Argyrodite

Formula:  Ag₈GeS₆

Origin of name:  From Greek for silver containing

Crystal system:  Orthorhombic, pseudocubic

Crystal class:  mm2

Twinning:  Common by spinel law {111}, repeated interpenetration twins of pseudododecahedra on {111}

Unit cell:   a = 15.15 Å, b = 7.48 Å, c = 10.59 Å

Colour:  Steel-gray with reddish tint, tarnishes black with blue tint

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Crystals octahedral, dodecahedral; crystal aggregates, botryoidal crusts, massive

Hardness:  2.5 - 3

Specific gravity:  6.29

Cleavage:  None

Tenacity:  Brittle

Streak:  Grayish black

Synonyms/varieties:

Comments:  Series with canfieldite. Formed in low-temperature poly-metallic deposits with silver sulphosalts, in high-temperature Sn-Ag deposits