Pe arl Stan dar d
2009 Version
Japan Pearl Promotion Society
The Pearl Standard
(2009 Revised Edition)
I
Classification
Pearls are metabolites formed in living mollusks. Their visible part is composed mostly of
substances equivalent to the mollusk nacre, consisting of concentric layers of calcium
carbonate crystals, usually in the form of “aragonite” and scleroprotein called “conchiolin”.
(Note 1)
I-1
Natural pearl
Pearls accidentally formed in living mollusks without aid of any human agency. Natural
pearls are classified into whole round natural pearls, blister pearls and blister according to
the formation mechanism and features.
I-1-1
Whole round natural pearl
Pearls accidentally formed in a pearl sac of living mollusks without aid of any human agency.
Their entire surface is covered with nacre.
I-1-2
(Note 2)
Natural blister pearls
Pearls accidentally formed on the inner surface of living mollusks shell without any human
agency. They first formed as natural pearls in a pearl sac, then broke mantle lobe to attach
on the surface of the shell, where host mollusks covered their surface with nacre.
I-1-3
Natural blister
Blisters accidentally formed on the inner surface of the mollusk shell without aid of any
human agency. They are originated by the intrusion of a foreign material into a space
between mantle and inner surface of the nacreous shell, or by hole repair of the shell bored
by the intrusion of parasites etc, irrespective of whether the internal construction is hollow or
nacre composition.
I-2
Cultured Pearls
Pearls formed in living mollusks with aid of human agency. Human intervention should only
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give an occasion of pearl formation and substance formed should only be of natural product.
Cultured pearls are classified into whole round cultured pearls, blister cultured pearls and
Hankei cultured pearls (cultured blister) according to the formation mechanism and features.
I-2-1
Whole round cultured pearls
Pearls formed in a pearl sac of living mollusks with aid of human agency. Human intrusion
should only give an occasion of pearl sac formation. Whole round cultured pearls are
classified into bead nucleated and non-bead nucleated cultured pearls.
I-2-1-1
(Note 3)
Bead nucleated cultured pearls
Pearls formed in a pearl sac of living mollusks by inserting a nucleus (or nuclei) made of
American freshwater mussel shells such as Pig toe (Fusconaia flava), Washboard
(Megalonaias gigantea), Maple leaf (Quadrula quadrula), Three ridge (Amblema plicata)
and Ebony shell (Fusconaia ebena) only by physical procedure such as cutting and
polishing into spherical shape, together with a piece (or pieces) of epithelial tissue. Nucleus
is entirely covered with nacre secreted by mollusks.
I-2-1-2
Non-bead nucleated cultured pearls
Pearls formed in a pearl sac of living mollusks by inserting only a piece (or pieces) of
epithelial tissue. They are entirely composed of nacre secreted by mollusks.
I-2-2
Cultured blister pearl
Pearls formed on the inner surface of mollusk shell with aid of human agency. They first
formed as cultured pearls in a pearl sac, then broke pearl sac to attach on the surface of the
shell, where host mollusks covered their surface with nacre.
I-2-3
Hankei cultured pearls (cultured blister)
Pearls formed on the inner surface of the shell of living wild or cultured mollusks by
attaching half or three-quarter shaped nucleus (or nuclei). The entire surface of the nucleus
is covered with nacre secreted by mollusks. It is irrespective whether the nucleus used
remains after cultivation or is removed and replaced with a different substance. The pearls
cut or ground to half or three-quarter from whole round pearls are excluded from this
category.
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I-3
Imitation pearls
Artificial products not formed in living mollusks but manufactured by imitating the
appearance, color and other features of natural or cultured pearls. It is irrespective of
whether physical or chemical properties are the same as natural or cultured pearls. Imitation
pearls are classified as follows by manufacturing methods.
I-3-1
Artificially made imitation pearls
Artificial products not formed in mollusks but manufactured by imitating appearance, color
and other features of natural and cultured pearls with materials such as shell, nucleus, glass,
plastics, fish scale etc. It is irrespective whether the same materials as natural and cultured
pearls are used and whether the surface is of the same as nacre of natural and cultured
pearls.
