Incorporating opal

Jewelry Discussion
21 
Once again, I reiterate my oft stated opinion.....if you wait long
enough, all opal will craze. Maybe you just haven't waited long
enough yet Kevin~!!

I’m not trying to offer advice or a solution to a problem, but rather
asking a question. I’ve heard things said about opals and wonder
whether it’s true or an urban myth. People say that an opal should be
worn regularly and that they absorb the oils from the skin - and that
if they are not worn regularly, they dry out and crack. Is this the
case and if it is true, could this be why some opals craze? Or is it
just a load of rubbish?

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

22

Hi Derek,

Chemically opal, of course, is SIO2 H20. Some people say that the
crazing, if it's going to be unstable, comes from the evaporation
of water from the stone. I don't know if this is true, but I've
certainly seen opal crack.

I just asked a question about this today (7th July) and it will
appear tomorrow (8th). It would appear to make sense. Any GG’s out
there who can elaborate on the opal drying out scenario?

By the way, for Helen who enquired about polishing the old stone,
actually older stones, mined roughly more than around 50 years
previous, whether opal or even other species can be particularly
susceptible to crazing when repolished.

I gave it a thorough clean the other day and am pleased to say that
it changed from its grubby grey colour to a lovely white colour again
and I’ve just louped it thoroughly and it doesn’t appear to be crazed
at the moment but the surface is very dinged and scratched. There is
good colour play but it does seem to be impeded by its scratched
surface, indicating that a repolish will (if done successfully)
restore the beauty to stone.

Some topazes can fade as well

I’ve had a few blue topaz fade to virtually colourless and none of
them were ever kept in the sun. I’ve had other blue topaz that are
as vibrantly blue now as the day I bought them.

If you want to take the risk of polishing it, it really should be
done wet with cerium or aluminum oxide on damp leather.

I’ll bear your warnings in mind. I’m not talking about using
anything rotary to polish it. I’m talking about loading a surface
such as leather with an abrasive and doing it by hand. That is far
less likely to generate excessive heat. I know it’s possible as
truing up a bezel with figure of eight motions on sandpaper can
quickly generate heat but it’s easier to control if done by hand than
with rotary equipment.

Thanks for the advice.

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

23

Hi there,

I’m usually a lurker, as I don’t work in metal these days, but I do
cut opals and am interested in the entire industry. Occasionally
I’ll pop up with something stone related.

The crack and craze thread here caught my attention.

Opals and emeralds are worlds apart of course. Dunno much about
emeralds, but opals will craze or crack on you pretty readily. They
get lonesome, and you have to hold them and talk to them regularly,
sort of like cats. Just kidding of course, but they do not thrive in
storage. Safety deposit vaults are useless, you might as well go
ahead and microwave your opals. In fact, you are. Lotsa bank vaults
use ultrasonic motion detectors and the vaults have a very dry
environment. Opal-killers. Home jewelry boxes are almost as bad.

But some opals are just going to crack or craze. I usually let rough
sit around for several months before I cut it. I’m pretty hard on it
while cutting, it gets too hot in the dopping and polishing phases,
and i put the freshly polished pieces into my freezer for a while
right after finishing them, to separate the stones from the wax and
incidently, stress the stones again. If they survive that ( I usually
lose at least one per batch) I let them sit another week or two
before photos and listing. I’ve had freshly mined and cut stones from
Brazil, Australia, Mexico and Ethiopia crack within days of cutting.
I had a parcel of chocolate Ethiopian arrive in a hundred tiny
pieces, it all cracked and fell apart in transit. I’ve had very
expensive high quality (?) Coober Pedy Australian crack overnight
after rough shaping. I have had a few crack for apparently no reason
after years. It just happens, rough or cut. There are things you can
do which will accelerate or slow the process, but some will
eventually crack no matter what. I figure better to crack in my shop
than in a piece of jewelry, so I seldom, if ever, have a stone
returned. Early opal mining in Hungary apparently involved months of
slow movement of the rough up to the surface, to allow it to slowly
stabilize. The popular Mexican procedure of storing rough in jars
filled with glycerine has destroyed a lot of good opal there. Storage
in water is a problem too. Rough has to be allowed to dry completely
to evaluate, but often a parcel of rough has been in water since
mining. Now setting is another issue altogether. There’s no opal
which a careless, unlucky or just inexperienced jeweler cannot crack.
As a cutter, I discourage rings. I cut primarily freeforms for
pendants, it’s a much safer way to wear opals and keep their beauty
safe. Buyers of opal rings should understand that opal is a natural
glass and must be treated like a fine crystal champagne flute.

