Larosite

General Information: Chemical Formula:(Cu,Ag)21(Pb,Bi)2S13 Composition:(Molecular Weight = 2,256.15 gm)Copper 53.51 % CuSilver 9.56 % AgBismuth 9.26 % BiLead 9.18 % PbSulfur 18.48 % S  Empirical Formula: Cu19Ag2PbBiS13 IMA Status:Approved IMA 1972 Locality:Foster mine, Cobalt, Ontario, Canada. Name Origin:Named for Fed LaRose, a discoverer of silver ore at Cobalt.Physical Properties: Color:black. Density:6.19 Diaphaniety:Opaque Habits:Microscopic Crystals - Crystals visible only with microscopes., Acicular - Occurs as needle-like crystals., Hardness:3-3.5 - Calcite-Copper Penny Luster:MetallicMore details...

(C ,Ag)21(Pb,Bi)2S13