I-3-2
Shell modified imitation pearls
Curving part of the snail shell finished as a Hankei cultured pearl by cutting, grinding,
polishing and stuffing. Part of the shell nacre imitating a natural or cultured pearl by cutting,
shaping and polishing.
I-3-3
Coated imitation pearls
Natural or cultured pearls which surface is covered with artificial materials such as plastics,
lacquer etc.
II
Terms and descriptions
Natural, cultured and imitation pearls must be termed and described in accordance with the
terminology and classification set out in Clause I. This applies to the descriptions in an
official publication in all communications addressed to the public as well as to all business
matters. These terms and descriptions must not be abbreviated and should not be used
misleadingly.
II-1
Terms and descriptions of natural pearls
Natural pearls must clearly be termed or described that they are natural pearls in
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accordance with the Classification I-1. Pearls other than natural pearls classified in I-1 must
not be termed or described in the same manner as natural pearls.
II-1-1
Usage of the words of “real”, “precious”, “Orient” and “Oriental”
Terms “real”, “precious”, “Orient” and “Oriental” must not be used for terms or description of
pearls other than natural ones. The usage of the term “true” for the pearls other than natural
ones should be avoided, since the usage may be misunderstood as an intention to make
semblance of natural pearls.
II-1-2
Usage of the words “seed”, “poppy” and “dust”
The terms of “seed”, “poppy” and “dust” must not be used to term or describe tiny pearls
other than natural ones.
II-1-3
(Note 4)
Terms and descriptions of “blister pearl”
In accordance with I-1-2, the term “blister pearl” must not be used to term or describe pearls
other than pearls accidentally formed on the surface of mollusk shell without any human
agency.
II-1-4
Terms and descriptions of “blister”
In accordance with 1-1-3, the term “blister” must not be used to term and describe the
blisters other than blisters accidentally formed as a lump on the inner surface of the mollusk
shell without aid of any human agency.
II-1-5
“Conch pearl”, “Horse conch pearl” and “Melo pearl”
The terms of “Conch pearl”, “Horse conch pearl” and “Melo pearl” must not be used to term
or describe pearls other than pearls accidentally formed in Queen conch, Horse conch and
Melo melo without aid of any human agency.
II-2
Terms and descriptions of cultured pearls
Cultured pearls must clearly be termed or described that they are cultured pearls in
accordance with the Classification I-2. Pearls other than cultured pearls classified in I-2 must
not be termed or described in the same manner as cultured pearls.
II-2-1
Usage of the words of “cultured”, “cultivated”
Cultured pearls must be clarified as cultured by the term “cultured”, “cultivated” or equivalent
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terms such as “Yoshoku-shinju” or “Zuchtperlen”. Such terms must not be used for pearls
other than cultured pearls.
II-2-2
(Note 5)
Usage of the word of “Keshi”
Saltwater pearls having no bead nucleus in them obtained as by-product at the time of
cultured pearl harvest must be termed or described as “Keshi”. The term of “cultured” must
be added after Keshi, since Keshi is a by-product of sea water cultured pearl. It is preferable
to identify the mother oyster species such as “Akoya Keshi cultured pearl”, “Shirocho Keshi
cultured pearl (Silver/Gold lipped Keshi cultured pearl) ”, “Kurocho Keshi cultured pearl
(Black lipped Keshi cultured pearl)”.
II-2-3
(Note 6)
Terms and descriptions of cultured blister pearls
Cultured blister pearls must be termed or described that they are cultured blister pearls in
accordance with Clause I-2-2. Pearls other than those formed with aid of human agency on
the inner surface mollusk shell must not be termed or described as cultured blister.
II-2-4
Terms and descriptions of Hankei cultured pearls (cultured blister)
Hankei cultured pearls (cultured blister) must be termed or described as “Akoya Hankei
cultured pearl”, “Shirocho (Silver or Gold-lipped) Hankei cultured pearl”, “Kurocho
(Black-lipped) Hankei cultured pearl”, “Mabé Hankei cultured pearl” and “Awabi (Abalone)
Hankei cultured pearl” in accordance with the classification I-2-3. The pearls cut or ground to
half or three-quarter from whole round pearls are excluded from this category.
