Some mechanical properties of brown and type II diamonds

Abstract

Measurements show that the resistance of brown and type II diamonds to abrasion by the conventional diamond polishing process is appreciably greater than for other diamonds. Also, the cleavage of a type II diamond produces unusually smooth cleavage faces, whereas brown diamonds generally yield rough surfaces. The reasons for this behaviour are analysed using observations of the diamonds in polarized light, in the cathodoluminescent mode of the scanning electron microscope, by observing the scattering of light in the crystal and by the use of X-ray topography. The enhanced abrasion resistance appears to be associated with the high density of dislocations observed in both brown and type II diamonds, and the rougher cleavage of the brown stones with their more complex patterns of growth. Examples are also given of some unusual features of the luminescence associated with the dislocation lines.