petrosilex Min.
(pɛtrəʊˈsaɪlɛks)
[mod.L., f. petr-us stone or petr-a rock + silex flint, pebble; also in Fr. (1753 D'Holbach Min. de Walerius I. 176, in Hatz.-Darm.).]
A hard rock; an early name for compact feldspar, now called Felsite; in Dana given as a synonym of albite and orthoclase.
| 1770 Cronstedt's Min. I. 68 Petro-silex, Lapis Corneus. The Hornstein of the Germans. 1791 Beddoes in Phil. Trans. LXXXI. 63 It forms molten currents of petrosilex and flint exactly the same as our gun-flints. 1794 Sullivan View Nat. I. 437 Porphyries, properly so called, and jaspers, but more ambiguously petro-silices and felt spar. 1815 J. Smith Panorama Sc. & Art II. 463 Petrosilex, or Chert occurs most frequently in beds of limestone. 1855 Lyall Man. Geol. xxviii. (ed. 5) 476 Compact Felspar, which has also been called Petrosilex,..is allied to clinkstone, but is harder, more compact, and translucent. It is a varying rock, of which the chemical composition is not well defined. 1865 Lubbock Preh. Times iv. (1869) 77 The type of the felspathic extreme of the series of trap rocks is..petrosilex..the average composition of which is 25 parts quartz and 75 felspar. |