Thanks and disclaimer:


Important Note: The author: Vincent Pardieu is an employee of GIA (Gemological Institute of America) Laboratory Bangkok since Dec 2008. Any views expressed on this website - and in particular any views expressed by Vincent Pardieu - are the authors' opinions and do not necessarily reflect the opinions of GIA or GIA Laboratory Bangkok . GIA takes no responsibility and assumes no liability for any content on this website nor is GIA liable for any mistakes or omissions you may encounter. GIA is in particular not screening, editing or monitoring the content on this website and has no possibility to remove, screen or edit any content.


About FieldGemology. org

This website is home for "Shameless Travel Addicted Gemologist" Vincent Pardieu (B.Sc., GGA, G.G.). Vincent is "Supervisor, Field Gemology" at GIA Laboratory Bangkok. He is a gemologist specialized on "origin determination of gemstones".
This is also home for Vincent's regular traveling companions: David Bright, Jean Baptiste Senoble, Richard W. Hughes, Guillaume Soubiraa, Walter Balmer, Michael Rogers, Kham Vannaxay and many others like recently: Philippe Ressigeac, Oliver Segura , Flavie Isatelle and Lou Pierre Bryl.

We are gemologists (gemmologists) sharing a passion for gemstones, gemolology (gemmology), gem people and traveling.

You will find in this website gemological expedition reports and some studies of gemological interest.

Visiting many gem mining areas we saw that people in remote mining and trading areas have difficulties to access to gemological publications. As today the Internet can be accessed in most of these gem mining areas and trading centers, the author started to build this website to give gem people living there the opportunity to see the result of the gemological expeditions they were associated in. It is a way to thanks them for their time and collaboration and to help them to get access to more gemological information.

At the same time the author hope that these expedition reports will please the people from consuming countries interested in gemstones and fascinated by their mysterious origins. Our purpose here is to help people facing difficulties to get quality first hand information about gems and their origins to get the information they need through this website and its links.

With our field expeditions to gemstone mines and gem markets around the world, we intend also here to share our passion for photography, gems and our fascination for the work of the "Gem People" bringing gemstones from the ground to magnificent jewelry.

From the gems external beauty to the intimate beauty of gemstone inclusions, from gem lore to the mines, the people and the landscapes gems origin from, we expect to share with you our passion for gemstone beauty.

We also invite you to join us on some gemological forums we are active in as they are convenient tools to get rapid answers to your questions as they are regularly visited by many other passionate gemologists, jewelers, hobbyists and professionals willing to learn more and share their knowledge about gemstones.


Website Map


Index page: Vincent Pardieu's Blog

About the Author

About me : How did a countryside Frenchman became a "Shameless travel addicted gemologist"? ( Under construction)


Contact the author:


Write Comments:

Fieldgemology Page on facebook

Popular Articles

"Tsavorite, an Untamed Gem" with R.W.Hughes, first published in ICA's InColor (Winter 2008)
"Working the blue seam" The Tanzanite mines of Merelani with R.W.Hughes first published on
"Spinel, the resurection of a Classic" with R.W. Hughes, first published in ICA's InColor (Summer 2008)

Gemological studies

(Apr. 2009) "Sapphires reportedly from Batakundi / Basil area" a preliminary study about unusual sapphires we saw at GIA Laboratory Bangkok
(Mar. 2009) "Rubies from Niassa province, Mozambique" a preliminary study about rubies we saw at GIA Laboratory Bangkok
"Lead glass filled rubies" :
First published on AIGS Lab Website (Feb 2005)

Expedition Reports

Autumn. 2009: GIA Field Expedition FE09: Rubies from Mozambique. (pdf file)

May. 2009: GIA Field Expedition FE08: Melos and their pearls in Vietnam. (pdf file)

Dec. 2008 and Feb-Mar. 2009: GIA Field Expeditions FE01 and FE04: Rubies and sapphires from Pailin, Cambodia. (pdf file)

Aug. 2008: Sapphires and Tsavorite from the south of Madagascar with the AFG (Association francaise de Gemmologie) : Available soon...

Apr. 2008: Expedition to the new Winza ruby deposit in central Tanzania with Jean Baptiste Senoble and the support of the Gubelin Gem Lab

October 2007: Gemological expedition to East Africa (Kenya and Tanzania) with Richard W. Hughes, Mike Rogers, Guillaume Soubiraa, Warne and Monty Chitty and Philippe Bruno:

Summer 2006: Expeditions to Central Asia gem wealth with Guillaume Soubiraa and the support of the AIGS, the ICA and the Gubelin Gem Lab:

Oct. 2005: Colombia by J.B. Senoble

Sep. 2005: Madagascar with Richard W. Hughes and Dana Schorr (Will be available one of these days...)

