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Jadeite jade 2
Distinctive features Its almost
alabastine translucence, the minute internal network of discontinuities
and corresponding effect on the outer surface, its degree
of hardness, the graduated streaks of color, and the incomparable
shades of green, are frequently sufficient to distinguish
jadeite jade from similar materials of lesser value, notably
serpentine (which is highly translucent, greenish white to
oil green, of uniform color, less hard, and less dense) and
what is known as Transvaal or Pakistan jade (which is a mixture
of microcrystalline hydrogrossular and vesuvianite, that ranges
from highly translucent to almost opaque, lacks the internal
appearance of jadeite jade, and has a rather different range
of colors, fractionally higher density, and higher indices).
But many natural materials are occasionally used as substitutes,
and it may be hard to tell them apart.
Occurrence Most jadeite jade used in Chinese
art since the latter half of the eighteenth century and most
of that used today comes from northern Burma. Thus, nowadays,
the name "Burmese jade" is synonymous with jadeite
jade. It has also been found in Japan, the United States (California),
and Guatemala, and only rarely in a few other places. It is,
therefore, much less common and more localized than nephrite
jade.
Value Jadeite jade has a very wide range
of possible values. As a gem, the translucent emerald green
variety known as imperial jade can fetch prices only just
below those of the principal gemstones, particularly emerald,
which it so much resembles. Yet pieces in other colors are
worth no more than other fine, hard opaque stones.
Where the material is used for carving and engraving, the
value depends very much on the quality of the workmanship,
the skill with which any patches of color have been exploited,
and the standard of finish. It is, nevertheless, the most
valuable of materials used for this purpose, worth more than
nephrite jade, except for very finely worked or antique pieces,
where no distinction is made between the two.
Simulants and synthetics Some whitish pale-green
or green aventurine, also of granular structure, is occasionally
used as a substitute for jadeite jade and known as Indian
jade, though it lacks the exceptional mechanical and chromatic
properties of true jade. Synthetic jadeite does not exist.
A problem which has arisen recently over jadeite is that of
coloration. Because of the minute discontinuities present
in the mass, it is easily impregnated with artificial dyes,
to pleasing effect. In this way, for example, whitish jadeite
can be made to look like the much more highly prized imperial
jade; and the other colors are also often imitated in this
way. One can usually distinguish cases in which the color,
rather than being contained in individual crystals, is distributed
in the minute fractures and cleavages of the mass, but a microscope
is needed for this.
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