Opal is one of the world's most beautiful and rarest precious gemstones. Australian gemstones can easily be distinguished by their brilliance and play of colour. The Gerard McCabe Opalescence collection incorporates white opal from Coober Pedy in South Australia and black opal from Lightning Ridge in New South Wales. Here is everything you need to know about these glorious gems:
What is an Opal?
Opal is from the Greek Opallos meaning to "see a change of colour". Each Australian opal is unique and the different varieties offer a spectacular choice of colour, shape and size. When rotated, the opal displays a constantly changing interplay of fiery colours.
Opal is not only one of the world's most beautiful precious gemstones; it is also one of the world's rarest.
Technically, opal is a non-crystalline silica (in a rigid gel form) containing approximately 5% to 9% water. On the Mohs Scale of Hardness opal rates at around 5.5.to 6.5. As a comparison, diamonds rate at around 10, sapphires 9, quartz 7 and pearls 3-4.
How is opal formed?
About 65-140 million years ago during the Cretaceous period, central Australia was covered by a giant inland sea. As the inland sea retreated, silica-rich sands were deposited, onto what is now basically a desert area. Weather conditions changed the sand sediments released large quantities of soluble silica, creating a gel. This gel seeped into cracks and crevices in the ground and gradually hardened through nature's heating and moulding processes, resulting in the creation of opal.
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Where does the colour in opal come from?
Opal is composed of silica spheres that are packed together. In precious opal, the arrangement of the spheres is an orderly three-dimensional grid, because of the special pattern of spheres it is the only gemstone that has the unique natural ability to diffract light. light passing through the transparent spheres is scattered by the array of voids. White light is diffracted and split into various colours at different angles. The colour visible from the opal is dependent on the size of the spheres. Blue and violet colours are created by spheres that are smaller compared to the larger spheres and voids which create red and orange colours.
Where does opal come from?
96% of the world's precious opal comes from three isolated areas in the outback of Australia. A small amount of precious Opal is found in Brazil and Mexico. Australian stones can easily be distinguished by their brilliance and play of colour.
In Australia, Black Opal comes from Lightning Ridge in New South Wales, while Light or White Opal is mined principally from the South Australian fields of Mintabie, Coober Pedy and Andamooka. Boulder Opal hails from Central Queensland. The opal fields of Australia are in the harsh outback where only the hardened miner can make a living. In Coober Pedy, miners live in underground homes, dug into the barren ground, to escape the extraordinary heat and relentless dust.
The Gerard McCabe Opalescence Collection features both Cooper Pedy White Opal and Lightning Ridge Black Opal.
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What kind of Opal does Gerard McCabe sell?
Gerard McCabe sells solid opal in our Opalescence Collection. Solid opal can be cut into many shapes. Unlike diamonds and other precious gemstones, it is not cut into facets because this would spoil the play of colour with reflections. Usually, it is cut into softly curved cabochons and various freeform shapes.
Gerard McCabe's Opalescence Collection features black opal from Lightning Ridge in New South Wales. This is best described as opal with a dark or black background colour. The face of the stone predominantly radiates hues of red, blue, green and orange. Our collection also features White Opal from Coober Pedy in South Australia. This opal can be identified by a light body tone and a red, blue, green or orange play of colour.
Gerard McCabe also offers some opal jewellery in our Antique jewellery collection.
Discover the impressive Gerard McCabe Opalescence Collection at any of our South Australian Jewellery Boutiques: Rundle Mall, Adelaide Arcade and the South Australian Museum Shop on North Terrace.
