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Mineral & Geology

Imerys Kaolin is the world's largest producer of quality kaolin and has deposits and production plants in the UK, USA, France, Belgium, Sweden and Brazil. Our products offer unique and specific geological characteristics that can be tailor-made to meet the changing demands of the markets that we serve.

In order to guarantee a long-term supply for its customers and secure its future growth, Imerys Kaolin aims to constantly have at least 20 years of reserves for all its minerals. To achieve this, the Group is constantly prospecting, optimizing its portfolio of deposits and acquiring new resources.

  • Properties & Production

    Kaolin (china clay) is a hydrated aluminum silicate crystalline mineral (kaolinite) formed over many millions of years by the hydrothermal decomposition of granite rocks. Hydrous kaolin is characterized 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.

    Imerys kaolin brands are renowned for high quality and reliability.

    Whatever your kaolin needs, Imerys Kaolin can offer engineered product solutions specialized for you.

    Quick View

    Mineralogy: Kaolinite with minor amounts of mica, quartz and feldspar or illmenite
    Particle Shape: Platy, with typical aspect ratio of 20:01
    Specific Gravity: : 2.6
    Refractive Index: 1.56
    MOH Hardness: 2.5
    Moisture: (max %) 1.5
    pH: 5-7.5
  • Properties

    Calcined Kaolin is an anhydrous aluminum silicate produced by heating ultrafine natural kaolin to high temperatures in a kiln. The calcination process increases whiteness and hardness, improves electrical properties, and alters the size and shape of the kaolin particles.


    Calcination occurs in two steps.
    At 700°C the dehydroxylation of the kaolin is complete forming a poorly crystalline metakaolin.

    At 980°C an amorphous defect spinel is formed which undergoes a transformation, with mullite recrystallising in an amorphous glass at temperatures above 1100°C. Products produced within this temperature range provide excellent properties in rubber compounds, especially when coated with silane, improving mechanical properties and chemical resistance. Silane treatment further enhances rigidity, toughness and dimensional stability in polyamide moldings.

    Quick View

    Mineralogy: Metakaolin or amorphous, aluminum silicate (defect spinel)
    Particle Shape: Irregular, with surface voids
    Specific Gravity: 2.6
    Refractive Index: 1.56
    MOH Hardness: 4-5
    Moisture: (max %) 0.5
    pH: 6-8



Product Spotlight:




A high brightness calcined kaolin for direct thermal and thermal transfer paper coatings
For further information please click here


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