Pearl Standard

2020

New edition

Japan Pearl Promotion Society0Table of Contents
I.

PURPOSE OF THE STANDARD

II. THE PEARL’S CHARTERIII.

PRINCIPLES OF THE PEARL STANDARD

IV.

KEY INFORMATION FOR THE PEARL STANDARD

Chapter 1 Defining pearls
1. Definition of a pearl
1.1 Characteristics of pearl formation
1.2 Assessing the jewelry value of pearls
Chapter 2 The history of pearl culturing
1. Research on pearl formation and pearl culturing trials
1.1 Research on pearl formation
1.2 Research on pearl formation in Europe
1.3 Pearl culturing trials
2. The history of pearl culturing in Japan
2.1 Trials and industrialization of cultured pearls
2.2 Development of spherical pearl culturing techniques
2.3 Early development of the cultured pearl market
2.4 Establishment of the cultured pearl industry
3. Expansion of the pearl culturing industry
3.1 Silver-lipped pearls
3.2 Black-lipped pearls
3.3 Freshwater pearls
4. Cultured pearl industry after the Second World War
4.1 Export industry
4.2 Expansion of domestic demand
4.3 Globalization of the industry
5. Prospects for the cultured pearl industry today
5.1 Cultured pearls as jewels

15.2 Promotion of pearl jewelry culture
6. Footnote references
Chapter 3 Basic stance on quality standards
1. Assessing pearl quality
1.1 Background
1.2 The Pearl Culture Industry Law
2. Quality criteria for pearls
2.1 Shape
2.2 Nacre thickness
2.3 Flaws
2.4 Luster
2.5 Color
3. Quality inspections of pearls
3.1

Domestic quality inspections

3.2

Quality inspections of pearls

Chapter 4 Basic stance on processing and treatments
1. Background
1.1

Processing and treatment methods

2. Treatment disclosures
3． Overseas movements
4. Establishment of the standards
Chapter 5 Basic stance on pearl inspections and differentiations
1. Background
1.1 Differentiating natural and cultured pearls
1.2 Identification by pearl oyster species
1.3 Identifying pearls by place of origin
2. Identification methods
2.1 Magnification
2.2 Inner structure inspection
2.3 Spectrometric analysis
2.4 Fluorescence analysis
2.5 Composition analysis
3. Future tasks

2

3.1

Identification techniques

3.2

Terms for ‘Keshi’

3.3

Apprasing pearl quality

Chapter 6 Related laws
1. The Pearl Promotion Law
2. The Pearl Culture Industry Law

V.

DEFINITION, CLASSIFICATION, PROCESSING AND TREATMENTS OF PEARLS
1. Definition of pearls
2. Classification of pearls
2.1 Natural pearls
2.2 Natural blister pearls
2.3 Cultured pearls
2.3.1

Bead nucleated cultured pearls

2.3.2

Non-bead nucleated cultured pearls

2.3.3

Blister cultured pearls

3. Classification of blisters
3.1 Natural blister
3.2 Cultured blister
4. Classification of imitation pearls
4.1 Artificially made imitations
4.2 Shell-modified imitations
5. Pearl terms and descriptions
5.1 Terms and descriptions for natural pearls
5.1.1‘Natural’, ‘Real’, ‘Precious’, ‘Orient’ and ‘Oriental’

5.1.2‘Seed’ and ‘Dust’

5.1.3

Natural blister pearls

5.1.4

Natural blisters

5.2 Terms and descriptions for cultured pearls
5.2.1‘Cultured’ and ‘Cultivated’

5.2.2‘Honshinju’

5.2.3‘Keshi’5.2.4

Blister cultured pearls

5.2.5

Cultured blisters (Hankei cultured pearls)3

5.3 Imitation pearls
5.3.1

Use of the term ‘Imitation’

5.3.2‘Semi-cultured’, ‘Half-cultured’, ‘Part-cultured’ and ‘Premature’

6. Terms and descriptions according to species
6.1 Seawater pearls
6.1.1

Natural pearls

6.1.2

Cultured pearls

6.2 Freshwater pearls
6.2.1

Natural pearls

6.2.2

Cultured pearls

7. Processing and treatments
7.1 Processing and treatment methods
7.1.1

Drilling

7.1.2

Cutting (including three-quarter cutting)

7.1.3 Shaping
7.1.4

Polishing

7.1.5

Gluing7.1.6

Filling

7.1.7

Coating

7.1.8

Thermal processing

7.1.9

Mae-shori

7.1.10Bleaching

7.1.11

Tinting

7.1.12Dyeing7.1.13

Coloration

7.1.14

Irradiation

7.1.15Modification

7.1.16

Cultured blister (with lid) processing

7.1.17

Cultured blister (with shell) processing

8. Descriptions of cultured pearl standards
8.1 Commodity standards
8.1.1

Size

8.1.2

Weight8.1.3

Length of a strand

8.1.4 Quantity
8.2 Quality standards

48.2.1

Bead nucleated cultured pearls

8.2.2

Non-nucleated cultured pearls

8.2.3

Cultured blisters (Hankei cultured pearls)

9. Care of pearls
9.1 Routine care
9.2 Special care
10. Other related matters10.1 ‘Hanadama’10.2 PS treatment
10.3 Imitation pearls
10.4 Nucleus
11. Notes

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Ⅰ

Purpose of the Standard

The origin of the global pearl culturing industry began with the manufacturing ofhemispherical cultured pearls by Kokichi Mikimoto in 1893. In 1907, Tokichi Nishikawa
invented a technique for the production of whole, round cultured pearls known as the‘piece method’. This discovery has been handed down relatively unchanged from thisoriginal technique as a key technology for culturing pearls globally today. Over the years,
Japanese cultured pearls have had a major influence on jewelry trends and fashion styles
across the world. To acknowledge Japan’s historic position in the global pearl industry,“Pearl Promotion Law” was introduced in 2016.
In line with this, the Pearl Standard will explain the criteria to preserve the quality andmarket value of cultured pearls, as well as the jewelry created from them. To assure thesuccess of these standards will require mutual recognition by members of theinternational industry – from cultivators, manufacturers, distributers and consumers,
as well as those in related sectors – of the importance of maintaining the quality of pearls,
and the techniques for culturing them which were established in Japan.
The Pearl Standard will explain the historical origins of cultured pearls, clarify
associated terminology, and outline the criteria required to uphold the market value,
standards of processing and treatment, inspections, and legislation concerning theirproduction, manufacture and distribution,

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Ⅱ

The Pearl’s Charter

THE PEARL'S CHARTER
Established in 1993 (5th Year of Heisei)
Revised in 2019 (1st Year of Reiwa)
Established by Japan Pearl Promotion Society
Pearls, created by nature, are living jewels which have been enjoyed for centuries fortheir intrinsic beauty.
We have endeavored to enhance the natural beauty of cultured pearls through ourcommitment to improved techniques, while not affecting nature's work.
Pearls are now produced on a worldwide scale. This is a development which enhances
their universal acceptance.
It is our wish that pearls may enrich our daily lives and play an important part as amessenger of peace in the long run.
A pearl is a prayer for the quintessence of beauty that is created by nature and man. As
pearl cultivating pioneers and industrialists, it is our intention to promote and safeguard
the mystical quality of pearls making effective use of our experience and ability.

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Ⅲ Principles of the Pearl Standard
Japan Pearl Promotion Society’s 1993 “Pearl’s Charter” articulates the principles andvalues for the production, distribution and acquisition of cultured pearls as establishedby the industry’s founders. The Pearl’s Charter has since provided a guiding philosophy
for the execution of industry best-practice. This section will now provide an update tothese principles, adapting them for present circumstances, whilst maintaining
continuity with the universal values established by the Charter more than twenty-fiveyears ago.
Japan Pearl Promotion Society strives towards the global adoption of these standards tomaintain the commercial and aesthetic value of cultured pearls and ensure thesustainability of the processes involved in their production, as well as jewelry createdfrom them. The execution principles for maintaining these standards are as follows:1.

All involved in the pearl industry should aim to undertake all their activities in linewith UN Sustainability Development Goals (SDGs) to guarantee a long-term future
for the cultured pearl industry which has a history over 100 years.

2.

Those involved in farming cultured pearls should appreciate their historic, culturaland natural significance of pearls, jewels produced by chance through humanintervention with nature. As such, they should do their utmost to guarantee theconservation of the sea, which provides the nourishing natural resources to cultivate
pearls. They should also use pearl culturing techniques backed by the latest
scientific knowledge, technology and expertise, and should recruit and train talented
staff to provide future successors equipped to tackle the challenges of balancing
stable production with variable market demands.

3.

Those involved in processing and treating cultured pearls should endeavor to bringout the original, latent beauty of pearls by reducing the number of treatments andselecting techniques that will preserve pearl’s natural beauty for a long time. Where
processing or treatments are required, they should always disclose this information
to retailers and customers. They should also make efforts to apply a common
standard for correctly identifying and defining the beauty and value of pearls, since
all possess varying degrees of quality.
8

4.

Those involved in jewelry manufacture should aspire to use the skills of talented
designers who can showcase cultured pearls as fashionable and desirable attributes
in people’s lives. They should aim to enhance the existing beauty of pearls,
coordinating them with other materials which create jewelry pieces finished to ahigh standard that are tailored to suit the different categories of customer.

5.

Those involved in the sale of cultured pearls should have completed a good level of
education and training to both apprehend and convey accurate information about
the beauty, quality and value of pearls. They should acquire an appreciation of thedifferent customs and use of pearls by people all over the world and supply thisdiverse clientele with sincere and correct information about pearls and theirassociated products.

6.

Those involved in appraisal and valuation of pearls should have a sound grasp of thehistorical background of the industry and maintain an up to date knowledge of thelatest processing and treating techniques for pearls. This knowledge should be used
to accurately assess the type and quality of pearls, and detect the use of processing
and treatments, including their methods and extent to which they accord withdomestic and/or global standards. They should provide an honest account of thisassessment to ensure continued confidence of the consumer in pearl products.

7.

Those who own, wear or gain enjoyment from the use of pearls and pearl jewelry,should acquire a good understanding of the pearl industry and its associated jewelry,
and use the knowledge they have about pearls to drive the standards of work for
those employed in the industry. In addition, consumers should seek to properly
understand the quality of pearls so that they can make their own assessment by
requesting the correct information from businessmen (salesmen and expert
appraisers), which will monitor and improve the work of members of the pearl
industry.

8.

Those involved in the retail business of pearls should provide opportunities forcustomers to choose pearls and pearl jewelry based on accurate information about
the origin of, and techniques used in its production, as well as the latest fashion
trends. They should also promote a deeper understanding of the pearl to their clients,
including information about the domestic and overseas supply, providing guidance
9and advice based on recommendations in the Pearl Promotion Law.
9.

Those involved in operations management should have a good understanding of thetasks involved in all stages of the pearl industry to fulfil the basic tenets of the Pearl
Promotion Law and assist in making high-quality pearls for the international
market. They should strive to teach, nurture, advise and provide support to further
expand across the world the cultured pearl industry, which first originated in Japan.

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Ⅳ

Key Information for the Pearl Standard

Chapter 1
1.

Defining pearls

Definition of a pearl

A ‘pearl’ is defined by the following five characteristics.
① It is formed in the nacreous body of an oyster② It involves the creation of a ‘pearl sac’
③ A biomineral pearl is formed in the sac④ The whole surface of the pearl is formed from the same nacre as the shell ofpearl oysters (nacre is defined as a stratified structure formed from a mixture ofcalcium carbonate crystal called ‘aragonite’ and an organic matrix called‘conchiolin’)⑤ It has jewelry value.
The criteria from ① to ④ are based on the processes by which a pearl forms, whereas
criteria ⑤ is based on the resulting value of a pearl.
1.1 Characteristics of pearl formation① It is formed in the nacreous body of an oyster
The advanced tissue culturing techniques developed for vertebrates, such as humanbeings, cannot be applied to invertebrates such as oysters. Therefore, it is impossible toartificially synthesize biomineral pearls by culturing cells in this way from the mantle
tissue of an oyster. However, as the detrimental impact of synthetic diamonds to themarket has shown, we cannot rule out that it may be possible in the future to artificiallysynthesize pearls.
As there has been an increase over the years in the production of fake pearls, made infactories or laboratories, it is important to clarify the definition of pearls in support ofcriteria ①“A pearl is a substance made by an oyster in the natural sea”.

11

To preserve the value of pearls, it is important to differentiate between pearls that are
nurtured in the natural environment, and those that are produced from artificial
substances.
② It involves the creation of a ‘pearl sac’
③ A biomineral pearl is formed in the pearl sac
There is evidence that research on pearls and their production from oysters was started
early as 16th to early 18th century in Europe. At that time, it was observed that pearls
and oyster shells are made from the same substance. In 1856, Theodor von Hessling ofGermany discovered by his detailed histological observation that when an external
stimulus causes the epithelial tissue of the mantle to intrude into the body of an oyster,
it forms a cyst within which a pearl is formed. The cyst that Hessling discovered waslater named “Sac de la perle” in 1899 by Leon Diguet of France. It was so named after it
was shown that pearls are made inside this sac, which is composed from the same cells
as that of the mantle. A cultured pearl therefore is a pearl formed in pearl sac that has
been artificially stimulated to form inside an oyster’s body.
The history of the cultured pearl industry began with Kokichi Mikimoto, whose ambition
to produce jewel-quality pearls using Akoya oysters, led to his first meeting with Dr.
Kakichi Mitsukuri of Tokyo Imperial University. Dr. Mitsukuri’s knowledge and researchon pearls firmly convinced Mikimoto that making pearls through human intervention
was possible. In 1907 three Japanese, Kokichi Mikimoto, Tokichi Nishikawa and Tatuhei
Mise established their own techniques to form a spherical pearl in an oyster body, andMikimoto paved the way for a new spherical pearl culturing industry.
Criteria ② and ③ are based on the scientific and historical characteristics of pearl
culturing.
④ The whole surface of a pearl is formed from the same nacre as the shell of pearl
oysters
In 1919, when Kokichi Mikimoto started to sell his cultured pearls in Europe, jewelers
in Paris who were at that time trading in natural pearls, boycotted cultured pearls tostop their influx into the pearl market. Mikimoto subsequently filed a lawsuit against
this movement. Through a close inspection of cultured pearls by leading scientific experts
in the pearl industry at the time, it was declared that cultured pearls were in fact real
pearls. After the verdict of September 20, 1924, a statement was released that “Japanese12

pearls should be recognized as high quality pearls made from nacre, with a nacreous
nucleus inside them”. It was concluded that cultured pearls are thus true pearls because
they are constructed from the same nacre as natural pearls.
Criteria ④ is therefore supported by the definition resulting from the outcome of theParis court trial which concluded that “cultured pearls are real pearls as they have thesame nacre of natural pearls”. At that time, it was also shown that the nuclei were madefrom nacreous material.
For further details, see Chapter 2 The history of pearl culturing.
There are some examples of pearls that do not correspond with the above characteristics
but have historically and exceptionally been treated as pearls because of their jewelry
value. These examples are biominerals produced in mollusks that do not have nacreous
structured in their shells, such as Queen Conch (Lobatus gigas), Horse conch(Triplofusus gigantea), Melo (Melo sp) and Hardclams (Mercenaria mercenaria). Also
blisters having the requisite worthy of jewels are thus excepted from the definition
provided in ①‐④, since they have historically been treated as pearls.
1.2

Assessing the jewelry value of pearls

As criteria ⑤ It has jewelry value indicates, it is important to consider the criteria thatmake pearls jewels, as well as their processes of formation. We have to decide therefore
what characteristics give peals value as jewels, by considering three factors: beauty,
durability and rarity.
(1) Beauty
Beauty of a pearl depends on its characteristics, such as shape, nacre thickness, extent
of flaws, its luster and color. In addition, smoothness transparency and evidence of
blemishes on the surface are important considerations. The beauty of a pearl on thewhole is judged by a qualitative assessment of the relative beauty of each of these aspects.
In this respect, the evaluation of pearls is rather different from other gemstones. In orderto improve the beauty of pearls, diligence is needed throughout all stages from supplying
high-quality raw materials (pearl oysters and nuclei) through to their production,
processing and distribution.

13

(2) Durability
The characteristics of pearls greatly differ from those of other gemstones, which are
typically composed of wholly inorganic substances. A pearl is composed of a stratified
structure called nacre that consists of thousands of inorganic calcium crystals calledaragonite and an organic matrix called conchiolin piled together. The durability of a pearl
is determined by the thickness of its nacre. The thicker nacre becomes, the more durable
a pearl is. However, not only thickness, but also other characteristics of nacre areimportant, such as its nature, shape, uniformity of layers of calcium carbonate crystals
and the strength of its organic matrix. The durability of a pearl decreases when different
calcium carbonate crystals called calcite and other foreign substances are present in thenacre. The thickness of nacre is determined during the production stages of pearl
culturing, but the degree of damage to the organic matrix varies according to any
subsequent treatments it undergoes, as well as how well it is stored and handled
afterwards.
For these reasons, the durability of pearls can be evaluated by nacre thickness and thedegree of injuries to their organic matrix. For example, there are occasions where a pearl
may have extremely thin nacre which gradually by deterioration and abrasion of thesurface, exposes the nucleus. As a result, its jewelry value can be rapidly lost in a shortperiod of time. Another example involves deterioration of the organic matrix (conchiolin),which decreases the latter’s adhesive power, causing the nacre of a pearl to peel off. In
addition, extreme damage to the organic matrix can be caused by ultraviolet light, heatand excessive physical and chemical treatments. The durability of a pearl therefore
depends on maintaining adequate nacre thickness during the stages of culturing andpreventing the organic matrix from being damaged after it is harvested.
(3) Rarity
It is often said that natural pearls are rarer then cultured pearls, since they result fromchance finds. However, low availability does not necessarily translate to rarity value.
When we see beautiful Conch natural pearls, we can appreciate that they are rare as noother mollusks yield them, thus rarity value increases. However, natural pearls fromclams and oysters do not possess as high a rarity value, even though they are rare.
In the case of cultured pearls, those which are yellow in color were once not so highly
evaluated. However, due to improvements in culturing techniques, the appearance ofyellowish pearls has gradually been controlled. As a result, rarity value of golden
14

cultured pearls has increased in recent years. Unlike natural pearls, the rarity value of
cultured pearls can be easily lost if we artificially produce as many as the same type as
possible. When production exceeds demand, the flood of low quality pearls into themarket can damage the rarity, and thus value of cultured pearls. In order to maintainthe rarity and value of cultured pearls therefore, it is important to continue our efforts
to raise the overall quality standards of pearls and eliminate low quality pearls from themarket.
Determining the jewel value of pearls can be summarized in the table below.
BeautyCharacteristics

Durability

RarityShape, nacre thickness

Nacre thickness,

Overall ratio of high to low

flaws, color, luster

structural soundness ofquality pearls produced

organic matrix (conchiolin)
Improvement measures

Production to enhance

Treatments, stability

Maintaining aquality, orientation

sustainable production

towards nacre thickness

rate

15

Chapter 2

The history of pearl culturing

This chapter describes the invention of cultured pearls, and the history and growth ofthe cultured pearl industry.

