There are many different production methods used to create
synthetic gems, but they all fall under two major types:
Melt growth and
Two common melt-growth methods are Verneuil flame fusion
(or just “flame fusion”) and Czochralski pulled-growth.
(a) Flame Fusion
The first technology utilized for growing gemstones in a
laboratory, flame fusion is still very widely used to create rubies, sapphires,
and spinel. It’s inexpensive, but yields low quality gems. These created gems
are often used in “class rings” and cheap jewelry found in discount stores. It’s
relatively easy for any competent jeweler to detect synthetics created by flame
fusion methods because the “dripped” molten material forms “growth striae”
(thin, narrow grooves) as it hardens.
Czochralski pulled-growth is also commonly used to create
rubies, sapphires, and spinel. It’s a more complex and costly method, and
creates better gems than flame fusion.
Still, both these methods yield gems of questionable
quality. Because they use very high temperatures, it is difficult for
manufacturers to achieve uniform color (particularly in rubies and blue
sapphires). The mechanical action of melting and reforming crystals introduces
non-uniformity’s in the gems, which scatter light and give the stone a “dead”
look — like a piece of colored glass.
Some believe that solution growth leads to higher quality
gems than melt-growth. There are two common solution growth techniques: flux and
(a) Flux Method
In addition to creating the “big three” (emerald, ruby, and
sapphire), the flux method is used to grow spinel and alexandrite. This method
uses a supersaturated chemical bath to form the crystals. Flux Method or Flux
Fusion — not to be confused with Flame Fusion — creates the highest quality and
most expensive synthetic corundum (rubies and sapphires).
(b) Hydrothermal Method
High quality emerald, as well as the less common
aquamarine, morganite, and beryl, can be lab grown by the hydrothermal method.
It uses a water solution at very high temperature and pressure and takes several
months to create a batch of gems. That’s one of the reasons higher quality
created gems cost so much more.