The Fascinating Process of Creating Lab-Grown Sapphires

People have highly prized sapphires for ages. Their beauty and hardness make them ideal choices for jewelry. The demand for sapphires, however, has long exceeded the natural supply. In fact, gem-quality corundum, which includes sapphires and rubies, is rarer than diamond. Not surprisingly, sapphires and rubies were some of the first gemstones to be synthesized over 100 years ago. Manufacturers still use some of the technological methods used then to synthesize sapphires today.

How are Lab-Grown Sapphires Made?

Whether under the Earth or in a laboratory, crystal gemstones develop or "grow" when the right combinations of minerals interact under specific chemical and physical conditions. Of course, the chief advantages of synthesizing gems in a laboratory (from the manufacturer's perspective) are time and financial savings. In a lab, manufacturers can control and even accelerate chemical and physical processes as well as combine minerals that occur rarely in nature. In effect, labs can create to order gems difficult or expensive to mine.

There are two types of methods for artificially creating sapphires: melt processes, which involve melting aluminum oxide into a sapphire droplet, and solution processes, which grow sapphire crystals in a solution.

Melt Processes

The most inexpensive and oldest melt process is known as flame fusion. In this method, a flame melts aluminum oxide powder (the principal mineral in corundum). The drops form into a long teardrop shape called a "boule." The addition of other minerals to the aluminum oxide can create colored varieties of sapphire. Also, adding chromium to the aluminum oxide will create synthetic ruby.

The Verneuil process is a flame fusion process that can create sapphires much larger than those commonly found in nature.

The Czochralski process, uses radio waves to melt the aluminum oxide. Manufacturers insert a rod tipped with a seed crystal into the mixture and slowly rotate it and pull it out, creating a column of sapphire. Although an expensive way to synthesize sapphires, it can create up to 4" of crystal per hour.

Solution Processes

Hydrothermal synthesis is a solution process that closely mimics natural formation, subjecting the minerals to intense heat and pressure in a sort of "pressure cooker." Sapphires form around a seed crystal as the mineral solution rises to the top of the cooker.

Are Lab-Grown Sapphires Really Sapphires?

Chemically and physically speaking, the same materials constitute natural and lab-grown sapphires, and they have the same atomic structure and crystal habit. Gemology labs would identify both lab-grown and natural sapphires as forms of corundum.

As a consumer, however, you may want to make a distinction between lab-grown and natural. Both can be beautiful, but it is best to know exactly what you are paying for. If you encounter a sapphire offered for sale as synthetic, you can make an informed choice to buy or not.