Recent Simulant and Synthetic Gems Found by the GIA

Gemstones are inherently in demand, and as such, there are many who attempt to either create an imitation (simulant) gemstone or create a lab-grown (synthetic) gemstone. Simulant gemstones are those that mimic another, but have different properties and compositions than the imitated gem, such as a red-dyed quartz simulating a ruby (a variety of corundum) (read more here about simulants). Whereas, synthetic gemstones are those that have the same chemical composition and properties as the imitated gem (read more here about synthetics). Synthetic gemstones are not a new concept; rubies have been known to be synthesized since the late 19th century and emeralds (a variety of beryl) since the 1930s. Undoubtedly many antique jewelry items bear synthetic gems such as ruby and emerald, and as technology and techniques advance, more and more gems are becoming replicated.

Real rhodochrosite cabochons (two on the left) and imitated rhodochrosite (two on the right). The banding of the simulant on the left is poor, but the one on the right is almost half-decent.
(image credit: Xu and Yu, 2019/GIA)

Recently, the Gemological Institute of America's (GIA) journal, Gems & Gemology, reported a rhodochrosite (MnCO3) simulant acquired from a Chinese market (Xu and Yu, 2019). This was interesting to me because many people would like to simulate precious gemstones such as diamonds and rubies, rather than minerals that are typically fashioned into cabochons, such as rhodochrosite and turquoise. The imitation rhodochrosite is made of pink-red gibbsite (Al[OH]3)) powder and white calcite (CaCO3) powder compacted and bonded together with an epoxy-like substance, possibly styrene. The researchers found that the rhodochrosite simulant was quickly evident as a fake by a trained eye, as it had "brighter color, less-complex banding, lower specific gravity, lower RI [refractive index], and poor transparency."

Synthetic ruby (left) and synthetic sapphire (right) exhibiting asterism (starburst pattern of reflected light). The ruby is 4,759 carats (2.1 lbs) and 76.96 mm diameter. The sapphire is 467.2 carats (0.21 lbs) and is 52.04 x 42.29 x 20.89 mm.
(image credit: GIA)

The GIA also recently published an online article on the seven most unusual gems analyzed by the GIA in 2019. These include (among a a few unique natural gems) a synthetic diamond grown on a natural diamond, a synthetic cyan sapphire, a diamond coated with chromium oxide to appear as a rare green color, a large sapphire exhibiting asterism (starburst reflection of light that can occur naturally in some sapphires due to inclusions), and a ridiculously large (appx. two pounds!) ruby also exhibiting asterism. While simulants and synthetics may be forged for legitimate means, such as conflict-free diamonds, others are fabricated as a means to extort. The prevalence and increasing ease for simulant and synthetic gems to be produced underscores the importance of buying gemstones from reputable and knowledgeable dealers.

Reference:
Xu, H. and Yu, X., 2019, Pressed gibbsite and calcite as a rhodochrosite imitation: Gems & Gemology, v. 55, n. 3, p. 406-416.

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