Silex silica, silicium, or silicious earth, is one of the most abundant substances in nature, constituting the entire mass of many mountains, and probably of a large portion of the globe itself. It is the chief component of sand, sandstone, flint, granite, quartz, porphyry, rock-crystal, agate, and many precious stones; it is the chief substance of which glass is made; also an ingredient, in a pulverised state, in the manufacture of "stoneware, " and it is essential in the preparation of tenacious mortar. Silex, when pure, is a fine powder, hard, insipid, and inodorous; rough to the touch, scratches and wears away glass. It does not form an adhesive mass with water, but falls to the bottom, leaving the water clear: however, if the silex be very minutely powdered, a small portion of it will be dissolved by the water. Silex may be obtained in a pure state by igniting powdered quartz with three parts of pure potash in a silver crucible, and adding to the solution a quantity of acid sufficient to saturate the alkali; then by evaporating to dryness, there will remain a gritty powder, which, when washed with water, will be pure silex.