Summer 2005: Gemological expeditions to South East Asia (Vietnam) South Asia (Sri Lanka) and East Africa (Kenya, Madagascar and Tanzania) with J.B. Senoble and Tanguy Lagache with the support of the AIGS, the ICA and the Gubelin Gem Lab:

- Feb. 2005: A visit to Thailand, Cambodia with the AFG (Association Francaise de Gemmologie) (under construction)

- 2002-2007: Expeditions to Pailin (Cambodia), Chanthaburi Kanchanaburi (Thailand) Houay Xai (Laos) Mogok, Namya (Burma) (under construction)

- 2001: Expeditions to Namya, Hpakant and then Mogok with Ted and Angelo Themelis and Hemi Englisher (under construction)

Find our blogs using the following Keywords:

     black star sapphire
     Bo Rai
     Dak Nong
     Di Linh
     Fair Trade
     Field Report GIA
     Gemological study
     Ha Long
     Ha Long Bay
     Houay Xai
     Khao Ploy Waen
     Kho Laem Sing
     Kul I Lal
     lead glass filled ruby
     Luc Yen
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     Mong Hsu
     pearl farm
     Phan Thiet
     Quy Chau
     Richard W. Hughes
     Richard Wise
     Sri Lanka
     star ruby
     Yen Bai

Find our photos using the following Keywords:

     Bai Lai
     Ha Long
     Ha Long Bay
     Luc Yen
     Minh Tien
     pearl farm
     star ruby
     Tan Huong
     Thac Ba

Discover fieldgemology newsletter:
(Currently under "hibernation status"...)

Number 01: Sept 2006
(I know: it was long time ago...)



THANKS for their support
for our field expeditions since 2005:


about gems, gemology, field expeditions, studying gemology, minerals, jade, pearls or jewelry?
We recommend these FORUMS
where the author is contributing:

Do you want to

Here are some recommended institutes where the author studied gemology in Thailand ... and was happy about his investment!

For those willing to go further after their gemological studies: Recommended Advanced Gemological Courses:

To finish here are some BOOKS about gemology
the author have read and appreciated and would like to recommend to people willing to learn more about gemstones, gemology and the places where gemstones are found:




Creative Commons License

The photos and articles on are licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Feel free to use the photos and articles with links and credits. No commercial use without permission.
All the best,

May 11th, 2010 | Keywords:mozambique , ruby , treatment , flux , glass Travel |
Blog Title: flux assisted heat treated rubies from Mozambique with partial fissure healing and filling.

May 10th 2010: GIA Laboratory Bangkok a new study on the heat treatment of rubies from Mozambique is now online on


Here is a link to the Mozambique special issue where you can find this study: "FAPFH/GFF Treated Ruby from Mozambique, a preliminary report" by V. Pardieu, N. Sturman, S. Saesaew, G. Du Toit and K. Thirangoon released May 11, 2010.


The ruby deposit in Montepuez was discovered during spring 2009 (see our GIA Mozambique expedition report). Rapidly many rubies from that new location were seen in Bangkok, Thailand. First we saw at GIA Lab Bangkok many unheated rubies but then more and more heated rubies. Unlike rubies from the Niassa deposit that were commonly seen treated using lead glass, these rubies were treated using some flux assisted heat process.


Dont get us wrong: It is not what we can really call a new treatment:


Flux healing using borax and silica is going on for nearly 20 years with rubies from Mong Hsu (Burma) and rubies from other deposits (usually marble type like Vietnam, Afghanistan, Tajikistan, Kenya, Tanzania,...) But the treatment is now performed also on rubies from the new deposit in Montepuez, Mozambique (which is not a marble type deposit). Usually what lab gemologists used to see with flux healed Mong Hsu rubies where healed fissures and sometimes glass filled cavities, but most of the time the stones were cleaned with acid before to be send to the lab and thus there was no glass filled cavities.
The new thing is that most of the flux heated rubies from Mozambique which were submitted to the GIA labs recently in Carlsbad, New York and Bangkok were obviously not cleaned with acid and has some large fissures filled with glass or partially healed and partially filled with glass (as the healing was obviouly far to be complete):


"Glass filled and healed fissure in Mozambique ruby"

On the right part of the photo taken using a microcope under 40x magnification and using dark field illumination, we can see a curved vertical line on the right side of the photo, on the top. It is the area where the fissure reaches the surface of the ruby. Note that this line is continuous. It means that the fissure is not healed. Close to the surface, the fissure is filled and it is possible to see inside the fissure some strait lines that are in fact devitrification features and small round features (in fact gas bubbles). Deeper inside the fissure (on the left side of the photo) we can see some fingerprint like designs first something like honey combs, then something more like a fingerprint design. It is the area deep inside the fissure where some healing was taking place.

