Aluminium hydroxide, Al(OH)₃, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite

Gibbsite

Gibbsite, Al3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al3 . It is also sometimes called hydrargillite ....

 (also known as hydrargillite) and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide

Aluminium oxide hydroxide

Aluminium hydroxide oxide or aluminium oxyhydroxide, AlO is found as one of two well defined crystalline phases, which are also known as the minerals boehmite and diaspore...

, AlO(OH), and aluminium oxide

Aluminium oxide

Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...

, Al₂O₃, differing only by loss of water. These compounds together are the major components of the aluminium ore

Ore

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 bauxite

Bauxite

Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...

.