Si2Al2O5OH4

Si2Al2O5OH4 is the chemical formula for kaolinite, a common clay mineral. It is a hydrated aluminum silicate. Kaolinite is a layered silicate mineral composed of tetrahedral sheets of silica (SiO4) linked to octahedral sheets of alumina (Al(OH)6). These layers are stacked in a 1:1 ratio, meaning one tetrahedral sheet is bonded to one octahedral sheet. The hydroxyl groups (OH) are located within the octahedral layer.

The structure of kaolinite is relatively stable and it is generally inert. It has a Mohs hardness of 2 to 2.5, indicating it is a soft mineral. Kaolinite is typically white or off-white in color, though impurities can impart various shades of gray, yellow, or brown. It is insoluble in water and most acids and bases.

Kaolinite is a significant component of many soils and sedimentary rocks. It is formed through the weathering of feldspar minerals and other aluminum-rich silicates. It is found worldwide in sedimentary deposits and hydrothermal alteration zones. Kaolinite has numerous industrial applications, including its use in the production of ceramics, paper, paints, rubber, and as a filler material. Its fine particle size, chemical inertness, and whiteness contribute to its utility in these industries.