The difference between white corundum and brown corundum
Brown fused alumina is made of bauxite, anthracite and iron filings, and is smelted at high temperature in an electric arc furnace. During the smelting process, the carbon in the anthracite reduces impurities such as silicon oxide, iron oxide, and titanium oxide in the bauxite to metals, and these metals are combined to form a ferroalloy, which settles to the bottom of the furnace due to its larger specific gravity than the corundum solution. The corundum solution separates. Only a small amount of impurities are included in the corundum frit.