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 Simulant, imitation |
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 A short recall |
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 Gem: these are natural stones having
the appearance of diamond like quartz, sapphire, beryl, topaz, zircon.
Natural
synthetics: these are manufactured stones that have the same
chemical composition, atomic structure, and physical properties of a natural
counterpart. They are man made and includes: synthetic rutile, synthetic
sapphire and synthetic spinel.
Artificial
synthetics: these are the manufactured stones that have no natural
counterpart and include: strontium titanate, yttrium aluminate (YAG) and
cubic zirconia.
Imitations: glasses of differing
densities.
Composites-doublets: stones were
often constructed from more than one stone to enhance particular properties. |
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| Simulants, imitations, |
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 Simulant,
imitation is a material that imitates the appearance of a gem without
duplicating its properties (glass, plastic, etc.). |
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The main simulants: |
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Very old: |
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Glass |
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Grenat-glass doublet. |
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Old: |
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Synthetic corundum. |
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Synthetic spinel. |
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Diamond-diamond doublet. |
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After the last war: |
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Synthetic rutile. |
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Strontium titanate (« Fabulite »). |
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YAG (Yttrium Aluminum Garnet). |
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GGG (Gadolinium Gallium Garnet). |
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Synthetic cubic zirconia (CZ). |
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Moissanite. |
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Recognition: |
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Optical
properties: the imitations with low index of refraction let pass the light. |
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Polish
resistance: imitations have « soft » edges. |
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Hardness: diamond and carborundum are
not scratched by corundum. |
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Tools: |
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The
reflectometer: estimates the reflecting capacity
of the stone tested in infrared compared to a diamond. Certain
substances can give the same result as diamond (ilmenite...). |
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The
conductimeter: estimates the thermal conductibility of
the stone tested. Be careful with the very conducting substances
(gold, silver), with the small stones (less than 0.05 ct) and
with synthetic corundum which is a good thermal conductor. |
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Diamond tester:
electronic diamond testers works by measuring the loss of heat
from a metallic probe. Diamonds are excellent conductors of
heat and will draw the heat from the probe faster than
simulants. Be careful to test the stone at various places
(example: table + pavilion, be careful with doublets). |
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The simplest method to
detect imitations consists in tracing a black line on a quite
white paper sheet and to place the table of the stones to be tested
on the black line. If you see the black line through the stone, it is
an imitation. Be careful, with cubic zirconium oxide, synthetic rutile, fabulite
and certain doublets which escape this rule. |
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| Synthetics |
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Synthetic stones are
materials whose crystallization was caused partially or completely
by man and they have the same optic and physic characteristics
that their natural equivalents. |
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To detect the
synthetic stones from a real diamond, there is a simple process which
consists to cloud the stone with your breath. The stone to be tested must have
the culet facing up. Mist disappears much more quickly from the surface of the diamond
than on a synthetic stone. The ideal is to have a true diamond which will be used as reference
compared to the stone tested. |
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The moissanite
is the most perfect substitute of diamond. It is not easy to detect on
the jewels. Index of refraction: 2.65 to
2.69. Hardness: 9.25.
Density: 3.21. Thermal conductibility: very high. Observe
the doubling of the edges. Do not hesitate to dismount the stone if in doubt. |
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The cubic
zirconium oxide is the second perfect substitute of diamond, but
it is denser than diamond. Refractive Index: 2.16. Relative
Density: 6. Dispersion: 0.060. Hardness: 8.5. |
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| Assembled stones: doublets |
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Assembled stones: |
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The doublets are
two pieces of gem material fused together by heat (example:
garnet and glass doublets) or two pieces of gem material cemented
together with a colourless cement (example: opal doublet).
The triplets are two pieces of gem material cemented together with
a coloured cement (imparts colour to the stone) or three pieces of gem
material cemented together with a colourless cement (opal triplet). |
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Emerald imitation (doublet) |
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| Diamond imitation (doublet) |
Ruby imitation (triplet) |
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Recognition: |
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Place the stone
on a white paper, the culet facing up. Observe with the naked eye. A red
circle is visible. In the case of a red stone or dark colour, the circle
is not detectable. |
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Joining by fusion
can have bubbles organized on a plan. Rutile needles present in
garnet can be visible. They are the sign of a natural stone.
Association bubble-needles is the proof of a doublet garnet-glass. |
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Other examples exist, like doublet enamel. |
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0.82 carat H-SI1 |
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1.73 carat E-SI2 |
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0.28 carat H-SI1 |
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1.19 carat H-VVS2 |
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0.85 carat H-VS2 |
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| Price: £ 1,852 |
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| Price: £ 11,622 |
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| Price: £ 252 |
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| Price: £ 7,230 |
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| Price: £ 2,251 |
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