A single crystal diamond grown by microwave plasma chemical vapor
deposition annealed at pressures in excess of 4.0 GPa and heated to
temperature in excess of 1500 degrees C. that has a hardness of greater
than 120 GPa. A method for manufacture a hard single crystal diamond
includes growing a single crystal diamond and annealing the single
crystal diamond at pressures in excess of 4.0 GPa and a temperature in
excess of 1500 degrees C. to have a hardness in excess of 120 GPa.