Sand is a mixture of very small pieces of different rocks or minerals. Sand grains are between the size of gravel grains (which is from 2 mm to 64 mm) and the size of silt (which is around 0.0625 mm to 0.004 mm). It is found on beaches, and in deserts.
Sand is most of the time made of silica (silicon dioxide, or SiO2). Sand is also formed by Granite by weathering and erosion. Sand is made from large boulders eroding (being broken apart by wind or rocks). They get smaller and smaller until they reach the beach or a low lying area. Sand dunes are made when wind or a river pulls sand into a mountain-like shape. They can be found in deserts, but sometimes high up on beaches too.
Sand can be mixed with water to make concrete, a tough material which can be used in buildings to help support the structure. It can also be used to make bricks or sand castles. When mixed with water sand will become mud.
Sand on a beach in Calabria. You can see sand dunes here.
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