Cat's eye is a type of gemstone that exhibits a chatoyancy, or a band of light that resembles a cat's eye. This effect is caused by parallel, microscopic tubes or fibers that run through the stone. The most valuable cat's eye stones are made of chrysoberyl, a mineral that is related to emerald and ruby. Chrysoberyl cat's eyes are typically green, but they can also be yellow, brown, or orange.
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