Synthetic Gemstones

Synthetic gemstones are made in factories or laboratories, not in rocks. They have virtually the same chemical composition and crystal structure as natural gemstones. So, their optical and physical properties are very similar. However, they can usually be identified by the difference in their inclusions. Many gems have been synthesized in the laboratory. Yet, only a few are produced commercially – generally for scientific or industrial purposes.

Sometimes, synthetic ruby crystals are grown in a crucible.

Shapes and Colors

Because of the way they are made, synthetic gems may show the subtle differences in shape and color that help to distinguish them from their natural counterparts. For instance, corundum produced by flame fusion has curved growth lines, rather than straight ones. That is because the ingredients have not mixed together fully. Some synthetic gems may also suffer from uneven color distribution.

Flame-fusion spinel is manufactured to imitate gems such as sapphire, ruby, blue sapphire, aquamarine, peridot, tourmaline, zircon, and chrysoberyl.

Distinct Inclusions

Synthetic gems have different inclusions from natural gems. So, often the best way to tell them apart is to examine them with a loupe or a microscope. Synthetic inclusions may be typical of a process, or of a synthetic gem species. For instance, in Verneuil rubies, gas bubbles have a well-defined outlines; in flux-melt emeralds, characteristic ‘veil’ and ‘feather’ patterns form.

Gilson Gems

Turquoise, lapis lazuli, and coral produced by the French manufacture, Gilson, are similar to their natural counterparts. However, they are not true synthetics because their optical and physical properties differ from the natural gems. Gilson lapis lazuli, for example, is more porous and has lower specific gravity.

Gilson Emerald Inclusions

Synthetic emerald from the French manufacturer, Gilson, has characteristic veil-like inclusions. The gems are made from poor-quality material by a flux-melt method.

Identifying Synthetic Gems

A hand-held lens is powerful enough to assist in gem identification. With its 10x magnification, it may be possible to distinguish between natural and synthetic inclusions.

Making Synthetic Gemstones

Man has tried to replicate gems for thousands of years. However, it was not until the late 1800s that any substantial success was achieved. In 1877, French chemist Edmond Fremy grew the first gem-quality crystals of reasonable size.

1. Verneuil Method

Around 1900, August Verneuil devised a technique to produce ruby. With a few modifications, the Verneuil flame-fusion method is still in use today.

The powdered ingredients are dropped into a furnace and melt as they fall through a flame hotter than 2,000 degrees, fusing into liquid drops. These drip onto a pedestal and crystallize. As the pedestal is withdrawn, a long, cylindrical crystal, which is known as a boule, forms.

2. Flux-Melt Technique

Pioneered by the French chemist Edmond Fremy, he grew emerald crystals of a reasonable size. Similarly, he grew ruby crystals by melting aluminum oxide and chromium in a crucible.

The flux-melt technique is still used to make emeralds. The powdered ingredients are melted and fused in a solvent (flux) in a crucible. The material must be kept at a very high temperature for months, before being left to cool slowly.

3. Flame-Fusion Corundum

Synthetic corundum manufactured by flame-fusion grows as a single mass called a ‘boule.’ It has the same inner structure as a natural crystal and can be cut to shape.