When it comes to sand, size is all that matters. That is because sand is defined as any mineral between .065 millimeters and 2 millimeters in diameter, which is about the width of a nickel. The fact that sand can be composed of any mineral provides endless combinations of sand!
There are two general types of sand: mineral sand and organic sand. Mineral sands are formed by geological forces. Most sand on earth is quartz. Quartz begins as a rock, such as granite, sandstone, or limestone. Weathering breaks apart granite’s two major components: quartz and feldspar. When quartz, which is a silica-based mineral, reaches the correct size the quartz becomes sand. The feldspar part of granite breaks down over the ages to form the primary component of clay.
Sand can take on many different colors. For example, the pink sand at the Pink Coral Reef Dunes State Park in Southern Utah is quartz has been stained by rusting hematite (iron) when it was part of the Navajo Sandstone formation.
There is even green sand, which is very rare! Some of it can be found on beaches in Hawaii and Guam. This sand gets its color from the mineral olivine, which eroded from basalt flows from nearby volcanos. There are even two kinds of black sand! One type of black sand is formed with heavy metals like gold. It contains minerals like hematite and magnetite. The second type of black sand can be found on beaches near volcanos and is composed of basalt.
The mineral that forms the dunes of White Sands National Park is about 98 percent pure gypsum sand. Gypsum sand is considered rare because gypsum is water soluble—it dissolves in water like sugar in iced tea. It is even rarer to find gypsum sand in the form of dunes, which are mounds of sand piled up by wind. The 275-square miles of dunes are comprised of over 4.5 billion tons of gypsum sand. It is one of the many things that make White Sands a unique and special place.
Last updated: January 22, 2020