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Based
on archeological data, it has been shown that over several
millenarian within the vast Pacific region, there appeared
numerous cultures which venerated or worshipped jade.
These include the Olmec and Mayan civilizations on the
American continent and the Maori Culture of New Zealand,
in addition to, of course, the age-old Chinese
civilization. As the "jade" relics from these
cultures were most often found to consist of nephrite or
jadeite, minerologists have limited the scope of true jade
to include only these two substances.
Chemically speaking a silicate of calcium and magnesium,
nephrite belongs to the amphibole group of minerals. It
occurs primarily in dolomitic marbles or in serpentinized
ultramafics. Throughout the ages, nephrite has been
frequently employed as a working material. While the
locations of the deposits that yielded very ancient
nephritic jades aren't know, nephritic jades from the
Shang Dynasty onward originate in dolomitic deposits of
the Kunlun Mountains in Sinkiang Province. As it has been
collected for the most part in the Ho-t'ien District, it
has been called "Ho-t'ien jade." Nephrite of
this provenance appears in numerous colors. From a snowy
white state in the absence of impurities, it darkens into
various shades of bluish white in relation to the amounts
of magnesium or iron present. An increase in the amount of
ferric ion imparts a yellowish hue. When particular areas
of a piece of white or bluish-white jade contain hematite,
brown jade is obtained; graphite infusions, depending on
their concentration lead to either grey or black jade. The
fact that these two colorations frequently coexist in a
given stone had been exploited by the jade craftsman.
Examples of jades whose coloration and shape harmonize can
be seen in the "Cup in the shape of an animal
horn" and the world renowned "Jade vase in the
shape of a horned fish" displayed in National Palace
Museum, Taipei.
Dark-green nephrite has its origins in the serpentinized
ultramafics of Sinkiang Province's Tien Shan Ma Na Ssu.
Similarly colored nephrite has been quarried in Hualien on
Taiwan, New Zealand, Canada, and elsewhere.
A
silicate of sodium and aluminum, jadeite is classed as a
pyroxene. Although in a class different from nephrite,
jadeite shares many characteristics with it, namely a high
degree of hardness and firmness, and a luster that lends
an appearance of transparency. Additionally, variations is
iron content result in brownish-red, dark green, or
lavender hues. Presence of minute amounts of chromium
yields emerald green. Finally, the characters in the
Chinese appellation for jadeite, fei-ts'ui, are those for
two species of kingfisher whose feathers are of a color
similar to that of brownish-red and emerald green jadeite.
( extracted
from exhibition catalogue of National Palace Museum
)
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