Opals are the gem world's silvery mirrors, reflecting back every color in a flash of pastels or a streak of fire. Uncover this enchanting stone.

THE ABCS OF OPAL

Opal, October's birthstone, is sometimes considered the "Queen of Gems," because it encompossed the colors of all other gems. The Romans revered opal as a symbol of hope, fidelity, purity, and good fortune and held it to be second only to the prized emerald.

Opal is a non-crystalline gem that is formed in the ground when silica is liquefied and washed into fissures in the surrounding rock where it solidifies into a hardened gel. Tiny silica spheres create a pattern in opal that causes a prism-like effect that produces flashes of color.

Natural opal occurs in several types: White opal--the most common on the market--has a transparent or white body color with vibrant pastel flashes of rainbow color. Black opal has a blue, gray or black body color that reveals a more dramatic play of color. Boulder opal is most often black opal with some of the ironstone matrix in which it occurred still intact. Crystal or water opal is transparent, colorless opal that contains brilliant flashes of color swimming within it. Fire opal is transparent or translucent opal with a yellow to orange to red body color that may have a play of color or not.

On the Mohs scale of hardness, opal ranks 5-6.5. Opal contains a variable amount of waterdepending on the mine location and depth of extraction. This rather porous gem makes a poor ring stone because it is brittle and fragile. Thought should be given when designing jewelry that protects the stone from harsh wear.

Today, 95% of the world's opal is mined in Australia, known for producing the most spectacular material on the planet. White opal is also being produced in Brazil. Fire and crystal opal is found in Mexico and the United States (Nevada).

Use a soft dry or damp cloth to clean your opal. In fact, Rub the gem periodically with cloth moistened with olive oil to help preserve it. Do not soak your opal in place in chemicals or use mechanical cleaners. Avoid heat and dry conditions that could dehydrate and crack your opal. Treat it with care to prevent sharp blows and scratches. Avoid impacts. It is important to buy fine opal from a reputable retailer who will provide, in writing, all pertinent information regarding the gem including enhancements and special care notes.

BUYING OPAL

Opal is one of the most popular of all gems. In determining value, the brilliance and pattern of the play of color on an opal are very important. Generally speaking, opal with an abundance of red fire is the most highly prized. Those strong in blue and green are equally beautiful but not as rare, so they're priced less. Opal is not a common gem, although non-precious varieties abound. White opal, the most prevalent, may sell for a few dollars to several hundred per carat. On the other hand, fine black opal, which is the loveliest and rarest, therefore most expensive of the opal varieties, can command more than $1,000 per carat. The value of opal also lies in the size of the gem. Opal is very rare in large sizes, especially in black opal. Most opal is not faceted (except fire opal). It is usually cut into rounded or freeform cabochons that enhance color play.

Perfect natural gems--in color and appearance--are very rare and expensive. Many types of opal are treated to enhance their appearance. A common technique is to immerse white of gray opal in sugar solution and then in strong sulfuric acid. The acid carbonizes the sugar and leaves microscopic carbon specks in the opal that effectively blacken the body color and make the spots of fire stand out more. If an opal is enhanced in this way, avoid solvents and repolishing.

Some opals are also impregnated with colorless oil, wax and resin; colorless plastic and/or other hardened agents; or colorless synthetic resins and hardeners to hide crazing and/or improve durability. If an opal is enhanced in this way, avoid heat, solvents, chemicals and ultrasonic cleaners.

Natural opals are also found in composite or assembled stones called opal doublets or triplets. While they strongly resemble black opal, they are composed of a thin layer or two of white opal adhered to a poorer quality opal or other substance with black cement. It's an affordable way to get a big opal look. Doublets and triplets are usually sold by the stone rather than by weight and are cut to standard millimeter dimensions. Small gems sell for under $100.

Moreover, opals are synthesized and simulated in the lab. Pierre Gilson of France began synthesizing opal, the Gilson Created Opal, in 1974. Other companies, namely in Japan and Australia, are also creating opal. Opal is also imitated by a variety of other substances including plastics and glass.

OPAL HISTORY

The name opal was derived from the Sanskrit "Upala" and later the Greek derivative "Opallios," meaning to see a change of color. Opal is a gemstone that ranges from semi-transparent to opaque. Its body color covers a broad spectrum of colors, but is mostly prized for what is known as "play of color," the ability to reflect and refract light into flashes of multiple colors.

Historically, opal was considered a lucky charm that brought beauty, success and happiness to its wearer. Scandinavian women wore opals as hair ornaments to prevent their blonde locks from going gray. The Arabs thought that opal would ward off lighting and give a cloak of invisibility to its wearer when desired. It was supposed to grant vigor, aid the heart and kidneys and protect against fainting and infection.

Opals were also mined by eastern Europeans, the Aztecs of Central America, and ancient tribes in Central Africa. An opal was featured in the crown of the Holy Roman Emperor, and is still among the crown jewels of France. Napoleon gave Josephine an opal, and Queen Victoria was known to give them out as wedding presents. Opals are mentioned in the plays of Shakespeare and the novels of Sir Walter Scott.

Several opals are worthy of mention, including the 77-carat opal of Louis XVIII, kept in the National Museum of Natural History in Paris, and the 203-carat opal presented by the Australian government to Queen Elizabeth II of England in 1954.

In addition to its place as October's birthstone, opal is also a recommended gift for couples celebrating their 14th wedding anniversary.