24

Years ago I purchased opal from Coober Pedy in a few jars of water,
cut it, put it in a butterfly case and exposed it to 90 deg.
Quartzsite sun, well knowing the risk, without crazing. I then had a
good selling line for those stones in the case.

Then a few years ago I bought a small jar of Coober Pedy Opal in
water after the seller told me the only reason it was in water was to
make it easier to see (I actually asked him about the stability and
he said it had been dry for years so it was all good stuff!), cut it
and had 80% of it cracked. This was about $3k or so of stuff. Luckily
a customer took them off my hands for $50. Now I don’t have to look
at them.

On another note I was lucky enough to go to West Coast Mining’s
claim at Opal Butte, Oregon. They charged $60.00 for a 5 gal bucket
subject to search. Anything more being extra. Anything really good
being extra. The best practice with this stuff was to do nothing with
it for about 7 Years! Now even after more time than that I cobbed
some facet quality material and within a few months some of it also
crazed.

A good practice with some wet/new Virgin Valley material is to place
the stuff you wish to cut in wet napkin or cloth and place it in a
sealed plastic zip bag and let it dry for a few years, slowly.

I will buy opal in the future, but I will never trust it. From now
on I will keep all of it dry for years before I cut it. This includes
Mexican Opal. I understand this will not, in all cases, prevent
cracking or crazing, but such a practice will minimize problems.

Good Luck all!

TL Goodwin
Lapidarian/Metalsmith

25

Hi there,

Sorry about the unfinished post, I hit the wrong key.

Please have a look at some of my opals and opal at
www.opalfire.info, and please drop me a line with opal questions you
may have. A photo guide to patterns, colors, types and body color is
in the works and will be posted soon. Also a lot more opals which I
am photographing now.

Thanks,
Mike Kelley

26 
Any GG's out there who can elaborate on the opal drying out
scenario?

Well, I’m reviewing my Colored Stones phamplets in preparation for
the GG exam in August after I finish Diamond Grading, soooo…From
GIA’s Colored Stones 19 Opal copyright 2001 pg 21:

“If an opal loses moisture, it can lead to crazing: a fine network of
cracks that resembles a spider’s web. The moisture loss can be caused
by heat or excessive dryness, or by exposure to bright light or
direct sunlight. Crazing can be prevented by never displaying opals
in places - such as window displays - where they’re exposed to these
conditions.” From GEMSTONES of the world by Walter Schumann
translated from German reprinted 1986, page 150: “Opal always
contains water: the content varies but it can be as much as 30%. It
can happen that in the course of time, the stone loses water, cracks
and the opalescence diminishes. This can, at least temporarily, be
restored by saturation with oil or water. The aging process is
avoided and the opalescence increased when storing in moist absorbent
cotton”

At the Tarheel Gem and Mineral Club meetings, where we have owners in
a Nevada Opal mine, there is debate over whether to store opal in
water or let it dry out before cutting. After purchasing a piece of
opal jewelry, a person needs to take care not to store it in a dry
environment (like a bank vault or safety box). Regional climate would
also have an effect. Helen is in a relatively high humidity area, but
the advent of air-conditioning has made inside the home environment
of the average US southeast home a very dry climate (wood chair rails
come loose as the glue dries out) so I like Schumann’s idea of
storing opal with some supplied water - now we just have to be
careful of mold!) jeanette (back to the books…)

27 
People want opal rings (I've made many) - what are you going to do,
kick them out?

Supply the demand and make money. (aside from the glory of dirty
fingernails and 50-60 hours/ week after Thanksgiving, its why I do
this)

I hope this thread doesn’t unduly discourage folks from selling
opal. I see a lot of what people already own and honestly I see very,
very few crazed opals, and people have a way of bringing me their
problems. Admittedly empirical.

