Publish Time: 2025-05-27 Origin: Site
Wollastonite: A Versatile Industrial Mineral
#### 1. Basic Properties of Wollastonite
Wollastonite is a naturally occurring white chain-like silicate mineral with the chemical formula **CaSiO₃**, and its theoretical composition is 48.3% CaO and 51.7% SiO₂. Its crystal structure is composed of single-chain silicate tetrahedra, with calcium ions filling the interstitial spaces between the chains, endowing it with unique physical and chemical properties:
- **Physical Properties**: It usually appears as needle-like or fibrous crystals, with a Mohs hardness of 4.5-5, a density of 2.8-3.1 g/cm³, and a melting point of approximately 1540°C. It features low water absorption, high whiteness (above 90%), and excellent thermal stability.
- **Chemical Properties**: It is resistant to acid and alkali corrosion (especially stable in weak acid and alkali environments), has good insulation performance, and can react with metal oxides such as aluminum and magnesium at high temperatures to form a glass phase.
#### 2. Discovery and Naming
Wollastonite was first discovered in New York State, USA in 1818 by the British chemist William Hyde Wollaston, and was named after him. Its formation is mainly related to contact metamorphism and it is commonly found in the contact zones between limestone and igneous rocks such as granite.
#### 3. Industrial Application Fields
Wollastonite, with its unique properties, has become an important raw material in modern industry:
- **Ceramic Industry** (accounting for approximately 50%):
As a flux, it lowers the firing temperature of the body (reducing energy consumption by 15% - 20%), shortens the firing cycle; the needle-like structure enhances the strength of the ceramic body and reduces drying shrinkage cracking.
- **Plastics and Rubber**:
Replace 30% - 50% of glass fiber or calcium carbonate, enhance the tensile strength of composite materials (by 20% - 30%) and dimensional stability, while reducing production costs.
- **Coatings and Papermaking**:
It serves as a functional filler in coatings to enhance the wear resistance and weather resistance of the coating; in the papermaking industry, it is used to improve the whiteness and opacity of paper.
- **Metallurgical protective slag**:
It regulates the viscosity of the molten slag in the continuous casting process, adsorbs impurities in the molten steel, and improves the surface quality of the steel.
- **Environmental Protection Field**:
It is used in wastewater treatment (adsorbing heavy metal ions such as Pb⊃2;⁺ and Cd⊃2;⁺, with a removal rate of over 85%), and as a desulfurizer to reduce SO₂ emissions from coal combustion.
- **Emerging Applications**:
- **Biomedical**: Preparation of Ca-P-Si series bioactive ceramics for bone repair (excellent compatibility with human bones).
- **Friction Materials**: Replacement of asbestos in brake pads, with high-temperature resistance and no carcinogenic risk.
- **3D Printing Materials**: Used as reinforcing phase in ceramic/metal matrix composites.
#### 4. Global Distribution and Mining of Resources
- **Major Production Areas**:
The United States (New York, California), China (Lishu, Jilin; Shanggao, Jiangxi; Yunnan, etc.), India (Rajasthan), Mexico, and Finland. China has an estimated reserve of about 130 million tons, accounting for over 50% of the global total, with an annual output exceeding 700,000 tons (data from 2022).
- **Mineral Processing Technology**:
A combined magnetic separation and flotation process is adopted to extract high-purity concentrate (SiO₂ ≥ 50%, CaO ≥ 45%) with low iron content (Fe₂O₃ ≤ 0.2%).
#### Conclusion
From traditional ceramics to cutting-edge biomaterials, wollastonite has been continuously expanding its application boundaries by virtue of its performance and environmental advantages. With the advancement of carbon neutrality goals, its potential in energy-saving materials, carbon sequestration technologies, and other fields remains to be tapped. In the future, it may become one of the key minerals in the green industry.