**1.1.4 Alumina (Al2O3)**

Melting point of alumina is about 2000 0C. It is the most durable refractory material to mechanical loads and chemical materials at middle temperature levels. Relatively low melting point limits its application. It doesn't dissolve in water and mineral acids and basis if adequately calcined. Raw alumina can be found as corundum with silicates as well as compounds of bauxide, diaspore, cryolit, silimanite, kyanite, nephelite and many other minerals. As its purety rises, it becomes resistant to temperature, wear and electricity.
