Cuprobismutite

Formula:  Cu₁₀Bi₁₂S₂₃

Origin of name:  From copper (Latin cuprum) and bismuth

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 17.520 Å, b = 3.926 Å, c = 15.261 Å, β = 100.18°

Colour:  Dark bluish-black

Diaphaneity:  Opaque

Luster:  Metallic

Habit:  Thin blades slightly twisted parallel [010] (elongation axis), prismatic crystals, massive

Hardness:

Specific gravity:  6.31 to 6.47

Cleavage:

Tenacity:

Streak:  Black

Synonyms/varieties:

Comments: Found in quartz veins with other sulphides