Rutile

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

Rutile on pyrophyllite from Mono County, Calif.

(credit: B.M. Shaub)

Commercially important titanium mineral (titanium dioxide, TiO₂). It forms red to reddish brown, hard, brilliant metallic, slender crystals. Rutile has minor uses in porcelain and glass manufacture as a colouring agent and in making some steels and copper alloys. It is also used as a gem, but synthetic rutile is actually superior to natural crystals for gem use; it has fire (flashes of colour) and brilliance (light deflection) like those of diamond. Rutile is mined in Norway and is widespread in the Alps, the southern U.S., Mexico, and elsewhere.

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rutile [′rü‚tēl]

(mineralogy)

TiO₂A reddish-brown tetragonal mineral common in acid igneous rocks, in metamorphic rocks, and as residual grain in beach sand.

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rutile

A common mineral, red-to-brown or black in color; contains 60% titanium; used in paints, as a coating on welding rods to stabilize the arc, and as an opacifier in ceramic glaze and in glass.

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Rutile 

a mineral, one of the three polymorphs of titanium dioxide (titania), TiO₂. It contains iron, chromium, and sometimes vanadium, niobium, and tantalum as admixtures. The structure of rutile differs from that of the other two polymorphs of TiO₂—ana tase and brookite—in the nature of the coupling of the octahedral [TiO₆] groups, which are connected to each other by two common edges, forming chains parallel to the c-axis. The c-axis lies in a plane corresponding to layers of close hexagonal packing. Rutile crystallizes in the tetragonal system. It is a semiconductor and is antiferromagnetic. It has a hardness of 6–6.5 on Mohs’ scale, and its density ranges from 4,200 to 5,600 kg/m³, depending on the content of niobium and tantalum. Pure rutile is colorless, but the mineral is almost always found in various tints as a result of various admixtures.

Rutile is a common accessory mineral in rocks. In pegmatites and hydrothermal veins it occurs as large prismatic or acicular crystals. Rutile-bearing quartzites and chloritic, graphitic, and other schists have industrial value as titanium ores. Rutile is also accumulated in placers, which are especially valuable ores. Synthetic rutile is used in the jewelry industry.

REFERENCE

Mineraly: Spravochnik, vol. 2. Moscow, 1965.