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RUTILE , the most abundant of the three native forms of See also: titanium dioxide (TiO2) ; the other forms being See also:anatase (q.v.) and See also:brookite (q.v.). Like anatase, it crystallizes in the tetragonal See also:system, but with different angles and cleavages, it being crystallographically related to cassiterite, with which it is isomorphous. The crystals resemble cassiterite in their prismatic See also:habit and terminal See also:pyramid planes (fig. I) and also in the twinning: the See also:prism planes are striated vertically. Geniculated twins, with e (ior) as twin-See also:plane, are of frequent occurrence, and the twinning is usually several times repeated, giving rise to triplets (fig. 2), sextets and octets. Twin-lamellae are often
See also:present in the crystals. Acicular crystals are sometimes twinned together to See also:form reticulated skeletal plates to which the name " sagenite," from Gr. oayi7vn (a See also:net), is applied. A rarer type of twinning, on the plane (301), gives rise to See also:heart-shaped or See also:kite-shaped forms. There are distinct cleavages parallel to the faces of the prisms m (110) and a (See also:loo). The See also:colour is usually reddish-See also:- BROWN
- BROWN, CHARLES BROCKDEN (1771-181o)
- BROWN, FORD MADOX (1821-1893)
- BROWN, FRANCIS (1849- )
- BROWN, GEORGE (1818-188o)
- BROWN, HENRY KIRKE (1814-1886)
- BROWN, JACOB (1775–1828)
- BROWN, JOHN (1715–1766)
- BROWN, JOHN (1722-1787)
- BROWN, JOHN (1735–1788)
- BROWN, JOHN (1784–1858)
- BROWN, JOHN (1800-1859)
- BROWN, JOHN (1810—1882)
- BROWN, JOHN GEORGE (1831— )
- BROWN, ROBERT (1773-1858)
- BROWN, SAMUEL MORISON (1817—1856)
- BROWN, SIR GEORGE (1790-1865)
- BROWN, SIR JOHN (1816-1896)
- BROWN, SIR WILLIAM, BART
- BROWN, THOMAS (1663-1704)
- BROWN, THOMAS (1778-1820)
- BROWN, THOMAS EDWARD (1830-1897)
- BROWN, WILLIAM LAURENCE (1755–1830)
brown, though yellowish in the very See also:fine needles, and See also:black in the ferruginous varieties (" nigrine " and " ilmeno See also:ruble "): the streak is See also:pale brown. The name rutile, given by A. G. See also: Werner in 1803, refers to the colour, being from the Latin rutilus (red). Crystals are transparent to opaque, and have a brilliant metallic-adamantine lustre. The hardness is 6a and the specific gravity 4.2, ranging, however, up to 5.2 in varieties containing Io% of ferric See also:oxide. The refractive indices and the See also:positive birefringence are high.
Rutile occur's as a See also:primary constituent in eruptive rocks, but more frequently in schistose rocks. As delicate acicular crystals it is often enclosed in See also:mica and See also:quartz: in mica (q.v.) it gives rise to the phenomenon of asterism; and clear transparent quartz (See also:rock-crystal) enclosing rutile is often cut as a See also:gem under the name of " See also:Venus' See also:hair See also:- STONE
- STONE (0. Eng. shin; the word is common to Teutonic languages, cf. Ger. Stein, Du. steen, Dan. and Swed. sten; the root is also seen in Gr. aria, pebble)
- STONE, CHARLES POMEROY (1824-1887)
- STONE, EDWARD JAMES (1831-1897)
- STONE, FRANK (1800-1859)
- STONE, GEORGE (1708—1764)
- STONE, LUCY [BLACKWELL] (1818-1893)
- STONE, MARCUS (184o— )
- STONE, NICHOLAS (1586-1647)
stone " (Veneris crinis of See also:Pliny). Larger crystals occur in the cavities of See also:granite and crystalline See also:schists; very large twinned crystals have been found at See also:Graves See also:Mountain in See also:Lincoln See also:county, See also:Georgia, and See also:good specimens have been obtained from several places in See also:Norway and the Swiss and Ti:olese See also:Alps. As a secondary See also:mineral, rutile in the form of See also:minute needles is of wide See also:distribution in various sedimentary rocks, especially See also:clays and slates. As rounded grains it is often met with in auriferous sands and gravels. The mineral has little economic value: it has been used for imparting a yellow colour to See also:glass and See also:porcelain. and for this purpose is See also:mined at Risor and other places in Norway: (L. J.
End of Article: RUTILE
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