The principal superhard materials are found as phases in the boron-carbon-nitrogen-silicon family of elements. Of these, the superhard materials of commercial interest include silicon nitride (Si3N4), silicon carbide (SiC), boron carbide (B4C), diamond, and cubic boron nitride (CBN). This Article describes the synthesis of diamond and cubic boron nitride (CBN) for transforming a crystal structure from a soft hexagonal form to a hard cubic form. Polycrystalline diamond (PCD) or polycrystalline CBN (PCBN) are produced by sintering (or binding) many individual crystals of diamond or CBN together to produce a larger polycrystalline mass. The Article also provides useful information on the physical properties of diamond, CBN, and sintered polycrystalline diamond. Further, the Article describes superabrasive grains that are commercially available in a range of sizes, shapes, and qualities. Diamond or CBN grains can be used as loose abrasives, as bonded abrasives in grinding wheels and hones, and as bonded abrasives in single-point applications such as turning tools, dressers, and scribes. Finally, the Article provides a short note on the applications of ultrahard cutting tool materials of sintered PCD or PCBN.