It was several months before Valentine’s Day that Graff Diamonds announced the availability of the largest D Flawless heart shape diamond in the world. Named after the Roman goddess of Love, the Graff Venus is a type IIa 118.78ct diamond. I’m sure there are not many people who can afford this diamond, and with a large amount of money at stake, I’m sure there will be testing by any buyer who wants to own the magnificent stone.
But how does one test a diamond to find out if it is natural or synthetic?
ISO (the International Organization for Standardization) states that a “diamond is a mineral; it forms and grows under natural geological processes…. A synthetic diamond, also known as a laboratory-grown or laboratory-created diamond, is an artificial product that has essentially the same chemical composition, crystal structure and physical (including optical) properties as a diamond.”
According to a Bloomberg article,
“Unlike imitation diamonds such as cubic zirconia, stones that are ‘grown’ (the nascent industry’s preferred term) in labs have the same physical characteristics and chemical makeup as the real thing. They’re made from a carbon seed placed in a microwave chamber with methane or another carbon-containing gas and superheated into a glowing plasma ball. That creates particles that crystallize into diamonds, a process that can take 10 weeks.”
High-pressure high-temperature (HPHT) diamonds and laboratory-grown diamonds are part of the synthetic family of diamonds.
The HPHT method, as explained by the GIA, “essentially mimics the natural process – carbon is crystallized as diamond through intense heat and pressure deep within the Earth. The HPHT process is very costly, given the energy and equipment required, and produces diamonds with mainly yellowish or brownish yellow colors…. The [Chemical Vapor Deposition (CVD)] process involves introducing a gas, such as methane, into a vacuum chamber, then activating and breaking down the molecules of the gas with microwaves. This causes the carbon atoms to accumulate on a substrate (a small platform containing a flat diamond seed crystal, usually an HPHT synthetic), similar to the way snowflakes accumulate in a snowfall.”
HPHT diamonds and laboratory-grown diamonds CVD techniques have improved to the point that these products are nearly indistinguishable from natural diamonds. In fact, synthetic diamond creation technology has improved so much that these products are nearly indistinguishable from natural diamonds without the help of Fourier Transform Infrared spectroscopy.
FT-IR spectroscopy produces an infrared absorption spectrum that represents a ﬁngerprint of the sample, with absorption peaks which correspond to the frequencies of vibrations between the bonds of the atoms making up the material. Infrared spectroscopy can often detect the presence or absence of trace compounds that may be due to either the natural or synthetic process that created a specific gemstone. FT-IR is one of the ways to detect Type IIa diamonds, which have almost no nitrogen impurity peaks in the infrared spectrum.
Diamonds are unique among gemstones because they are composed of a single element (carbon), while virtually all other gems contain multiple elements including significant amounts of oxides. The infrared spectrum of diamond is equally unique and can be used to easily confirm that a stone is actually a diamond.
It’s been reported from many sources that the Venus was cut from a raw stone that weighed 357 carats and was found at the Letseng mine in Lesotho, so we can assume that it is a natural diamond. But if I was the buyer, I would still get it tested with a Fourier Transform Infrared spectrometer. I wouldn’t want him or her to end up with a broken heart.
If you are interested learning more about diamond analysis by FT-IR spectroscopy, read the Analysis of Diamonds by FT-IR Spectroscopy application note. If you want to learn more about FT-IR spectroscopy, we have many free resources on our website. Just visit our online FTIR Spectroscopy Academy for videos, white papers, application notes, and infographics about various FTIR applications, FAQs, basic education, and sample handling techniques.