History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c17.s3.t1.2

v1.c17.s3.t1.2

Due to chromium and iron, chrysoberyl samples assume green and yellow colour respectively, the more usual green colour often merging into golden yellow. Milky white or greenish white cloudy chrysoberyl samples (not the clear and transparent ones) exhibit chatoyancy. Extending across the curved surface of such stones is a silvery line or streak of light, when viewed in a strong light. These samples are called chrysoberyl or oriental cat’s eye. The phenomenon of chatoyancy is due to the existence in immense numbers of microscopically small cavities arranged in a particular direction or a bundle of microscopic channels running parallel to a single direction. When viewed at right angles to this direction, a band of light is visible Table 4 — Gem Categories Of Importance In The Ancient World