1. Research on pearl formation and pearl culturing trials
1.1

Research on pearl formation

For thousands of years, natural pearls have been highly praised in culture around theworld as rare and beautiful chance finds from mollusks. The fashion for being adored by
precious, lustrous pearls was a practice enjoyed by an elite, privileged few.1.2
Throughout history, people were fascinated with the mysterious origins of pearls, andthus invented many stories for how pearls are born. The Roman naturalist andphilosopher of the first century B.C, Pliny the Elder (Gaius Plinius Secundus), stated in
his opus, Naturalis Historia, that “pearls are formed from drop of dew”. This theory was
widely believed until the 11th century or so, when the notion that a pearl is born from aseed conceived in a mollusk’s body by a natural accident became popular. However, theprecise cause of a pearl’s formation was still shrouded in mystery.3
Through the development of modern science from the middle of the 16th century, theimaginative theories for the causation of pearls were gradually debunked. Peopleinterested in pearls tried to make them by their own hands with a scientific spirit ofinquiry. They began research to prove the secret of the pearl’s origins, and from the 18th
century to the beginning of the 20th century, pearl formation was a topic enthusiasticallystudied in Europe. Based on this body of research, from the end of the 19th century to thebeginning of the 20th century, many attempts in different corners of the globe have been
made to generate a pearl culturing industry.4
1.2

Research on pearl formation in Europe

To explain the origins of pearls in the latter 16th up to the 17th century, ‘disease causation’,‘egg causation’ and ‘sand causation’ were popular theories proposed. As a result of thesenew directions in thought, the ‘dew causation theory’ which had been widely believed up
to that point was completely disproved.1-5 In the 18th century, Réaumur (R. A. de16

Réaumur) of France proposed a theory that provided an early precursor to the modern
scientific understanding of pearl causation. He hypothesized that a pearl was formed
from a mass of materials secreted in the oyster’s body when the shell-producing mantle
tissue was damaged by intrusion of foreign matter or some outer force.6
The most important development for elucidating the cause of pearls was the discovery of
the pearl sac. In the middle of the 19th century, T. von Hessling of Germany discovered
through histological observation that an external force can cause the epithelial cells of
the mantle to intrude into the oyster’s body to form a cyst, and this is the cyst in which
pearl is formed. The cyst that Hessling discovered was later named the ‘sac de la perle’(pearl sac) by L. Diguet of France, who pointed out that the pearl is formed in the cyst
(pearl sac) which consists of the same cells as that of the mantle.7-9 After that time, many
researchers noticed that the pearl sac is closely related to pearl formation and thediscussion as to how pearl sacs formed became the center of these inquiries.
At the beginning of the 20th century, H. L. Jameson of England and L. Boutan of France
reported that pearls are formed in pearl sacs, but they believed that the formation of thesac itself had something to do with parasites.10,11 Though admitting that parasites may
have a role, many researchers, through further investigations, began to notice thatparasites are not the only cause for pearl formation.12-15 In 1911, A. Rubbel of Germany
rejected the earlier parasite causation theory, insisting that pearls are formed in an
oyster’s body when a part of the epithelial cells of the mantle covers an intrusive foreign
body.16 In 1912, Jameson reached the same conclusion.17
A common consensus amongst researchers from the beginning of the 20th century wasthat the important thing for pearl formation was not the exact nature of the substancewhich forms the nucleus, but the fact that an external intrusion causes epithelial tissue
to fall onto the biological tissue causing the oysters to construct a pearl sac. In 1913, F.
Alverdes of Germany succeeded in producing a pearl by his experiments using
freshwater mussels (Margaritifera margaritifera).18The discussion thus concluded that“the formation of the pearl sac is crucial, whilst the nucleus – an external substancearound which a pearl forms – is but only one aspect that causes a pearl to form”. In Japan,
however, the reasons for pearl causation had already been identified by 1907, andsubsequently the gateway to industrialization of cultured pearls was opened.
1.3

Pearl culturing trials
17

For hundreds of years, people have desired to make pearls by human hands. In China,
from the 11th to 13th century A.D, the technique to produce hemispherical cultured
blisters and Buddha-shaped cultured pearls (cultured blisters) using freshwater mussels
had already been developed. At a later time, cultured blisters came to be sold as
ornaments and talismans or souvenirs with shell attached to them. Such products,
however, were far from the jewelry we associate with pearls today.
Later, trials to culture pearls were frequently made in Europe. The Swedish scientist C.
von Linnaeus, experimented with producing pearls by drilling a hole through the shellof a freshwater mussel, and inserting a small ball made of limestone between the shelland mantle with a silver wire, which succeeded in making a pearl by manmade
intervention.2 From the 19th to the beginning of the 20th century, many attempts weremade to manufacture pearls at an industrial level. At that time the main techniques forforming pearls consisted of two methods: to insert a globular nucleus through a hole
drilled in the shell, and to form a pearl by infecting it with a parasite.
In 1825, J. E. Gray expanded Linnaeus’ method by announcing that pearls could be
artificially made by inserting a piece of nacre between the shell and the mantle. In 1838,
J. Wall’s attempt to make a peal following Gray’s method ended in faiure.19 Attempts toinsert a small ball into the space between the shell and the mantle to make a blister weremade by G. Bouchon-Brandely in 1884 in French Polynesian Tahiti by using Black-lipped
oysters, and by L. Boutan of France by using abalone off the coast of California. Althoughthese trials reported successful experiments, none of them had yet to achieve industrial
levels of production.20-22
Trials to set up companies raising pearl oysters and culturing pearls were made in many
places of the world. William Saville-Kent, who had conducted experiments in the Torres
Strait, succeeded in making hemispherical pearls, and set up a company in 1906 withplans to culture pearls further. However, in 1908 he died, and his enterprise ended
suddenly. Regrettably, the technique he used to produce cultured pearls are unclear due
to the paucity of records describing his methods.23
In 1909, J. Clark tried to culture pearls in Australia using Silver-lipped and Black-lipped
oysters. During this same period, many trials for culturing pearls were conducted: by G.
J. Vives of the USA near La Paz in Mexico using Black-lipped oyster and abalone, by A.
18

Seale using Silver-lipped oyster from the Sule Archipelago in the Philippines, and by T.
Haynes in Monte Bello Island, Western Australia using Shark Bay oyster (Pinctada

albina)2,13. Around 1909, J. I. Solomon of the USA succeeded in culturing hemispherical
pearls using Silver-lipped oysters from Mergui Island. He sold them in London and New
York between 1911 and 1912, but his business was discontinued after that time.20
From the end of the 19th century to the beginning of the 20th century, many trials to
culture pearl were made across the world. All of them were challenged not only tocultured pearls at an experimental level, but to achieve an industrial level of cultured
pearls at the entrepreneurial level. All these trials, however, did not develop the samelevel of industry to culture pearls for jewelry as Japan did.24

2.

The history of pearl culturing in Japan

2.1

Trials and industrialization of cultured pearls

In Japan, natural pearl have been collected from Akoya oysters and abalone throughout
time, and highly prized as jewels. In the Meiji era, natural pearls were treasures to be
traded at a higher price compared with other exported marine products. As a result, thenumber of Akoya oysters decreased due to overfishing, causing the number of natural
pearls to decrease sharply. In Ago Bay, which is situated in Ise-Shima of Mie prefecture
in Japan, natural pearl collection was a major concern as it decimated the population of
Akoya oysters.
Kokichi Mikimoto, handling natural pearls, started his experiments on 11 September
1888, breeding Akoya oysters near Benten Island in Shinmeimura, Ago Bay. In 1889,
through an introduction by Naraetsu Yanagi, he met Dr. Kakichi Mitsukuri of Tokyo
Imperial University (the first Director of Misaki Marine Biological Station) who was wellinformed about pearl culture study. Mikimoto was given examples of research andinstructions on pearl causation, as well as case studies of attempts to culture pearls in
Europe.
With advice from Dr. Kishinoue (Professor of Tokyo Imperial University) and otherresearchers, the collaborative efforts of Kokichi Mikimoto and Kakichi Mitsukuri paved
the way for the development of culturing techniques and the improvement of researchwhich would lead to the industrialization of the pearl industry in Japan. Receiving
19

instructions from Mitsukuri and others, Mikimoto was convinced that it was possible toculture pearls, and so he set about undertaking pearl culturing experiments in thefollowing year, 1890, in the inner part of Ago Bay.
Embracing his ambition to make pearls with his own hands, Mikimoto challenged thelimits of pearl culturing with experiments which inserted different foreign substances
into an oyster’s body, frequently changing the place for insertion through trial and error.
Although the oysters he used for his experiments were decimated by a red tide which
occurred in November 1892, another experiment in the seas around Ojima (present day
Mikimoto Pearl Island) escaped from calamity. On July 11, 1893, he found five blisters(at that time Mikimoto called these half-pearls) attached to the inner shells of his oysters.
Mikimoto examined how these pearls were made, and established a technique to culture
half-pearls, patenting the technique (Patent No.2670 ‘Method for pearl formation’).
Taking advantage of this development, he expanded industrialization and set up a pearl
farm on Tatoku Island in Ago Bay on October 26, 1899. Advancing this technique, he
improved production enough to succeed in the mass production of half-pearls. He used
his cultured half-pearls to create jewelry, and in 1899 he sold half-pearl ornaments forthe first time, rapidly expanding his business.
2.2

Development of spherical pearl culturing techniques

In the year 1907, three Japanese men, Kokichi Mikimoto, Tokichi Nishikawa andTatsuhei Mise applied for patents for a technique to produce spherical pearls.* They arethus called the inventors of the spherical pearl, and the Japanese pearl industry views
this year as the founding year for spherical pearl invention.25 These patents prove thatJapan had identified the cause for pearl formation and developed practical techniques
for spherical pearl production ahead of Europe.
At the time or trial and error experiments with spherical pearl culturing at Mikimoto’s
pearl farm, a red tide occurred on January 10, 1905, which continued for three months
resulting in 850,000 oysters, four fifth of his total stock to die. However, five pearls, with
their surface entirely covered in nacre, were accidentally found among the surviving
oysters operated on that year. As proof of his success, Mikimoto devised a spherical pearl
forming method, a technique which he used from 1905 to 1907 to harvest pearls in thewinter of 1907. Among the harvest, he chose good quality pearls to present to theEmperor Meiji. His technique involved using a spatula-like instrument, pressing the20mantle gently to form a sac into which a nucleus was inserted. He applied for a patent
for this method in 1907, and Patent No. 13673 ‘Method for pearl formation’ was grantedin the next year, 1908. As this method was invented in the 38th year of Emperor Meiji’sreign (1905), it was called the ‘38 method’ or ‘Meiji method’. The yield of pearls by thismethod, however, was extremely poor.
During this period, Mikimoto invited former dentist Otokichi Kuwabara in 1902 to tackle
the development of full-scale pearl culturing. He improved the tools for inserting thenucleus into an oyster by modifying dental instruments, such as adapting a forceps
clamp into a shell opening tool, which is used even today.26 Based on a pearl forming
method developed in 1914 called the ‘Taisho method’ (Patent No. 29429), Mikimoto
devised another similar method in 1917 to insert a round shape bead made of shell,
completely wrapped in mantle tissue into the body (gonad) of another pearl oyster. He
applied for and was granted a patent ‘Method pf pearl formation’ (Patent No. 33640) for
this technique in 1918, which is commonly referred to as the ‘Wrapping method’.
Although this method yielded good quality pearls, the efficiency of this method was poor
as it involved extremely intricate and time-consuming labor.
At first, the ‘Wrapping method’ was treated with caution due to several technicaldifficulties. To investigate the robustness of this method, the Imperial Association of
Inventions sent five Association members, including Chujiro Sasaki, to visit Mikimoto in
May 1926 to investigate his cultured pearls. This action reflected the continuing doubt
and suspicion attached to cultured pearls, even though the outcome of the Paris trials in
1924 had concluded that there was no difference between natural and cultured pearls,(see Chapter 2, 3. Early development of the cultured pearl market). The Imperial
Association of Inventions thus decided to visit Mikimoto’s pearl farm to assess how he
was able to culture pearls by such an elaborate technique as the ‘Wrapping method’.
According to a report by the Association, the survey conducted by Professors of Tokyo
Imperial University, Chujiro Sasaki, Kamakichi Kishinoue, Seitaro Goto and others,
appraised the technique as a legitimate invention for global application.
The report states as follows27:“When this method was published by the Patent Office with Patent No.33640, it was
believed, at least by some Japanese that the technique of the tying the mouth of the bag
formed by the mantle parenchyma would be too delicate and almost impracticable. There
21

were certain European scientists who also held the same opinion. The actual
performance of the delicate operation at the hands of expert technicians created great
surprise. The pearl oysters after being so treated are left for seven years in the nursery.
Out of fifty oysters picked out of the bed at random, on an average thirteen containperfectly spherical pearls. After careful examination of these pearls, the Committee cameto the conclusion that they were in luster, color and shape, and in every other way, equal
to natural pearls. The attainment of this remarkable success is solely dependent on theapplication of science. For this invention, now universally known, Mr. Mikimoto deserves
the highest praise.”
Prior to this Tokichi Nishikawa, a graduate of Tokyo Imperial University, who had
worked as a fishery engineer for the Ministry of Commerce, began working on pearl
culturing techniques with Mikimoto. The collaboration began after he attended, on Dr.
Mitsukuri’s behalf, the first harvest of hemispherical pearls at Mikimoto’s pearl farm.
When a red tide occurred at Mikimoto’s pearl farm, he often visited for investigation ofthis recurring issue, and in 1905 he rejoined Tokyo Imperial University. In this post, he
was able to devote his time to pearl research work, even at one time undertaking joint
research with Mikimoto in the laboratory at his pearl farm of Tatoku Island. Under theguidance of Dr. Kakichi Mitsukuri and Dr. Isao Iijima, Nishikawa conducted research byhimself at Misaki Marin Biological Station from April 1906. Striving to stimulate a pearl
sac in an oyster’s body to form spherical pearls, he devised a technique to transplant asmall piece of mantle into an oyster’s body. In 1907, based on the results of his research,
Nishikawa applied for four ‘Pearl formation methods’ patents, one on May 13 and three
on October 24, 1907. Three of his applications, Patent 29628, Patent 29629 and Patent
29630 were granted on Jun 20, 1916, with the remaining Patent 30771 on February 15,
1917. Among these four patents, Patent No.30771 became the main prototype for thetechnique that is now used in all pearl culturing farms worldwide today.
Before these patents were granted, Mikimoto has signed an agreement with Nishikawa
to undertake experiments at Mikimoto Pearl Research laboratory in Tatoku Island toprove the techniques he had been developing. As for practical experiments on nucleus
insertion, Kuwabara and Shinjuro Nishikawa, Tokichi’s brother, took on this challenge.
Operations were conducted for about three months beginning in September 1907, withapproximately 27,000 oysters operated upon in total. To keep this research secret,
Mikimoto’s Pearl Research Laboratory was moved in February 1907 from Tatoku Island
to the location of the Mikimoto Pearl Research Laboratory today on the mainland at22

Osaki peninsula, west of Tatoku Island. After submitting an application for these patents,
Nishikawa continued his research both at his own pearl farm on Awaji Island in Hyogo
prefecture, and Misaki Marine Biological Station in Kanagawa prefecture. Despite
tireless work on many experiments, Nishikawa sadly died in June 1909, aged thirty-five
before seeing his work come to fruition.
In August 1913, at the first interim survey to monitor the progress of cultured pearl
production, a sample of pearls was harvested in the presence of Dr. Isao Iijima, Sukeyo
Fujita, Masayo Fujita, Shinjuro Nishikawa and Otokichi Kuwabara. The pearls
harvested during this research were true spherical pearls created at the hands ofcultivators, a fair number of which were collected. However, the results in terms of pearl
size, yield and quality were not satisfactory. Subsequently, the techniques for culturing
were improved and this knowledge was disseminated by Masayo Fujita, a disciple ofNishikawa. Nishikawa’s pearl culturing technique became known as the ‘Piece method’,a technology that spread to foreign countries and is now widely used in the present-day
pearl culturing industry. A patent for this method was applied for in Australia by his son
Shinkichi Nishikawa on July 24, 1914, granted the next year on December 7, 1915 as
Patent No. 13,959. The title of the patent is ‘The artificial method of stimulating theformation of free pearls of regular form by pearl producing mollusca’. This stated that a
nucleus of ball-shaped, shell nacre can be inserted together with a small piece of mantle
tissue into the body of an oyster body to produce spherical pearls.
Tatsuhei Mise was another key person, whose work contributed to the success ofculturing spherical pearls. In 1902, with an interest in pearl culturing, Mise moved
15,000 pearl oysters from Shinmei Village (present-day Shima City) to Matoya Bay,
where he began his research on spherical pearl culturing. On March 1, 1907, Miseapplied for a patent entitled, ‘A needle to insert a nucleus for pearl coating into themantle tissue of an oyster’. This patent, Patent No. 12598, was granted on July 27 of thesame year. This patented a technique using a syringe-like tool – a needle with a sharp,
slantwise cut edge – to separate a piece of the mantle, this needle then injected a small
nucleus along with a piece of mantle into the tissue of an oyster where a pearl is formed.
Mise continued his research, filing another patent in 1917, which was granted three
years later in 1920, as Patent No.37746. This patented a method for producing spherical
pearls by making several small holes into the mantle at the place where it is attached to
the flesh of an oyster towards the outer epithelium, nuclei are inserted into the holes in23

the mantle, causing outer epithelial cells to intrude into the inner mantle to form a pearlsac. This is generally referred to as the ‘Induction method’. However, the effectiveness of
introducing epithelial cells from the outer surface of the mantle into the body of an oyster
was not satisfactory for practical application.
It can be seen that the pearl forming techniques of Japanese scientists, each with theirown original characteristics, were at that time the most advanced in the world. The
patents they obtained prove that they had identified the reasons for pearl causation,with the cultured pearls techniques in Japan ahead of those in Europe. The efficiency ofthese early methods at the beginning of the 20th century, however, were so low thatcommercial industrialization was utterly impossible.
(Spherical pearl*: a pearl that with its entire surface covered in nacre)
2.3

Early development of the cultured pearl market

In 1918, with the prospect of industrial scale pearl culturing using the ‘Wrapping
method’, Mikimoto set about marketing spherical pearls he had cultured for theEuropean market, the center of the natural pearl trade at that time. Beginning with his
first sales in London, Mikimoto’s entry onto the European market had a great impact on
European jewelers, especially in London and Paris which up until that time had dealt
exclusively in natural pearls. Suspicion of cultured pearls was so aroused in London in
1921, with the flames quickly leaping to France where the Association dealing withjewelry developed Boycott movement, vociferously waging a campaign claiming cultured
pearls were fake.
Against this movement, Mikimoto appealed to a civil trial, which was brought to court
to decide whether cultured pearls were genuine or fake. Although the opposition, The
Commercial and Industrial Association of France, tried to prove that cultured pearls
were imitation, famous scholars with extensive knowledge of pearls, Professor Jamesonof Oxford University and Professor Boutan of Bordeaux University bore witness at thetrial to support the scientific view that “there is no difference between natural andcultured pearls in terms of their formation and structure”. Finally, in 1927, a verdict was
passed by the French court that “cultured pearls are the same as natural pearls”. Having
endured these trials, cultured pearls were finally recognized as gems in the world jewelry
market.
24

