I had heard once ( and have no idea at all how true it is) that
opals could be stored in very small quantities of mineral oil for
long term storage. It was supposed to protect the stones as well as
retain or enhance the colors in the stones. I honestly do not know
the accuracy of this. It just seems that a certain degree of
climate control could be maintained in a small air-tight container
of some sort.
Michael, As I mentioned in a previous post, opal can, indeed, be
stored in an airtight container with liquid to help prevent or deter
thermal shock (or you can call it “a certain degree of climate
control”). The vast majority of opalholics do agree that opal can
“re-hydrate” most liquids and, since the diffraction of light in
opal is caused by the water between the stacked silica spheres
within, water is usually the liquid of choice. Most, but not all,
opalholics agree that mineral oil, or any oil can be absorbed into
an opal, possibly discoloring it. If you believe that opal can
re-hydrate, you must also believe it can soak up oils.
This begs the question: If opal can soak up mineral oil, then why do
they recommend I wear it daily to prevent crazing by wicking out my
body’s natural oils? I can’t answer that one, but it does beg
another question from me: If you bought opal jewelry, why on earth
wouldn’t you want to wear it? That’s the opalholic in me talking 
My second question here is, what about all the other types of
jewely out there that do not use opals? How would the air
conditioning systems affect them if at all?
Good question. Opal is pretty much the only gemstone that can be
severely affected by dehydration, but thermal shock can affect quite
a few. Fortunately, it takes a fairly extreme temperature change to
make a difference. Also, opal dehydration can take a long time, and
that varies from piece to piece. It could take weeks or years.
Since all emeralds are oiled before they leave the mines, a lot of
people store them in some type of oil. I believe the most common
emerald oil treatment consists of Canada balsam (occasionally dyed,
as well), but there may be newer techniques. Air conditioning, safe
deposit boxes, etc. won’t have much of an effect on most jewelry.
However, there are lots of period pieces with such stones as
foilbacks that can suffer from humidity changes. If anyone has
valuable gems or jewelry of any kind, they should always insure them
for this purpose, and other obvious ones.
As I said, I am very ignorant on these subjects (especially
about opals and other stones) because I use primarily metals only
at this stage of my learning experience. Inquiring braincells are
thirsting for knowledge here.
If you’d like to learn a lot about opals, look into Paul B.
Downing’s books Opal Identification and Value, and Opal Adventures.
Fred Ward also has a good one, I believed titled simply Opal by Fred
Ward. The archives will list them, I’m sure. These will give you a
great start. One of the many web sites that specialize in gemology,
www.yourgemologist.com has a tremendous amount of about
most common And, you can always ask here.
James in SoFl