Precious Stones Of The Future From The Laboratory

An insider (s) view + tips for students studying synthetic gemstone identification course (s).

(via The Journal of Gemmology, Vol.XVI, No.7, July 1979)

A report on M. Pierre Gilson’s talk

On the 11th October, 1978, a talk was given to members of the Association by M Pierre Gilson on ‘Precious Stones of the Future from the Laboratory’ in the Geological Museum Cinema Theatre, South Kensington. The theatre was full when the proceedings were opened and the speaker was introduced by the vice-chairman, Dr David Callaghan, FGA, who said M Gilson produced the very best that man could produce and was able to do in a relatively short time things which Nature took very much longer to achieve; his talent and the vast range of materials that he was producing were quite fantastic.

M Gilson’s talk then took the form of a running commentary no the hundred or so slides which he showed during the evening and he left few people in doubt about the progress made in the last fifty or sixty years. He reminded the audience that Verneuil was the first to make synthetic ruby and sapphire at the beginning of the century: with his relatively simple method he was able to produce a boule in one of several colors in a matter of three hours or so, and his synthetic corundum was soon used to make the jewels in watches.

In contrast, M Gilson’s company takes as long as nine months to grow synthetic emeralds. They start with a seed—synthetic material of the highest quality—and grow it as a non-stop process for nine months. A continuous supply of electricity is essential, because it is important to allow crystallization to take place at a constant temperature if good crystals are to be grown. Accordingly arrangements have been made to ensure that the company is guaranteed a supply of electricity privately in case there should be a failure in the public supply due to breakdown or perhaps a strike.

But it is not just a matter of having the right equipment and know how: experimentation also is necessary. Before success in making synthetic turquoise was achieved, thirty different phosphates had to be crystallized.

The equipment now used in the Gilson laboratories is very sophisticated and quite advanced. In order to study the size and formation of the tiny ‘beads’ which make up such gemstones as emeralds an electron microscope is used. A spectrophotometer is another essential piece of equipment, because it is important to be able to control absorption to within one part per million.

With synthetic emeralds M Gilson has found it beneficial to cut at a specific angle in relation to the seed crystal on which the new material has been grown. He used slides to explain that the main difference between synthetic and natural emerald lies in the nature of the inclusions. In the synthetic material the ‘veil’ is twisted, whereas in the natural stone it is straight. He added that Nature produced only one good emerald for every million crystals formed: in the laboratory it was essential to have a very much higher success rate. Emerald production in the Gilson laboratory takes precisely nine months, since, if you wait any longer, crystallization may have stopped. A simple—but impractical! –test to distinguish between natural and synthetic emerald was mentioned: if you heat it to one thousand degrees and it turns white when it cools, you know it is natural. He added that the hardness of emerald was affected by the extent of inclusions in a given stone.

Opal was next discussed. Opal is pure silica: it acts like a prism and the colors which can be seen are pure spectral colors. Gilson synthetic opals contain more pure colors than natural material because they contain more pure constituents. Laboratory production of opal calls for a very high temperature: natural opal is no longer being created because temperatures are not high enough. Even in the laboratory it is impossible to produce two identical opals. Production starts with the production of millions of tiny beads, each about 0.3 microns in diameter, and these eventually form the finished material. M Gilson’s most recent improvements involve the removal of all traces of water from synthetic opals, and this gets rid of cracks and helps to avoid some of the hazards associated with the natural material. With natural opals, it is interesting to note that material found at depth of more than six meters is often noticeably better than stones found near the surface.

Natural turquoise contains iron, and in some cases customers are disappointed when the iron turns green after a year or two. ‘Our own stones are pure turquoise, so this problem doesn’t arise’—but a process has now been developed so that iron can be introduced to the surface of synthetic turquoise.

With lapis, although pyrites (its inclusions) can be synthesized, M Gilson uses natural pyrites. ‘Each day nine hundred tons of natural pyrites are mined: I cannot compete with that!’ He is now successfully synthesizing coral and used calcite which is now being mined in France.

In answer to a question whether he could suggest any methods of testing stones to tell the difference between real and synthetic specimens, he said: ‘We work on developing new scientific products, but when it comes to identification you are the experts.’ Asked whether it was his intention to produce stones so similar to the natural product that they could not be detected, he replied: ‘We are not competing with Nature but merely trying to improve on it by producing more pure stones—more beautiful ones for the jeweler to work with.’

Mr Alec Farn asked if M Gilson had produced any emeralds without chromium but with the addition of vanadium, and M Gilson replied that he had not—and even if it was done, could the result be described as emerald?’ ‘If people want chromium in emerald, then why shouldn’t we give it to them?’

Offering a tip for improving opals, M Gilson said that if soaked over night in ethyl alcohol all moisture in the stone would be driven out and the color improved—but it was essential not to do this if the stone was a triplet! And in reply to an enquiry whether he had carried out any experiment on the jadeite family, he smiled and said: ‘Yes, we are working on this problem.’

When asked how long he had been trying to make synthetic stones before he had his first success, he said he took fifteen years to succeed with emerald, ten years with opal, and eight years with turquoise: and because of slow reactions and the length of time it took to grow a single crystal before it was known whether or not the experiment was a success, research was becoming more difficult and expensive. Some members of the audience were surprised when M Gilson mentioned that his main business was not the production of synthetic gemstones but the manufacture of about nine tons of ceramics each month for industrial use.