JAPAN KASUMI NEWS AND VIEWS
The Soul of the Lake:
A Tribute to the History and Artistry of Japanese Freshwater Pearls
September 22, 2026
The third annual Live Sale Event, on location at Kise, near Tsuchiura, Ibaragi Prefecture, Japan was a record breaking success, and we are grateful to Jeremy and Hisano Shepherd of Pearl Paradise for introducing our product to their much wider audience.
Jeremy Shepherd is President of the Pearl Association (formerly Cultured Pearl Association of America) which can be joined by following this {link}.
Unlike his predecessors, and the majority of pearl dealers throughout history, he shares my belief that frank disclosure and unvarnished fact can indeed promote love of pearls among intelligent people. His "Pearls as One" Online Course offers more up to date knowledge about pearls than any published source. Now in its second edition, it is available {link}. Your writer had the honor of proofreading some of the new texts and making suggestions for changes.
Kiyoshi Yoneguchi, in his words "the last samurai of Japanese freshwater pearl cultivation, continues to work without human helpers (only fish) to breed the hybrid mussels he originated. When they reach adequate size, he performs a unique operation in the springtime, (known only to him and his daughter) on them to insert a nucleus.
He reports that storms, flooding, and earthquakes have limited the time he had available for operating on his mussels at the ideal time in their growth. Instead, it was taken up by emergency infrastructure repair. These calamities are believed to be caused or exacerbated by global warming. Even if what are at present believed to be ideal conditions were to prevail until then, this means that the harvest at the end of 2030 will be much smaller.
Throughout the summer, he hangs them in nets suspended from racks supported by poles he has driven into the bottom of his two permitted sites, one in Lake Kasumi-ga-Ura and one in the mouth of a tributary, Onogawa. And in midwinter, when the cold blooded creatures are at the perigee of nacre-producing activity, he harvests those which have been in the natural water for four years, thereby minimizing the chances of getting less than a complete layer of nacre. He has two dinghies, one at each site.
Currently, the mortality rate is about 40%, but it has been a lot worse. A dead mussel yields no pearl, and another 10 - 15% are useless. No wonder all the other freshwater pearl cultivators in Japan gave up.
Some of the more litigious former freshwater pearl cultivators apparently sued various branches of the government they felt were responsible for the loss of their livelihood. The result was that bureaucrats as a whole adopted an unfriendly stance towards freshwater pearl cultivators, including those who were still active, and applications for new permits to replace sites that had ceased to be viable languished for years. This probably resulted in even more bankruptcies.
The Ministry of Land, Infrastructure, Transport and Tourism, among other things, controls national government land, including lakes, rivers and their embankments. This agency issues the permits for Kiyoshi's sites. inherited from his father and so "grandfathered in". Because abandoned boats in Lake Kasumi-ga-Ura apparently pose a problem, the same agency planted a signboard at the lake site, ordering the removal of the dinghy, on pain of seizure. I attempted to suggest alternatives, but learned that no portable boat could bear the weight of the mussels. Instead, Kiyoshi, Jeremy Shepherd (President of the Pearl Association), Sarah Canizzaro (Kojima Pearl and Treasurer of the Pearl Association) and your writer sent petitions. After half a year, the boat remains moored, leading to cautious optimism that the Ministry has tacitly granted the petitions.
Kiyoshi's intention to make more baroque pearls, probably unique among pearl farmers, is succeeding slowly. This is in response to our niche market that more desires strong, dark and scarce colors much more common in baroque than in round pearls. That these would therefore increase was a gamble that shows signs of gradually paying off. Pearl color depends to a degree on the choice of active mantle tissue used for the graft which forms the pearl sac. But this has been known for a long time, and there is little room for improvement there. A "nurture" component, previously trivialized, may play a role,
Among myriad environmental catastrophes thought to be due to global warming, one factor has apparently, for the moment at least, helped with the quest for more strong colors. It is causing a considerable change in the water temperature in which Kasumi-ga-Ura pearls grow. With pure-bred Hyriopsis schlegeli mussels, that was chief among the causes they could not be kept alive. Kiyoshi's H. schlegeli/cumingii hybrid, fortuitously discovered in the mid 1980's, is in many ways more robust. Meanwhile, he discovered that the plankton on which mussels feed had changed. His theory is that the warmer water plankton may play a role in the incipient trend towards more "collector" colors popular among many of our clients.
