Opal is a mineraloid, meaning that it is similar to a mineral but has a non-crystalline nature. Opal comes in both common and precious forms, both of which display unique colors and characteristics. A rarer form by the name of fire opal exists, named after its fiery combinations of yellow, orange, and red colors. Over 90% of opal comes from Australia, with fire opal only found in parts of Mexico.
The Colors of Opal
Opal can feature a full rainbow spectrum of colors, often in the same stone. Unlike diamonds and other gemstones, opal diffracts light rather than refracting it, which brings the various colors out. As a mineraloid, opal has an internal structure that gives it a milky white to bluish black base color. Opal forms under lower temperatures compared to diamonds and other common gemstones; when heated Opal will typically darken and change the color spectrum on the stone. The opal featured in premium jewelry tends to have a whiter base that allows for brighter color sheen.
Some pieces of common and precious opal are attractive enough to undergo only a simple reshaping before becoming a piece of opal jewelry. These are particularly popular with those who prefer a more subtle and earthy look to their jewelry. Enhancing a raw piece of opal into a gemstone can involve a variety of steps taken by jewelers, including cutting, polishing, and the use of natural and synthetic materials to further enhance color and shine. Opal is occasionally placed on top of other stones such as basalt in thin layers; the dark color of basalt further illuminates the colors and transparency. Recent advances in technology have allowed for the creation of synthetic opal in laboratories as well, but most of the opal found in jewelry is naturally occurring.
The use and admiration of opal dates all the way back to the cultures of ancient Greece, Rome, and India. Along the way, opal has been associated with luck and fertility, as well as being the birthstone for October and the astrological signs of Scorpio and Libra. Opal was at one time considered to be the most valuable of all gemstones and commonly traded as a treasured commodity.
The most valuable opal in the world is the over seven pound Olympic Australis Opal, which is worth somewhere in the area of $2,500,000. Found in Australia in 1956, the Olympic Australis was named after the Olympic Games. The Australis has been kept in its original natural form, which has a near 100% color consistency.
Sometimes referred to as “the Queen of Gems,” the opal is an attractive and diverse gemstone that works with a variety of jewelry types. Given the wide array of opal options, there is sure to be a stone that is perfect for all personalities and fashion styles.
Tanzanite, Diamond and Opal Ring by Allurez
Valuable display of Opals by Dierdre Wollard on Flickr Creative Commons