The background of this struggle should not be forgotten, nor the efforts of the forerunners
who devoted themselves wholly to culturing thickly nacred pearls to rival natural pearls.
Mikimoto, along with many others, through these concrete cultured techniques andsuccesses in attaining in industrial level production, created a jewelry market for
spherical cultured pearls ahead of other countries. Nowadays, the global cultured pearl
industry, which was founded in Japan, has grown into one of the largest jewelry markets
in the world.
2.4

Establishment of cultured pearl industry

Since developing knowledge about how pearls are naturally formed and having had
success in producing high-quality pearls, the technical developments to raise theirstandards for use in jewelry has since been energetically progressed. Cultured pearls not
only build on the natural principles of pearl formation, but their techniques may also
upgrade the quality of pearls as jewels. In the early years of spherical pearl culturing,
the location for inserting the nucleus was mainly in the area surrounding the mantle.
However, as the mantle of Akoya oyster is thin, it was difficult to make large sized pearls.
After experimenting with different suitable locations for inserting nuclei, the gonads ofan oyster have proved the most suitable region for producing large pearls. In addition,
developments in nucleus insertion techniques, such as the refinement of operation tools,
and improvement in the management of pearl farms, such as the suspension of culturing
cages from the sea surface, the regular cleaning of shells and the wintering of oysters,
have resulted in rapid improvements to the overall quality of cultured pearls. Thus,
through these advances in nucleus insertion techniques and culturing activities, themass production of quality cultured pearls was nearly perfected by the 1920’s, andthereafter they have been widely distributed on the international market.
It can be said that Mikimoto and others were the first to advance concrete practicalculturing

methods,

perfecting

thesetechniques

to

the

point

of

successful

industrialization of spherical pearl culturing, which resulted in the rapid expansion of
the pearl jewelry market. In 1926, when the first official statistics were announced, there
were thirty-three active pearl cultivators with 669,012 pearls produced that year. Ten
years later, in 1936, there were two hundred and fifty-eight cultivators producing
7,071,000 pearls, and in the following year, 1937, these two hundred and fifty-eightcultivators increased production to 10,858, 000. These numbers highlight an explosive25

rise in a decade of both the number of cultivators and total pearls cultured. This
achievement was due to the gradual improvements in the management of oyster culture,whilst building on the early foundations of techniques for nucleus inserting operations.
It is important to highlight the contribution of Japan, whose first pearl culturingindustry contributed to the establishment worldwide of a cultured pearl industry today.

3.

Expansion of the pearl culturing industry

Inspired by the success of Akoya spherical pearl culturing, pearl culturing using otheroyster species, such as Silver-lipped oyster, Black-lipped oyster and freshwater mussels
was also developed. Meanwhile, the areas where pearl culturing was carried out wereexpanded, with many Japanese entrepreneurs challenging themselves to culture pearls
outside of Japan.
3.1

Silver-lipped pearls

Silver-lipped pearl culturing started with a trial by Sukeyo Fujita around Zamboanga of
Mindanao Island in the Philippines, and after this, Silver-lipped pearl culturing was alsoestablished in Indonesia on Buton Island in 1922. Five years later, in 1927, Fujita
succeeded in producing large sized spherical pearls, commencing mass production in
1930. His pearl culturing business grew thereafter, with production reaching 5 Kan (18.8kg) by 1936. However, in 1941, when the political situation worsened due to the threatof the Second World War, all employees and their families were forced to evacuate areas
in South East Asia. After the War, pearl culturing resumed in Burma (present day
Myanmar), with culturing subsequently expanded to the Philippines, Australia andIndonesia.26
3.2Black-lipped pearls

In 1914, Mikimoto began Black-lipped pearl culturing in Okinawa’s Nakura Bay on
Ishigaki Island. At a later date, the farm was moved from Nakura to Kabira Bay due toheavy damage by a typhoon. In 1923, Mikimoto opened another farm in Koror, Palau
Island. Similar to the experience on the blossoming Silver-lipped pearl culturing industry,
his activities were forced to close due to the worsening political situation and outbreakof the Second World War. After the War, pearl culturing resumed in Okinawa in 1951. Atthat time there were several companies attempting to culture black pearls, but all of
26

them ended in failure. In 1953, Ryukyu Pearls Co. started culturing in Kabira Bay andafter much adversity, finally succeeded in producing one hundred and twenty-three
beautiful, large spherical pearls with good lusters. Thereafter, the company produced
high quality pearls by improving their culturing techniques and increasing oyster
production by hatchery breeding. Entering the 1980’s, however, French Polynesia(Tahiti) started full-scale mass production, and since that time the center of the world
market in black pearls has shifted from Okinawa to Tahiti.26
3.3

Freshwater pearls

Freshwater pearl culturing went into full swing with culturing experiments by Masayo
Fujita using ‘Karasu-gai’ (Cocks Comb, Cristaria plicata) at a research laboratory
belonging to Kyoto University’s Otsu Lake Laboratory in Lake Biwa, Shiga Prefecture,
Japan. The following year, in 1925, thirty-four spherical pearls that had been operated
on in the previous year were harvested from ‘Karasu-gai’. Later, the mussel species usedchanged from ‘Karasu-gai’ to ‘Ikecho-gai’ (Hyriopsis schlegeli). In 1935, freshwater pearl
culturing was industrialized, and full-scale culturing started around Lake Biwa.
Freshwater pearls cultured by ‘Ikecho-gai’ that possessed good commodity value werenamed ‘Fujita Rose Pearls’ and exported to England and France via Shanghai throughIndian merchants. The development of this industry was interrupted, like other pearl
culturing activities, by the events of the Second World War. In 1946, the freshwater pearl
industry resumed, along with an important invention by Seiichiro Uda. Whilst the usual
culturing method had been to make a pearl by inserting a nucleus and a piece of mantle
into a mussel’s body, this was replaced by a ‘non-beaded method’ to make a pearl byinserting only a piece of the mantle tissue into the mantle of a mussel. Since that time,
the freshwater cultured pearl industry has been advanced on the basis of producing nonnucleated pearls.26

4.

Cultured pearl industry after the Second World War

4.1

Export industry

After the War, the Japanese pearl industry gradually resumed its activities from 1949
due to loosening in that year of restrictions on pearl trading by the Allied GHQ (General
Headquarters). In that same year, the present-day Fisheries Law was established, andbecause of measures in specific districts to allocate demarcated fishery areas for pearl
27

culturing and mother oyster breeding, the industry rapidly recovered a smooth
production line. Serving the huge demand for cultured pearls in the American market,
the industry rapidly expanded, growing even larger than before the War. The Japanese
government, recognizing that cultured pearls were a principle export which contributed
to the acquisition of foreign currency, protected the Japanese pearl industry by
establishing the “Pearl Culture Industry Law” in 1952.
The Law consisted of the following five pillars: publication of target amounts of pearl
oysters used for nucleus insertion, inspection of pearls for export, assistance for pearl
oyster production, the establishment of the Pearl Culture Industry Council and theestablishment of the National Pearl Institute. Under these robust protections along withother national policies, the Japanese pearl industry expanded exponentially on the basisof its export trade. As for the inspection of pearls for export, two Government Pearl
Inspection Offices to uphold the pearl inspection rules of the Law were opened in 1952,
one in Tokyo and the other in Kobe. To maintain confidence in Japanese cultured pearlsaround the world, the Government Inspection Offices classified all pearls for export aseither ‘High (H)’ or ‘Low (L)’ so that they could regulate exports on low-quality pearls.
Around this time, a National Pearl Institute was established in 1955 in Kashikojima in
Mie prefecture. This was a unique research organization dedicated to research on pearl
and pearl culturing, which produced best practice documents in a series of ‘National
Pearl Reports’. With the National Pearl Institute at its center, pearl research wasvigorously conducted at universities, as well as private research laboratories. Thesenational policies, advancing quality and efficiency in production, increased theconfidence in Japanese cultured pearls overseas. At each pearl farm, as the materials
and equipment modernized, levels of efficiency increase so much that there was a rapid
spike in pearl production. From 1955 to 1965, total pearl production in Japan increased
from roughly 6,500 Kan (24.5 t) to about 30,000 Kan (114.1 t). Of this total, exports in
1955 stood at around 5,000 Kan (18.7 t) and rose to approximately 22,000 Kan (82.5 t)
by 1965. The production and sale of distribution expanded nearly five times more in ten
years.
However, uncontrolled rapid production to meet the demand of the market caused
increased oyster mortality, conspicuous degradations in quality and decreased yields,
which impacted and deteriorated the value of cultured pearls on the market. Meanwhile,a worsening of environmental conditions and lowered productivity by overcrowding
28

oysters was coupled with an increase in production costs stemming from these causes,
which put severe pressure on the management of pearl culturing farms. As a result, by
1969, a flow of low-quality pearls in the market made overseas buyers anxious anddistrustful, discouraging them from making purchases. This was a major turning point
where the Japanese cultured pearl industry, which had boomed till that time, suddenly
plunged into a major decline.28 Despite the fact that there were increasing calls tostabilize production and exports, the situation in the industry had already become too
chaotic and it became utterly impossible to prevent the Japanese pearl industry fromspiraling into chaos. With bankruptcy declared by many pearl dealers and a contractionof business massively reducing their workforce, the government and business sector
could only recover the industry by two key measures: adjusting the storage of excess
pearls and controlling production by the ‘Pearl Culturing Temporary Measurement Law’.
In 1971, this severe depression finally came to an end, but it left serious after-effects on
the pearl industry in Japan.
4.2

Expansion of domestic demandWith this depression as a turning point, many pearl dealers who had previously largely
dependent on exports, headed for expansion into the domestic market in Japan. Major
export and manufacturing traders strengthened their domestic sales departments by
opening retail shops on busy streets or arcades in large and middle-sized cities in Japan,
concentrating their efforts on partnerships with department stores. Other traders put
their energy into job-area sales, training people working for them to increase sales
through exhibitions. In Mie, Ehime and Nagasaki prefectures, which are still important
pearl producing areas today, cultured pearls were sold as souvenirs by pearl cultivatorsand brokers who had had to change their job. Through these efforts the domestic market
expanded to make up about one third of total pearl sales.
Due to the division of labor for pearl oyster breeding and pearl production, the efficiencyof the industry increased, and by the latter half of the 1980s to the beginning of the 1990s
overall production and domestic market sales expanded dramatically. During the 1980s,
however, production gradually reduced because of the unstable climate and conditions
for pearl farms. This was compounded by a change of sea environment and worsening offarm conditions due to increased fish culturing. As a result, oyster mortality increased
and pearl quality notably degraded. Nonetheless, the decline in productivity wascompensated by an increase in quantity. Unfortunately, during the 1990s, two new29

unprecedented incidents occurred. The first was an unexplained mass Akoya oyster
mortality in Mie prefecture in early 1990, with a second mass mortality of oysters again
in 1992 in Ago Bay. A subsequent study identified a new dinoflagellate plankton,

Heterocapsa circularisquama, as the cause of death. This plankton spread to the innerbays of seas in the West of Japan, threatening oyster culture all the more. In the latter
half of the 1990s across all pearl culturing areas in Japan, there was another incident,‘Akoya oyster disease’ where the color of Akoay oysters’ meat changes to red and theoyster dies. This unexpected cause of death, which started in farm areas in Ehime
prefecture, was a disease which spreads throughout all Japanese pearl culturing sites
within three years. So significant was this damage, that it severely rocked the
management of pearl farms and decreased production dramatically. It took a further
study after this crisis to identify this infectious disease. Consequently in 1999, theproduction of pearls deceased to 6,500 Kan (24.5 t), the same level as that in 1955.
Prior to this, the National Pearl Institute, the only national-level specialized pearl
research organization in the world, had ceased to exist in 1979 by unifying with the
National Research Institute of Aquaculture. This meant that there was significant
confusion surrounding pearl production measures to control the rampancy of the disease.
Moreover, in 1997 the ‘Act on Provisional Measures for the Adjustment of Pearl Culture.’
was abolished, and the ‘Pearl Culture Industry Law’, which had supported the Japanese
pearl industry for forty-six years from 1952 to 1998, was abolished on January 1, 1999.
Accordingly, hidden problems, mainly globalization of the industry and liberalization,
bubbled to the surface, and rapid worldwide pearl production and distribution wereaccelerated. As a result, Japan’s prominent status in the global pearl industry was
rapidly weakened, and the high reputation and value of cultured pearls that Japan had
built with Akoya at its center was dramatically damaged.
4.3

Globalization of the industry

The globalization of the pearl industry had been gradually expanding despite therestrictions of the Pearl Culture Industry Law. After the expiry of this Law, however, theglobal expansion of the industry rapidly progressed. Previously, pearl culturing overseas
had been restricted by a section of the Law called ‘The three principles for the overseas
pearl industry’. This was established to maintain the gem value of South Sea cultured
pearls and protect Japan’s original culturing techniques. This policy released by the
Fisheries Secretary stated that:30

1. Pearl culturing techniques shall not be disclosed to the public.
2. All cultured pearls should be exported to Japan, and Japan will obtain exclusive
marketing rights.
3. The extent of production shall be controlled according to the variety of pearl and typeof culturing.
As part of this policy, a prohibition on Akoya oyster pearl culturing in foreign countries
was included.29
After the abolishment of the Law, knowledge of pearl culturing techniques wastransferred abroad, and pearl culturing developed local capital as technicians began
applying these techniques. Not only pearl culturing, but also pearl processing andtreatments, and even nucleus manufacture had been globalized. Accordingly, thesystems of values, which had been originally established by standards for Japanese
Akoya cultured pearls was diversified, and other countries have since cultured,
processed and treated pearls by their own valuation scales. In addition, many pearls
produced in foreign countries were sold without being inspected in Japan.
Liberalization meant abolition of the regulation established by the Pearl Culture
Industry Law. The most prominent was the withdrawal of export restrictions. Until thattime, only pearls that passed the Japanese government inspection based on the Law
could be exported. Since the abolition of the Law, however, any quality of pearl could beexported without inspection. Concurrently, in Japan it became possible for businesses
which were previously excluded by the Law’s regulations, to enter freely into the pearl
industry, driving a rapid multiplication of pearl values and quality standards, with sales
rapidly accelerating in many directions.

5.

Prospects for the cultured pearl industry today

Today, pearl culturing has a presence in many countries around the world. Pearls arecultured using different species of mollusk, such as Akoya, Silver-lipped and Blacklipped, as well as Triangle freshwater mussels. The cultured pearl industry, which
originated from Japan, has developed into a globally important industry by contributing
to the supply and availability of pearls, advancing culturing techniques and influencing
pearl jewelry fashions and designs. In 2016, the Pearl Promotion Law was establishedto encourage the sustainable regrowth of the cultured pearl industry by focusing on the31

protection of biological resources and environmental preservation. The cultured pearl
industry has now entered a regenerative phase to develop a revolutionized pearl culture
and jewelry industry in Japan today.
5.1

Cultured pearls as jewels

In recent years, in response to intensive change to the aquatic environment of pearl
culturing farms, it has become more important than ever to refine culturing techniques
by applying rigorous scientific knowledge and information to optimize culturing
management.
In many countries outside of Japan, such as Australia, China and French Polynesia(where pearl culturing is a particularly important industry), pearl research has become
increasingly robust with the latest gene research in the life sciences, and studies on
pearls in molecular biology making remarkable progress. With this in mind, Japan, once
the world’s leading cultured pearl industry, has revised the importance of conducting
research on pearls. In 2011, a study by the University of Tokyo and others to investigate
genes relating to pearl formation, identified a vast number of novel gene candidates, andby building up this research substantial progress has been made on understanding how
nacre is formed at the gene level. Furthermore, in 2012, The Okinawa Institute of
Science and Technology Graduate University (OIST), along with other research groups,
became the first research unit in the world to successfully provide a complete gene
analysis of the Japanese Akoya oyster. Through a return to increased research on thebasic structure and process of pearl production, the science and technology for culturing
pearl is again making rapid progress.29
For the sustainable development of pearl culturing based on a symbiotic relationshipwith the natural environment, research on biological resources and environmental
conservation is also becoming an important theme. To ensure the stabilization andimprovement of the cultured pearl industry’s standards, it is important to cooperate withvarious research sectors, and thus a number of industry-government-university
partnership have been created. Through this cooperation, there is a strengthening ofwork between production bases and research organizations, so that problems from thefield are scientifically solved, promoting the scientific management of pearl culturing
more widely.

32

Pearls are biominerals produced in living mollusks during the course of their naturalactivities. Today, most pearls distributed in the world, rather than being formed througha rare accident of nature, are almost entirely cultured pearls produced in nature byhuman intervention. Consequently, the term ‘pearl’ has now come to refer more generally
to ‘cultured pearls’. Pearls are gems born in a stable natural environment maintained byan ecosystem involving the living activities of various creatures. In short, they are thevery symbol of a gem of life born in the natural environment. It can be said that cultured
pearls are gems living together with human beings, with their beauty and value closely
related to the environment in which we live. For the sustainable development of cultured
pearls, it is important to understand the true value of cultured pearls and share thisvalue with the world. This is a role that Japan – where the cultured pearl industry firstgrew – has taken on today.
5.2

Promotion of Pearl Jewelry Culture

In the recent Pearl Promotion Law, the ‘Promotion of Pearl Jewelry Culture’ is one of its
stated aims. Pearl jewelry culture is generally understood as the customs relating tojewelry used for fashionable bodily adornment. This culture has existed since European
royalty and titled nobility of old used rare, natural pearls abundantly as decoration on
clothing and ornaments. Pearls, however, have existed through time not as mere
ornaments, but have deeper symbolic cultural significance. Attitudes towards Japanesenatural pearls in particular were strongly influenced by religious (Buddhist, Shinto) andagricultural practices that influenced a particular set of customs using pearls: they were
donated for religious offerings, groundbreaking ceremonies, soul repose for the dead, andalso used as medicine.
From the latter half of the 19th century to the first half of the 20th century, cultured pearls
invented in Japan, rapidly spread to the global jewelry market, transforming pearl
jewelry culture which had at that stage developed from the era of natural pearls. Those
who culture pearls are connected to the natural environment, paying homage to pearlproducing oysters and nature by raising these living creatures. Thus, cultured pearls
have been favored as a gem symbolic of the joint action of humans working with nature.
Over time, cultured pearls, which have been exported to countries all over the world,
have enabled a new jewelry culture to blossom. As substitutes of natural pearls, cultured
pearls are not only loved by a privileged elite, but they are also enjoyed by ordinary33

people, using them routinely as part of their daily adornment. The quality anduniformity of cultured pearls has thus enhanced the diversity of designs for these refinedornaments, so that they can enrich the cultures of everyday life for people all over theworld.
In Japan, more so than other countries overseas, it is common for Akoya cultured pearls
to be mainly worn as jewelry for formal occasions such as ceremonies and celebrations.
There was a time that in Japan the most popular jewel for engagement rings was Akoya
cultured pearls. The reason being that not only were these pearls affordable, but they
were also associated with sentiments of loyalty, oath, love purity and happiness. Pearls
are gems that inherit a feeling of ‘life’ as their symbol. Reviving once again the pearl
culture of Japan, the world history of pearl culturing and the essential values of pearls
will lead to the creation of another new pearl jewelry culture to contribute to lives theworld over.
The establishment of the Pearl Promotion Law aims to revive the meaning, status andvalue that cultured pearls once held. To share pearl jewelry culture the world over,Japanese cultured pearls should strive to enhance the intrinsic and extrinsic qualities of
pearls, elaborating on their history, story, dreams and role in new fashions, whilst
endeavoring to work in harmony with nature and the environment.

