Sand FAQ

A few quick questions and answers of the subject of sand.

What actually is sand?
Sand is a granular material made up of fine loose particles ranging in size from 0.0625 mm up to 2.00 mm. Particles larger than 2.00 mm are referred to as gravel, while particles smaller than 0.0625 mm are referred to as clay. Sand is commonly divided into five sub-categories based on size:

  • Very fine sand – 0.0625 to 0.125 mm
  • Fine sand – 0.125 to 0.25 mm
  • Medium sand – 0.25 mm to 0.5 mm
  • Coarse sand – 0.50 mm to 1.00 mm
  • Very coarse sand – 1.00 mm to 2.00 mm

What are the different sand categories?
There are three main types of sand – mineral sands, biogenic sands and precipitated sands. Mineral sands form from the mechanical and chemical breakdown of rocks. Biogenic sands, also known as carbonate sands, are formed from the remains of living organisms such as corals, forams, shells, gastropods, tube worms and so on. The third category, precipitated sands, are formed by a chemical process whereby minerals are precipitated out of an aqueous solution, such as in shallow lakes or the sea.

What kind of materials is sand comprised of?
Sand is generally made up of a mixture of different materials with the most common being minerals such as quartz resulting from the break down of rocks. Some sands may be comprised of organic remains such as shell and coral fragments or the skeletal remains of marine organisms such as plankton. The composition is very much dependant on the nature of local materials. For example, sands in volcanically active regions may consists of ash or other related fragments and the sands around coral atolls might consist entirely of coral fragments.

How does sand accumulate, for example, on beaches?
Sand accumulates by a variety of processes with perhaps the most well known being the action of waves and currents in coastal areas – most of the sand on beaches accumulates this way. Another well-known process that brings sands together is the wind and examples would be sand dunes found along the coast and in desert areas. The process of erosion by rivers, and even glaciers, also causes sand to accumulate.

What kind of minerals can I find in sand?
There are many different minerals found in sand including quartz, feldspar, mica, calcite, gypsum, hornblende, zircon and many others. As well as minerals sand may also contain rocks fragments such as basalt, magnetite, pumice or precious material such as garnet, amethyst or even gold!

Why do the sands on different beaches vary in colour?
The colour of any sand is down to the different minerals or mixture of minerals and other particles that makes up the sand. For example, white sands can often consist entirely of the white remains of corals or limestone. Black sands may be made up of dark coloured volcanic materials such as magnetite, which can be picked up with a magnet or even particles of marine coals exposed along the shore. The mineral olivine is responsible for some green sands and reddish or cream coloured sands are often comprised from particles of eroded sandstone.

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