A few years ago, I had the pleasure of visiting the DJEVA factory and discovering a large manufacturer of synthetic sapphires and rubies located near Montreux in Switzerland. The factory runs 24 hours a day and employs nearly 80 people.
The history of Djeva goes back to the beginning of the 20th century. In 1902, the lapidary Hrand Djevahirdjian was intrigued by the publication of the work of the physicist Auguste Verneuil on the synthesis of ruby.
He tried out the process, perfected it, replacing the lighting gas with hydrogen and started producing synthetic corundum.
What is synthetic corundum?
Synthetic corundum is a corundum manufactured in a laboratory with the same components as the natural gem. Known in costume jewellery, its industrial applications are innumerable and of great value.
Corundum is the scientific name for sapphires and rubies, which are therefore in the same gem family. Natural corundum found in nature and synthetic corundum produced in the laboratory have exactly the same physical and chemical properties and it takes knowledge, a good eye and often good instruments to distinguish between them.
It was the French chemist Auguste Verneuil, who perfected its synthesis in 1891. The chemical formula of this aluminium oxide is relatively simple: Al2 O3, but this does not mean that everyone can make it in their garage!
Corundum (natural or synthetic) is colourless but it is quite rare and it exists in almost all the colours of the almost all the colours of the rainbow. It is enough that some atoms of aluminium atoms of aluminium are replaced by iron, cobalt, titanium, manganese or chromium or a combination chromium or a combination of these elements, the corundum becomes coloured and turns becomes blue, pink, yellow or more rarely "ruby red" when, by chance, the crystal has incorporated chromium, a rare element on earth. The best known known are the blue sapphire (a quasi redundancy, since sapphire comes from the Greek sappheiros, blue) and the ruby (ruby meaning "red" in Latin).
Why the Alps?
Originally located near Lyon, then in the Pyrenees then in the Pyrenees, the company finally settled in Monthey in Switzerland for both technical and economic reasons.
The manufacture of synthetic sapphires sapphires requires an enormous amount of energy, an industry that is highly industry, so it is important that it is located in an area where electricity is where electricity is cheap. It also requires chlorine and It also requires chlorine and must be located close to chemical sites. The gases (oxygen and hydrogen) to heat the ingredients that will crystallize and grow in refractory in refractory moulds are produced by electrolysis of water.
The 2 gases are stored in an impressive 20,000 m³ of pressurized tanks and provide 12 hours of autonomy autonomy of 12 hours, allowing production to continue at night when electricity electricity is cheaper.
DJEVA's annual electricity consumption of electricity is equivalent to the consumption of a town of 8000 inhabitants!
In the buildings, there are 6 huge corundum production halls, where 2,000 torch furnaces operate day and night. and night.
How does the crystal grow?
The starting point is a synthetic corundum seed oriented according to its future use. The stone grows like a stalagmite. A technician adjusts the hydrogen/oxygen supply of the 45 torches, then the alumina powder is fed in with a small hammer that is individually individually.
The growth rate of the "crystalline bottle The speed of growth of the "crystalline bottle" is 1 cm/h, faster for the blue color. We see a stone worker preparing his firing, he wears glasses that protect his eyes from the He wears glasses that protect his eyes from the very blinding flame. He is very concentrated because the first hour is crucial.
The manufacture of crystals according to the the Verneuil process is done under low pressure. The crystal is shaped like an inverted bottle shape. At the end of the growth, it is necessary to eliminate tensions which weaken the crystal, the bottles are therefore annealed at 1800° without air, for 24/48 hours in order to be stabilized.
As indicated by its chemical formula alumina is the basic mineral of corundum, DJEVA produces its own their own alumina.
The hydrocarbon torches are manufactured as well as the "muffles", the furnaces that protect the growing which are used to protect the growing crystal. The muffles are made of refractory earth and grog.
Refractory moulds must withstand temperatures above 2000°. The crucible acts as a furnace that protects the stones. Each crucible can be used between 10 and 50 times depending on its diameter or the dye used for the stone because there are components that attack more than others.
At the end of the chain, before shipment the quality control department where the cleavage plane of each corundum is determined of each corundum is determined by means of cross polarizers. The cleavage plane The cleavage plane and the direction of the optical axis are marked on each piece. We bubbles, possible unmelted material etc. are then tracked down. The stones can then be measured, calibrated and stored.
What is the purpose of the production?
DJEVA sells raw stones and laser laser drilled stones. Colorless crystals for watch glasses or optical lenses or optical lenses, coloured ones for most other applications.
For example, the rubies are drilled and become washers for the watchmaking or precision industries. precision industries. The hole measures between 34 and 39 microns in diameter, the equivalent of half the diameter of a human hair. So we don't look for it without a microscope.
These pierced rubies (an extremely solid and friction-resistant stone) are used as the basis for pivots in precision engineering. Other rubies are cut to decorate watch winders.
We pass quickly the workshop the watch glass manufacturing workshop, starting from the crystalline bottle, we the cleavage plane is placed and the sawing is carried out by spraying with water.
It takes about four hours to saw, then the "glass" is passed through an abrasive machine (diamond abrasive) to make the faces perfectly flat.
The glass is then polished by applying increasingly fine diamond powder...
DJEVA also manufactures star-shaped rubies and synthetic sapphires, a delicate process to direct the titanium needles to form a 6-pointed star.
This is a long treatment that requires several weeks at various temperatures. Many of these sapphires or coloured rubies, pure or starred, are intended for costume jewellery and copies of precious jewellery. DJEVA remains discreet about possible frauds. Fortunately the French consumer is quite protected, but not the tourist on an exotic market who will not think for a moment that the beautiful stone, so pure, could come from a factory so close to his home.
Other technical products from the factory include injector nozzles, balls and endoscope tips. It is exciting to discover that synthetic sapphires are used in mobile phones, scientific optical lenses and Airbus landing gear... Enjoy the flight!