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Enargite (Photo) [abbr. Eng ]

Year of discovery: 1850 (San Francisco vein, Peru), 1915 (Japan)

Locality list: 63 localities of enargite

• Cu₃AsS₄
• [Cu²⁺₃][As³⁺][S₄]

• Class: Sulfide
• Insoluble in: HCl

• Polymorph: Luzonite (Tetragonal)

• As => Sb: Famatinite
• As => In: Sakuraiite
• As => Sn: Petrukite, Kuramite

• Color: Grayish black
• Tarnish: Dull black
• Streak: Black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Tabular on {001}, Prismatic elongated to {001}
• Striation: [001] on pyramidal faces
• Twin: {320} common, Intrusion twin to form pseudohexagonal crystal

• Cleavage: Perfect on {110} (1 plane), Distinct on {100} and {010} (2 planes)
• Hardness: 3
• Density: 4.5

• System: Orthorhombic, Pseudohexagonal (Intrusion twin)
• Group: mm2, Pmn2₁
• Lattice: a=7.4, b=6.4, c=6.2

Etymology: Enarges (clear) in Greek, as its cleavage is distinct.