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Natural Pearls
This is the type formed by accident, without
human inMvention, and was virtually the only one known before
t beginning of the twentieth century.
Appearance Most natural pearls
used in jewelry r: roughly spherical, and this is the most
suitable shape ' ordinary necklaces. Pearls may, however,
be somewhat regular in shape. If they have rounded, not too
obvious pr jections, they are known as baroque pearls. These
are alpierced and threaded, especially if medium-sized or
smr: while larger specimens are used as parts of designs,
' instance, as the head or body of an animal, a human fac
or a fruit. Pearls may also be pear-shaped, in which cathey
are normally used as pendants, or they may be flc: tened at
one pole, or both, in which case they are genera "rested
on a piece of jewelry, such as a ring, brooch, - earring.
When examined under a 10x or 20x lens, pearls often diplay
small, superficial irregularities, roughly conical proc .
berances, barely visible furrows arranged in parallel,' _
tiny flaws like miniature craters on the moon, sometim, with
a cometlike tail on one side. At higher magnification the
normally smooth and shining surface displays closa set, minute,
sinuous lines, evenly distributed throughow
The color varies from white with a hint of gray
to white wit a yellow tinge, but can also be silvery gray
or more noticcably yellow. In strong light, pearls have characteristpearly
or "nacreous" luster and may also be iridescer with
the emphasis on pink or other colors, which give very pleasing
effect. Alternatively, they can be slight . translucent, revealing
faint speckles or marks on the if side, this generally being
due to the presence of abnormally large quantities of the
organic componew conchiolin, and water, which makes the pearl
more liable % deteriorate.
Many antique pearls look badly damaged. Sometimes par of the
outer surface of nacre has been worn away or ther• may
be loss of luster, caused by dehydration of the organi component
or by the dulling effect of acid perspiration o, the mineral
component (calcium carbonate). Therefore one often finds that
some of the pearls in an antique piecc of jewelry have been
replaced, usually by modern, culturec pearls.
Distinctive features Pearls can generally
be distinguished by their surface appearance-which is lustrou~
but with microscopic, discontinuous wavy lines-frow glass
imitations with a very different surface or from other imitations
covered by a special, minutely granular varnisr made from
ground fish scales. A much harder problem i~ distinguishing
natural from cultured pearls. Individua! pierced pearls can
be distinguished by observing the inside of the hole with
a strong lens or binocular microscope
A succession of concentric layers (possibly
with a dark center, if the pearl is slightly grayish) is characteristic
of natural pearls, while a compact, almost waxy-looking nucleus,
with a single, clearly different layer around it is characteristic
of cultured pearls. Although it is impossible to judge a single
unpierced pearl by its outward appearance.
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