In a most basic sense , the sand of our beaches comes from soil erosion . The addition of new sand to beaches is seasonal , occurring during the rainy season when the river flow and sediment are washed into the sea. Today the supply of new sand to our beaches is greatly reduced by human activity . In the last 50 years river sand has been restricted by dams on river gravel mining and floodplain by private industry . Tap water also has small particles farther than larger particles of sand or gravel , so due to the fact that the oceans are the lowest point of any area of land , the sand has performed everywhere from top down to the banks of rivers or floods . Some sand is recycled to go through the cycle repeats become sandstone, and then demoted down in the sand again.
Sand also washed out to sea and in rivers draining into the beaches by the action of waves and tides .
lyndsay's answer is pretty good, but seems to ignore the question. silica (sand, SiO2) is very insoluble in water. Most other common minerals are much more soluble; feldspars, carbonates, sulfates. some beaches (ie. hawaii) have much less mature sediments, so many of the other minerals have not had time to chemically weather.
some deserts are composed of gypsum (CaSO4) instead of silica.