The word 'keshi' is a Japanese word meaning
the smallest particle imaginable, e.g. a grain of sand, poppy seed, etc., it
is used in Japanese for all pearls that grew without a nucleus. In the Japanese pearl
business it is slang for the by-product of any oyster seeded for
culturing. It is not in itself natural, being caused by the act of operating.
In Japan, the act of inserting a nucleus with its attendant 'mantle piece'
(epithelial tissue) into Pinctada martensi can
cause keshi formation. This, although not naturally 'accidental' has been
termed 'adventitious'.
Keshi pearls
are small non-nucleated pearls typically formed as by-products of pearl
cultivation. Originally, keshi pearls referred to those pearls formed when a
bead nucleus was rejected. More recently, keshi has been used to refer to
second harvest pearls and even to freshwater non-nucleated pearls. However the
later usage referring to freshwater pearls is considered erroneous by many
leading gem trade associations. Because they have no nucleus, keshi pearls are
composed entirely of nacre.
With the insertion of a nucleus into the
gonads, the incision itself, plus the piece of mantle tissue inserted, can
cause the formation of small cysts or sacs producing small pearly baroque
'pearls', varying from 1 to 4mm.
A
report from a well-informed source in Japan runs as follows:
Keshi it has long been used to describe in
Japan a by-product of the culturing of pearl from akoya oysters; and non-nucleated
pearls produced, either as a result of culture or else deliberately as opposed
to being a natural product.
Akoya oysters (P.
martensi); silver-lipped or golden-lipped (P.
maxima); black-lipped (P. margartifera); black-winged
pearl oysters (Pteria penguin) are
all used in various parts of the world's oceans to produce in sea-water
whole or half pearls by the technique usually known as
'pearl culture'. This surgery on the flesh of the animal causes it to produce
within organs, other than its pearl sac, tiny and small pieces of pearl apart
from the prime cultured pearl; this product is generally known as 'keshi' and
consists of (usually) baroque-shaped small sizes of solid pearl, though in
larger sizes there may be a hollow at the centre. Without the culture operation
the animal would not produce more than a small percentage of the pearl material
that it has to yield when irritated by culture.
Keshi,
being pure pearl, responds favorably to bleaching and
treatment; and finished pearls are often lustrous, bright, white and
attractive. A very small amount of akoya keshi comes in round shapes and this
is sorted out in India, mixed with Persian Gulf products and sold frequently in
the USA for the add-a-pearl trade. P. maxima of various lip colors gives
also a 'keshi' of sizes larger than akoya in rough proportion to the sizes of
oyster, akoya - P. maxima. Golden-lip shell yields a creamy-tone
keshi, black-lip a grey-tone keshi. Larger sizes are doubtless sold either by
ignorance, or intent, as perles fines and
there must be pearls on which detection even by X-rays can be difficult. Learn
how to evaluate pearl quality at What
to Look for When Buying Pearls? Your Guide to Buying Pearls.
Origin of Name
“Keshi” (occasionally misspelled Keishi,
apparently a confusion with “Heishi beads”) was first used in Japan to
describe pearls without nucleus. Akoya pearl cultivation, which began in the
1920s in Japan, provided numerous small, most often greyish pearls as a
by-product. Traders from India, where natural pearls were harvested and
processed during past centuries, needed no sales talk to be convinced that they
could sell Japan Akoya keshi in their market and to visiting Arabs as natural
pearls, because their close similarities. Having access to Indian labor capable
of sorting, drilling and stringing tiny pearls, arrangements were made to send
Japanese keshi pearls to India (even during many years in which imports were
not sanctioned); provide processing services at conditions without rival; and
covertly retain pearls for sale in India under an allowance for pearls ruined
in the course of processing.
Pearl importers in consumer countries, and
the trade associations they constitute, have recommended limiting the use of
the term keshi to ocean pearls, and banning its use for freshwater
pearls. This is justified to some extent by the fact that ocean pearl keshi
were known as a product for some years before their freshwater counterparts.
Japanese language usage of keshi certainly includes freshwater pearls.
It has always been a generic term, not a trademark, and its application to
freshwater pearls by the Chinese is based on visual similarity that is quite
close. Restrictions proposed would likely be futile, but would do nothing to
resolve the ambiguity among various ocean pearl sources (Akoya, Southsea
Kasumi, Tahitian) that can be eliminated by using keshi only in
conjunction with mollusc name/species and/or provenance.
Chinese use of keshi for freshwater
pearls is generally limited to those from a second (or subsequent) harvest.
These differ considerably from the plump, full shapes of first-harvest
freshwater pearls, which grow during a young mussel's growth period, when nacre
production is at its peak. Older mussels produce nacre more slowly, and
second-harvest freshwater pearls (if not nucleated) are generally flat and
often thin, with concavities and texture mostly absent from first-harvest
pearls. Curiously, the Chinese use keshi to differentiate between two distinct
products, while Japanese usage, requiring only the absence of a nucleus, is
equally applicable to both.