Broken is another matter. But remember that a diamond may cleave
from the same trauma that breaks an opal.

It's one thing to guide people, it's another to try to imprint them

Typically the opal customer comes in wanting opal. They don’t get
switched from something else. You want it, you buy it…its yours. I
think the jeweler’s responsibility ends after an admonition to treat
it gently, which by and by most consumers already know.

28

I have sold a lot of opal of all qualities in finished goods, both
my work and from wholesale companies.

I have sold crystal, white base, black, boulder, Ethiopian, Mexican
jelly, solids, doublets and triplets and had few problems with
crazing. Most of the problems have been with “boulder” opal doublets.
These problems happened while I owned them. Some companies replace if
crazing occurs.

I do have a few pieces I cut many years ago that crazed, but I have
at least a pound of material, all different Australian and Mexican
opal. The Mexican opal I faceted about 10 years ago has not crazed.

I do repair and I have seen rings with cracked or missing opals, the
rings that have multiple opals where one is missing or cracked never
have crazed stones. I have heated opal very gently with my torch to
dop. I would not recommend it, but I had more material and did not
care if I ruined a small piece. I have heated them while polishing
with no damage.

I have had the most damage while being careless when using shock to
remove opal from a dop, pulled material out of the surface. Did not
do that again. The biggest problem I had was with cabbed Mexican opal
I bought in Mexico at the mine. A few stones have crazed, about one
out of 20.

I have about 100 crystal base opals I cut and polished or preformed
before I moved to Denver about 20 years ago that are just the same as
when I cut or prefomed them. (I have a huge collection of started not
finished projects, both jewelry and gem cutting) I am in Denver, Co.,
I do not store opals in water, and it is virtually devoid of
humidity here, so I have come to believe that storing in water or
wetting occasionally is folklore.

I do not know why different people have such different experiences.
Considering how many I have, how many I have cut, and how many I have
sold I consider opal a low risk gem. The most damage that I have
comes from setting them, I have definitely crunched a few. I
collaborate with a woman metalsmith, we use a lot of opal in our
oneof a kind pieces and have bezel set hundreds of opals over the
last two years. Neither of us have broken a stone or had crazing of
any of them.

Richard Hart

29

Ethiopian opal. I contacted a dealer of this material and he told me
upfront that most of it is very unstable when not kept immersed. My
impression was that a jeweler would find only the rare piece usable.

30

Hi Jeanette,

After purchasing a piece of opal jewelry, a person needs to take
care not to store it in a dry environment (like a bank vault or
safety box). Regional climate would also have an effect.

Thanks for your reply regarding opal drying out. I’ll change the way
I store my opals and put them in moist cotton - great idea, thanks.

Good luck with your GG exams - that’s something I’d love to study
too.

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

31

My ex’s mother’s opal is your bog-standard white opal with
orange/red/ blue/green colourplay that you see in mass produced
jewellery. Is that referred to as white opal? Is there a difference
between that and precious opal? And if so, what is the difference
between white opal and precious opal and crystal opal and even black
opal - I’ve seen pieces called black opal that look just like the
white opal! It’s all rather confusing.

I’m a big fan of mexican fire opal - the red stuff with colour play,
not the pale, uninteresting stuff (and Kirk, if you’ve still got some
I’m still planning to purchase some from you), and I also love
boulder opal and have a few nice pieces of that. I’d like to acquire
some decent pieces of some sort of white opal with good colourplay
but it seems to be a bit of a minefield, with all sorts of stuff
being offered, both rubbish and decent stuff. I bought a few small
pieces of white opal from a UK supplier a while ago. Granted it
didn’t cost very much, but when it arrived, I was shocked to find
that the so called cabochons were no more than about half a
millimeter thick!!! Yes they’ve got lovely colourplay but being not
much thicker than a piece of paper, if any opals are going to crack
and craze, they are - and I can’t imagine anyone would want to
attempt to set such pathetic examples. If anyone has any suggestions
of decent sources for nice but still quite affordable white opal,
I’d appreciate it.

