Domeykite

Formula:   Cu₃As

Origin of name:   For Ignacio Domeyko (1802-1889), Chilean mineralogist

Crystal system:   Cubic

Crystal class:   -43m

Twinning:

Unit cell: a = 9.62 Å

Colour:   Silver-white to steel-gray, tarnishes yellowish brown or iridescent

Diaphaneity:  Opaque

Luster:   Metallic

Habit:   Massive; botryoidal or reniform

Hardness:   3 to 3.5

Specific gravity:   7.92 to 8.10

Cleavage:   None

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: Hydrothermal origin in association with copper (usually arsenian), silver and algodonite