Gemstones & Pearls:Gemology
China produces hundreds of tons of cultured freshwater pearls every
year. Some categories are getting better all the time
China has made enormous strides in freshwater pearl culture in the past
two decades. Once scorned as "rice krispies" because of their
irregular and elongated appearance, Chinese freshwater pearls have been
moving steadily toward rounder shapes, smoother surfaces and bigger sizes.
The natural-color cultured freshwater pearls shown below are a case in
point. However, they are by no means abundant, requiring months or even
years of collecting for a multistrand necklace, says retailer Michael Randall
of Gem Reflections, San Anselmo, CA. But because of their unusual colors,
lush appearance and luster, Randall has decided to carry this type of Chinese
How They Form
Randall is intrigued also by how they form. They are sold as non-nucleated
cultured pearls because they don't have the nucleus bead traditionally found
in cultured pearls. Instead, they have a cross-section similar to that of
pearls that grow naturally, with concentric layers of nacre. No study has
fully documented this type of formation. However, the Summer 1994 issue
of Gems & Gemology, the quarterly journal of the Gemological
Institute of America, referred to them as "tissue nucleated."
"With the tremendous and still increasing production of freshwater
tissue nucleated cultured pearls, and the greater attention to quality by
cultured-pearl farmers in China, it is not surprising that some of these
cultured pearls turn out nearly round or round," the article states.
Similarly, in her book The Pearl Book, The Definitive Buying Guide, Antoinette
Matlins says: "While the exact technique used to produce these beauties
is not known, we do know it involves implanting a round all-nacre nucleus
perhaps made from a non-nucleated freshwater cultured pearl such as the
inexpensive tissue graft rice-krispie type, shaped into round beads after
harvesting and then re-implanted in another freshwater mollusk."
The pearls are slightly out-of-round, says Randall, but are a vast improvement
over the "potato" pearls (so named because of their shape) that
represented the Chinese growers' first step toward "rounding"
in the early 1990s.
Today, the pearls grow as large as 10mm to 11.5mm, compared with 6.5mm
to 7mm when the GIA report was published five years ago.
The pearls' natural colors include lavender, pink, orange, gold and gray,
though pure white and cream are more common. The origin of the color remains
a mystery. (China also produces vast quantities of pearls that are irradiated,
dyed or both to achieve the same colors. See Professional Jeweler,
September 1998, pp. 125-126.) You can detect dye in color concentrations
on the pearl's surface (especially around the drill hole), but experts say
irradiation can be very hard to detect. For this reason, a definitive determination
of color origin may need to take place in an accredited gem lab.
A Chinese freshwater cultured pearl cross-section reveals concentric
layers of nacre growth reminiscent of natural pearls. But the process of
producing these pearls is a well-kept secret. Pearl courtesy of Gem Reflections
of California, San Anselmo, CA.
A strand of 10mm to 11.5mm cultured freshwater pearls from China blends
an array of natural pastel colors. Pearls courtesy of Gem Reflections of
California, San Anselmo, CA.
photos by Robert Weldon
by Robert Weldon, G.G.
Copyright © 1998 by Bond Communications.