rutile

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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 reddish-brown, but also yellowish-red, or black; pale brown streak; adamantine lustre; crystals normally square prisms terminated by pyramids; cleavage prismatic {110} and {100}; occurs in a variety of igneous rocks, schists, gneisses, and metamorphic limestones and quartzites, and becomes concentrated in alluvial deposits and beach sands. It is an important ore mineral for titanium and its compounds.

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rutile, mineral, one of three forms of titanium dioxide (TiO2; see titanium). It occurs in crystals, often in twins or rosettes, and is typically brownish red, although there are black varieties. Rutile is found in igneous and metamorphic rocks, chiefly in Switzerland, Norway, Brazil, and parts of the United States.

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rutile (titanium dioxide, TiO2) Black to red-brown oxide mineral, found in igneous and metamorphic rocks and quartz veins. It occurs as long, prismatic crystals in the tetragonal system and as granular masses. It has a metallic lustre, is brittle and is used as a gemstone. Hardness 6–6.5; r.d. 4.2.