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CHAPTER XXXI.
ROCK CRYSTAL.
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EREOF the common opinion hath been, and still remaineth among us," said the learned Sir Thomas Browne, in his famous work on Vulgar Errors, in
1646, "that Crystal is nothing else but ice or snow concreted, and by
duration of time congealed beyond liquation. Of which assertion, if
prescription of time and numerosity of assertors were a sufficient
demonstration, we might set down herein as an unquestionable truth ;
nor should there need ulterior disquisition. For few opinions there
are which have found so many friends, or been so popularly received
through all Professions and Ages." The word crystal is, in fact, a standing testimony to this strange belief, since it owes its origin to the Greek word krustallos, which
means "ice." Pliny, Seneca, and other ancient writers—not to mention
Austin, Gregory, Jerome, and several early fathers of the Church—have
given their adhesion to the opinion that Rock Crystal is nothing but
water congealed by a cold so intense that ordinary methods fail to melt
it.
Modern
science, however, dispelling such illusions, has proved that Rock
Crystal is a pure and limpid form of Quartz—a natural variety of silica.
Rock
Crystal is found in a variety of forms, sometimes of extraordinary size
and beauty. Its colour varies from pure white to greyish-white,
yellow-white, yellowish-brown, clove-brown, and black. According to its
colour it receives a variety of names : thus the yellow is known as Citrine and False- Topaz, the brown as Cairngorm and
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