Erosion constantly wears away solid rock through the action of rain, snow and waves, frost and ice, glaciers and wind and the bits broken off are slowly broken down into ever-smaller pieces. The most common mineral found in sand is quartz but  other mineral, such as calcite, feldspar and mica are also present. The colour of sand on a beach reflects the material from which it is made: in Hawaii sands from volcanic rocks are black
while those of coral islands are very pale because they are formed from the ground-down skeletons of long-dead coral polyps rather than from eroded rock.