Abstract
X-ray topographic studies were made of a succession of thin plates cleaved parallel to the basal plane from the bottom to the top of a prismatic crystal of topaz from a pegmatite druse in granite at Naegi District, Gifu Prefecture, Japan. Various types of contrast images, such as growth horizons, growth sector boundaries, dislocations, and inclusions were observed and interpreted. Some growth defects were correlated to optical anomalies. The contrast images vary considerably from the bottom to the top as well as from the center to the edges of the crystal. From these the growth history of the crystal was deduced as follows: (1) initial rapid growth stage; (2) layer growth stage on {001}, {110}, {111}, and (221}; (3) intermission of growth and slight dissolution by newly introduced solution; (4) final layer growth on {120}, {021}, {111}, and {221}.
