Larry and Blaine, Opalolism is an addictive disease much like alcohol.
When you are totally in the grasp of opal you will not be able to go
past an opal dealer without buying a jar or bag. It took one large
bad deal to cure me. Put out a couple of thousand dollars for an
ounce of gem grade opal and have it craze after cutting will put you
well on the way to a cure. The best explaination I heard for opal
crazing comes from a PHD in minerology from Australia. His
explanation was that all opal because of its water content is
internally stressed. As the internal stress is released the water
exits the stone. This leaves a crazed stone of no value. According
to him the process of stress release goes on in all opals. Some
slower than others. Some can take minutes, some days, some
centuries, but it occurs in all opals. The process is accelerated
once the opal is removed from the ground. Once removed the
atmospheric interactions, sunlight and chemicals, all speed up the
process. Also accrording to him the process cannot be stopped or
reversed. So if you own a beautiful opal, take care of it. Do not
wear it when you swim, do not put perfume on it, do not leave it
exposed to direct sunlight and heat. To this day nothing captivates
me more than opal, but I have been burned by the fickle nature of the
stone. I admire it, but keep my distance.
Gerry Galarneau
Help recently I was shown a very interesting type of opal,said to be
from MAdagascar, thus stone was black as coal and had very nice color
ranges, can any one tell me where to find a source for this stone and
what a normal price rage is? thank you Tom.
Gerry: Your explanation sounds about right. I read in an old LJ
article once that one might prevent crazing of susceptible opal rough
by “curing” it in a ziplock bag with a damp paper towel. By the time
the towel has dried out, both it and the opal should be dry and the
opal hopefully not crazed. I believe this came from an article on
Virgin Valley Opal (either there or some other location out West),
which is notorious for crazing.
HTH,
Roy
It is more likely Labradorite (a variety of Feldspar) which is coming
out of Madagascar by the ton! Judy Shaw
Hi Tom, I’m not familiar with any opal from Madagascar, but I wouldn’t
be too surprised. If it does exist, I don’t think it would be
considered a major locality.
Based on your description, what came to mind for me was Honduran
opal. I was able to find an example on eBay that has a good photo of a
cut stone and a pile of rough (at the bottom of the page):
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1618042969
In fact, it’s a “Dutch” auction of seven one-ounce parcels of
rough… I may have to bid! 
All the best,
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com
Hi, All-
A word to the wise on the black honduran opal-
The stuff I have seen is precious opal in a basalt matrix, and it’s
beautiful when it’s wet-- black, with all sorts of pretty sparkly.
Once it’s cabbed and polished, it tends to be more of an unaesthetic,
dirty grey, due to the porosity of the basalt. It would probably
improve greatly with an opticon treatment, or possibly with the kind
of sugar treating normally done to Andamooka matrix.
I’m not saying that you shouldn’t buy this stuff, but I would
recommend that you buy a small amount, cut it, and see how you like
the finished result before making a large purchase.
Lee Einer