Where is Kaolinite found?
Al2Si2O5(OH)4
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Open the appKaolinite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Kaolinite
Cornwall, England
Historically significant and still active kaolin mining region, particularly around St Austell, formed from the hydrothermal alteration of granites.
Georgia, USA
One of the world's largest and highest-quality kaolin deposits, primarily in the 'Fall Line' region, formed from the weathering of crystalline rocks and subsequent deposition.
Brazil
Significant deposits, especially in the Amazon region, often associated with deeply weathered crystalline basement rocks.
China
The name 'kaolin' is derived from Gaoling (Kaoling) Hill in Jingdezhen, Jiangxi Province, where it was historically mined for porcelain production.
Australia
Various deposits, including those in Western Australia and Victoria, often associated with weathered granitic terrains.
Collecting tips
- Look for weathered outcrops. Kaolinite is a product of weathering, so search in areas with deeply weathered igneous or metamorphic rocks, especially those rich in feldspar.
- Check for white, earthy masses. Kaolinite often forms soft, white to off-white, earthy masses that can be easily crumbled. It will feel smooth and somewhat greasy when dry.
- Test for plasticity when wet. Pure kaolinite has low plasticity, but when mixed with water, it forms a paste that can be molded, though less plastic than other clays like montmorillonite.
- Observe associated minerals. Kaolinite is often found with quartz, muscovite, and unweathered feldspar remnants in its parent rock. Iron oxides may impart reddish or yellowish hues.
- Consider geological context. Areas with ancient peneplains, tropical or subtropical climates (past or present), and regions of hydrothermal alteration are prime locations for kaolinite deposits.
Quick Check
- Color:
- White to off-white
- Luster:
- Dull, earthy
- Streak:
- White
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