Dervillite

Formula:  Ag₂AsS₂

Origin of name:  For Henri Derville, French academic, Strasbourg University, Strasbourg

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 6.833 Å, b = 12.932 Å,  c = 9.638 Å, β = 99.33°

Colour:  Black

Diaphaneity:  Opaque

Luster:  Metallic

Habit:  Crystals, minute to 0.3 mm

Hardness:  1 to 1.5

Specific gravity:  5.62

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:

Comments: Found in a Co-Ni-Fe-As deposit