Tiger's Eye is a chatoyant gemstone that is usually a metamorphic rock that is a golden to red-brown color, with a silky luster. Its hardness on the Mohs scale is 5.5-6, and its specific gravity is 2.64-2.71.
Rutile is a mineral composed primarily of titanium dioxide. Rutile has among the highest refractive indices at visible wavelengths of any known crystal, and also exhibits a particularly large birefringence and high dispersion. Small rutile needles present in gems are responsible for an optical phenomenon known as asterism. Asteriated gems are known as "star" gems. Star sapphires, star rubies, and other "star" gems are highly sought after and are generally more valuable than their normal counterparts.