In the desert of theSouth Australiaabout 850 km from Adelaide, the mining town arises with the world’s largest opal producera very rare and sought-after gemstone. It is Coober Pedyan isolated group of a few buildings, surrounded by an almost Martian landscape dominated by the red color of the terrain. Behind its desolate appearance, in reality, there is much more: the Most of the population lives underground. Let’s find out why and how we survive under the desert.
The Origin of Coober Pedy
Where Coober Pedy now stands, in 1915 two gold prospectors discovered a large amount of noble opalthe most sought-after variety, at relatively shallow depths. They decided to continue excavating, but there was a problem: they were very far from major centers and in the desert there was no water and the temperatures were prohibitive (they could exceed 40 °C during the day and drop below 0 °C at night). As for the water, they remedied it with a large tank that was filled once a week. The problem of the temperatures, however, was solved digging the houses underground, along the sides of the sandstone hills so as to have the entrance at road level. Initially, many veterans of the First World War settled there. Then, in the 1950s, the discovery of a rich vein of opal gave a further boost to the mining activity and many miners from all over the world moved to Coober Pedy in search of fortune.
Living under the Australian desert
Today Coober Pedy has about 3500 inhabitants belonging to 45 different nations, most of whom live underground. It is difficult to imagine that an underground dwelling could be comfortable. Yet in this case it is real apartments equipped with everything necessary. The water tank has been replaced with an underground source, electricity is available, you can watch television and even surf the Internet. To prevent dust from forming, the sandstone walls are covered with stucco. The temperature in the apartments is constant and mild, and to circulate the air, vents communicating with the outside have been created.
But there is more: in the underground social life is very active and takes place between bar, restaurants, swimming pools And churcheswhere regular religious functions are held. There is also no shortage of shops, art galleries And hotels for tourists: the tourism It has become an increasingly important source of income, especially in recent years, as the most productive opal mines have begun to run out.
Many of these rooms were created from abandoned mines and are connected to each other by a network of tunnels.
Opal mining in Coober Pedy
Most of the people of Coober Pedy work in the mines, where opal is mined between 20 and 30 m deep. Its formation occurred between 50 and 20 million years ago thanks to two factors: the presence of Silica-rich rocks and a climate in which rainy periods alternate with dry periods. Rainwater seeping into the rocks underground has become enriched with silica and has filled voids and fractures in the ground. When the underground water evaporated during dry periods, the silica in solution has deposited, forming opal. This process is very slow: it takes about 5 million years to deposit a thickness of opal equal to one centimeter.
In the past, opal was mined by digging pits with a shovel and pickaxe, while today augers are used. There are hundreds of pits and, together with the piles of waste rock, they dot the surroundings of Coober Pedy like craters. Once mined, the rough opal is separated from the sandstone in which it is found and cleaned of dust. It will then be cut, polished and worked depending on the use that is to be made of it.
Why Opal is Precious
Opal is a mineral that contains silica and water. It is amorphousthat is, its atoms do not form an ordered structure with well-defined crystals like, for example, those of quartz. The tiny spherical silica particles which are inside it, however, can be arranged “in packages”, like oranges in boxes. When this happens, the opal is called “noble” and is particularly precious. Its silica spheres, thanks to their orderly arrangement, are able to break down white light into all its colorscreating a “rainbow effect”.
THE‘noble opal It is not easily found in nature: the deposits from which this precious stone is extracted are located mainly in Australia, Ethiopia, Brazil and Mexico. TheAustraliain particular, provides the 90% of world production of noble opal.
