Kaolinite clay occurs in abundance in soils that have formed from the chemical weathering of rocks in hot, moist climates—for example in tropical rainforest areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolinite decreases, while the proportion of other clay minerals such as illite (in cooler climates) or smectite (in drier climates) increases. Such climatically-related differences in clay mineral content are often used to infer changes in climates in the geological past, where ancient soils have been buried and preserved.

 

The largest use is in the production of paper, including ensuring the gloss on some grades of paper.

In April ***8, the US Naval Medical Research Institute announced the successful use of a kaolinite-derived aluminosilicate nanoparticle infusion in traditional gauze, known commercially as QuikClot Combat Gauze.[*2]

Kaolin is or was also used:

in ceramics. It is generally the main component in porcelain.

in toothpaste

as a light diffusing material in white incandescent light bulbs

in cosmetics

as paint to extend titanium dioxide (TiO2) and modify gloss levels;

for its semi-reinforcing properties in rubber

in adhesives to modify rheology.[*3]

the production of common smoking pipes in Europe and Asia

in organic farming, as a spray applied to crops to deter insect damage, and in the case of apples, to prevent sun scald.

as whitewash in traditional stone masonry homes in Nepal. The most common method is to paint the upper part with white Kaolin clay and the middle with red clay. The red clay may extend to the bottom, or the bottom may be painted black.

as a filler in Edison Diamond Discs.[*4]

as an indicator in radiological dating since Kaolinite can contain very small traces of uranium and thorium.

to soothe an upset stomach, similar to the way parrots (and later, humans) in South America originally used it.[*5] More recently, industrially-produced kaolinite preparations were formerly common for treatment of diarrhea; the most common of these was Kaopectate, which abandoned the use of kaolin in favor of attapulgite and then (in the United States) bismuth subsalicylate.

for facial masks or soap[*6]

According to the American National Precast Concrete Association metakaolin is a supplementary cementitious material (SCM). When added to a concrete mix, metakaolin accelerates the hydration of Portland cement.