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colored varieties are seldom seen in the gem trade.
Rutile Is too Soft to be useful as a gemstone (hardness
6-61/2 on the Molls scale). But its dispersion is about
six times higher than that of diamond. Cut rutile therefore
blazes with myriad colors.
The color display is so dazzling and breathtaking that
cut rutile loses credibility as the diamond it is supposed
to imitate. There is simply too much color to be "real."
Cut
rutile, often sold as “Titania," is still available,
but has lost much of its initial popularity to other,
more suitable, diamond imitations.
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Some
other synthetic materials that have natural analogs
include: Scheelite (calcium tungstate); apatite (calcium
phosphate); wulfenite (lead molybdate); Proustite (silver
arsenic sulfide); gahnite (zinc alumi¬nate, a variety
of spinel); periclase (magnesium oxide); fluorite (calcium
fluoride); zincite (zinc oxide); bromellite (beryllium
oxide); feldspar (aluminum silicate); zircon (zirconium
silicate); phenakite (beryllium silicate); and Sphalerite
(zinc sulfide).
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All
of these have probably been cut as curiosities for gem collectors.
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Other Synthetic Gems |
| Other
Synthetic Gems
In recent years, Pierre Gilson of Paris has introduced
three remarkable synthetic gems: opal, turquoise,
and lapis lazuli. It is now known that the color
flashes in precious opal are due to the regular
accumulation of layers of minute spheres. Gilson
has duplicated this process in the laboratory,
and his synthetic black and white opal is spectacular
and natural looking.
Careful
tests may be required to distinguish it from natural
opal.Gilson turquoise resembles the finest Persian
turquoise. I¬ tremely uniform in color and
texture, and available in cut stone or ¬rough
blocks. Under the microscope this turquoise consists
of an gate of tiny spheres of uniform size, allowing
it to be readily distin- guished from natural
turquoise.
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Another
recently introduced synthetic gem is alexandrite.
The corundum with an alexandrite-like color change,
but rather a synthetic Chrysoberyl with suitable
impurities added. The color change is green to
red, resembling Russian alexandrite. Cut gems
several carats in are available, but the cost
is high for a synthetic-in the ran synthetic emerald. |
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Synthetic
rutile, titanium oxide, appeared on the market in 1948, under
various trade names. Natural rutile is nearly always opaque
very dense, deep-red color. Synthetic rutile is made by the
Very process in a variety of colors, including brown, yellow,
red, and blue. Completely colorless stones could not be made,
and always have tinge of yellow.
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