The number “12” seems to follow a chain of gemstone superstitions. Gemstones were considered to have mystical relationship not only with the Twelve Tribes and the Twelve Apostles but also with the Twelve Angels, the Twelve Ranks of the Devil, and the Twelve Parts of the human body. Some stones were even endowed with astrological significance and were believed to be in sympathy with the twelve zodiacal signs. On the basis of an elaborate system of prognostications, an astrologer was considered able to foretell future events by proper observance of changes in hue and brilliance of the symbolic stones. Aries the Ram, _Bloodstone_ Taurus the Bull, _Sapphire_ Gemini the Twins, _Agate_ Cancer the Crab, _Emerald_ Leo the Lion, _Onyx_ Virgo the Virgin, _Carnelian_ Libra the Scales, _Chrysolite_ Scorpio the Scorpion, _Aquamarine_ Sagittarius the Archer, _Topaz_ Capricornus the Goat, _Ruby_ Aquarius the Water Bearer, _Garnet_ Pisces the Fishes, _Amethyst_ Perhaps in our own space-oriented times the ancient superstitions sympathetically relating certain gemstones with the planets will be revived. In the distant past, moonstone, topaz, and other white stones were believed to be in sympathy with the Moon, diamond and ruby with the Sun, jasper and emerald with Mars, amethyst, topaz, and emerald with Venus, carnelian, topaz, and amethyst with Jupiter, turquoise and sapphire with Saturn, and rock crystal, agate, and emerald with Mercury. Since Uranus, Neptune, and Pluto were unknown to the ancients, these planets have not been represented by gemstones. Of special interest to the American public are birthstones. Many birthstone lists have been proposed, and in order to use this idea to popularize gemstones the American jewelry industry has agreed upon an official list. This list has served to bring about some uniformity in the selection of birthstones for the twelve months. January, _Garnet_ February, _Amethyst_ March, _Aquamarine_ or _Bloodstone_ April, _Diamond_ May, _Emerald_ June, _Moonstone_ or _Pearl_ July, _Ruby_ August, _Peridot_ or _Sardonyx_ September, _Sapphire_ October, Opal or _Tourmaline_ November, _Topaz_ or _Citrine_ December, _Turquoise_ or _Lapis lazuli_ All these associations and strange beliefs have served to create in the general public a mental image of gemstones that gives to them an increased exoticism and mysterious appeal far exceeding their monetary value. [Illustration: {zodiac symbols}] 6 PRINCIPAL GEM SPECIES