What is Boulder Opal?
Boulder opal is term used to describe precious opal that occurs in 'veins' or 'pockets' in ironstone boulders. It is only found in one part of the world - Queensland, Australia.
Australian boulder opals come from the very heart of Australia - in a belt of Cretaceous sedimentary rock that covers an area 400,000 square kilometres, or about the size of California.
Finding these elusive ironstone boulders is no easy task. After all, we are hunting for something that formed millions of years ago. But it is worth it, as these unique ironstone boulders contain the world's most beautiful opals. And at Broken River Mining we treat each and every opal uniquely, just like a piece of art.
Our wood replacement and crystal opals are a special type of Australian opal that form in sandstone. They are found together with boulder opals at our Russells opal mine in Western Queensland, Australia. See below for the specifics of their formation.
Opal Fossils with Unpreserved Internal Details
Opal formation commences when silica dissolves in water. At our Russells opal mine we have found that this silica solution occupies a void most probably left by decaying tree roots or branches. When it solidifies it creates an opalized replica of the original object. These are also known as 'jelly mould' fossils.
In some rare cases we have found large and rare opal fossil specimens with beautifully preserved external features and pure crystal opal ‘branches' or 'roots’ within.
The smaller and more fragmented pieces yield thick "crystal opal" that we carve into transparent and translucent opal gemstones.
Opal Fossils with Preserved Internal Details
Opal formation commences when silica dissolves in water. At
our Russells opal mine we have found that this silica solution occupies a void most probably left by decaying tree roots or branches.
In cases where the silica infiltrates organic material before complete decomposition occurs, the organic molecules are replaced by silica. This remarkable process results in the meticulous preservation of
intricate internal structures. Consequently, the wood structure remains visible within the opal.
Our “wood replacement” opal is truly exquisite, not only because it is an opalised fossil, but because the remaining internal structures create a mesmerizing inner world that is visible through the transparent and translucent opal.