Faceted diamond grains

A method of producing faceted diamond grains having an average particle size from 1 µm to 20 µm, at least 75% of the source diamond grains having an average particle size and being substantially free of facets is disclosed. The source diamond grains are mixed with metal particles to form a reaction mass. The metal particles have an average particle size no greater than the average diamond particle size. The reaction mass is subjected to a temperature of greater than 1100°C and a pressure of greater than 4.5 GPa to form faceted diamond grains, such that fewer than 50% of the faceted diamond grains form a part of an agglomerate comprising at least two inter-bondedfaceted diamond grains. The faceted diamond grains are recovered from the reaction mass. Carbon may be added to the reaction mass and a tool including euhedral diamond grains formed with the method may be such that the diamond grains are orientated in the tool at an orientation relating to the orientation of the longest dimension of the euhedral grains.