The first mass-produced synthetic rubies were created by French chemist Auguste Verneuil sometime between 1891 and 1902 using the process that now takes his name. Eearlier Geneva Ruby synthetics from around 1885 were probably created using a very similar method by persons unknown, but Verneuil was the first to produce these stones in commercially viable quantities (by 1910 Verneuil had 30 furnaces running with an annual production of 1,000 kg (2,205 lb) of synthetic ruby.
The Verneuil process is still used today to create synthetic rubies, although other processes are also used.
The process involves melting high purity aluminium oxide (alumina) - containing small amounts of chromium oxide as a colouring agent - with a flame of around 2000 °C (3,600 °F). Droplets of molten alumina gather on the end of a support rod held below the alumina feed. As the rod is lowered, ruby builds up on the top of the rod, and as molten material is added to the top, it crystallizes into a single long cylindrical ruby crystal, called a boule.