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By Paul Holewa
Opals are the birthstone of October, making this the perfect month for Scheherazade Jewelers’ Rare Opals of Australia Trunk Show from October 11 to 12. We’re celebrating this month’s birthstone by bringing in an assortment of rare opals mainly from Australia, which produces 97% of the world’s opals.
Millions of years ago, the Great Artesian Basin of Australia was filled with the Eromanga Sea. This shallow, cold, muddy, stagnant body of water at its peak flooded 60% of Australia. The formation of Australian opal was due to the acidic oxidative weathering that occurred during the drying out of the country’s central landscape that followed the retreat of the Eromanga Sea from the basin starting about 100 million years ago. Such an occurrence over a large region is quite unusual explaining why a majority of the world’s opal supply is found in Australia.
Opals from Other Places
The state of Querétaro in Mexico is a well-known source for Fire Opal. Opals are also found in Brazil, and the Honduras. Ethiopia has been a key source for opals in the last three to five years.
What is Opal?
In scientific and plain terms, an opal is a mix of silica and water. Opal is known for and valued on its play of color. This results from the microstructure of opal. The bright rainbow colors of opal, as they appear to the human eye, will move and change depending on the angle at which the stone is viewed.
How is an Opal Valued?
The phenomenon known as the “play-of-color” is the brilliant range of the full spectrum of colors caused by the diffraction of white light by the internal structure of orderly arrayed spheres of silica. Body tone refers to the background or the underlying color of the opal, which ranges from black through dark to light. Brilliance refers to the brightness and clarity of the colors displayed by opal, when the stone is viewed face-up. This ranges from brilliant, bright , to subdued or dull. Patterns are another value factor for opals. The most desired patterns include Harlequin, Flagstone, Ribbon, Straw, Chinese Writing, and Picture stones.
An Opal Fun Fact
In 2008 NASA announced it had found opal deposits on Mars.
Legend and Lore
Throughout most of history, opal has been regarded as the luckiest and most magical of all gems because it can show all colors. In medieval times, young maidens thought opals had the power to preserve the life and color of blond hair.