Helen
UK
http://www.hillsgems.co.uk

32 
I have been cutting opal and setting it for more than thirty years
and to this point have not witnessed an opal spontaneously craze.

I feel compelled to chime in on the notion that you must have been
leading a charmed life if this has not happened. I keep all opals for
a minimum of a year, usually more, before setting them to give them
time to get it out of their systems. Nonetheless, a piece I made
about three years ago but have not sold just recently developed a
crack. It has never been worn, let alone whacked, though it is
possible that a gallery put it in a sunny window, I suppose. Now what
do I do with it? Beautiful (freeform) stone, elaborate piece… The
last time this happened, I found a customer who loved the piece (and
the much-reduced price) enough to ignore the crack.

Noel

33 
How do people like that sleep at night?!

A lot better than they will “sleep” for all eternity, if you believe
in an afterlife. Actually, I don’t, but the chance that I could be
wrong gives me some satisfaction in cases like this.

And in this world, what goes around comes around.

Noel

34

Devil’s Advocate kind of question here…

There seems to be a school of thought here that you should keep your
opals in water(or some such) so they don’t craze. Fine, for the
dealer, but in the context of full disclosure, if you do that, water
your opals, then make and sell a piece…does it follow that you’re
dumping the presumed eventual craze on your customer? Aren’t you
delaying financial loss until its someone else’s problem and after
you have profited? Have you or have you not deceived your customer by
not disclosing that you feel its important to water your opals?

I may have missed it, but I don’t see in this thread anyone suggest
that if one waters the stone, one should advise the client to do the
same.

I might think that if you don’t soak your opals the question becomes
moot? Because you haven’t put yourself at an unfair advantage over
the buyer.

Maybe I’m just picking ethical nits here.

35

Hello Orchidland,

What do all you opal experts have to say about crazing in the
lab-made opal (Gilson is one). I have had some Mexican opals and
doublets craze, but have not seen crazing on the lab-made opals.

Judy in Kansas, who is curious… and is confident that an answer
will be shared.

36 
I've had a number of stones just craze up. In fact, recently a
client brought me a beautiful coober-pedy stone cut as a pear...

You’re also the person that said “heat is the enemy of opal”. Thermal
shock is the enemy, not heat. I can heat an opal that will blister
your fingers, but remain undamaged.

And thermal shock is probably the enemy of other stones.

You didn’t say whether the opal mentioned was cut by you; and if it
was who was the dealer. I say again there are people selling opal
rough and cut opal who are not qualified.

Thus ends my participation in this discussion.

KPK

37

Here are what makes opal:

Here are some scanning electron micro scope pictures of opal;

near gem quality california

691×556 97.7 KB

california fire opal:

The last one is documented at 100,000 times magnification.

This type of picture provided the key to how to grow real gem opal.

The size and arrangement and resultant spacing is the key to the
play of colors. water fills the interstitial spaces. Lose the water
and you get cracking-crazing.

Gilson opal with very regular spacing is quite different from Chatum
which is really the same as natural opal. The great uniformity in
the Gilson opal may be the reason it doesn’t crack as he water
leaves it doesn’t create the stress that could build up in the
irregular material. They may use something like PEG added to the
water to keep it from drying out.

SEMS are wonderful expensive toys. The silica spheres really play
with light! this is not a true answer to your question but it is fun.

Jesse no way an expert

38

Nope…I was not the one who said 'heat is the enemy of opal" but I
certainly would not argue with you about thermal shock.
Unfortunately, opal has lots of enemies…it doesn’t end there…see
my earlier post this regard. I did not cut the pear…it was cut in
Israel. I merely recut it into 9 smaller stones!

Yup you can heat opal up till it is hot. But why do that…doesn’t
get you anywhere except now and then loose a good stone. Just
remember, as I have said, what the structure of opal is. That is a
clue to what happens when you heat and opal, subject it to shock,
cold, vibration, etc, etc. Cheers from Don in SOFL

39 
There seems to be a school of thought here that you should keep
your opals in water (or some such) so they don't craze.

