sedimentary

Kaolinite Claystone

Al2Si2O5(OH)4 (Kaolinite)

Hardness: 2-2.5 on Mohs scale; Color: primarily white with occasional cream or pink tints; Luster: dull, earthy; Crystal Structure: triclinic (microscopic); Cleavage: perfect (microscopic); Specific Gravity: 2.6

Hardness: 2-2
Color: primarily white with occasional cream or pink tints
Luster: dull, earthy

Identified June 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the chemical weathering of aluminum-rich silicate minerals (like feldspar) in humid, tropical environments or through hydrothermal alteration. Often found in deposits from the Cretaceous to Tertiary periods.

Uses & applications

Extensively used in the paper industry for coating, ceramics, porcelain production, toothpaste, cosmetics, and as a food additive (thickener). Also used in the manufacturing of bricks and cement.

Geological facts

The name Kaolin is derived from 'Gaoling' (High Ridge), a village in Jiangxi Province, China, where it was first identified. It is a critical component in the production of fine bone china.

Field identification & locations

Identify in the field by its white color, earthy smell when moist, and 'sticky' feel to the tongue (high absorption). Common in the southeastern United States (Georgia), UK (Cornwall), and Brazil. Collectors look for pristine white purity and density.