Because silica is the most common component of sand in non-tropical climates, the chemical formula for sand is SiO2. The number of silicon atoms in silica is divided by the number of oxygen atoms in a 1:2 ratio.
This silica is commonly found in the form of quartz in sand. Quartz has the chemical formula SiO2 and a crystal structure in which each silicon atom is linked to four oxygen atoms and each oxygen atom to two silicon atoms. Sand can also include calcium carbonate in some countries. CaCO3 is the chemical formula for calcium carbonate.