Australian Boulder opal is mined over thousands of square kilometres in central Queensland Australia.
The major opal fields are Winton, Quilpie, Yowah, Koroit, Opalton with many opal mines hundreds of kilometres away from any regional town. So if you meet a opal miner and he invites you to his mine you are best to take provisions for 2 day drive! Some boulder is even mined closed to the Northern territory border.
Many opal cutters will specialise in one particular area as boulder opal is found in veins in bedrock and has to be split or sawn or chipped open to expose opal colours.
Most boulder opal is sedimentary so it is not cabochon but some colours and pattern are spectacular and opal splits make ideal earrings.
Lightning ridge opal need s water to clean the rough opal but boulder opal is found in more desert conditions and water is scarce even if even if artesian water trough is close by. so dry agitators are common to expose opal veins in the host bed rock and bulldozers work well in these hot dry dusty conditions.
Diesel fuel is expensive now and many opal miners spend thousands dollars each week on fuel so opal is getting more expensive to mine and harder to find large deposits of boulder opals.