Mineral description : Acanthite

Picture pending, acanthite from Garpenberg.

Mineral class	Sulphides : Argentite group
Chemical formula	Ag2S
Crystal system	Monoclinic
Habitus	Crystals rare, as pseudocubic crystal groups. Mostly as crusts, dendritic or in massive form.
Cleavage	[001] poor, [110] poor. Bendable, mallable and cuttable.
Hardness	2 - 2.5
Density	7.3
Color	Led gray, opaque.
Streak	Shiny gray.
Luster	Metallic.
Description
Occurance	Formed in low temperature hydrothermal veins. Also in the concentration zone in silver deposits.
Associates	Silver, Galena.
Notes	Often with dull black tarnish. When heated to glowth, metallic silver is formed. Acanthite is the stable form below 179° C of the cubic argentite.
Localities	A not so common mineral in Sweden but found in a number of silver mines. Harmsarvet, Grycksbo, Dalarna. Together with silver. Garpenberg Norra, Dalarna. Pauträsk, Storuman, Lappland. Nordmark, Filipstad, Värmland. Sala silver mine, Västmanland. Mostly microscopic in galena, making up the most of the silver contents of the ore.

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