Rock-crystal The popular belief in his time as to the origin of rock-crystal is voiced by St. Jerome, when, using the words of Pliny, although not citing his authority, he says that it was formed by the congelation of water in dark caverns of the mountains, where the temperature was intensely cold, so that, “While a stone to the touch, it seems like water to the eye.” This belief was evidently due to the fact that rock-crystal was so often found in mountain clefts and caverns. Symbolically, it signified that those within the portals of the Church should keep themselves free from stain and have a pure faith.[138] [Illustration: ROCK-CRYSTAL SKULL, ANCIENT MEXICAN Weighing 475¼ oz. Troy. Now in the British Museum, London. From “Gems and Precious Stones of North America,” by George Frederick Kunz, New York, 1890, p. 285.] The Chinese emperor Wu was devoted to the service of the gods and of the immortal spirits. He built many edifices for religious purposes, and all the doors of these buildings were made of white rock-crystal, so that a flood of light poured into the interior. Although the Chinese texts call this material rock-crystal, it is possible that the name was applied to glass when that substance was but recently introduced into China.[139] Regarding this same “rock-crystal” a humorous tale is related. Muan-fen, a mandarin who had a great terror of draughts, was once received in the palace by one of the Chinese emperors. The doors of the audience chamber were of rock-crystal and were tightly closed, but, because of the transparency of the material, they seemed to be wide open, and the emperor was greatly amused to note that Muan-fen was shivering with cold, although the temperature of the room was quite comfortable.[140] An exceptionally fine specimen of Aztec work is a skull carved out of rock-crystal. It weighs 475¼ ounces Troy, and measures 8¼ inches in width. Ruby The ruby has many names in Sanskrit, some of them clearly showing that it was more valued as a gem by the Hindus than any other. For instance, it is called _ratnaraj_, “king of precious stones,” and _ratnanâyaka_, “leader of precious stones;” another name, applied to a particular shade of ruby is _padmarâga_, “red as the lotus.”[141] The glowing hue of the ruby suggested the idea that an inextinguishable flame burned in this stone. From this fancy came the assertion that the inner fire could not be hidden, as it would shine through the clothing or through any material that might be wrapped around the stone.[142] If cast into the water the ruby communicated its heat to the liquid, causing it to boil. The dark and the star rubies were called “male” stones, the others, more especially, however, those of lighter hue, being considered as “female” stones. All varieties served to preserve the bodily and mental health of the wearer, for they removed evil thoughts, controlled amorous desires, dissipated pestilential vapors, and reconciled disputes.[143]