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a nickel arsenide mineral with chemical composition approximating Ni11As8, assigned to the group of sulfide minerals. It often occurs with niccolite (to which it alters), as at Mansfeld, Ger.; Los Jarales, Malaga, Spain; and Ontario, Can. Its crystals belong to the tetragonal system. It is identical to the furnace product placodine. For chemical formula and detailed physical properties, see sulfide mineral (table)