What is Violarite?
Violarite is a violet-black nickel-iron sulfide commonly formed by alteration of pentlandite in weathered nickel deposits.
Mineralogy and structure
Reference formula: FeNi2S4. Violarite has a cubic spinel-related structure and commonly occurs as fine-grained replacement material. The exact COD 9000978 model is used; a violet sheen alone is not diagnostic. Violarite is classified with sulfides and has cubic crystal symmetry. Typical hardness is 4.5–5 on the Mohs scale and specific gravity is approximately 4.5–4.8.
Colour, lustre and habit
Typical colours include violet-black, black, bronze, grey. The usual granular, massive, crusty habit and metallic, sub-metallic lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Violarite forms in or is associated with supergene alteration zones of nickel sulfide ores, ultramafic rocks and mine weathering profiles. Important documented localities include Canada, Australia, Norway, Russia, South Africa and the United States.
Violet-black alteration in a nickel ore
Violarite is valued by specialists because its colour and texture record the transformation of a nickel sulfide ore. A good specimen pairs the violet surface with clear host-rock and locality information.
Collecting and care
Keep dry and enclosed, avoid dust, acids and grinding, and treat nickel-bearing sulfide as an ore specimen.
