Optical Phenomena In Gemstones
We are fascinated by the precious gemstone and they have endless mysteries. Precious gemstones are fascinated by the people since ancient era. Not only they are fascinated across the world but each gem has an innate power harnessed by human beings for their good effects.
Optical Phenomenon’s in Gemstones
Adularesence: This phenomenon represents reflecting blue sheen on the domed cabochon surface of Moonstone. This is created by the interaction of light with layer of little “albite” crystals in the moonstones. The blue shimmer is determined by the thickness of layer of the tiny crystals; thinner is the layer, better the blue flash. If we look over the metaphysical properties of Moonstone it includes nurturing, mothering sensitivity and humanitarian love. Moonstone is an excellent gemstone for female and it is the alternative gem for Pearl.
Asterism: The gem of low quality is cut as cabochon. In these gems and stone when light falls it makes a star like rays called as asterism. There are 4 ray and 6 ray stars observed normally. This appears due to the orientation of needle like inclusions. Now, what are inclusions? Inclusions are common rutile. Star of Bombay is one of the famous Sapphires representing Asterism.
Chatoyancy: This is a French word. Chat in French means cat and Chatoyancy means a process which denotes opening and closing of eye. This phenomenon is mostly seen in the Chrysoberyl Cat’s Eye gem with clarity. The Chrysoberyl Cat’s eye is cut en cabochon and displays Chatoyancy.
Iridescence: This is also known as Goniochromism. This is a process where the surface of any material displays several colors as angle changes while view. It is found in the soap bubbles, neck of pigeon and wings of butterfly. This happens because of the passage of light on the irregular spaces which allows light to pass from multiple surfaces causing multi-color visual effect.
Play of colour: Opal displays beautiful play of color. The fire opal of Australia, lightning ridge are famous for this phenomenon. We can assume play of color as iridescence and sometimes wrongly interpreted as fire. Fire is generally a term used for the brilliant flashes of color in a diamond.
Pleochroism: In this phenomenon, gemstone appears to show pattern of different color viewed in different direction. Iolite displays exceptional pleochroism where violet blue color changes to grey color.
Color change: The best example of color change can be seen in Alexandrite. This gemstone appears different in incandescent light as compared to the natural daylight. Alexandrite appears as green during the day time and red in incandescent light. Some Sapphires and Tourmaline also show pattern of color change.
Labradorescence: Labradorescence is the pattern which is directional because of twinning crystals. It is found in Labradorite.