Kaolinite

Kaolinite is a white to off-white clay mineral that commonly occurs as earthy, powdery masses or compact, fine-grained aggregates.

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Information about Kaolinite

Kaolinite is a white to off-white clay mineral that commonly occurs as earthy, powdery masses or compact, fine-grained aggregates.

It often forms soft, chalky lumps and occasionally in pseudo-hexagonal platelets visible under a microscope. Its texture is typically smooth and soft, and its luster ranges from dull to pearly on cleaved surfaces.


Uses and History

Kaolinite is one of the most important industrial minerals, extensively used in ceramics, particularly in the production of porcelain and fine china.

It is also a key ingredient in paper manufacturing, where it serves as a coating and filler to enhance brightness and smoothness. Kaolinite is used in the production of paints, plastics, rubber, and as a raw material in the chemical industry for producing aluminum sulfate. It is also used in cosmetics as a mild exfoliant and as an absorbent in face powders.

The name kaolinite derives from the Chinese “Gaoling,” meaning “high ridge,” where it was first mined in the Gaoling village, Jingdezhen, Jiangxi, China. It was first described as a mineral in 1637 by Song Yingxing but was mined for hundreds of years before that, and was known as ‘kaolin earth’.

Kaolinite played a crucial role in the early development of porcelain in China, which was later adopted and refined in Europe during the 18th century. Its discovery in Europe sparked a significant industrial revolution in ceramics and contributed to the widespread use of fine porcelain globally.


Mineralogy

Chemistry
A clay mineral with the formula Al2Si2O5(OH)4.
Colours and Variations

White to cream, brown, yellow-brown, sometimes stained or oxidised.

Streak
White
Luster
Pearly to dull, earthy
Transparency
Translucent to opaque
Fracture
Crystal habit
Crystals are rare. Most often compact, claylike masses formed of microscopic plates.
Mohs hardness
2 – 2.5
Fluorescence
Specific Gravity
2.16 – 2.68
Easiest testing method

Hazards and Warnings

Prolonged inhalation of kaolinite dust may cause respiratory issues like kaolinosis; adequate ventilation is advised when handling in powdered form.

Mineral collectors should wash their hands after handling specimens, to avoid any exposure to potential toxins.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis.

When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

 


Translations

Arabic:

  • كاولينيت

Hindi:

Portuguese:

Bengali:

Indonesian:

Punjabi:

English:

Italian:

  • Caolinite

Russian:

  • Каолинит

French:

Japanese:

  • カオリナイト

Spanish:

  • Caolinita

German:

  • Kaolinit

Korean:

Thai:

Gujurati:

Mandarin Chinese:

  • 高岭石

Urdu:


Further Reading / External Links