Phenomena gems get their dazzling special effects from the way they interact with light. Their colors and effects may appear to float inside or outside the gems bodycolor. Some of the phenomenal gems are opal, sunstone, moonstone, and fire agate. The stronger the phenomenal effect the more valuable the gemstone.Opal is the most known phenomenal gem, it has a rainbow of color it is called its play of color. Unlike some gemstones opal is not a crystal ,it is made up of tiny spheres of silica it is the same chemical that is in quartz. A opal has to have the right conditions , light waves bend around the spheres  and break up into the different colors, the size of the spheres will determine how much color the opal will display.Small spheres will break up and form green and blue colors, larger spheres will form colors of yellow, orange and red. In any opal large patches are preferred so there is no blank or dead spots. The finest opal has a black bodycolor with large patches of color. Opal was thought to be a doorway for your psychic abilities. People thought Opal was bad luck, but it was thought by the ancient people to be very lucky and worn to bring out your inner beauty. Moonstone is the only gem that displays what is known as Adularescence, when light strikes a moonstone's alternating growth layers there is a soft glow of color that seems to float across the gem. The best color in moonstone is a light blue with a bright blue adularescence. When you take a moonstone and move it back and forth you will see the adularescence.This gem was thought to bring love into your life.        it was also thought that the moon was inside the stone and it would help you look into the future.Sunstone  is a form of translucent quartz known as Oregon sunstone. Symbolically it is linked with moonstone. This was a gem associated with the sun due to its sparking orange gold color.Sunstone was used to bring happiness into your life.Chatoyancy is bands of light on certain gems one of them is  a gem called Cat's Eye there is needle-like inclusions in the gem . A Inclusion  can be internal flaws ,such as dark spots, crystals, growth lines, or cracks, In the Cat's Eye the needles line up the , inclusions lie parallel to one another light reflects from the needles creating a silky sheen.If you hold a flashlight up to it the chatoyant band seems to split in two then merge together  it gives you the look of a cat's eye opening and closing. This gem was used for money, beauty, gambling, and protection.  When the needles line up in a several directions and come together in the center a star is born this is called asterism. Fine star rubies ,sapphires and garnets can be very expensive gems. These were used for protection and good luck. A fine star gem has a star that is unbroken extending across the gem and the gem has excellent color. A relatively unknown gem is Labradorite it shows a bright flash of color that shifts across a large area of the stone. Its special effect is called labradorescence caused by light interacting with thin layers in the stone. Iridescence is the rainbow streaks that you see in soap bubbles  this is visible in fire agate and some pearls [in pearls it is called the orient] Another thing you will see is called Aventurescence , in these gems light reflects from small flat inclusions within the gem. such as sunstone. Phenomenal gems can make a dazzling effect in jewelry, some are abundant and others rare,you need to be a connoisseur to appreciate its beauty.