Black Opal needs to have the natural black tone under the play-of-colour. It can go from a very black tone to a dark grey (an still be considered a black opal). Black opal on average is the most valuable of all opals but just because it is black does make it valuable it still needs to be bright and colourful - Put simply, if there's no Wow! Then there's no real value.
The Opal Museum is a private museum funded by the sales of loose opals and opal jewellery so for this reason we do not catalogue the loose stones on this website.