Rubies and sapphires from Didy, Madagascar

[vincent pardieu]

Dear all,
I would like to inform you that we have published a new field report.
It is about the new ruby and sapphire deposit near the village of Didy in Madagascar. The rush happened for 3 months then the Malagasy authorities send a force to expel the miners as the discovery happened to be in a protected area part dedicated to conservation.

You will be able with this report to live the gem rush that occurred there as we lived it.
You will also find a lot of information on the very poorly known other deposits from the jungle covered region in the north east of Madagascar: the ruby and polychrome sapphire deposit at Andilamena, the blue sapphire deposit at Andrebabe and the Mandraka/Toamasina sapphire deposit located near Toamasina (Tamatave).

and finally you will find an extensive inclusion study of the samples we collected during the expedition to Didy.

The pdf is available on the following pages on GIA websites:
http://www.giathai.net/lab.php
http://www.giathai.net/lab_field_reports_VP03.php
and it will be soon also on:
http://www.gia.edu/research-resources/n ... index.html

Hoping that you will find it interesting.
Do not hesitate to send me your comments. It is still a work in progress and within few week we will publish a complete study on the rubies and sapphires from Didy.

All the best,

[gemlover]

Thank you for sharing. I am enjoying reading the report.

John

[Osman khattak]

Thanks for sharing such an interesting information.

[WClee]

Thanks a lot!!!! Very interesting and informative writing!

[vincent pardieu]

Thanks guys,

Nice to read that you enjoy reading that report.
Soon a second report focussing on the gemology of the samples we collected will also be published.

I will keep you informed of course.

All the best,

[danielle]

Hi Vincent !

Thanks for sharing this interesting report nicely illustrated !The pictures are very beautiful , we learn a lot .

What exciting life than yours !

... I'll be glad to read you again ...

[Barbra Voltaire, FGG]

I really enjoyed reading the article, especially the geological references.
Question:
The corundum found in many areas of Eastern Madagascar formed metamorphically and contains many of the same mineral inclusions as sapphires found in Burma and Kashmir. Inclusions, which were formally diagnostic of Burma and or/ Kashmir origin.

How would a lab (like GIA, AGL or Gubelin) differentiate localities when trying to do an origin determination?
Is it now a function of analysis with sophisticated spectrographic instrumentation? If, so, what are the determining characteristics one looks for spectrographically?
Or, is it more of a subjective determination based on the experience of the person doing the report?

[vincent pardieu]

Hi Barbra,

Nice to read that you enjoyed the article.

Regarding the blue sapphires I wrote in the report that regarding their inclusion scene the blue sapphires from Didy are reminiscent of the blue sapphires from Mogok in Burma while the rubies from Didy are reminiscent of the rubies from Winza (Tanzania) and Montepuez (Mozambique).

I never wrote that they were looking similar to sapphires from Kashmir. I don't know where you got that.... I also never said that the inclusions in Didy stones were before diagnostic from Burma, to the inverse I wrote on page 45 that these sapphires of the "iron rich metamorphic type" are "mostly known to originate from deposits like Mogok in Burma (Myanmar), Tunduru, Umba and Winza in Tanzania, Andrebabe and Mandraka/Toamasina in Madagascar and more recently from Kataragama in Sri Lanka."

Regarding the way a laboratory like the GIA is working on origin determination it is quite simple in the principle but it can become rapidly very complicated when you start to look at details or examples:

But to give you a short concise explanation about what a lab like GIA does here is what I can tell you: It is an opinion based on inclusions, basic gemological properties and the spectroscopic and chemical analysis of the stone.

Now how we do that?

Well it is again simple and complicated at the same time:

First at GIA we do our very best to build the best possible reference collection with samples collected as close as possible from the source and also from multiple, independent sources. This is a very unique approach as GIA is to my knowledge the only gemological laboratory to have a field gemology department and to send regularly sent some gemologist to collect samples in the field from new deposits to complete its reference collection but also from known deposits in order to keep it up to date.

Then back at the lab, these samples are catalogued, fabricated and studied by GIA Research Gemologists using traditional gemological techniques but also with advanced techniques like the identification of inclusions using Raman, to trace element chemistry using EDXRF and LA-ICP-MS passing by spectroscopy mainly using FTIR, UV-Vis.

You can see an example of what I mean with the report about sapphires from Kataragama ( http://www.giathai.net/pdf/Kataragama.pdf ) and to a lesser extend with this report about rubies and sapphires from Didy, as in this case the report is far to be complete regarding the gemological study of the rubies and sapphires from Didy.

When we try to identify the origin of a given stone we first collect all the data possible on that stone using these different techniques available in the lab and then typically we compare this data with what we know from the study of the stones from our reference collection. In some cases, when the stone has a very particular trace element chemistry only known from stones of one deposit or when it has some diagnostic inclusions, spectroscopic features or even better when the stone has a unique combination of diagnostic features (inclusions, trace element chemistry, spectroscopy, etc...) then we can base our origin opinion on very solid facts.

But in some other cases we lack these diagnostic features. This is particularly the case with clean, or heated stones (as in that case the inclusions that could have help you can be melted and difficult to identify, furthermore the spectroscopic features may also have been altered).
You can get typically a case where lets say the analysis with one instrument indicates that the stone is very likely to be from origin A (without excluding B, C and D) and when using a second instrument he get a result more favoring origin B (without excluding A and D) and when with a third instrument he gets lets say either A, B and C. In such case C and D seems excluded but still it is not possible to exclude A or B. But depending of the case, a given gemologist might decide to go for A more than B based on some subjective reasons related with his experience and his analysis of the data collected. In some other cases another gemologist with a different experience might prefer to say that he was not able to identify a probable origin or even that in his opinion the stone is more likely from B...

My personal opinion in such difficult case, is that what is important is that each gemologist do his best to give his most honest opinion based on facts (if possible) or on the best of his knowledge. As I repeat many times, to young gemologists lacking confidence, the different between a good and a bad gemologist is that in my opinion a good gemologist knows when he has to say "I don't know". Nevertheless there is nothing wrong to say: "I'm not 100% sure but based on my study of that stone I believe that this stone is most likely from A". You might be wrong, but I feel that it is Ok in my opinion as long as you remain honest because what you are asked after all is just an opinion.

Again and again: We are not providing "origin certificates" but "origin reports". I know that people in the trade speak all the time about certificates, but well I don't know many serious labs providing certificates, all the ones I know are providing "reports".

Hoping to have helped,

All the best,

[Barbra Voltaire, FGG]

Thanks for the clarification and YES it has helped a lot.
My post was directed towards how a lab determines origin when many of the inclusions which help determine locality are currently seen in gems from several localities.
When I was a gemology student in the 80's the studied inclusions which defined localities were far more limited. There was no corundum coming from Madagascar or Winza
Oops, I threw Kashmir in the mix erroneously.....sorry.

So, as I understand it, it is presently beyond the scope of a gemologist with standard gemological instruments to call an origin in corundum with confidence based on an inclusion scene....

Agreed?

Thanks in advance, Vincent.

[vincent pardieu]

Hi Barbra,
Well just using the microscope in some cases you still can find out where a stone is from, but in many other cases you will need also to check the stone with other techniques like trace element chemistry and spectroscopy in order to eliminate some possibilities.
The classic case is possibly emeralds with jagged type 3 phase inclusions: Such inclusions are now known for emeralds from different deposits in Colombia but also from Nigeria, Afghanistan and China. But using UV-Vis and chemistry in most cases you can separate with confidence these origins...

All the best,