An aluminum ore which consists of the minerals
– Gibbsite- Al(OH)3
– Boehmite- γ-AlO(OH)
– Diaspore- α-AlO(OH)
– Goethite- α-FeO(OH)
– Hematite- Fe2O3
– Kaolinite- Al2Si2O5(OH)4
– Anatase- TiO2
Bauxite is not a mineral but rather it is classified as a rock.
Hardness: 1- 3
Made up of oolitic spherical masses in a matrix of clays.
Specific gravity: 2.0 -2.6
Common to the oxide and hydroxide groups
Mineral of the Month: March 2015
Bauxite is strip mined since it is next to the surface with little or no overburden. The first step in producing aluminum is to crush the bauxite and purify it using the Bayer Process. In the Bayer Process the bauxite is washed in a hot solution of sodium hydroxide which leaches aluminum from the bauxite. The aluminum is precipitated out of solution in the form of aluminum hydroxide, Al(OH)3. The aluminum hydroxide is then calcined to form alumina, Al2O3.
Aluminum is smelted from the alumina using the Hall-Heroult Process. In the Hall-Heroult Process the alumina is dissolved in a molten bath of cryolite (Na3AlF6). Molten aluminum is removed from the solution by electrolysis. This process uses an enormous amount of electricity. Aluminum is usually produced where electricity costs are very low.
Calcined alumina is a synthetic corundum, which is a very hard material. Calcined alumina is crushed, separated by size and used as an abrasive. Aluminum oxide sandpaper, polishing powders and polishing suspensions are made from calcined alumina.
Sintered bauxite is often used as an sand-blasting abrasive. It is produced by crushing bauxite to a powder and then fusing it into spherical beads at very high temperature. These beads are very hard and very durable. The beads are then sorted by size for use in different types of sandblasting equipment and for different sandblasting applications. Their round shape reduces wear on the delivery equipment.
Bauxite is found in abundance at many locations around the world. In 2010 the ten leading bauxite producing countries were: Australia, China, Brazil, India, Guinea, Jamaica, Russia, Kazakhstan, Suriname and Greece. Each of these countries has enough reserves for many years of continued production. Some have reserves for over 100 years of production.
The United States has small amounts of bauxite in Arkansas, Alabama and Georgia; however, there is very little mining of bauxite in the United States and at least 99% of consumption is imported.