What is Opal?
Opal - Queen of Gems
Opal is often referred to as the "queen of gems" because unlike other gemstones, an outstanding opal can flash all the colors of the rainbow. An opal's play of color is fascinating to watch as the colors dance and shift while rotating the stone. This play of color is opal's signature characteristic and helps to make every opal a unique work of art. Opal is the only gemstone known to man to have the natural ability to diffract light. As light enters an opal the light is split by millions of tiny silica spheres and voids. The arrangement and size of the spheres determines what colors the opal will fire or flash.
Opal is formed when water saturated with silica fills the cracks and seams in a host rock. The solution slowly turns into a gel and after thousands of years of gradual water loss, an opal is formed. It is estimated to take 5 million years to form a layer of opal one centimeter thick. Because of the unique conditions under which opal forms it is nearly impossible to find two opal exactly the same.
Opal of differing qualities occurs in more than twenty countries worldwide, including Zambia, Peru, Canada, New Zealand, Ethiopia, Guatemala, Poland Indonesia, the United States, Brazil, and Mexico. Australia accounts for 96% of all commercial opal and is the top source for precious opal. Australian opal is mined in many locations throughout New South Wales, Queensland and South Australia with the main areas of production being Mintabie, Lightning Ridge, Coober Pedy, Andamooka and Queensland.
Several types of opals are mined today. The most rare and valuable type of opal is the black opal. A black opal has a dark body color, usually dark grey or black, that allows the opal's colors to really stand out. Some black opals cost more per carat than diamonds. Boulder opals are the second most valuable type of opal. Because the opal formed in the cracks of the host ironstone boulders, some very colorful and unique patterns can be formed. Boulder opal is only found in Queensland, Australia. Equal in value to boulder opal is crystal opal. Crystal opal is the term used to describe any opal with a semi-transparent or transparent body color. The last type of opal is white opal. White opal's colors appear very muted, due in part to the white body color. White opal is very common and is much more affordable than the other types of opal.
Today you will find opal used in various qualities and forms. Opal appears in jewelry in grades ranging from milky white to the finest black stones. Opal may be cut into solid cabochons, doublets or triplets. A doublet is formed by attaching a black backing with epoxy to the opal, thereby enhancing the color. A triplet is made by sandwiching a thin slice of opal between a black backing and a piece of polished quartz. Doublets and triplets are both considerably less valuable than solids. Opal inlay has become very popular over the last twenty years. Inlaying involves precisely cutting the stone, grinding it to fit in a channel, and gluing it in place. The opal is then ground down flush with the metal and brought to a high polish. Special care should be taken to prolong the life of your opal jewelry no matter what form or grade you purchase.