Cobaltite

Formula:  CoAsS

Origin of name:  From composition

Crystal system:  Orthorhombic, pseudocubic

Crystal class:  mm2

Twinning:   Rare on {011} or {111}

Unit cell: a = 5.582 Ǻ, b = 5.582 Ǻ, c = 5.582 Ǻ

Colour:  Tin-white, steel-gray with violet tint, grayish black

Diaphaneity: Opaque

Luster:  Metallic, brilliant to dull

Habit:  Crystals have isometric forms; massive, granular to compact

Hardness:  5.5

Specific gravity:  6.33

Cleavage:  1; {001} perfect

Tenacity:  Uneven, brittle

Streak:  Greyish black

Synonyms/varieties:

Comments: Found in high-temperature hydrothermal deposits, as disseminations, and as veins in contact metamorphic rocks.