The most valuable and popular of all opals is Black opal. Black opal accounts for around 5% and is found at Lightning Ridge in Northern NSW. It is called Black opal because it has a black base caused by black or grey iron oxide impurities in the opal. The color bar or the ‘play of color’ of Black opal comes in all the colours of a rainbow with red being the rarest and most expensive. A Black opal is Crystal opal with iron oxide in the back. It can be grey through to very black.
This black potch or common opal has no value unless we find a color bar on top of it. It’s all about the evidence we get when we cut rough opal, we find a little piece of color on the side and we take off the top layer of potch (common opal) and we hope the opal faces up. Then we take off the skin of the stone and we hope we get a face with nice color. Often it looks very nice on the side but not on the face, that is the risk we take in cutting black opal. The yield when we cut black or Boulder opal is 5% that means we lose 95% of the opal, it is very risky to buy rough black opal and cut it.