cat's-eye

/kats"uy'/, n., pl. cat's-eyes.

1. any of certain gems having a chatoyant luster, esp. chrysoberyl.

2. a playing marble marked with eyelike concentric circles.

[1545-55]

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Any of several gemstones that display a luminous band reminiscent of the eye of a cat.

Grayish green or greenish quartz cat's-eye is the most common type; although it comes from the Orient, it is often called occidental cat's-eye to differentiate it from the rarer, and more valuable, precious or oriental cat's-eye, which is a greenish variety of chrysoberyl. Crocidolite cat's-eye (African cat's-eye) is more commonly known as tigereye. Corundum cat's-eye is an imperfect star sapphire or ruby in which the star is reduced to a luminous zone.

Chrysoberyl cat's-eye with yellow banding on a brown stone

John H. Gerard

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▪ gemstone

      any of several gemstones that, when cut en cabochon (in convex form, highly polished), display a luminous band reminiscent of the eye of a cat; this particular quality is termed chatoyancy. Precious, or oriental, cat's-eye, the rarest and most highly prized, is a greenish chatoyant variety of chrysoberyl called cymophane; (cymophane) the chatoyant effect is due to minute parallel cavities. Quartz cat's-eye, the commonest, owes its chatoyancy and grayish-green or greenish colour to parallel fibres of asbestos in the quartz; although it comes from the East, it is often called occidental cat's-eye to differentiate it from the more valuable oriental (chrysoberyl) cat's-eye. The two may be distinguished by their specific gravities; chrysoberyl is much denser. Crocidolite cat's-eye (African cat's-eye), more commonly known as tigereye (or tiger's-eye), is quartz that contains oriented fibres of crocidolite that have been replaced by silica. Corundum cat's-eye is an imperfect star sapphire or ruby in which the star is reduced to a luminous zone.

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