6.

Footnote references1.

⻄川藤吉．真珠．動物学雑誌．1904；15：51-67，129-140，203-214．

2.

Kunz G. F and Stevenson C. H．The Book of The Pearl. New York The Century Co .
1908.

3.

松井佳一．真珠の事典．北隆館 1965．

4.

Nagai K．A History of the Cultured Pearl Industry．Zoological Science 2013；30:783793.

5.

藤田政勝．真珠養成学.楽水會 1923：1-34，44-50．

6.

Réaumur R F．Observations sur le coquillage appellé Pinne marine ou Nacre de perle,à l'occasion duquel on explique la formation des perles. Mémoires de l'Académie desSciences 1717：177-194．
7.

Hessling Tv．Über die Ursachen der Perlbildung bei Unio margaritifer．Siebold undKölliker,Zeitschrift für Wissenschaftliche Zoologie .1858；9：543-546．
34

8.

Hessling Tv. Die perlmuscheln und ihre perlen. Wilhelm engelmann Leipzig 1859.

9.

松井佳一．真珠の成因説に関する研究．日本水産学会誌 1958；24：402–406

10. Jameson H L. On the Origin of Pearls. Proceedings of the Zoological Society of London
1902;1:140-166.
11. Boutan L. L'Origine réelle des perles fines. Comptes Rendus de l'Académie desSciences 1903; 137:1073-1075.
12. ⻄川藤吉．一個の貝より生ずる真珠の数．動物学雑誌 1907；19(3)：42-57．
13. Dakin W J．The Origin of Pearls, Pearls． Cambridge at the University Press 1913：
pp91-116．
14. 小串次郎．真珠の研究．伊藤文信堂 1938：pp85-93，pp123-134．
15. 磯和楠吉．真珠成因研究の史的概観．国立真珠研究所報告 1956；1：47–56
16. Rubbel A ． Über Perlen und Perlbildung bei Margaritana margaritifera nebst
Beiträgen zur Kenntnis ihrer Schalanstruktur． Zoologische Jahrbücher，Abteilung

für Anatomie 1911；32：287-366．
17. Jameson H L．Studies on Pearl-Oysters and Pearls．The Structure of the Shell andPearls of the Ceylon Pearl Oyster Margaritifera vulgaris (Schumacher)：with an
Examination of the Cestode Theory of Pearl-Production. Proceedings of the ZoologicalSociety of London 1912：260-358．
18. Alverdes F ． Versuche über die künstliche Erzeugung von Mantelperlen bei
Süßwassermuscheln. Zoologischer Anzeiger 1913；42：441-459．
19. Haas F．Die Perlen. Akademische Verlagsgesellschaft m.b.H.Leipzig (1931,1933)（Translation; Hayashi K）Jinnou Press 1972：pp87-97．
20. 久米武夫．宝石学．風間書房 1953：pp625-644.
21. Bouchon-Brandely G．Sur La Péche et la Culture des Huîtres Perlières à Tahiti;Pêcheries de l'Archipel Tuamotu． Imprimerie du Journal Officie 1885；31：4-73．
22. Boutan L．Production artificielle des perles chez les Haliotis. Comptes Rendus del'Académie des Sciences 1898：pp77．
23. 藤田輔世．科学知識．1928；8（10）：pp1064
24. 永井清仁．養殖真珠研究の歩み．真珠研究の今を伝える．恒星社厚生閣 2020：1-22．
（in press）
25. 真珠産業史．真珠産業の誕生．日本真珠振興会 2007：pp19-34．
26. 赤松 蔚．養殖真珠の発明と真珠産業の発展（１）．ジュエリーコーディネーター． 2018；
83：1-8．
27. 阪谷芳郎. 御木本養殖真珠調査報告書．帝国発明協会 1926：1–8．
28. 丹下 孚．日本真珠産業論．真珠新聞社 1986．
35

29. 丹下 孚．変貌する真珠産業．真珠新聞社 1993．

36

Chapter 3

Basic stance of the quality standards

1.

Assessing pearl quality

1.1

BackgroundIn 1928, in order to maintain the reputation of the pearl, a domestic industry
organization ‘Dai Nippon (Imperial Japanese) Pearl Association’ was established. To
eliminate low-quality products unworthy of the title ‘pearl’ from the market, they obliged
members of the industry to present all the pearls they had cultured so that their quality
could be evaluated by two or more appraisers. As a result, pearls which had nacre that
did not reach the standard thickness, had no pearl luster and/or had an extremely
irregular shape were rejected and prohibited from sale.
In 1932, the Association was reorganized, and Japan Cultured Pearl Fisheries
Association was born. This Association closely monitored the commodity standards for
pearls, ensuring a more thorough inspection and disposing those that had been rejected.
The Association also prepared other regulations concerned with inspections, arranging
for exclusive inspectors to carry out this task. The process obliged the producer to reveal
the results of this inspection to others in the supply chain, and pearls that were
substandard were prohibited from sale. The pearls were rejected if they presented with
one or more of the following characteristics:
1. It is below the standard nacre thickness.
2. It has a severely deformed shape.
3. It has no luster.
4. It possesses little practical value.
5. It is anticipated that it would be unfavorably received on the market.

Rejected pearls were divided into two groups: 1. for disposal and 2. as reserves. Pearls
for disposal were burned by the Association. Reserve pearls on the other hand, whichwere forbidden from use as merchandise in their original state, were acquired by the
Association to determine their fate. At that time, however, the world was reeling froman economic depression, and the demand for pearls as luxury goods was decreasing day
by day. Nevertheless, thinly coated cultured pearls flooded the world markets through37the hands of unscrupulous dealers. Seeing this situation, Kokichi Mikimoto wasconcerned that this would hurt the reputation of cultured pearls and damage prospects
for future trade. To set an example of good quality pearl sales therefore, he publicly burnt
36Kan (135kg, current value 48,000 JPY) of cheapjack pearls as ‘creation of the pearl’ infront of Kobe Chamber of Commerce. Thus, cultured pearls before the Second World War
were rigorously checked according to benchmark quality standards for nacre thickness,shape, luster and color, with special attention directed towards evaluating the nacre
thickness of a pearl.
1.2

The Pearl Culture Industry Law

It can be said that government inspection of pearl exports provided an opportunity torate pearl quality in terms of shape, nacre thickness, flaw, luster and color. Thesestandards were protected by the Pearl Culture Industry Law which was established in
March 1952 to encourage the stable growth of the pearl industry.
According to a government ordinance of the Law, the ‘Pearl Inspection Rule’, all pearls
for export underwent a classification of ‘H’ (high) and ‘L’ (low) at national pearl inspection
offices; and only (H) class pearls could be exported. Although this inspection was
intended to mainly classify pearls according to categories (H) and (L), in practice thesecategories involved five grades with the upper three grades assigned to (H) and the lower
two grades (L). These grades were determined by six criteria: shape, nacre thickness,gloss, flaws (natural or processed) blemish and finish.
The colors of pearls were divided into white, silver, pink, yellow, gold, green, blue andblack, with each color assigned one of the above five grades. However, this assessment
did not reflect the final quality evaluation. In addition to the above mentioned quality
criteria, elements of surface roughness, defective dyeing, burnishing (silicon and coating),
thin coating, muddy nacre, cracks (subdivided into nucleus cracks and nacre cracks),
breakages and flaws were also checked. Details of three (H) Class (Class I-III) and two(L) Class (Class Ⅳ-Ⅴ) are provided in the Guideline for compiling results of pearl export
inspections as follows:38

Guidelines for compiling results of pearl export inspections
Grade

Inspection criteria

Ⅰ

Ⅱ

Very thick nacre (substantial

Ⅲ

Thick nacre

Ⅳ

Slightly thin nacreThin nacre

Nucleus layer visible

Ⅴ

thickness ）1. Nacre thickness

Example: Mid-quality pearl

Example: Mid-quality pearl

Possible to see the nucleus layer

cultured over 3 years

cultured over 2 years

a little

Round

Semi-roundSemi-baroque

Spherical

Spherical with a little distortion

Mild distortion, some protrusion

Example: ball-shaped

Example: egg- shaped

3. Luster

Strong vibrant luster, deep gloss

Good luster

Ordinary luster

No luster

4. Flaw A (natural)

Nil

Slightly spotted,

Middle spots

Heavily spotted

Almost conspicuous

Somewhat conspicuous

2. Shape

B (processed) As above
5. Spot and mud

6. Finish

Grade

Baroque
Heavy distortion, significant

Nil

protrusion
Nil

Nil

As above

Nil

A few

Many

Very many

Excellent processing techniques

Excellent processing techniques

Good processing techniques, slight

Rather poor processing

Excellent matching of rhe srand

Good matching of the strand

discord in matching the outer edge

techniques, and mismatchingfrom the main part of the strandof the strand

Reconized for ordinary ornaments

No value as pearl

Recognized as a gemstone

Nil

Recognized for quality high

Nil

Nil

Nil

ornaments

2.

Quality criteria for pearls

Quality evaluation of pearls is carried out at every stage from culturing, processing andtreatment, wholesale, export and appraisal. Although the evaluation standards vary ateach stage, quality criteria are evaluated according to roughly the same scales. The
criteria of shape, nacre thickness, flaws, luster and color are described in the following
section. Whilst size is not a quality criterion, it does influence the overall price. In caseof necklaces, matching is added as an additional quality element.
2.1

Shape

As for the ideal shape, perfectly round pearls are typically highly evaluated. The reason
for this may stem from the rarity of round natural pearls, a trend that remains relatively
unchanged since cultured pearls were invented. Historically round pearls called Happokorogashi, which roll in every direction where there is even the slightest slanting surface,have been highly valued. The reason why the shape of a cultured pearl is rarely perfectlyround despite having a round nucleus, is because pearl oysters typically do not secretenacreous substances evenly, and organic matter is sometimes included in the formationof a pearl. When the culturing period is longer, the rate of production of off round pearls
becomes especially high because nacre thickly accumulates around the nucleus. As aresult, wholly round pearls with a thick nacre are naturally those that receive the39highest valuation. Recently, however, as the number of thinly nacred, round pearls
produced under a short culturing period has increased, the quality of round pearls is notnecessarily high. In fact, some pearl dealers insist that transformations in the shape ofa pearl are proof of the thickness of its nacre. As such, somewhat misshapen pearls witha thick nacre are more highly regarded than thinly coated, round pearls.
The shape of pearls is roughly divided into round, semi-round, semi-baroque and baroque.
In the case of Silver-lipped and Black-lipped cultured pearls, other shapes such as drop,
button, oval and circle are also seen. Circular Akoya cultured pearls, however, are hardly
ever produced.
2.2 Nacre thickness
As the title indicates, this term refers to the thickness of a pearl’s nacre. A visualassessment of the thickness of nacre is closely dependent on the color and luster specificto each pearl. The thickness and quality of nacre also has a close relationship with overall
durability, an important factor in assuring a pearl’s status as a jewel. Nacre thickness istypically determined by the length of culturing period. Although there are otherinfluences, such as the characteristics of the pearl oyster and environment of the pearl
farm, in general he longer pearls are cultured, the thicker their nacre becomes. As nacre
is composed of thousands of thin crystals of calcium carbonate, the quality of thissubstance greatly affects a pearlʼs luster and durability.
The thickness and quality of nacre varies according to pearl oyster species. Generally,
the nacre thickness of Akoya cultured pearls is thinner than Silver-lipped and Blacklipped cultured pearls. However, Akoya cultured pearls have a finely textured nacre,
which produces a specific luster and iridescent color. Nacre thickness may sometimes bemeasured by X-ray and ultrasonic devices, but usually it is assessed by the naked eye. It
should be noted that the nacre thickness standards vary from trader to trader. In thecase of Akoya cultured pearls, nacre thickness is divided into three main categories, thick,middle-thick and thin.
When the crystal structure – a core component of nacre – maintain a uniform thickness,
it contributes to the production of the most beautiful color iridescence and an excellently
smooth surface for a pearl.

40

2.3 Flaws
Naturally, flawless pearls are highly valued, since flaws reflect a damages to the surface
beauty of a pearl. There are many reasons that flaws occur during culturing, but the
precise reasons for them are not well understood. It is generally accepted that a pearl
will contain at least one or more flaws. There are two types of the flaw, a ‘natural flaw’
formed at the culturing stage and a ‘processed flaw’ which occurs after it is harvested
during processing, treatment and handling.
The initial evaluation of flaws involves deciding whether it is either a natural orprocessed. The subsequent assessment takes into account the number, kind, size andlocation of the flaw(s). In the case of Akoya cultured pearls, flaws are roughly divided
into flawless, small, middle and heavy. As there is no fixed evaluation system forassessing flaws, dealers often do so according to their own standards, some groupflawless and small flaws together, others divide flaws into seven to eight grades. All such
evaluations are carried out by the naked eye.
2.4 Luster
An evaluation of the luster of a pearl is based on a combined assessment of luster andtransparency, as well as special optical properties, which occur when light is diffused andrefracted to create pearl iridescence. The quality of luster is determined by the thicknessof nacre, and the uniformity and transparency of the crystals that compose it.
Nacre thickness has a close correspondence with the extent to which pearls shine.
Recently, with the developments in polishing techniques, shining pearls with a mirrorlike surface are appearing on the market. However, this is not true deep, subtle sheen
originally possessed by a pearl, it is but a mere surface reflection.
When a pearl is composed on layers of the large, compact and beautiful tabular aragonite
crystals, a particular luster is created by an optical action of light. However, even if nacre
is satisfactorily thick, a pearl cannot possess a good luster if the crystal layers are thick,and aragonite crystals are small and irregularly arranged as this causes too much inner
diffusion of light.
The characteristics of nacre are greatly influenced by the quality of management of the41culturing phase. In the case of Japanese Akoya, a temperature drop leads to a growth ofbig, compact and beautiful aragonite crystals, improving the luster of a pearl. Pearlcultivators call this action ‘Kesho-maki’ (makeup coating). The reason the harvest is
carried out in winter is because nacre’s crystal structure produces the finest and mostbeautiful luster and iridescent color during this season.
There is no unified standard for luster. Some dealers divide luster into three categories:
lustrous, middle luster and lusterless, whilst other dealers divide this even more. The
evaluation of luster is often combined with an evaluation of nacre thickness. The extent
of iridescence of color also affects the evaluation of luster. Assessing luster is a skilled
job that requires an ability to differentiate between mere surface shine made bypolishing and the deep, internal luster specific to each individual pearl.
2.5

Color

As for the color of a pearl, the first assessment is to decide whether it is natural or treated.
In the case of Akoya cultured pearls, there are five different colors: natural color without
any treatment except polishing, non-tinted color only altered by bleaching, tinted color
by slight alteration using pigments, dyed color using dyestuff and colors created by theaddition of other treatments.
The natural color of a pearl is a combination of a main color (body color) elaborately
mixed with iridescent color and body color. Iridescent color is produced by astrengthening and weakening of light of a certain wavelength. A pearl creates color byreflection, refraction and iridescence of light in the stratified nacre layers. As iridescentcolor has a close relationship with luster, the jewel value of a pearl can be enhanced or
decreased depending on this iridescence.
The body color, on the other hand, is decided by tiny pigments contained in the organic
matrix of a pearl. There are yellow pigments in Akoya and Silver-lipped cultured pearls,
black pigments in Black-lipped cultured pearls and orange and purple pigments in
Freshwater cultured pearls. In pearl culturing, color is controlled to a certain degree. In
Akoya pearl culturing, for instance, the appearance of yellow pearls is minimized byusing tissue from peal oysters that contain as few yellow pigments as possible. On theother hand, in Silver-lipped pearl culturing, golden pearls are purposely produced byusing oysters that contain more yellow pigment.
42

In addition to iridescent color and body color, there are other colors caused by organic
matter, which are called blemishes. Blemishes can form between the nacre and nucleus,
or between the layers of nacre, tingeing it with a brown-black color. However, when ablemish is seen through the nacre, pearls can appear blue. Pearls with this blue color
are sold in the market under the name ‘natural blue’.
At present, there is no unified standard nomenclature for pearl colors because of theabove-mentioned complexities, so dealers often use their own names to describe the colorof pearls. In the case of Akoya cultured pearls, pink, white, green, cream, gold and blue
are common names. For pearls other than Akoya, names such as peacock, pistachio,
cognac, wine and champagne are also seen.
There is no rule that privileges one color over another to decide which is best. The colorof a pearl may be highly praised or not according to its rarity, current fashions, anddifferences in national and regional preferences. The most important thing to remember
is that pearl color ultimately depends upon individual tastes. Though the quality of color
was assigned one of five grades in the same manner as other criteria, the export
inspections carried out for pearls did not consider ‘base color’ a determining factor in the
final quality evaluation.

3.

