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MIMETITE , a See also:mineral consisting of See also:lead chloro-arsenate, '(PbCl)Pb4(AsO4)3, crystallizing in the hexagonal See also:system and closely resembling See also:pyromorphite (q.v.) in See also:appearance and See also:general characters. The See also:arsenic is usually partly replaced by See also:equivalent amounts of See also:phosphorus, and there may thus be a See also:gradual passage from mimetite to pyromorphite. The two See also:species can, as a See also:rule, only be distinguished by chemical See also:analysis, and because of their See also:close resemblance the less frequently occurring chloro-arsenate was named mimetite or mimetesite, from Gr. µiµgrns, imitator. Crystals of pyromorphite though usually optically uniaxial are sometimes biaxial, but in mimetite this anomalous See also:character is almost always See also:present; a See also:cross-See also:section of a hexagonal See also:prism of mimetite shows a See also:division into six optically biaxial sectors or a complex lamellated structure. In See also:colour mimetite is usually yellow or 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, rarely See also:- WHITE
- WHITE, ANDREW DICKSON (1832– )
- WHITE, GILBERT (1720–1793)
- WHITE, HENRY KIRKE (1785-1806)
- WHITE, HUGH LAWSON (1773-1840)
- WHITE, JOSEPH BLANCO (1775-1841)
- WHITE, RICHARD GRANT (1822-1885)
- WHITE, ROBERT (1645-1704)
- WHITE, SIR GEORGE STUART (1835– )
- WHITE, SIR THOMAS (1492-1567)
- WHITE, SIR WILLIAM ARTHUR (1824--1891)
- WHITE, SIR WILLIAM HENRY (1845– )
- WHITE, THOMAS (1628-1698)
- WHITE, THOMAS (c. 1550-1624)
white or colourless; the lustre is resinous to adamantine. The hardness is 32f and the specific gravity 7.0—7.25. Like pyromorphite, mimetite is found in the upper parts of See also:veins of lead ore, where it has been formed by the oxidation of See also:galena and See also:mispickel. When found in large amount it is of importance as an ore of lead. The best crystallized specimens are those from Johanngeorgenstadt in See also:Saxony and Wheal Unity in See also:Cornwall. It was formerly found in considerable amount at Dry Gill in See also:Cumberland, as six-sided See also:barrel-shaped crystals of a brownish-red or See also:orange-yellow colour and containing a considerable proportion of phosphoric See also:acid; this variety has been called campylite, from Gr. KaµauXos, curved, on See also:account of the remarkable curvature of the faces of the crystals. (L. J.
End of Article: MIMETITE
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