Chalcostibite

Formula:  CuSbS₂

Origin of name:  From composition, chalkos - copper stibium - antimony

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:  On {104}

Unit cell: a  = 6.016 Ǻ, b = 14.51 Ǻ, c = 3.800 Ǻ

Colour:  Dark lead-gray to iron-gray, occasionally with a blue or green tarnish

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Crystals prismatic, flattened, striated parallel to elongation; massive, granular

Hardness:  3 to 4

Specific gravity:  4.8 to 5.0

Cleavage:  3; {010} perfect, {001} and {100} imperfect

Tenacity:  Subconchoidal; brittle

Streak:

Synonyms/varieties:

Comments: Found with other sulfosalts and sulfides in hydrothermal veins