They have great luster, great roundness, and great color. Compare the three pearls shown above right to a strand of natural-color Australian South Sea bead-nucleated golds (top), and you’ll be hard-pressed to tell them apart. So what are they?

“They’re dyed Chinese freshwaters,” says Tetsuo Maruyama, managing director for C. Link International, Tokyo. They’re undrilled golden Chinese freshwater tissue-nucleated pearls. How they’ve been dyed is a mystery. “I was told that it takes about three months,” Maruyama says.

“If you look closely at the images, you can see a reddish overtone on the periphery, particularly on the right pearl but also on the center pearl [the bottom part]. This looks very much like the appearance on some of the ‘golden’ South Sea pearls that we identified as dyed cultured pearls,” notes Karin Hurwit, pearl expert, formerly with GIA’s Gem Laboratory. She confronted the mystery in a Lab Note written for Gems & Gemology in 2002, but she couldn’t solve it either. (The pearls Hurwit examined did show distinct yellow/green fluorescence under long-wave radiation, also proving those were treated.)

“I am not sure exactly [how it’s done] as most of the treatments are not 100 percent explained,” says Gina Latendresse, American Pearl Co., Nashville, Tenn. “However, I have suspected that the undrilled golden colors are from an organic dye, which is more likely to penetrate the layers. My father visited the processing offices many times in his 50 years of travel, and he said it was not unusual that the treatments would take as long as three months.”

“There are so many trade secrets,” says Hurwit. “What we do know, though, is that you can easily dye drilled and undrilled pearls by immersing them for some time into either organic or inorganic solutions.”