Niccolite

The niccolite called also Niccolite , is a mineral nickel arsenide of NiAs formula, containing 43,9% of Arsenic and 56,1% of Nickel. Minor amounts of Sulfur, Iron and Cobalt are usually present; arsenic can be significantly replaced by the Antimoine.

Niccolite forms a isomorphous series with the Breithauptite. Because of its color copper-red the ore is often called “copper-nickel”: the German equivalent “Kupfernickel” was employed since 1694. The associated ores include: Mispickel, Barytine, Money, Cobaltine, Pyrrhotite, Pentlandite, Chalcopyrite, Breithauptite and Maucherite. In contact with the humid air niccolite gives Pseudomorphose by coating of Annabergite (green Arséniate of Nickel).

Origin

Niccolite is formed by hydrothermal action on ultramafic rocks and the associated layers and can be formed by replacement of nickel-copper sulfides (replacement of the Pentlandite and association with sulfo-arsenides of Cuivre), or by métasomatose of the ultramafic rocks deprived of sulfides, where sulfur, like arsenic and carbonates, are brought by the fluids metasomatic. The result is typically an association which comprehend the Millerite, the Heazelwoodite, the Pentlandite and the Pyrite. Important layers of niccolite and associated minerals are in Ontario and Australia.

Structure

Niccolite has hexagonal structure, Groupe of space P 63/ mmc , hardness of about 5-5 ½ in the scale of Mohs. It is about the hexagonal equivalent of the structure Galène.

Economic importance

Niccolite is seldom employed like source of nickel because of the presence of the arsenic, which is noxious with the majority of the uses. During the deterioration of the nickel sulfide layers, the presence of arsenic makes the ore nonprofitable as soon as the concentration exceeds the few hundreds of parts per million. However, the arsenical nickel ore can be mixed with other ores deprived of arsenic, which gives a content more acceptable for an industrial use.

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