Magically, from the depths of mineral crystals, stars shine and cat's eyes gleam. Tiny needle-shaped crystals that grew within larger crystals cause these optical effects. Light reflects off the needles, which are commonly crystals of the mineral rutile. Depending on whether the needles grew in three directions or one, the result is a star or cat's eye. To highlight the effect, a gem must be cut as a cabochon and in the correct orientation.