The Opal - Aussie Extraordinaire
Posted by Ron Hansen on September 16, 2016
Opal is one of the most beautiful gems on the planet renown for its unique and varied color composition. Over 95% of all opals in the world come from Australia. Cooper Pedy, a town in South Australia and major source of opals, produced the world's largest opal back in the 1950's. Called the "Olympic Australis" this magnificent gem tilts the scales at 17,000 carrats! Because of the opal's proliferation in the Land Down Under, the Australians have appropriately named it their national gemstone.
A form of silica, the opal is classified as a mineraloid that has no specific form or crystalline structure, and it is well known for its multiplicity of color. The colors are formed by water trapped within the stone with tiny particles of silica dissolved in it, which causes light diffraction and creates a rainbow.effect. Multiple colors appear to intermittently move across an opal against a background color, depending on the angle from which it is seen. This phenomenon is called "play of color" and only occurs in a precious opal, as opposed to a common opal (also called "potch") in which it doesn't. Several colors can appear in opal including red, yellow, green, aqua, pink, blue, and brown. Orange, black and violet can also be found in opal but these colors are quite rare. Color impacts an opal's value in three ways - color intensity, transparency level, and play of color. As for luster, opal tends to have a waxy or somewhat gelatinous luster.
Opals occur in dozens of varieties, with their names often concocted by dealers - boulder opal, fire opal, cherry opal, jelly opal, flash opal, and many more. Compared to other gems, opal is relatively soft, with a 5.5 to 6.5 ranking on the Mohs scale, 10 being the hardest as with a diamond. It can be cut into many shapes, including ovals, marquises, rounds and hearts. And above all, the opal is found in just about any type of jewelry piece.
A great deal of folklore surrounds the opal, which ranges from possessing healing powers to being a harbinger of good fortune. Some suggest that the opal had its origin from the wife of Saturn in Greek mythology. Others believe that the opal stimulates creative powers. The opal is also recognized as the birthstone of October.
First century Roman author, Pliny the Elder, wrote that the opal consisted of “the glories of the most precious gems” with all of their beautiful attributes “shining together in an incredible union.”