Optical and etching studies on cleaved and sawn faces of diamond crystals

Abstract

In chapter 1 a short account of raining and recovery of diamonds is given. Different properties of diamonds are also mentioned briefly. The various theories of crystal growth are described in short in chapter 2.

Chapter 3 deals briefly with the cutting and shaping ofdiamonds. A diamond, when suitably divided may be shaped as desired. Cleaving and sawing which are two different methods for dividing large stones, are described. The shaping of a diamond is achieved in two ways: a) bruting, and b) grinding and polishing. These are also given briefly.

All the experimental techniques employed during the course of the present work are given in chapter 4. It has been emphasized that before making any observations, the specimens should be thoroughly cleaned. This, undoubtedly, was achieved by ultrasonics. Different methods were tried for making a suitable replica for use in an electron microscope. The technique which was suitable of all is given in detail.

Chapter 5 deals with the etching and dissolution. In addition to a cursory survey of the etching and recent developments in general, the existing information on the etching of diamond surfaces is also surveyed. It has been argued once again, in chapter 6, that trigons are due to the growth.

For the first time, a systematic study of the etching of synthetic diamond surfaces has been reported in chapter 7 and theresult is compared with the etching of natural micro diamond surfaces.

Micro percussion marks found on sawn, polished and cleaved diamond surfaces are described in chapter 8. Their presence is attributed to the occurrence of micro cleavages in a direction parallel to the dodecahedron planes.

It is shown in chapter 9 that there is a high degree of resemblance between the etch patterns on matched cleavage faces.On a few cleavage surfaces triangular features were observed, and a possible explanation is given for their occurrence. The etch patterns on different polished dodecahedron sections, given in chapter 10, reveal a sectional history of the growth of the diamond. It has been argued that diamonds have a laminated structure. Evidence has been found which shows that diamonds, most likely, grow around a core. It is also shown that many diamonds are, in fact, very inhomogeneous. Calculations of the density of defects were made on different diamond surfaces andthey were in agreement. The density of defects, on one surface, in type I material was in excess of 4.6 x 105 per mm.2 and in type II material it was less than 8 x 103 per mm. 2.