About Us



Established in Bangkok in 2017, the Institute of Gem Trading offers gemological courses based on decades of experience in mining, cutting, and gem trading. Through our modular short courses, you will learn the skills of the modern professional field gemologists such as grading rough colored gemstones, cutting and recutting gems in order to maximize values, as well as mastering the trade secrets of the colored gemstones market. With a hands-on approach, students will learn through lectures, videos, interactive demonstrations, sample specimens, workshops, field trips, and seminars by industry leaders.

about image why-section
about image why-section

Why Choose Us?

The Missing Link in Gem Training

Utilizing our experience in various aspects of the gem trade, we have designed courses to teach all the needed knowledge from mine to market; how to examine gem rough, cut them into valuable and saleable gemstones, and find success in the international gemstone trade.

A Hands On Method

IGT gives its students the ability to gain practical knowledge through the use of natural gemstones. We house a world-class gemstone library for use in the classroom and we teach our students how to use gemological tools to analyze them.

Professional Network and Knowledge

Our courses reveal many previously guarded trade secrets and we teach skills that are usually unavailable outside of a family-run gemstone business or a long-term traditional apprenticeship.

The Modular Approach

Whether you would prefer to visit Bangkok for a week to expand your knowledge or immerse yourself in the full month educational training program that we offer, IGT's modular courses can accommodate your needs.

Meet The Team

Our team and founders are passionate communicators with years of first-hand experience in the gem trade.

Justin K Prim

Faceting Instructor

Justin K Prim is an American gem cutter and author. He has been cutting gemstones since 2013 and has trained as a lapidary in the United States, Thailand, Sri Lanka, and Switzerland.To support his work as a gem cutter, he has attended gemology programs at GIA and AIGS. He has travelled around the world to various gem producing regions to learn more about rough, and has visited mines in Thailand, Cambodia, Europe, and the Americas.


Before joining IGT, Justin was teaching Gemology courses at AIGS Bangkok.He is currently working on a book about the regional histories of colored gemstone faceting and regularly travels around the world researching lapidary history. Aside from teaching and writing, Justin also gives talks and presentations about faceting and faceting history.

Kamila Guerchouche

Assistant Marketing Manager

Kamila grew up in the gem trade, surrounded by gemstones since her childhood.  Her father is a gem buyer, so she learned the ways of a family-run gemstone business from the inside. Kamila has lived between Thailand and France and she is fluent in Thai, French, and English. After completing a diploma in Paris, she returned to Bangkok and joined the IGT team.


Kamila has a love for people and communication and has worked on various socially-oriented projects and events in both Thailand and France. These skills make her the perfect fit to handle IGT’s marketing and social media needs. She will be the voice responding to your emails and social media questions.

Jayesh Patel

Gemology Instructor

Jayesh is an Accredited Gemologist born in Mogok, Burma, with an accumulated 40 years of experience in the gemstone trade, including many years spent as a  gemological instructor and lab manager at AIGS. Jayesh brings his gemological expertise, sophisticated market knowledge, and extensive gem trade network contacts to IGT’s educational program.


Aside from teaching, Jayesh is engaged in trade with local gem businesses in Myanmar, Thailand, Mozambique, and India for Rubies, Sapphires, Spinels, and also Diamonds. He manages a consistent flow of stones coming from mines into the trading market as well as maintaining an extensive network of contacts with suppliers, buyers, and facilitators from all over Asia and Europe.

Sangwantip Pituk (Fon)

Executive Secretary

Fon has a diverse background in the customer service industry.  She was the executive secretary for the head office of Harvest Property for many years. She worked as the sales manager for Bangkok First Aid and has also done sales and acted as a tour guide for diving companies in the Thai islands. Fon also makes jewelry as a hobby and has enjoyed learning to cut gemstones in IGT’s cutting class that she can use for her jewelry creations.


Fon brings her diverse skillset to IGT, helping us grow our customer base, handling administrative duties, and explore the various avenues of marketing. Fon also handles our Line and WhatsApp communications so if you contact us in those ways be sure to say hi!

Sarath Chandrasiri

Faceting Instructor

Sarath is a master gemcutter from Sri Lanka with over 30 years of experience. For the last 17 years he has been the head faceter for the Yavorskyy company was part of the original gem cutting team for Yavorskyy’s cutting factory in the early 1990’s.


Sarath regularly travels between Bangkok and Sri Lanka, doing work for clients all over the world.  His specialty is faceting large stones, having cut everything from sapphire to tanzanite to tourmalines and everything in between.


Sarath has worked in all parts of the gem cutting industry. Over the years, he has worked with several factories to produce his own cutting machines and his own laps which he has sold in Sri Lanka and also imported to Bangkok.  Sarath brings many decades of cutting mastery to the IGT cutting class and hopes to impart his wisdom onto our students.

Mariaveronica Favoroso

Managing Director

Mariaveronica Favoroso Ressigeac is a former corporate lawyer who, during her 5 years in China, changed her career to become a strategy consultant specializing in luxury. She later moved to London where she worked for Fabergé and then for its parent company, Gemfields, as Head of Business Development for China.


Co-founder of Ressigeac Gems, she in charge of the commercial side of the business whilst co-developing new CSR and traceability projects, alongside with running her own company in Hong Kong, based on Educational and Special events. After reading an MBA in London, she is now completing her Graduate Gemmologist Degree with GIA.

Karim Guerchouche


Karim has been working in the gemstone industry since 1988. He started a cutting factory in Chanthaburi that specializes in Swiss-Quality precision gem cutting for the watch industry. His area of expertise is in the treatment of various types of gemstones.  Through various collaborations with major mining companies and gem labs, along with years of experimenting, Karim has developed his own heat treatment techniques for Ruby, Sapphire, Spinel, and more.


Karim has bought gems in many countries around the world, including Burma, India, Pakistan, Madagascar, Mozambique, Tanzania and he’s now a Gemfields Authorised auction Partner.


Philippe Ressigeac


Philippe’s main area of expertise is in rough gemstones. By living in key mining and manufacturing hubs such as Burma and Thailand, and travelling extensively in various countries such as Vietnam, Madagascar, Mozambique, and Burma, collecting specimens, he has acquired a vast knowledge of gem cutting and grading.


In Madagascar, he worked for 3 years with a Swiss partner in Sapphire mining and cutting and also co-founded a jewelery retail business in the country. In Mozambique, he worked for 3 years with Gemfields at Montepuez Ruby Mine, where he co-developed their proprietary Ruby grading system and Ruby auctions. After leaving Gemfields, he acted as a consultant and created the Gemfields Masterclass educational program, which has run worldwide since September 2016 with hundreds of students in attendance. Philippe is a Gemfields Authorised auction Partner.

Laurent Peter


Laurent Peter studied business at the University of Geneva (HEC). After graduation, he worked for 20 years in various banks in Geneva, acquiring detailed knowledge of banking business and project management in specific areas such as trading, risk management, and procurement of IT solutions and their financial information – from the user’s needs definition to the solution deployment.


Seven years ago, he opted for a new start in the gemstones business. He attended AIGS to acquire knowledge of the gemology industry and in 2012, he set up a trading company in Switzerland focused on the Swiss Watch Industry. In parallel, he set up a lapidary factory in Sri Lanka which today counts over 35 specialized employees. In 2017, with a partner, he opened a gemstones trading company dedicated to the jewellery Industry in Bangkok.

Our Institute

Thanks to its strategic position in the heart of the Bangkok’s gem district, Institute of Gem Trading provides the perfect environment for students to learn new gemological skills in.

Have Questions?

Feel free to contact us with any questions you might have about IGT and its courses.

Contact Us