Gem, a precious stone. The use of the term implies that the stone has been cut and polished for ornamental purposes. The list of gems is a long one. The principal stones are the carnelian, chalcedony, onyx, sardonyx, agate, emerald, jasper, garnet, jacinth, ruby, beryl, amethyst, sapphire, lapis lazuli, topaz, turquoise, tourmaline, opal, and diamond. The art of engraving precious stones is as old as civilization itself. A gem cut so that a figure stands up is known as a cameo. In case the figures are cut out of the stone, so as to form depressions, the gem is an intaglio. Skilled workmen are able to imitate most gems in various sorts of pottery, porcelain, and glass. Separate articles may be consulted on the principal precious stones. As in the case of flowers, many gems have particular significance, the origin of which it would be difficult to trace. The astrologer claimed that the onyx was under the influence of Saturn; the carnelian, of Jupiter; the diamond, of Mars; the sapphire, of the Sun; the emerald, of Venus; the lodestone, of Mercury; and the crystal, of the Moon. In sentimental matters each month has its gem, and, like flowers, each gem has its significance. The following table carries with it at least the authority of long established tradition: January. . . Garnet. . . .Constancy. February. . . .Amethyst. . . .Sincerity. March. . . .Bloodstone. . . .Courage. April. . . .Diamond. . . .Innocence. May. . . .Emerald. . . .Success in love. June. . . .Agate. . . .Health and long life. July. . . .Carnelian. . . .Content. August. . . .Sardonyx. . . .Conjugal felicity. September. . . .Chrysolite. . . .Antidote for madness. October. . . .Opal. . . .Hope. November. . . .Topaz. . . .Fidelity. December. . . .Turquoise. . . .Prosperity.