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Cultured Pearls 2
Sometimes, when a cultured pearl whose external
lay are either too thin or translucent is viewed against a
strc light, horizontal lines can be seen. These are the `
parallel layers of the artificial nucleus and have nothinc
do with the concentric layers-never visible, incic tally-characteristic
of natural pearls. Even simple ob, vation of the external
shape can provide information us for purposes of distinction,
when one is dealing with wr strings of pearls rather than
individual pearls If the pe are all perfectly spherical in
shape or have only very ` protuberances, rather than slight
but extensive spher defects, it is very probable that there
is a turned nuci inside, forming a sizeable, rigid infrastructure
onto wr the oyster has been forced to deposit the nacre spherical
shape.
This factor, combined with the two ; ceding
ones (viewing against the light and observatic - the drill
hole) should almost always make it possibla identify a string
of mainly cultured pearls. Australian tured pearls are unique.
These, in fact, have a highly cr acteristic appearance (and
size), which makes them c easy to identify.
As already mentioned in the discussion of natural pe:-. the
physical characteristics of this gem are not eas. measure,
except for the density. This is usually slic higher in cultured
pearls than natural pearls and is a: 2.74 g/cm3. When cultured
and natural pearls cannc' distinguished by the types of direct
observation just scribed, radiography and X-ray diffraction
techniques used, as they are with natural pearls, and these
will F tively identify even unpierced specimens
.
Occurrence The main center of production
for culn. pearls is Japan. Other, less important centers are
ch along the northwest coast of Australia. More recently fivation
of pearls has begun along the coasts of India.
Value There is a big difference
between the value of ural pearls and that of cultured pearls,
which on ave cost at least ten times less. The same criteria
are usr evaluate them as to evaluate natural pearls, i.e.,
color ter, regularity of form and compactness. When dealiny
..
a string of many pearls, great importance is attach(, their
general homogeneity. Furthermore, a string o` tured pearls
of uniform diameter is worth more than or - graduated diameters
and a pair of identical pearls is v. more than two different
ones.
The thickness of the pe layer surrounding the
nucleus is especially importa evaluating cultured pearls.
A thicker layer in relation t, diameter of the nucleus takes
longer to produce (the a:. age period of cultivation is four
to five years, but somet it is extended to six to seven years)
and therefore c more. Furthermore, a very thin layer, sometimes
seeString of cultured poor quality pearls, is much less durable.
Lastly, a thi pearls. layer of nacre usually, if not always,
gives an appearar closer to that of natural pearls.
Despite their rather cc color and lack of iridescence,
Australian cultured pea are worth much more than the others
partly because their size. Sometimes they have a thick layer
of nacre, t cause one of the many qualities of the mollusks
used produce them is the ability to complete their task with
cc siderable speed. Nowadays, however, the tendency is restrict
culture to only three years, more pearls in a shor time being
preferred to pearls with thicker layers.
Simulants These are the same
as already mentioned natural pearls. Majorca is now famous
for the productior imitation pearls, which look very convincing
at a distance
1 - 2
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