Wollastonite

Wollastonite is a calcium silicate mineral belonging to the pyroxenoid group. It has the chemical formula CaSiO3, indicating the presence of calcium (Ca), silicon (Si), and oxygen (O). Wollastonite occurs in nature as a white to gray mineral with a needle-like or fibrous crystal structure. It is named after the English chemist and mineralogist William Hyde Wollaston.

Wollastonite's versatility and range of properties make it valuable in different industries, contributing to the improvement of various materials and products. Its use as a reinforcement material in composite materials and its role in enhancing the performance of ceramics, plastics, and coatings highlight its significance in industrial applications.

Here are some key points about wollastonite:

  1. Chemical Composition: The primary components of wollastonite are calcium, silicon, and oxygen. It is a chain silicate with a calcium-to-silicon ratio of 1:1.

  2. Crystal Structure: Wollastonite crystallizes in the triclinic system and often forms acicular (needle-like) or fibrous crystals. It can also occur in massive or granular forms.

  3. Physical Properties:

    • Color: Wollastonite is usually white, but it can also be gray, brown, or green due to impurities.
    • Hardness: It has a hardness of 4.5 to 5.5 on the Mohs scale.
    • Luster: Wollastonite has a vitreous to silky luster.
    • Cleavage: It exhibits good cleavage in two directions.
  4. Occurrences: Wollastonite is found in metamorphic rocks, especially skarns and contact metamorphic zones. It is also associated with some igneous rocks.

  5. Industrial Applications:

    • Ceramics: Wollastonite is used in the ceramics industry as a fluxing agent. It improves the firing process and enhances the strength and elasticity of ceramic products.
    • Plastics and Rubber: In the plastics and rubber industries, wollastonite is used as a filler to improve mechanical properties, such as tensile strength and impact resistance.
    • Paints and Coatings: Wollastonite is employed in paints and coatings to enhance durability, hardness, and weather resistance.
    • Construction Materials: It is used in the production of construction materials, including cement, plaster, and various building products.
    • Friction Products: Due to its high melting point and low thermal expansion, wollastonite is used as a reinforcement material in brake linings and other friction products.
  6. Reinforcement Properties: Wollastonite's unique properties, including high aspect ratio and low thermal expansion, make it an effective reinforcement material in various applications.

  7. Environmental Uses: Wollastonite has been explored for its potential environmental benefits, such as in soil amendments to improve fertility and as a component in certain environmental remediation processes.

  8. Gemstone Variety: Fibrous varieties of wollastonite, known as "wollastonite cat's eye" or "wollastonite catseye," can exhibit a chatoyant effect resembling the eye of a cat.

Chemical Properties %
Sio2 62-65%
Al2O3 0.64%
Fe2O3 0.42%
CaO 32-35%
MgO 0.59%
K2O 0.09%
Na2O 0.32%
L.O.I 1.19%
Physical Properties Value
L Value 94.84
A Value 0.16
B Value 7.08
Cycle Min 49
Shrinkage 1.64%
Whitness 87.31
Residue (#300) 1.72
Temprature C 1188/1194
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