Phenomenal gems are a special category of gems that have unique characteristics beyond their color, luster and hardness that make them special. These stones can be both rare and common, but appeal to the senses of someone who truly appreciates the distinctive quality of these gemstones. The common enominator amongst these stones are their reaction to light.
1. Star Gems.
These gems display an effect called asterism. Due to the structure and distribution of the inclusions inside the stone, light reflects of its surface to display either 4 or 6 rays. These rays resonate from a focal point and make the light look like a star. The most common stone to display this ability is the Star Sapphire or Star Ruby. The most common cutting to get the best effect out is as a cabochon, to give a smooth surface for light to reflect from.
2. Cat’s-Eye Gems.
These gems display an effect called chatoyancy. This phenomenon is also caused by the unique placements of parallel inclusions inside the stone, as a result of which, when light reflects off the surface it shines in particular as a distinct line along the entire stone. Again, this effect is best viewed on a cabochon. Common stones are Cat’s-Eye Tourmalines.
3. Color Change Gems.
These gems display a change of color when struck by different lights. Their ‘white light’ and ‘yellow light’ colors can be strikingly different, and result in extremely rare stones. The rarest of these which are also extremely popular are Alexandrite Chrysoberyls. It can go from a soft purplish red to a striking greenish blue.
4. Play-of- color and Iridescence.
These stones display a rainbow of colors or layers of colors as light moves across them. Common examples of these stones are Opals, Pearls and Ammonites.
5. Labradorescence and Aventurescence.
These stones scatter incoming light and disperse different colors to their original color. It’s a similar effect as the Play-of- color, however, the dispersion is caused as the light moves across the stone. For example, Labradorite is a stone which appears grey in color, but provides flashes of blue (can also include green and yellow) in certain angles.