Opal is the most rare and valuable gemstone in the entire world. Every single opal is different and unique. You will never be able to find an opal that is exactly the same as another opal. They are found all over the world. All opal gemstones are considered gemstones, and not semi precious stones, because of its quality and rarity. Opals are usually opaque but can sometimes be translucent or even transparent. On Moh’s Scale, the opal’s hardness is 5.5 – 6.5. This is relatively soft, so opal is sometimes coated with a thin layer of clear quartz. This is to make the opal more resistant to scratches. These are called opal doublets or triplets. An imperfection of the opal is crazing. That is when the gemstone is damp and then dried too quickly or suddenly exposed to intense light, which forms internal cracks.
The chemical formula for opal is SiO2 + nH2O. Another name for common opal is potch. Some historical information about opals is that people used to think they were bad luck. This is a myth. In the early days, diamond companies were worried that opal companies were going to become more popular than them, so they spread some bad rumours around.
About 95% of the world’s opal comes from Australia. That’s why it is the national gemstone of the country. The countries that contain opal deposits are Australia, Honduras, Mexico, Brazil and Nevada in the US. Coober Pedy, Andamooka, White Cliffs, Lightning Ridge are major mines in Australia. Tablon mine is from Honduras, Iris mine is from Mexico, Pedro 2 and Boi Morto mine are from Brazil and Virgin Valley is from Nevada.
Opal is mined using the simplest method from the early days. It is one of the only minerals that could be mined by one person alone. It is mined using shaft sinking using a pick or a shovel. The shafts are sunk straight down until any promising opal dirt is found. Driving along the levels is then carried out, using picks or explosives. Handpicks or screwdrivers are used to delicately