Photo: V. Pardieu / GIA Laboratory Bangkok, 2010


To illustrate the fact that we are not really facing a new treatment, it is interesting and useful to remind and study carefully the excellent diagram published in 1998 by Prof. H.A.Hänni (reproduced with permission). Prof. H.A.Hänni was trying to explained what was going on inside these fissures during the flux-assisted heat treatment process:


"Flux assisted healing process by H.A.Hänni (Reproduced with permission)"


It is interesting to see that Prof. Hänny already saw devitrification features in surface reaching lass filled fissures during the 1990's in the case of rubies heated with flux (nothing really new in this treatment then...):


- In "D. after possible devitrification" we can see that the surface reaching area is filled with glass, with gas bubbles and devitrification features (it is exactly what you see on the inclusion photo in this blog) but we can see also that after D, there is E (logic...):


- "E. after cleaning by surface-etching": Flux healed rubies were usually cleaned and the glass was removed before the stones to be released in the market.


This last step in the process was obviously not performed in the case of the stones which were recently submitted at the GIA labs as we saw commonly that glass was still present in some surface reaching fissures. This is the new thing and the issue here:


- If the fissure is healed, then it is closed by recrystalization of ruby (synthetic ruby) and thus the final product is stable.


- Now if it is just filled, the durability of the final product will depend on the durability of the filler...


As such stones with healed and also glass filled fissures were becoming more commonly submitted at the GIA labs, at the end of March 2010, the GIA gemological laboratories in Carlsbad, New York, and Bangkok started to issue reports disclosing clearly the presence of these filled fissures in addition to the healed fissures. The reason is that glass (with lead or without lead) is much less durable than ruby and glass as a filler is likely to get damaged by chemicals, heat or abbrasion dparticularly during the stting or jewelry repairing process.


Thus it is important that the presence of such filler is disclosed to the consumer.


To get more details about this issue and the research we dit at GIA, please read the following report:



Here is a link to the Mozambique special issue where you can find this study: "FAPFH/GFF Treated Ruby from Mozambique, a preliminary report" by V. Pardieu, N. Sturman, S. Saesaew, G. Du Toit and K. Thirangoon released May 11, 2010.


Hoping that you will find all that interesting and useful!


All the best,




February 4th, 2010 | Keywords:glass , star ruby , treatment Travel |
Blog Title: New study on GIA website: Lead glass filled star rubies.

February 02nd 2010: GIA Laboratory Bangkok "Lead Glass Filled Star Rubies" is now online on!

It is a new study about the lead glass filled rubies. This time it is a specific study about lead glass filled star rubies.


"Lead glass filled Star rubies"

A selection of 34 lead glass filled star rubies showing the color range of the new material from pink to red and to near black. The stones presented weight from approximately 1 to 20 carats. The photograph was taken using a slightly diffused natural sunlight in Bangkok, Thailand. The background used is page 17 of “Gemstone Enhancement” by Kurt Nassau (1984).

Photo: V. Pardieu / GIA Laboratory Bangkok, 2010


Recently we were contacted by Mr. Mahiton Thongdeesuk, the burner who allowed me to witness his lead glass treatment process in 2004 in Chanthaburi :


lead glass filled rubies pardieu

lead glass filled rubies McClure

lead glass filled rubies McClure

Here are links to the article "Lead glass filled/repaired rubies" by V. Pardieu, then Director of the AIGS Laboratory in Bangkok published in February 2005 and its 2 updates published in "Gem Market News, a Supplement to The Guide" in July 2006 and September 2006.

This time Mr. Thongdeesuk told us that was about to release in the market some important quantities of lead glass filled star rubies and he would be interested us to study his material and inform the public about it as some stones were very much looking like fine unheated star rubies. So we studied these stones. It was a good occasion to show that gem burners and gemological laboratories like the GIA Laboratory Bangkok can work together. This update will we hope help to inform the market and the final consumer about these stones which if they are not a gemological issue are a serious problem for the trade.


