ABSTRACT
Silica is the name given to a specific compound composed of silicon and oxygen, the two most abundant elements in the earth’s crust. The natural sources of silica are widely and abundantly available all over the world and are used for making silica refractories. Silica occurs in a variety of crystalline polymorphic forms, for example, quartz, tridymite, and cristobalite and also as an undercooled melt called quartz glass. The polymorphic forms of silica are temperature dependent and one form changes to other on reaching a specific temperature. The selection of a proper raw material and its firing process are important for the silica refractories such that the degree of quartz transformation to the desired form is suitable for the intended application. The firing of silica refractories requires special attention due to its polymorphic changes during heating. Silica refractories are classified mainly into two types depending on the purity or impurity content.
