Boulder Opal Matrix is mined mainly in Yowah or Koroit opal fields. This opal has inclusions on colour in natural formed ironstone that has reputation of stunning natural patterns n colours and normally has high polish Source your Boulder opalmatrix direct from opal miners and opal wholesalers and dealers for your single gem opal or parcel boulder matrix opals from Quilpie or Winton Australia Boulder opals are mostly shaped freeform and have colours formed on sandstone or ironstone backs so boulder opal is considered very stable.also found as pipe opal or matrix opal