Free silica in the form of cristobalite has been observed in the glass.
Sillimanite is most suitable as a raw material for refractory shapes, since normally it does not need to be pre-fired. With the transformation of other forms to mullite powerful stresses are associated which render pre-firing essential before using the minerals in the ceramic bodies if the product is intended to be made are used subsequently above the transformation temperature.
In addition to Sillimanite, Andalusite and Kyanite are also used for the manufacturing of ceramic bodies of mullite type. The Aluvial Kyanite from India is used for mullite bodies after pre-firing. This is not necessary with Sillimanite.
To be contd…..
