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PEARLS: natural, cultured and imitation
D.E. Conklin
INTRODUCTION
Natural pearls are formed when epithelial cells, which secrete a coating of thin concentric layers
of mother-of-pearl material called “nacre”, surround an irritant in the mantle of a mollusk. It is
estimated that only 1 natural pearl will be found in every 2,000 pearl oysters. Often the complex
will be attached to the shell on one side producing half round pearls called “mabes” (mah-bays).
The nacre is a combination of calcium carbonate in a crystalline form called aragonite
(pronounced a-rag-a-nite) bound in a protein called conchiolin (pronounced kong-ki-a-lin) plus
some trapped water. The nacre reflects the light in such a way to give a soft luster or “orient.”
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NATURAL PEARL FISHERIES
Source
Color, quality/size
Saltwater pearls – oysters, genus Pinctata
Persian gulf (Kuwait - Bahrain)
India and the Gulf of Mannar (Sri Lanka)
Red Sea (Saudi Arabian shores)
Creamy white, average quality & size
N/NW Australian coasts
Silver to golden white, dense, large (up to 18 mm)
South Seas Islands
White or black, usually large
Margarita Island (Venezuela)
Translucent white, small
Gulf of California and Pacific coast of Mexico
Metallic hues, black, often irregular shape
Japan, China and Korea
White
White, fine quality, small (~ 7.5 mm)
Other marine mollusks – various species
Giant clam - Indian ocean
Conch - West Indies/Florida coast
White, non-nacreous, large
Distinct pink, non-nacreous
Abalone - California, Japan, New Zealand
Mabes with brilliant green, blue & yellow hues
Pearly nautilus -Australian waters
Yellow, very uncommon
Freshwater pearls
Japan mussel Hyriopsis schlegeli
Rivers & lakes of America, Scotland, France, Sweden,
Russia, China
Freshwater pearls with a pink tint
Mussel pearls with a more subdued orient than saltwater
oyster pearls. Consequently, freshwater pearls are of
less value.
FAUX (pronounced foe) PEARLS
1600’s -
Parisian rosary maker, Jacquin - imitation pearls - hollow glass beads, coated
inside with essence d’orient, the iridescence substance (guanine) from fish scales,
then the beads filled with wax. Servants after royal balls would go around
looking for pearls and stomp on them to determine which were real.
Today -
The finest faux pearls today are made on the Spanish Island of Majorca
(pronouced “ma jor ka”). Solid glass beads are repeatedly dipped in essence
d’oreint. Each layer is carefully polished and when finished covered by a
protective layer. Majorca S.A. produces some 2.5 million strands of pearls
annually. Barbara Bush’s famous strand was a Majorca product (Joyce and
Addison 1993).
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CULTURED OYSTER (SEAWATER) PEARLS – INDUSTRY ANALYSIS
History and Infrastructure
Fifth century
Chinese inserted images of Buddha between the mantle and shell of
freshwater mussels to coat them with nacre (Joyce and Addison 1993)
The pearl king, Kokichi Mikimoto
1858 - Mikimoto born, son of a noodle peddler; (Commodore Perry had
opened trade with Japan only five years earlier) Mikimoto died in 1954 at the age of 96.
1893 - Mikimoto, produced half-pearls or "mabes" (pronounced "mahbays") in oysters.
1896 - Mikimoto's wife Ume dies.
1903 - Tatsuhei Mise, a teenage carpenter and Tokichi Nishikawa, a marine biologist developed
a method to produced cultured round pearls. A fragment of the mantle from a
donor oyster together with nuclei was inserted into a host oyster to produce the
round pearl.
1905 - Red tide destroyed much of Mikimoto’s production (saved 150,000 of 1,000,000 oysters)
and the first round pearls.
1919 - Mikimoto adopted and perfected the Mise/Nishikawa technique and worked over the next
three decades to promote cultured pearls.
One of the major problems Mikimoto overcame was finding the right nuclei. The
ideal nucleus; a substance of appropriate density that would not be routinely
rejected by the oyster and also undetectable under the thin layers of nacre, was
found to be polished beads cut from oyster shell.
1922 - First cultured pearls appear on the international market.
1926 - Mikimoto travels to the U.S. and meets Edison.
