Opal

The most famous opals of today are mined in Australia, which seems to have a nearly unlimited supply of the stunning, fiery gems. Opals are a silica gem that contain about 10-20 percent water. The subtle flashes of light in the gem – referred to as play of light – are the result of light refracting and reflecting between layers of silica and water.

At one time, opals were among the rarest and most expensive of gems, but the discovery of opals in Australia as well as the mistaken superstition that opals are unlucky has brought the price down considerably. To quote one opal aficionado, ‘The only unlucky thing about an opal is in not owning one’.

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Opal buying guide

Opals should be milky white (except, of course, black opals) with distinct color flashes visible when the gem is moved under light. Light opal is the least expensive because of its availability. It should be nearly transparent against a white background. Black opals are more highly valued because of their rarity. The darker the black, the higher the value of the opal is likely to be.

Some things to watch for when shopping for opals include:

Opal jewelry that is backed with gold may actually be a doublet rather than a solid opal. Solid opals are many times more valuable than doublet opals. You should be able to see the stone from both the front and the back.

Take statements like ‘opals with more red in the play of light are more valuable than those that are more blue’ with a grain of salt. The color preference tends to vary from area to area. Instead, decide what color and flash pleases your eye, and look for your best deal on those stones.

Caring for opals

Opal is a relatively soft, porous stone that’s subject to damage in a number of different ways. Because opals contain water, many of the care tips for opals involve water in one way or another. Experts offer the following advice:

If you store your opal jewelry in a safe deposit box, put it in an airtight bag with a piece of wet cloth, or put it in a small jar of water to keep it moist.

Avoid using liquid detergents and soaps around your opal. The detergent could be absorbed by the stone and dull its sparkle.

Do not oil your opal. Glycerin and other oil=based liquids can cause the opal to leech moisture.

Cleaning opals

Opal jewelry can be cleaned in warm water with a little detergent – but limit soaking time in the water to no more than five minutes. Wipe the top of the stone with a soft, dry cloth to remove residues. Never clean opal jewelry in a sonic cleaner or with harsh chemicals.

It’s important to know whether the opals in your jewelry are solid opals, or composites. Composite opals (doublets and triplets) should never be immersed in water, as it can get between the layers and damage the glue or spoil the appearance of the stone. Instead, clean the stone carefully with a moist cloth, or with toothpaste on a fine-bristled brush.

If your opal loses some of its shine, it can be recut or repolished by a jeweler.

Storing your opal jewelry

Opals are soft stones – only 5-6.5 on the Mohs gem hardness scale. They can easily be damaged by hard surfaces, including other jewelry in your jewelry box. To avoid that, always store opal jewelry wrapped in protective cloth or in its own box. If you’re going to store an opal for a long period of time, storing it in a ziplock baggie with a piece of damp cloth will help prevent crazing of the stone.