Personally, with few exceptions, I don’t believe in watering opals.
The Virgin Valley, NV opal from the ‘wet’ mines (those that have not
dried out yet over the past 100K years or so such as Rainbow Ridge)
must be kept in water or they can fall to pieces right in front of
your eyes.

Consider where most opal we are familiar with (such as Coober Pedy)
comes from (of course it comes from many places and there are
exceptions, different experience ad nausium) but, essentially deep
down in the ground where there has been very consistant humidity,
temperature and pressure for more years than I can count. Suddenly,
it is found by man and brought to the surface where there is very
low humidity, very high temps and a few Gs less pressure. The first
thing I would do if subjected to such conditions would be to expand
and begin dehydrating. Next the opal is moved here and there around
the world into many environments, some cold, some hot, some humid,
some not etc. Some nut puts them into water subjects them to harsh
light so they will sparkle and customers will buy them, take them
home and subject them to even more treatment…maybe dried out
again, heated for dopping (I very rarely do that…cut em free hand
or use glue so they don’t have to be heated) then they go through
terrible vibrations from grinding, smoothing and polishing. After
they are polished they have a rather tough amorphis glassy covering
which might tend to hold it together but also keep moisture both in
and out! Unfortunately, the other forces continue their dastardly
work and work their terrible forces on the delicate opal structure
which is, after all, merely millions of teeny tiny spheres loosly
held together with the moisture between them.

So…why put your opals in water? Once dehydrated, they will not
(except for some very special opal) rehydrate. They will not take on
water, oil, grease, nuthin! But, under some conditions, they WILL
continue to dehydrate (such as a humidity controlled bank vault).
Then after being worn for some time, the glassy surface begins to
disappear. Now, the stone might take on some body oil or detergent a
few microns into the surface but there is not much chance the
moisture will penetrate very deeply…rather the oils etc will merely
yellow slightly.

If an opal starts out with high moisture content, as many of the
Virgin Valley stones, say around 15 to 20 % they will dehrdrate
quickly and craze or worse. If they came from a dry mine they might
only have 2 to 8% and dehydrate more slowly. Now, if they are stored
in water, they might not take on any moisture but they will certainly
give it off more slowly. So one might at best get a few more years
out of it.

Sorry for rambling on a bit but there are so many wrong ideas out
there and I could go on for hours…and I’m not even an
‘expert’…just an old opal cutter and setter. But its late and
thats enough for this session. But I certainly do advise my clients
of all of the above…usually tell them more than they need to know.
At least then they know what they are getting.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry!

40 
There seems to be a school of thought here that you should keep
your opals in water(or some such) so they don't craze. Fine, for
the dealer, but in the context of full disclosure, if you do that,
water your opals, then make and sell a piece...does it follow that
you're dumping the presumed eventual craze on your customer?

In response to Neil’s devil’s advocate question, disclosure of wet
finished opal isn’t an issue, because wetting a stone isn’t a
permanent condition, nor is it a treatment.

Opals stored in bank safe deposit boxes need to be stored in water
or wrapped in moist pads because the humidity is kept around 1/2 of
1 percent. But other than that, I see no earthly reason to keep a
cut and polished opal in water.

Someone in the Opal Society once said, “Water your plants, not your
opals.” The main reason to put opals in water is to get an idea of
what the rough will look like when cut and polished. It won’t hurt
to store rough that way, but it also doesn’t let you find out if the
stone is unstable and will react to drying out by cracking/crazing.

Cracking or crazing can be caused by abuses like not using enough
water while cutting so that the opal gets overheated, overheating
when using dopping wax, or by cutting on an out of round silicon
carbide wheel, so the stone is ‘slapped’ by the wheel, or by
improperly setting it. Storing opals in glycerine pulls water from
the opal and makes it unstable and likely to craze because the
glycerine has a higher affinity for water.

There’s so much to say about opals, it’s hard to stop talking about
them, but I will for tonight.

Carol