All our natural solid boulder opals go through multiple quality checks over time before being released for sale. Any boulder opals that do not pass these quality control checks because of natural inclusions or faults are classed as our SECONDS. Opal seconds should always be declared as such, prior to purchase, and are always valued at much lower prices. Please note that we do NOT sell cracked or crazed stones, as they are virtually worthless. Normally we only sell our boulder opal seconds at trade shows, but for a limited time only we have made them available here for you! They are exclusive to our website.
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.