Niccolite

niccolite [′nik·ə‚līt]

(mineralogy)

NiAs A pale-copper-red, hexagonal mineral with metallic luster; an important ore of nickel; hardness is 5-5.5 on Mohs scale. Also known as arsenical nickel; copper nickel; nickeline.

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Niccolite 

(also copper nickel), a mineral, a nickel arsenide whose chemical composition is NiAs. Niccolite frequently contains Co, Fe, Sb, and other admixtures. The mineral is opaque and has a metallic luster and a characteristic copper-red color. It crystallizes in the hexagonal system and usually forms compact granular or columnar masses. The mineral has a hexagonal closely packed crystal structure. Ni occupies the center of octahedral vacancies and is surrounded by six As ions; each As ion is surrounded by six Ni ions according to the symmetry of a trigonal prism. The mineral has a hardness of 5 on Mohs’ scale and a density of 7,600–7,800 kg/m³.

Niccolite is usually found in quartz-carbonate hydrothermal ore veins together with other arsenides of nickel and cobalt, as well as with native bismuth, silver, and other metals. Niccolite is readily weatherable in the oxidation zone and is transformed into the bright green secondary mineral annabergite, Ni[AsO₄]₂ • 8H₂0. The mineral is found in the USSR in the Berikul’skii gold deposits (Kemerovo Oblast) and in the cobalt deposits of Khovu-Aksy (Tuva ASSR). Niccolite is also found in the German Democratic Republic (Schneeberg in Saxony, Mansfeld in Thuringia, and other locations), the USA, Canada, and other countries. When found in large deposits, the mineral serves as an ore for the production of nickel.