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Polybasite

Year of discovery: 1829 (World), 1894 (Japan)

Locality list: 65 localities of polybasite

• Ag₁₅CuSb₂S₁₁
• [(Ag,Cu)₆(Sb,As)₂S₇][Ag₉CuS₄]
• [Ag⁺₆][Sb³⁺₂][S₇]^14-,[Ag⁺₉][Cu⁺][S₄]^8-

• Class: Polybasite group < Ag sulfosalts < Sulfosalt class
• Class: Sulfosalt
• Insoluble in: HCl

• Ag => Cu: Cupropolybasite

• Sb => As: Pearceite (Series)

• S => Se: Selenopolybasite

• Color: Black with a red tint
• Streak: Black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Pseudohexagonal, platy on {001}
• Striation: Triangle on {001}
• Twin: {110}

• Cleavage: Imperfect on {001} (1 plane)
• Hardness: 2.5-3
• Density: 6.1

• System: Trigonal (Tac, Antimonpearceite), Trigonal (T2ac), Monoclinic (M2a2b2c) (Layer-stacking polytype)
• Group: 2/m, C2/m
• Lattice: a=26.2, b=15.1, c=23.9, β=90.0

Etymology: Poly (many) and Bas (base) in Greek.