Here is a beautiful Koroit boulder opal cab from my mine in Koroit, Queensland, Australia. Yes, it is completely natural. I found it, cut it and polished it.
This type of boulder opal is quite unusual. It is a type of opalized wood, however opalized wood showing such a clean and vibrant "zip" of bright color does not happen very often.
Approximate mass: 8.21 carats
Approximate dimensions: 25.0mm x 12.7mm x 4.2mm
More photos are available on request.
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