Synthetic Diamonds:

Synthetic diamond, man-made diamond that is usually produced by subjecting graphite to very high temperatures and pressures. Synthetic diamond resembles natural diamond in most fundamental properties, retaining the extreme hardness, broad transparency (when pure), high thermal conductivity, and high electrical resistivity for which diamond is highly prized. Because synthesis is an expensive process, large stones of gem quality are rarely made. Instead, most synthetic diamond is produced as grit or small crystals that are used to provide hard coatings for industrial equipment such as grinding wheels, machine tools, wire-drawing dies, quarrying saws, and mining drills.