Pyrargyrite

Formula: Ag₃SbS₃

Origin of name: from Greek for fire and silver

Crystal system: hexagonal

Crystal class: 3m

Twinning: common on {10-14} repeated, lamellar, less common on {10-11} or about [11-20] axis, rare on {01-12}

Unit cell: a = 11.05 Å, c = 8.72 Å

Colour: deep red

Diaphaneity: 

Luster: adamantine

Habit: crystals prismatic, hemimorphism sometimes distinct, or steep scalenohedral, massive, compact, disseminated

Hardness: 2.5

Specific gravity: 5.85

Cleavage: 2; {10-11} distinct, {01-12} indistinct

Tenacity: 

Streak: dark red

Synonyms/varieties: ruby silver

Comments: dimorphous with pyrostilpnite