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Opal care


#1

You have all been so great in helping this hobbyist with past
questions! Here’s one more…

I purchased the most amazing opal. The dealer called it Nevada opal,
and it’s full of brilliant greens, reds and blues. It also has many
black veins throughout the stone (petrified wood?). I’m about to set
it, but wonder if there is a way to protect it afterwards. Someone
suggested placing it in a plastic bag with a wet tissue to maintain
a high humidity level.

Any other thoughts on its care?


#2
        I purchased the most amazing opal. The dealer called it
Nevada opal,... Someone suggested placing it in a plastic bag with
a wet tissue to maintain a high humidity level. Any other thoughts
on its care? 

Karen, Most, not all, Nevada opal is unstable. If you have to take
extraordinary measures to care for it, it is not suitable for jewelry
use. Leave the stone out of water for a time to see if crazing will
be a problem. Keep a very close eye on it. If you see any cracks form,
place it back in the water and consider it “specimen only”. Cracks
can take weeks to form, sometimes only hours in a very dry climate.
It is said that you can “cure” opal by keeping it semi-moist and
allowing it to dry very slowly over a long period of time. (months)
But this is risky practice as it could go to any climate once it
leaves your hands and could still craze down the road. I hope your
piece is stable - as Nevada (and Oregon) opal can be some of the
best!

Mark Thomas Ruby
SunSpirit Designs
Loveland, CO
970 669-7075


#3

This “Nevada opal” is, indeed, beautiful. But unfortunately it is
very “cracky”. (If it is allowed to dry out it will crack.) It’s
just the nature of this opal. Your best bet will be to keep it in
water, and enjoy its beauty. Don’t try to set it. and yes, as I
understand it, it is opalized wood.

Margaret
@Margaret_Malm2,
in Utah’s colorful Dixie


#4
  I purchased the most amazing opal. The dealer called it Nevada
opal. 

Hi Karen, It sounds like Virgin Valley, Nevada, opalized wood. I
have a few pieces and it’s amazingly beautiful stuff. Chances are,
it’s been stabilized with Opticon or something similar. There’s
nothing wrong with this; in fact, most of the Virgin Valley material
is notoriously unstable and would fall apart if not stabilized. The
process affects only the matrix, not the opal. As for care, I’d
treat it the same as any fine opal don’t expose it to extremes of
temperature and don’t store it for long periods in a dry environment
(like a bank’s safety deposit box). The plastic bag with a wet
tissue is unnecessary. By the way, the black matrix Virgin Valley
material is especially rare; you’ve got a real prize!

Beth


#5
    I purchased the most amazing opal. I'm about to set it, but
wonder if there is a way to protect it afterwards. Someone
suggested placing it in a plastic bag with a wet  tissue to
maintain a high humidity level. 

I’m no expert on opals, but that just sounds like a great way to
grow a bag full of mildew. My father used to cut opals (still does
once in a while, but at 86 his eyes aren’t what they used to be). He
keeps his uncut opals and a few of the remaining cut cabs he has in
small jars of mineral oil. I’m sure someone who actually knows how
opals should be stored will jump in here with better suggestions.

–Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com


#6

Karen, the Nevada opal has some of the finest color of any opal. It
also has some nasty problems, mainly that it is not very stable. I
have had pieces start to craze and crack within 20 minutes of being
removed from water. I have had pieces that went from water clear
with great fire to a sugar cube look within a similar time frame.
Luckily the last resorted to it’s former life after about 10 minutes
in a glass of water. I also have a nice piece of wood with opal in
it. If I wet it, the opal really stands out. I put it in water
over night, and it was just the opposite of the earlier stone, all
the color disappeared. These stones are called Hydorphane Opal.
Some will show color only when wet, others only when dry. Neither
is a very good choice for jewelry. They can vary in weight by
several percent between dry and wet states. Some, when dry, will
stick to your tongue like natural turquoise.

