What is Sand ?

The technical definition of sand is therefore, " material consisting of particles ranging in size from 1/16 mm to 2.0 mm". Sand, along with gravel, silt and clay are collectively known as sediment, and are produced by the mechanical and chemical breakdown of rocks. Once disaggregated from the original source rock, this material is eroded and transported by either wind, water or ice. Sand tends to accumulate on the coast but it is also found along rivers, around lakes, in caves and on hillsides, or ultimately as sediment in the sea. Wind can bring sand over large areas especially in the deserts as sand dunes.

Sand can be classified as different type, depending on its origin : beach and sea sands, river and lake sands, eolian and desert sands, volcanic sand, quarry sand...

Sand can also be divided in two categories: mineral sands and biogenic or calciferous sands : the first being the product of erosion, the latter the product of biological processes.

Garnets and quartz

Almost any mineral can exist as sand, but the most common constituent is quartz (silica). There is also granitic rocks like feldspar and mica. Calcite and gypsum can also be present depending on the geologic origin and pathways of transport. Sand can also contain debris of volcanic rocks like basalt, magnetite or pumice. But sand also can contain precious metals (gold) and gemms like garnet, olivine and sapphire.

Mica

Serpentine, Corsica

Biogenic sand, Ibiza

Magnetite, Bali

Biogenic sands contains the remains of animals and plants, shell fragment, tiny skeletons, micro-mollusks, and other sea creatures often almost too small to see by the naked eye. They are called foraminifera, and shown on the picture. But sand is often a mixture of mineral and biogenic grains.