Okay, you’ve purchased a lot of black opal rough… now what do you do with it?
Watch this video to find out.
January 18, 2010
December 10, 2009
Boulder and sandstone opal pt 1
Sandstone and boulder opal have been mined in Queensland, Australia since 1872.
Sandstone opal, which is also found in Mintabie and Andamooka, forms opal that is unattached, whereas boulder opal is formed attached to ironstone.
Australian gem associations define boulder opal in this way:
“Boulder opal is presented in one piece, where the opal is naturally attached to the host rock in which it was formed and the host rock is of a different chemical composition composition.”
The earliest miners would cut or break the opal away from the ironstone, and would then sell it as Queensland Opal. If the opal broke when it was being separated, it would simply be thrown away.
It was not until the 1970s that boulder opal found a market. Today, the best pieces of boulder opal can fetch as much high prices as even black opal.
November 13, 2009
Coober Pedy Opal Rough on auction today
There’s never a dearth of coober pedy opal rough at www.opalauctions.com. Here’s a sample of what’s available. To see it all, follow the link above.
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PETERS ROUGH OPAL DEAL2.97 CTS [MN5] PETERS OPAL |
135.00 | - | - | 2 days 6 hours |
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PETERS ROUGH OPAL DEAL 22.30 CTS [MN40] PETERS OPAL |
45.00 | - | - | 2 days 6 hours |
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PETERS ROUGH PARCEL MINED IN THE 90S. 19.84 CTS [SP 312 ] PETERS OPAL |
89.00 | - | 19.84 | 2 days 6 hours |
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WHITE OPAL ROUGH 3.50 CTS FJL 2889 (LO) LIGHTNINGOPALS INC |
10.00 | - | - | 2 days 8 hours |
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PETERS CHUNKY ROUGH OPAL DEAL 19CTS [SP637] PETERS OPAL |
16.00 | - | - | 2 days 8 hours |
October 21, 2009
Introduction to Boulder Opal
View boulder opal rough available at http://www.opalauctions.com/auctions/rough-opal/boulder-opal-rough/
Boulder opal, which occurs in deposits in weathered sedimentary Cretaceous rocks in the west of the state of Queensland, is unique. For one thing – it is found only in Queensland!
Boulder opals are the second most valuable type of opal (after black opal).
Boulder opals are easily distinguished, because they have a layer of solid brown ironstone on the back of the stone. Boulder opals are mined from large underground ironstone boulders. Thin veins of colourful opal forms in cracks and fissures in these boulders. Because these veins of colour are so thin, it is necessary to leave the ironstone on the back of the opal to form a full sized stone. The thin layer of opal in boulder opals can display any colour of the spectrum in a beautiful play of colour.
Concretions up to 5 cm across, known as ‘nuts’, may host a kernel of solid opal or contain a network of thin veins of opal through the ironstone. This variety of opal is prevalent at Yowah where the concretions form distinct bands—these are called ‘Yowah-nuts’.
The major opal mines are:
–Winton
–Quilpie
–Yowah
–Koroit
–Jundah
Boulder opal rough needs experienced cutters to work the veins. The veins are tricky to follow. Many cutters use saws to cut and split the boulder rough — the rainbow colours can be spectacular.
When a miner has cut a piece of boulder rough and sees a good vein of colour, he will put a nick along this vein colour with his saw blade and the rock will split open revealing the opal colours. This is termed “a split.”