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Kaolin (Kaolinite)

Mineral Properties

China clay or Kaolin is a hydrated aluminium silicate crystalline mineral (kaolinite) formed over many millions of years by the hydrothermal decomposition of granite rocks. Hydrous kaolin is characterised by its fine particle size, plate like or lamellar particle shape and chemical inertness.

Kaolin is named after the hill in China (Kao-Ling) where it was first mined, for many years before it’s discovery in Europe (Cornwall, England) in 1745 by William Cookworthy who was looking for a source of material to produce white chinawares.

Markets for Kaolin

Kaolin is now used in the ceramics, paper, paint, plastics, rubber, sealant, adhesive and chemicals industries.

Formulated into Paint, fine kaolin such as Supreme™ can act as a functional extender of TiO2, reducing formulation cost and improving rheology. Coarser kaolins, Polwhite™ B & Polwhite™ E do not offer so much potential to extend TiO2 but do enhance the dry film properties of primers and undercoats. Polsperse™ 10 offers paint makers the possibility to extend TiO2 in solvent based gloss paints processed using high speed dissolvers rather than bead mills traditionally associated with this type of paint – cutting processing time and increasing efficiency.

Rubber formulations benefit from the use of fine kaolins, Supreme™ and Speswhite™, giving semi-reinforcing properties and good barrier properties, particularly useful in automotive hose applications. Coarser kaolins, Polwhite™ E, can be used in flooring compounds to increase abrasion resistance as well as making the compound cheaper.

In sealants and adhesives, kaolin is used to modify rheological properties.

The Ultramarine Blue industry uses kaolin as a raw material for the synthesis of this important pigment, which is itself widely used in the Performance Minerals industries

IMERYS is the world's largest producer of quality kaolin and has deposits and production plants in the UK, USA, Australia, Portugal and Brazil. Such a wide range of quality kaolin reserves is unique.

Quick View

Mineralogy: Kaolinite with minor amounts of mica, quartz and feldspar or illmenite
Particle Shape: Platy, with typical aspect ratio of 20:1
Specific Gravity: 2.6
Refractive Index: 1.56
MOH Hardness: 2.5
Moisture: (max %) 1.5
pH: 5-7.5

 

European Performance Minerals - Contact Points

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Scanning Electron Micrograph (SEM) of Opacilite - a flash calcined kaolin

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Opacilite is a high whiteness calcined kaolin produced by a revolutionary new rapid heating process. This patented 'flash calcination' technique creates large numbers of tiny sealed voids within the clay particles, resulting in outstanding opacifying properties and a low specific gravity... read more