corundum

Corundum is a crystalline mineral of alpha - alumina. Corundum is a refractory material, and its hardness is second only to diamond. The mineral structure is tripartite crystal system, six square bottom center lattice, crystal is barrel-shaped, short columnar, a few are plate-like or double conical surface with thick stripes. The aggregate is a dense granular mass. There are many variations. Alpha corundum is more stable. Stable chemical properties, acid and alkali resistance. The volume density is 3.95~4.1g/cm3, mohs hardness is 9, melting point is 2050℃, boiling point is 3400~3700℃, melting heat is 246.4KJ/kg, evaporation heat is 6160.7KJ/kg, thermal conductivity (1000℃) is 21.1W/(m·k). Corundum is divided into natural and artificial corundum. In the refractory industry, brown corundum, white corundum, compact fused corundum and plate corundum are more commonly used.