quartz cat’s-eye

Quartz cat's-eye is a gemstone that displays a luminous band, known as chatoyancy, when cut in a convex, polished form. This effect is caused by parallel fibers within the quartz, often from asbestos, which give it a grayish-green or greenish color. While precious cat's-eye is a rare chrysoberyl called cymophane, quartz cat's-eye is more common. Another variety, tigereye, is quartz that contains oriented fibers of crocidolite replaced by silica, resulting in a yellow to brown color with a golden luster. These gemstones have been used since antiquity as ornamental stones.123