As to your opal, what was the state of it when you acquired it. Was
it in water, or was it a dry stone? Also what is its history, IE
how long has it been out of the ground, and how has it been stored?
If you got the stone dry, and it has been in that state for at least
a couple years, then you might just have a rare Nevada stone that is
stable. They make great jewelry items. If you are not sure of the
stone, let it dry for a while, knowing that crazing and cracking are
possible at worst, and turning milky white is the next worst thing.
Don’t try to accelerate the drying process. Just normal room
temperature with mid to low humidity, IE 50% to 20%. If the stone
stands this for six or seven months, then you may have a jewelry
piece.

As to care after you set it, a little moisture will not harm it, and
might do it some good. The moist tissue in a zip-lock bag is
sometimes called the “Nevada Cure” as it slowly lets the moisture
escape and reduces stress on the stone. The normal cure time is on
the order of two to three years without opening the bag. The results
are spotty though.

If the stone has been dry, and it has been cut and polished for
several months to a year and is still in good shape, the best care
you can give it is to just occasionally wipe it down with a damp
rag. Never store it in a safety deposit box as the extreme low
humidity, on the order of 1 to 2% will damage even a sound
Australian opal. Never use any oils on the stone and Never use
glycerine (an alcohol family chemical that will suck any remaining
moisture out of your opal). Avoid extreme temperatures. Nothing
below freezing, and nothing so warm that you can’t hold it in a
closed hand. This advice applies to all opals.

Don at Campbell Gemstones


#7

As stated, this material is notorious for instability. My wife made
a neckpiece for a friend out of a limb casting of black opal. The
limb piece fell apart but the knob she was going to cut off “fell
off” or cleaved just where she was going to cut it. Lots of red
fire, in a tear drop form. Beautiful to say the least. The casting
was collected many years ago and was in a collection. All has been
stable for about 7 years now…

There are so many “methods” and Ideas as to how to keep opal, sort
of mind boggling. I tend to stay away from mineral oil as it (to
me) makes no sense (where is there mineral oil in the opal fields??)
but I think it has come into use as it doesn’t grow algae like water
does. I store of matrixed opal dry, the solid material in water.
That is just me, but it makes the most brain sense to MY brain.
Always open to other thoughts and thinking, but to date this is
where I am on it.

Hope your piece is stable, it is beautiful material.

John Dach

MidLife Crisis Enterprises
C.T. Designs (sculptures)
Maiden Metals (foundry)
MLCE.net (web site)
P.O. Bx 44
Philo, CA 95466


#8

Kathy, Opals should not be stored in oil of any kind. The stone being
porous, they absorb oil and that depletes play-of-color. The oil
bearing layer can be ground off in the case of rough. If you’re
serious about opal, store it dry. That way you will know if a parcel
is cracky and not waste your time cutting it. I wait at least 6 mo. to
a year before cutting especially if the parcel is newly mined. (old
stock is best when you can get it) later, Mark

Mark Thomas Ruby
SunSpirit Designs
Loveland, CO
970 669-7075


#9
He keeps his uncut opals and a few of the remaining cut cabs he
has in small jars of mineral oil. 

I recently came across the following article which speaks to this
point. Note that it’s about specimen opals, not about opals set in
jewelry.

Beth

Storage of Specimen (not to be cut) Opals:

– Liquid Silicon: This viscous semi-liquid can protect the stones
from mechanical shock and sudden temperature changes. It is close to
the refractive index of opal which enables it to mask - not heal -
existing cracks. However, it may be impractical for use in large
quantities due to the expense.

– Glycerin: This emollient can also protect opal and hide cracks,
plus it is inexpensive. However, it can enlarge existing cracks and
induce new cracking.

– Mineral Oil: the viscosity of this material may protect opals
from external damage. However, it is not recommended for long-term
storage because opals will absorb the oil, become dull, eventually
turn yellow and lose their play-of-color.

– Water: The cheapest, safest and best fluid in which to store and
display specimen opals. It is recommended that ordinary bleach be
added sparingly (1 or 2 drops) to distilled water for preventing the
formation of algae.

