Opal – A Kaleidoscope of Color

Since ancient times, opals have been associated with various powers and superstitions, some good and some bad. On the good side, Romans believed opals were a symbol of hope and purity and made one magically invisible; thus, Roman warriors were known to carry opals into battle for protection. Conversely, the bad luck superstitions of opals began in the 19th century with a female character in a Sir Walter Scott novel. The lady wore an opal in her hair and when a drop of holy water fell on it, she died! Queen Victoria (who coincidentally owned several opal mines) was somewhat successful in putting that myth to rest by giving opal jewelry as wedding gifts to all her relatives.

Opal traditionally serves as a birthstone for October and is available in several different types. Solid opals range in base color from “black” (any dark body color) to semi-black, crystal, semi-crystal and opaque “milk” opal. In addition to the base color, opals can also exhibit color patterns, ranging from broad flashes to pinpoint “color play”.

The most valuable base color of solid opal is black, and in all opals the more valuable ones exhibit all colors in their color play. That being said, the presence of pronounced red color is best, followed by orange, yellow, green, blue and violet. Also the intensity or brightness of the color will markedly affect the price. Opals with no color play are known as “common opal”.

Opals are also available as “triplets”, which consist of a thin layer of opal secured between an opaque backing material and a crystal clear cap to protect the stone. This can create a brilliant play of colors. “Doublet” opal is the same as triplet but without the crystal top layer. There is also a natural mix of an opal face on ironstone rock known as “boulder opal”, which is sometimes referred to as “nature’s doublet”.

It is interesting to note that ninety to ninety-five percent of the world’s opals come from Australia, with the main fields located in the South Australian towns of Andamooka and Coober Pedy. The main source of black opal (which is far rarer than white) is in Lightning Ridge, New South Wales, Australia. Other sources of opal include China, Brazil, the United States (California and Nevada), Mexico, and Ethiopia.

Opals are relatively soft at 5 ½ to 6 ½ on the Mohs hardness scale and their toughness is only fair to poor. This makes them easily wearable as pendants or earrings. Customers who purchase opal rings simply need to be advised to handle and wear them with care. Opal jewelry can be cleaned with a very soft brush and mild soapy water, then rinsed with water and polished with a soft cloth. Doublets and triplets generally should not be submerged in liquids which could penetrate between the layers and cause them to separate.

One last thing to be aware of is that opals can be re-polished if scratched. Also, there is no need to oil them or soak them in water or glycerine after they have been cut and polished. Most cracking or crazing occurs very early in an opal’s life and the weak ones can be weeded out at that time.

Sharon S. Axelson
Graduate Gemologist, Gemological Institute of America
Certified Gemologist Appraiser, American Gem Society

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