What is Millerite?
Millerite is one of the most dramatic acicular sulfides. Fine golden sprays can cover a cavity like metallic grass, revealing both the geometry of crystal growth and the chemistry of a nickel-rich environment.
Mineralogy and crystal structure
Reference formula: NiS. Millerite is a trigonal nickel sulfide famous for delicate hairlike sprays and radiating needles. It can alter to nickel sulfates or oxides, and its nickel-bearing composition makes analytical confirmation and careful handling advisable. Millerite is classified with sulfides and has a trigonal crystal system. Typical hardness is 3–3.5 on the Mohs scale and specific gravity is approximately 5.3–5.6.
Colour, lustre and habit
Typical colours include brass-yellow, bronze-yellow, greenish-yellow. The usual needle-like, hairlike, radiating habit and metallic lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Millerite forms in or is associated with nickel sulfide deposits, meteorite-related assemblages, coal seams and low-temperature hydrothermal cavities. Important documented localities include Canada, Germany, the United States, Russia, Italy and Australia.
Golden needles with a nickel story
Millerite is one of the most dramatic acicular sulfides. Fine golden sprays can cover a cavity like metallic grass, revealing both the geometry of crystal growth and the chemistry of a nickel-rich environment.
Collecting and care
Protect fragile needles from vibration and abrasion; avoid dust and acids.
