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Ch. 14: Cat?s Eye

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CHAPTER XIV
cat's-eye
CAT'S-EYE is a well established term in the trade in precious stones, and more than one mineral which exhibits chatoyancy—a French word signifying a changeable, undulat­ing lustre, like the eye of a cat in the dark— is termed, and sold as " cat's-eye."
The true cat's-eye is cymophane, a variety of chrysoberyl, a mineral resembling beryl in con­taining the element glucinum (beryllium), but otherwise distinct. Chrysoberyl is devoid of silica, which beryl possesses, and is, theoretic­ally, composed of glucina, 19.8 and alumina, 80.2. Jewellers variously call chrysoberyl " cat's-eye," " Oriental cat's-eye," or " Cey-lonese cat's-eye." Besides its principal com­ponents, chrysoberyl frequently contains im­purities such as iron and chromium oxides. Chrysoberyl is very hard—8.5, being third in Mohs's scale to the diamond, and when cut is susceptible of a high polish. Heavier than the
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Ch. 13: Turquoise Page of 451 Ch. 14: Cat?s Eye
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