AL Stone is composed of pure synthetic alumina mainly which is made by chemical synthesis and AI₂ O₃, Cr, Na₂ O₃, MgO, etc. are combined. These materials are heated at high temperature (1,600˚C – 1,700˚C) to be hardened fused crystal (d-AI₂O₃). Comparatively the specific gravity of AL Stone (3.0 – 3.6) is rather heavy among barrel stones which property shows excellent grinding efficiency. AL Stone is a stable all round stone and of wide application from heavy job to finishing. Since the hardness is very hard, AL Stone is the most suitable in high speed barrel grinding.