Gibbsite

An article about the mineral Gibbsite

Gibbsite

Gibbsite sample

Gibbsite is a mineral form of aluminum hydroxide, with the chemical formula Al(OH)_. It is an important ore of aluminum and is one of the main components of bauxite, the principal ore of aluminum. Gibbsite is named after the American mineralogist George Gibbs.

Properties

Gibbsite is a white, gray, or colorless mineral that crystallizes in the monoclinic system. It typically forms as tabular crystals, but can also occur in massive, stalactitic, or earthy forms. The mineral has a pearly luster and a Mohs hardness of 2.5 to 3.5, making it relatively soft. Gibbsite has a specific gravity of approximately 2.3 to 2.4.

Formation and Occurrence

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Structure of Gibbsite

Gibbsite commonly forms in tropical and subtropical climates as a result of the weathering of aluminosilicate minerals. It is often found in lateritic soils and is a major component of bauxite deposits. Gibbsite can also form as a secondary mineral in hydrothermal environments.

Uses

Gibbsite is primarily used as an ore of aluminum. The extraction of aluminum from gibbsite involves the Bayer process, where the mineral is dissolved in sodium hydroxide to separate the aluminum hydroxide from impurities. The aluminum hydroxide is then calcined to produce alumina, which is subsequently reduced to aluminum metal through the Hall–Héroult process.

Related Minerals

Gibbsite is part of the aluminum hydroxide group, which includes other polymorphs such as boehmite and diaspore. These minerals are also important constituents of bauxite and are used in the production of aluminum.

See also

• Bauxite
• Aluminum
• Bayer process
• Hall–Héroult process

Related pages

• Alumina
• Laterite
• Hydrothermal mineral deposit