II-3
(Note 7)
Terms and descriptions of imitation pearls
Imitation pearls must be termed or described as imitation in accordance with the
classification I-3. Imitation pearls must not be termed or described with the same expression
of natural or cultured pearls in the classification I-1 and I-2. In describing imitation pearls
only by commercial names, “imitation”, “stimulated”, “artificial” or “man-made” must be put
before or after commercial names to clarify they are imitations.
II-3-1
Terms and descriptions of synthesized imitation pearls
Imitation pearls classified in I-3-1 must clearly be termed and described as imitation.
II-3-2
Terms and descriptions of shell modified imitation pearls
Imitation pearls classified in I-3-2 must clearly be termed and described as imitation.
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II-3-3
Usage of the words of “semi-cultured”, “half-cultured”, “part-cultured”
and “premature”
Terms
associating
with
cultured
pearls
such
as
“semi-cultured”,
“half-cultured”,
“part-cultured” and “premature” must not be used for imitation pearls manufactured by
covering the surface of nucleus or other materials with plastics or other materials. They shall
be clearly termed and described as “imitation pearl”.
III
Terms and descriptions of pearls by species and place of origin
III-1
Terms and descriptions of pearls by species
Natural or cultured pearls should be termed or described in accordance with the species of
mother oysters when they can be clarified by the certificate of place of origin, or by
appropriate methods.
III-1-1
Terms and descriptions of seawater natural and cultured pearls
Seawater natural and cultured pearls should be termed or described by the species of
mother oyster (in Japanese Katakana).
Seawater natural pearls
Conch natural pearl
Horse conch natural pearl
Melo natural pearl Awbabi
Awabi natural pearl
Akoyagai natural pearl (or Akoya natural pearl)
Shirochogai natural pearl (or Shirocho natural pearl)
Kurochogai natural pearl (or Kurocho natural pearl)
Mabé natural pearl
Akoyagai : Akoya pearl oyster (Pinctada fucata)
Shirochogai : Silver/ Gold-lipped pearl oyster (Pinctada maxima)
Kurochogai : Black-lipped pearl oyster (Pinctada margaritifera)
Mabé: Black-winged pearl oyster (Pteria penguin)
Awabi: Abalone (Haliotis sp.)
Seawater cultured pearls
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Akoyagai cultured pearl (or Akoya cultured pearl)
Akoyagai cultured Hankei pearl (or Akoya Hankei cultured pearl)
Akoyagai Keshi cultured pearl (or Akoya Keshi cultured pearl)
Shirochogai cultured pearl (or Shirocho cultured pearl)
Shirochogai cultured Hankei pearl (or Shirocho Hankei cultured pearl)
Shirocho Keshi cultured pearl (or Shirocho Keshi cultured pearl)
Kurochogai cultured pearl (or Kurocho cultured pearl)
Kurochogai cultured Hankei pearl (or Kurocho Hankei cultured pearl)
Kurocho Keshi cultured pearl (or Kurocho Keshi cultured pearl)
Mabé cultured pearl
Mabé Hankei cultured pearl
Awabi cultured pearl
Awabi Hankei cultured pearl
III-1-2
Terms and descriptions of Freshwater natural and cultured pearls
Freshwater natural and cultured pearls may not be termed or described by the species of
mother mussels by following reasons.
1) There are many mussel species to produce natural pearls, that makes it difficult to identify
them.
2) Mussels with common regional names are widely used, so it is difficult to identify their
species.
3) In pearl cultivation, pieces of mantle tissue from different mussel species are sometimes
transplanted, that makes the decision of the species difficult.
III-2
Terms and descriptions of pearls by places of origin
In terming or describing natural or cultured pearls, no places of origin are specified. However,
sometimes places of origin are specified to distinguish pearls from those of other places
where the same species pearls are produced.
