Boulder opalRough is mined in Queensland Australia. It is formed as veins in ironstone. Ironstone is the deep brown potch like stone that is very strong. Most popular opal mining towns are Quilpie and Winton and many old fields like Jundah or Hammonds mine still produce opal. Boulder opal mining is capital expensive with large bulldozers and excavators..D9 bulldozers are common and some fields now have D12s as these dozers sometimes have to level off mountain tops to get to the opal and need large strong rippers to break open the ground. the miner will block out the rough opal and when he sees vein of opal colour he will hold against thin saw blade to place nick in the colour and the piece will break open evenly exposing opal colour, sometimes good colour sometimes very little colour Source your Boulder opal rough direct from opal miners and opal wholesalers and dealers for your single gem opal boulder rough or parcel rough boulder opals from Quilpie or Winton Australia