How are Laboratory-Grown Diamonds produced?

There are two different types of laboratory-grown diamonds.

High pressure, high temperature (HPHT)
The first is referred to as HPHT, meaning high pressure high temperature. These diamonds are produced by a process that starts with a small capsule capable of withstanding extremely high pressures with pressure being applied from both sides (much like under the Earth’s surface). Starting with a seed crystal, an organic pure carbon substance is dropped through a molten metal flux allowing it to attach to the crystal. This then produces a rough cub-octahedron shaped stone.

Image 1: These diamonds were all grown using the HPHT method. The background shows a DiamondView image of a laboratory-grown diamond with a cross-shaped fluorescence pattern, a well-known diagnostic feature of HPHT diamonds. Photo courtesy of the GIA

Image 2: Shown here is a HPHT press, used to create diamonds. It approximates the high pressure, high temperature environment that natural diamonds experience within the earth. Photo courtesy of the GIA and Suncrest Diamonds.

Chemical Vapour Dispositions 
The second is referred to as CVD. This means chemical vapour dispositions. Theses laboratory-grown diamonds are produced on a seed plate slowly growing from a carbon rich gas. An energy source much like a microwave beam is shone through the high temperature plasma-like gas cloud. This breaks down the molecules causing the carbon atoms to precipitate falling onto the seed plate. Crystallization then begins and occurs over several weeks. The rough uncut stones grow to exhibit a flat tubular shaped design with dark edges of graphite.

Image 3: In CVD synthesis, microwaves split apart the hydrocarbon molecules fed into the reactor (left). These fragments migrate down to the colder diamond seed and attach to the growing diamond surface. The synthetic diamond grows in thin layers, and its final thickness depends on the amount of time allowed for growth. This results in flat, tabular crystals (centre and right) with exteriors coated in black graphite. Illustrations: Peter Johnston/GIA

Laboratory-Grown Diamonds versus Natural grown diamonds

The laboratory process of creating a laboratory-grown diamond simulates the Earth’s naturally occurring phenomena. Just like natural diamonds, no two laboratory produced stones are alike. For this reason, the grading of laboratory-grown diamonds follows the same criteria as mined diamonds.

Carat: As with earth mined diamonds, laboratory-grown diamonds also fluctuate in size (carat weight). This is mainly due to the similarity of conditions that the laboratory-grown diamonds are created in.

Colour/Clarity: Colour is variable, as with natural diamonds. Ranging from D-M in colour, Champagne to Brown, Pink, Yellow, Blue etc. In terms of clarity, one could find all sorts of inclusions that gemmologists, jewellers and diamond merchants have been accustomed to finding in natural diamonds for centuries.

Cut: Each and every laboratory-grown diamond is cut into an ideal diamond shape. It is in the cut of a diamond, which is how we establish perfection, polish and symmetry, regardless of natural or laboratory-grown.

Image: Examples of Laboratory-grown Diamond Certification