Unlike a synthetic diamond, which has the same chemical
composition and crystal structure as a natural diamond, simulants (also
known as imitations) merely imitate the gem’s appearance. Simulants
can either be created in a factory or occur naturally.
Some of the oldest diamond imitators were made of glass, garnet and glass doublets, rhinestones, and synthetic sapphire. But probably the most familiar simulant is the cubic zirconia. Known by the household name “CZ,” it is nearly as brilliant, shimmering, and durable as a diamond.
In 1997, a stone called synthetic moissanite entered the market, closely resembling a diamond. It shared many of the same optical and physical characteristics but what really invoked controversy was that it fooled the thermal testers used to detect previous diamond simulants.
No matter how convincing it may seem, any diamond simulant will have optical or physical characteristics that can be identified by a trained gemologist. In the case of synthetic moissanite, double refraction is a dead giveaway. When you look through a large facet, you’ll see a doubling of facet junctions on the opposite side of the stone.