Cubic boron nitride is an ultra hard abrasive too. The microscopic hardness is less than that of synthetic diamond. It has advantages over synthetic diamond in its superior thermal stability and chemical inertness relating to the ferrous metals of the ferric family, therefore, it effectively remedies the deficiencies of diamond in these uses. CBN is produced by heating hexagonal boron nitride to sufficiently high temperature at high pressure in the presence of a metal catalyst. Its crystals are irregular, black with sharp edges. Therefore, an excellent grinding effect is available in grinding.