Silicon dioxide, or SiO2, is commonly known as sand or quartz. It exists naturally in Earth's crust. It also exists in the biology of plants, animals and water.
SiO2 is a naturally occurring material composed of the shells of microscopic, single-celled algae. SiO2 is consumed by animals, including humans, as part of their natural diet and is considered harmless. Numerous pharmaceutical companies use SiO2 in pills and vitamins as an anti-caking or glidant agent. It is present in almost every pill made out of a powder. SiO2 also has industrial uses which include the manufacture of cement, natural pesticides, glass and numerous electronics.