Sand-Stone, a genus of fossils found in various parts of Britain, and which is divided into four species, namely :
1. Calcareous Sandstones, which consist of carbonate of lime and marle, with a considerable portion of sand intermixed with its particles. Their surface is rough, generally grey, though they are sometimes found of a yellowish or brown cast. - This species is occasionally burned for lime.
2. Aluminous Sand-stones are those, the basis of which is alumina, or pure clay. They are of a close and compact texture, which is finer or coarser according to the size of the sand forming their constituent parts. This species is usually grey, yellow, or brown, and is chiefly manufactured into mill - stones, filtering - stones, or coarse whet-stones.
3. Siliceous Sand-stones are composed of grains of sand, that are cemented together with silica or flint, or with some substance, the basis of which is formed by the last mentioned fossil. They are considerably harder than any of the other species.
Sand-stones are of great utility for buildings designed to resist the combined effects of air, fire, and water. Some of these fossils are soft while in the quarry, but become hard on exposure to the air. Those of a friable nature are generally employed, being best adapted to this purpose; because the hard kinds are apt to burst in the fire : the latter, however, will ad-mit of being polished, and may be advantageously used for whet-stones.