10.17ct Opal Australian Boulder Matrix In Sterling Silver Forged Wrap Total Weight. Boulder Opal consists of concretions and fracture fillings in a dark ironstone matrix. Boulder Opal is typically found in Western Queensland, Australia. This pendant is triangle shaped and has seams of bright flashy opal. This is a very nice small pendant. Total size of this pendant is 19 x 13 x 4 mm. Shipped Free with USPS First Class Package.