Australia is located and also accounts for about 95% of all expensive opals in the world. The remaining 5% is more or less divided by about 19 state territories. In most of them expensive opals are only found and only in nine states their mining takes place. Australian expensive opals differ from precious opals found in the rest of the world mainly from their origins. While in the world, in all cases, the result of volcanic activity and hydrothermal processes, opal was formed in Australia mostly as a product of the weathering process.