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 It
is important to know the difference between a synthetic diamond and a
diamond stimulant. A synthetic diamond is a real diamond created by
industrial processes. Whereas a diamond stimulant is a material used to
simulate the appearance of a diamond.
It is important to distinguish
that a synthetic diamond is a true diamond created by a technological
process, whereas a diamond stimulant is defined as a non-diamond
material that is used to simulate the appearance of a true diamond. The
demand for rough diamond by industrial sectors is satisfied by synthetic
diamonds, which saves more precious natural mined diamonds from being
used in industry. But through the advancement in technological
processes, synthetic diamonds have also reached such a quality that they
have also penetrated the gem diamond market. Synthetic diamonds have
been in production since 50 years.
A gem quality diamond is more
appearance dependant as compared to its physical properties. This has
lead to development of imitations and few procedures that enhance the
appearance (especially color) of a diamond. Materials having similar
characteristics to a diamond but are neither mined nor synthetic fall in
the category of diamond stimulants.
Currently, trained
gemologists with appropriate equipment are able to distinguish natural
diamonds from all synthetic and stimulant diamonds, and identify all
enhanced natural diamonds. The established natural diamond industry has
a vested interest in maintaining the distinction between natural
diamonds and other diamonds, and has made significant investments toward
that end. However, as manufacturing technology improves, synthetic
diamonds may become indistinguishable from natural diamonds, and new
techniques for creating and treating stimulants (such as coating them
with a very thin diamond-like layer of carbon) are making it
increasingly difficult to distinguish stimulants from real diamonds.
Cubic
Zirconium
One most
popular example for a diamond stimulant is cubic zirconium (CZ). CZ is
pure zirconium oxide (ZrO2), a mineral that is extremely rare in nature.
It is widely synthesized for use as a diamond stimulant. The synthesized
material is hard, optically flawless and usually colorless, but may be
made in a variety of different colors. It should not be confused with
zircon, which is a zirconium silicate (ZrSiO4). Because of its low cost,
durability, and close visual likeness to diamond, synthetic cubic
zirconium has remained the most geologically and economically important
diamond stimulant since 1976. Its main competition as a synthetic
gemstone is the more recently cultivated material called synthetic
moissanite.
Moissanite
Moissanite
(Silicon Carbide) is somewhat similar to diamond in several important
ways: it is transparent and hard (8.5-9.25 on the Mohs scale compared to
10 for diamond), with a refractive index between 2.65 and 2.69 (compared
to 2.42 for diamond). Moissanite is somewhat harder than common cubic
zirconium. Unlike diamond, Moissanite is strongly birefringent (Double
Refraction). This is a desirable in some optical applications, but is
not desirable in gemstones. For this reason, Moissanite jewels are cut
along the optic axis of the crystal to minimize birefringence. It is
lighter (density 3.22 vs. 3.56), and much more resistant to heat. This
results in a stone of higher luster, sharper facets and good resilience.
Loose moissanite stones may be placed directly into ring moulds; unlike
diamond, which burns at 800 °C, moissanite remains undamaged by
temperatures up to twice the 900 °C melting point of 18k gold.
Sophisticated thermal probes are able to differentiate simulated
moissanite (synthetic silicon carbide) from diamond, and Charles &
Colvard also manufacture their own proprietary device which relies on
simulated moissanite's (synthetic silicon carbide) greater opacity to
ultraviolet light.
Quartz Crystals
Natural
minerals which (after cut like diamonds) optically resemble white
diamonds are rare, because the trace impurities usually present in
natural minerals tend to impart color. The earliest stimulants of
diamond were colorless quartz, topaz, and beryl (gahnite). All these are
common minerals with above-average hardness (7–8), but all have low
Refractive Indices and correspondingly low dispersions. Well-formed
quartz crystals are sometimes offered as "diamonds," a popular example
being the so-called "Herkimer diamonds" mined in Herkimer County, New
York. Topaz's SAG (3.50–3.57) also falls within the range of diamond.
Zircon
The most
notable natural stimulant of diamond is zircon with a hardness of 7.5,
and shows perceptible fire when cut, due to its high dispersion of
0.039. Colorless zircon has been mined in Sri Lanka for over 2,000
years; prior to the advent of modern mineralogy, colorless zircon was
thought to be an inferior form of diamond. It is still encountered as a
diamond stimulant, but differentiation is easy due to zircon's
anisotropy and strong birefringence. It is also brittle and often shows
wear on the girdle and facet edges.
Fancy-colored
diamonds are also imitated, and zircon serves this purpose very well.
