The New Student's Reference Work/Sand
Sand, a term loosely applied to incoherent mineral matter occurring in particles smaller than pebbles and larger than particles of mud or dust. If the mineral matter is fine enough to become mud when wet, it would hardly be called sand. Between clay, the particles of which are very small, and sand there is no sharp line of demarcation. The one grades into the other. The same is true of sand and gravel. Sand usually consists chiefly of quartz, but it generally contains other mineral matter in small quantities, and sometimes is largely made of other minerals. Grains of sand are usually thought to be round, though this is rarely the case. They, however, often are roundish. As it occurs in nature, quartz-sand is made of partly rounded bits of quartz-crystals. These crystals originally occurred in igneous rock, and by the decay of the other minerals of the rock the quartz-crystals were set free. They were then brought together in valleys and along shores by the wash of rain, streams and waves. The purest varieties of quartz-sand are used for the manufacture of glass. Sand is extensively used with lime, for mortar, cements etc. When cemented by natural processes, sand becomes sandstone.