Microtopographical studies on natural and synthetic quartz crystals

Abstract

Phase contrast and multiple-beam interferometric techniques have been applied to the study of surface structures of natural and synthetic quartz crystals. A summary is given in a tabular form of the observations of growth by spiral mechanism recorded during the years 1949 - 1959. An improved thin-film collodion technique has been worked out and applied to the study of extremely irregular crystal surfaces. The merits of this technique are assessed, and it is shown that with the help of this technique step heights less than 10 can be detected and measured. Spiral patterns on the basal planes and rhombohedral faces, and the vertical striations on the prism faces of Synthetic quartz crystals are illustrated and described. A mechanism of growth of synthetic quartz crystals is proposed, and it is shown that all the results obtained support this proposed mechanism. The curved nature of the profile of spirals on the basal planes, recorded for the first time, is established with the help of the improved thin-film collodion technique. The mechanism of the formation of such a profile is described. Very strange tadpole-shaped features observed on synthetic quartz are described and interpreted. Properties of the growth pyramids on the faces of natural quartz crystals and the information available therefrom about gradients and the direction of flow of mother liquid are given. Also described are associated growth of other crystals, replacement of other minerals by quartz, natural etch figures, surface structures of red quartz etc. The first clear evidence of the growth of natural quartz crystals by spiral mechanism is given. A new approach to the twinning problem is described and Sunagawa's newly proposed mechanism of 'twin formation by a kind of fault' is established for quartz. The surface Structures of trigonal bipyramidal faces are briefly dealt with and a study made of the surfaces of four samples of fused quartz. Finally the effects of a crack produced by an explosion, at a pressure of 24,000 atmospheres, inside a diamond bomb are examined.