The Cat's Eye, a semi-transparent stone of the Chrysoberyl family, has a distinct ray of light running across it, which ray has been compared to a drop of water enclosing a beam of light. It is most commonly translucent, of a milky-white colour, but is also found in shades of yellow, red, and brown. It has always been greatly valued in India, where it is regarded not only as a bringer of wealth, but a Talisman to prevent its owner's gain diminishing. The Cat's Eye is also considered powerful against the terrors of the night; it will relieve asthma if hung round the neck, also helps babies suffering from croup, and it is also worn for mental balance, foresight, and general attractiveness. As a popular charm for success in speculation, gambling, and games of chance, it is said to have no equal.
Rock Crystal is a form of quartz, clear and transparent, the name Crystal coming from a Greek word signifying "frozen water" or "clear ice." The magical powers of revealing the hidden secrets of the future supposed to exist in the ball of Crystal is of very ancient origin; and it is said that Saint Augustine believed that Crystal-gazing, as it is called, originated in Persia.
The Moon, the ruler of the House of Cancer, has direct influence upon the intuitive faculties of the brain, through which seers visualise events foreshadowed in the Crystal; making it peculiarly appropriate and sympathetic to subjects of this type, so that it is not surprising that this sign produces some of the best seers. Pliny states that Roman physicians also used the ball of Crystal for cauterising purposes, holding it against the rays of the Sun; they also used them applied externally as a remedy for diseases of the kidneys.