What is sand?
Sand is a naturally occurring material composed of minute rock and mineral particles. A single particle of sand (a grain of sand) ranges in size from 1/16 mm to 2 mm. The next size up from a sand particle is called "gravel", while the next smaller size is called "silt". When it is handled, sand has a distinctive gritty feel.
Size your sand
For collection and display purposes, it can be useful to sort one's sand by size. This makes for a nice, uniform display. Sand can be classified by the size of the particles:
- very fine (0.05 - 0.1 mm)
- fine (0.1 - 0.25 mm)
- medium (0.25 - 0.5 mm)
- coarse (0.5 - 1 mm)
- very coarse (1 - 2 mm)
The Colours of Sand
It may come as a surprise to you, but not all sand is "sand-coloured." The colour of any particular grain of sand is determined by its chemical composition. A microscope and a good crystal identification book may be helpful in identifying the type of sand you have. The most common type of sand is made of silicon dioxide (usually quartz). These grains are clear or opaque.
White sand is formed from eroded limestone. Black sands are volcanic, as are green sands composed of olivine. In some areas, sand is primarily crushed seashells (calcite), which gives a pinkish cast.
|clear||quartz (from granite or sandstone erosion)|
|dull black, grey, or reddish-brown||basalt|
|olive-green or brownish||olivine (from basalt erosion)|
|black (shiny irregular shapes)||obsidian (from basalt erosion)|
|clear, yellow, or pink||feldspar|
|light-coloured or pink||granite|
|yellow or brownish||monazite|
|shiny black and magnetic||magnetite|
|white, tan, or pink||carbonate (from shell erosion)|
In addition to the mineral-based sands, there are also biogenic sands which contain the remains of animals and plants, shell fragment, tiny skeletons, micro-mollusks, and other sea creatures often almost too small to see by the naked eye. These remains are called "foraminifera".