Christopher S. Nelson 
Of all the great debates in the gemstone and jewelry industry, the most “hot” topic continues to be natural diamonds versus synthetic diamonds. Variable and sometimes “opposing” information is published as synthetic and natural diamond technologies continue to develop.
The initial confusion: what’s in a name? It appears that the industry prefers the term “lab grown” or “lab created” diamonds to “synthetic” diamonds. Technically, “synthetic” is the most accurate term, although “lab grown” and “lab created”, not short of “lab”, are also accepted by the CIBJO industry standard.
These names all represent lab-made diamonds that have the same chemical composition and physical properties as natural diamonds.
On the other hand, there are synthetic stones that are designed to look like diamonds but are imitations because they are not the same chemically and / or physically, like cubic zirconia and moissanite.
The first recorded synthetic diamonds were largely experimental, designed for use in advanced technological environments. In 1970, General Electric announced that it had produced gem-quality colorless, blue and yellow synthetic diamonds suitable for the jewelry industry.
As technology and understanding of diamond synthesis improved, new variations of these gemstones were produced, including synthetic blue diamonds, supposedly “grown from human remains”!
The first method of diamond synthesis responsible for commercially available synthetic diamonds, still available today, was high pressure, high temperature (HPHT) synthesis. This aims to recreate the natural growth of the diamond by subjecting the carbon to extreme pressure and temperature, as the name suggests.
The device “grows” diamonds at pressures of around 53,000 atmospheres (1 atmosphere is the average pressure we feel on Earth) and temperatures of around 1,300 to 1,600 ° C.
Generating this level of energy is expensive and requires more equipment than the more recently introduced synthetic method of chemical vapor deposition (CVD). This method is very different from the geological processes that create natural diamonds.
CVD diamonds are grown in a vacuum chamber from a carbon-containing gas, such as methane. Exposure of the gas to microwaves ionizes the carbon atoms, which deposit and grow on a seed diamond crystal inside the chamber. Over time, the change in gas used and the purity of the diamond seed plate resulted in higher quality CVD synthetics.
Synthetic CVD diamonds are generally Type IIa – a “purer” type of diamond with negligible nitrogen impurities, found in only 2% of natural diamonds.
Although HPHT synthetic diamonds were predominantly Type Ib in previous production, the introduction of a new step in the growth process means that Type IIa is now commonly cultivated for the jewelry industry.
Nowadays, portable test equipment designed to identify and separate colorless natural diamonds from synthetic diamonds, such as the Presidium Synthetic Diamond Screener II, measure the diamond’s response to ultraviolet light to suggest if it may be type IIa.
In the screening process, all colorless diamonds that show signs of being Type IIa should be sent to a gemological lab for further testing to confirm natural or synthetic growth.
The best known characteristics of synthetic diamonds include metallic inclusions in HPHTs (which can attract them by magnets), stronger fluorescence in shortwave ultraviolet light than longwave (the opposite of natural diamonds), phosphorescence and deformation. patterns caused by the growth process and their different morphology (crystal shape), which varies between HPHT, CVD and natural diamonds.
Accurate and reliable identification can be simple by identifying growth patterns, fluorescence and phosphorescence, or it can be difficult, requiring more advanced gemological tests, such as spectroscopic analysis.
As technology continues to improve, disclosure and education become more and more important. Next month we will provide an overview of the treatments that can be applied to synthetic diamonds in Synthetic Diamonds: Part II.
