Synthetic Diamonds & Man-Made Diamond Simulants
The First Synthetic Diamonds
Article Copyright © 2009 AllAboutGemstones.com
The process of creating man-made diamonds (aka cultured diamonds, lab diamonds) was first conceived by French chemist Henri Moissan in 1892. With Moissan's process, tiny fragments of synthetic diamond were created by heating charcoal, or carbon to an extremely high temperature (4000¼ C) in a cast iron crucible.
Using an electric furnace constructed with blocks of lime, the intense heat would render the crucible and its carbon contents into a molten liquid mass. Once the desired temperature had been achieved, the crucible and its contents were rapidly cooled by immersing them into cold water. This abrupt cooling caused the rapid shrinkage of the molten iron crucible, which created enough pressure to crystallize the molten carbon into tiny diamond fragments.
The first practical commercial application of Moissan's process was developed in 1954, by H.Tracy Hall for the General Electric Company. The process, known as the HTHP (high-temperature, high-pressure) "belt press" process was used for synthesizing industrial-grade diamonds, and has been steadily improved upon throughout the last 50 years.
These man-made synthetic diamonds are a laboratory-grown simulation of the natural gemstone, yet they have the identical carbon-based chemical properties of natural diamond. Although synthetic diamonds were originally conceived as a substitute for natural industrial-grade diamonds, they are increasingly used in fine jewelry as their quality increases.
Synthetic Diamond under Fluorescent - © AGS Labs
Synthetic Yellow Chatham Diamond - © AGS Labs
Today, there are two main processes for creating lab diamonds: the High-Temperature High-Pressure or "HTHP" method, and the Chemical Vapor Deposition or "CVD" method.
High-Temperature High-Pressure (HTHP)
The "High-Temperature High-Pressure" (HTHP) technique, also known as "GE POL," uses a four-anvil 'tetrahedral press,' or six-anvil 'cubic press' to create the necessary pressure. A diamond seed is placed into a growth camber, and a combination of heat and pressure are applied to the seed in a process that attempts to replicate the natural conditions for diamond-formation.
Unlike their natural diamond counterparts, the HTHP diamond's growth process can take 7 to 10 days to complete. Synthetic diamonds can also be treated with the HTHP process to alter the optical properties of the stones, making them difficult to differentiate from natural diamonds.
Chemical Vapor Deposition (CVD)
The "Chemical Vapor Deposition" (CVD) method was developed during the 1980s, and uses a lower-pressure growth environment than the earlier HTHP method. With CVD, a seed or substrate material is placed into the growth camber, and a combination of heat and pressure are applied while a vaporized carbon-plasma that is combined with hydrogen is applied, or "deposited" onto the substrate in successive layers. The vaporized carbon gases are energized using microwave energy, which attracts the gas to the substrate. Using Chemical Vapor Deposition, the diamond's entire growth process takes several days to complete.
A cultured synthetic diamond will have the identical cleavage, hardness, light dispersion, refractive index, specific gravity, and surface luster as its natural diamond counterpart. Like natural diamond, synthetic diamonds may contain small inclusions, ranging in clarity from IF to SI or I.
Synthetic Diamond Color & Optics
Unlike natural diamond which can occur in completely colorless form, most synthetic diamonds will have a slightly yellowish hue due to nitrogen impurities that are dispersed through out the crystal lattice structure during the growth phase. These impurities absorb the blue end of the light spectrum, making the stone appear yellowish.
Synthetic diamonds can be detected using infrared, ultraviolet, or X-ray spectroscopy, or by measuring UV fluorescence with a DiamondView tester.
Diamond "simulants," also known as "simulated diamonds" or "fake diamonds" are man-made gemstones that look like, or "simulate" the appearance of natural diamonds, but are not a carbon-based compound having a natural diamond's crystalline structure. Common diamond simulants include:
- Cubic Zirconia (CZ) (1976-) Czarite, Diamonite, Diamond Essence, Phianite
- Gadolinium Gallium Garnet (GGG) (1972-1975)
- Strontium Titanate (ST) (1955 - 1970) Diagem, Fabulite
- Synthetic Rutile (1946-1955) Diamothyst, Java Gem, Rainbow Diamond, Rutania, Titangem
- Synthetic Sapphire (1900-1947) Diamondette, Diamondite, Jourado Diamond, Thrilliant
- Synthetic Spinel (1920-1947) Corundolite, Lustergem, Magalux, Radient
- Yttrium Aluminum Garnet (YAG) (1970-1975) Diamone, Diamonaire, Diamonte, Geminaire
In the early 1900's, colorless synthetic sapphire (aka Diamondite) was a popular diamond simulant. produced using the Verneuil (flame-fusion) Process. In the late 1940's Diamondite gave way to Synthetic Rutile which was popular until the advent of YAG in the early 1970's. With the advent of Cubic Zirconia in the mid 1970's, and Moissanite in 1998, most of these lesser simulants fell by the wayside.
Synthetic Diamond Manufacturers
Apollo Diamond, inc. in Boston, Massachusetts grows colorless (D to M) diamonds, and some fancy colored diamonds, using a proprietary variation of the Chemical Vapor Deposition (CVD) technique. Apollo Diamonds are cut and polished in sizes ranging from .25 carats to 1 carat, with clarity grades from IF to SI. Apollo Diamond's cut stones are available in round brilliant, emerald, princess, and rose cuts, and each cut stone is laser inscribed with the Apollo company logo and serial number.
Chatham Created Diamonds
Chatham Gems is a San Francisco based company that grows only fancy-colored diamonds in colors ranging from champagne and canary yellow to pink and midnight blue. Chatham's pricing ranges from $6,500 to $9,500 per carat (2004 est.), and each stone is laser inscribed with the company name and serial number.
Gemesis Cultured Diamonds
Gemesis is located in Sarasota, Florida, and like Chatham, Gemesis only grows fancy-colored diamonds. To insure easy identification as a man-made product, each Gemesis cut stone over .25 carats is laser inscribed with the company name and serial number.
Tairus Created Gems
Tairus Created Gems is a Russian company that grows fancy-colored diamonds in their proprietary "Split Sphere" system, which they claim is the closest thing to mother nature. The Split Sphere system crystalizes the carbon seed in an alkaline, carbonate fluid solution that is similar to diamond-bearing metamorphic rock. Tairus produces rough sizes from .30 carats to 3 carats, and stones are cut to order. Tairus Created Gems are sold exclusively through Tairus Thailand Co., Ltd. of Bangkok Thailand.
Bibliography for Synthetic Diamonds
1. Robert M. Hazen, The Diamond Makers . Cambridge University Press
2. Amanda Barnard, The Diamond Formula: Diamond synthesis . Butterworth-Heinemann
3. Nature Article, Growing Diamond Crystals . www.nature.com
4. Wired magazine, The New Diamond Age . www.wired.com
5. Newton, Physical Properties of Diamonds . www.newton.ex.ac.uk
6. Chemical & Engineering News, Man Made Diamonds . www.pubs.acs.org
7. Moissanite Detection, Moissanite Testers . www.kassoy.com
8. Antoinette L . Matlins, Antonio C. Bonanno, Gem Identification Made Easy . Gemstone Press
9. Judith Crowe, The Jeweler's Directory of Gemstones . DK Publishing.
10. Walter Schumann, Gemstones of the World . NAG Press; 2Rev Ed edition
11. Renee Newman, Gemstone Buying Guide . International Jewelry Publications; 2nd edition
12. Paul R. Shaffer, Herbert S. Zim, Raymond Perlman, Rocks, Gems and Minerals . Martin's Press