Since time immemorial, the widespread belief that pearls ought to be white caused natural pearls to be bleached. Natural colors of freshwater pearls tend to fade in sustained strong light (for an amusing anecdote about this, click {here}). Their luster is not adversely affected. In ocean pearls like akoya, light alone does nothing to remove the natural creamy, yellow and greenish color; chemicals like hydrogen peroxide are needed. The loss of luster and of the cohesive strength of the nacre are considerable, leading to higher prices and reduced durability in direct proportion to the strength of the treatment. This is true of China freshwater pearls which are often bleached with peroxide because the "sunning" process is so time consuming.
Akoya shells were bred for decades for pale colors to aid bleaching and maximize whiteness. A belated appreciation of their natural colors has resulted in some of them being dyed into mild to exaggerated golden hues. Carrying forward a tradition of disinformation, such treatments, along with bleaching, are often denied instead of disclosed.
Kiyoshi's pearls undergo no treatment except washing with salt; this is necessary because organic matter from the pearl sac adheres to pearls, making them lackluster if allowed to dry without this cleansing. His father, Takasuke Yoneguchi, was one of the first to begin pearl farming details {here}) in the Kasumi-ga-Ura area. He clearly believed in the economies of scale. Of some 50 concrete breeding pools (measuring roughly 10 by 1000') he built, Kiyoshi uses only 3.
Kiyoshi Yoneguchi's gumption, his love of his product and friendships with many that study, wear and sell it, and pride in being the last man active, keep him practicing his art.
The Biwa Pearl Museum
Kiyoshi divulged a great deal of inside information on his craft, and is also the source of the "Chronology of Freshwater Pearl Cultivation in Japan" {link} which, with his help, your writer translated and annotated. In 1985, he discovered a hybrid Hyriopsis schlegeli / cumingii mussel, just as the pure bred H.schlegeli could not be kept alive. He shared its spat for free with all his competitors in Kasumi-ga-Ura, and his father's partner in a company which in 1963 pioneered pearl cultivation there.
Tetsuya Toyama {details here} then shared the spat with the Lake Biwa Mother Mussel Assn. for large scale breeding and distribution to pearl farms in Lake Biwa. That Association, when the jig was up in Lake Biwa, launched a co-operative program with China. Similarly to individual technicians who had been promised much in exchange for teaching their skills, they were thrown out when they had completed their part of the bargain.
In 1980, when H. schlegeli mussels were still thriving and Japan's freshwater production was at its peak in terms of volume and value, the Yoneguchis, Takasuke and Kiyoshi, toured Chinese freshwater pearl farms. The then JAL station manager introduced them to Chinese cultivators desirous of starting a joint venture to farm in China. They declined.
The H. schlegeli mussels native to Biwa and the ones introduced in the 1920's by Masayo Fujita to Kasumi-ga-Ura, Kiyoshi reports, differed considerably in shape, speed of growth, and nacre characteristics. While being of the same species, the differing environments including plankton availability cause Biwa mussels to be flatter and more elongated, have slower growth, and whiter nacre prone to uneven luster. Those in Kasumi had more girth and were shorter, with rapid growth, more varied colors, and more consistently lustrous nacre.
When pressed for more information on this chapter of history, Kiyoshi said that the Biwa Pearl Cultivating Assn. disbanded in the early 1990's, and none of its members are living. He believes that, except possibly in possession of the descendants of cultivators, no collection of photos nor of artifacts exists. His own collection was lost in a fire that destroyed his home in 2010. The Eastern Japan Great Earthquake occurred on Mar 11, 2011, destroying much essential infrastructure; the 3 then remaining freshwater pearl cultivators were not spared.
