How do I know if my opal is real?

[duker]

I bought an opal on ebay, and I want to know if it is real. I have inspected it, and the colours are not shown in the alligator skin pattern that is usually found on synthetic opals. I do not know what else to see.

It is not a doublet nor a triplet or some of those things. I am pretty sure it is an opal, as it has the common qualities associated with opals, but I am not sure if it is natural or artificial.

It is faceted, oval cut, approx. .8 carat, multiple colours -including red, green, yellow, cyan-, the most dominant are violet and blue. The colours are more shiny under sun light than under inner house light. Also the colours shine more -like under sun- under light comming from a LEDs lamp I have. It is transparent, with an slight milky white-yellow tone, but you can perfectly read a letter, if you put it over a written paper -I read that was the test to know if an opal is really transparent, and it pass it-.

I have read that natural opals have some fluorescence that synthetic opals do not have. But I could not find any other instructions about that. I want to know how do I test if my opal has the fluorescence they are talking about. What is that fluorescence and how do I discover if my opal has it?

DO you know any other test I could do?

 

[Richard M.]

DO you know any other test I could do?

Yes. If it's faceted it's very possibly an Ethiopian opal from Welo. Faceted stones from that location are very popular right now and many are being sold on EBay. Welo opal, while beautiful, has the unusual property of being reverse hydrophane and loses its play of color when immersed in water. (Regular hydrophane opal has no play of color *until* it's immersed in water).

I do NOT recommend putting your opal in water. While most Welos dry out and regain their POC within a short period, some do not. But you can determine if it's hydrophane by placing the stone on a soft surface to protect it from a fall and see if it will stick to a wet fingertip. I know of no hydrophane synthetic opals. Of course opals from other locations can be faceted and are, so my test will only indicate an Ethiopian origin.

Richard M. (Rick Martin)

 

[duker]

DO you know any other test I could do?

Yes. If it's faceted it's very possibly an Ethiopian opal from Welo. Faceted stones from that location are very popular right now and many are being sold on EBay. Welo opal, while beautiful, has the unusual property of being reverse hydrophane and loses its play of color when immersed in water. (Regular hydrophane opal has no play of color *until* it's immersed in water).

I do NOT recommend putting your opal in water. While most Welos dry out and regain their POC within a short period, some do not. But you can determine if it's hydrophane by placing the stone on a soft surface to protect it from a fall and see if it will stick to a wet fingertip. I know of no hydrophane synthetic opals. Of course opals from other locations can be faceted and are, so my test will only indicate an Ethiopian origin.

Richard M. (Rick Martin)

Hello, I did the test. I wet my index finger with water, and then I touched the faceted opal, upside down, and elevated my finger. The opal actually seemed to stick to my finger slightly, and it stick for a fraction of time. While I was elevating my finger, perhaps at 5 or 7 cm, the opal fell. So it seems that it stick a little. I am not sure if this indicates it has the properties, as it does not stand stick, but falls after a little time -perhaps a second-.

What do you think?

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Edit:

I repeated the test, soaking my finger more, and the opal sticks for more time, 3 seconds, later the sticking becomes weak, and finally fall.

It seems that adding more water augmented the sticking duration. I hope this to be a prove of its authenticity. I hope...

 

[chrono]

It certainly sounds like a natural Welo opal.

 

[Richard M.]

duker, I hesitate to suggest this because some will go "Yecchhhhh!" But the easiest way to do this test is with the tip of your tongue because it gives a more positive indication than a wet fingertip. With the opal in completely dry condition (wait at least 24 hours after your fingertip test), just touch it to your tongue. If you feel a very slight "grabbing" sensation and a tiny amount of resistance when you pull the stone away, that's a strong indication of hydrophane.

I'm using Occam's Razor in suggesting your stone may be Welo material. 1) There's a lot of Welo on the market right now. 2) It is commonly faceted. 3) A lot of it is offered on EBay. Therefore the simplest explanation may be the best one. But if you want proof positive, take your stone to a qualified gemologist for a scientific ID.

Richard M. (Rick Martin)

 

[gsellis]

Welo can be hydrophane and not hydrophane. Sara Lee Boyce used the finger test and your's sounds like hydrophane Welo. While water should not hurt it, don't soak it as it will discolor for up to two weeks. Also, anything in the water will transport into the stone. Welo should not be prong mounted, but the jury is still out. I have a couple that have been in prongs over 2 years with no adverse effect. BUT, I am not wearing them either. I also worry that if you do get it wet in a prong mount, there may be some expansion. That could damage it. Another BUT... do not try to make it dry. Dry environments are death to opal. Safe deposit boxes are considered opal graveyards. So...

So as long as you know that the color can vary based on moisture, and are good with that enjoy. It is a more digital opal and the structures are not as linear as Oz opal. But it is seriously fun. And that is what is important.

 

[Richard M.]

George, I know that not all Welo is hydrophane. But most is. So...Occam's Razor again.

When you say Welo is "more digital" does that mean Aussie opal is "more analog?"

Even though it's been around several years now, Welo opal is still unproven as a long-term jewelry stone. It's remarkably beautiful but it does have a few little peculiarities. Some studies indicate it's more resistant to breakage than opal from other sources. But it's that hygroscopic (thirsty for water) property that leaves unanswered questions. We won't know the answers until it's been in wide public use for a few years longer and get feedback from purchasers.

As to its "digital" nature, I haven't seen any SEM studies of Welo structure. Apparently you have. Can you point me to them? I'm aware of what is called "digital appearance" in Welo and I've seen something similar opal from Piaui, Brazil. I'd be interested in seeing how it may relate to internal arrangement of the spheroids.

Richard M. (Rick Martin)

 

[gsellis]

ROM, Sarah Lee Boyce has seen studies on it. I was just the humble student. And Sarah Lee is not digital (email and web are not her thing). I don't know the source. Maybe ask Paul Browning? I am not sure how to reach him.

 

[Richard M.]

You had me at a loss so I did a search for Sarah Lee Boyce and learned she's been cutting opals since 1991. I've been cutting and selling precious opals since 1961 so I know a little about the interesting beasts. But there's always something new to learn.

I have no idea who Paul Browning is. What is his role in determining Welo opal structure? Is Australia's CSIRO, which did the first SEM work on opal structure, involved?

Richard M. (Rick Martin)

 

[Quantz Studios]

George, do you mean Paul B. Downing?

 

[Richard M.]

Yes, Paul Downing would certainly make sense in that context. Good suggestion Ryan. I didn't immediately make that connection.

Richard M. (Rick Martin)

 

[beau-wy]

I could be dead wrong, but my last contact with Paul Downing a few years ago, he was retired from opal and devoted to fly fishing.

 

[Richard M.]

Yes, Paul moved to Colorado and established Majestic Press to publish his own opal books and new ones on fly fishing. I imagine he maintains an interest in precious opal as well and I thought perhaps he'd shown up somewhere as a guest expert/lecturer.

Richard M. (Rick Martin)