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Pearceite
Year of discovery: 1896 (Mollie Gibson mine, USA), 1960 (Japan)
Locality list: 29 localities of pearceite
- Ag15CuAs2S11
- [(Ag,Cu)6(As,Sb)2S7][Ag9CuS4]
- [Ag+6][As3+2][S7]14-,[Ag+9][Cu+][S4]8-
- Color: Black with a red tint
- Streak: Reddish black
- Luster: Metallic
- Diaphaneity: Opaque
- Habit: Pseudohexagonal short tabular
- Aggregate: Rosette
- Striation: Triangle on {001}
- Cleavage: Poor on {001} (1 plane)
- Hardness: 2.5-3
- Density: 6.2
- System: Trigonal (Tac), Trigonal (T2ac, Arsenpolybasite-221), Monoclinic (M2a2b2c, Arsenpolybasite-222) (Layer-stacking polytype)
- Group: (-3)m, P(-3)m1
- Lattice: a=7.4, c=11.9
Etymology: Richard Pearce (1837-1927), American chemist
Synonym: Arsenpolybasite