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Jade Properties
For collectors as well as jewelry lovers, jade is a
fascinating gemstone.
In general, the value of jade is determined according to its color and the
intensity of that color, the vivacity and texture, and its clarity and
transparency.
For the Chinese, jade had been the physical manifestation of spiritual virtue,
the embodiment of all that is most desirable, for several thousand years.
Jade of one type or another is found in Burma, Central America, Brazil, Canada,
Japan, India, Siberia, Finland, Tanzania, and elsewhere. It is prized for its
hardness, glassy luster, and rich translucent colors.
Jade is properly applied to two distinct stones: nephrite and jadeite. Nephrite,
either from local source or imported from central Asia, was almost the only jade
used by the Chinese until around the time of the American revolution, when
jadeite was introduced from Burma.
Although quite different in mineralogical composition, the two stones share many
qualities. A milky, soft-colored stone, nephrite is a calcium and magnesium
silicate with a tightly bonded, fibrous structure. It is usually white, green,
or violet but can be other colors as well. Jadeite, a sodium and aluminum
silicate, comes in more colors, ranging in tone from white to gray and in hue
from yellow-orange to violet. But it is best known for the bright green of the
highly polished form that is favored for jewelry, where it is cherished for its
high luster. Jade's spectrum of colors is the result of trace elements -- such
as magnesium in green jade or iron in jades with a yellowish hue -- mixed in
with the snowy white of the pure mineral.
Jade cannot be carved. Because of its hardness, it can rarely be shaped by
chiseling or chipping but must be worn away by abrasion with tools and hard sand
pastes. This is a process that requires immense patience -- even with modern
machinery equipped with diamond-tipped burrs that grind out intricate designs,
it remains laborious. Yet jade appeared in Chinese culture several thousand
years before metal tools existed. Neolithic jade artisans worked with bamboo,
bone, and stone tools, using a drilling or bow action to abrade the jade with
sand. Because the process was so labor-intensive and time-consuming, jades
reflected the ability of a ruling elite to command resources, and therefore came
to symbolize power, status, and prestige.
Jade Grades
Jade may be enhanced or more commonly referred
to in the industry as "stabilized" to yield 3 different grades.
Grade A
Jadeite has not been treated in any way except surface waxing. This type of
jadeite, carat by carat, is the most expensive gem in the world, even more
so than diamond.
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Grade B
Type B
treatment involves exposing a promising but stained piece of jadeite to
chemical bleaches and/or acids and impregnating it with a clear polymer
resin. This results in a significant improvement of transparency and color
of the material. Currently, infrared spectroscopy is the only test for the
detection of polymer in jadeite. |
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Grade C
Type C jade has been artificially stained or dyed. The red color of Red jade
can be enhanced with heat. The effects are somewhat uncontrollable and may
result in a dull brown. In any case, translucency is usually lost. |
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