Tiger's-eye is chatoyant quartz. It ranges in color from brownish yellow to brown or reddish brown with iron oxide being the coloring agent. The gemstones fibrous structure causes it to be chatoyant. The chatoyancy appears because wavy lines of very fine crocidolite fibers run perpendicular to the cutting direction, flat stones and tablets can have many bars or bands perpendicular to the wavy lines. Cabochons exhibit an eye similar to the eye of a cat.
Other varieties of chatoyant quartz include hawk's-eye which is usually a grayish blue color, zebra tiger's-eye which is tiger's-eye with grayish blue streaks and cat's-eye quartz which is semitransparent to translucent usually brownish yellow to greenish brown and must be cut en cabochon to exhibit an eye.