Sand is a granular material composed of finely divided rock and mineral particles. Sand has various compositions but is defined by its grain size. Its grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 per cent sand-sized particles by mass.
Pritish Kumar Halder explains about Sand, a mineral particle in his blog.
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.
Calcium carbonate is the second most common type of sand, for example, aragonite, which has mostly been created, over the past 500 million 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.
Sand from rivers is collected either from the river itself or its flood plain and accounts for the majority of the sand used in the construction industry. Because of this, many small rivers have been depleted, causing environmental concern and economic losses to adjacent land. The rate of sand mining in such areas greatly outweighs the rate the sand can replenish, making it a non-renewable resource.
Sand dunes are a consequence of dry conditions or wind deposition. The Sahara Desert is very dry because of its geographic location and proximity to the equator. It is known for its vast sand dunes, which exist mainly due to a lack of vegetation and water. Over time, wind blows away fine particles, such as clay and dead organic matter, leaving only sand and larger rocks. Only 15% of the Sahara is sand dunes, while 70% is bare rock. The wind is responsible for creating these different environments and shaping the sand to be round and smooth. These properties make desert sand unusable for construction.
Abrasion: Before sandpaper, wet sand was used as an abrasive element between rotating devices with elastic surface and hard materials such as very hard stone (making of stone vases), or metal.
Agriculture: Sandy soils are ideal for crops such as watermelons, peaches, and peanuts, and their excellent drainage characteristics make them suitable for intensive dairy farming.
Air filtration: Finer sand particles mixed with cloth was commonly used in certain gas mask filter designs but have largely been replaced by microfibers.
Aquaria: Sand makes a low-cost aquarium base material which some believe is better than gravel for home use. It is also a necessity for saltwater reef tanks, which emulate environments composed largely of aragonite sand broken down from coral and shellfish.
Artificial reefs: Geotextile bagged sand can serve as the foundation for new reefs. Artificial islands in the Persian Gulf.
Beach nourishment: Governments move sand to beaches where tides, storms, or deliberate changes to the shoreline erode the original sand.
Brick: Manufacturing plants add sand to a mixture of clay and other materials for manufacturing bricks.
Cob: Coarse sand makes up as much as 75% of cob.
Concrete: Sand is often a principal component of this critical construction material.
Glass: Sand rich in silica is the principal component in common glasses.
Hydraulic fracturing: A drilling technique for natural gas, which uses rounded silica sand as a “proppant”, a material to hold open cracks that are caused by the hydraulic fracturing process.
Landscaping: Sand makes small hills and slopes (golf courses would be an example).
Mortar: Sand is mixed with masonry cement or Portland cement and lime to be used in masonry construction.
Paint: Mixing sand with paint produces a textured finish for walls and ceilings or non-slip floor surfaces.
Railroads: Engine drivers and rail transit operators use sand to improve the traction of wheels on the rails.
Recreation: Playing with sand is a favourite beach activity. One of the most beloved uses of sand is to make sometimes intricate, sometimes simple structures known as sand castles, proverbially impermanent. Special play areas for children, enclosing a significant area of sand and known as sandboxes, are common on many public playgrounds, and even at some single-family homes. Sand dunes are also popular among climbers, motorcyclists and beach buggy drivers.
Roads: It improves traction (and thus traffic safety) in icy or snowy conditions.
Sand animation: Performance artists draw images in sand. Makers of animated films use the same term to describe their use of sand on frontlet or backlit glass.
Sand casting: Casters moisten or oil molding sand, also known as foundry sand and then shape it into molds into which they pour molten material. This type of sand must be able to withstand high temperatures and pressure, allow gases to escape, have a uniform, small grain size, and be non-reactive with metals.
Sandbags: These protect against floods and gunfire. The inexpensive bags are easy to transport when empty, and unskilled volunteers can quickly fill them with local sand in emergencies.
Sandblasting: Graded sand serves as an abrasive in cleaning, preparing, and polishing.
Silicon: Quartz sand is a raw material for the production of silicon.
Thermal weapon: While not in widespread use anymore, sand used to be heated and poured on invading troops in the classical and medieval time periods.
Water filtration: Media filters use sand for filtering water. It is also commonly used by many water treatment facilities, often in the form of rapid sand filters.