Resources
According to the US Geological Survey, the world's bauxite resources are estimated to be
55 to 75 billion tonnes located mainly in South America (33%), Africa (27%), Asia (17%),
Oceania (13%), and elsewhere (10%). Today, Australia supplies 35% of the demand worldwide for bauxite, South America 25%, and Africa 15%. The current reserves are estimated at
being able to supply worldwide demand for more than two centuries. Note that about 95% of
bauxite is of the metallurgical grade and hence used for the production of primary aluminum metal.
Description
Bauxite is the major source of aluminum sesquioxide (alumina, Al
2O
3) worldwide. Bauxite is
a soft and red clay, rich in alumina. From a geological point of view bauxite is defined as a residual
sedimentary rock in the laterite family that results from in situ superficial weathering in moist tropical climates of clays, clayey limestones, or high-alumina-content silicoaluminous
igneous and metamorphic rocks containing feldspars and micas.
Bauxite is a sedimentary rock, so it has neither a precise
definition nor chemical formula. From a mineralogical point of view, bauxite is mainly composed of hydrated alumina minerals such as gibbsite [Al(OH)
3 or Al
2O
3.3H
2O, monoclinic] in
recent tropical and equatorial bauxite deposits, while boehmite [AlO(OH) or Al
2O
3.H
2O, orthorhombic] and, to a lesser extent, diaspore [AlO(OH) or Al
2O3
.H
2O, orthorhombic] are the
major minerals in subtropical and temperate bauxite old deposits. The average chemical
composition of bauxite is 45 to 60 wt.% Al
2O
3
and 10 to 30 wt.% Fe
2O
3, the remainder consisting of silica, calcia, titanium dioxide, and water.
Chemical Properties
solid
Chemical Properties
Bauxite consists mainly of gibbsite, Al(OH)3, and varying amounts of kaolinite, and iron and titania impurities. Because the loss on ignition is high, bauxite must be calcined to high temperatures before use. During calcination, it is converted to a dense grain consisting mainly of corundum, Al2O3, and mullite.
Uses
Ore for production of alumina; adsorbent
in oil refining
Definition
A mineral hydrated form of
aluminum hydroxide; the principal ore of
aluminum.
Definition
A natural aggregate of aluminumbearing minerals, more or less impure, in which the aluminum occurs largely as hydrated oxides. It is usually formed by prolonged weathering of aluminous rocks. Contains 30–75% Al2O 3 , 9–31% H2O, 3–25% Fe2O 3 , 2–9%, SiO2, 1–3% Ti O 2 .
Application
Bauxite is the best raw material for the production of alumina and aluminium. More than 95 per cent of the world's alumina is extracted from bauxite using the Bayer process. Therefore, it is mainly used for the production of primary aluminium metal. The following diagram shows the flow chart for aluminium production:
Health Hazard
Bauxite can be considered to be
a nuisance particulate; long experience with
mining and refining of bauxite has not revealed
significant adverse health effects.
Nuisance particulates have little adverse
effect on lungs and do not produce significant organic disease or toxic effect when exposures
are kept under reasonable control.
Safety Profile
A nuisance dust. Human systemiceffects by inhalation: fibrosis, focal (pneumoconiosis).
