Making camp one night, a 14 year old boy found an opal. This started an 'opal rush' and soon the settlement of the Stuart Range Opal Field was founded, better known now as Coober Pedy and together with Lightning Ridge in NSW, the bulk of the world's opal continues to be produced. In Australia, precious opal is found in Cretaceous age sandstones and mudstones. These sedimentary rocks were deeply weathered and this weathering released silica into the groundwater. Small faults and joints in the rocks formed pathways for movement of the groundwater as it penetrated downwards.
Impermeable barriers between the sandstone and the underlying rocks trapped the silica-carrying groundwater where it slowly hardened into a gel forming opal in veins and lenses. Opals are frequently layered and if a rare red layer is present it is at the base in the thinnest portion of the vein and indicates that gravity played a part in the arrangement of the silica spheres.
Australia is the only part of the world where opalised animal and plant fossils have been found. At Lightning Ridge in NSW, small opalised dinosaurs and primitive early mammalian remains, together with shallow marine shellfish and crustaceans have been found. Probably the most famous opalised fossil is Eric the Pliosaur Cretaceous age marine vertebrate which was found at Coober Pedy and now forms part of the Australian Museum collection. Opal 'pineapple' pseudomorph after ikaite, R Spectacular mineral replacement with opal can also occur.
Queensland opal deposits occur in non-marine sedimentary rocks and opalised animal remains are very rare, however fossil wood fragments showing annual growth rings and cellular wood textures occur and sometimes these are beautifully replaced with precious opal. Opal in matrix from Queensland. Opalised bones of Eric the Pliosaur. Source: stellalapis. Today, Coober Pedy SA is the main producer of white opal, though in recent years this field has expanded and all types of opals are found.
Other centres in SA include Andamooka and Mintabe. When early settlers migrated west to pan for gold in early American boomtowns, they may have also encountered another treasure hidden in the earth: opals! The US supplies only a fraction compared to other sources like Australia, Ethiopia, Brazil, and Mexico, but the western canyons and valleys are lined with small opal mines.
Today, many mines are still active while others have long since closed, but their treasures still sell in the market. American opals come from several states in western USA, where volcanic rocks in remote mountains and valleys along the Western Trail from California to Washington supply varieties like black opal, fire opal, common opal, and more.
However, Nevada is the leading American supplier for opals. Most of these opals are found in western USA, with many opal mines open to the public. Can you find black opal in the US? You bet! In Northern Nevada nestled against the border of Oregon, a conglomeration of three high-producing Virgin Valley opal mines line the high desert valleys along the Sheldon National Wildlife Refuge, including:. The vast 68,acre valleys encompass the heart of the Old West and its rich prospecting history.
The region teems with common opal, but a few small deposits supply precious black opal, known as some of the finest opals in the world. Tourists can visit this opal mecca during the mining season, from May to November. These fragile stones cannot be cut or polished.
That said, they make for stunning display gems sold to museums and rock shops for collectors and home decor. Opals hide in rhyolite geode mineraloids that form in low-temperature silicon dioxide cracks in the earth. In addition to thundereggs, Oregon supplies a variety of fire opals as well as common opals, rainbow opals, centra luz opals, blue opals, and dendritic opals.
Where can you find opals in Oregon? Counties across the state have small opal mines. Any findings unearthed are yours to keep! Boulder opal comes from Queensland, Australia. The name of this comes from the way it has formed naturally in an ironstone rock boulder. The pictures below are taken from face and back side of the same stone. The picture on the right is the face and left picture is the back.
This type of opal typically presents as a thin layer of opal over a dark brown base when cut. Let's have a look at another picture. Rich in myths and legends, Queensland is the birthplace of the Australian Opal Industry. Opal was first discovered in Queensland on Listowel Downs, south of Blackall in The first registered mine was in south of the present town of Quilpie.
Among the early miners were Berkelman and Lambert, who worked a deposit on the Barcoo in , and whose opal attracted great interest at the Queensland Annexe of the London International Gem Exhibition in In so doing he engraved his name forever across the annals of history. It was due to his sheer determination in convincing the gem merchants of the world to accept the gem that we now have a viable industry.
Opal gougers of last century were mostly shearers and station-hands who had little or no geological knowledge. George Cragg, a young stockman, discovered the northern opal fields on Warronbool Downs kilometres south of Winton where the Opalton Field exists even to this day. Two World Wars and droughts slowed the progress of Boulder Opal realising its full potential on the world stage.
Although mining on a small scale continued it was relatively dormant. It was not until , when Des Burton , a pharmacist from Quilpie become involved with Boulder Opal, unwittingly through his efforts, helped revitalise an industry. Opal has been discovered in Queensland from the Southern Borders of Western Queensland to as far north as Kynuna, this probably would be the largest opal field ever known, with opal mining centres in Winton and Quilpie.
Today the Queensland opal miner still exists, supplying the markets of the world with this most exquisite product, Queensland Boulder Opal. A History of Opal Mining in Queensland The history of opal in Queensland is one of heartbreak, frustration, determination and at times success at incredible odds.
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