CXXXIII. Microscopic studies on beryl crystals.—II. Dislocations and the growth of prism faces

Abstract

It is shown that the type of growth predicted by the dislocation theory of growth takes place on faces of beryl. The growth layers, in general, produce a complex topography. The behaviour of layers at surface obstacles is discussed. Examples are given of the propagation of a dominant layer group past lines of dislocations, and inactive dislocation groups, and the mode of propagation by cross-linking is discussed. Typical examples of lineage boundaries and limited slip zones are shown; these features are observed as lines of dislocations. The dependence of growth rate of the layers on crystallographic orientation is considered. The types of layer structure observed on natural and synthetic crystals are compared. It is shown that the dislocation theory of growth can be applied to give such information as the supersaturation and temperature at which growth took place.