Identifying the Diamond Simulant

Published: 27th August 2008
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Diamond simulants are gemstones (natural or synthetic) that resembles a diamond and is mostly confused for a natural diamond. Diamond simulant is different from synthetic diamond where synthetic diamonds are man made and has almost the same chemical and physical properties of a natural diamond. Diamond simulants differ completely physically and chemically from a natural diamond. They just imitate natural diamond.

While some differences between a diamond simulant and a real diamond are easy to identify, there are others that can be challenging. It is important to know some basic facts that will allow you to differentiate and therefore keep yourself from being cheated.

Though each diamond simulant has its own physical properties and differs from the diamond in various ways, there are some properties where the differences are common. For example, all diamond simulants are softer than the diamond. Therefore, each of the diamond simulants is likely to have rounded edges and cut. The surface of the simulant is likely to get scratched easily. Even when the simulant is new, it cannot match the clarity and brilliance of the diamond itself. These small differences can easily be observed under a microscope. Sometimes, the naked eye is enough to identify these differences.

All diamond simulants have a higher specific gravity than that of the diamond. This means that if we have a diamond and a diamond simulant that is exactly the same in size and shape, the simulant will weigh more.

The thermal conductivity of the simulants is lower than that of the diamond. Therefore the diamond is a cooler substance and feels cooler than the simulants on touch. A mechanical tool called the thermal tester, diamond tester or the diamond probe can be used to determine this. The tip of the tester should be touched with the face of the diamond and care should be taken to avoid touching any metal (if the diamond is mounted). The tester heats the stone and assesses whether it is a synthetic diamond or a natural one based on the rate at which the heat is absorbed and transmitted.

There are however certain other characteristics of specific diamond simulants that one needs to know about to be able to differentiate between the diamond and its simulant.

Glass - This simple and extremely available diamond simulant has been used as a proxy since the 1700's. This was made possible when the Europeans discovered that they could add lead oxide to glass to increase its dispersive property and brilliance. Even with this treatment, glass has much less brilliance, hardness and dispersion. The dispersion of glass is so low that one can see through a faceted glass stone; something that is not at all possible if a real natural diamond is symmetrically faceted.

Doublets - The garnet and glass doublet has been used as a diamond simulant since the 1840's. A colorless or pale color thin layer of garnet is fused to a glass base to create this effect. The hard garnet provides the lustrous and polished look. The fact that the garnet layer is extremely thin allows the coupled gem to look colorless from the face-up.

All that is needed to identify the diamond simulant is a simple rocking of the gem under a light. The difference in luster of the harder garnet and the glass makes it evident that the stone is a doublet and not a genuine diamond.

The garnet and glass doublets can be commonly seen in some antiwue jewelry. They are no longer the preferred doublet option for modern jewelers. INstead synthetic spinels or synthetic sapphires crowns and strontium titanate are used nowadays.

Colorless synthetics- Sunthetic sapphires and spinels are also used as diamond simulants. They are harder than the previously used simulants and provide better brilliance. However, the luster, brilliance and durability does not even come close to that of the natural diamond. The fact that the spinel is extremely inexpensive to produce makes it a favorite for imitation jewelry.

Zircon - Even though natural zircon is not used very commonly as a diamond simulant any more, it was used as one earlier. The natural zircon has more brilliance than glass. However, unlike the natural diamond which is single refractive, zircon gemstone is double refractive. This means that if you look a line through a zircon, you are likely to see two lines on the other side. This feature makes it fairly easy to identify a zircon when it is used as a diamond simulant. The reason why the use of the zircon reduced over the years is because it chips and scratches very easily.

Synthetic Rutile - A gem with relatively low hardness, a synthetic rutile has high levels of brilliance. Actually the rain bow colors that it disperses are so intense that they take away from the luster. This rainbow colors are obvious even to amature gemologists. The synthetic rutile is also doubly refractive.

Strontium Titanate -Singly refractive and highly dispersive, this diamond stimulant is less hard and not too durable.

YAG (Yttrium aluminium garnet) and GGG (Gadolinium Gallium Garnet) - With a high level of hardness and good brilliance, YAG was one of the more popular diamond simulants till better ones appeared on the scene. GGG is more dispersive and is almost as brilliant as the diamond itself. However, its disadvantage lies in its lack of hardness and the fact that it scratches easily.

Synthetic Cubic Zirconia - A great simulant of the diamond the synthetic cubic zirconia has comparable brilliance and luster. The durability is also high with a hardness of 8.5-9 on the Mohs scale. The one way in which the simulant can be identified is by checking the specific gravity of the stone which will give away the fact that it is much heavier than the diamond.

Synthetic Moissanite - With a hardness of 9 on the Mohs scale, synthetic moissanite is one of the hardest simulants of the diamond. A good balance of brilliance and fire gives this stone a good and attractive appearance. The synthetic moissanite gemstone is a double refractive, but the doubling of back facets effect can only be seen under higher magnification when the gem is tilted. This stone is one exception to the specific gravity rule and the specific gravity of the synthetic moissanite is lower than that of the diamond. It is one simulant that can fool most gemologists easily since it sometimes gives a clearance on the thermal test too. Therefore, if the thermal tester indicates the gemstone as a diamond, other tests should be performed to ascertain whether the stone is not a natural diamond or a synthetic moissanite.

The similarities of these simulants with the diamond make them extremely marketable and appealing. The issue however, is whether the trader and sellers disclose the real status of the gem while trading it.


Mithun Rao holds a professional degree in gemology and jewelry design from Mumbai and has spent more than 10 years in the industry. He manages his own jewelry store and takes out the free time to write and maintain his site on gemstones and diamond industry.

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