A recent discovery in 2007 of the beautiful Pipe Opal has created great joy for opal miners and a big frenzy with opal buyers. Displaying an amazing array of colors and patterns, everyone is wanting to know more about this newly unearthed stone.
Boulder Pipe Crystal Opal is found in the Central Queensland opal fields in Australia. As the name suggests it is opal formed in a pipe or tubular formation. These roundish tubes are formed in host rock, which is mostly sandstone. The sand stone potch enhances the natural fire color in this crystal opals. Most pipe opal is green to blue fire colours but some have sunset bright fire opal colors but this is rare. The tubular pipe opal can be hollow or tubular.
At the start of the century Australia had pipe opal production. New fields were not found till 2007 and only recently deposits have been mined in 2018. Mining for pipe opal has not been regular with small pockets of pipe opal being discovered. It can be several years or decades before more pipe opal is found in large quantities.
In the past many people have purchased a crystal opal that had the potch removed and have no idea that the opal was actually a pipe opal.
Today opal cutters prefer to leave the natural potch on the opal intact. This does make the crystal generally brighter and creates more unique organic shapes. Be careful not to confuse belemnite opals with pipe opal. Belemnite opal is also tubular and solid or hollow like pipe opal but it is a fossil from South Australian opal fields.
The famous tubular shape Virgin Rainbow is also not a belemnite but formed under the pocket left by a dead belemnite. Pipe opal from the Queensland boulder fields is not a fossil.
The sandstone can vary greatly in color and density. Creamy colored sandstone displays softer opal colours and sandstone can be tan to deep chocolate colour and this can help enhance the crystal opal.
The theory is that water or silica flows into tubular crevices, but why the crevices are tubular shape and only in small areas is still a mystery. The water also must be pressurized to drive the ultra-filtration process. Similar to a fast-flowing creek after heavy downpour of rain. The water also needs to be alkaline with high silica content. This might help explain why only small local areas produce pipe opal. Another concept is that chemical elements were in the alkaline water and this reaction helped carve out tubular veins where the silica formed. Mother nature created these beautiful pipe opals in small localized areas so it is difficult to find large deposits of this opal.
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