Silica Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz.

In terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm (or ⅟16 mm, or 62.5 μm) to 2 mm. An individual particle in this range size is termed a sand grain. The next smallest size class above sand is gravel, with particles ranging from 2 mm up to 64 mm. The next smallest size class is silt: particles smaller than 0.0625 mm down to 0.004 mm in diameter. The size specification between sand and gravel has remained constant for more than a century, but particle diameters as small as 0.02 mm were considered sand under the Albert Atterberg standard in use during the early 20th century. A 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A 1938 specification of the United States Department of Agriculture was 0.05 mm.[1] Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).