26.4 ct Yowah Boulder Opal cabochon

This extraordinary 26.4 ct Koroit black opal kernel represents a rare chapter of Australian opal history, displaying dominant blue and green play-of-color with full-spectrum flashes concentrated within a naturally formed, high-contrast kernel — a structure prized by elite cutters and collectors alike. Held for decades within the Andreou Family Heritage Collection, this stone originates from an era of Koroit mining that has long since passed, when exceptional material of this caliber was still being recovered. Today, opals of this quality and formation are no longer being mined, making this piece not only visually exceptional, but historically irreplaceable. Offered to the market for the first time, it stands as a one-of-a-kind opportunity to acquire a genuine legacy stone from Australia’s golden age of opal.