Silicon dioxide also known as silica is a chemical compound made up of silicon and oxygen. It's chemical formula is SiO2 because it's made up of one atom of silicon and two atoms of oxygen. Found most commonly in nature as the mineral quartz, it's the second most abundant mineral in Earth's crust. Silicon dioxide can be found in most types of sand and exists in several different crystalline forms and a number of cryptocrystalline forms.
Silicon dioxide is widely used in industry because its melting point is higher than copper, iron and aluminium. It's used for the production of glass, optical fibres and as a raw material in whiteware ceramics, stoneware, porcelain and industrial cement. It's also used in toothpaste because its hardness helps to remove plaque. As a food additive silicon dioxide protects dried foods from moisture and powdered foods from clumping or sticking together. The small white packets called silica gel that can often be found with new merchandise contain grains of silicon dioxide. The packets absorb moisture hence protect the item they're packed with.