Joined: Thu May 20, 2010 2:21 am Posts: 32 Location: Chicago, Illinois
hello all,
I was wondering what your collective experience is with respect to Peruvian opal stability. I am interested in the advantages and pitfalls of both the blue ('chrysopal') and pink varieties. I am often offered this material in Peru, but I do not want to invest in some pricey rough only to find that it has started to craze after being out of water for a year.
Joined: Mon Oct 06, 2008 6:13 pm Posts: 5077 Location: Australia
hmm, well I've had some pink for a couple of years, neither the rough or cut stone has shown any crazing. It was from a high end quality seller but I honestly can't tell you more than that. I haven't really looked into the makeup of this stone but it's not what I'd immediately recognise as an opal. The blue is pretty and it looks very similar to some gorgeous translucent aqua Aussie chrysoprase I have. I think the Peruvian is more along these lines, chalcedony, than opal. Must look into it but will be good to hear others comments. Also, I don't know why this would be stored in water.
I am not a gem person, just an overly curious consumer, but I have a pretty blue ring I purchased a couple of years ago from **gasp** a tv/web seller. It is as beautiful as it was 2 years ago though I haven't risked louping it to see how much I probably scratched it. The blue blends very well with the Larimar bracelet I purchased at a gem show recently. I hope that is remotely useful.
Joined: Mon Oct 06, 2008 6:13 pm Posts: 5077 Location: Australia
hmmm Barbra...anyone? Now this quote came from an opal group
Quote:
basic composition is more in the quartz family of gemstones
in reference to the blue. Now my eyes are hanging out and this just isn't computing. Can you direct me to a really good info source on this one please.
Joined: Thu May 20, 2010 2:21 am Posts: 32 Location: Chicago, Illinois
My understanding is that the blue color is a result of chrysocolla impurities within the opal. Essentially the same thing as 'gem silica', except that it is suspended in opal (SiO2 + H2O) rather than chalcedony (SiO2).
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
NuevoMundo wrote:
My understanding is that the blue color is a result of chrysocolla impurities within the opal. Essentially the same thing as 'gem silica', except that it is suspended in opal (SiO2 + H2O) rather than chalcedony (SiO2).
That's basically it, except that both the chrysocolla and the blue opal are colored by copper. Both blue opal and "gem silica" occur in this same Peruvian deposit. I have both in my cutting stock. I'm limited for time today so can't look up info I have archived that shows the relationship of opal to the rest of the quartz family. I'll try to remember to post a link later.
I've cut a lot of the Peruvian blue opal and find it to be very stable. It tends to have black dendrites which can often be used to good advantage in designing cabs, like this bead from a dealer's site. There is much that's pure blue and blue-green. It's pretty stuff and tends to be less opaque than Peruvian pink.
Attachments:
Peruvian Blue Opal.jpg [ 18.79 KiB | Viewed 2818 times ]
I have some pink peruvian opal I bought around the time we had the contest for arcticles for the Project. Somebody do the math, anyway it is still not cracking so I'm planning on cuttine it when the eye heals up
hope this helps wolf
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Joined: Fri Oct 12, 2007 10:22 pm Posts: 1117 Location: Virginia
I have a pair of blue opal cab earrings cut by Ben Kho. I have had them 3 years. He uses Peruvian Blue Opal frequently, so I guess he thinks it's stable.
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Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
mehoose wrote:
Thanks ROM would be good to see the info. Hey, you trying to start a new frenzy with opal, 'Copper' bearing! move over Tourmaline.
Yeah, I've been a great fan of copper-bearing gems for years: turquoise, gem silica chrysocolla, malachite and azurite. But tourmaline is the only one I know of that's transparent. Blue opal is translucent at best.
Opal evolves from a silica gel. The theory is that the silica in your Oz opal deposits comes from groundwater leaching of near-surface soils and the gel is captured in cracks and subsurface openings. Whether it becomes "precious" opal or potch depends on how the little spherule lattices inside arrange themselves. Other opal concentrations elsewhere come from the same process as well as hydrothermal activity.
The article I had in mind is mostly about agate formation but opal is one part of the sequence. More research on opal is being done in Oz than anywhere else, I think. Here's the link: http://www.rps.psu.edu/0109/form.html
I would like to revive this thread. For those who had those opals....so after 7 years, how are they?
I find this material beautiful and not much around now but I still get conflicting feedback on the aqua blues. At the HK show last year, a seller with the "Paraiba" blue opals are soaking them in water. I think they cannot stand long under display lights or anything with constant heat or they will craze but should be fine in daily wear or stored in a gem jar?
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