The moonstone is believed to bring good fortune and is regarded as a sacred stone in India. It is never displayed for sale there, except on a yellow cloth, as yellow is an especially sacred color. As a gift for lovers the moonstone takes a high rank, for it is believed to arouse the tender passion, and to give lovers the power to read in the future the fortune, good or ill, that is in store for them. To gain this knowledge, however, the stone must be placed in the mouth while the moon is full.[133] Antoine Mizauld[134] tells us of a selenite or moonstone owned by a friend of his, a great traveller. This stone, about the size of the gold piece known as the gold noble, but somewhat thicker, indicated the waxing and waning of the moon by a certain white point or mark which grew larger or smaller as did the moon. Mizauld relates that to convince himself of the truth of this he obtained possession of the stone for one lunar month, during which time he sedulously observed it. The white mark first appeared at the top. It was like a small millet-seed, increasing in size and moving down on the stone, always assuming the form of the moon until, on reaching the middle, it was round like the full moon; then the mark gradually passed up again as the moon diminished. The owner declared that he had “vowed and dedicated this stone to the young king [Edward VI], who was then highly esteemed because he had good judgment in regard to rare and precious things.” Onyx The onyx, if worn on the neck, was said to cool the ardors of love, and Cardano relates that everywhere in India the stone was worn for this purpose.[135] This belief is closely related to the idea commonly associated with the onyx,—namely, that it provoked discord and separated lovers. The close union and yet the strange contrast between the layers of black and white may have suggested this. [Illustration: OBSIDIAN MASK, FROM THE FAYOUM, EGYPT. Twelfth Dynasty. Late De Lesseps Collection. Collection of Mrs. Henry Draper. The obsidian is the typical stone of Mexico.] Pyrites Crystals of iron pyrites (pyrite, native iron disulphide) are sometimes used as amulets by the North American Indians, and the belief in their magic power is attested by their presence in the outfit of miscellaneous objects which the medicine-men use in the course of their incantations. Because these gleaming yellow crystals are occasionally mistaken for gold, the name “fool’s gold” has been popularly bestowed upon them.[136] [Illustration: OBSIDIAN MIRROR, FROM OAXACA, MEXICO. NOW IN TROCADÉRO MUSEUM, PARIS. See “Gems and Precious Stones of North America,” by George Frederick Kunz, New York, 1890, p. 299.] Of this material the ancient Mexicans made wonderful mirrors, one side being usually polished flat, while the other side was strongly convex. Frequently this side was curiously carved with some symbolic representation as appears in the case of a pyrite mirror of the Pinard collection in the Trocadéro, Paris.[137]