pearls should take time to learn to evaluate luster and, in
particular, to recognize what is acceptable and what is not
acceptable; in particular, when luster is too low. Luster is produced
when rays of light are absorbed into and reflected back out through
the nacre - the layers of calcium carbonate that make up the pearl.
Luster is rated from very high to very low. In general, the thicker
the nacre, the deeper the luster. Japanese pearls, in general,
exhibit a higher luster than South Sea varieties that show a softer,
more velvety appearance.
Pearls with a
bright, intense luster sharply reflects nearby images, will have a
good nacre thickness; pearls that look very dull or chalky probably
have very thin nacre or poor quality nacre. Roll the pearls to view
them from all sides to make sure the luster is uniform. Examine them
under a light source such as fluoroscent lamp, looking for
reflections of the light off the surface, paying particular attention
to the brightness or sharpness of the reflections. Avoid strong,
direct light. If the available light is too strong, hold your hand
over the pearls to shade them, and examine in the shadowed area.
Japanese Akoya cultured pearls can have a higher luster than other
white round cultured pearls because of the water temperature in which
they are produced. Cold water causes slower nacre production, which
normally results in superior crystallization and over-all nacre
quality. When the nacre is good, and is exceptionally thick, Japanese
Akoya pearls can have incredible lustrousness. The luster can also be
very chalky, indicating very thin nacre, or poor quality nacre.
Pearl Luster Facts
Of the value
factors, luster is among the most important. Luster refers to the
quality and quantity of light reflecting from the pearl's surface, or
"brightness" of the pearl. Very high luster is a sign of
fine quality nacre, and is found only in the most rare pearls that
command a premium price.
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