Min. [a. G. quarz (first in MHG.) of uncertain origin: hence also Du. kwarts, F. quartz, It. quarzo.]
1. A widely diffused mineral, massive or crystallizing in hexagonal prisms; in a pure form consisting of silica or silicon dioxide (SiO2), but varying greatly in color, luster, etc., according to the different impurities it contains.
Quartz forms the rocks quartzite and sandstone, and is an important constituent in granite, gneiss, and other rocks. It frequently contains gold, and is largely mined and crushed for the purpose of extracting this metal (cf. quots. in 2). The numerous varieties are chiefly denoted by adjs. descriptive of their structure or color, as (1) amorphous, asteriated (star-quartz), capped, cavernous, compact, (crypto-) crystalline, fibrous, grained, radiated, sagenitic, sparry, etc., (2) blue (siderite or sapphire-quartz), brown or smoky (cairngorm, morion), green (chrysoprase, prase), milky (milk-quartz), purple (amethyst), red, rose, yellow (citrine), etc.; also Babel or Babylonian quartz, found in Devonshire, showing on its under-surface the impression of the crystals of fluor-spar on which it was deposited. The colorless crystalline variety is known as ROCK-CRYSTAL.
1756. Observ. Isl. Scilly, 71. White debas’d Crystal (which the Germans call Quartz).
1772. trans. Cronstedt’s Min., 57. I shall adopt this name of quartz in English as it has already gained access into other European languages.
1831. Brewster, Optics, xvii. § 94. 151/2. Among the crystals best fitted for exhibiting the phenomena of positive double refraction is rock crystal or quartz.
1859. R. F. Burton, Centr. Afr., in Jrnl. Geog. Soc., XXIX. 107. Boulders of primitive formation, streaked with snow-white quartz.
1879. Rutley, Stud. Rocks, x. 150. Quartz is infusible before the blowpipe, insoluble in all acids except fluoric acid.
2. attrib. and Comb.
a. attrib. in sense ‘consisting of quartz,’ or ‘containing quartz,’ as quartz-boil (see quot. 1869), -crystal, -gritstone, -lode, -pebble, -porphyry, -reef, -rock, -sand, -schist, -slate, vein, etc.
1789. Saunders, in Phil. Trans., LXXIX. 82. It is known to mineralists in that state by the name of quartz gritstone.
1802. Playfair, Illustr. Hutton. Th., 167. Vertical strata much intersected by quartz veins. Ibid., 326. Granites containing quartz-crystals.
1833. Lyell, Princ. Geol., III. 367. Beds of pure quartz rock.
1843. Portlock, Geol., 170. Mica slate passing into quartz slate.
1859. R. B. Smyth, Gold Fields Victoria, 283. Quartz reefs are richer as they increase in depth. Ibid., 618. Quartz-boil, an outcrop of a quartz reef on the surface, or an outburst or extension in width of the reef beneath it.
1877. Raymond, Statist. Mines & Mining, 218. Very little work has been done … on quartz-lodes.
b. attrib. in other senses, obj., and obj. gen., chiefly in terms relating to the extraction of gold from quartz, as quartz-battery, -crusher, -crushing adj., -gold (see quot. 1874), -mill, -mining, -prospecting, -reefing (= mining), etc.
1861. Mrs. Meredith, Over the Straits, iv. 133. Quartz-reefin’s the payinest game, now.
1872. Raymond, Statist. Mines & Mining, 17. Some gold quartz-mining enterprises have been in operation. Ibid. (1874), 317. It is largely ‘quartz gold,’ that is, not rounded and water-worn, but irregular and frequently twisted in form, usually very bright, and always of fine quality, as is the gold of the quartz-veins. Ibid. (1877), 220. The discovery … of quartz-claims in the district. This action gave an impetus to quartz-prospecting.
1882. Rep. to Ho. Repr. Prec. Met. U.S., 596. Quartz-crushing machines yet to be invented.
