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
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