anatase (octahedrite) Mineral, TiO2; sp. gr. 3.9, hardness 5.5–6.0; tetragonal; yellow, or shades of brown, blue, or black; white streak; vitreous lustre; crystals normally bipyramidal octahedra, but sometimes tabular; cleavage perfect, basal, and pyramidal; occurs as an accessory mineral in metamorphic and igneous rocks, also in hydrothermal veins and granite pegmatites.
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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… Rutile , rutile rutile An accessory mineral, TiO2; iron, niobium, and tantalum may also be present; sp. gr. 4.2–5.6; hardness 6.0–6.5; tetragonal; normally re… Anglesite , wulfenite Mineral, PbMoO4; sp. gr. 6.5–7.0; hardness 3; tetragonal; orange-yellow, olive-green, or brown; white streak; resinous lustre; crystals usu… Titanite , sphene (titanite) A nesosilicate CaTiSiO4 (O,OH,F); sp. gr. 3.45–3.55; hardness 5; crystals wedge-shaped, occasionally massive; brown, grey, reddish… Biotite , biotite biotite An important rock-forming silicate mineral; a member of the mica group K2(Mg,Fe)6[Si3AlO10]2(OH,F)4, in which the Mg/Fe ratio is less… Corundum , corundum Mineral, Al2O3; sp. gr. 3.9–4.1; hardness 9; trigonal; the two main varieties blue and green, but can be yellow, or brown to almost black, a…
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