More importantly, he found an important source of large nuclei. The "pig toe" or
"washboard" freshwater mussels of the Mississippi River basin, are large mussels
weighing up to seven pounds. The thick shells of these mussels can provide
beads from a few millimeters in size up to 14 millimeters. Annual US export of
mussel shell is about 11,000 mt/year. Mussel bead prices run from $ 3,200/kg for
average beads (< 13 mm) to $ 14,000/kg for top of the line 17 mm beads.
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1930s -
The most important source of natural pearls has always been the Arabian Gulf.
The Arabian Gulf (formerly referred to as the Persian Gulf) roughly 600 miles
long by 100 miles wide and encircled by Iran, Kuwait, Saudi Arabia and the
United Arab Emirates, furnished about 80% of the world production of natural
pearls. Annual catch for the Gulf was estimated to be around 35,000 tons of the
oyster, Pinctada radiata. Thriving from historic times until the 1930s, the pearl
fishery of the gulf declined steadily from 1930 onwards. The decline was due to
first to a world recession, then the introduction of Japanese cultured pearls, and
finally the development of oil production in the region in the 1940s that siphoned
off the labor force.
1933 - Mikimoto burns 750,000 inferior pearls.
1942 - Production of luxury goods, including pearls, stopped during WWII
1953 - The Japanese government establishes its "diamond" (national jewel) policy
•
pearl cultivating techniques shall remain secret to all but the Japanese.
•
production objectives shall be controlled and regulated to safeguard the
home pearl production
•
all pearl production shall be exported to Japan for marketing.
1980s - Australian and French Polynesian pearl culture industries develop and begin marketing
pearls.
1994 - Pearls '94 (May 14 - 19, 1994) Honolulu, Hawaii
Species
While a host of molluscan species can form pearls (both round and mabes) the three species of
"pearl oysters" used to produce cultured round pearls are all in the genus Pinctada. This genus is
characterized by a long straight hinge, with the long axis of the shell at right angles to the hinge.
They are distributed throughout the Indo-Pacific region. The taxonomy of Pinctada was
confused until the definitive revision of Hynd (1955).
•
Pinctada fucata – The Japanese Akoya pearl oyster, often referred to as
simply as the pearl oyster, it is the major pearl producing species used in
Japan, China and Korea.
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P. maxima - The silver or golden lipped oyster, it is used in Australia,
Burma, Indonesia, and the Philippines. It is the produces the largest round
pearls (up to 18 mm in diameter)
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•
P. margaritifera - The blacklip oyster, it is cultured in Tahiti, Fiji, as well
as Japan. Cultured pearls produced from this species are steel-black but in
nature they can either be black or white.
All of the pearl oyster species grow best at sub-tidal depths; 10 - 80 m and have a strong
preference for hard substrates. Salinity optima is fairly narrow, 27 - 34 ppt. and these species do
best in pollution-free waters in areas with reasonably strong currents.
Temperature preference for P. maxima and P. margaritifera is about the same, 23 - 32oC while
P. fucata has a lower range, 10 - 25oC. Colder temperatures reduce growth and nacre deposition
as well as making them more susceptible to disease.
Management strategy
Traditionally, pearl oysters have been obtained by natural spatfall. Natural spatfall for P.
margaritifera is heaviest about 1 month after the high annual water temperature October and
November. Spat is collected on spat collectors placed in the upper 1 - 2 m of the water column.
P. margaritifera spat can be identified when they are about 1 cm in size. In contrast to other
species they have a predominantly green color.
Hatchery production throughout the pearl industry is becoming more widespread. Hatcheries
now provide a large proportion of the P. fucata in Japan. Private and government hatchery work
has begun with P. maxima and P. margaritifera. While details are largely proprietary, they are
undoubtedly similar to those developed for the Pacific oyster. Larval stages are the same as
other oysters with the larval period for P. margaritifera taking about 22 days to metamorphosis
and settlement. Pearl oyster attach to the substrate by byssal threads.
Initial grow-out - Culture pearl oysters are typically grown in mesh rearing structures (see
Figure 1). Mesh is cleaned regularly (every 6 weeks or more often in the summer) and the
density gradually reduced. Mature (1 - 2 years old) oysters (P. fucata - > 50 mm; P.
margaritifera - > 100 mm; and P. maxima - > 120 mm.
