Identifying Synthetic Gems: A Guide to Recognizing Artificial Gemstones

As the world of gemstones continues to evolve, the ability to accurately identify synthetic gems has become increasingly important. Synthetic gems, created in laboratories, can closely mimic the appearance of their natural counterparts, making them a challenge to distinguish. However, with the right knowledge and techniques, it is possible to confidently identify specific synthetic gems. In this comprehensive guide, we will explore the distinctive features and characteristics that can help you recognize synthetic diamonds, emeralds, lapis lazuli, opals, and spinels.

Synthetic Diamonds

Unlike their natural counterparts, synthetic diamonds have very few inclusions. However, they have two distinctive types of graining that can be used to identify them. On their surface, you may see crystal-shaped grain, usually octagonal, or an inverted triangular pattern, called "hourglass." Since these two characteristics are never found in natural gems, they positively identify synthetics.

Natural yellow diamonds usually fluoresce blue. However, they can show other colors or be inert. Synthetic yellow diamonds, on the other hand, are inert under longwave and fluoresce greenish yellow or yellow in shortwave ultraviolet light (UV).

Another key indicator of natural origin is the presence of a cape line, a strong line at 415 nm on a diamond's absorption spectrum. This feature proves the diamond's natural origin. In contrast, natural diamonds have no color zoning, while synthetic yellow diamonds often do. While a lack of zoning proves nothing, its presence confirms a synthetic origin.

Finally, magnets will attract some synthetic diamonds but never naturals. This simple test can be a reliable way to distinguish between the two.

Synthetic Emeralds

Both the flux and hydrothermal methods can create synthetic emeralds. While these lab-made emeralds share the characteristics of other gems grown from these methods, they have some special features to be aware of.

For example, some manufacturers deliberately add fluid inclusions to flux-grown emeralds that resemble a natural jardin. Biron emeralds from Australia may have gold specks or white particles known as "comet tails." Some Lechleitner synthetic emeralds are flame fusion stones, designed to imitate the more expensive flux gems. The makers grow a skin of corundum over a flame fusion beryl seed. When flux enters the seed through cracks, fingerprint inclusions form. Then, the flux skin is cut away. Look for curved striae in anything that appears to be a flux grown emerald.

Linde synthetic emerald has a thin, hydrothermal growth over a faceted piece of clear beryl. However, these gems have a dead giveaway: clearly visible crazing on the surface.

Some hydrothermally grown emeralds have a zigzag or wavy growth structure. Look for a growth pattern that resembles a field of chevrons (an unnatural pattern). You may also see something resembling the roiled effect of a hessonite garnet called "whisky in water." They may also contain internal fractures or black inclusions resembling the mica and hematite found in natural emeralds.

Synthetic Lapis

Gilson manufactures an imitation lapis, distinguished by having small, angular spots of dark blue. You can make a positive identification with UV testing. Natural lapis lazuli fluoresces weak to moderate green in shortwave, and any calcite in lapis also fluoresces pink in longwave. In contrast, Gilson lapis is inert to both longwave and shortwave.

Synthetic Opals

Lab-made opals share most of the characteristics of their natural counterparts. UV testing does allow one quick separation: phosphorescence indicates a natural opal. However, both natural and synthetic opals may lack phosphorescence, so absence proves nothing.

One defining feature of synthetics is a scale-like or "chicken wire" structure, which you can see with high magnification and bright field or overhead lighting. Also, you might find a dendritic-like structure in some synthetics. (Please note that some some natural Welo Ethiopian opals may also have a snakeskin-like, "honeycomb" pattern that resembles "chicken wire.")

Some synthetic white opal has a column-like structure, when viewed from the side with oblique lighting.

Synthetic Spinels

You'll have to distinguish most natural and synthetic spinels through their inclusions. Since natural colorless spinel is extremely rare, any such stone you encounter is most likely (but not positively) synthetic.

You'll frequently encounter synthetic spinels used to imitate other gemstones. These synthetic spinels can be challenging to identify, as they often lack the distinctive inclusions that can help distinguish them from natural stones.

In conclusion, the ability to accurately identify synthetic gems is crucial in the ever-evolving world of gemstones. By understanding the unique characteristics and features of synthetic diamonds, emeralds, lapis lazuli, opals, and spinels, you can confidently distinguish them from their natural counterparts. This knowledge not only helps ensure the authenticity of your gemstone purchases but also contributes to the responsible and ethical trade of these valuable resources.