Some gemology, business presentation: supply of rough and faceted gemstones, jewelry manufacturer in Thailand.


Yannick Mandaba

Yannick Mandaba
Speaks French (mother tongue), English, and some Thai.

Graduate Gemmologist-HRD (Anvers, Belgique)
D.U.G (Nantes University Diploma in Gemology, France)
Asian Institute of Gemmological Sciences (Bangkok, Thailand)

Main Occupation: Custom Jewelry Manufacturer, and production of lines of jewelry for boutique stores and brands.

As a gemmologist:
I have the chance, through my work in jewelry manufaturing and through my studies, colleagues gemologists, laboratory researchers and gem dealers, to see beautiful gemstones. If you are looking for something specific do not hesitate to contact me.

Business Development:
I am also interested in any venture in relation with
- Commodities and Ressources from central africa (gold, diamonds, certified wood).

- Customer Service person for jewelry manufacturing
(speaking english, thai would be a plus).
Job description: New inquiries, gather all required info, create products files and present to pricing section, return quotes, take orders, give order status to customers. Knowledge in gemstones or jewelry is required. Part time job possible for students in Gemological School in Bangkok (AIGS or GIA students are welcome)
- Full time position is also available after 3 months to 6 months training/probation time depending knowledge in jewelry manufacturing.


Fabrication de bijouterie en thailande

Custom Jewelry Manufacturing in Thailand

Manja Thai Co., Ltd,
50/31, Pan Road, Silom,
Bangrak, Bangkok 10500,Thailand
Tel: +66 2635 0858
Fax: +66 2635 0859




Education in Gemology

Membership :
- Graduate's Club (HRD)
- Gemological Research Center (CRG, Université de Nantes)

Publications :

- Article in the scientific magazine of the French Gemological Association (AFG):
E. Fritsch, JP. Gauthier, Y. Mandaba, F. Mazzero (2004) L'opale d'Ethiopie : gemmologie ordinaire et caractéristiques exceptionnelles, Revue de gemmologie AFG n° 149


DUG Thesis (University Diploma of Gemology, Nantes University):

Opals from Ethiopia
(List of DUG prresented at Nantes University )

Opal from Ethiopia - Ethiopian Opal

Comparison of the Opals of Ethiopia with other Volcanic Opals and with sedimentary opals:
- Description on the level of the structure with thanks to the electronic imagery.
- Confrontation of the the X-rays method with that of the Raman probe. They both show the rate of crystallization (information on the geological origin). But identification of the geographical origin can be possible with the probe Raman (geographical signature for an area and sometimes for a given deposit). Mainly qualitative, but very illustrative studies on the methods of gemstones analysis and the type of information to be extracted.

Research Director: Professor Emmanuel Fritsch
Samples provided by: GEMOA SARL

Education (in French) :


Pictures from a trip to Cambodia:

Heat Treatment for sapphires in Pailin, Cambodia

Mining, heating and cutting in Pailin city

Trip to Arusha, Tanzania:

Tsavorite from Saul mine in Tanzania

The Saul brothers' Tsavorite Mine


Starting in Thailand


Cutting Factory in Bangkok
We still use their services if necessary, good work but not cheap at all...
(1st January 2006).

I have been part of this company since January 2006, to take care of international customer relations, but have lent a hand for the supplies.
I have begun my integration by implementing a quotation system which uses forms linked to a quotations database, allowing us to answer more swiftly to the customers' demands, and control our pricing.

Gemstone Cutting Factory in Bangkok Index cutting machine
Gems & Jewelry Show... "Index", precision hand cutting Machine

Thus this cutting factory is working mainly on the local market's rough stones, but also with those directly imported from other countries from Asia, the Middle East and Africa.

This workshop's specialties are difficult and unusual cutting solutions:

- Highly precise cuts (0.03 mm) by hand, using the index (semi-industrial).

- "Cut to fit" to perfectly fit the customer's setting.

- Fancy cuts: The available equipment allows the production of calibrated sizes in fancy faceting, which allows easy setting and fashionable designs.

- Special operations: Concave cut, driling, carving, etc...

- Automated computer guided cutting machines, thanks to the developments of the Corean engineer.

Automated cutting machine cutting machine, 12 stones at a time!
Kiwong, engineer. 12 stones in a row! Computer guided machine (works with GemCad software)

Swala Gems Trader, Mine de Tsavorite , à Arusha, Tanzania
(Octobre 2005 - Fevrier 2006)

The goal of this mission for the Saul brothers was to set up the exportation and retail of cut stones, allowing this mining company to increase their income while maintaining the same productivity.

Eric Saul holding a huge Tanzanite rough stone Eric Saul checking the JIG for tsavorite garnets
Eric Saul, underground,holding a huge Tanzanite
(Photo Patrick Voillot)
Marc Saul, check the concentration of Tsavorite Garnet in order to tweak the engine frequency of the gig.
(Photo Yannick)

The most beautiful stones are then cut and sold to individuals:
- At the Swala Gem Traders Shop in the renowned "New Arusha Hotel".
- On the site; stones under a certain value being stored in and shipped from Bangkok for delivery costs reasons.