Quality inspections of pearls

3.1

Domestic quality inspections

Once there was an attempt in Japan to apply the same standards of inspection for export
pearls to those intended for the domestic market. However, this presented an immense
challenge as the task for export inspection had been to rate pearls as either high (H) orlow (L), whereas domestic inspection had to be graded, rather than simply assigning a
rating of (H) or (L).
As domestic inspections of pearls are particularly geared towards the consumer, theranking of quality is particularly imperative. Each quality criteria of a pearl (shape,nacre thickness, flaws, luster and color) are not treated as independent, but are closely
related to each other. For instance, although a shape may be poor, if its nacre thickness,luster and color are good, the pearl is highly evaluated regardless of this defect. Recently,
43there has been a tendency to say that if flawed pearls produce a good luster, they can be
assigned a high value despite these flaws.
At present, the biggest challenge for valuing pearls on the market is that different
appraisers have judged each quality criteria individually, using their own evaluation
standards to produce a final result. Whilst the highest quality pearl (which all appraisers
rank at the top) and the lowest quality (L class of the pearl export inspection) can beeasily classified, when it comes to middling quality pearls the situation becomes more
complex. As the exact classification system differs according to the values ascribed by
the individual dealer, this presents a constant challenge for standardizing pearl
appraisals.
Treatment is one further aspect that must be considered in pearl quality inspection.
Further developments in, and globalization of the treatment techniques mean thatpearls are often widely treated overseas. Therefore, inspections must be carried out witha consideration of the treatments used to determine the extent to which pearls aredamaged and how such treatments affect the quality of a pearl.
3.2

Quality inspections of pearls

During quality inspections, appraisers judge in the first instance whether the pearl
tested possesses value as a jewel. This judgment is based on the high (H) classestablished by the past export inspection standards. When a pearl is judged low (L) class,
it is rejected if it has one or more of the following characteristics.
Nacre thickness: The nacre is so thin it is possible to see the layer of the nucleus (socalled ‘streak’). Severely and partially thin nacre with an abnormal ‘luster’ is found onthat spot.
Shape: Extreme ruggedness that spoils the beauty of the pearl. Noticeable circles that
deform the total shape of the pearl.
Luster: A lack of pearl luster. Inclusion of a prismatic layer in the nacre which has a
noticeable aesthetic impact.
Flaw: Extreme convex and concave flaws that seriously damage the surface beauty ofthe pearl (a natural flaw). Serious damage to the inner part of the nacre by treatments(a processed flaw).
Treatments: Serious damage on the surface of the nacre caused by excessive bleaching.
44

An extreme red color of the whole pearl, resulting from dyes remaining in holes, anduneven tint with streaks caused by excessive tinting.
As for pearls which are recognized as jewels by the above-mentioned inspection,
appraisers categorize them according to each quality criterion. However, according to thestandards of Japan Pearl Promotion Society, the individual result of each criterion does
not necessarily reflect the final overall valuation of a pearl. The reason is that, aspreviously mentioned, valuations greatly depend on the appraiser. The Society does not
object to private institutions adopting an integrated approach to overall ratings, but forthe methods by which appraisals are undertaken, a standardized system based on former
Japanese export inspections should be established.
An evaluation scale to provide quality definitions of pearls based on nacre thickness,luster, flaw etc., has been developed according to the former Japanese Government Pearl
Inspection Office system. However, the overall evaluation standards are not fixed, sincenacre thickness and luster are mutually affected, and values assigned to shape and color
depend on individual taste. Therefore, whilst the Society recommends a standardized
evaluation scale to undertake quality criteria inspections, the final judgment is up to theindividual appraiser.
The most important thing when consumers are purchasing pearls is to disclose allnecessary information on the type, quality and price of a pearl to inform their decisionat the time of purchase. If the information offered is not sufficient enough or misleading,consumers will instantly lose confidence in pearls. To ensure a successful future for pearl
jewelry culture, it is important to convey accurate information to customers for thecreation of jewelry, and to offer quality pearls worthy of securing consumer confidence.

45

Chapter 4

Basic stance on processing and treatments

1. Background
Processing and treatments of the pearl are physical and chemical methods to alter shape,
inner structure and weight of natural and cultured pearls, to enhance their latent beauty
and to change their original color and appearance, irrespective of their original
characters.
As for the treatment, it is said that the first treatment in Japan was carried out in 1922
by Yasuie Todo. He started to bleach blemished pearls after he learned that browncolored coral in Italy whitened on contact with oxygenated water. In the 1930s, pearls
were often bleached and substantially dyed, a treatment method described in detail in areport by Toshikazu Horai. In the latter half of 1955, treatment methods for pearls madefurther progress. In particular, bleaching by irradiation using visible light, and dyeing
with dyestuffs dissolved in methyl alcohol widely prevailed as a common method.
Present-day methods have built on these techniques.
1.1

Processing and treatment methods

Specifically, the followings are common processing and treatment methods:
1) Drilling
Using super-steel drills to make cylindrical holes through or into the center of pearls.
2) Cutting (including three-quarter cutting)Cutting a pearl (including three-quarter cutting) using tools such as diamond cutter,etc.
3) Shaping
Changing the surface feature of pearl to improve its smoothness of curves.
4) Polishing
Improving pearl luster by physical and chemical methods, such as barrel tumbling,
animal skin polishing, buffing, high-speed polishing and acid polishing.
5) Gluing
Sticking together cut pearls with adhesive agents.
6)

Filling
Introduction of resins or other substances into the body of a pearl to reinforce its
46

strength and increase its weight.
7)

Coating
Covering the entire surface of a pearl with resin or other materials to reinforce its
strength and improve the color and luster of a pearl.

8)

Thermal processing
Removal of unfavorable colors and/or improvement of luster by heating.

9)

Mae-shori
Soaking pearls in water or organic solvents at either room or ambient temperature
to stabilize the color tone and improve the luster of pearls.

10) Bleaching
Removal of organic matter, stains (stain removal) or pigments (whitening) found innatural and cultured pearls to alter and stabilize their color.
11) Tinting
Slight color alteration of Akoya cultured pearls by the addition of red dyes tosupplement the iridescent color of Akoya cultured pearl naturally possesses.
12) Dyeing
Application of natural and synthetic dyes to natural and cultured pearls to alter
their color and appearance from their original character.
13) Coloration
Application of chemical reagents other than dyes to natural and cultured pearls toalter their color and appearance from their original character.
14) Irradiation
Color alterations made by irradiating a pearl with gamma rays.
15) Modification
Changing the calcium carbonate structure of nacre to a different substance usingchemical reagents such as calcium fluoride for reinforcing the strength of a pearl.
16) Cultured blister (with lid) processing
The nucleus and impurities are removed after cutting away cultured blisters fromthe attached shell, filling the vacant part by removal with resin etc., and attachinga lid made of shell nacre.
17) Cultured blister (with shell) processing
Cultured blisters are cut out together with a part of the attached shell, for shapeprocessing.

2. Treatment disclosures47

As processing and treatments from 6) to 14) change original characteristics of naturaland cultured pearls, such as color, luster, appearance and weight, they have to disclose
their methods. Treatment 16) should also be disclosed since modification alters originalnacre characteristics composed of calcium carbonate to different calcium fluoride,
deviating from definition of the pearl. In the past, the Japanese Government pearl
inspection of pearls for export decided only to disclose treatments for black pearls using
silver nitrate and gamma ray irradiated blue pearls as STB (Scientifically Treated Black).
Other treatments at that time did not need to be disclosed. However, on June 1, 1994,
Japan Jewellery Association and Association of Gemological Laboratories in Japanestablished standards for the definition and nomenclature of natural stones, which
obliged disclosures on the information and background of gemstones. Following thisdecision, Japan Pearl Promotion Society at the 6th Board of Directors on December 6 ofthat same year, also decided to enforce the disclosure of treatments, dividing them into
two categories:
1) ENHANCEMENT
Enhancement involves optimizing the existing beauty and characteristics of a pearl.
Without such pre-existing qualities, enhancement is unlikely to have a significant
impact on the pearl color or its outward appearance. Although pearls are enhanced using
the same techniques, the procedure produces different results from pearl to pearl (notethat enhancement methods include only tinting).
2) TREATMENT
Treatments are procedures to artificially alter the color and appearance of a pearl bychemical and/or physical methods which do not rely upon enhancing the original
properties that a pearl possesses (treatment methods include: color change, coloring,dyeing and irradiation).
ENHANCEMENT
Tinted pearls

Pearls bleached, pearls slightly dyed (colored)
TREATMENTA Treated black pearl

Chemical color changes to Akoya and Black-lipped
cultured pearls (osmic acid and silver salt treatment)

B

Irradiated black pearl

Color changed to black to grey by irradiationC

Dyed blue pearl

Treated with blue dye

DCombined black pearl

Treated by B and C type method

E

Dyed golden pearl

Treated with yellow dye
48

Later, in the United States these definitions were abolished because these were thought
to be too ambiguous, so treated gems were identified according to their treatment name.
Following this decision, in the first edition of the Pearl Standard issued in the year 2000
by Japan Pearl Promotion Society, it was decided that treatments of pearls should bereferred to by the name of their treatment methods.

3. Overseas movements
According to a decision made by Japan Pearl Promotion Society in 1994, there was noneed to disclose enhancements. The background of this decision was based on CIBJO(The World Jewellery Confederation) Pearl Book of 1991 which defined pearl treatments
as follows:

Art 10b) Bleaching of natural or cultured pearls does not need to be disclosed.
c) Regarding cultured pearls, slight alterations of tint (e.g. rose tint) caused bytreatments do not need to be disclosed. Artificial coloration (e.g. stained freshwater
cultured pearls, black treated cultured pearls, etc.) must clearly and openly stated.
However, in accordance with recent great change of pearl processing and treatment
techniques, CIBJO has changed disclosure in Pearl Book 2020 as follows:
4.5.2.2

Cultured pearls requiring general information on treatments

Cultured pearls that have been bleached to produce a uniform white appearance shallhave an asterisk on commercial documents, immediately following the description orname of the pearls that relates to a footnote of equal prominence to the description orname that appears on the same page that indicates that the cultured pearls have been
bleached.
Example……cultured pearls**These cultured pearls have been bleached to remove or change their clour to white.
*Cultured pearls grown in the Akoya pearl oyster are usually bleached to remove
blemishes between the nucleus and the nacre, to change the colour of the nacre or
produce a uniform white appearance.
4.5.2.3

Cultured pearls altered by methods requiring specific treatment declarations
49

Cultured pearls that have been treated by dyeing (5.63), filling (5.69), heating (5.94),
irradiation (5.100), lustre enhancement e.g. “Maeshori” (5.111), oiling (5.143), tinting(5.198), waxing (5.204) and chemically altered (5.38) require specific information on thetreatments to be declared at the point of sale.
Treatment methods:
5.38

Chemically altered

A treatment that changes the colour of a pearl or cultured pearl without the use of a dye.
5.63

Dyed/dyeing

Application of a dye or stain to natural materials or artificial products to alter theircolour.
5.69

Filling

To introduce a substance that occupies the whole or part of a void.
5.94

Heating

To heat a pearl or cultured pearl to a temperature that may alter its appearance.
5.100

Irradiated/irradiation

Exposing pearls, cultured pearls, diamonds, gemstones, synthetic stones and artificial
products to any form of radiation which is controlled wholly or partially by man, usuallyto alter their appearance.
5.111

Maeshori treatment

A multi-part chemical treatment, including exposure to heat and/or light, that
temporarily enhances lustre.
5.143

OilingA process, called ‘decraqueler’, sometimes applied to natural and cultured pearls,
whereby the surface of pearls is soaked in warm oil, to diminish the appearance of cracks.
5.198

Tinting

A treatment which causes a subtle change in colour and/or appearance (often associatedwith bleaching).
5.204

Waxing

The application of a colourless wax or similar products to, or near, the surface of a pearl.
In the United States, on the other hand, it was thought that the definitions of‘enhancement’ and ‘treatment’ were too ambiguous. For this reason, these terms wereabolished, and treated stones were identified by the name of their treatment method.
Afterwards the Federal Trade Commission (FTC) revised FTC Guide on July 7, 2018,50

and the recommendations for disclosure of treatments have been updated in Revised
Jewelry Guide Ⅲ as follows:
Disclosure of treatments
It is unfair or deceptive to fail to disclose that a pearl or cultured pearl has been treatedif,(a) The treatment is not permanent. The seller should disclose that the pearl or cultured
pearl has been treated and that the treatment is or may not be permanent.
(b) The treatment necessitates special care requirement for the pearl of cultured pearl.
The seller disclose that a pearl or cultured pearl has been treated and has special
care requirements. It is also recommended that the seller disclose the special carerequirements to the purchaser.
(c) The treatment has a significant effect on the product’s value. The seller should
disclose that a pearl or cultured pearl has been treated.

4. Establishment of the Standards
Treatment greatly affect the quality of a pearl. As such, in 1995 the Pearl Quality
Establishment Committee of Japan Pearl Promotion Society presented the following
report. It is important that the standards published as part of this report become widely
established industry knowledge.
“Recent treatment techniques have progressed remarkably. Although the Committee
pointed out the problem of excessive treatments, in reality each company merely
copes with problems from experience, such as what kind of treatment effects whatchange to a pearl, and what the limits for treatments are, especially in terms of
pearl’s durability etc. Of course, companies fully understand that they will incurusers’ criticism if they continue to deal in treated pearls that lack durability. Whilst
it can be seen that companies are trying to tackle the treatment problem, at present
the accumulation of scientific knowledge on pearls is more abundant than ever.
Therefore, it is important to continue scientific research which focuses onunderstanding the effects of treatments on pearls, especially the extent to which
they affect pearl’s durability. The methods and standards used for treatments
should be based on scientific research”.

51Chapter 5
1.

Basic stance on pearl inspections and differentiations

Background

Pearl differentiation before the invention of cultured pearl was to identify whether a peal
was true or imitation. Manufacturing technique of imitation pearls were so poor thatthey were easily recognized as imitations with a quick glance. Differentiation of natural
pearls implied appraisal concerning when, where and how the pearl was collected, andby whose hand it was offered in the market.
1.1

Differentiating natural and cultured pearls

The development of cultured pearls gave rise to a new importance on pearl
differentiation. In 1919, when Kokichi Mikimoto started selling his pearls cultured at
his pearl farm in Gokasho Bay, Mie prefecture in London and Paris markets, jewelers
selling natural pearls in Paris were deeply wary of his products. To stem the flow of
cultured pearls, they thus developed a boycott movement starting that “cultured pearls
are imitations”.
Against this, Mikimoto raised a lawsuit for business obstruction, and the so-called ‘Pearljudgment’ was fought in court. At that time, the most prominent pearl experts, Dr.
Jameson of England and Dr. Boutan of France, carefully examined cultured pearls andafter examination, they declared that cultured pearls are true pearls. Dr. Jameson
announced this result in a scientific journal ‘Nature’ in 1921. This could be said to be thefirst moment pearls underwent differentiation. According to the journal, he usedpolarized light and fluoresce with ultraviolet light, and also applied the usual methods
to examine the color and luster of pearls.
When thin slices of pearls were examined by polarized light, cultured pearls could be
easily distinguished from natural pearls because they contained large nucleus madefrom freshwater mussel. However, when it came to differentiation by non-destructive
methods, it was reported that the distinction between natural and cultured pearl bypolarized or other lights was almost impossible.
When they used fluorescence emitted by the irradiation of ultraviolet light, it waspossible to distinguish Indian and Ceylon natural pearls from Japanese cultured pearls,
52

since the former emit blue fluorescence, whilst the latter green. It was reported, however,that the distinction of cultured pearls and natural pearls from other regions was
impossible.
In 1924, the Paris trial was finally settled when the verdict that cultured pearls should
be considered real pearls. After the settlement, various differentiation techniques weretried and tested. It can be easily imagined that at that time it was important todistinguish natural and cultured pearls. To do this, the detection of the nucleus by X-ray
was the most effective methods, but it was not until 1929 that Alexander and Sherwood
used this technique for the first time, and only after 1936 did X-ray become available forpearl differentiation. When Jewelry Research Laboratory of the London Chamber ofCommerce and Industry started regularly using X-ray for pearl differentiation, it was
widely used thereafter.
1.2

Identification by pearl oyster species

Just as making the distinction between natural and cultured pearls is crucial, so too is
the identification of pearl oyster species. In 1965, when Ryukyu Pearls & Co., succeededin culturing black pearls using Black-lipped oysters in Ishigaki Island, Okinawa, they
became the only company in the world to produce cultured black pearls. However, about
ten years before the appearance of true black pearls, silver nitrate treated and gamma
ray irradiated Akoya and Silver-lipped black pearls were already in distribution. To
distinguish treated black pearls from the true pearls cultured by Black-lipped oysters in
Okinawa, methods for identifying pearl oyster species were required.
After various trials, photographic analysis using infrared color film proved effective, andresult reports based on infrared photography were published. Later, an identification
method using spectrophotometers was developed to check a peak of around 700nm
arising from the presence of specific black pigments in Black-lipped oysters. At the sametime, non-destructive analysis of the components of pearls through X-ray fluorescence
had become possible. This was especially useful for detecting the existence of silver toprove whether or not a pearl had been silver-treated.
Japan’s Shosoin Treasure House in Nara prefecture, where 4,158 natural pearls fromthe Nara Period (710 – 784 AD) are preserved, is another example of the importance of
pearl oyster identification. In 1988 and 1989, investigation of these pearls was carried
53

out to identify their oyster species and understand where they had come from. Afterinvestigationbyapolarized

microscope,

spectrophotometer,

fluorescence

spectrophotometer and X-ray fluorescence analyzer, they were identified as natural,seawater pearls from waters around the coast of Japan. At the same time, it was proventhat most of these pearls were from Akoya oysters, though some were natural pearls
from abalone.
1.3

Identifying pearls by place of origin

Today, the methods for identifying pearl oysters are rapidly diversifying. As the pearl
culturing industry had globalized, the same species of oyster has started to be used indifferent pearl farms around the world. Akoya pearls are cultured in Japan, China,
Vietnam and the UAE. Silver-lipped pearls are cultured in Australia, Indonesia, thePhilippines and Myanmar, and Black-lipped pearls are cultured in Tahiti and Fiji. As for
freshwater pearls, they are cultured in Japan and China. Though the same type of pearl
oysters is used in different regions, if culturing techniques and farm environments differ,
there is a significant difference in the quality and characteristics of the pearl produced.
Concurrently, there has been an increasing emphasis on ‘place of origin’ as a brand．
Up till now, identifying pearls by place of origin and oyster species has been almost
impossible as it can only be done by analyzing specific pigments and chemical elements
contained within a pearl. However, with the success in 2012 by Japanese scientists toanalyze the genes of Akoya oysters, there is an increased opportunity for identifying
pearl oyster species and the birthplace of a pearl by examining pearl oysters’ DNA. In
the near future, therefore, it is anticipated that DNA analysis of pearls will become oneof the main methods of identification. There is also another technique to detect traceelements contained in the pearl which is improving processes for determining a pearl’s
origins.

2.

