Image: <bdi><a href="https://www.wikidata.org/wiki/Q126871368" class="extiw" title="d:Q126871368"><span title="photographer from the United States">Darla Sondrol</span></a></bdi> (CC0)
Bauxite
Mixture of aluminum hydroxides and oxides, primarily gibbsite (Al(OH)3), boehmite (AlO(OH)), and diaspore (AlO(OH))
This sample of bauxite is about 12 cm across, displaying a reddish-brown color and a distinct pisolitic (pea-sized spherical aggregates) texture. It is an earthy, dull-looking rock, characteristic of its mixed mineral composition.
Bauxite Physical Properties
Mohs Hardness
1Crystal System
amorphousLuster
earthyStreak Color
white to reddish-brownCleavage
noneFracture
unevenSpecific Gravity
2Colors
reddish-brown, brown, white, gray, yellowTransparency
opaqueMineral Group
Rock (sedimentary), composed of aluminum hydroxides/oxidesUses
aluminum production, abrasives, refractoriesAssociated Minerals
gibbsite, diaspore, boehmite, kaolinite, hematite, goethiteRarity
commonGeological Context
Bauxite forms as a residual deposit from intense chemical weathering of aluminum-rich rocks (e.g., granites, basalts, shales) in tropical and subtropical climates, where silica is leached away, concentrating aluminum hydroxides.
