What Is Sand? What Is It Made Of?


What Is Sand
Sand consists of minerals and other particles ranging between roughly 0.06 and 4.75 mm. (image: Siim Sepp, CC 3.0 Unported License)

At its core, sand is a granular material composed of finely divided rock and mineral particles. Technically, it’s defined by size, being coarser than silt and finer than gravel. The particles range in size from 0.0625 to 2 millimeters, according to the definition set by the United States Geological Survey. The International Granular Standard scales it slightly differently, ranging from 0.075 to 4.75 mm.

A psammophile is an organism that lives in sand. People who collect sand as a hobby are arenophiles.

Sand vs Silt vs Gravel

The primary difference between sand, silt, and gravel is the size of their particles. Silt is finer than sand, with particles less than 0.0625 mm, often giving it a smoother feel. Gravel, conversely, is coarser, with particle sizes above 2 mm. This difference in size results in distinct physical characteristics and applications for each material. Sand feels gritty to the touch, while silt feels more like flour and gravel is pebbly.

Where Does Sand Come From?

Sand originates from the weathering and erosion of rocks and other materials over millions of years. The actions of wind, water, and chemical reactions drive this process, breaking rocks into smaller particles. Different formation processes result in sand with varying chemical and physical properties. For instance, particles of sand from desert dunes tend to be rounded due to the wind constantly pushing the grains against each other.

Beach and Desert Sand

The sand found on beaches primarily comes from the erosion of rocks and coral reefs. Erosion and weathering of rocks on land forms particles that rivers carry to the sea. Waves and tides gradually break down these materials into finer particles. In deserts, sand results from the weathering of rocks due to temperature fluctuations and wind erosion.

Sand Around the World: Composition and Appearance

Different regions have distinctive sands, each with unique compositions and appearances. For example:

  • Sahara Desert: Comprised mainly of quartz and feldspar, this sand has fine, golden appearance.
  • Hawaii’s Black Sand Beaches: Formed from volcanic activities, these sands contain basalt, giving them a striking black color.
  • Hawaii’s Green Sand Beach: Gets its green color from volcanic olivine.
  • Pink Sand of Bermuda: Consisting of coral, shells, and calcium carbonate, it gets its pink hue from microscopic organisms called foraminifera.
  • White Sands, New Mexico: Composed of gypsum, these sands stand out with their brilliant white color.
  • Whitehaven Beach, Australia: The pristine powdery brilliant white beach consists of nearly pure silica.
  • Great Sand Dunes, Colorado: The gold, beige, and reddish tones comes from the blend of quartz, feldspar, and magnetite.

Uses of Sand

Sand is integral to numerous industries and daily life applications:

  • Construction: Concrete production, paving, and glassmaking.
  • Water Filtration: Used in water purification processes.
  • Agriculture: For mixing with soil to improve aeration and drainage.
  • Landscaping: Enhances soil quality in gardens and parks.
  • Recreational: Essential for creating beaches, sandpits, and golf bunkers.
  • Abrasives: For smoothing surfaces.
  • Land Reclamation: For filling in parts of the ocean and making new land area.
  • Hydraulic Fracturing: In the oil and natural gas industry, for propping open fissures in rocks.
  • Metal Casting: In molds for casting metal products.

Environmental Impact and Sustainability

While often perceived as abundant, sand is a non-renewable resource. The demand in construction and various industries has led to overexploitation. Basically, the world is running out of sand.

Ecological Consequences

Excessive sand mining leads to erosion, loss of biodiversity, and disruption of natural habitats. In coastal areas, it exacerbates the effects of sea-level rise and increases the vulnerability of communities to natural disasters.

Solutions include:

  • Regulated Sand Mining: Implementing stricter regulations to control the amount and methods of sand extraction.
  • Alternative Materials: Researching and promoting substitutes for sand in industrial applications. For example, manufactured or M sand comes from artificial treatments of rock and hold promise for construction applications.
  • Recycling: Encouraging the recycling of concrete and glass to reduce the demand for new sand.

References

  • Beiser, Vince (2018). The World in a Grain: The Story of Sand and How It Transformed Civilization. Riverhead Books. ISBN 978-0399576423.
  • Kim, Tae Goun (2007). “The economic costs to fisheries because of marine sand mining in Ongjin Korea: Concepts, methods, and illustrative results”. Ecological Economics. 65 (3): 498–507. doi:10.1016/j.ecolecon.2007.07.016
  • Pettijohn, F.J.; Potter, P.E.; Siever, Raymond (1972). Sand and Sandstone. New York: Springer Verlag. ISBN 9780387900711.
  • Pilegis, M.; Gardner, D.; Lark, R. (2016). “An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete”. Materials. 9 (6): 440. doi:10.3390/ma9060440
  • Torres, Aurora; Simoni, Mark U.; et al.(2021). “Sustainability of the global sand system in the Anthropocene”. One Earth. 4 (5): 639–650. doi:10.1016/j.oneear.2021.04.011