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ALLOPHANE , one of the few minerals known only in the amorphous See also:state. It is a glassy substance, usually occurring as thin encrustations with a mammillary See also:surface; occasionally, however, it is earthy and pulverulent. The See also:colour varies considerably, from colourless to yellow, 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, See also:blue or See also:green. Specimens of a brilliant See also:sky-blue colour, such as those found formerly in Wheal Hamblyn, near Bridestowe in See also:Devonshire, and in See also:Sardinia, are specially attractive in See also:appearance; the colour is here due to the presence of the See also:copper See also:mineral See also:chrysocolla. The hardness is 3, and the specific gravity 1.9. Chemically, it is a hydrous See also:aluminium silicate, Al,SiO5. 5H2O. Allophane is always of secondary origin, resulting from the decomposition of various aluminous silicates, such as See also:felspar. It is often found encrusting fissures and cavities in mines, especially those of copper and See also:iron. It was first observed in I$09 in See also:marl at Grafenthal, near Saalfield in Thuringia; and has been found in some quantity in the See also:chalk pits at Charlton in See also:Kent, where it lines fissures and See also:funnel-shaped cavities. The name allophanewas given by F. Stromeyer in 1816, from the Gr. iiXAos, another, and rpaivw, to appear, in allusion to the fact that the mineral crumbles and changes in appearance when heated before the See also:blowpipe. Other names for the See also:species are riemannite and elhuyarite, whilst closely allied minerals are carolathine, samoite and schrStterite (See also:opal-allophane).
End of Article: ALLOPHANE
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