Bornhardtite

Formula:  CoCo₂Se₄

Origin of name:  For Wilhelm Bornhardt, German mineralogist (1864-?)

Crystal system:  Cubic

Crystal class:  4/m -3 2/m

Twinning:

Unit cell: a = ~10.2 Å

Colour:  Rose-red, pinkish red

Diaphaneity:  Opaque

Luster: Metallic

Habit:  Massive or microscopic rims on trogtalite crystals

Hardness:  ~ 4

Specific gravity:  6.17

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:

Comments: Of hydrothermal origin with trogtalite, hastite, clausthalite