By replicating the mining conditions inside a lab, we are able to grow diamonds that are identical to mined diamonds, but without the social and environmental impacts.
There are two methods to create cultivated diamonds:
1. High-Pressure High-Temperature
HPHT stands for high pressure, high temperature and is one of the primary methods used to grow diamonds in a lab. This diamond growth process subjects carbon to extreme temperatures and pressures and is meant to replicate the extreme heat and pressure conditions deep within the earth where natural diamonds form.
THE HPHT DIAMOND GROWTH PROCESS
Diamond seed is placed in a specifically designed press.The growth chamber is heated to 1300-1600 °C with pressures above 870,000 pounds per square inch.The molten metal dissolves the high purity carbon source.Carbon atoms precipitate on a small diamond seed crystal, and a synthetic diamond begins to grow.The lab-grown crystal is then cut and polished by a diamond cutter.
2. Chemical Vapor Deposition (CVD)
CVD stands for chemical vapor deposition and is another method used for making diamonds in a lab. Diamonds grow from a hydrocarbon gas mixture subjected to moderate pressures and temperatures in a vacuum chamber.
THE CVD DIAMOND GROWTH PROCESS
Diamond seed crystals are placed in a diamond growth chamber.The chamber is filled with carbon-containing gas. The chamber is heated to about 900-1200°C. A microwave beam causes carbon to precipitate out of a plasma cloud and deposit onto a seed crystal.Diamonds are removed every few days to have the top surface polished to remove any non-diamond carbon before being put back in to grow. Each batch of diamonds may require several stop/start cycles, and the entire growth process can take three or four weeks. After the synthetic diamond crystals are removed, they are ready to be cut and polished into the final product.
Source: HPHT and CVD Diamond Growth Processes: Making Lab-Grown Diamonds, Dr. James E. Shigley, GIA, 2016.