I was sorting through my jewellery and I came across my Opal necklace that I actually forgot I had! So I thought I would share a few facts I have learnt over the past on Australian opal.
Australia is the source of the world's finest opal specimens. The discover of this gemstone in the 19th Century triggered waves of migration just like those of the American Gold Rush.
At the end of the Cretaceous period and the beginning of the Tertiary era, the area of the planet occupied by Australia experienced sudden climate change. A mild maritime environment gave way to another, much drier one leading to the creation of a great dessert. Later, during the Miocene period a slow process of erosion took place (you can read more on the geological history of Australia in one of my previous blogs).
These events gave rise to the formation of opal, a semiprecious stone that is a combination of water and silica. Over time, nodules of opal built up in veins; fractures, and discontinuities of Australia's sandstone. There it remained until its discovery by British settlers and prospectors.
Opal has been mined in Australia for more than a century and a half. The first miners that arrived in the Australian dessert immediately realised it was going to be impossible for them to live and work in 50degree Celsius temperatures. So instead, they tunnelled underground where it was cooler, both to extract the gemstones and also build their homes and live. Even today, these 'troglodyte' dwellings are still inhabited.
The first commercial opal field in Australia was White Cliffs in New South Wales. As yields from this deposit declined, propectors began exploring other parts of Australia with similar geological characteristics. In 1915, the Coober Pedy deposit was found and quickly became renowned as a new, darker kind of opal named black opal. It was unearthed in shades of red, blue and vivid green. Even today, Coober Pedy is one of the most important opal-producing deposits in the world.
More info on Coober Pedy here:
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