Calcined alumina is produced by firing alumina at controlled high temperatures to achieve varying degrees of calcination, converting it into alpha alumina—its densest and most stable form. Depending on the calcination level, alpha alumina content can range from 5% to nearly 100%. The material appears as crystalline agglomerates, with particle size increasing as calcination intensity rises. It is widely used in refractories, glass, ceramics, and enamel applications where thermal stability and strength are critical.