The exact composition of sand varies from region to region, but in most cases it is a mixture of silicon dioxide, weathered rocks and local minerals, calcium carbonate from reefs, and the remains of microscopic sea creatures. The action of the ocean waves or wind grinds this material together until all that remains are tiny fragments.
The material that makes up sand gives it its unique characteristics. Most inland sand, including that found in deserts, consists of silicon dioxide or quartz weathered into tiny particles. In some cases, desert sand may also be blown in from nearby bodies of water. Tropical sands are often the remnants of reefs or other sea creatures, sometimes mixed with quartz and other mineral sands. The beaches of Hawaii, on the other hand, are almost entirely calcium carbonate remnants of sea creatures, since the islands have no natural source of quartz available.
Sand may have different colors depending on what minerals or other materials are present. Calcium carbonate sand is a vivid white, while sand formed from hematite can range from orange to pink. Olivine gives sand a greenish tinge, while iron provides a yellow coloring. In some tropical areas, volcanic stone and glass produces sand that is deep black in color.