Sandstone

Sandstone, sand cemented either by mere pressure producing a welding of the quartz-grains, by carbonate of lime, by carbonate or oxide of iron, 0r by silica. When coarse-grained, it is termed a grit. It is frequently flaggy from the presence of scales of mica. Those in the Old Red Sandstone of Caithness, Dundee, Arbroath, Cork, Kerry, etc., are among the oldest used in building. The Yorkshire flags, used for paving and for grindstones, and the Craigleith Stone of which much of Edinburgh is built, belong to the Carboniferous system; the St. Bees Sandstone, used for Furness Abbey, is Permian; whilst some of the variegated or "bunter" sandstones of the Trias are false-bedded, and are only held together by cohesion due to pressure, but others are used in building. In the Hastings Sands highly-ferruginous sandstones, in former times the source of all our English iron, occur; in the Lower Greensand, besides the valuable siliceous limestone known as Kentish Rag, beds of rubbly sandstone known as hassock are worked; _and the Upper Greensand contains the valuable fire-stone used for furnaces, hearthstones, and building. In the loose sands of Eocene age, known as the Thanet Sands and the Bagshot Sands, the very compact and tough pure sandstone, known as Sarsenstone, from which most megalithic monuments in the south-east of England are made, is found in lines of large irregular nodular masses often left on the surface of the chalk. [TORRIDON SANDSTONE.]