Kaolinite
Description
A hydrated aluminum silicate mineral which is the principal constituent of Kaolin clay. Kaolinite crystals have a lamellar or plate-like structure that gives the clay its slippery feel. It is a natural alteration product of aluminum silicate rocks, such as feldspar. Pure kaolinite is a primary clay. Most secondary clays contain only a small percentage of kaolinite (Fournier 1996). One exception is ball clay found in Wareham, England.
Synonyms and Related Terms
china clay, kaolin; gaoling (Chin.); Kaolinit (Deut.); caolinita (Esp.); kaolinite (Fr.); kaolien (Ned.); kaoliniet (Ned.); caulinite (Port.);
Hazards and Safety
Noncombustible.
ThermoFisher: SDS
Physical and Chemical Properties
Insoluble in water, cold acids and alkalis.
Monoclinic system with with hexagonal, plate-like crystals 0.1-1.0 micrometers.
Perfect cleavage in one direction. Plastic when wet. Brittle when dry.
Fracture = earthy (friable). Luster =dull to pearly. Streak = white.
| Composition | Al2Si2O5(OH4) |
|---|---|
| Mohs Hardness | 2.0 - 2.5 |
| Density | 2.6-2.63 |
| Refractive Index | 1.558; 1.565; 1.564 |
Resources and Citations
- R. Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Co., Radnor, PA, 1996.
- Mineralogy Database: Kaolinite
- Encyclopedia Britannica, http://www.britannica.com Comment: "kaolinite" [Accessed December 4, 2001].
- Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Wikipedia: http://en.wikipedia.org/wiki/Kaolinite (Accessed Sept. 7, 2005)
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966