About Opals and Fire Opals

About fire and other types of opals: How they evolved and where they are found.

Opals are one of the most attractive gemstones. Not because of their often colorful appearance per say, but mainly because of the tiny spheres made of silica that certain types of opals possess (In particular fire opals) which refract light. When one such opal is turned in light, an illusion of fire and flame are created. It’s little wonder that the Mayan and Aztec civilization associated this gemstones appearance with sensual pleasures and named it bird of paradise stone.

How are opals formed? Opals are formed in volcanic zones, especially where one finds hot springs. After a volcanic eruption hot solutions containing silica and water dissolved and took the place of calcite in rocks. This became colloidal silica and formed opals. The skeletons of tiny organisms were also filled. This became known as diatomite earth and is found in California.

Stunning fire opal and silver ring

What are the different types of opals? The dominant colors of fire opals can be from reds to yellows to vivid oranges. The principle fire opal producing country is Mexico. Dark reds and oranges are referred to as cherry opals. The best quality black opals are the most prized and therefore the most valuable. Australia is the world’s top producer of black opals, and they are also the Australian national gemstone. Also from Queensland, Australia we get a variety known as boulder opals. They are distinguished by their dark colors and marble effect sometimes referred to as “church window”.

White opals are desirable, but only those which feature a refractive presence of variable color. Hyalite opal is colorless and opaque. Wood opal is formed when silica forms in wood. Plain or common opals come in an attractive variety of colors from pinks to greens, and are often used in jewelry. But they have little monetary value. A few years ago a new type of opal was discovered in Tanzania called prase-opal. Its dominant color is green which comes from the chemical element nickel. Fire opals have also recently been discovered in the Ukraine and Kazakhstan. Although it is said they cannot compete with the best quality Mexican fire opals.

Common opal

Where can I prospect for opals in North America? Whilst various types of fine opals are mined in many parts of the world, the USA is no exception. Wyoming, Colorado, Oregon, Washington and Georgia are opal producing states. Wyoming is one of two places in the world where wood opals can be found. The other is Sardinia in Italy. However Americas best quality opals are found in northwest Nevada. There are two opal mines open to the public in Nevada. The Bonanza Opal mine is located in the Virgin Valley, and is open through the summer season. Rainbow Ridge Opal Mine is also in the Virgin Valley, near the town of Denio. See links for details.