My task was to conceive the site (Structure and Design), direct its construction. I am still taking care of the technical support and on-going developments.

I then went to Tanzania for a month, allowing me to prepare the contents of the site (articles, images and structure), visit the mine, the buying office and the shop, but, more importantly, to accurately measure the different possibilities offered for establishing a photographic studio, delivery options in Arusha and Bangkok, workload repartition, etc.
Finally Eric Saul decided to start with sending the stones directly from Arusha, but the possibility of managing a few warehouses is still available in the website's customized administration tool.

During the week, I have been working on the website and the photographic studio, and I was spending the weekends in the mining area with Marc Saul whose house there sits on the only hill, squarely at the center of that circus-shaped valley.

The Saul tsavorite Mine The Saul tsavorite Mine
The Saul's little House at the mine dominnating a magnificent "U" shaped valley . Marc is able to embrass his entire domain in a single sight.
(Photo Yannick)
Water, so rare in this part of the world, is an essential element of the mining process . Here Marc is supervising the operation of transvasing the water in another reservoir in order to clean this one from the mud and continue washing the gravels.
(Photo Yannick)

The Saul tsavorite Mine

This was a very rewarding experience, as much for hands-on gemology and discovery of eastern Africa as for the e-trade and unusual logistics involved because of the isolation of the area from where cut stones are directly sent to customers.

Dr. John Saul's discoveries john Saul Ruby MineThe John Saul Ruby Mine
  Tanzanite, sky Blus ZoisiteTanzanite, the Sky Blue Zoisite
  Color Change GarnetThe first Color-Change Garnet
Gemstones of East-Africa Gemstones of East AfricaFirst Gemstones of East-Africa
  Rift Valley, East AfricaGeological Context of East-Africa



AIGS Laboratory &
(October 2004 - Juin 2005)

   As soon as I arrived in Bangkok, right after having my knowledge on Stone from South Asia and new treatments updated at the A.I.G.S. School, I have been assisting Vincent Pardieu (Director of the Asian Institute of Gemological Sciences Laboratory: AIGS) in his research on the origin determination of corundums. An obsticle laboratories have been trying to overcome is determining origin of corundums for use on their certificates. With current technology origin determination is still a developing science.
But quickly I started to be attracted by the possibilities of the local market for more commercial activities, a chance to pratice the most exciting part of working with gemstones.

AIGS Laboratory for gemstones certificates establishment in Bangkok
Vincent Pardieu,
Ex-Director of AIGS Laboratory,
now working for Gubelin Laboratory

     My knowledge in computers and web hosting led me to become manager of a leading distributer of gemstones over the net. GemWow is a portal that helps Jewelers from Thailand, Laos and Vietnam reach customers all over the world with little worry for maintainance, shipping, insurrance or a plethora of other administrative details. The website goal was to offer gem dealers the oppertunity to manage their own internet based shops from any workstation allowing them to add products, modify prices and descriptions, follow actions, and reply to customers' questions and offers.

Vincent Pardieuis now working for Gubelin Laboratory in Switzerland, continuing his researches on gemstones deposits all around the world.
Oups, Vincent is now (2009) working at G.I.A. in the research section, updating their database to prepare the certification of origin for gemstones around...2012 something like that. Good luck with that Vince!


Personnal Notes:

I was born from a French mother and an African father. I was born in France and raised in Africa.
My family has nothing to do with gems or jewelry besides the fact that my father used to participate into a mining company in C.A.R. with an Italian group as a local investor.

My mother is a fine pediatrician rewarded by the "French Medal of Merite" for taking care of French citizens babies in Central African Republic, as well as her support to the local population.

My father, the professor Jean-Luc Mandaba did a lot for health, democracy and sport in Central African Republic (Amnesty International Award).
Professor in Pediatric Surgery and sport lover, he finally gave his life to make this former French colony a real nation and a real democracy, but was poorly rewarded. He helped the president Ange-Felix Patasse to access his position at the head of the country, using the support of France and his numerous contacts in political circles (that he kept from his studies in the Medical University of Paris and his active political background in France as a student). He was even the first Prime Minister of this fragile Presidency coming right after 14 years of military dictatorship. After loosing his illusions about his friend the president and especially the president's abusive family, he decided to run for the next presidential elections as an independent candidate. Unfortunately that day never came.

I owe my interest in this field to him and to his advise, when I was not really happy studying computer ingeneering, to consider coming back to natural Sciences, geology, diamonds that are beautiful in C.A.R. This plan being no longer possible, I was finally brought to Thailand seeking for a laboratory job. Then I went into the gems cutting industrie for the knowledge and for a better situation as well, and I finally fixed my activity on jewelry, the real destiny for all stones, the most creative part.

Resume (french): Professor Jean-Luc Mandaba Achievements



Laboratories & schools Forums & Networks Knowledge Associations (D.U.G. France) (GUBELIN) (ICA) (A.I.G.S.) (AGTA) (D-Gem-G) (GIA) (TGJTA) (GRS) Others (SSEF) (Profile) (HRD) (IGI)  

Websites about Gemstones Websites selling Gemstones as well
Some gemology and Jewelry
Dr. Claudio Cardella, G.G. (GIA)


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