Examples: Persian Gulf natural pearl, Japanese Akoya cultured pearl, Tahitian Black lipped cultured pearl,
American freshwater natural pearl, Peruvian Western winged natural pearl
IV
Cultured Pearl Quality Standard
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When handling cultured pearls as merchandise, their commodity and quality must be
specified. The specification applies to both loose pearls (undrilled, half-drilled,
drilled-through, three quarter and Hankei) and strands (threaded strands and finished
strands with clasps) of cultured pearls from all species of mother oysters.
IV-1
Commodity Standard
Commodity Standard of cultured pearls is specified by size, length of the strand, weight and
quantity.
IV-1-1
Size
Pearl size is indicated by millimeter (mm). In principle, pearls are measured by half of a
millimeter (1/2mm) or fourth of a millimeter (1/4mm). Sizes of spherical pearls are measured
by maximum diameter. Sizes of non-spherical pearls such as oval and button are measured
by maximum and minimum diameters (e.g. 16.2mm x 8.3mm). Sizes of rod-shaped pearls
are measured by maximum diameter, minimum diameter and length (e.g. 7.5-5.3 mm x
9.2mm).
IV-1-2
Weight
Weight of the pearl (both loose pearls and strands) is specified by Momme (1 Momme
=3.75g).
IV-1-3
Length of the strand
Length of the necklace is specified by inch (”) or centimeter (cm).
IV-1-4
Quantity
Strands are specified by numbers. Loose pearls are specified by pieces, pairs and sets.
IV-2
Quality standard
The Quality standard of the cultured pearl varies according to culturing methods, bead
nucleated, tissue nucleated and Hankei pearl. All cultured pearls must clear the following
standards.
IV-2-1 Quality standard of bead-nucleated cultured pearls
1) Pearls should possess pearl luster, not being spoiled by prismatic layer and/or organic
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substance.
2) Pearls should possess enough nacre thickness, showing no evidence of nucleus through
the nacre and partial thinness of the nacre.
3) Blemishes should be small and not fatal.
4) No cracks of the nucleus or the nacre should be recognized.
5) Rose tint, dyeing and coloring should be processed properly.
6) Processes should not be excessive. They should not cause posterior quality change of
the pearl.
7) Strains should not be conspicuous for having suitable smooth surface for work.
8) Pearls should not have broken nacre.
IV-2-2 Quality standard of non-bead nucleated cultured pearls
1) Pearls should possess pearl luster, not being spoiled by prismatic layer and/or organic
substance.
2) Pearls should possess uniform nacre, not having a hollow inside the pearl.
3) Blemishes should be small and not fatal.
4) No cracks of the nacre should be recognized.
5) Rose tint, dyeing and coloring should be processed properly.
6) Processes should not be excessive. They should not cause posterior quality change of
the pearl.
7) Stains should not be conspicuous for having to suitable smooth surface for work.
8) Pearls should not have broken nacre.
IV-2-3
Quality standard of Hankei cultured pearls
1) Pearls should possess enough nacre thickness to prevent from easy breakage.
2) Pearls should possess uniform nacre having smooth surface free of wrinkles and warts.
3) Blemishes should be small and not fatal.
4) Processing should properly be done. No unevenness of dyeing and color difference
should be recognized.
5) Damages such as peeling of the lid, cracks in the nacre, breakage of the nacre should not
be recognized.
V
Pearl Processing
Processing is physical and/or chemical action on cultured pearls to extract their latent
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beauty or to alter their quality such as color, appearance etc independently of their original
characteristics. All processing should be disclosed.
V-1
Processing Methods
V-1-1 Thermal processing
Removal of the unfavorable color and/or improvement of the luster by heating.
V-1-2 Bleaching
Removal of organic matter (stain) by oxidizing reagents such as hydrogen peroxide.
V-1-3 Rose tinting
Improvement of the color tone of Akoya cultured pearl by slight addition of reddish
pigments or dyestuff.
V-1-4 Dyeing
Color alteration different from original color by natural or synthetic dyestuff.
V-1-5 Coloration
Color alteration different from original color not by dyestuff but by chemical reagents.
V-1-6
Irradiation
Color alteration by gamma ray irradiation.
