I don't think I see this article posted on PG yet http://www.jckonline.com/2010/05/25/pearls
Cut and paste below:
This story appears in the June 2010 issue of JCK Magazine.
Three years ago, metallic-skinned Chinese freshwater pearls began appearing in mixed-color strands at major international trade shows. Since then, the tissue-nucleated pearls have been popping up with increasing frequency, ranging in shape and size from baroques to perfect rounds between 6 and 13 mm. Jeremy Shepherd, owner of *PearlParadise.com, collected whatever he could find in China in 2007 and introduced a line of mixed metallic strands by the end of that year. As more pearls became available, Shepherd reintroduced the strands in perfect rounds and soon, other pearlers followed.
The reason behind the metallic colors is not completely clear, but pearl experts say they could be the result of byproducts from newer Chinese hybrid shells—a combination of Hyriopsis cumingi and Hyriopsis schlegeli mussels—cultivated originally for Fireball pearls. According to Shepherd, the metallic colors are more exotic than typical natural-color pearls in lavender and pink, and the luster exceeds that of many Japanese akoyas. Shepherd recently spent two weeks in Asia talking to growers about metallics. Availability is still somewhat limited—Shepherd found just 25 pearls in 30 kilos (about 1,000 strands) while shopping one farmer’s inventory from the same harvest. “They still only make up one-hundredth of 1 percent of total production,” he says. —Blaire Beavers