The rock particles that make up soil come in different sizes and are given different names to show this. Sand, often called a grain, is a piece of rock that measures from .0024 to .08 inches (.06 to 2 millimeters) across. Sand results when larger rocks disintegrate, eroded by water, weather, and glaciers. The two greatest deposits of sand on Earthís surface can be found in deserts and on beaches. When soil consists mostly of sand, its large grains cannot hold the water or nutrients needed for healthy plant growth one reason you donít see many plants in the desert or on the beach. When you look closely at a handful of sand, you may find that the grains are really many different colors; this is because sand comes from several different kinds of rocks. Sand may appear brown, yellow, white, or even black (when it comes from certain volcanic rock). The sand of some beaches may also have grains made of organic material the remains of living creatures, like shells and coral instead of rock.