Compiled by Barr L. Doty and condensed from The Opal Express 12/98.


#10

The reason mineral oil is used is that the refractive index of
mineral oil is close to that of opal thus disguising any
imperfections. If you want to keep the water clear of algae use a
few drops of bleach. KPK


#11
    Kathy, Opals should not be stored in oil of any kind. The
stone being porous, they absorb oil and that depletes
play-of-color. The oil bearing layer can be ground off in the case
of rough. 

Dad’s had some of these opals stored in mineral oil for probably 25
to 30 years. But now that I think about it, the liquid in those jars
might be glycerin. I’ll have to ask him. If it’s mineral oil, I’m
sure it’s too late to salvage them.

–Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com


#12
  Dad's had some of these opals stored in mineral oil for probably
25 to 30 years. But now that I think about it, the liquid in those
jars *might* be glycerin. I'll have to ask him. If it's mineral
oil, I'm sure it's too late to salvage them. 

glycerin is not good for opals either as it sucks the water out.
Once in glycerin, they had better remain there or be switched to
water, but you can probably never cut them.

Cathy


#13
 If you're serious about opal, store it dry. That way you will know
if a parcel is cracky and not waste your time cutting it. I wait at
least 6 mo. to a year before cutting especially if the parcel is
newly mined. (old stock is best when you can get it)

Now there’s some advice I can pretty much agree with! Reading
Orchid over the past few years I’ve been amazed by the many accounts
I’ve read about unstable opal. I speak from many years of
opal-cutting and have experienced very few “cracky” opals in all that
time. There are two reasons for that. I buy only Australian opals
(unless I want an expensive thrill). And I know my opal dealers and
expect them to pre-screen any unstable material or replace any that
goes bad. There are bad Australian opals, too, but the word gets
around to reliable dealers quickly. They don’t want cracky opal any
more than I do.

I’m from Idaho and have mined opal in both Idaho and Nevada. Here’s
the sad truth: most opal from that region is far too hydrated and is
almost guaranteed to crack. It makes incredibly beautiful specimens
but is not commercially useful opal. There are a few stable stones
and there are people who claim to be able to stabilize the rough; it
may be true but I’ll let others take the risks. Anyone who expects
to successfully sell this opal in jewelry is looking for trouble in
my opinion (with the exception of properly made triplets from
Spencer, Idaho material).

The only other precious opal I’ve found to be mostly stable is from
Piaui State in Brazil. In the 1970s when rough was briefly
available, there were two types: alluvial and mined. Brazilian
alluvial crystal opal may be the most stable I’ve ever cut. It is
harder than opal from other sources, with over 60% of the pieces
tested by late opal dealer Bill Maison able to scratch quartz! It
also occurred in large gem-quality pieces (up to 4 oz. with a few
pieces to 10 oz.) and featured unusual and dazzling columnar fire
patterns. Unfortunately the mined opal was stressed by heavy
machinery rumbling over it and would often crack within a year of
being cut. I don’t know the present status of that location but see
very little material on the market.

I’m wary of Mexican precious opal. It’s gorgeous but very prone to
cracking, especially the so-called Canterra matrix type. I’ve heard
the same thing about Indonesian opal and the “thunderegg” opal from
Ethiopia. In general they are all volcanic opals and very few
volcanic opals are stable in my experience.

Storing opals in water is like eating chicken soup for a cold: it
can’t hurt but it probably doesn’t help either. Opal is either
stable or it isn’t. Unstable opal will eventually craze. I consider
oiling opal a shady practice, mostly to hide cracks from buyers. It
actually hurts good opal which needs to “breathe” to keep itself
hydrated from humidity in the air. That’s why you should never store
opal in a safe deposit box. The same low humidity that preserves the
paper in wills and stock certificates will dehydrate even stable
opals and crack them.

If you are lucky enough to own a fine opal protect it from hard
knocks, too much heat and sudden temperature changes. Then just
enjoy it.

Rick Martin
MARTIN DESIGNS