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pentlandite , pentlandite An iron and nickel sulphide, with the formula (FeNi)9S8, and the main ore mineral for nickel; sp. gr. 4.5–5.0; hardness 3–4; cubic; light… Cuprite , cuprite (red copper ore) Mineral, Cu2O; sp. gr. 5.8–6.1; hardness 3.5–4.0 cubic; red to nearly black; brownish-red streak; adamantine to sub-metallic… wolframite , wolframite Ore mineral for tungsten, with the formula (Fe,Mn)WO4; sp. gr. 7.0–7.5; hardness 5.0–5.5; monoclinic; grey-black to brownish-black; browni… Pyrrhotite , pyrrhotite Mineral, FeS; sp. gr. 4.6–4.7; hardness 3.5–4.5; hexagonal; bronzeyellow but darkens rapidly to reddishbrown on exposure; greyish-black st… Uraninite , uraninite (pitchblende) Mineral, UO2; sp. gr. from 8.5 when massive to 10 for unaltered crystals; hardness 5–6; cubic; it is brownish-black or grey-b… ilmenite , ilmenite Mineral, FeTiO3; sp. gr. 4.5–5.0; hardness 5–6; trigonal; black; black to brownish-red streak; sub-metallic lustre; crystals normally thick…
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