Kaolin is a sub-group minerals kaolinite as the main component of the soft clay minerals and non-clay mineral types. Kaolinite minerals is less than 2μm from the small sheet or tubular form of kaolinite group minerals Al4 [Si4O10] (OH) 8. Kaolin hydrous aluminum silicate because of its chemical composition, layered structure, and particulates, have many common minerals do not have special properties. Extensive use of kaolin and its excellent physical properties are inseparable. Quality of pure white kaolin with a high, soft and easily dispersed suspension in the water, good plasticity and high adhesion, excellent electrical insulation properties and good acid solution, low cation exchange capacity, high refractoriness other physical and chemical properties. 
 The main physical properties of kaolin: 
 1, Color: The color is white kaolin or nearly white, the highest whiteness greater than 95%. 
 2, hardness: the hardness of soft kaolin is generally 1-2, sometimes hard kaolin up to 3-4. 
 3, Plasticity: Plasticity refers to the use of crushed kaolin reconciliation of the right amount of water, kneaded into mud pie, in the external force can be changed from the form without the risk of cracks, out of force, kaolin can maintain the shape when the force performance Kaolin has a good molding, drying and sintering. 
 4, dispersion: dispersion of kaolin is dispersed in water and nature in suspension or as suspension, anti-flocculation of kaolin in water, easily dispersed, suspended, can form a stable and good suspension. 
 5, electrical insulation: Kaolin has a good electrical insulation properties, 200 ℃ when the resistivity is greater than 1010Ω ? cm, can be used for cable fill. 
 Chemical properties: 
 1, chemical stability, good acid soluble kaolin. 
 2, cation exchange capacity. Cation exchange capacity of kaolin is in the PH value of 7 conditions, the kaolin can exchange cations down the total, including the exchangeable bases and exchangeable hydrogen, in units of mmol / g, 1g of dry samples of each can only exchange cation exchange capacity is generally 0.03-0.05mmol / g. 
 3, the refractoriness. Kaolin chemical composition of Al2O3 and SiO2, it has excellent fire resistance, refractoriness is 1770-1790 ℃.