Sand is a mixture made up of very small pieces of different rocks or minerals. When most of the pieces are at least two millimeters wide, it is called gravel. When most of the pieces are less than one-sixteenth of a millimeter wide (about as wide as the lines on a ruler), it is called silt.
Sand is the result of erosion of large boulders. They get smaller and smaller until they reach the beach or a low lying area.
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
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