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Boulder Opals
Boulder opal is only found in the opal fields of
Queensland, Australia. Boulder opal is formed in cracks and fissures in the host
rock (usually ironstone). Varieties of boulder opal are defined by body tone,
"play of colour" and transparency. They include black, dark and light
variations. Boulder opal is usually cut leaving some of the
ironstone as a natural backing. Sometimes a seam can be split to give you two
matching boulder opals. Mining boulder opal is hard work, requiring the use
of heavy machinery and is very expensive. One of the main reasons being
that boulder opal is not found in high concentrations. Generally a lot of dirt
has to be moved to find just a small amount of boulder opal. Once the opal is
mined the ground must be restored to allow for
regeneration.
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