Silicon dioxide

The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2.

Related Topics:
Chemical compound - Oxide - Silicon - Chemical formula - O

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

It is found in nature in several forms, including quartz and opal. In fact, silica has 17 crystalline forms (see

Related Topics:
Quartz - Opal

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Nomenclature of Silica). Also, many forms of life include silica structures, including microorganisms such as diatoms, plants such as horsetail, and animals such as hexactinellid sponges.

Related Topics:
Diatom - Horsetail - Hexactinellid - Sponge

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

It is manufactured in several forms including glass (in colorless high purity form called fused silica), synthetic amorphous silica and silica gel (used e.g. as desiccants in brand new clothes and leather goods). Silica is a major ingredient of Portland cement. The ceramic re-entry heat protection tiles mounted on the bottom side of the Space Shuttles are made mostly of silica, as are the firebricks used in steel processing.

Related Topics:
Glass - Fused silica - Silica gel - Portland cement - Space Shuttle - Firebrick - Steel

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The most common constituent of sand in inland continental settings and non-tropical coastal settings is silica, usually in the form of quartz because the considerable hardness of this mineral resists erosion. However, the composition of sand varies according to local rock sources and conditions.

Related Topics:
Sand - Quartz

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Inhaling crystalline silica dust can lead to silicosis.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Variants found in high-pressure impacts are coesite and stishovite.

Related Topics:
Coesite - Stishovite

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Silica is also used as a food additive, primarily as a flow agent in powdered foods, or to absorb water.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~