Preoperative phase – Traditionally oysters are weaken for 28 - 40 days by crowding or
subjected to poor growing conditions. This weakening induces the oyster to spawn and ensures
that it is sufficiently weak not to reject the inserted nuclei. More recently, spawning is induced
by bring the oysters near the surface where the water is warmer.
Implanting operations - Done during the cooler months, trained technicians insert one or more
nuclei and a small cube of donor mantle tissue into the host gonad tissue. Technicians are paid
~ $ 1,000/day ($ 3 – 4/oyster) plus expenses and implant ~ 300 oysters per day. The ideal size
of oyster for grafting is 4.5 – 6 in (12 – 15 cm) in length .
Postoperative care - Calm deep water - after 40, success is evaluated with catch bags or through
X-raying in larger operations. Oysters that have retained the nucleus are moved to the normal
grow-out area. Live oysters that have lost the nucleus are retained for “keshi” production.
Pearl culture grow-out - 18 months - 3.5 years; 2 mm of nacre after 2 years.
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Figure 1.
Production cycle of pearl oysters
Hatchery production of spat on cultch
Initial grow-out of pearl oysters
1 - 2 years
hanging culture; density reduced as the oysters
grow from ~200/m2 to ~10/m2
mesh cleaned every 6 weeks
Preoperative phase
30 - 40 days of crowding and poor growing
conditions - induces spawning and generally
weakens the oysters
Postoperative care
calm deep water - 5 months
X-rayed to evaluate success (~ 40 - 50%; 75%
with antibiotic coated nuclei)
Hanging culture 2 - 3.5 years
(2 mm nacre after 2 years)
Harvesting, polishing and sale
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Farm size
Minimum farm size ~ 3,000 graftable pearl oysters per 18 month production cycle. To maintain
this number ~ 12,000 – 15,000 pearl oysters of various sizes need to be maintained.
Depth 75 – 120 ft (22 – 36 m) away from reef areas.
•
•
•
Tahitian longline with ear-hung oysters on chaplets
Floating rafts
Floating rafts - pearl culture industry
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Underwater trestles
Production
Approximately 45% of the oysters that retain the nucleus for the first 40 days will yield
marketable pearls; however gem and A-grade quality pearls will only be around 15 % of the
total.
Grading and processing of pearls
5%
10%
30%
Gem-quality flawless
A-grade:
one flaw, small flaws, small stain, pink, silver or light cream
B-grade:
fairly large flaws, stains, cream color, or irregular shape
Average price/pearl = ~ $ 35; average production cost = ~ $ 28 for a 3,000 pearl farm; ~ $ 20 for
a 6,000 pearl farm
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55%
C-grade:
trash pearls, wild shaped, badly coated, heavily pock-marked, clayey
lumps
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Processing
Pearls are mixed with salt in equal volume and placed in a tub with a little water. The residual
mucus on the surface of the pearl is removed by rubbing with salt to obtain a good luster. Pearls
are typically drilled and sometimes "doctored". To improve the quality, drilled pearls are
bleached with hydrogen peroxide.
Production
Approximately 45% of the oysters that retain the nucleus for the first 40 days will yield
marketable pearls; however gem and A-grade quality pearls will only be around 15 % of the
total.
Grading and processing of pearls
5%
10%
30%
Gem-quality flawless (95% of the farmers income)
A-grade:
one flaw, small flaws, small stain, pink, silver or light cream
B-grade:
fairly large flaws, stains, cream color, or irregular shape
55%
C-grade:
trash pearls, wild shaped, badly coated, heavily pock-marked, clayey umps
Industry prices •
•
shell pearls -
US$ 8.00 - 11.00/kg
US$ 60,000/kg (average price per pearl = $ 120.00)
Industry statistics - 1993 production values
Japan Australia French Polynesia -
US $ 800 - 900 (domestic market uses ~ 2/3)
US $ 110 million
US $ 77 million
Presently producing ~ 5 tons of pearls annually
Maximum production ~ 8 tons of pearls (only 40 of the 130
French Polynesian islands suitable for production)
Global industry -
US $ 1.5 billion (32 nations)
Future developments
Beads = based on dolomite, common mineral with the formula CaMg (CO3)2, found
chiefly in rock masses as dolomitic limestone.
