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IMPERFECTIONS
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necessitating
the removal of several entire skins before a sphere is reached again.
The under skins of some pearls appear to have failed to completely
envelop the nucleus. The cavity resulting is then filled to an even
surface and is succeeded by fully developed skins. It is, therefore,
not certain that a pearl, perfect in form and skin when found, has been
so at all stages of its growth. Broken pearls sometimes show not only
differences of color but of thickness in the successive layers. The
skins of fresh-water pearls especially are often very irregular in
thickness.
Many
pearls have cracks in them. These generally escape the observation of
inexpert persons, as they are usually under the outer layer. The fact
that they rarely extend to the surface suggests that the
solidification, or drying out of the confined interior layers, may be
the cause. These are considered detrimental and dangerous by dealers,
so that pearls with cracks in them will not bring as high a price as
they would if free from them.
As cracked pearls are liable to break, especially when pierced for stringing, it is well to
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