What is Népouite?
Népouite is a nickel-rich serpentine-group mineral with vivid green colour, formed in weathered ultramafic rocks and laterite profiles.
Mineralogy and crystal structure
Reference formula: Ni3Si2O5(OH)4. Népouite is the nickel-rich end of the lizardite-nepouite series and natural compositions vary. The selected COD model represents a nickel-rich layered structure, not every sample's exact occupancy. Népouite is classified with silicates and has a monoclinic crystal system. Typical hardness is 2–3 on the Mohs scale and specific gravity is approximately 2.5–2.8.
Colour, lustre and habit
Typical colours include apple-green, yellow-green, brown, white. The usual massive, platy, fibrous habit and waxy, pearly, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Népouite forms in or is associated with nickel laterites, weathered peridotite and hydrothermal alteration of magnesium-rich ultramafic rocks. Important documented localities include New Caledonia, Australia, Brazil, the Dominican Republic and Russia.
Apple-green nickel chemistry in a laterite
Népouite turns tropical weathering into colour. Its green layered material shows how nickel can be concentrated as ultramafic rock is transformed by water and oxygen.
Collecting and care
Soft and dusty when weathered; avoid abrasion, acids and inhaling powder.
