Incredibly rare! Millions of years ago a Fungus ate out channels into the wood. The so created cavities have then been filled in by the Opal gel. Over time the Opal gel hardened out to the opal we see today. That is what makes that kind of Opal pattern “Conk”. The Dozer Conk’s Sibling ( Brother) is one of those three wood opals conk that has been driven over with the Bulldozer, while preparing the bank in the Mine.