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CHAPTER XXIV
ONYX AND SARDONYX
ONYX and sardonyx are varieties of agate with layers in even planes of uniform thickness, thus adapting them to the purposes of cameo engravers. The cameo has a base of one colour and the figure of another. The art of cameo engraving attained a point nearest perfection with the ancient Romans, evidence being supplied by the numerous relics, that are the admiration of modern artists. The word onyx means a finger-nail, and was suggested, it is supposed, by a fancied resemblance to the lustre and appearance of a finger-nail. Of course —if the Greek myth be true—this most beauti­ful instance of stratification in all mineral nature owes its origin to the freak of playful Cupid, and is the only visible and palpable evi­dence we have of the mundane visits of the Goddess of Beauty.
Sardonyx is a variety of onyx in which one layer has the brown colour of sard. Chalce-
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