It is known that natural diamonds are formed at pressures of 5-6 GPa and temperatures in the range of 900-1400°C.  Until recently diamond crystallization under such conditions could be realized only in metallic systems, which are unlikely to correspond to natural diamond formation environment.   Dr. Palyanov’s team has found that the diamonds can be crystallized in alkaline carbonate-fluid melts at temperatures and pressures similar to those of natural diamond formations. The system we use is known as the “Split Sphere”.  The process utilizes Na2CO3, K2CO3, graphite and oxalic acid dehydrates, generating C-O-H fluid. Further, we add minute diamond particles as seeds to the charge. Crystallization process is done in sealed platinum ampoules. Considering the abundance of carbonates in diamond-breaking rocks of magmatic and metamorphic origin, as well as the aqueous carbonaceous composition of mantle fluid, Dr. Palyanov suggested that alkaline carbonate-fluid melts represent the most likely medium for natural diamond formation.

At present the main areas of activity are improving quality and color characteristics of synthetic diamonds, growth and modification of diamonds for high-technology application and modeling natural diamond formation processes. We mainly produce Fancy Yellow shades, including Vivid, Orange and Cognac. White and blue were recently grown, but we still have some work to do to improve size and price.

 

   The synthetic diamond is a definite threat to DeBeers cartel. The comparison can be made with other Created Gems, but there is no gem that is being monopolized to the extend that the diamond is. The price of natural stones is artificially inflated, not like some other gems that are freely traded by miners and brokers. The scarcity of man-made diamonds still commends high price, however, in the case of our production of Fancy Vivid Yellow shade, natural stones’ wholesale price is in the range of $ 50,000/ct for 1-2 carat size stones in VS or better clarity. The main difference between a “Created” and a natural stone is that men make one and men find the other one.

 

    

 

 

 

 

 

 

 

 

 

 

 

 

 

The Sphere apparatus, used by to produce our Gems      Walter Barshai with Dr. Yuri Nikolayevich Palyanov        Fancy Yellow colors of our new product

 

Properties of Natural and Created Diamonds

Hardness = 10
Refractive index = 2.42 (off the scale for most gem refractometers).
Dispersion = 0.044
Internal inclusions such as feathers, clouds, veils, pinpoints, etc.
Thermal conductivity (standard test used to differentiate diamonds from other colorless, high refractive gemstones, such as cubic zirconia).
Natural Diamonds: Positive Identification Features
Included crystals (also known as “carbon spots”).
Indented trigons (natural triangular shaped external features on diamond crystals). Note: raised trigons may be associated with either natural or synthetics.
Blue fluorescence.
Occurs in all colors, including colorless. Note: expect this to change as soon as the synthetic diamond technology matures!
Mottled zoning that does not repeat every 90°.
Usually octahedral crystal habit (uncut).
Synthetic Diamonds: Positive Identification Features
Metallic inclusions.
Hourglass-shaped and columnar internal color zoning. Repeats every 90° of rotation.
Radiating octagonal surface pattern on table (raised external feature that remains after polishing).
Geometric patterns (e.g. crosses) seen in fluorescence due to zoning of light emitting ions. Fluorescent pattern is usually green or yellowish green, sometimes orange, but never blue.
Phosphorescence (up to 30 seconds) in near colorless stones.
Cube octahedral crystals (uncut).

 

HISTORY OF CREATED DIAMONDS

 

 

The First Real Success: Tracy Hall at General Electric

 

The first confirmed success in the synthesis of diamond came in 1955, when Tracy Hall of the American company General Electric produced synthetic diamond using an apparatus that remains the mainstay of synthetic diamond experimentation today.

 

The conversion of graphite to diamond requires very high temperatures and pressures, and is extremely difficult to achieve.  The most important leap forward was made with the adoption of catalyst, something that had been absent in previous experiments.  An iron catalyst was used, as this material (at high temperatures and pressures) was able to act as a solvent in which the graphite starting material could be dissolved and later re-crystallized as diamond.

           

The apparatus used to produce synthetic diamond is known as the 'belt' due to the structure of the central zone (containing the reaction cell) which consists of a ring made of tungsten carbide and specially toughened pre-shrunk steel.  Two pistons are driven by a large hydraulic press, of strengthened steel then compress the central area from above and below.  At high temperatures and pressures standard structural materials such as steel rapidly lose their strength and a substitute had to be found.  General Electric solved this problem by internally heating the pistons and belt assembly, and more importantly building the central chamber and its gaskets out of the naturally occurring rock pyrophyllite.

 

Pyrophyllite was chosen because it has the ability to soften and transmit pressure, but remain not melted at the high temperatures and pressures produced by the process.  A complex assembly of pyrophyllite and metal gaskets fills the space between the pistons and cylindrical belt centering on a carbon tube through which a current is passed to generate the necessary heat.  The pyrophyllite components at the center of the belt provide thermal insulation for the sample chamber, which contains a catalyst of nickel and iron together with the 'feed' material.

 

During the process the pressures generated by the presses reduce the volume of the pyrophyllite gasket (which seals any potential gaps).  The pressures generated are around 50,000 atmospheres, at temperatures of around 1400°C (for only about two minutes) followed by a gradual cooling.  Most of the diamond-grit used for abrasive and industrial purposes is now generated synthetically.

 

 

 

 

The 'Split-Sphere' or BARS

 

The only real viable economic process for the growth of large (1ct or more) diamond crystals of potential gem quality is still the 'belt' type system mounted within a hydraulic press.  This technique remains basically as outlined above.  Scientists at De Beers, General Electric and Sumitomo Electric all use variants of this apparatus which produces temperatures of between 1400 and 1600°C, and pressures of 50,000 to 60,000 atmospheres (50-60 kbar).  Diamond is the stable form of carbon within this pressure/temperature envelope, and growth occurs in a metal flux.  Growth of a 1ct diamond takes five days.

However, in our process, a different type of reaction vessel is used.  This is known as the split-sphere, or more usually by the Russian name BARS.  Rather than a belt-type arrangement, two sets of anvils completely surround a central reaction chamber.  The first (outer) set forms an octahedral cavity in, which nestle a further (inner) set of six additional anvils positioned around a central cube-shaped cell.  The high pressure cell in which the diamonds grow occupies the center of the apparatus.  Temperature and pressure ranges are very similar to those produced with the belt method (1350 to 1600°C and 55 to 60 kbars).  A transition metal flux (this may be iron, nickel, manganese or an alloy of these metals) is used, but the interior of the reaction cell is smaller than that of the belt apparatus, so less space is available for diamond growth (Shigley et al 1993). In recent years the chamber was adjusted to allow growth of larger crystals, up to 6 carats.

 

 

 

 

 

 

 

Tairus Created Gems

 

 

 

                                Created Diamonds we grow              by Walter Barshai

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Above: The high pressure cell (C) positioned within two sets of anvils.

                   (An enlargement of the high pressure cell (C) )