Koroit Boulder Opal Rough

Koroit boulder opal from Queensland, Australia is a precious opal that is found in seams in ironstone. The ironstone formed as concretions in sandstone matrix. The color patterns of the matrix combined with the gorgeous opal make beautiful stones from this material.

Some opal will be a thin layer on top of the ironstone. Keeping the ironstone as a backing is a common practice with this material. Other times, the opal is cut so that the opal shows as veins within the matrix.

For tips on cutting opal, see this article.

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