Item Information

Dimensions (mm) not provided
Weight (carats) 7 carats

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This is a parcel of opal that is in the sandstone found on the boulder opal fields in Queensland.It has been treated to appear like black opal by being carbonized.

The polish is excellent.


Weight of parcel 6.96 cts app

Size of largest 9.6 x 6.4 mm app


What is Sandstone Opal Matrix?
Naturaly formed sandstone opal matrix is Precious Opal flecks dispersed throughout an earthy orange ferruginous sandstone.
Why is sandstone opal matrix treated?
By enhancing the background matrix will give a greater contrast thus the visability of the precious opal colors is greater and stabilizing the sandstone also strengthens the stone by up to x10. Once enhanced some stones have the appearance of top gem quality black opal particularly ones with interesting and unique patterns. They are also similar in appearance to Honduran (basalt) matrix and gem Andamooka (concrete) matrix, even nicer.
How is sandstone opal matrix treated?
The treatment is done by cooking the stone in sugar, thus the sugar is carbonized giving the stone a darker or black background and it is stabilized with inert chemical that strengthens the opal by up to x10. Only the sandstone absorbs the treatmeant, not the precious opal. This type of treatment when applied correctly is absorbed all the way through the entire stone, so re-cutting is not a problem, you do not have to treat it again after cutting.
This stone is a more compacted sandstone type and the flecks of precious opal are more concentrated. It takes a polish/ finish much better than the very porous types. 


6d 22h 55m 32s

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Pricing & Details

Bid Increment $1.00
Starting Bid $28.00
Auction ID 253115
Watchers 2 watching
Viewed 371 times
Starts 26th Oct 2016 7:03pm PDT
Ends 2nd Nov 2016 7:00pm PDT

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