Sillimanite
Sillimanite (also known as fibrolite) is an aluminosilicate mineral commonly found in metamorphic rocks, especially schists and gneisses. It typically forms long, slender, needle-like or fibrous crystals and is indicative of high temperature metamorphism. The mineral was named after the American chemist Benjamin Silliman.
Chemical Composition
- Chemical formula: Al2SiO5
- Mineral class: Aluminosilicate
- Crystal System: Orthorhombic
- Common colors: Colorless, white, yellow, brown, green, blue, gray
- Hardness (Mohs): 6–7.5
- Related minerals: Andalusite, Kyanite (polymorphs with same composition).
Uses of Sillimanite
- Refractory Industry: Sillimanite is a crucial raw material for making high-alumina refractories, mainly bricks, shapes, mortars, and castables, due to its ability to withstand high temperatures and chemical corrosion.
- Glass, Iron, and Steel Production: Extensively used as refractory lining material in furnaces, kilns, and foundries.
- Ceramic and Electrical Industries: Used in porcelains, precision casting, and sanitary ware.
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Other Applications:
Foundry sands, abrasives, and sometimes in gemstone form (cat’s eye variety) for jewelry.
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