Rudolf Voll (1911 - 2008) was fond of non-nucleated Biwa and later Kasumi-ga-Ura pearls. In our stores in Tokyo and Hong Kong, we introduced them to Europeans(mainly German-speaking) in the 1960s and 70's. Not many were prepared to spend money on what was new to them. Those that did, often faced ridicule at home, for buying expensive small pearls that were not even round. A case in point was related to us, after its rewarding conclusion, by an Austrian doctor.
Being known to carry Japan Biwa (as well as Kasumi) pearls, your writer has fielded many phone calls from appraisers and insurance adjusters as to their replacement value.
In 2026, a senior teacher at one of the largest and most respected gemology schools in the world purchased some Japan Biwa non-nucleated strands for use as a teaching tool.
An article written some time ago and never published with addresses this theme:
Are Japanese and Chinese freshwater pearls identical, and if not, how can I tell the difference?
Musings on Japan Lake Biwa non-nucleated freshwater pearls.
While handling these pearls, some have been in our family's possession before 1970, even without the aid of labels, there is seldom any doubt as to whether a strand is Japan Biwa, or China origin. The Chinese freshwater pearl cultivators have carried the baton to new heights of diversity, affordability relative to the spherical ideal, and size since they made the change from using "Kwong" (meaning shine and denoting Cristaria plicata), to "Sam Kwok" (three corners, ie the roughly triangular Hieryopsis cumingii, and, subsequently, probably many varieties of martensii hybrids) starting in the 1980's.
The visual difference is familiar to cognoscenti, but hitherto considered ineffable. This results in the vast majority of pearls described as Biwa to be of Chinese origin. It motivated Mr Dillenburger (dba Perlen Yukie in Germany) to commission some boffins at the University of Marburg to define a test. What they came up with was a destructive (requiring pearls to be pulverized) test comparing histograms of strontium and barium concentrations of each. A small sample being inconclusive, it falls short of being practical. Needless to say, most gem labs do not attempt it.With the exception of areas of diminished luster typically affecting only part of pearl (thus giving a clue to their provenance) Japan Biwa's tend to have stronger shine, especially considering their age. This is probably because they were not usually bleached with chemicals, only with light. There was a time when Chinese pearls were bleached using sunlight, strands were hung on bamboo poles which are normally used to dry clothes. With the import of peroxide bleaching technology from Japan ocean (Akoya) pearls, such a time-consuming process was soon abandoned. And it has become standard practice of all China origin pearls (not only the bleached ones) to tumble them with bamboo chips impregnated with silicone to improve their luster. This was not common in Japan, and at any rate does not last for years.
The JB's shapes are prone to have sharper edges. The predominant shape of larger non-nucleated Biwa pearls is roughly lentil shape, called mochigata in Japan, a reference to the common New Year's decoration of a stack of (usually 3) kagami(=mirror)-mochi of that shape. This kind of Biwa pearl sometimes have indentations on one side in the center, where they are drilled for making strands.
Near-spherical shape and even near-circular buttons were highly prized for their scarcity. The prices of even small diameters of rounds and buttons were commensurate. But the main market of the non-nucleated pearls was Hyderabad (India) and thence the Near East, home of many OPEC countries. Often pretending to be natural pearls (and presenting the same image when X-rayed). These customers did not expect perfection, indeed rejected bead nucleated Akoya pearls. One of the only available published commentaries on this subject comes from the late Robert Crowningshield, to wit:
"The matter of freshwater cultured pearl terminology is not academic when we consider that in both Japan and India, export papers describe the product as "natural pearls." Since they reach America from these countries under this description, the official papers carry some weight with importers and brokers who have contested the contraption by the Laboratories. They point out that they go into India duty free as "natural pearls," whereas there is a 25% duty for cultured pearls. We are in agreement that the product deserves a descriptive and marketable term that will serve to distinguish them from ordinary nucleated cultured pearls." Source: "Gems & Gemology" (GIA) Spring 1962
Your writer opined in the 1990s that Chinese pearls with no nucleus were rounder than those with, but out-of round ones (ovals & buttons) tend to have better luster. The late Fred Ward once shared a theory that very large spherical pearls with no nucleus were produced by using smaller pearls as nuclei. However, Chinese sources explained that pearl nucleation at that time did not produce round pearls, and was practiced solely to increase the weight of the irregular pearls harvested. Previously bleached pearls used as nuclei were known to increase mussel mortality rates.
