Wednesday, October 5, 2011

For all you opal lovers, especially those who have been drawn to Ethiopian opal, here's some breaking news that may cause you to pause.

As many may know, there is lovely, natural (that is, opal not treated in any way) Ethiopian opal. Recently, a beautiful "black" Ethiopian opal began entering the market, from Welo (also spelled Wollo). It is represented as natural, untreated opal, and this claim — that the opal is natural and it's color is natural — has been "confirmed" by several laboratories. Questions recently arose, however, over some especially beautiful pieces, leading to more extensive testing, and the results were shocking.

New findings have shown that most, if not all, of the "black" Ethiopian opal now seen in the market is not what it appears to be! It is either treated by innovative new "smoking" techniques to obtain it's black-opal appearance, or the material is not stable (that is to say, it will crack and break fairly easily, and quickly)!

For some time the opal trade has been aware of naturally dark material that can be referred to as "black opal" from some sources within Ethiopia, but this "natural black opal" was found to be very unstable. The recently mined material from Welo (Wollo) was stable, but lacked the fiery character that is so highly prized in opal. So by finding a way to "smoke" the material to make it darker, they could create a more fiery character, and a more highly prized and costly appearance.

Smoking techniques are not new where opal is concerned, but what is now being used on the Ethiopian opal introduces a new twist to the old smoking method, which is why the treatment was missed by respected gem-testing laboratories.

The old technique was used on low quality opal, such as Mexican material, to darken the color of the base material, which causes — by contrast — a more fiery play of color. It was done simply by wrapping the opal tightly in brown paper, placing it in a covered container, heating over medium heat until the paper is completely charred, then cooling and washing it. The result was a much prettier opal!

This "old" technique (or similar approaches, all of which are still used today) affects only the surface and is easy to detect simply by applying a little saliva to the surface of the stone: if the fiery play of color is visibly reduced when wet but then returns to its more fiery character when dry, you know it is "smoked."

When the Ethiopian material was cut open, however, it was discovered that the darkening effect penetrated the entire stone, and so normal, routine testing techniques used for opal didn't indicate smoking, or dyeing, or any other treatment. Yet once the researchers probed deeper in studying this new "suspect" material, and applied more sophisticated techniques not routinely used for opal, the existence of carbon (from the blackening/smoking technique used) was immediately detected.

Now that we know such a treatment is being used, and how to test for it, it poses no problem for laboratories. And the effects of the treatment appear to be permanent. I like the product, and since we now know how to distinguish it from "natural" black opal, I think it makes a nice opal alternative. Also, since it can now be detected, it poses little risk to the trade ... as long as people are aware of the treatment, and take steps to ensure the material has been properly represented...and priced!

In concluding, I must urge everyone to be extra cautious where this material is concerned. While it is possible that one day a source of fine, natural-color black Ethiopian opal will be discovered, at this time, none of the material being touted all over the internet and elsewhere as "natural black opal from Ethiopia" is, in fact, natural-color black opal...what is flooding the internet and TV sites is smoked and much of it is over-priced for what it really is. Today, when buying any Ethiopian "black opal" represented to be natural color, be sure you buy only from a reputable seller you know you can locate tomorrow if the opal turns out not to be as represented...and be sure to send it to a respected gem testing laboratory to confirm the facts.

For those interested in learning more about this material, and how its "smoked," here is a link to gem-testing laboratory that made this discovery, and the report they have just recently:

http://www.stonegrouplabs.com/SmokeTreatmentinWolloOpal.pdf

It's compelling reading, and the findings appear to be indisputable.

Antoinette Matlins, Professional Gemologist

Author of Jewelry & Gems—The Buying Guide, 7th Edition and

Gem Identification Made Easy, 4th Edition

www.antoinettematlins.com