VI
Care Requirements
Natural and cultures pearls need following normal cares if their as-sold appearance is to be
retained in normal usage.
VI-1
Normal cares
1) Natural and cultured pearls should avoid rough handling.
2) Natural and cultured pearls should keep separated from other jewelry items to avoid
scratches.
3) Cosmetics should be applied before and not after any natural and cultured pearls are put
on.
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4) Natural and cultured pearls should not be for everyday wear and should not be worn while
carrying out heavy work.
5) Following wear, natural and cultured pearls require cleaning with a soft cloth.
6) When not worn for extended periods, natural and cultured pearls should be wiped
with a soft cloth at regular intervals.
VI-2
Special cares
In addition to normal care, natural and cultured pearls need following special care.
1) Natural and cultured pearls should not be exposed to strong natural and artificial light or
strong display lighting for an extended period of time. The color of natural and cultured
pearls may fade when exposed to natural sunlight, artificial light or strong display lights:
some pearls may revert to their original color.
2) Natural and cultured pearls should be kept away from acids and all solvents.
3) Natural and cultured pearls should not be subjected to ultrasonic cleaning.
Notes
Note 1
Although metabolites formed in Queen conch (Strombus gigas), Horse conch (Pleuroplica
gigantea),
Melo (Melo melo) etc do not possess nacre, they are treated as pearls exceptionally.
Note 2
The meaning of “whole round” described here is not the roundness in shape but the meaning of
“the whole surface of the pearl is covered with nacre”.
Note 3
The meaning of “whole round” described here is not the roundness in shape but the meaning of “the
whole surface of the pearl is covered with nacre”.
Note 4
Tiny natural pearls and cultured pearls without solid nucleus have been called by various names such as
“Keshi”, “seed”, “poppy” and “dust”. Presently, however, acoording to Cibjo Pearl Book, “seed”, “poppy”
and “dust” are used for natural pearls, while “Keshi” for cultured pearls.
Note 5
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In Japan, since the invention of cultured pearls, they have been traditionally accepted as“pearls”.
Therefore, the term “pearl” without “cultured” is generally used for association names, company names
and other names when it can be clearly distinguished from merchandise descriptions.
Note 6
Originally, Keshi was a Japanese word indicating very small natural pearls from Akoya pearl oysters from
olden times. Since the invention of cultured pearl, many Keshi pearls were obtained as by-product at the
time of cultured pearl harvest, and they began to be used as jewelry items. The formation of Keshi is not
clear, whether they are naturally formed or by the mechanism that the piece of mantle tissue separated
from nucleus to form a small pear without nucleus. In any case, Keshi, whether it is natural or cultured,
has the same structure as natural pearl, so both natural and cultured Keshi were handed together as one
category.
In Pamphlets of International Pearl Design Contest in 1995 and 1996, bigger sized pearls
without solid nucleus from Silver/Gold lipped and Black lipped oysters have begun to be called “South
Sea Keshi” or “Tahiti Keshi”. As different usage from original meaning caused a big confusion, CIBJO
(International Jewelry Confederation) has changed the definition of Keshi to “a trade name that
designates a no-beaded cultured pearl formed accidentally or intentionally by human intervention in
marine pearl oysters and is a by-product of the culturing process”. The old definition was “Keshi is a
Japanese trade name meaning small seawater pearl without nucleus as by-product of pearl cultivation”.
According to new CIBJO definition Keshi is specified as cultured pearl.
Note 7
In the past, only hemi-spherical nucleus was used, so pearls cultured with this nucleus were called
“Han-en” (half round). As non hemi-spherical, such as drop and heart shaped, nuclei have begun to be
used, the term has been unified to “Hankei” which means “half shape”. Among Hankei cultured pearls
Mabé is so famous that other Hankei cultured pearls from different pearl oyster species are sometimes
called “Mabé” as well. Usually original nucleus of Hankei cultured pearl is removed after harvest and the
vacancy is filled with another materials such as plastics and the lids, usually made of pearl oyster shell, is
put. That is because Hankei cultured pearls are called “composite” or “assembled”.
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