In the world of gemstones, phenomenal gems are some of the most unique and highly sought-after of all. When it comes to chatoyancy, there are several different forms, including cat's eye and asterism chatoyancy, as well as simply chatoyancy. Cat's eye and asterism (star) chatoyancy is a phenomenon known to occur in a handful of different gem types. High-quality, especially chrysoberyl, can exhibit a 'milk and honey' effect, which can be seen when moving a light side-to-side of the gem, concentrating it laterally, which results in one side appearing dark and the other light. Some rare stones may even exhibit 'split eyes' or 'split stars' when exposed to two different direct light sources. As two lights shift, a single eye splits into two, each following one of the lights resembling an opening and closing eye effect. This remarkable phenomenon can also occur with quartz, tourmaline, apatite, beryl, sillimanite, sapphire, garnet, ruby, diopside and moonstone.
Simple chatoyancy is not as pronounced as cat's eye or star chatoyancy, but is equally as beautiful and striking. Simple chatoyancy is also the result of parallel microscopic needle-like inclusions. Simple chatoyancy appears as multiple reflections of small silky and thread-like streaks of light. With only slight adjustments to its viewing angle, simple chatoyancy can cause a stone to change from light to dark and back to light again. Gems such as tiger's eye, hawk's eye, pietersite, seraphinite, as well as charoite are the some of the best-known gems that possess simple chatoyancy.