QUICK NOTES ON BAUXITE

By Steven Marquez

Bauxite is the most important ore of aluminum. Bauxite is not a mineral since it lacks a fixed chemical composition; instead it is a mixture of hydrous aluminum oxides, aluminum hydroxides, clay minerals; and insoluble materials such as quartz, hematite, magnetite, siderite, and goethite. The aluminum minerals in bauxite can include: gibbsite Al(OH)₃; boehmite AlO(OH); and, diaspora; AlO(OH). 

Although aluminum is the most abundant metal in the earth's crust, it is never found as a native element in nature.

Bauxite was named by the French geologist Pierre Berthier in 1821 after the hamlet of Les Baux in Provence, southern France, where he discovered it and found that it contained aluminum. Elemental aluminum was created by a complicated method that used expensive materials, making it more valuable than gold and platinum at that time. Napoleon III of France at a state banquet used an aluminum spoon while his guests used much cheaper gold spoons.

Bauxite, mined in the state of Arkansas since 1896, is the state rock. In Saline County, Arkansas, the town of Bauxite was established as a mining and refining center for aluminum ore. Bauxite is usually strip mined because it is almost always found near the surface.

           FACTS ON FILE

Color: yellow, brown, red

Luster: non-metallic, earthy

Streak: white usually white but iron stain can discolor the streak

Hardness: 1-3 (soft)

Cleavage: none

Specific gravity: 2.0 to 2.6

Fracture: Uneven

Crystal system: amorphous

Cleavage: none

Transparency: opaque

Diagnostic properties: often exhibits a spherical or pisolitic structure 

Chemical composition: variable (aluminum oxides and aluminum hydroxides)

Primary uses: main ore of aluminum, also used as an abrasive

BAUXITE HAIKU (a poem by the scientist Steven Marquez)

Metal trapped in stone

Aluminum hydroxide

Awaiting its fate    

Figure 1. This bauxite specimen is from Bauxite, Arkansas.
It exhibits a pisolitic (spherical) structure and characteristic red iron staining.
Bauxite is not a mineral. It is a rock formed from a soil that has been
leached of silica and other soluble materials in a damp climate. Bauxite is the
main source of the world’s aluminum. Specimen is from the Steven Marquez collection.
Photo © by Steven Marquez.

FURTHER READING

Bardossy, G. (1982). Karst Bauxites. Bauxite deposits on carbonate rocks. Elsevier Sci. Publ. 441 p.

Bardossy, G. and Aleva, G.J.J. (1990). Lateritic Bauxites. Developments in Economic Geology 27, Elsevier Sci. Publ. 624 p. ISBN 0-444-988

Grant, C; lalor, G and Vutchkov, M (2005). Comparison of bauxites from Jamaica, the Dominican Republic and Suriname. Journal of Radioanalytical and Nuclear Chemistry p. 385-388 Vol.266, No.3

ABOUT THE AUTHOR

Steven Marquez is an Earth Science Scholar with the Colorado Springs Mineralogical Society (Colorado). He is a volunteer in the mineral section of the Cripple Creek District Museum. Steven enjoys studying minerals and field work. He is in 8th grade.

Figure 2. Author Steven Marquez is panning gold.
He is active in the study of rocks and minerals in the Pikes Peak region.
Photo © by Steven Veatch.