Silica is present as refractory material in the super duty silica bricks of the crown. It is there in a superstore also in fused silica form. Aluminum oxide is used as corundum or alpha-beta alumina form in furnaces. Alumino-silicate refractories are used in the form of sillimanite, mullite or fireclay. Zirconia is present as zircon, dense zirconia, sinter or fused cast AZS form.

Magnesium oxide is used in the form of periclase or spinel with alumina compound.

The most commonly used refractory materials contain four oxides: MgO, ZrO2, Al2O3 and SiO2. The refractory materials usually contain either a single or a combination of two or three oxides. For example aluminum oxide, zirconia and silica form a AZS refractory. Generally speaking refractories are acidic, basic or neutral depending on the oxide species. Silica and alumina silicate are considered acidic, refractories which are composed of MgO are basic, whereas alumina, zircon and chromium are neutral.

These terms are used to describe the slag character developed during the high temperature reactions with no reference to pH. It is a bad industrial practice to place acid and basic bricks together in direct contact. There is a potential risk of a reaction proceeding with their participation