Application of heat treatment to brown zircon can create several bright
colors, most commonly sky-blue, golden yellow, and red. Blue zircon is
very popular, but not necessarily color stable; prolonged exposure to
ultraviolet light (including the UV component in sunlight) tends to
bleach the stone. Heat treatment also imparts greater brittleness to
zircon and characteristic inclusions.
Shelite
Much less
common than colorless zircon is colorless sheltie. Its dispersion
(0.026) is also high enough to mimic diamond, but although it is highly
lustrous its hardness is much too low (4.5–5.5) to maintain a good
polish. It is also anisotropic and fairly dense (SAG 5.9–6.1). Synthetic
sheltie produced via the Czochralski process is available, but it has
never been widely used as a diamond stimulant. Due to the scarcity of
natural gem-quality sheltie, synthetic sheltie is much more likely to
simulate it than diamond.
Cerussite
Another
similar case is orthorhombic carbonate cerussite, which is so fragile
(very brittle with four directions of good cleavage) and soft (hardness
3.5) that it is very rarely set in jewelry, and only occasionally seen
in gem collections because it is very difficult to cut. Cerussite gems
have an adamantine luster, high RI (1.804–2.078), and high dispersion
(0.051), making them attractive and valued collector's pieces. Aside
from softness, they are easily distinguished by cerussite's high density
(SAG 6.51) and anisotropy with extreme birefringence (0.271).
Sphalerite
Sphalerite
(zinc blende) is another fragile gem quality mineral and varies from
strong yellow to honey brown, orange, red, or green. Its very high RI
(2.37) and dispersion (0.156) make for an extremely lustrous and fiery
gem, and it is also isotropic but has very low hardness (2.5 to 4 on
Mohs scale).
Other
Garnet Group Minerals
Some
members of Garnet group such as grossularite (usually brownish orange,
rarely colorless, yellow, green, or pink) and andradite (the rarest and
most costly of the garnets, with three of its varieties—topazolite
(yellow), melanite (black), and demantoid (green)) is sometimes seen as
diamond stimulant. Demantoid (diamond-like) has been prized as a
gemstone since its discovery in the Ural Mountains in 1868. It has been
noted in antique Russian and Art Nouveau jewelry.
Sphene
(titanite) has also been recognized in antique jewelry and has a luster
and dispersion properties high enough to be mistaken as a diamond but is
soft and anisotropic (a high birefringence of 0.105–0.135).
Titanate
Another
diamond stimulant is glass and strontium titanate doublets. The two
materials are used for the bottom portion (pavilion) of the stone, and
in the case of strontium titanate, a much harder material, usually
colorless synthetic spinel or sapphire, is used for the top half
(crown). In glass doublets, the top portion is made of almandine garnet.
It is usually a very thin slice which does not modify the stone's
overall body color.
In strontium
titanate and diamond-based doublets, an epoxy is used to adhere the two
halves together. The epoxy may fluoresce under UV light, and there may
be residue on the stone's exterior. The garnet top of a glass doublet is
physically fused to its base, but in it and the other doublet types
there are usually flattened air bubbles seen at the junction of the two
halves. A join line is also readily visible whose position is variable;
it may be above or below the girdle, sometimes at an angle, but rarely
along the girdle itself.
The most
recent composite stimulant involves combining a CZ core with an outer
coating of laboratory created amorphous diamond. The concept effectively
mimics the structure of a cultured Pearl (which combines a core bead
with an outer layer of Pearl coating), only done for the diamond market.
Brought to market under the 'Asha' brand name, the finished stimulant
provides a more lustrous and diamond-like look than plain CZ due to its
usage of amorphous diamond.
Diamond Enhancements
Diamond enhancements are performed on natural as well as synthetic
diamonds to improve their gemological characteristics. Enhancements are
usually performed on the diamonds already cut and polished. Enhancements
include clarity treatments to remove inclusions, such as laser drilling,
application of sealants for filling cracks, color treatments for
improving a diamond’s color grade...
Read more...
Read about Diamond
History, Diamond Facts and More......
A symbol of innocence,
justice, faith and strength, the diamond was believed to make its
wearers courageous and victorious over their enemies. When set in gold
and worn on the left side, it held the power to drive away nightmares
and soothe savage beasts. Diamonds were even thought to be so powerful
that they could stop lechery.
Diamonds have lured and
fascinated us for centuries. Their ores and lore recorded romantic and
bloody events in the past. Diamonds have been long cherished and sought
after, fought over and killed for in the human history simply because of
its beauty and the fascination....
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Information Summary...
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Diamond Substitutes
