Sand is a composite of various rocks and mineral pieces. As weathering takes place, tiny bits of the rocks and minerals are washed downstream from their source. These bits can be from 1/16mm diameter to 2.0 mm diameter. With five classifications for the size being very fine sand (1/16mm- 1/8mm), fine sand (1/8- 1/4mm), medium sand (1/4mm- 1/2mm), coarse sand (1/2mm- 1mm), and very coarse sand (1mm- 2mm). The most common form of sand found in inland continental settings and non-tropical coastal settings is silicon dioxide, or quartz.
The composition of mineral sand is highly variable, depending on the local rock sources and conditions. The bright white sands found in tropical and subtropical coastal settings are eroded limestone and may contain coral and shell fragments in addition to other organic or organically derived fragmental material, suggesting sand formation depends on living organisms, too. The gypsum sand dunes of the White Sand National Monument in New Mexico are famous for their bright, white color. Arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a (usually nearby) granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic (lava) with a high olivine content. Many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones.
Sand if very versatile and is an indispensable material in our lives. It is used for everything from casting metals (as in engine blocks, cast iron cookware, and other metallic items used), as an abrasive (sandblasting and sand papers), a major ingredient in the construction industry (concrete & cement, bricks and blocks) and it is used as a filtrate material.
Pismo Beach Sand
by Wilson44691: Mark A. Wilson, Department of Geology, The College of Wooster – Own work. Licensed under Public Domain via Commons
(Perissa, Santorini, Greece) Licensed under CC BY-SA 3.0 via Commons
Sand from Gobi Desert
by Siim Sepp – Own work. Licensed under CC BY-SA 3.0 via Commons
Sand from the beach at Scala dei Turchi, Sicily. Made up of shell fragments and quartz.
Black volcanic sand from the beach in Perissa, Santorini, Greece
“Scala dei Turchi Sand 062313” by Wilson44691 – Own work. Licensed under CC0 via Commons