4SEAS

Most sand is made from very small particles of rocks that have been broken down by the weathering action of rain, ice and wind, or by the action of waves beating against our shores. The colour of sand usually reflects the type of rock or specific minerals within them.

In non-tropical regions, the most common type of sand on beaches is made up mainly of Silicon Dioxide or silica (SiO₂) in the form of quartz. This quartz can contain small amounts of iron which gives it a typical golden yellow colour.

The white sands which are often seen in tropical areas usually contain particles mainly made up from, Calcium carbonate (CaCO₃) from limestone rocks, but also from the hard bodies of corals which are also made from Calcium carbonate. Coral reefs can be broken up by storms or by the animals which eat corals and the dead coral can then be broken down into fine sand particles which are transported onto beaches by waves and currents. In other parts of the world, volcanic rocks, which are often very dark in colour, are broken down to form deep black sands.

As well as sands from corals, the bodies of many other marine organisms get broken down to become part of sand. Seashells are perhaps the most commonly seen example of this, but there are even seaweed which make hard skeletons, again from Calcium Carbonate, and these too can help form a significant proportion of the sand in some places.