High-pressure, high-temperature (HPHT)
In the HPHT process, a small diamond seed is placed in a chamber with a carbon source, such as graphite. The chamber is then heated to extremely high temperatures (up to 2,000 degrees Fahrenheit) and pressures (up to 150,000 pounds per square inch). The carbon source is then converted into diamond, which forms around the diamond seed.
Chemical vapour deposition (CVD)
In the CVD process, a carbon-rich gas is placed in a chamber with a substrate, such as a silicon wafer. The chamber is then heated to high temperatures (up to 1,000 degrees Fahrenheit) and a plasma is created. The carbon atoms in the gas are then deposited onto the substrate, forming a diamond layer.
The growth rate of lab-grown diamonds can vary depending on the method used. HPHT diamonds typically grow more slowly than CVD diamonds. However, HPHT diamonds are generally considered to be of higher quality than CVD diamonds.
Once the diamond has grown to the desired size, it is removed from the chamber and polished. The polished diamond is then graded and certified by a gemological laboratory.
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