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Dirty opal


Hello, we had a real mess in our basement this week, a sewage back
up. In cleaning up I find that my rough stock of Spencer opal has
been slightly dampened. The cardboard box and the rock it contained
were wet on the bottom. Now, this rock has not been trimmed yet, and
some of the pieces are about the size of cantaloupes (with small
pieces of opal). I need a good process to sterilize the rocks and
leave the opals intact. Somewhere in the back of my mind a little
voice says that a 1/10 solution of bleach may cloud opals. ?? What
about hydrogen peroxide or alcohol?

All answers greatly appreciated.
Sincerely yours, Rose Alene McArthur


I would think just taking them out in the back lyard and hosing them
down with fresh water would do the trick. Jerry in Kodiak


Dear Rose,

Yuck, what a problem. I think that I’ve read that alcohol won’t harm
opals but that is half remembered info. They can also be soaked in
acetone or Attack to remove glue; I can’t imagine anything living in
either of these liquids. My usual ring is a nice Lightening Ridge
black. I have used antibacterial soap several times while wearing it
with no ill effects. My advice would be to try a small piece and
soak it in this for enough time to murder all of those nasty germs.

Best of Luck,

   Somewhere in the back of my mind a little voice says that a 1/10
solution of bleach may cloud opals. ?? What about hydrogen peroxide
or alcohol? 

Don’t listen to that voice. Bleach will be just fine. So would
hydrogen peroxide or alcohol, if you prefer. But I’d guess the bleach
is cheapest, easiest, and most effective. Do remember that though
opal is pretty special stuff, it’s still just silica. and it’s
waterproof, despite having water content. Spencer opal may be
somewhat prone to dehydration, but that doesn’t mean you can’t soak it
in a mild bleach solution. Won’t hurt it at all. neither would some
detergent or whatever else you need to clean it up.

Peter Rowe


Opal gets its color from the micros-structure of the material. Small
spheres of silica, usually less than the width of the wavelength of
light, interfere with the incoming photons and disrupt them… This
changes the wavelength of the light and you we see this as color
change. These spheres are packed with great regularity, like ping pong
balls on a tea tray.

There’s usually some water included in the material and some opals
are hygroscopic (water hungry. I’ve seen opals that will stick to your

If these opals get into contact with water that’s got small particles
in it they will absorb water and dirt.

Most bacteria are far too large to enter the pores of the material.

Hydrogen peroxide, however, will enter the opal and then break down
into oxygen and water. The highly reactive oxygen will bind with
anything that’s around to form a white oxide (usually white). This
accounts for the milkiness.

I’d suggest that your opals are probably already contaminated with
bacteria (ever tried going to the loo down a opal mine?) and that a
good wash in clean water with a little mild antibacterial cleaner
(mouthwash) for no longer than a few minutes will clean the surface
and allow you to feel safe about cutting.


Hello Rose Alene, I can’t address the question of whether or not the
disinfecting chamical (all you mentioned will disinfect with 60
second exposure) will damage the opal rough, but I can offer an
alternative, effective disinfection. If the box containing the rough
was wet, that means the solids in the sewage didn’t actually wash
into and around the rough. The stones are probably not contaminated
to any extent of concern, but here’s my suggestion to be on the safe
side. Sunlight is an excellent disinfectant (a band in the UV light
range does the killing) and I would suggest that you scrub off the
rock with disinfecting liquid soap - scrub with a brush if you can -
rinse, and put into the sunlight to dry. Turn as it dries so that
all the surfaces are exposed to the sunlight. Several minutes per
side of exposure should do it. Wear sun screen to protect yourself
;-}. Judy in Kansas where the wheat harvest is in full swing


Hi, The easiest way to disinfect your opal is to soak it in 10% bleach
water. This will not hurt the opal. Many dealers at gem shows use
bleach to keep the water clear. Thanks,


The gem book I have says to avoid solvents , never ultrasonic or
steam, use warm soapy water to clean…It’s not much but maybe
it will help…Char

Ms. Charolette’s Gold & Gem Specialties LLC
Rob & Charolette Purviance Jr.
4024 Davis Rd.
Guthrie, OK. 73044