The
Mise-Nishikawa The
Mise-NishikawaThe first step in the operation is to open-up the pearl oysters, but -hopefully- without killing them. Most technicians employ inverse steel pliers to force open their pearl oysters. Forcing open the oysters causes much mortality (depending on the species, anywhere from 30 to 70%).
But not here. In Mexico we use a more humane method to ensure a very good survival rate. This method lowers our mortality to only 1-5%. Recently, improvements in our own technique have allowed for a mortality in the 0.5 to 1.2% range.
Now we can
proceed to perform the operation. But first, we need a
"donor" oyster to obtain mantle tissue cells
(the mantle is a thin, skin-like organ, responsible for the secretion of nacre
or "mother-of-pearl shell").
We will cut away a strip of mantle tissue and then cut it up into small squares. These little pieces of mantle tissue will then be known as grafts.
Next, we must put the recipient oyster on a special stand, and an incision is made in the soft body of the oyster.
Thru this incision we will insert
a long and slender steel probe, and we will make a tunnel inside
the animal's body mass, but always avoiding delicate organs: the
heart, liver and pancreas, kidney, stomach and intestines).
At the end of this tunnel we will find an organ usually referred as "the pearl sac" (keep in mind that the real "pearl sac" is really a tunic of epithelial mantle cells), made up of both gonad and connective tissues.
This is the most appropriate place -within the animal- to grow the cultured pearl, because it is both big enough to allocate the nucleus (and future cultured pearl) and receives many nutrients from the body.
Inside this pearl sac, we will introduce one spherical shell bead or nucleus. These beads are quite special for many reasons: they are obtained from the shells of freshwater mussels (family Unionidae) from the Mississippi River and its many tributaries.
Those mussels are quite capable of making freshwater pearls, and their shells are -of course- made of mother-of-pearl shell, which makes them most appropriate for pearl culture. If you inserted any other kind of material -instead of mother-of-pearl- your pearl will crack when drilled for jewelry uses.
Finally, comes
the piece of mantle tissue, the graft must be placed
alongside the bead. If all goes well (the animal survives,
doesn't spit out the bead, etc.) the little piece of tissue will
"graft" itself to the surrounding tissues, it will grow
around the sphere and then will begin coating it up with
microscopic layers of nacre (depositing anywhere from 1 to 3 layers daily).
After a wait of -at least- one year and a half (18 months) or up to two years (26 months), the coating of nacre on top of the shell bead should at least be between 1.2 and up to 3.0 mm. Thus, a beautiful and colorful pearl will finally be born unto the world.
A really good cultured pearl should last several lifetimes (this is mostly due to the good thickness of nacre) without peeling or cracking up, otherwise we are talking about low-quality Akoya pearls (grown mostly in China and Japan), that have very little nacre in them (thickness of only 0.1 to 0.2 mm around the bead) and will not last very long.
Copyright 1998-2007 Perlas Únicas S.A. de C.V.
Last Updated 05/2007
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