Bauxite

Physical Properties

Hardness: 1-3 on Mohs scale; Color: Reddish-brown, white, tan, or gray; Luster: Dull to earthy; Structure: Pisolitic (pea-like) or massive; Cleavage: None; Specific Gravity: 2.0-2.5

Formation & Geological History

Formed by the intense chemical weathering of parent rocks (like granite or basalt) in hot, humid tropical or subtropical climates. It is a residual soil (laterite) where silica and other soluble materials have been leached away.

Uses & Applications

The primary ore of aluminum used in industrial smelting; also used in refractories, abrasives, and as a flux in steelmaking.

Geological Facts

Bauxite is not a single mineral but a mixture of hydrous aluminum oxides. It was first discovered in 1821 by geologist Pierre Berthier near the village of Les Baux in France, which is how it got its name.

Field Identification & Locations

Identify by its earthy appearance and sometimes 'pisolitic' texture (small round clasts). It is feel relatively light and is often found in tropical regions like Australia, Guinea, and Brazil. Collectors look for unique textures and coloration.

Identified on: 4/23/2026

Mode: Standard