Boulder Opal

Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix. It is found sporadically in western Queensland, from Kynuna in the north, to Yowah and Koroit in the south. The largest quantities are found around Jundah and Quilpie in South West Queensland.

The layers of opal formed on this ironstone backing are usually very thin, and as a consequence, the ironstone is often intermingled with the opal when cut and polished.  This type of opal is referred to as a matrix opal.  Because of the rich brown of the ironstone, these opals display vivid and bright colours.

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