A cubic boron nitride-containing high-density inorganic composite is prepared by mixing cubic boron nitride with a powdered inorganic compound capable of forming a rigid sintered article having a density of at least 85% and a Vickers hardness of at least 800, which does not promote the conversion of cubic boron nitride into graphite-type phase boron nitride (hBN). The powder mixture is compressed into a mold, and fired at low pressure of between 1,000-2,000 MPa, at a temperature of not more than 1,500.degree. C., under which conditions the cubic boron nitride does not convert to hBN, but is sufficiently metastable to permit the formation of the high-density inorganic composite.