Extreme competition from Asian producers
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Marketing
The value of a pearl is determined by a combination of size and other factors. Other factors are:
shape (perfectly round > drop > oval > button > baroque) and color. The traditional color is a
clear, almost translucent white with a subdued iridescent sheen. Varieties of round cultured
pearls include white South Sea pearls, Tahitian gray-black pearls, high-gloss Akoya pearls with
rosy over-tones and golden Burmese pearls. The large and relatively rare Australian while pearls
have a golden or silver hue and generally the most expensive.
Tahitian black pearls actually come in a range of colors (see below), with the most desirable
having “peacock green” overtones.
Size is the determining factor, assuming all other factors are the same. Most jewelers consider
the seven to 7½ millimeters a classic size. The typical 18” strand (princess strand) makes a
useful comparison. For example:
Price-Costco 2003
18” Cultured pearl necklace (14 karat gold clasp) – pearl size 7 mm
Cost = $ 739.99
18” Cultured pearl necklace (14 karat gold clasp) - pearl size 8 mm
Cost = $ 1, 669.99
18” Cultured pearl necklace (14 karat gold clasp) - pearl size 9 – 9.5 mm
Cost = $ 3, 399.99
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Price is also dictated by fashion. Pearl fashion is cyclical. Historically these have been 10-year
cycles with the last boom in 1996.
The Art of Picking Pearls
Here are some tips on choosing pearls from the Jewelers of America Inc. and Tiffany & Co.
•
•
•
•
Look for a rich luster in the shadow area of the pearl, not where the light is shining.
Look for clear color tones, and avoid dull or muddy tones. Check carefully for cracks, chips
or blemishes.
Each pearl in a strand should be much like its sisters. They should blend well in shape, luster
and color. Roll a strand of pearls along a flat surface to determine if all pearls are strung
through their exact centers. All pearls should wobble evenly.
Spend the money on the pearls rather than the clasp; a more expensive jeweled clasp can
always be added later.
The Care of Pearls
Although thought of as gems, the water content and the organic matrix portends a limited life
span. The functional life span of pearls is in the range of hundreds of years depending on the
severity of the environmental conditions they face.
Here are some do’s and don’ts of pearl care from the Jewelers of America Inc.
•
•
•
•
•
Don’t toss pearls carelessly into your purse or jewelry box where they can be scratched.
Don’t clean pearls with chemicals or abrasives; simply rinse them with mild soap and water
or wipe them with a soft chamois cloth.
Do put pearls on last when dressing; hair spray, perfumes and cosmetics can dull the luster.
Do wrap them in a soft cloth, or keep them in a separate place when in storage.
Do have pearls restrung every year or so. The string should be silk and knotted between each
pearl.
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REFERENCES AND ADDITIONAL READING
Almatar, S. M., K. E. Carpenter, R. Jackson, S. H. Alhazeem, A. H. Al-Saffar, A. R. Abdul
Ghaffar and C. Carpenter. 1993. Observations on the pearl oyster fishery of Kuwait. Journal of
Shellfish Research 12:35-40.
Farn, A. E. 1986. Pearls: natural, cultured and imitation. Butterworth & Co. Ltd. London 150
pp.
Fassler, C. R. 1991. Farming jewels: the aquaculture of pearls. Aquaculture Magazine
(September/October) 34,36,38,40,42,44-52.
Fassler, C. R. 1991. The return of the American pearl. Aquaculture Magazine
(November/December) 63-78.
Fassler, C. R. 1992. Pearls: an update. Aquaculture Magazine (May/June) 66-70.
Fassler, C. R. 1993. Pearl culture taking off: international conference set for Hawaii.
Aquaculture Magazine (November/December) 89-91.
Gervis, M. H. and N. A. Sims. 1992. The biology and culture of pearl oysters (Bivalvia:
Pteriidae) ICLARM Studies and Reviews 21. 49 pp.
Hynd, J. S. 1955. A revision of Australian pearl shells, genus Pinctada. Australian Journal of
Marine and Freshwater Research 6:98-137.
Joyce, K. and S. Addison. 1993. Pearls: ornament and obsession.
Ikenoue, H. and T. Kafuku (eds). 1992. Modern Methods of Aquaculture in Japan.
Developments in Aquaculture and Fisheries Science, 24. Elsevier, Amsterdam, The Netherlands.
Landau, M. 1991. Introduction to Aquaculture. John Wiley & Sons, Inc. New York, New York,
USA. 440 pp.