Origin of Keshi Pearls
All of
the following can cause a keshi pearl to grow:
1) An attack on a pearl-producing mollusc by
a predator that bores through its shell... similar to a way in which wild
natural pearls are formed, except that captive molluscs are more susceptible.
2) Accidents causing injury to molluscs, for
example driving shell fragments into mantle tissue.
3) Cultivation mishaps, generally separation
of the mantle tissue graft from an inserted nucleus... this causes the intended
nucleated pearl to fail, and a smaller keshi pearl to grow instead.
4) Deliberate non-nucleated cultivation,
still the most common type in freshwater pearl farming.
5) Keeping freshwater molluscs with pearl
sacs alive after harvesting the (first round of) pearls.
Except to the extent
of noting that extremely small pearls (less than than 2mm) are not cultivated,
since there is no incentive to do so because naturally occurring tiny pearls
are relatively plentiful, it is usually not possible to determine which of
these caused an individual keshi pearl to grow. Because most keshi pearls come
from farms where they are commonly and deliberately cultivated, it is necessary
to classify keshi as cultivated / cultured pearls. Any natural pearl (without
nucleus) may be called a keshi pearl, but doing so would be rather meaningless
without mentioning the species of mollusc in which the pearl grew, or at least
its geographic provenance. Use of “keshi pearl” without provenance is confusing
and should be avoided.
Freshwater Keshi
In Lake Biwa, Japan, and in river areas in
China, there is a regular production of keshi pearl. In Japan the animal is a
mussel, Hyriopsis schlegeli, and in
China it is presumed that a similar mussel is employed. In Japan, and it is
assumed that the Chinese copy the Japanese, small pieces of flesh are inserted
into the animal, with the result that for the first year crop good quality Biwa
keshi is produced; this is taken out of the mussel without the host being
killed, so a second and then a third crop is also produced by the same animal
without more flesh being inserted. Injections by syringe of glucose or vitamins
are sometimes made but this is not universal. The second crop is duller and
flatter than the first; whilst the third year crop is very thin, even like
slices of pearl, lusterless and dirty and it is often used for grinding into
medicine. It is not sure that the Chinese produce second and third year crops
since their first year original crop is very much inferior to that of Lake Biwa,
being wrinkle-skinned, dull of luster and with many bone-like or dead pearls.
The Japanese only (not the Chinese) also pump
air into the mussels' pearl sacs in order to produce within these sacs long
stick-shaped pearls resembling old-time Mississippi 'dogs' teeth'; being very
adept, they also can make variations of this stick shape so that the mussel
produces such sticks formed either as a triangle or even cross-shaped
(cruciform). By combinations of flesh and air pump, fancy shapes of keshi are
also made, such as flats, ovals, and even squares.
Salt-water
akoya keshi production may annually reach a weight of
400 kg; Australian keshi will, however, be only some 7 per cent of this figure.
Lake Biwa production is about ten times that of akoya whilst the Chinese crop
is believed to exceed greatly that of Lake Biwa. The huge majority of
fresh-water keshi is made into uniform strands which are then treated into many
different colors. They sell easily world-wide but especially in Western
Germany.
Nature vs. Nurture Controversy
Because it is impossible to determine whether
an individual keshi pearl grew serendipitously or as a result of mantle tissue
insertion, they are all classified as cultivated/cultured
pearls. It is possible to speculate on the likelihood of keshi pearls from
various cultivations based on supply and demand. Tiny “seed” pearls (less than 2mm)
occur commonly in all types of molluscs used for pearl cultivation, both ocean
and freshwater, thus there has never been a need to find a way to cultivate
tiny sizes. Japan Akoya pearl production generated large numbers of tiny keshi
pearls, the pearl
value of which was mostly in the labor-intensive processing,
so there is little or no incentive to cultivate extra keshi. Southsea pearls on
the other hand are farmed in larger molluscs, and keshi from these may reach
considerable size and value. Freshwater cultivators in pre-1985 Japan commonly
used up bits of active mantle tissue left over from in-body bead nucleation by
slipping a few keshi into the mantle. Now the market of those keshi farmed in
China is so low that they discard the leftovers rather than expending even a
tiny fraction of their mussels' strength on producing freshwater keshi.
Freshwater
keshi pearls from China are for the most part
unquestionably cultivated, but in an indirect way. Active mantle tissue grafts
in a mussel's mantle are needed in order for the first harvest of pearls
(pearls NOT considered keshi by most Chinese dealers) to grow. Except for the
insertion of nuclei in selected pearl sacs to make coin pearls and
bead-nucleated “flame” pearls, keshi pearls will grow without any further
intervention following the careful harvesting of the first round of pearls.
Since mussels may live for many years, the process may be repeated; however the
amount of nacre produced continuously falls with age, and most cultivators harvest
only twice.
Keshi pearls consist of solid nacre, and tend
to have high luster as a result. All nacre colors typical of the mollusc under
cultivation may be represented among keshi pearls harvested from the same, but
in the case of Akoya pearls a larger portion of keshi is usually grey than of
bead-nucleated pearls.
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