Sand is the result of the weathering or gradual breakdown of rock (over thousands or millions of years - so we cannot witness it ourselves), as a result of chemical, physical or biological forces. Even the colour of sand (ranging from black for volcanic sand to grey to bright yellow to red) is due to the rock from which it has originated. In some regions of the earth, pink sand is found, due to unique micro-organisms which live within it. The finer the sand, the more sheltered from waves the beach is and vice-versa.