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From: San Francisco Chronicle Thursday, December 12, 1996
The Wisdom of Pearls
They’re not inexpensive, but they’re for keeps
By Sylvia Rubin, Chronicle Staff Writer
Those in the oyster business remember 1986 fondly – big year for pearls. Maybe it was
the Barbara Bush factor. And then all was quiet for a while.
Until the Jackie O auction this year. Her fake pearls set a record price for costume
jewelry – a three-strand necklace sold for $211,000 in April.
Then Hollywood checked in. Renee Russo wore a pearl choker in every scene in “Tin
Cup.” Cameron Diaz looked classy in hers in “She’s the One.” All of the women in “First
Wives Club” received a strand of pearls, a gift from their rich college friend, in the opening
scene of the movie.
So what? “Sales are up in retail stores by an average of 18 percent this year,” said Devin
Macnow, executive director of the Culture Pearl Information Center in New York. “Pearl
fashion is cyclical. Historically it goes in 10-year cycles, and the last boom was in ’86.”
You really can’t go wrong with pearls no matter what the decade; an 18-inch strand,
called “princess” length, is a classic keepsake.
Where to Start
Begin by saving your pennies. That lustrous 18-inch strand of medium-sized pearls can
run as much as a fine one-carat solitaire. Translation: $2,000 to $ 3,000.
One word to remember is “millimeter” – as in, how many millimeters can I afford?
Most jewelers consider severn to 7½ millimeters a classic size – not too big, not too
small. Go down one millimeter to 6½, and the savings are significant, about an $800 drop per
strand. Many quality pearls can be found in that size. But jump up one millimeter, and you’ll
pay an extra $3,000 to $5,000 more per strand.
Varieties of round cultured pearls include white South Sea pearls, Tahitian gray-black
pearls, high-gloss Akoya pearls with rosy over-tones and golden Burmese pearls. South sea
pearls are the rarest and most expensive.
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Japanese Culture
Most cultured pearls come form Japan; the most familiar are the Akoya, grown along the
cost. Mikimoto, the only brand-name pearls are also grown on farms throughout Japan; Kokichi
Mikimoto, an oyster farmer who began his business in the late 19th century, is credited with
inventing the growing and harvesting of round cultured pearls.
“The Mikimoto name has a certain cache and is generally known for its superior quality,”
said Macnow, “but it is possible to find pearls of equal quality that do not bear the brand name.”
A cultured pearl is created by impregnating oysters with a tiny spherical piece of mussel
shell, then returning them to the sea in wire baskets hung from long, floating rafts. Pearls are
harvested after two to four years. The only way to tell the difference between a natural pearl and
a cultured one is to scan the pearl with an X-ray to see the substance of the core.
What it All Means
In Middle East lore, pearls were thought to ward off evil and, just for good measure,
impart virility. In China they represent chastity, femininity and charm and are said to bring long
life. In Japan, these little glowing spheres are thought to be gifts from the Moon Goddess.
Treating Your Pearls Right
“A strand of medium- to high-quality pearls should outlive its original owner by several hundred
years if they are treated right.
Here are some do’s and don’ts of pearl care from the Jewelers of America Inc.
•
•
•
•
•
Don’t toss pearls carelessly into your purse or jewelry box where they can be scratched.
Don’t clean pearls with chemicals or abrasives; simply rinse them with mild soap and water
or wipe them with a soft chamois cloth.
Do put pearls on last when dressing; hair spray, perfumes and cosmetics can dull the luster.
Do wrap them in a soft cloth, or keep them in a separate place when in storage.
Do have pearls restrung every year or so. The string should be silk and knotted between each
pearl.
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The Art of Picking Pearls
Here are some tips on choosing pearls from the Jewelers of America Inc. and Tiffany & Co.
•
•
•
•
Look for a rich luster in the shadow area of the pearl, not where the light is shining.
Look for clear color tones, and avoid dull or muddy tones. Check carefully for cracks, chips
or blemishes.
Each pearl in a strand should be much like its sisters. They should blend well in shape, luster
and color. Roll a strand of pearls along a flat surface to determine if all pearls are strung
through their exact centers. All pearls should wobble evenly.
Spend the money on the pearls rather than the clasp; a more expensive jeweled clasp can
always be added later.
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