Oregon Sunstone and Chinese Red Feldspar:
An exercise in forensic mineralogy

Dr. Rossman presented a compelling Power Point Presentation with an overview of all known and alleged sources for Red Feldspar for the Mineralogical Society of Southern California on March 13. He stressed the necessity of using experimental research, based on the principles of chemistry, mineralogy and geology, to arrive at conclusions pertaining to gem varieties of red feldspar and its sources. He also emphasized the necessity to recognize the limitations of one’s instruments, knowledge and skills when making claims and assertions about treatments and localities.

Dr. Rossman has been studying Oregon sunstone since 1985. This is not a new topic for him. He made it quite clear that many of the “reports” and blogs presented on the internet are based on misinterpretation, misunderstanding and misrepresentation of the science necessary to find the truth. Many, of the reports offered online in reference to determining treatment and location of this mystery feldspar have been based on BAD science. More precisely, they are based on rather casual observations made with an insufficient sample size, the lack of proper instrumentation and perhaps, most importantly, the lack of knowledge to recognize the potential for error in their conclusions.

We have long suspected that the plethora of red andesine and labradorite suddenly available from mysterious remote locations was very suspicious. We suspected that the material has undergone some sort of treatment to make it red.

We were right!

But the early reports presented online by individuals and lab(s) were misleading and premature. As it turns out, one can not rely on observational techniques using immersion microscopes, hand-held spectroscopes, refractometers, filters etc. to determine treatment and localities of this gem.

Natural red andesine will display the same characteristics as treated material when studied with observational instruments. The same process used in a lab to induce the diffusion of copper can and has occurred naturally!

So, what forensic techniques were used by Dr. Rossman to make a determination on treatment and locality?

Extensive experiments were conducted to see what effect simple heat and/or irradiation would have on yellow andesine in a controlled lab environment.
Quick answer: none.

Experiments were performed by Dr. Emmett in conjunction with Caltech to determine if copper could be artificially diffused into yellow andesine/labradorite and induce a red coloration.
Quick answer: yes it can*
*This “diffusion” is profoundly different from the beryllium diffusion in corundum. It can NOT be detected by microscopic observation of color concentrations nor alteration of inclusions!

Just because something CAN be done does not mean it is being done. Further tests were needed to positively prove or disprove diffusion treatment in individual samples.

Rossman and his colleagues at Caltech have conducted extensive chemical, spectroscopic and radioactive isotope experiments with an enormous sample size of material, both rough and fashioned, from all purported locations.

He discovered that samples from various international locations have very diagnostic chemical markers. Dr. Rossman was able to clearly separate gems submitted into three groups originating from Oregon, Mexico and the Mongolian/Chinese border region. Using that criterion he was able to resolve that NONE of the material represented as Tibetan or Chinese red andesine/labradorite originated from Mexico or Oregon! This is huge as many allegations were made claiming that Mexico was exporting vast amounts of yellow plagioclase to be treated in international locations.
FALSE!

So what is the source of the red feldspar that is not coming from Oregon?

Using the principles of tectonic geology in concert with the known chemistry of the feldspar group, Dr. Rossman determined, with the aid of extensive radioactive isotope experimentation, that material represented as Chinese red andesine and Tibetan red andesine had the same chemical markers as the yellow feldspar submitted as originating from the Mongolia/China border. This makes the Tibetan source suspect as we would expect the Tibetan locality to have unique chemical markers. Furthermore, based on potassium argon ratios in all of the samples studied, it was determined that it is likely that all red andesine not originating from Oregon, has been subjected to laboratory diffusion with copper to produce it's red color.


Can we, as gemologists, use our standard gemological instruments to determine treatment?
Quick answer: no.

Can we determine origin from visual observation?
Not reliably. Many treated feldspars have virtually the same appearance as those which have not been artificially diffused.

Moral of the story: “Accept that you don’t know what you don’t know.”

PS. Laboratories performing this diffusion treatment are located in China, not Thailand.

Can you say BOMBSHELL? But we suspected lots of this all along. Thanks for posting all this Barbra.

Thank you Barbra. Very interesting. Not surprisingly it didn't take long for the 'spin to begin.'

And did the Congo material also has the same chemical markers as the Mongolian?

I wonder what Gemfrance is going to make of that!

DSN must be rubbing their hands right about now.

Barbra,

Excellent report! Has Dr. Rossman written a paper or is there to be a publication?

Thanks Richard.
I am not aware of any report immediately forthcoming.

Africanuck, in regards to samples studied that were reported to be from the Congo:
Certainly, every gem has NOT been tested and I recall Dr. Rossman stating that he was not specifically aware of feldspar submitted by GemFrance, but of those submitted and represented as being from the Congo, the chemical markers are the same as the feldspar from the Mongolia/Chinese border. And they also contain a potassium/argon ratio consistent with treatment.

Is it possible that a source in the Congo exists? Of course...but it can not be documented at this time.

PS. I clicked on the link supplied by Bigfish and couldn't read past the first paragraph. Bonkycat just doesn't get it. She never will. Robert James suspected treatment and tailored his studies to support his suspicions. That's really not acceptible.

Hello,

Just to say that I am still waiting for an official report from a well-known US laboratory who has studied my samples and other red feldspar from other sources.
But I cannot talk in place of this laboratory.
So wait and see...

I have always cooperated with the laboratories. But I don’t remember having never received any asking from Dr. Rossman to send samples.


I appreciate "Moral of the story: “Accept that you don’t know what you don’t know.”

Always take care of the rumours!

Knew it, umm, I mean, suspected it all along.

Well done report Barbra!

Last November I was in Carlsbad visiting with Dr. Rossman (and GIA) when I heard his initial report regarding the chemical makeup and the differences between the locales. It was then I also heard of the radioactive gases being measured to determine that these feldspars had gone through the treatment process.

At the time all suspected the Tibetan material was fishy. Now seeing the tests on the Tibetan that show no gases present at testing, and the chemistry the same as the Mongolian, there is something terribly amiss and needs to be accounted for on the Chinese side of things.

BTW, George also told us at the time that he would produce a report on all this, so we can probably expect to see it in G&G very soon.

bear

I'm looking forward to the printed report, because his lecture featured so many wonderful photos, diagrams, charts, and graphs that it is impossible to really convey how magnificent the presentation was.

I also think, that if anyone is interested in the specifics of potassium/argon ratios we could expand a little on that too, Bear.
'Cause that is a juicy topic!

Regarding the Tibetan location.
G&G recently featured a blurb with photos of the mine site. There is a picture of several red xls in an outcrop. As much as I wanted to believe in the existence of this location, and presumed those doing the reporting were far more knowledgeable than I, I have to admit, I've never seen xls sitting in a matrix that resembled that photo.

Can we assume whatever work they were doing with the supposed Tibetan material will be done with Dr. Rossman's findings in mind?

Does this report mean that the Oregon feldspar miners are going to have a hard time arguing that their product isn’t treated? You got to wonder if anything that’s not red is going to have a little extra copper added.

Good question, Red Dirt.

The study concludes that Oregon material is NOT artificially diffused. It is a natural and untreated product.

The red color of Oregon feldspar resulted from natural diffusion taking place over millions of years in a volcanic environment.

The Japanese Gemological lab that collected samples at the mine is also currently conducting tests. Results should be forthcoming.

And just want to clarify... the interaction of the chemistry in it's formation took place in the magmatic stages, but the diffusion of the Ar gases (over millions of years) took place in the alluvial environment.