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APLITE , in See also:petrology, the name given to intrusive See also:rock in which See also:quartz and See also:felspar are the dominant minerals. Aplites are usually very See also:fine-grained, 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, See also:grey or flesh-coloured, and their constituents are visible only with the help of a magnifying See also:lens. Dykes and threads of aplite are very frequently to be observed traversing granitic bosses; they occur also, though in less See also:numbers, in syenites, diorites, quartz-diabases and gabbros. Without doubt they have usually a genetic See also:affinity to the rocks they intersect. The aplites of See also:granite areas, for example, are the last See also:part of the magma to crystallize, and correspond in See also:composition to the quartzo-felspathic aggregates which frll up the interspaces between the See also:early minerals in the See also:main See also:body of the rock. They See also:bear a considerable resemblance to the eutectic mixtures which are formed on the cooling of solutions of See also:mineral salts, and remain liquid till the excess of either of the components has separated out, finally solidifying en masse when the proper proportions of the constituents and a suitable temperature are reached. The essential components of the aplites are quartz and See also:alkali felspar (the latter usually See also:orthoclase or microperthite). See also:Crystallization has been appal., ently rapid (as the rocks are so fine-grained), and the ingredients have solidified almost at the same See also:- TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
- TIME, MEASUREMENT OF
- TIME, STANDARD
time. Hence their crystals are rather imperfect and See also:fit closely to one another in a sort of fine See also:mosaic of nearly equi-dimensional grains. Porphyritic felspars occur occasionally and quartz more seldom; but the relation of the aplites to quartz-porphyries, granophyres and felsites is very See also:close, as all these rocks have nearly the same chemical composition. Yet the aplites associated with diorites and quartz-diabases differ in See also:minor respects from the See also:common aplites, which accompany granites. The See also:accessory minerals of these rocks are principally See also:oligoclase, See also:muscovite, See also:apatite and See also:zircon. See also:Biotite and all ferromagnesian minerals rarely appear in them, and never are in considerable amount. Riebeckitegranites (paisanites) have close See also:affinities to aplites, shown especially in the prevalence of alkali felspars. See also:Tourmaline also occurs in some aplites. The rocks of this See also:group are very frequent in all areas where masses of granite are known. They See also:form dykes and irregular See also:veins which may be only a few inches or many feet in See also:diameter. Less frequently aplite forms See also:stocks or bosses, or occupies the edges or ,irregular portions of the interior of outcrops of granite. The See also:syenite-aplites consist mainly of alkali felspar; the See also:diorite-aplites of See also:plagioclase; there are See also:nepheline-bearing aplites which intersect some elaeolite-syenites. In all cases they bear the same relation to the See also:parent masses. By increase of quartz aplites pass gradually, in a few localities, through highly quartzose modifications (beresite, &c.) into quartz veins. (J. S.
End of Article: APLITE
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