The cleavage properties of diamond

Summary

Calculations of the cleavage energies of various planes in diamond indicated the presence of cleavages other than those already known. A careful goniometric study of several crystal fragments in Sir C. V. Raman’s collection revealed numerous other cleavages. The presence of the following cleavage has been definitely established: (111), (221), (110), (322), (331), (211) and (332). The (111) cleavage was found to be by far the most perfect and most abundant, while (221) and (110) cleavages were not uncommon. It is suggested that the perfection of the (111) cleavage is not merely because that plane has the minimum cleavage energy but also due to the fact that on either side of the plane of easy cleavage lie layers of atoms having three times the cleavage energy. It was also found that diamond definitely has curved fractures and the theory developed in the earlier part of the paper accounts for the existence of these.