The Fascinating Beauty of the Opal

By Awake! correspondent in Australia

A POPULAR lyric says that ‘diamonds are a girl’s best friend.’ But diamonds are not alone in being able to dazzle their enchanted owners. Why, for flashing colors and breathtaking beauty, the multicolored opal is in a class of its own!

Opal is a form of noncrystalline silica. Chemically, it is much the same as ordinary sand. However, it contains water within its mineral structure. Centuries ago, a watery silica gel seeped into crevices and cracks in rocks. As the water evaporated, the gel eventually hardened to become opal.

Prospecting for Opal

Freeing opal from its rocky home is no easy task, however. It is found mostly in remote, semidesert areas, where heat, myriads of buzzing flies, and limited water supplies often make life unpleasant. And as with most prospecting endeavors, success depends to a large extent upon chance.

Furthermore, 95 percent of all opal discovered is common opal. It is dull and valueless. Of the remaining opal unearthed, only a tiny percentage is precious opal, or gem opal.

So while fabulous wealth has been the reward of some prospectors, countless others have dug in vain. Picks, shovels, and hammers have been the prospector’s basic tools for decades. First, he digs a narrow shaft into the hard, dry ground until he reaches the clay level where opal is likely to be found. Then he tunnels horizontally, lamp in hand, looking for the flash of color that indicates he has hit a trace of opal.

This method has given way to more expensive equipment. Some commercial companies now reach the opal level by plowing the ground with bulldozers. Most shafts are now sunk with large mechanical drills mounted on trucks. Sophisticated tunneling machines are also used to follow the seams.

Achieving Its Beauty

Of course, opal in the rough is a far cry from the finished product. The rough opal must be cut and polished. Thus it can serve well in rings, pendants, and other jewelry. Notes The World Book Encyclopedia: “Since the beauty of the opal lies in its internal color flashes, it is never cut with facets, like a diamond. Instead, it is cut with a gently rounded convex surface.”

How an opal produces its dazzling displays of color was for many years a mystery. By means of electron microscopes, however, scientists have begun to unlock the opal’s secrets. A diamond produces its colors by refraction, that is, by bending light at the surface of the gem. The opal’s external and internal structure diffracts light, breaking it up into many colors within the stone.

The book Australian Opals in Colour observes: “If the gemstone is tilted around, all of the colours will change. We call this the ‘play of colour’ and it is this property of ever-changing colours which gives opals their distinctive attraction.”

Factors That Affect Price

Before purchasing an opal, however, you should realize that not all opals are solid. A doublet is a thin layer, or veneer, of precious opal cemented to a common opal backing. Triplets are similar to doublets, but to protect them from abrasion, a colorless quartz cap is added. Although such can be quite beautiful, the book Australian Opals & Gemstones​—Nature’s Own Fireworks warns: “Doublet and triplet opals should never be immersed in water, detergents, alcohol or an ultrasonic cleaner, as they are laminated and bonded with a cement.”

Another factor in price is the stone’s base, or background, color. Black opal is generally the most expensive variety. It is called black because of its dark background, but the stone itself has spectacular color variations that are almost limitless. Light, or white, opal is usually less expensive. Although this variety has a pale or white background, it still produces brilliant colors​—pink, red, green, and blue. Equally important in determining an opal’s value is the dominant fire color (red is generally more expensive than green or blue) and the color pattern.

But whether it is a lustrous solid or a more modest doublet or triplet, a shimmering red gem or a modest blue, an opal is a thing of beauty for you to behold and enjoy.

[Pictures on page 24, 25]

About 95 percent of gem opal comes from Australia

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Photos: By courtesy of Australian Overseas Information Service