Opals come in many types and colors, with black being the most expensive. They are indeed a very intriguing stone - sedimentary in nature's development. The value is determined by the base color as well as the many varied colors (fire) exhibited. This effect is called "opalescence." The Harlequin opal has major broad fire plates (angular color planes) resembling patches. Opals of this type, having the rarer secondary colors of teal, purple and yellow in combination with the ever popular red/orange and blue/green, are the most valuable.
Opals are the only stone that require feeding! The color and hues are caused by trapped water surrounding mineral materials. This water, if allowed to escape via tiny cracks and natural or percussive fissures, will first result in the lost of the brilliant color saturation and ultimately a very dull looking and crazed stone. Occasionally feed your opals by rubbing body perspiration or mineral oil over the entire stone (including the underside if reachable), to seal in the trapped water. Do not store in areas of extreme heat or cold and avoid open fire or heat from display lights. Opals stored away (in a safety deposit box for example) can crack, then craze and then disintegrate if left unattended for many years. Opal cutters are reminded to never store uncut stones in glycerin, this will dry out the water, as well, even prior to cutting. It is recommended that opal jewelry not be worn for everyday because of their medium hardness (5.5-6.5 on Mohs' scale). Avoid wearing opals with other items that are in immediate contact and much harder because this can scratch the opal. Clean opal jewelry with a mild soapy mixture or in a commercial jewelry cleaner that specifically says it will not harm opals. Dry and lightly polish the opal with a soft cloth, and "refeed" - (re-oil your opal). Do not clean in an ultrasonic or soak in acids such as detergents or nail polish remover. Minor surface scratches can be removed by repolishing the top surfaces with traditional stone polishing techniques.
See Ralph Miller Jewelers, 28 & 30 West 8th Street, Erie, Pennsylvania for your selection of precious black, white, gray, tiger opal, fire opal, and Bolder opal (Australian or Brazilian), in opaques and transparents - and for any lapidary, goldsmithing or custom designing needs!
