October’s Birthstone: Opal – The Mysterious Multicolored Gem

Monique Pean Opal Rings
Monique Pean Opal Rings
Photo Courtesy of JewelsDujour.com from Wall Street Journal

My grandmother always told me that opals are bad luck. She loved jewelry and fashion, and in fact worked for decades at Milgrim and Hattie Carnegie specialty stores on New York’s 57th Street. But like many of her generation, she believed the myth that wearing opal brings bad luck — unless, as others say, it happens to be your birthstone.

This myth is thought to have originated in 1829, when Sir Walter Scott published a novel called “Anne of Geierstein,” or “The Maiden of the Mist.” In his book Scott used an opal to symbolize the changing fortunes of his heroin, and critics of the novel said the opal had an “evil influence” because of her terrible ordeals. This bit of folklore briefly reduced the value of opal at the time, but when Australia’s mines began to produce opals commercially in the 1890s, their popularity grew to new heights, continuing to this day.

Color, Play-of-Color, and Pattern

Black Opal
Black Opal
Photo Courtesy of GIA

Scientists do not completely understand the genesis of the opal, but gemologists will tell you it is the only stone in nature with minute spheres of crystal, which produce opal’s magnificent and varied colors. An opal might display a single color, two or three colors, or all the colors of the rainbow. Black opals, which are only found in a 900-square-mile patch of the vast continent of Australia, are the rarest. If you are lucky – yes lucky – enough to own an Australian black opal, you have something unique in the world.

According to the Gemological Institute of America (GIA), play-of-color is the most dominant aspect of an opal’s appearance. No matter the combination of colors, play-of-color must be vivid to command a high rating. Opal connoisseurs prize bright play-of-color over faint play-of-color.

Opal, Fancy Yellow Diamond, Sapphire, Emerald and Diamond Necklace by Oscar Heyman
Opal, Fancy Yellow Diamond, Sapphire, Emerald and Diamond Necklace by Oscar Heyman
Available at Dorfman Jewelers
Mimi So ZoZo Opal and Diamond Earrings
Mimi So ZoZo Opal and Diamond Earrings

Secondary in importance is the play-of-color’s range. If an opal’s play-of-color ranges across the entire spectrum, it is very rare and valuable. In some opals, the play-of-color consists of just one main color and two or more secondary colors. Red is considered the best prominent color, orange the next most desirable, followed by green.

Pattern is the arrangement of an opal’s play-of-color. The GIA likens these patterns to the shapes one sees in the clouds, including Pinfire — small, closely set patches of color; Harlequin — broad, angular, closely set patches of color; Flame —  sweeping reddish bands or streaks that shoot across the stone; and Peacock — mainly blue and green.

Clarity and Cut

An opal’s clarity can range all the way from completely transparent to opaque, depending on type. In black opal, for example, experts prefer an opaque background, while in crystal opal they prize transparency. Each background is best for displaying play-of-color in its individual opal type.

In planning the best cut for an opal, the stone’s color, pattern, and clarity must be taken into consideration. To achieve this goal, the cutter may opt for traditional shapes or cut the opals into large, irregular shapes that keep as much play-of-color as possible.

Here’s a chart from the GIA to help you navigate the complexities of the mysterious opal.  Good luck!

How to Evaluate an Opal - chart courtesy of GIA
How to Evaluate an Opal Chart Courtesy of GIA.edu

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