Canfieldite

Formula:  Ag₈SnS₆

Origin of name:  For Frederick A. Canfield (1849-1926), American mining engineer and mineral collector from Dover, New Jersey

Crystal system:  Orthorhombic, pseudo-cubic

Crystal class:  mm2

Twinning:  Common on {111} by Pseudo-spinel law or penetration twins of pseudo-dodecahedra

Unit cell: a = 15.30 Ǻ, b = 7.548 Ǻ, c = 10.70 Ǻ

Colour:  Steel-gray with reddish tinge; tarnishes black with purple or bluish tinge

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Crystals usually octahedral

Hardness:  2.5

Specific gravity:  6.276

Cleavage:  None

Tenacity:  Conchoidal to uneven; brittle

Streak:  Grayish black

Synonyms/varieties:

Comments:  Series with argyrodite. Occurs in polymetallic veins, formed very late in the paragenetic sequence