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Arsenopyrite (Photo) [abbr. Apy ]

Year of discovery: 1847 (World), 1875 (Japan)

Locality list: 717 localities of arsenopyrite

• FeAsS
• (Fe,Co)AsS
• [Fe³⁺][As³⁺][S]

• Class: Arsenopyrite group
• Class: Sulfide
• Variety: Danaite (+Co)
• Insoluble in: HCl
• Magnetism: Paramagnetic (After heating)
• Odor: Garlic (by hitting)
• Formed in high temperature veins.

• Fe => Co: Cobaltite
• Fe => Os: Osarsite
• Fe => Ru: Ruarsite
• Fe => Ni: Gersdorffite
• Fe => Rh: Hollingworthite
• Fe => Pt: Platarsite
• Fe => Ir: Irarsite

• Fe₂ => CoFe: Glaucodot
• Fe₄ => Co₃Fe: Alloclasite

• As => Sb: Gudmundite

• Color: Silver white
• Tarnish: Yellow
• Streak: Grayish black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Prismatic with rhombus cross section, Platy
• Striation: [001]
• Twin: {100}, {001}, Stellate intrusion twin by {101}{012}

• Cleavage: Distinct on {001} (1 plane), Indistinct on {010} (1 plane)
• Hardness: 5.5-6
• Density: 6.1

• System: Monoclinic, Pseudoorthorhombic
• Group: 2/m, P2₁/c
• Lattice: a=5.7, b=5.7, c=5.8, β=112.3

Etymology: As-bearing Pyrite