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Kaolinite identification and geology

Kaolinite mineral reference specimen

Clay mineral forming from weathering of aluminum-rich silicates, especially feldspar. Primary component of kaolin clay. Color: White, sometimes stained. Luster: Earthy to pearly. Streak: White. Cleavage: Perfect basal. Hardness: 2-2.5. Transparency: Translucent to opaque. Crystal system: Triclinic. Chemical formula: Al₂Si₂O₅ OH ₄. Specific gravity: 2.6. Formation: Forms from chemical weathering and hydrothermal alteration of aluminum silicates, especially feldspars. Common geological settings: Worldwide; Georgia USA , Cornwall UK , China; major industrial clay mineral. Common look-alikes and related entries: Talc, Halloysite, Illite.

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Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T14:36:48.818052+00:00
Review status
Published; not independently peer-reviewed
  • IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
  • Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.

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Common questions

What is Kaolinite?
Clay mineral forming from weathering of aluminum-rich silicates, especially feldspar. Primary component of kaolin clay.
How can you identify Kaolinite?
Compare several properties rather than relying on colour alone. This entry records colour: White, sometimes stained; lustre: Earthy to pearly; streak: White; Mohs hardness: 2-2.5; cleavage: Perfect basal; crystal system: Triclinic; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Kaolinite form?
Forms from chemical weathering and hydrothermal alteration of aluminum silicates, especially feldspars.
Where is Kaolinite commonly found?
Worldwide; Georgia USA , Cornwall UK , China; major industrial clay mineral.
What is Kaolinite commonly confused with?
Kaolinite may be confused with Talc, Halloysite, Illite. Compare multiple diagnostic properties because colour and surface appearance can overlap.

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