sand

Sand is a granular material composed of finely divided rock and mineral particles. It is defined by its particle size, generally between 0.063 millimeters and 2 millimeters in diameter. The most common constituent is silica in the form of quartz, but sand can contain significant amounts of feldspar, mica, lithic fragments, and, in coastal or biologically active settings, shells and corals.

Sand originates from the weathering and erosion of rocks and minerals. Particles are transported by wind and water, then deposited in environments such as rivers, lakes, deserts, and oceans. Sorting by transport processes produces characteristic grain-size distributions and rounded shapes.

Types of sand vary by composition. Silica sand is widely used for glassmaking and foundry applications. Carbonate sands are rich in calcium carbonate from shells and skeletons. Feldspathic sands contain feldspar minerals. Biogenic sands are produced by the accumulation of shell debris and coral fragments.

Properties of sand include grain size and shape, which influence porosity and permeability. Well-sorted, round grains store and drain water efficiently, while poorly sorted sands have varied drainage. Hardness, mineral composition, and binding cementation affect strength in construction materials.

Major uses include construction aggregate for concrete and mortar, glass production, sandblasting, filtration, and industrial applications such as foundry molds and hydraulic fracturing proppants.

Geologically, sand forms extensive deposits in deserts as aeolian dunes and along shorelines as beaches and dune fields. It also occurs in sedimentary reservoirs and as aquifers. Sand mining and dredging can impact habitats, coastal stability, and ecosystem diversity.

Sand is globally abundant and found on almost every continent. Leading producers include regions with extensive desert or beach resources, and many jurisdictions regulate extraction to balance demand with ecological concerns.