Jeffery Bergman, a gemstone expert based in Thailand, has issued a warning for retailers and consumers to be aware of inexpensive topaz being sold with what he terms a “color-stability problem.”

“In the last few months we have seen a significant increase in the volume of orangey to reddish to pinkish brown precious topaz on the market in Thailand,” Bergman said in an e-mail to members of the jewelry industry. “Some dealers represent these gems as Burmese, others Brazilian. In Chanthaburi [Thailand] they are available for as little as $1/ct. Unfortunately, there are already several Thai-based dealers selling them to unsuspecting consumers on eBay with no disclosure of the color-stability problem.”

Bergman continued: “I recently acquired three samples from a Chanthaburi dealer, one 18.00 ct., one 22.00 ct., and one36.00 ct. All exhibited a lovely classic strong orangey ‘sherry’ color on the ends of the stone, and a medium slightly orangey brown in the belly. I do not yet know the origin of the color in these highly unstable gems, but upon exposure to direct sunlight for one day, they fade to near colorless.”

To illustrate his point, Bergman, founder of Primagem in Bangkok, Thailand, a natural gemstones and jewelry dealer, included a photograph that shows two stones side by side. The first stone shows the color before exposure to sunlight, and the second shows the color after exposure to sunlight.

He concluded: “It is important these gems are not sold to unsuspecting consumers, as this further erodes confidence in our already fragile industry.”