Mineral description : Boulangerite

Boulangerite from Nasafjäll silver mine, Lappland.

Mineral class	Sulphides : Tetrahedrite bournonite boulangerite group
Chemical formula	Pb5Sb4S11
Crystal system	Monoclinic
Habitus	Crystals rare, mostly as radiating and fibric masses.
Cleavage	Good, fracture uneven.
Hardness	2.5-3
Density	5.8-6.2
Color	Led gray to bluish gray.
Streak	Brownish black.
Luster	Dull or metallic
Description
Occurance	In hydrothermal veins.
Associates	Galena, pyrite, sphalerite, tetrahedrite, tennantite, proustite, quartz.
Notes	Fuses very easily. Does not react with cold weak acids, but dissolves in hot strong acids.
Locations	A rare mineral in Sweden. Nasafjäll silver mine, Lappland. Common as fibric masses with galena and sphalerite. Rusty tarnish. Sala silver mine, Västmanland. Used to be a good locality. As fibric masses in a grainy mixture of galena and sphalerite. Also in dolomite. Also found in Boliden, Rakkejaur and Stekenjokk.

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