Flame Fusion

Flame fusion, discovered in 1902 by Auguste Verneuil, was the first successful process creating synthetic gemstones. Using powdered elements and high temperatures he was able to grow crystals in a laboratory. Initially, rubies were the only gems produced by this method. Eventually it was determined that by altering the elements put into the melt, other gems could be produced. In the 1940's Union Carbide used this process to create the famous "Linde Star" sapphires.

Verneuil process diagram svg.png
The process works as followed. Powdered aluminum oxide travels towards a flame. The 2000 degree heat is created by that flame melts the powder and droplets are formed. These droplets then drop onto a slowly turning earthen rod and, upon cooling, crystallize in to a boule. The outside looks like a cylinder but inside, the newly created synthetic gem material, has the crystal structure of the natural gem material. Color can be induced by adding certain chemical elements to the aluminum oxide powder mix. Chromium to create ruby or Titanium and iron to make blue sapphires are the two most produced examples but just about any color can be created with this method.

An alternate name for this process is Verneuil after its creator.

Rendering of the early Verneuil Synthesis Machine.
A tell-tale feature of Verneuil corundum: curved stria
A second typical feature of Verneuil corundum: clouds of small gas bubbles