One of the most fascinating types of opal out there is matrix opal. This is a type of opal which has typically seeped into and fused with more porous rock types. The exact process changes from rock type to rock type and region to region but generally speaking a sedimentary rock either has parts of the glue holding it together (known as matrix) replaced by silica over time, or the tiny pores within the rock itself fill up with silica. The result is the same- the silica is of course opal.
Andamooka and its opal
Andamooka matrix opal has an interesting history. The town, Andamooka is located in South Australia, near Coober Pedy. It is extremely remote. The town itself has a frontier quality to it. Nevertheless, it is one of the oldest mining towns in Australia. Originally when opal was discovered in this remote part of the world, miners were more interested in the crystal and boulder opal that was extracted. These opal types had obvious colour and was easily sold at a premium price. It didn't take long, however for miners to realise they could treat the "waste" matrix opal using common household chemicals.
Treating the opal
Matrix opal tends to be porous. This is important, as if the opal can soak up water, it can also soak up treatments. The most common treatment methods involve either smoking or a heat treatment using ordinary table sugar. The result is an originally light coloured rock which is now intensely dark, and this dark colour brings out the fire of the opal within.
The Andamooka opal con
Once miners realised heat treatments changed the colour and vibrancy of the opal,
it didn't take long for some of the less reputable miners to try to pass off this opal to foreigners as original Lightning Ridge opal. In reality, this opal is easy to identify so the "con" should not have been too effective. As they say there is a sucker born every minute....
The reputation plummets
As fantastic as it may seem, this "fake" opal was successfully marketed, but it did not take long for the deception to be revealed. In a market reaction not dissimilar to what we see in smoked Ethiopian opal in the present day, All treated opals became practically worthless overnight. There was no market in Andamooka matrix. Opal production dwindled.
The recovery
Over the last few years, the value of Andamooka opal has been rediscovered. The treatment recipes managed to survive. Most people use a treatment method that is at least 40 years old and is probably unchanged from colonial times. Many opal sellers specialise in "Mooka" (slang for Andamooka opal) and many YouTube influencers demonstrate the treatment technique to millions of adoring viewers. Andamooka is back and although affordable, is becoming more expensive every year.
Mining
Andamooka mining is still possible but claims have to comply with the requirements of the local indigenous people. For centuries, the local tribes were not considered at all and they have a right to feel aggrieved about the land and what was stolen. Meeting tighter and tighter requirements is drying up supply of this wonderful opal. there may be a time in the near future when it is not available at all.
Conclusion
Although Andamooka and its opal got off to a rocky (groan) start, This fine gem is making a massive comeback. Look on our site for some Andamooka matrix. I'm sure it won't stay there for long!