corundum
(kɒˈrʌndəm)
Also 8 corivindum, -vendum, coriundum, 9 corundon.
[a. Tamil kurundam, in Telugu kuruvindam, Hindī kurunḍ; Skr. kuruvinda ‘ruby’. Cf. also corindon.]
1. A crystallized mineral belonging to the same species as the sapphire and ruby, but opaque or merely translucent, and varying in colour from light blue to smoky grey, brown, and black; called also adamantine spar.
| a 1728 Woodward Catal. For. Fossils 6 Nella Corivindum is found in fields where the rice grows. 1798 Greville in Phil. Trans. LXXXVIII. 403 My friend Colonel Cathcart sent me its native name, Corundum, from India, with some specimens..in 1784. 1794 Kirwan Min. I. 335 The second, in India, near Bombay and there called corundum. 1868 Dana Min. 138 Corundum..is ground and used as a polishing material, which, being purer, is superior in this respect to emery. It was thus employed in ancient times. 1886 Pall Mall G. 9 Mar. 11/2 A new process for obtaining pure aluminium from aluminium oxide or broken corundum. |
2. Min. Used as the name of a mineral species, under which Dana includes the transparent sapphire (including the ruby, and the (so-called) oriental amethyst, emerald, and topaz), the opaque or translucent adamantine spar (= prec. sense), and the granular emery. It consists of crystallized alumina (Al2O3) variously coloured.
| 1804 Phil. Trans. XCIV. 44 Those stones which offer the greatest resistance to a mechanical division, such as quartz, blue corundum or sapphire. 1868 Dana Min. 139 Emery..in which the corundum is in distinct crystals. 1870 H. Macmillan Bible Teach. xiv. 273 The sapphire..the ruby and the Oriental topaz..are all mere coloured varieties of the mineral substance known as corundum. |
3. attrib., as in corundum point, corundum stick, corundum tool, corundum wheel, used in polishing, dressing millstones, etc.
| 1792 Oakley in Phil. Trans. LXXXVIII. 407 Among these broken lumps, the Corundum stone is found. 1873 J. Richards Wood-working Factories 106 Corundum or emery wheels are now generally used for dressing both saws and cutters. 1884 F. J. Britten Watch & Clockm. 86 The edges of holes in dials may be trimmed with corundum sticks. |