ALUMINUM SILICATE

Uses

ALUMINUM SILICATE (Sillimanite) is extensively mined as a byproduct of beach mineral sand operations in South Africa and Australia. Sillimanite minerals are predominantly used in refractories and technical porcelains. Sillimanite refractories cut into various shapes and sizes or made out of bonded particles are used in industries like cement, ceramics, glass making, metal smelting, refinery and treatment, tar distillation, coal carbonization, chemical manufacture, and iron foundries.

Reactions

ALUMINUM SILICATE (Sillimanite), kyanite, and andalusite are all mullite-forming minerals, that is, on firing they decompose into mullite and vitreous silica according to the chemical reaction:
3Al₂SiO₅ —> Al₆Si₂O₁₃ + SiO₂
However, sillimanite does not change into mullite until the temperature reaches 1545°C with a volume expansion of 5 to 6 vol.%.