Boulder opal forms when a silica solution percolates through the ground and pools in empty cavities eventually turning into opal.
Boulder Opal can come in some incredible patterns with bright vibrant colours (we call this gem boulder opal). It is the most stable of all opals and it's not possible to make synthetic Boulder Opal. The challenge is, that because is varies so much it is more challenging to work out value unless you have a lot of experience and knowledge of the supply v’s demand ratio.
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.