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Turquoise 2
Occurrence In ancient times,
turquoise was mined in Sinai peninsula and Iran, while certain
Central Amer, peoples, the Aztecs in particular, extracted
it in what is - known as New Mexico.
The best quality turquoise still comes from Iran, but in •
tively small quantities. Recently, deposits in the Ur States
(New Mexico, Arizona, California, Nevada) r been increasingly
exploited. Much of the material tracted from these sources
is of low quality, but it is usnevertheless, after being treated
to improve its hardn•consistency, and color.
Value Because it has been fashionable for
a numbe years, turquoise is quite highly prized in relation
to corr . rable nontransparent gems, although it is fairly
plentitithe market. Its value is exceeded only by lapis lazuli
top quality jadeite jade.
Simulants and synthetics The ancient Egyptians
parently imitated turquoise with ceramic material. Morr, cently,
it has been so widely simulated by the most div, materials
that imitations are nowadays perhaps more F tiful on the market
than turquoise itself.
Ceramic material, glass, plastic, agglomerates of artil powders,
and nodules of artificially colored rock among the most common
simulants. Attractive synthetic
Below: Microcrystalline aggregate of lazurite.
turquoise has also been produced for about a decade. "
has a highly characteristic honeycomb structure, whic recognizable
under a lens. What complicates matters ~ siderably is the
fact that large quantities of turquoise put on the market
which are not of gem quality, but wh because of their extraordinary
porosity, have been imp, nated with various substances to
improve their app, ance, resistance, and ability to take polish.
The r, common cases are:
• Impregnation with paraffin or wax to enliven the cc
eliminate porosity, and make material of low hardr easier
to polish. When this treatment is carried ow good quality
material, which absorbs very little an - only slightly improved,
it is admissible.
• Impregnation with colorless or colored plastic to
enl the color, reduce britileness, and allow the specirne
take an exceptional polish. This treatment, which partial
falsification, is not acceptable.
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