Field Report

Venture into Chanthaburi’s Sapphire Mines and Markets with GIA’s Field Gemologists

GIA Staff
October 23, 2015

A Visit to Chanthaburi, Thailand

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Visit Thailand’s resurgent mines and gem markets with GIA field gemologists.


This video takes you to a sapphire mine in eastern Thailand and to Chanthaburi’s bustling gem market, with a team led by GIA Field Gemologist Vincent Pardieu.

Only a few hours from Bangkok, the area provides easy access for collecting reference samples and witnessing the evolution of the area’s mining and trading activity. It’s also an ideal expedition for training and evaluating young gemologists seeking to join GIA’s Field Gemology department.

In this video, you’ll travel to the Khao Ploy Waen volcano, which is at the center of the sapphire-producing area. Its name literally means “hill of gems.” The volcano is about four miles (6.5 km) west of Chanthaburi, a gem-trading center a little over three-hours’ drive—some 155 miles (250 km)—southeast of Thailand’s capital city, Bangkok.

Eastern Thailand was the world’s major ruby source between the early 1960s and the 1990s, when political issues in Myanmar (then Burma) shut down supply from that country. This spurred big, mechanized mining operations in eastern Thailand.

Although the rubies are mostly gone, this area has lately seen a resurgence in sapphire mining, and Khao Ploy Waen still resounds to the rush of water and the clatter of concentrate through alluvial miners’ sluices, jigs, and trommels. The area produces some big dark blue silky stones—which require treatment to be marketable—along with green material and the locally prized yellow color sapphires locally called "Butsarakam". Top-quality yellow, green and blue gems sometimes have excellent transparency but strong dichroism, Pardieu explains.

Decades at the center of corundum supply helped cement Chanthaburi’s status as a premier gem trading and treatment center. A cosmopolitan place, Chanthaburi blends Chinese, Vietnamese, and French influences. The town also hosts Thailand’s largest Christian church, the Cathedral of the Immaculate Conception.

The town’s weekend gem market has an international flavor. Every Friday and Saturday, traders from all over the world come to buy and sell rough and cut gems. This is important because local merchants have come to depend on their merchandise. Traders from Guinea, Africa, are especially evident, with their selections of gems from African sources including Mozambique, Tanzania, Nigeria, and Madagascar.  This mix is demonstrated by a Buddha carving fashioned from African ruby that, Pardieu explains, required heating with borax to close fractures before it could be fashioned: Truly a blend of local treatment and fashioning knowhow with raw material sourced a continent away.

Chanthaburi’s market would be much less active without this influx of traders and their stones. Indeed, in one ironic twist, a trader from Kabul, Afghanistan, was seen purchasing Nigerian rhodolite garnet, treated ruby, and synthetic gems for sale to US servicemen in military bases like Bagram and Kabul.

This GIA Field Expedition (FE53) took place in June 2014. Besides Pardieu, the participants were cameramen Didier Gruel and Philippe Brunot, and expedition members Victoria Raynaud, Stanislas Detroyat, and Marie Daufresne.

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