WHAT IS THE VERNEUIL PROCESS?
The Verneuil process is a flame-melting process used to manufacture synthetic sapphires.
Pure, very fine aluminium oxide is melted using an oxidic torch (oxygen + hydrogen) at a temperature of over 2,000° Celsius.
This material falls drop by drop onto a crystalline seed which grows continuously like a stalagmite, giving rise to a crystal.
The process takes from a few hours to several days. In order for the crystal to grow, thanks to the superposition of very thin layers of molten material, it is continuously melted in the same temperature zone by a downward-facing flame.
The Verneuil process produces only small quantities of rubies, sapphires and coloured spinels. Most is grown as colourless crystal, but increasingly as raw material (crepites) for growing sapphire using other manufacturing processes.