Note about Lead glass filled star rubies: Lead glass filled star rubies are not a completly new thing, if fact the author saw some of them already in 2004 in Bangkok. They were first reported in the gemological literature by the GAAJ on their Jan 2005 update of the lab alert they did about this treatment on April 15th 2004. Recently an interesting study was also published by Thomas Hainschwang in his Gemlab Research Newsletter 06/2009 about lead glass filled star rubies looking quite similar to the lower quality material we saw at Mr. Thongdeesuk office. Is it the material studied by Thomas Hainschwang the same as the stones we studied? Difficult to say as many companies are producing lead glass treated stones nowadays on stones from different origins and using glass of slightly different compositions as the author already explained in his study published in February 2005. In fact there is not one treatment but at least as many treatments as you have companies. Furthermore sometimes the glass used by this or that company for this or that specific customer does not even contain lead but instead it is rich in bismuth or barium creating some terminology issues with the use of "lead glass filled rubies" in the case where lead is not detected. And of course it is clear that the treatment will continue to change as experimentation is still going on.


Summary about the whole "lead glass filled ruby" issue:


On the Gem lab side:

Lead glass filled rubies are very easy to identify for gemological laboratories. They were studied in details and a proper common nomenclature has been established by the gemological laboratories members of the LMHC group to identify them properly:


Here is a link to "A discussion on Ruby-Glass Composites & Their Potential Impact on the Nomenclature in use for Fracture-Filled or Clarity Enhanced stones in General" by K. Scarratt:
"(April 01, 2009), this study about Ruby-Glass Composites was first released as limited LMHC (Laboratory Manual Harmonization Committee) distribution in Feb. 2008)"


Here is a link to the LMHC Information Sheet number 3, presenting the current nomenclature use by the six gemological laboratories members of the LMHC (listed by alphabetical order): CISGEM (Italy), GAAJ Laboratory (Japan), GIA Laboratory (USA), GIT-Gem Testing Laboratory (Thailand), Gübelin Gem Lab (Switzerland), SSEF Swiss Gemmological Institute (Switzerland).


On the market side:

Since 2004 when these stones arrived in mass in the market, many stones were sold without proper disclosure. If it was about heated vs unheated, that would have been without consequences but, unlike traditionaly heated stones, lead glass filled rubies present some serious durability issues:


lead glass filled rubies McClure

Here is a link to the article "Identification and durability of lead glass filled rubies" by S.F. McClure, C.P. Smith, W. Wang, and M. Hall published in Gems & Gemology (Spring 2006)


Many stones were damaged particularly when jewelers were trying to use them in jewelry like if they were normal rubies. As the lead rich glass filling the fissures and the cavities can easily be damaged by chemicals like acids or caustic soda, by the heat of a jeweler torch and is also very brittle, many stones were severely damaged in the process. In consuming countries particularly where people are less aware of treatments, people feel to have been cheated. It created a bad name for the product.

Nevertheless as Tom Chatham said: “Gems do not cheat people, people cheat people”.

Sadly very often people buying or selling gemstones do not have enough gemological training to identify properly the stones they deal with. When in addition to that the stones are bought or sold without being properly identified by a gemological laboratory and without proper disclosure then this might not be without some serious consequences for the final customer and the trade when the stone present some durability problems like it is the case with filled gemstones.


That's the whole issue.


With proper disclosure and appropriate pricing, this material has its place in the market for the budget minded buyer who will never be able to afford unheated or traditional heated rubies. With lead glass filled rubies in fact such buyers have now an alternative to synthetics and imitations. Complete and accurate disclosure is the key to protect the buyer, and to build a healthy industry. So what to do?

Some people suggest that we should stigmatize this treatment and change the nomenclature on lab reports. Well, to the author understanding, the issue is not with the stones properly identified by gem labs, it is with the others. So changing the name on lab reports will not solve the trade problem, instead in the author opinion it might just add confusion. So in this case why to put all the gemological terminalogy upside down and take the risk to have a global confusion if it will not solve the main issue for the trade?


In the author opinion the terminology adopted by the gemological laboratories members of the LMHC and presented in the LMHC Information Sheet Number 3 is perfectly adapted to the current situation. With this this solid nomenclautre, what can lab gemologist do more to help the trade in this issue? Probably do our best to inform people about the treatment, publish informative studies like those the author recommend on this blog, remind people willing to buy gemstones that learning gemology can be useful, and if they don't want or cannot, then remind them that there are gemological laboratories who can do the identification work for them.


Hoping that you will find all that interesting and useful!

All the best,




Important Note: Vincent Pardieu is an employee of GIA (Gemological Institute of America) Laboratory Bangkok since Dec 2008. Any views expressed on this website - and in particular any views expressed by Vincent Pardieu - are the authors' opinions and do not necessarily reflect the opinions of GIA or GIA Laboratory Bangkok. GIA takes no responsibility and assumes no liability for any content on this website nor is GIA liable for any mistakes or omissions you may encounter. GIA is in particular not screening, editing or monitoring the content on this website and has no possibility to remove, screen or edit any content.