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See also:DACITE (from See also:Dacia, mod. Transylvania) , in See also:petrology, volcanic rocks which may be considered a See also:quartz-bearing variety of See also:andesite. Like the latter they consist for the most See also:part of See also:plagioclase See also:felspar with See also:biotite, See also:hornblende, See also:augite or See also:enstatite, and have generally a porphyritic structure, but they contain also quartz as rounded, corroded phenocrysts, or as an See also:element of the ground-See also:mass. Their felspar ranges from See also:oligoclase to andesite and See also:labradorite, and is often very zonal; sanidine occurs also in some dacites, and when abundant gives rise to rocks which See also:form transitions to the rhyolites. The biotite is 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; the hornblende brown or greenish brown; the augite usually See also:green. The ground-mass of these rocks is often micro-crystalline, with a See also:web of See also:minute felspars mixed with interstitial grains of quartz; but in many dacites it is largely vitreous, while in others it is felsitic or cryptocrystalline. In the See also:hand specimen many of the hornblende and biotite dacites are See also:grey or See also:pale brown and yellow rocks with 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 felspars, and See also:black crystals of biotite and hornblende. Other dacites, especially augite- and enstatite-dacites, are darker coloured. The rocks of this See also:group occur in See also:Hungary, See also:Almeria (See also:Spain), See also:Argyllshire and other parts of See also:Scotland, New See also:Zealand, the See also:Andes, See also:Martinique, See also:Nevada and other districts of western See also:North See also:America, See also:Greece, &c. They are mostly associated with andesites and trachytes, and form See also:lava flows, dikes, and in some cases massive intrusions in the centres of old volcanoes. Among See also:continental petrographers the older dacites (Carboniferous, &c.) are often known
as " porphyrites." (J: S.
End of Article: DACITE (from Dacia, mod. Transylvania)
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