Boulder Opal – Uniquely Queensland

Australian Boulder opal occurs only in Queensland Australia. Major opal fields in this area include Quilpie and Winton. As has been found as far north Middleton and as far south as Hungerford.

  • Australian Boulder opals are the second most valuable type of opal following black opal.
  • Boulder opals are easily distinguished by their layer of solid brown ironstone left on the back of the stone. Boulder opal is found filling cavities and cracks in ironstone concretions called boulders. Due to the general thinness (around 0.5mm to 2mm) of the opal, some of the ironstone is left on the back of the gems forming a stable durable base. Boulder opal is traditionally cut in “free form” shape.

Boulder opals, as the name suggests, are mined from large ironstone boulders under the ground. Thin veins of colourful opal forms in cracks and fissures in these boulders. Because these veins of colour are so thin, opal cutters need to leave the ironstone on the back of the opal to form a full sized stone. The thin layer of opal in boulder opals can display any colour of the spectrum.

Our mining efforts have concentrated around the old “Bulgroo” opal fields and in the vicinity of the “Highlands” opal fields.