Until the in body bead nucleation (IBN) technique became widespread in China, non-nucleated pearls, especially small diameters, were indeed apt to be rounder. In the 2020s, smaller diameter bead-nucleated pearls (body and mantle) and those with synthetic nuclei became common. This means the same tradeoff between roundness and nacre thickness that bedevils akoya production exists. The synthetic (shell powder and glue) nuclei, however, provide no easy way of gauging the lack of adequate nacre thickness that akoya pearls' shell (cut from sufficiently large freshwater mussels) nuclei do; the flat layers of the nucleus can be seen by the naked eye. Don't be fooled by the fraudulent use of "akoya" to describe these pearls.
China akoya did and reportedly do exist, but the only specimens Pacific Pearls (in Hong Kong since 1970) were able to source were small blue/grey baroques, which disappeared from the market by 1985.
In a small way, the present popularity of vintage akoya has benefitted us, for with 50+ years of experience in Japan, we have some old stock. The ones that survive to be vintage tend to exclude bright colors, which always had to undergo severe bleaching. All akoya pearls are treated with peroxide for spot removal (shimi-nuki) but we find a preponderance of near-natural creamy colors among our saleable vintage akoya.
As akoya are currently in production, it is questionable what constitutes "vintage". In contrast, non-nucleated Japan Biwa have been out of print for more than 40 years. Kiyoshi Yoneguchi, whose martensii/cumingii hybrid accounts for every freshwater pearl cultivated in Japan since the mid-1980's, cultivates only 大球（oodama＝big pearls, meaning IBN) in Kasumi-ga-Ura (Japan). Pacific Pearls has purchased and imported his entire harvest of Japan Kasumi pearls for many years. Along with all other Japanese cultivators, he abandoned all non-nucleated cultivation ca 1985; it no longer made sense to expend even an iota of his mussels' nacre producing power in the face of Chinese competition in keshi, which in a pearl context simply means “non-nucleated” in Japanese.
In the 20th century, bead nucleation was practiced only on a relatively small scale in China, so that most of their production could (and is) sold stating or implying Japan origin. Only circa 2010 the production had grown to extent that the ruse was untenable. Enter Chinese in-body bead nucleated pearls, IBN for short, but few have accepted this obvious name. Instead, they are called "nucleus", confusingly without distinction from in-mantle cultivated Flame pearls, dubbed "Fireballs" by Dave Federman, and brand names, like "Ming" and "Edison". The latter is very pervasive, especially since many resellers use it, and certain educators choose to teach it.
Another quote from Robert Crowningshield's 1962 article, which introduced freshwater and non-nucleated pearls to the Western Hemisphere:
"Another suggestion has been that, since Lake Biwa, so far, is the only culturing center for these pearls, the term "Biwa cultured pearls" be used. This suggestion is not valid for the Gem Trade Laboratories, since we do not attempt to give sources of other gem materials." (Ibid)
Would that it had been more widely read (and understood). For those who want to read it, excerpts are reproduced {here}.
Except for their name, mainly honored by misuse, Biwa pearls have been relegated to a remote corner of history. But for vintage pearl enthusiasts, they are rare finds which have not been produced for more than a generation.
Signed your writer, Fuji Voll Pacific Pearls