Arsenpolybasite

Formula:  (Ag,Cu)₁₆(As,Sb)₂S₁₁

Origin of name:  From arsenic and  relationship to polybasite

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: Twin plane {110}, repeated

Unit cell: a = 26.08 Å, b = 15.04 Å, c = 23.84 Å, β = 90°

Colour:  Black

Diaphaneity: Opaque, translucent in thin splinters

Luster:  Metallic

Habit:  Crystals thin tabular, pseudo-hexagonal

Hardness:  2-3

Specific gravity:  6.18 to 6.23

Cleavage:  1; {001}imperfect

Tenacity: Brittle

Streak:  Black

Synonyms/varieties:

Comments:  Series with pearceite. Probably antimonian pearceite. Formed in silver-bearing hydrothermal veins of low to moderate temperature.