A fire brick is a block of refractory ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. A refractory brick is designed mainly to withstand high heat, but should also usually have a low thermal conductivity to save energy.
Principal raw materials for firebrick include fireclays, mainly hydrated aluminum silicates; minerals of high aluminum oxide content, such as bauxite, diaspore, and kyanite; sources of silica, including sand and quartzite; magnesia minerals, magnesite, dolomite, forsterite, and olivine; chromite, a solid solution