Identification methods

2.1

Magnification

・ The surface of the pearl is magnified about one hundred times to identify whether itis true (natural or cultured) or imitation by determining the surface pattern which ischaracteristic of true pearls. Pearls from bivalves or snails are also identified by their54surface pattern characteristics. In the case of Conch natural pearls, a particular‘flame structure’ can be seen on their surface.
・ The surface of a pearl is observed by stereomicroscope and metallographic
microscopes to see if it has undergone coating and/or excessive polishing. When
pearls are coated or have been excessively polished, the surface pattern becomes
unclear of disappears entirely.
2.2 Inner structure inspection
・ Fiber optic light and X-rays are used to inspect whether a pearl is natural or cultured.
As there are cultured pearls with no nucleus, such as freshwater and ‘Keshi’ cultured
pearls, attention must be paid to the fact that non-nucleated pearls are not always
natural.
・ Strong condensed light from a fiberscope is irradiated onto the pearl to inspect cracks
in the nucleus and nacre
・ X-ray apparatus is used to examine nacre thickness, the inner state of a pearl andthe type of nucleus it contains.
2.3

Spectrometric analysis

・ Specific wave absorptions of around 400, 500 and 700nm are measured to identify
Black-lipped cultured pearls. Akoya non-treated cultured pearls have very specificabsorptions at 407, 430 and 460nm. Absorptions between 360 and 430nm are seen foryellowish Akoya and Silver-lipped cultured pearls, and specific wave length
stemming from polyene pigment is also used for the identification of Conch natural
pearls.
・ Absorption changes near 280nm caused by conchiolin proteins in pearls are also
inspected to see if they have undergone treatment. As for tinted, dyed and colored
pearls, they can be identified according to their absorption characteristics to check
whether the color is original or has been artificially added.
2.4

Fluorescence analysis

・Using black light, ultraviolet detectors, fluorescence spectrophotometers andfluorescence microscopes, fluorescent substances contained in pearls and added byexternal treatments can be analyzed to identify pearls.
55

・ Mabé, rainbow Mabé (Pteria sterna) and Black-lipped cultured pearls containporphyrin pigments that emit vivid strong red fluorescence with a peak around 620
nm. This characteristic is checked by fluorescence spectrophotometers and black
light to identify the pearl oyster species.
・Changes in fluorescence caused by the conchiolin protein in pearls can be analyzed
by black light, fluorescence spectrophotometers and image sensors to detect whether
a pearl has been treated or not.

2.5

Composition analysis

・ Using fluorescent X-ray analyzers, compositions (chemical elements) can be analyzed
without causing destruction to a pearl.
・ Detecting the amount of manganese and strontium by fluorescence X-ray analyzers,
sample pearls can be identified as to whether they are seawater or freshwater.
・ By detecting lead that is not found in real pearls, it is possible to identify whether it
is imitation or not.
・ By detecting silver that is not found in an original pearl, it is possible to identify
whether it is silver salt treated or not.

3.

Future tasks

3.1

Identification techniques

Recently, owing to the technological developments, pearl identification techniques haveremarkably improved. Microscopic observations, for instance, are carried out with digital
cameras equipped with microscopes, and images are processed by computers. For
identification techniques using X-ray, the development of X-ray CT devices using
computers can now provide a three-dimensional view inside the structure of a pearl. For
the measurement of nacre thickness, ultrasound and OCT (Optical Coherence
Tomography) are used. To detect whether a pearl has been irradiated or not, ESR(Electron Spin Resonance) is effective. Furthermore, though still in developmental
stages, Raman spectroscopy, owing to the developments in using laser beams and themove to data processing by computers, has made it possible for pigments and dyes
contained in pearls to be differentiated. Recently, some reports have revealed that DNA
analysis and trace element analysis by ICP-MS can be used to identify the oyster species
and place of origin of pearls.
56

3.2

Terms for ‘Keshi’At present, a new dispute has arisen about nucleated and non-nucleated pearls. This is
not the same discussion as to whether a pearl is natural or cultured, but a problem
arising from whether a cultured pearl contains or does not contain a nucleus. In the past,tiny pearls without nuclei were called ‘Keshi’, regardless of whether they were natural
or cultured. Recently, however, nucleated pearls, where the nucleus is removed after they
have been harvested, have been appearing on the market branded as ‘Keshi’ because
they do not contain a nucleus at the time of sale. In addition, such Keshi-pretending
cultured pearls are prevailing in the market; using a nucleus made of such substance as
to disappear after harvest or to make the detection of its existence impossible. In thesecircumstances, the likely intention is to give the impression that a cultured pearl is anatural pearl by calling it ‘Keshi’.
3.3

Appraising pearl quality

In recent years, with the globalization of treatment methods and diversification in thesales of cultured pearls, the processes to decide if a pearl is real or fake, natural orcultured, what oyster species it is from, and what quality it is have been presenting major
problems for the pearl industry. In the past, quality was assessed by the individual
characteristics of shape, nacre thickness, flaws, luster and color. However, the need toprovide a total valuation based on individual quality criteria has presented an increasing
challenge for appraising pearl quality.
‘Hanadama’ (literally ‘Hana’ means ‘flower’ and ‘dama’ means ‘pearl’), a term originatingfrom Akoya cultured pearls, is an example of one of these problems. The term ‘Hanadama’
was originally used for indicating high-quality newly harvested Akoya non-treatedpearls. However, increasingly Hanadama certificate started being issued even to treatedpearl products. This, in addition to a lack of unified appraisal standards, meant that
there was a loss of consumer confidence in the quality of pearls.
Whilst it is easy to evaluate each quality criterion of a pearl as there is a standardized
scale to this used by all appraisers, when it comes to overall valuation based on an
integrated assessment of each quality criterion, this is largely down to the appraisers’
own subjective opinion. A desirable colors and shapes are influenced by consumers’57

current tastes, it is difficult to set an objective evaluation standard. A basic pearl
appraisal, therefore, should not be narrowly focused on classifying quality criteria, butshould also include the following considerations:
1. Is it true or imitation?
2. Natural or cultured?
3. Spherical or blister (Hankei)?
4. Nucleated or non-nucleated?
5. What is its oyster species (and production area if possible)?
6. Has it undergone any treatments, and if so, what are the methods by which it istreated?
7. What number of pearls are there, and what are their size and weight?
8. What are the ratings for its individual quality criteria (shape, nacre thickness, flaws,
luster, color)?
Through the evaluation of each of the above points is traditionally carried out by the
naked eye, making full use of scientific instruments is increasingly important as pearl
appraisals need to produce accurate and trustworthy results. The recent developments
in analytical instruments have been so advanced that there are now various methods
that have been introduced to analyze pearl pigments, fluorescent characteristics, traceelements and isotopes, etc. Ultimately, it should be emphasized that the purpose of apearl appraisals is to enable consumers to make correct choices when purchasing pearl
products. However, unfortunately, it has been seen that in some instances, suchappraisals have strayed from their original purpose to secure consumer confidence,
instead becoming a mere tool for aggressive salesmanship.

58

Chapter 6

Related laws

1. The Pearl Promotion Law(Law No.74, 28th Year 0f Heisei)

Delivered on 7 June 2016
(Purpose of this Law)
Article 1
The Japanese pearl industry historically occupies prominent position in the world; it isa major pearl producing nation that established pearl culturing techniques ahead ofother countries. As such, there is a growing need to strengthen Japan’s international
competitiveness, and recognize that the pearl is a well-known national gem with ajewelry culture deeply pervades into nation’s life, and plays an important role for therealization of mind enriched life of the nation. This Law, therefore, aims to contribute to
the sustainable development of the pearl industry to fulfil and enhance a spiritually richnational life. The Minister of Agriculture, Forestry and Fisheries, and the Minister of
Economics, Trade and Industry shall decide a basic policy to promote the pearl industry
and its associated jewelry culture. They will take measures to promote stable
management practices for pearl producers, advance procedures for pearl processing anddistribution and promote pearl exports.
(Basic policy)
Article 2
The Ministry of Agriculture, Forestry and Fisheries, and the Ministry of Economy, Tradeand Industry shall decide a basic policy (hereinafter referred to as ‘the basic policy’)concerning enterprises engaged in the production, processing, distribution and sale ofpearls, including processed goods (hereinafter referred to ‘the pearl industry’), andactivities which promote the jewelry culture of pearls.
2.

The following matters shall be decided in the basic policy.
1) Matters concerning the basic significance of jewelry related to the pearl industry
and pearls.
2) Matters concerning the production target and other promotional efforts of thepearl industry focusing on the long-term perspective of pearl demand.
3) Matters concerning measures for the promotion of the pearl industry.
4) Matters concerning the promotion of pearl jewelry culture.
5) Matters concerning measures to improve the demand for pearls.

59

3.

The Minister of Agriculture, Forestry and Fisheries, and the Minister of Economy,

Trade and Industry may require, in deciding the basic plan, to submit materials and seek
all necessary cooperation from prefectural governors, industry groups (hereinafterreferred to as ‘pearl industry groups’) and other concerned parties, when there is a needto understand the supply-demand situation of pearls.
4.

The Minister of Agriculture, Forestry and Fisheries, and the Minister of Economy,

Trade and Industry may alter the basic policy if necessary due to the change in the
supply-demand situation of pearls and other circumstances.
5.

When finalizing and/or altering the basic policy, the Minister of Agriculture, Forestry

and Fisheries, and the Minister of Economy, Trade and Industry shall consult with thehead of relevant agencies beforehand.
6.

When the Minister of Agriculture, Forestry and Fisheries, and the Minister of

Economy, Trade and Industry have finalized and/or made changes to the basic policy,
these effects must be officially announced.
(Promotion Plan)
Article 3
Prefectures may, in adherence with the basic policy, decide a plan concerning thepromotion of the pearl industry and jewelry culture of the pearl (hereinafter referred toas ‘a promotion plan’).
2. To develop a promotion plan, prefectures may demand that pearl industry groups
and other parties concerned submit materials and provide all necessary cooperation tounderstand the supply-demand situation of pearls.
3.

Prefectures, when deciding and/or altering a promotion plan, shall promptly

announce its decision and/or alteration.
(Strengthening of Cooperation)
Article 4
The State shall, for the promotion of jewelry culture related to the pearl industry, takenecessary measures for strengthening cooperation among the State, local publicorganizations, entrepreneurs and research organizations, such as universities.
(Stabilization of Producers' Management)
Article 5
State and local public organizations shall, in the interests of stability of pearl producers'
operations, take necessary measures, such as maintenance of the pearl production base60

and reasonable compensation for losses caused by disasters.
(Promotion of Productivity and Quality Improvement)
Article 6
State and local public organizations shall, in order to improve production yields and thequality of pearls (hereinafter referred to as ‘the improvement of productivity andquality’), take necessary measures to support efforts for the improvement of productivity
and quality by those involved in the pearl industry.
(Farm Inspections)
Article 7
State and local public organizations shall, for effective and comprehensive
implementation measures to monitor pearl production, conduct investigations as needed
to understand farm conditions related to pearl production, predict environmental change
and implement other measures concerning pearl production.
2.

State and local public organizations shall, for their contribution to the activities of

pearl producers and others, supply information obtained by the investigations referred
to in the previous clause.
(Maintenance and Improvement of Farms)
Article 8
To secure stable pearl production, state and local public organizations shall takenecessary measures to help to maintain and improve the condition of pearl farms.
(Advancement of Processing and Distribution)
Article 9
State and local public organizations shall take necessary measures for the promotion ofhighly advanced pearl processing and distribution technique.
(Promotion of Exports)
Article 10
State and local public organizations shall take measures needed for the promotion of
pearl exports, taking into consideration that reclamation of foreign markets contributes
to an increased demand for pearls produced and processed in Japan.
(Promotion of Research and Development)61

Article 11
For the advancement of pearl producing techniques, improvement of productivity andpromotion of the pearl industry, state and local public organizations shall support those
who promote research and development (hereinafter referred to as ‘R&D’) anddisseminate the result of this work.
(Promotion and Maintenance of Human Resources)
Article 12
For the employment and training of talented individuals who are to carry out theefficient and stable management of pearl production, state and local organizations shalltake measures to improve the production techniques and financial management skills of
pearl producers. They will provide additional support, such as consultations to those whowish to engage in pearl production and use the requisite production techniques andmanagement methods to do so.
(Promotion of Pearl Jewelry Culture)
Article 13
State and local public organizations shall take necessary measures for planning thepromotion of the jewelry culture of pearls.
(Support for the Host of the Exposition)
Article 14
State and local public organizations shall support the opening of and participation in
expositions, exhibitions, trade shows, prize shows and other events for the promotion of
the pearl industry and jewelry cultured of pearls.
(Public Praise and Recognition)
Article 15
State and local public organizations shall publicly praise and recognize those who
contribute to the promotion of the pearl industry and jewelry culture of pearls.
(National Support)
Article 16
The State shall, when implementing measures stipulated in promotion plans by local
public organizations, supply information, advice, financial help and other assistance forthe smooth conduct of the measures concerned.
62

(Supplementary provisions)
The Pearl Promotion Law shall come into force from the day of its publication.

2. The Pearl Culture Industry Law
Delivered March 25, 1952
(Purpose of this Law)
Article 1.
The purpose of this Law is to develop the culturing of pearl oysters and pearls and to
improve the quality of pearls, with the object of contributing to the export of pearls andto the economic development of the nation.
(Definition)
Article 2.
“Pearl culture industry” as mentioned in this Law shall mean an industry which cultures
pearl oysters or pearls, processes pearls (not including the cases where goods are
manufactured by adding metals) or manufactures nuclei of pearls; and “pearl culturists”
shall mean a person who engages in such pearl culture industry.
(Publication of Goal Amount for Pearl Oyster Operation)
Article 3.
The Minister of Agriculture and Forestry shall, upon hearing the opinion of the Pearl
Culture Industry Council, determine every year the goal amount of pearl oyster
operation in each of To, Do, Fu and prefectures, according to the sizes of nuclei, and shallmake public announcement thereof.
(Submission of Plan)
Article 4.
The Minister of Agriculture and Forestry may, in accordance with the provisions of
Ministerial Ordinance, request any pearl culturist to submit every year a plan for the
pearl culture industry in which he engages.
(Advice and Recommendation on Plan and Assistance for Raising Fund)
Article 5.
In cases where a pearl culturist intends to determine the plan as prescribed in the63preceding Article, he may ask for an advice thereon of the Minister of Agriculture andForestry. In this case, the Minister of Agriculture and Forestry must give such advice as
may be required.
2

In cases where the Minister of Agriculture and Forestry deems it necessary to do sofor the purpose of attaining the goal amount determined in accordance with the provisionof Article 3, he may recommend to the pearl culturist an alteration in the plan presented
as submitted under the provision of the preceding Article.
3

In cases where the Minister of Agriculture and Forestry has given an advice asprescribed in Paragraph 1 or a recommendation as prescribed in the preceding
paragraph, he shall, when deemed necessary, assist the pearl culturist in raising funds
needed for the industry in keeping with such advice or recommendation.
(Subsidy for Culturist of Pearl Oysters)
Article 6.
The Minister of Agriculture and Forestry may, within the limits of budgetary
appropriations, grant necessary subsidy to a fishermen’s cooperative association or afederation of fishermen’s cooperative associations which engage in any of the following
businesses:(1)

Production of pearl oyster seeds or breeding of young or adult pearl oysters;(2)

Improvement of deposits of pearl oyster beds.

(Publication of Standard Price of Pearl Oysters)
Article 7.
In cases where the Minister of Agriculture and Forestry deems it specially necessary to
do so for the purpose of development of pearl oyster culturing, he may determine thestandard price of pearl oysters and make public announcement thereof.
(Inspection of Pearls)
Article 8.
No pearl (including any pearl used in pearl articles) shall be exported, unless it has been
subjected to the inspection of the National Pearl Inspection Office in accordance with theprovisions of Ministerial Ordinance, and the result of the inspection is indicated in aform as provided by Ministerial Ordinance. However, this shall not apply in cases where
pearls are exported, upon obtaining the permission of the Minister of Agriculture andForestry, as samples or for such other uses as may be designated by the Minister ofAgriculture and Forestry64

2

In cases where a Ministerial Ordinance is instituted on the matters concerning theinspection and form mentioned in the preceding paragraph, the Minister of Agriculture
and Forestry must approach the Minister of International Trade and Industry on suchmatter beforehand.
(Re-inspection)
Article 9.
Any pearl culturist or any other interested person who is not satisfied with the decisionof the inspection as prescribed in Paragraph 1 of the preceding Article may file anapplication for holding a hearing with the Minister of Agriculture and Forestry within
thirty days as from the day when such decision of the inspection was made.
2

In case where the application mentioned in the preceding paragraph has been filed,the Minister of Agriculture and Forestry must hold a hearing and examine the reason
for such dissatisfaction; and if he considers that the decision of the inspection asprescribed in Paragraph 1 of the preceding Article is not proper, he must order the Pearl
Inspection Office to make another inspection.
(Charge for inspection)
Article 10.
A person who intends to undergo the inspection as prescribed in Article 8 Paragraph 1
must pay to the State a charge for inspection in the amount as may be determined by
Ministerial Ordinance within the limits of thirty yen per momme of pearl.
(Demanding Report and Examination by Making Entry into Plants)
Article 11.
The Minister of Agriculture and Forestry may demand a pearl culturist who has been
assisted in raising funds as prescribed in Article 5 Paragraph 3 or has been granted a
subsidy under the provision of Article 6 to make reports on necessary matters in order
to ascertain how such funds were appropriated or has such subsidy resulted or may cause
his officials to enter the office, operating unit or other places of the pearl culturist andexamine the pearls, books, documents or other objects relevant thereto.
2

An official who performs examination by making entry into plants in accordancewith the provision of the preceding paragraph must carry with him a card identifying
his status and show it to the persons concerned.
3

The authority of making the entry and examination as prescribed in Paragraph1

must not be construed as having been recognized as criminal search.
65

(Establishment and Powers of Pearl Industry council)
Article 12.
In order to make research and deliberation on matters falling under the scope of its
powers, in accordance with the provisions of this Law, and other important mattersrelating to pearl culture industry, there shall be established a Pearl Culture Industry
Council (hereinafter referred to as “the Council”) in the Ministry of Agriculture andForestry.
(Organization, etc. of the council)
Article 13.
The Council shall be composed of seven members to be appointed by the Minister ofAgriculture and Forestry.
2

The term of office of a member shall be two years. However, the term of office of amember appointed to fill vacancy in membership shall be the unexpired portion of thatof his predecessor.
3

The council shall have a chairman who shall be appointed by mutual vote of themembers.
4

The chairman shall preside over the business of the council.

5

The Council must designate from among the members in advance a member who

shall act for the chairman in case the latter is prevented from discharging his duties.
6

The member shall serve part-time.

7

Other than those provided for in the preceding paragraphs, necessary mattersrelating to the proceedings of a meeting and the management of the Council shall be
determined by the Council.
(Pearl Provisions)
Article 14.
Any person who has acted in violation of the provisions of Article 8 Paragraph 1 shall be
liable to a penal servitude for a period not exceeding three years or a fine not exceeding
three hundred thousand yen.
Article 15.
Any person, who has failed to make the report as prescribed in Article 11 Paragraph 1,
or has made a false report, or has refused, obstructed or evaded the examination asprescribed in the same paragraph, shall be liable to a penal servitude for a period not66

exceeding six months or a fine not exceeding fifty thousand yen.
Article 16.
In cases where any representative of a juridical person, or any agent, employee or otherworker of a juridical person or individual has, in connection with the business affairs of
the juridical person or individual, committed any violating act mentioned in thepreceding two Articles, not only shall such violator be punished, but the juridical person
or individual concerned shall be fined in accordance with the provisions of the respective
Articles. However, this shall not apply to the juridical person or individual when thefollowing fact was proved that neither the juridical person nor individual (his legal
representative, in cases where the individual is a minor or a person adjudged
incompetent who has not the same capacity in relation to business as a person of fullage) failed to exercise due care in preventing the violating act concerned by the agent,employee or other worker of the juridical person or individual.
Supplementary Provisions:(Pearl Inspection Office)
Article 7-(6)The Pearl Inspection Office shall be an organ which conducts the Inspection of pearls.
2

The names and locations of the Pearl Inspection Offices shall be as follows:
Name

Location

Tokyo Pearl Inspection Office

Tokyo-To

Kobe Pearl Inspection Office

Kobe-City

3

The internal organization of the Pearl Inspection Office shall be determined by

Ministry of Agriculture and Forestry Ordinance(Pearl Research Laboratory)
Article 7-(7)The Pearl Research Laboratory shall be an organ which carries on the following matters:(1) Experiment, research and investigation relative to pearl oysters;(2) Production and distribution of superior pearl oyster seeds;(3) Dissemination of techniques to breed pearl oyster seeds and to culture pearl oysters;(4) Experiment, research and investigation relative to density of pearls to be cultured
and other matters relating to pearls;
67

(5) Dissemination of general information on pearls.
2

The Pearl Research Laboratory shall be established in Mie Prefecture.

