Cat's-Eye                        133
	defined in a strong light, while its boundaries are sharpest in small stones. The effect of the chatoyancy is in great part due to the judicious work of the lapidary, and usually the greatest possible effect is produced by the greatest curva­ture of the surface. Chatoyancy appears only in the cloudy chrysoberyl, and the cloudiness is due to thousands of microscopically small cavities within the stone. The influence of the whims and preferences of royalty on the popu­larity of gems was remarkably illustrated by the sudden favour with which chrysoberyl cat's-eye was invested, when His Royal Highness, the Duke of Connaught, gave his fiancee a ring set with this stone, which vastly increased the de­mand for it and caused a corresponding rise in price. The Minas Novas district in the northern part of the state of Minas Geraes, Brazil, is the most prolific producer of chrysoberyl of the finest colours; most of the specimens are chatoyant. The mineral in this locality occurs associated with rock crystal, amethyst, red quartz, green tourmaline, yellowish-red (vine­gar) spinel, garnet, euclase and white and blue topaz. Chrysoberyl is erroneously inden-tified with, and termed, chrysolite by the Brazil-