Sand

 Sand

is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt. 

Sand can also refer to a textural class of soil or soil type, a soil containing more than 85 percent sand-sized particles by mass.

 

noun sand plural noun sands a loose granular substance, typically pale yellowish brown, resulting from the erosion of siliceous 

and other rocks and forming a major constituent of beaches, riverbeds, the seabed, and deserts.

 

The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland 

continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. 

The second most common type of sand is calcium carbonate, for example, aragonite, which has mostly been created, over the past half billion years, 

by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated 

the ecosystem for millions of years like the Caribbean. Somewhat more rarely, sand may be composed of calcium sulfate, such as gypsum and selenite, 

as is found in places like White Sands National Park and Salt Plains National Wildlife Refuge in the U.S.

 

Sand is a non-renewable resource over human timescales, and sand suitable for making concrete is in high demand. Desert sand, although plentiful, 

is not suitable for concrete. 50 billion tons of beach sand and fossil sand is used each year for construction.