Aramayoite

Formula:  Ag(Sb, Bi)S₂

Origin of name:  For Felix Avelino Aramayo, former Bolivian managing director of the Compagnie Aramayo de Mines en Bolivie

Crystal system:  Triclinic

Crystal class:  -1

Twinning: about [-101] with the composition plane near {-101}

Unit cell: a = 7.72 Å, b = 8.82 Å, c = 8.30 Å, α = 100°23', β = 90°, γ = 103°54'

Colour:  Iron-black

Diaphanity: Nearly opaque

Luster:  Metallic

Habit:  Aggregates thin broad plates parallel to (010), striated along {100} and {001}

Hardness:  2.5

Specific gravity:  5.60

Cleavage:  3; {010} perfect, {100} fair, {001} poor

Tenacity: Sectile

Streak:  Black to red-brown

Synonyms/varieties:

Comments: In vein-controlled hydrothermal tin and silver ores