3

The Minister of Agriculture and Forestry may establish branch laboratories of thePearl Research Laboratory at such places as may be considered necessary for the purposeof giving partial charge of its business.
4

The internal organization of the Pearl Research Laboratory, as well as the names ,locations and internal organization of the branch laboratories shall be determined by
Ministry of Agriculture and Forestry Ordinance.

68

Ⅴ

Definition, classification, processing and treatments of pearls1.

Definition of pearls

Pearls are biominerals with a nacreous structure, formed in a pearl sac constructed in
the body of living mollusks. They have jewelry value and their entire surface is covered
with nacre (a stratified structure of calcium carbonate crystals called ‘aragonite’ andorganic matrix called ‘conchiolin’) which is the same nacreous substance as that of thepearl oyster’s shell. However, there are some exceptions where biominerals with nonacreous structure and formed in a pearl sac in the body of living mollusks, have also
been classified as pearls.

2.

Classification of pearls

2.1

Natural pearls

Pearls formed accidentally inside a living mollusk without human intervention.
2.2 Blister natural pearls
Pearls accidentally formed in a pearl sac of a living mollusk without human intervention.
During the process of formation, the pearl perforates the mantle of the mollusk andattaches to the inner surface of the shell forming a lump as its surface is covered withnacre.
2.3

Cultured pearls

Pearls formed by human intervention in a pearl sac that is constructed in the body ofliving mollusks, the whole surface of which is covered with nacre. Human intervention
involves methods which stimulate the natural process of pearl sac formation.
2.3.1

Bead nucleated cultured pearls

Cultured pearls including a bead nucleus are formed in a living mollusk in the followingway:
1)

Pearls are formed in a pearl sac of living mollusks by insertion of a nucleus (see Note691), which involves a physical process of cutting and polishing freshwater mussel
shells into spherical shapes, sticking it together with a piece of the mantle tissue
from a donor oyster. After insertion, a pearl sac is constructed around the nucleus
and within the sac nacre is secreted around the nucleus, covering its entire surface
with nacre.
2)

Pearls may also be formed in living mollusks which have already constructed pearlsac. After pearls are removed from a pearl sac without killing the mollusk, anothernucleus is inserted on its own without a piece into the vacant pearl sac to form apearl again.

2.3.2

Non-bead nucleated cultured pearls

Cultured pearls without a bead nucleus can form in living mollusks by following
techniques:1)

Non-bead nucleated pearls can be formed in the pearl sac of living mollusks byinserting only a piece of the mantle (piece).

2)

Non-beaded nucleated seawater pearls can form in the pearl sac of living oysters
during bead nucleated seawater pearl production. This occurs when a piece of the
mantle (piece), which is inserted into the body of a living oyster with a bead nucleus,
separates from the nucleus to form a non-bead nucleated pearl.

3)

Pearls can be formed in the vacant pearl sac of oysters from which cultured pearls
are removed. After harvesting, further culturing of these harvested oysters withvacant pearl sac continues, and second pears are formed in the sacs.

2.3.3

Blister cultured pearls

Blister cultured pearls are those formed in the pearl sac of living mollusks by humanintervention. They occur when a pearl perforates the mantle of the mollusk and attaches
to the inner surface of the shell to form a blister with its surface covered in nacre.

3.

Classification of blisters

3.1 Natural blister
These are blisters accidentally formed on the inner surface of mollusk shells without
human intervention. They originate from the intrusion of foreign material, or by theaction of mollusk to repair damaged shell bored by the invasion of sponges and parasites
etc. Though the surface part of the blister is covered with nacre, the internal construction
can be either hollow, or have nacre composition.

703.2 Cultured blisters
These are blisters formed on the inner surface of the shells of living mollusks that havenacre covered surfaces by closely attaching half (and three-quarter) shaped nuclei
artificially to epithelial cells of the mantle. They are termed cultured blisters regardlessof whether the nucleus used remains after cultivation or is removed and replaced bydifferent substances. Pearls cut or ground to half or three-quarter sizes from sphericalnatural or cultured pearls are excluded from this category (see Note 2).

4. Classification of imitation pearls
Imitations are artificial products not formed in living mollusks, which are manufactured
to imitate the appearance, color and other features of natural or cultured pearls. A pearl
produced in this way is always an imitation irrespective of whether its physical orchemical properties are similar to that of natural or cultured pearls.
4.1 Artificially made imitations
Artificial products not formed in mollusks but manufactured by imitating appearance,color and other features of natural or cultured pearls with materials such as shell, beadnucleus, glass, plastics, fish scale etc. Even if the same materials of natural or cultured
pearls are used, or if the surface is manufactured from the same nacre as natural orcultured pearls, they are still classified as imitations.
4.2 Shell-modified imitations
Artificial products manufactured by cutting a part of a snail etc. and removing theperiostracum from the surface of the cut part to finish it like a pearl or blister. Artificial
products can be manufactured by cutting, grinding and polishing parts of mollusk shells
to look like natural or cultured pearls.

5.

Pearl terms and descriptions

When dealing with natural and cultured pearls, each pearl must be termed and describedin accordance with the ‘Definition’ set out in Clause 1, and ‘Classification’ set out inClause 2. These terms and descriptions must not be abbreviated and must not be used71

misleadingly (see Note 3).
5.1

Terms and descriptions for natural pearls

Natural pearls must use terms and descriptions that include the term ‘natural’ or otherequivalent terms. Pearls other than natural pearls as classified in 2.1 and 2.2 above mustnot be termed and described in the same manner as natural pearls.
5.1.1‘Natural’, ‘Real’, ‘Precious’, ‘Orient’ and ‘Oriental’

The terms ‘natural’, ‘real’, ‘precious’, ‘Orient’ and ‘Oriental’ must not be used to pearls
other than natural pearls (see Note 4)
5.1.2‘Seed’ and ‘Dust’

The terms of ‘seed’ and ‘dust’ must not be used to term and describe tiny pearls otherthan natural pearls.
5.1.3

Natural blister pearls

In accordance with Classification 2.2, the terms and descriptions for ‘Blister natural
Pearls’ must not be used to term and describe pearls other than pearls accidentallyformed on the surface of the mollusk shell.
5.1.4

Natural blisters

In accordance with Classification 3.1, terms and descriptions of ‘Natural blisters’ mustnot be used to refer to blisters other than those accidentally formed by nature as a lumpon the inner surface of a mollusk shell.
5.2

Terms and descriptions for cultured pearls

Cultured pearls must be clearly termed and described that they are cultured pearls inaccordance with Classification 2.3. Pearls other than cultured pearls classified in 2.3
must not be referred to in the same manner as cultured pearls.
5.2.1‘Cultured’ and ‘Cultivated’

Cultured pearls must be denoted by the terms ‘cultured’, ‘cultivated’ or equivalent terms
such as ‘Zuchtperlen’. Such terms and descriptions must not be used to refer to pearls
other than cultured pearls classified in 2.3.
5.2.2

‘Honshinju’

The term ‘Honshinju’ (real pearls) must not be applied to cultured pearls as it produces
a misunderstanding that said cultured pearls are natural.
72

5.2.3‘Keshi’Seawater cultured pearls without bead nuclei which are formed as a by-product during
the harvest of cultured pearls must be described by the Japanese word ‘Keshi’. The term
‘cultured’ must be added after ‘Keshi’ to clarify that they are the by-products of theseawater pearl culturing process. It is also recommended to identify such pearls by theiroyster species, e.g. ‘Akoya Keshi cultured pearl’, ‘Shirocho (Silver/Gold-lipped) Keshi
cultured pearl’ and ‘Kurocho (Black-lipped) Keshi cultured pearls’ (see Note 5).
Association of Gemmological Laboratories Japan (AGL) describes ‘Keshi’ (limited toseawater pearls with size below 3mm) in the following example:
Identification result : Akoya cultured pearl.
Comment : Traditionally called “Keshi” from the shape.
5.2.4

Blister cultured pearls

In accordance with Classification 2.3.3, pearls other than those formed by humanintervention on the inner surface of mollusk shell must not be termed or described asblister cultured pearls.
5.2.5

Cultured blisters (Hankei cultured pearl)

Cultured blisters (Hankei cultured pearls) must clearly be identified by their oyster
species as ‘Akoya Hankei cultured pearls’ (or ‘Akoya Hankei pearls’), ‘Silver-lipped
Hankei cultured pearls’ (or ‘Silver-lipped Hankei pearls’), ‘Black-lipped Hankei cultured
pearls’ (or ‘Black-lipped Hankei pearls’), ‘Mabé Hankei cultured pearls’ (or ‘Mabé Hankei
pearls’) and ‘Abalone Hankei cultured pearls’ (or ‘Abalone Hankei pearls’). The term
‘Mabé’ must not be used to generally refer to cultured blisters. Spherical natural andcultured pearls that are cut or ground into a half or three-quarter size must not betermed and described in the same manner as ‘Hankei cultured pearl’ (see No 6).
5.3

Imitation pearls

Imitation pearls must be clearly identified and described in full to explain that they are
not real pearls (in accordance with Classification 4). Imitations must not be referred toby the terms used to describe real pearls, or the terms ‘natural’ and ‘cultured’ as definedin Section V Part 1, and Part 2.1-3 above.
5.3.1

Use of the term ‘Imitation’

Descriptions of imitation pearls may only include brand names and must clarify that73

they are not real pearls by using the accompanying description ‘imitation’ before or after
the brand name.
5.3.2‘Semi-cultured’, ‘Half-cultured’, ‘Part-cultured’ and ‘Premature’Terms associated with cultured pearls, such as ‘semi-cultured’, ‘half cultured’, ‘partcultured’ and ‘premature’ must not be used to describe imitations manufactured bycoating the surface of bead nuclei or other materials with an artificial film, such as
plastics lacquer etc. Such imitations must be termed accordingly and described in full toclarify that they are imitation.

6.

Terms and descriptions according to species

Natural and cultured pearls are referred to by their oyster or name if species is identified
by a certificate of their place of origin, and features ascertained by appropriate
differentiation methods (see Note 7). Basically, the order of description should begin with
the name of the oyster species, then its shape and whether it is natural/cultured (however,the shape and the natural/culture distinction are sometimes placed the other way
around).
6.1

Seawater pearls

Seawater natural and cultured pearls are described in Japan by their oyster name (inJapanese katakana script). In commercial trade in Japan, the names of pearl oyster
species are abbreviated as follows:
Akoyagai→Akoya, Shirochogai→Shirocho, Kurochogai→Kurocho. For cultured pearls,
the term ‘cultured’ is usually abbreviated, except for Keshi cultured pearls.
6.1.1

Natural pearls

Oyster names are included in the title only when known. If the species name is unknown,
then only the term ‘natural pearl’ should be used.
Akoya (or Akoyagai) natural pearl
Shirocho (or Shirochogai) natural pearl
Kurocho (or Kurochogai) natural pearl
Mabé natural pearl
Abalone natural pearl
Conch natural pearl
Horse conch natural pearl
74

Melo natural pearl
Pen shell natural pearl
Scallop natural pearl
Quahog natural pearl
Mussels natural pearl
Natural pearl
Natural blister pearl
Natural blister
6.1.2

Cultured pearls

Oyster names are included in the title only when known. If the species name is unknown,
then only the term ‘cultured’ should be used.
Akoya pearl (or Akoya cultured pearl)
Akoya Hankei pearl (or Akoya Hankei cultured pearl)
Akoya Keshi cultured pearl (or Akoyagai Keshi cultured pearl)Shirocho pearl (or Shirochogai cultured pearl)Shirocho Hankei pearl (or Shirochogai Hankei cultured pearl)Shirocho Keshi cultured pearl (or Shirochogai Keshi cultured pearl)
Kurocho pearl (or Kurochogai pearl)
Kurocho Hankei pearl (or Kurochogai Hankei cultured pearl)
Kurocho Keshi cultured pearl (or Kurochogai Keshi cultured pearl)
Mabé pearl (or Mabé cultured pearl)
Mabé Hankei pearl (or Mabé Hankei cultured pearl)
Abalone pearl (or Abalone cultured pearl)
Abalone Hankei pearl (Abalone Hankei cultured pearl)
Cultured pearl
Cultured blister pearl
Cultured blister
6.2

Freshwater pearls

Freshwater natural and cultured pearls are not described by the species of mussel forthe following reasons:1) There are so many different kinds of mussel species capable of producing pearls thatit makes it difficult to identify all their names.
2) The vast differences in common and regional names of mussels makes it difficult to
identify them.
753) Occasionally, a piece of mantle tissue is inserted from different mussel sources.
4) There are hybrid species, such as ‘Ikecho’ (Hyriopsis schlegelii) and Triangle mussel(Hyriopsis cumingii) which are used for pearl culturing.
6.2.1

Natural pearls
Freshwater natural pearl
Freshwater natural blister pearl
Freshwater blister

6.2.2

Cultured pearls
Freshwater cultured pearl
Freshwater cultured blister pearl
Freshwater cultured blister

7.

Processing and treatments

Processing and treatments of the pearl are physical and/or chemical methods to alter
shape, inner structure and weight of natural and cultured pearls, to enhance their latent
beauty and to change their original color and appearance irrespective of their original
character.
7.1
7.1.1

Processing and treatment methods
Drilling

Using super-steel drills to make cylindrical holes through or into the center of pearls.
7.1.2

Cutting (including three-quarter cutting)Cutting a pearl (including three-quarter cutting) using tools such as diamond cutter, etc.
7.1.3

ShapingChanging the surface feature of pearl to improve its smoothness of curves.
7.1.4

Polishing

Improving pearl luster by physical and chemical methods, such as barrel tumbling,
animal skin polishing, buffing, high-speed polishing and acid polishing.
7.1.5

GluingSticking together cut pearls with adhesive agents.
7.1.6

Filling

Introduction of resins or other substances into the body of a pearl to reinforce its strengthand increase its weight.
76

7.1.7

Coating

Covering the entire surface of a pearl with resin or other materials to reinforce its
strength and improve the color and luster of a pearl.
7.1.8

Thermal processing

Removal of unfavorable colors and/or improvement of luster by heating.
7.1.9

Mae-shori

Soaking pearls in water or organic solvents at either room or ambient temperature tostabilize the color tone and improve the luster of pearls.
7.1.10BleachingRemoval of organic matter, stains (stain removal) or pigments (whitening) found innatural and cultured pearls to alter and stabilize their color. (see Note 9).
7.1.11 Tinting
Slight color alterations to Akoya cultured pearls by the addition of red dyes tosupplement the iridescent color an Akoya cultured pearl naturally possesses.
7.1.12DyeingApplication of natural and synthetic dyes to natural and cultured pearls to alter theircolor and appearance from their original character.
7.1.13

Coloration

Application of chemical reagents other than dyes to natural and cultured pearls to alter
their color and appearance from their original character.
7.1.14

Irradiation

Color alterations made to a pearl by irradiation (mainly by gamma rays).
7.1.15Modification

Changing the calcium carbonate structure of nacre to a different substance usingchemical reagents such as calcium fluoride for reinforcing the strength of a pearl. (seeNote 8)7.1.16

Cultured blister (with lid) processing

The nucleus and impurities are removed after cutting away cultured blisters (see 3.2)
from the attached shell, filling the vacant part by removal with resin etc., and attachinga lid made of shell nacre.
7.1.17

Cultured blister (with shell) processing

Cultured blisters (see 3.2) are cut out together with a part of the attached shell, for shapeprocessing.
As processing and treatments from 7.1.6 to 7.1.14 change original characteristics ofnatural and cultured pearls, such as color, luster, appearance and weight, they have to77

disclose their methods. Treatment 7.1.16 should also be disclosed since modification
alters original nacre characteristics composed of calcium carbonate to different calcium
fluoride, deviating from definition of the pearl.

8.

Descriptions of cultured pearl standards

When handling cultured pearls as commercial products, their commodity value andquality must be disclosed. These disclosures apply to both loose (undrilled, half-drilled,
drilled-through, three-quarter and Hankei) and stranded cultured pearls (threaded
and/or finished strands with clasps) produced by all species of oyster.
8.1

Commodity standards

Commodity standards for valuing cultured pearls involve an assessment of the size,
weight, length (if sold as a strand) and quantity of pearls.
8.1.1

Size

Sizes of pearls are described in millimeters (mm). The sizes of Akoya cultured pearl aresorted by sieves with holes that differ by half millimeter intervals. Pearls are sifted andthose that remain are classified as the maximum size (Example: 7.5mm X 8.0mm). In
the case of Silver-lipped and Black-lipped cultured pearls, the process to determine theirsize varies according to whether they are stranded, loose or loose pearls as a lot.
Stranded: the diameter is measured from vertical direction against the hole threaded
the strand. The minimum and maximum size range of the pearls is determined by 0.1mm
intervals (Example: 10.3mm X 15.8mm).
Loose pearls: both maximum and minimum sizes are determined by 0.1mm intervals(Example: 15.4mm X 15.8mm).
Loose pearls as a lot: Pearls are sifted with sieves which differ by 1mm intervals and thesize of pearls that remain in the sieve, and those that are 1mm larger are identified(Example: 12mm X 13mm)
8.1.2

Weight

The weight of a pearl is measured by units of Momme (1 Momme =3.75g) for bothstranded and loose pearls.
8.1.3

Length of a strand

The length of a strand is measured by inches (”) or centimeters (cm). In case of Silverlipped and Black-lipped strands, length is specified up to one decimal place.
8.1.4

Quantity
78

The quantity of stranded pearls is determined by the total number of pearls, or numberof strands. Loose pearls are counted according to whether they are grouped in pieces,pairs or sets.
8.2

Quality standards

The quality of cultured pearls varies according to whether they are bead nucleated, nonbead nucleated, blister cultured pearl or cultured blister (Hankei cultured pearl). All
cultured pearls should adhere to the following quality standard.
8.2.1
1)

Bead nucleated cultured pearls
Pearls should possess a good luster, which has not been affected by build-up ofprismatic layers and/or organic substances.

