Synthetics, origin

What are Synthetic Diamonds?

Synthetic diamonds are sometimes referred to as laboratory-created diamonds, laboratory-grown diamonds, or cultured diamonds, and are manufactured diamond crystals produced by man, not nature.

Synthetic diamond can be optically and chemically identical to natural diamond.
Gem-quality synthetic diamonds are predominantly cubic and octahedral in the rough form. Impurities are common, but as the technology has progressed so the rough diamond crystals have improved. A diamond's hardness can vary depending on its impurities and crystalline structure.

Although synthetic diamonds have similar structure and chemical properties to a natural diamond, they can be conclusively identified by differences in atomic structure and trace impurities due to their different growth environment.

Colour zoning, inclusions, fluorescence and other properties of synthetic diamonds provide practical visual indicators using standard gemmological techniques and equipment, but conclusive identification requires advanced equipment and trained technicians in a laboratory.

Synthetic diamonds can sell at a fraction of the cost of natural diamonds, because they are made for less than it costs to mine a natural diamond. For this reason they are a viable alternative to natural diamond or less durable simulants.

DCLA does not certify synthetic diamonds, but laboratories that do opt to certify synthetic diamonds must clearly state on the certificate that the diamond is a laboratory-created, synthetic diamond.

There are currently two known processes for growing synthetic gem-quality diamonds: the High Pressure High Temperature (HPHT) method, and the Chemical Vapour Deposition (CVD) method.
 

HPHT Method for Growing Synthetic Diamonds

The High Pressure High Temperature (HPHT) method to produce synthetic diamonds uses large presses that can weigh several hundred tons and enormous heat to reproduce the conditions that created natural diamonds. Diamond growth occurs when a form of carbon, graphite, is subjected to this high heat and diamond stabilising pressures in the presence of a metal for a certain period of time. The metal acts as a solvent for the graphite, and also acts as a catalyst to enable crystal growth.

To create coloured HPHT synthetic diamonds, the as-grown diamond crystal may be treated with various methods to induce a colour change, just as natural diamonds are colour treated.

CVD Method for Growing Synthetic Diamonds

The second method, using Chemical Vapour Deposition or CVD, is very much like the process of creating frost on a window pane, when water molecules condense from the air and create a layer of frost. Diamond crystals are formed from a carbon-containing gas without the use of pressure.

The CVD method for growing synthetic diamonds was invented in the 1980s, and involves mixing gases (typically methane and hydrogen) in a vacuum chamber. When heat is applied inside the chamber, chemical reactions of the gas mixture deposit synthetic diamond onto a diamond substrate.