Synthetic Corundum


Year Event
Corundum Xtal Layer.png

The basic identity of ruby and sapphire was identified

Robert Hare of Philadelphia invents oxyhydrogen ('gas') blowpipe

Guy-Lussac found that heating ammonium alum would obtain pure aluminum oxide. Synthesizing corundum was on its way!

E.D. Clarke publishes details of his experiment with a gas blowpipe:
...two rubies were placed upon charcoal and exposed to the flame of the gas blowpipe... after suffering it to become cold... the two rubies were melted into one bead.[1]


A series of experiments began with Gauding and later by Fremy. No success as they did not have the technology to maintain consistent temperatures needed: 2050°C. Gauding gave up his attempts in 1870.


The young Auguste Verneuil applies for the position of lab assistant under Fremy at the Paris Museum of Natural History.


Verneuil became Fremy's lab assistant. At a certain point Fremy found out that using a flux of potassium hydroxide and barium fluoride made it possible to dissolve the raw ingredients at 1500°C. Gradual cooling would then cause the ingredients to crystallize. In this way Fremy created small rhombohedral crystals up to 0,3 ct

It could be argued that since experiments were conducted with several flux agents like potassium hydroxide and barium fluoride,the final product, although described as rhombohedral ruby crystal, was actually red, violet, and bluish in color.[2] Ruby synthesis was understood and repeatable. The Al+3 would simply be replaced by trace amounts of Cr+3 and a ruby would result every time. Further experiments produced xls of several tones of "bug juice", which could technically be termed sapphire, even though they were not a fine blue color. The problem: Creation of various colors (aside from red) were not repeatable as the chemistry of the specific chromophore, needed to obtain colors other than red, was not understood at that time.


Synthetic rubies, later to be called Geneva rubies were shown to P.M.E. Jannettaz, a gem expert at the Paris museum where Verneuil and Fremy worked. Spherical bubbles were observed and after some research it was concluded that the stones weren't natural. Verneuil was asked to replicate the process and he managed to fuse some powdered alumina containing a small amount of chromium with the aid of a oxygen-hydrogen torch. Tiny specimens were the result. This event and Verneuil's realisation that it was possible to produce synthetic corundum through fusing the raw ingredients changed the way Verneuil was thinking. Over the next years Verneuil must have developed his flame fusion method of synthesizing corundum.


Verneuil deposits a sealed envelope containing the major details of his method. Larger crystals were already produced but Verneuil hadn't figured out yet how to tackle the tension in the boules that caused cracking. Fremy publishes a summary of his research and illustrations of his flux rubies.


Verneuil drops off a second sealed envelope that contains writings on how to prevent and solve the tension problem.


Fremy dies.


Verneuil's assistant displays several new synthetic ruby crystals at the Paris World's Fair.


Verneuil officially announces that he succeeded in the manufacture of scientific rubies that are equal to genuine ones and large enough to be used in jewelry.

Verneuil torch sketch.png

Verneuil publishes his paper: Reproduction artificielle du rubis par fusion making it possible for anyone with chemical and mechanical know-how to reproduce his rubies.


Worldwide annual production of Verneuil rubies reaches 5 million carats.


Paris firm of Abraham A. Heller, supplier and manufacturer of imitation stones (doublets, imitation pearls, and the new synthetic ruby) wanted to add synthetic blue sapphire to their bag of tricks. They hired Verneuil to head their lab, as they were quite confident he would be able to sort out the chemistry.

Verneuil began testing sapphires and found the blue ones consistently contained iron and titanium. He found that the addition of iron and titanium in place of chromium would reliably produce the desired blue result. (in this case, 2 Al+3 atoms would be replaced by one each Ti+4 and Fe+2)

3/28/1911 and 9/26/1911

Two US patents were awarded to Verneuil, and his employer, the Heller Company, described as "closely resembling natural sapphires as possible" and "having beneath its surface bubble-like spots bounded with rounded walls."


J. Czochralski developes the basic apparatus necessary to produce the so called pulled crystals.


Experiments with the growth of synthetic rubies by the hydrothermal method are conducted at Bell Labs


Carroll Chatham introduces his flux melt 'cultured rubies' after years of experimenting.

FF boule.jpg

It was not until 1968 that the actual mechanism behind the color of blue sapphire was explained as intervalent charge transfer, but the precise chemistry of BLUE sapphire is still a matter of some debate within the mineralogical community.
It was in this year as well that the first Kashan synthetics came out of Truehart Brown's laboratory.


Knischka flux-grown rubies are introduced.


Ramaura flux rubies are first produced.


Ken Scarratt reports on 'float zone' synthetic corundum being produced by Seiko

1993 Douros synthetic flux rubies are introduced to the world
Numerous corporations produce Verneuil synthetic sapphires and spinels

Great Article on the History of Synthetic Corundum

Online G&G articles on synthetic corundum

  1. E.D. Clarke. 1819 (as quoted by Hughes, 1996)
  2. Kurt Nassau, Gems Made by Man, Fremy's Work, p. 39