LUSTER: PEARL'S PINNACLE
This is the first in a series of pearl quality factor discussions
designed to help you explain these popular and precious gems to your customers
by Devin Macnow Cultured pearl Information Center
For cultured pearl experts, luster is perhaps the most important indicator
in evaluating cultured pearl quality. Luster is what separates the inferior
pearl from the superior and the ordinary from the extraordinary. Luster
is what many experts term the heart and soul of the sea-grown gem. Throughout
history, this unique luster has separated pearls from all other gems. Early
man, captivated by this mysterious sphere born from the ugliest of all sea
creatures, likened the luster of a pearl to that of the shimmering moon.
In fact, pearls were once believed to be teardrops of the moon that had
fallen into the sea only to be swallowed by oysters.
Though we're no longer subject to such fanciful beliefs, the luster of
the pearl still captivates. For the layman and jewelry novice, the luster
of a pearl can best be described as a combination of a high, reflective
sheen on the surface of a pearl combined with an almost three-dimensional
glow that seems to emanate from within the heart of a pearl.
Luster, in more scientific terms, is the reflection and refraction of
light as it passes through the layers of aragonite crystals (often referred
to as nacre) that comprise a cultured pearl. The intensity of luster is
determined not only by the amount of these crystals but also by the specific
geometric pattern in which they are secreted upon the nucleus by the oyster.
Many factors play upon nacre secretion and these ultimately determine
the intensity of luster. The health of the oyster, the water temperature
of the host environment and the level of nutrients available to the oyster
in that environment all play a vital role in creating a pearl with superior
Though the intensity of a pearl's luster can be an indicator of nacre
thickness, and thus determine the durability of a pearl, this correlation
is not always true. In some cases it is possible for a cultured pearl to
have a very thick coating of nacre and still have a mediocre luster. Again
the formation of nacre crystals plays an important role in luster. Sometimes
when nacre crystals are in a very loose formation they do not have the ability
to refract and reflect light in the same manner as a pearl with very tightly
packed nacre layers. This phenomenon sometimes occurs in pearls grown in
For the average person, evaluating the luster of a cultured pearl is
not rocket science. Luster can be judged easily by the naked eye and without
any equipment. Pearls with high luster have the ability to sharply reflect
images around them, almost like a mirror. In addition they always display
the characteristic depth or three-dimensional glow and a subtle display
of different surface colors (sometimes referred to as orient) that is so
prized among high-quality pearls. Pearls with low luster often look dull,
monotonous, chalky and lifeless.
As for pricing, pearls with high luster account for only 8% to 10% of
all cultured pearl production in any given year so they usually command
premium prices. With all other factors such as surface, shape, color and
size being the same, a medium-luster 7mm pearl will cost about 30% more
than a low-luster pearl of the same size. A pearl with high luster will
often run 60% to 70% higher than a cultured pearl with low luster.
For anyone who has ever seen a high-luster pearl, it's easy to appreciate
the value and mysterious beauty captured in the gem. For without luster,
a pearl is simply a bead without any real value or charm. Copyright © 1998 by Bond Communications.