Question: Which laboratory method creates the best synthetic corundum for faceting?
By International Gem Society 2 minute read
synthetic corundum gems

Synthetic corundum gems, all 8 x 10 mm. Photo © Joel E. Arem, PhD, FGA. Used with permission.

Answer: It all depends on why you want to facet synthetic corundum in the first place. Do you just want to cut a beautiful gem, or are you going to sell the finished gem?

Flame Fusion vs Hydrothermal Synthetic Corundum

There are many ways to synthesize gem-quality corundum, both ruby and sapphire gems. Flame fusion is the least expensive method of synthesizing any stone. Hydrothermal synthesis is the most expensive. This involves growing a crystal from a solution under great heat and pressure. Not only is the equipment for this process expensive, it also takes weeks or months to grow crystals. However, hydrothermal is the synthetic technique that mimics most closely natural gemstone formation.

There are other methods of making corundum, too, such as the flux solution method. Their manufacturing costs are just slightly higher than flame fusion.

Chatham ruby crystals

Chatham rubies are created via a flux solution method. The largest of these Chatham ruby crystals measure about a half-inch across. Photo © Joel E. Arem, PhD, FGA. Used with permission.

Which Process Yields the Best Gemstones?

Distinguishing natural from lab-made rubies and sapphires takes magnification and careful analysis. With this in mind, flame fusion rubies and sapphires are a fine choice for most faceting. If you simply want to cut a beautiful stone, flame fusion is your best option.

However, if you want more value from your finished stone, use a hydrothermal. You may be able to sell your faceted hydrothermal ruby or sapphire for a higher price than a flame fusion stone. Most synthetics won’t command the same prices as natural stones. However, natural gem-quality rubies and sapphires are so rare, a quality hydrothermal synthetic could still sell for a good price.

The best synthetic corundum, bottom line, is what will give you the best return for your effort.

Donald Clark, CSM IMG

Verneuil Process Boules

Rubies and sapphires are some of the most prized gemstones in the world and were also some of the first to be created in a laboratory. These synthetic corundum boules were grown by Auguste Verneuil and associates around 1900 (before he published his notes on his Verneuil process). Photo © Joel E. Arem, PhD, FGA. Used with permission.