The microstructure of dodecahedral faces of diamond

Abstract

With the help of multiple-beam interferometry and the light-profile microscope, a study is made of the microtopographies of the faces of six dodecahedral diamonds. The dodecahedral faces show either striations or characteristic oriented network patterns. Interferometry shows the striations are narrow shallow ruts, often less than 50 Å deep. The network patterns consist of a crosswork of very shallow ruts, either curved or straight, the straight ruts being crystallographically oriented, enclosing small regions which are highly curved (convexly). The topographical details are evaluated with high definition interference fringes. Resolution in extension is 0.75μ and in depth appreciably better than 50 Å. Mild etch experiments conducted on the dodecahedral faces produce striking crystallo- graphically oriented linear networks. These networks are identified with those we report on natural faces. It is conjectured that there exist invisible dislocation networks on the surfaces of natural dodecahedra, the outlines of which are the first regions to be preferentially attacked by the etchant. When a face which already exhibits a natural network is subjected to etch, the attack first deepens the existing linear boundaries of the network preferentially. It is considered that the observed natural networks have arisen through some natural solution process, since they so closely resemble both in appearance and in behaviour the artificially etched networks. Dodecahedral faces appear to be more subject to natural solution processes than octahedral faces.