Bauxite
Rock made of gibbsite, boehmite, diaspore
Common · Al(OH)₃ and AlO(OH), with iron oxides and kaolinite
A sedimentary rock of deep weathering, dull reddish brown, white or tan, made of the aluminium minerals gibbsite, boehmite and diaspore with iron oxides and kaolinite. Named after Les Baux in Provence, where Pierre Berthier found it in 1821; it forms as laterite over granite, basalt and shale in the tropics, or as karst bauxite over limestone. The world's main source of aluminium, a metal of the industrial age: it is refined to alumina by the Bayer process, then reduced by electrolysis in molten cryolite. Strip mined near the surface; Guinea, Australia and China lead today.
Rock
- Kind of rock
- Chemical sedimentary rock
- Also contains
- Goethite, Hematite, Kaolinite
- Deposits
- Lateritic deposit
- Metals
- Aluminum
- How it forms
- Deep tropical weathering (laterite) over granite, basalt and shale, or karst bauxite over limestone.
- Uses
- The main ore of aluminium, refined by the Bayer process.
Identity
- Formula
- Al(OH)₃ and AlO(OH), with iron oxides and kaolinite
- Chemical class
- Oxide
- Also known as
- Aluminium ore
- Ore of
- Aluminum
Crystallography
- Crystal system
- Amorphous
- Habits
- Earthy, Nodular, Massive
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 2
- Density
- 2.5 g/cm³
- Luster
- Dull, Earthy
- Colors
- reddish brown, white, brown, pale yellow
- Transparency
- Opaque
Geology
- Origins
- Sedimentary
- Host rocks
- Volcanic rock, Limestone and chalk
- Associated minerals
- Gibbsite, Boehmite, Diaspore, Goethite, Hematite, Ilmenite
- Geography
- Guinea, Australia, China, France (Les Baux, Provence), Jamaica, Suriname, Guyana
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Bauxite. Wikipedia.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Gibbsite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Böhmite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Diaspore. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- C. R. Hallsworth, R. W. O’B. Knox, BGS Rock Classification Scheme, Volume 3: Classification of sediments and sedimentary rocks (Research Report RR 99-03). British Geological Survey, 1999.
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