October’s Birthstone: The Opal

The gemstone of the month is one of our favorites, the magnificent opal, full of fire and a rainbow of different colors. Most fine opals come from the dry and remote outback deserts of Australia, where their origins are the stuff of myth and legend. Aborigines believe the creator came down to Earth on a rainbow, in order to bring the message of peace to all humans, and at the very spot where his foot touched the ground, the stones became alive and started sparkling with all the colors of the rainbow – the birth of the opal.

Opals are distinguished by their place of origin and color. There are dark or black opals, white or light opals, milk or crystal opals, boulder opals, opal matrix, “yowah nuts” from Queensland, and also Mexican and fire opals. Opal variations are practically unlimited. They all show that unique play of colors, except for fire opal, which due to its transparency is nevertheless also considered a fine opal specimen. Opals lacking the typical play of colors are simply named “common opal.”

Up to the first half of the 19th century, opals in jewelry were relatively rare. It was in the era of Art Deco that opals became popular for use in jewelry design, with artists of the time preferring them because of their subdued charm, well suited in combination with enamel, another very popular material of those days.

One unique characteristic of opals is their high water content - usually between 2 and 6 per cent, but sometimes even more. This can cause them to become brittle if stored in a dry place or exposed to heat over a long period of time. When dry, opals can turn pale and show fissures. Therefore, opal jewelry should be worn as often as possible, for the gemstone will receive the needed humidity from the air and from the skin of its wearer!

Almost 95 per cent of all fine opals come from Australian mines, with remaining five per cent mined in Mexico, northern Brazil, and also in Idaho and Nevada. Recently the stones have also been found in Ethiopia and in the West African country of Mali.

The best cut to bring out the play of color in a fine opal is a round or oval cabochon, or any other softly domed shape, depending on the raw material. Only the best qualities of fire opal are suited to faceting. Opals’ value is not only determined by the body color, transparency, and factors based on place of origin; it is also important if the stone is transparent, translucent, or opaque.

The most important criterion for determining the price of an opal, however, is the color, play of color, and pattern. If the color red appears when looking through the stone, all the other colors will also appear. The thickness of the opal layer is considered, along with the beauty of the patterning, the cut, weight, and finish. Finally, the total impression or “wow factor” will be decisive in determining how much you will pay for your opal. RGC has a large selection of opal jewelry designs. If you are interested in a valuable specimen, we can advise you, because it takes a real expert to know about the many criteria that determine the price.