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Gratonite (Photo)

Year of discovery: 1939 (Excelsior mine, Peru), 1984 (Japan)

Locality list: A locality of gratonite

• Pb₉As₄S₁₅
• [Pb²⁺₉][As³⁺₄][S₁₅]^30-

• Class: Large 2D fragment Pb sulfosalts < Sulfosalt class
• Class: Sulfosalt

• Color: Dark lead black
• Streak: Black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Prismatic elongated to [0001] with end faces {11-20} and {02-21}

• Cleavage: No
• Hardness: 2.5
• Density: 6.2

• System: Trigonal
• Group: 3m, R3m
• Lattice: a=17.8, c=7.8

Etymology: Professor Louis Caryl Graton (1880-1970), economic geologist of Harvard University, USA