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Mckinstryite

Year of discovery: 1966 (Foster mine, Canada), 1971 (Japan)

Locality list: 10 localities of mckinstryite

• Ag₅Cu₃S₄
• Ag_5-xCu_3+xS₄
• [Ag⁺₅][Cu⁺₃][S₄]^8-
• X=0-0.28

• Class: Sulfide

• Ag => Cu: Chalcocite

• Cu => Ag: Argentite, Acanthite

• Ag₅Cu₃ => Ag₆Cu₂: Jalpaite

• Ag₅Cu₃ => Ag₄Cu₄: Stromeyerite

• Color: Dark gray
• Tarnish: Grayish black-Black
• Streak: Grayish black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Granular

• Cleavage: Indistinct (1 plane)
• Hardness: 1.5-2.5
• Density: 6.6

• System: Orthorhombic
• Group: mmm, Pnma
• Lattice: a=14.0, b=7.8, c=15.7

Etymology: Professor Hugh Exton McKinstry (1896-1961), American Geologist