This precious material is found in the old inland sea areas of Western Queensland, Australia.
It is believed that formation began 65 – 145 million years ago.
Boulder Opal occurs in veins and cracks in ironstone boulders and inseparable from the host rock.
Silicate rich waters seeping into the ironstone cavities over millions of years gradually hardened into opal.
This Boulder Opal measures 4 cm in length x 2.5 cm at its widest.