°; Z = 2
Identification
Formula mass	452.17 g/mol
Color	Brass yellow to silver white
Crystal habit	Bladed and slender striated prisms, also massive granular
Twinning	Common on [110]
Cleavage	None
Fracture	Uneven to subconchoidal
Tenacity	Brittle
Mohs scale hardness	2.5–3
Luster	Metallic
Streak	Green to yellow grey
Diaphaneity	Opaque
Specific gravity	9.1–9.3
Optical properties	Anisotropic
Pleochroism	Weak
Ultraviolet fluorescence	None
References	[2][3][4][5]

Calaverite, or gold telluride, is an uncommon telluride of gold, a metallic mineral with the chemical formula AuTe₂, with approximately 3% of the gold replaced by silver. It was first discovered in Calaveras County, California in 1861, and was named for the county in 1868.

The mineral often has a metallic luster, and its color may range from a silvery white to a brassy yellow. It is closely related to the gold-silver telluride mineral sylvanite, which, however, contains significantly more silver. Another AuTe₂ mineral (but with a quite different crystal structure) is krennerite. Calaverite and sylvanite represent the major telluride ores of gold, although such ores are minor sources of gold in general. As a major gold mineral found in Western Australia, calaverite played a major role in the 1890s gold rushes in that area.