Skutterudite
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Skutterudite is a cobalt arsenide mineral containing variable amounts of nickel and iron substituting for cobalt with the ideal formula CoAs₃. Some references give the arsenic a variable formula subscript of 2–3. High nickel varieties are referred... Wikipedia
Cleavage: Distinct on, and; in traces on
Color: Tin-white to silver-gray, tarnishes gray or iridescent; in polished section, gray, creamy or golden white
Crystal class: Diploidal (m3); H-M symbol: (2/m 3)
Crystal system: Cubic
Formula (repeating unit): CoAs3
Fracture: Conchoidal to uneven
Luster: Metallic