2)

Pearls should possess a sufficient nacre thickness, ensuring that nuclei are notvisible through the nacre.

3)

Blemishes should not be severe enough to damage the structure and overall
integrity of the pearl.

4)

There should be no cracking in the nucleus or nacre.

5)

Tinting, dyeing and coloring processes should be applied appropriately
according to methods that preserve overall quality.

6)

Treatments should not be excessive or affect the overall quality of the pearl.

7)

Any staining should be minimized and ensure a suitable surface for work.

8)

There should be no breaking or peeling of the nacre.

8.2.2
1)

Non-nucleated cultured pearls
Pearls should possess a good luster which has not been affected by build-up ofprismatic layers and/or organic substances.

2)

Nacre should be uniformly thick, without evidence of hollow cavities inside a
pearl.

3)

Blemishes should not be severe enough to damage the structure and overall
integrity of a pearl.

4)

There should be no cracking in the nacre.

5)

Tinting, dyeing and coloring process should be applied appropriately using
methods that preserve overall quality.

6)

Treatments should not be excessive or affect the overall quality of the pearl.

7)

Any staining should be minimized ensuring suitable surface for work.

8)

There should be no breaking or peeling of the nacre.
798.2.3
1)

Cultured blisters (Hankei cultured pearls)
Pearls should possess a good luster, which has not been affected by build-up ofprismatic layers and/or organic substances.

2)

Nacre should be uniformly thick, with a smooth wrinkle-free surface.

3)

Blemishes should not be severe enough to damage the structure and overall
integrity of the pearl.

4)

Treatments should not be excessive or affect the overall quality of pearls, and there
should be no evidence of uneven dyeing or color variations.

5)

There should be no visible damages, such as removal of the lid or cracks andbreakages in the nacre.

9.

Care of pearls

9.1

Routine care

1)Natural and cultured pearls should always be handled with care.

2)

When natural and cultured pearls are worn, cosmetics should always be applied
before, not after dressing.

3)

Natural and cultured pearls should not be worn when undertaking heavy manual
work.

4)

Natural and cultured pearls should be wiped with a soft cloth immediately if theycome into contact with water.

5)

After wear, natural and cultured pearls should be cleaned with a soft cloth.

6)

When not worn for extended periods, natural and cultured pearls should be
regularly maintained by wiping with a soft cloth.

7)

When storing natural and cultured pearls, they should be kept separate from otherjewelry items to avoid scratches caused by contact with other materials.

9.2

Special care

In addition to routine maintenance, the following special attention should be given tonatural and cultured pearls to preserve their appearance.
1) Natural and cultured pearls should not be exposed to strong natural, artificial
or display lights for extended periods as this will lead to fading and/or changing
the color.
2) Natural and cultured pearls should be kept away from acids and other organic
80

solvents.
3)

10.
10.1

Natural and cultured pearls should never be subject to ultrasonic cleaning.

Other related matters‘Hanadama’According to a pearl industry regulation, ‘Hanadama’ indicates precious, high quality,
very beautiful untreated Akoya pearls. They are cultured in Japan using Akoya oysters
and are very rare. Regarding ‘Hanadama’ Japan Pearl Promotion Society on its
homepages has called for the following:

Notice concerning the description of ‘Hanadama’“Nowadays, it has been noted that ‘Hanadama’, a very important term in the Japanese
pearl industry, is often being used in a manner that differs from its original meaning.
‘Hanadama’ is a term that has been used for a long time in the pearl industry to describe“the most excellent quality pearls among harvested Akoya cultured pearls” that are notused for manufactured products. However, in the market today, variable qualities of
Akoya pearls are traded under the name ‘Hanadama’ without a unified standard of
quality in the industry. In publications entitled ‘The Hanadama valuation report’ issuedby agencies undertaking pearl appraisal, there are clearly different applications of theterm ‘Hanadama’ from its original meaning. There are some agencies giving the name
“Hanadama” even to Silver-lipped and Black-lipped cultured pearls.”
In this respect, ‘Hanadama’ does not always indicate “the highest quality pearl”. Thus,
to say at the time of sale that a pearl is of the highest quality only by reason that it hasa ‘Hanadama’ certificate is not sufficient justification for the consumer. Such
explanations only create misunderstanding and confusion amongst customers, which
threatens to damage confidence in Japanese Akoya cultured pearls. As for the sale ofpearls with or without a ‘Hanadama’ certificate, it is the responsibility of a company’s
workforce as specialists in pearls, to decide whether they describe these products as “thehighest quality”. This judgment should be handled with integrity based on an awarenessof the importance of not losing consumer confidence by deviating from the original
meaning of ‘Hanadama’.
10.2

PS treatment
81

PS treatment is a method to substitute the carbonate ions of organic calcium carbonatebased gemstones (pearl and coral) with fluoride ions to improve its durability, especially
its resistance against acid. In 1998, this method was patented as Patent No. 2868730,‘Manufacture of acid resistant organic gemstones’. According to the patent, the following
two methods are permitted:(1) Solution method
Prepare 2% sodium fluoride solution. By adding phosphoric acid to the solution, prepare
weakly acidic solution with approximate pH 5.5. Submerge the organic gemstone insolution and leave for prescribed time (e.g. 30 minutes), heating it to maintain prescribedtemperature (e.g. 30-40℃). This forms a protective film consisting of mainly calcium
fluoride on the surface of the organic gemstone.
(2) Electrolysis method
Put electrolyte containing approximately 2% sodium fluoride in an electrolytic bath.
Organic gemstones composed of mainly calcium are immersed near the anode to form aprotective film of mainly calcium fluoride on the surface by electrolysis.
It has been reported that by these methods the calcium of the organic gemstone isstrengthened to provide sixty times more acid resistance. However, the issue is debatedas to whether calcium carbonate is actually replaced with calcium fluoride, and whetheracid-resistance has really increased. Some appraisal agencies have different opinions on
the matter, and in the past, it was argued that PS treated pearls were imitations. If thesurface of the pearl has changed to calcium fluoride, this would mean that the surface ofa pearl is covered with a foreign object, hence PS treated pearls should be dealt asimitations.
Japan Pearl Promotion Society defines pearls as “biominerals with a stratified structureof calcium carbonate (aragonite) and organic matrix (conchiolin)”. Thus, if they arecomposed of calcium fluoride and an organic matrix, they do not meet the criteria to becalled ‘pearls’.
10.3

Imitation pearls

The history of imitation pearls is older than that of cultured pearls; it dates back to the
Roman Age. In the past, when there were only natural pearls on the market, they were
owned by royalty and titled nobility. As it was almost impossible for common people to82

own them, imitation pearls were regularly used as substitutes. The most famous
imitation pearl was made in the latter half of the 1600’s by a French rosary craftsman
named Jaquin, using freshwater fish cyprinid scales. He extracted guanine from fish
scales, pasted it on the inside of a hollow glass ball, and was strengthened this by fillingthe ball with wax. Despite these efforts, it is said that the imitation pearl was so fragilethat many shards of the glass were found scattered on the floor after a guest wearing anecklace containing this ball left it at a party.
The technique of making imitation pearls using fish scale spread to Japan around 1919
via Europe and America, and sometimes around 1924 and 1925, production reached its
climax. In Japan, instead of herring, hairtail scales were originally used for imitations
and eventually replaced by plastic.
The interesting things to note about imitation pearls is that in Europe the trend moved
from natural, imitation and to cultured pearls, while in Japan, the trend shifted fromnatural, cultured and to imitation pearls. Therefore, imitation pearls manufactured inJapan are often mimicking cultured pearls in their names and characteristics. In thepast, there was a struggle which involved the Fair-Trade Commission, concerning thedescription of imitation pearls as a company named Sato Pearl once manufactured andsold imitations under the name of ‘The Third Pearl’. In recent years, there was anotherexample of a company in Geneva, Switzerland, which operated inflight sales of imitation
pearls under the name of “Misaki semi-cultured pearls”.
Up till now, imitation pearls have been made of completely different materials to easily
distinguish them from real pearls. However, in the future, it can be imagined that thesubstances that compose real pearls will not be made in living oysters, but in factories
by techniques such as genetic manipulation. Therefore, it is crucial therefore that thenaming, identification methods and standards for pearls clearly distinguish them from
imitation pearls.
10.4

NucleusThe quality of pearls should be considered with attention to the quality of the nucleus
used. When cultured pearls appeared on the international market for the first time, theargument as to whether cultured pearls were true or fake became so heated that it had
to be settled in court. In this dispute, the nucleus was also an important factor in83

securing the verdict that cultured pearls are true pearls. If china, glass, stone and metals,
such as gold and silver had been used as nuclei, cultured pearls may never have been
judged as genuine.
The text of the Paris verdict on September 20, 1924 mentioned, “Japanese pearls can be
regarded as high-class pearls, covered with nacre having a nacreous nucleus inside ofthem”. Since then, the Japanese pearl industry has been using nuclei made fromnacreous materials, specifically ball-shaped nacre from freshwater mussel shells.
Recently, however, the quality of nuclei that Japan has protected for a long time has been
deteriorating. The following can be considered the three main reasons for this decline:(1) Present situation of freshwater mussel shells for nuclei
In the United States, a major provider of freshwater mussel shells for nuclei
manufacture, freshwater mussels are protected by the Convention on International
Trade in Endangered Species of Wild Fauna and Flora (CITES, Appendix I) and theircollection is totally banned except for a few exempted species. Today, only one of thesecompanies has survived meaning that that the amount supplied to Japan is drasticallydecreasing, and good quality nuclei are becoming highly sought after, valuable goods.
(2) The appearance of Chinses nuclei
As a result of globalization, not only pearl culturing and treatment techniques, but also
nuclei manufacturing techniques have spread to China. In addition to using mussels
collected in Chinese rivers, huge amounts of freshwater mussel shells intended for pearl
culturing are being re-used after the harvest as material for manufacturing nuclei. As
these mussels contain many orange and purple pigments in their shell nacre, the colored
nuclei which result from these mussel shells are bleached with strong reduction
bleaching agents, making them more fragile.
(3) The appearance of substitute nuclei
The size of nuclei used for Silver-lipped and Black-lipped pearl culturing is mostly over8mm. The production of such large nuclei requires thick shells. However, the number ofmussels with thick shells is very low, so naturally the price of nuclei made of thick shell
becomes very high. For this reason, substitute nuclei are being increasingly used as
replacement for ordinary nuclei.
Typical examples of substitute nuclei are those made of Giant clam shells, and glued
nuclei. Both of these, however, have their own problems. As for nuclei made form Giantclam, although the catching of Giant clam is regulated by CITES Appendix II which84requires an attached certificate of origin, this regulation is often utterly neglected. As
such, dealing with pearls cultured using Giant clam nuclei poses a moral dilemma for
pearl dealers. Meanwhile, glued nuclei are made by sticking several, sliced freshwater
mussel shell plates together to create layers that become a single thick plate, which isthen shaped into large, spherical balls. Glued nuclei, however, have issues due to theirpoor durability and contamination by adhesive substances.
In addition, various nuclei made of fine ceramics, plastics, hydroscopic materials andwax are appearing on the market. Considering the similarity of these materials to theoriginal characteristics of nacre through their high biological and physical resemblances,such as their specific gravity, thermal expansion coefficients and dryness shrinkage
factor, the use of conventional nuclei is a method that should be maintained for the
production of Japanese Akoya pearls.
Most of the reasons that pearl cultivators head for substitute nuclei reflect attempts to
reduce culturing costs. When cultured pearls cannot be sold at a high price, this resultsin difficulties to balance culturing costs with sales, making cost reduction a naturalnecessity. However, pearls cultured with cheap nuclei bring further price drops, causing
a vicious cycle to be repeated. High-quality pearls should be produced using decent
materials and sold at a price worthy of its quality and brand. It is imperative therefore
that we strive to move from a vicious to virtuous cycle.

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11.

Notes

Note 1
The material of a nucleus was historically limited to the nacre of freshwater mussel
shells, allowing for no other materials. The reason for this goes back to the Paris court
trial. In 1919, when cultured pearls were sold for the first time in European markets,
they were accused being imitations, and a legal battle ensued to prove whether cultured
pearls were true or imitation. The verdict of the lawsuit stated:
Paris pearl judgment (September 20, 1924)“Estimant que la perle japonaise étant un noyau de nacre recouvert d’une materière
perlière puovait être considéré comm fine” (“Japanese pearl can be regarded as highquality gems, which have a nacreous nucleus covered in nacre”).
Since this verdict, Japan has traditionally used nuclei made from the shell of freshwater
mussel. However, as the pearl culturing industry globalized (as the below table shows)nuclei of various materials are now used in countries across the world. It should be notedthat nuclei made of Giant clam shells is in violation of the Convention on International
Trade in Endangered Species of Wild Fauna and Flora (CITES). Glued and pasted nuclei
are problematic too as they have poor strength.
Nuclei should ideally be made of shell, but once substance, such as glue and resin becomecommonly accepted as nuclei materials, this poses a threat to the industry by increasing
the ratio of poor-quality nuclei used around the world. As for the type of nucleus thatshould be used, this is stipulated in the CIBJO Pearl Book as follows:
CIBJO Pearl Book 5.20 Bead for cultured pearl
A sphere (usually) or other shape (occasionally) formed only by cutting and polishing anacreous shell used to accommodate the nacre secreted from a graft of mantle tissue,
which eventually forms the center of a beaded cultured pearl. That is to say, it has beenprescribed that nuclei used for pearl culturing should be made by physically shaping
freshwater mussel shells without the addition of any scientific treatments including
bleaching.

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Types of nucleus
American shell (Pig toe, Washboard,
Maple leaf, Three ridge)
Freshwater mussel shell

Chinese shell (Gananose : Lamprotura coreana)
Chinese shell (Triangle mussel)

Shell

Seawater oyster shell

Giant clam
Silver-lipped oyster

Seawater snail
Shell compound

Brown shell

Glued
PastedTreatedFluorescence whitening treatedBleached
Glass
Plastics

Artificial productFine ceramic
Wax
Mud

Mineral

Dolomite

Pearl

Freshwater cultured pearl

Checking the material of a nucleus
Inspection of a nucleus is performed by considering the following criteria
・Cracks (any cracks in the nucleus layer)
・Glitter (a part of the nucleus that shines)
・Colored (colored streaks are seen)
・Streaks (striped patterns are seen)
・Skin attached (a part of periostracum of the shell is attached to the
nucleus)・Blemishes (black colored part (s) can be seen)
・Flaws (flaws can be seen in a part of the nucleus)
・Setting (a part of the nucleus is broken, deviating from spherical form)
Note 2Though cultured blister are not pearls, the term ‘pearl’ was historically used for blisters,
87such as Chinese Buddha pearls, Linnaeus pearls and Kokichi Mikimoto’s cultured halfpearls. Even today, cultured blisters are called Hankei cultured pearls.
Note 3
The word ‘pearl’ can generally be used on its own without distinguishing if it is ‘natural’or ‘cultured’ when it refers to the name of a pearl company or association. However, theterms ‘natural’ and ‘cultured’ must be included with the term ‘pearl’ when used todescribe merchandise.
Note 4
The term ‘natural’ is sometimes used to refer to the natural color of pearls when they are
harvested.
Examples : Silver-lipped natural golden, Akoya natural blue and Akoya natural gray.
However, ‘natural’ should not be used to describe treated colors, such as ‘natural white’for bleached but non-tinted Akoya cultured pearl.
Note 5In CIBJO (World Jewellery Confederation)’s 1991 edition of the Pearl Book, the termʻKeshiʼ was defined: “ʻKeshiʼ is a Japanese trade name, which means small pearl.
ʻ Keshi’ can come from wild oyster or from cultivated oysters, as a by-product of
cultivation of seawater pearls”. However, in the International Pearl Design Contest of
Pearl Retailers’ Association in 1995 and 1996, large, non-bead nucleated pearls describedas ‘Silver-lipped Keshi’ and ‘Black-lipped Keshi’ were awarded. As these descriptions
were violations of the CIBJO rule, the definition was subsequently amended at CIBJO
1997 Congress in Las Vegas to provide a new definition of ‘Keshi’ as “non-beaded
seawater pearls, which are by-products of pearl cultivation”. In Japan, where freshwater
pearls have been harvested for a long time in Lake Biwa, tiny pearls were harvested as
by-products and have in the past been referred to as ‘Freshwater Keshi’. The reason‘Keshi’ is a term now confined to seawater pearls is that there are so many non-beaded
freshwater pearls cultured as main products in China that it is nearly impossible now to
distinguish these from ‘Keshi’ by-products.
Recently, nuclei, made of various materials are used for pearl culturing. After culturing
nuclei are removed from pearls and such non-beaded pearls are sold as’ Keshi’ since “theydo not contain nuclei”.
The Pearl Standard of Japan Pearl Promotion Society’s definition is that “They are ‘Keshi’88when a nucleus is not included in the pearl at the time of harvest”. Therefore, pearls
where nuclei have been removed after harvesting are not ‘Keshi’. As for pearls brought
into appraisal agencies for evaluation to determine whether they are ‘Keshi’ or not, AGL(Association of Gemological Laboratories Japan) changed the description of ‘Keshi’ from
April 2014. This was because it was very difficult to identify whether non-beaded pearls
were cultured without a nucleus or have had their nucleus removed after harvest. As aresult AGL refers to ‘Keshi’ as “seawater pearls with sizes below 3mm” and uses thefollowing description as an example:
Identification result : Akoya cultured pearl
Comments : Traditionally called “Keshi” due to its shape
Some dealers, however, define ‘Keshi’ as pearls harvested from Akoya oysters with sizes
below 2mm.
Note 6
Hankei cultured pearls (cultured blisters) using Mabé pearl oysters are often treated as
the representative species for producing Hankei cultured pearls. Therefore, in foreigncountries, irrespective of the species of mollusk used, all Hankei cultured pearls are often
called Mabé. It is a misrepresentation, however, to call Hankei cultured pearls Mabé ifthey are not cultured using Mabé oysters.
Note 7Natural and cultured pearls are not necessarily referred to by their place of origin.
However, the place of origin is often used for the purposes of distinguishing the same
species produced in different regions. Examples include: Japanese Akoya cultured pearls,
Tahiti Black-lipped cultured pearls, American freshwater natural pearls, Mexican Pteria

sterna cultured pearls, and Kasumiga freshwater cultured pearls.
Note 8
As for treatments discussed in Section V Part 7.1.7 ‘Coating’ and Part 7.1.15‘Modification’, these were not included in the definition of the year 2000 edition of thePearl Standard as Japan Pearl Promotion Society does not allow them.
Note 9Reduction bleaching and fluorescent whitening, which are different from ordinary
bleaching, are sometimes used. However, reduction bleaching considerably lowers the89quality of pearls, so it is not allowed by the year 2000 edition of Japan Pearl Promotion
Society’ Pearl Standard. As for fluorescent whitening, this treatment adds different
fluorescence characteristics from that of the original pearl, so this is also not allowed by
the Pearl Standard. However, AGL uses the notation “treated with fluorescent whitening
agents”.

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