Sand is an element formed by grinding up stones and minerals. The most common form of stone in the mixture of sand is silicon dioxide which is presented in the form of quartz. The Earth's landmasses are made up of rocks and minerals, including quartz, feldspar and mica. Mostly tho, sand is made from Quartz as it is very hard, granting decent defensive abilities and incapable of dissolving in water.
Sand is sort of weak to nearly everything. Fire at high temperatures will begin to melt the sand into glass if the sand is not compact and condensed. Water can make sand heavier, same with oils therefore it can render sand nearly useless.
Known users: Gaara, Shukaku, Temari, Sasori, Kankuro.
Combining sand release with a different type of earth chakra that can create iron for example, can create iron sand.