Tiger's eye is a popular colored stone that displays a unique optical phenomenal effect when a polished stone is moved back and forth in incident light. It is a cryptocrystalline variety of quartz that forms when the mineral crocidolite are replaced by silica. When cut and polished in the right orientation, the gem material produces a tiger's eye-like optical effect. Hat's off to MB&F for popularizing colored stones on watch dials.
