Sand

Sand, finely-divided quartz, with admixtures of other substances, accumulated by various agencies. The grains may be perfectly regular crystals of quartz; angular fragments freshly derived from the breaking up of granite or schist; water-worn and rounded; chemically corroded; or with a redeposited coating of silica. No sand in any quantity is formed of flint; The other constituent minerals of igneous rocks, such as scales of mica, tourmaline, epidote, garnets, cassiterite, etc., often occur in sands, as does also finely-divided shelly calcareous matter. The name "sand" is sometimes loosely applied to the ground-down coral and nullipores of the shores of the Bahamas and Bermudas. Sand may be accumulated by wind, rivers, lakes, glaciers, or the sea; and, in the absence of fossils, it is well-nigh impossible to distinguish sands that have originated in one of these ways from those originating in another. Sands are generally poor in fossils, as their porous character leads to the destruction of any they may contain, by percolation. They are commonly stained red or yellow by oxide of iron; but may be green from the presence of glauconite (q.v.); lilac from that of humus acid compounds; grey from carbonaceous matter; or bleached to silver sand by the reducing action of organic acids. Among our chief English formations of loose sand are the Trias, the Portland Sands, the Hastings (including the Ashdown and Tunbridge Wells) Sands, the Lower Greensand (including the Sandgate and Folkestone series and some of the Hythe beds), the Upper Greensand, more commonly incoherent, the Thanet Sands, and the Bagshot Sands. Sand is employed for many commercial purposes, for glass-making, for making mortar, for earthenware, for foundry-moulds, for the cultivating of ferns and for scouring, whilst it was formerly put down on brick floors.