There are two main processes used to create lab-grown diamonds:
1. HPHT - High Pressure, High Temperature
With this method, laboratory-grown diamonds are produced in laboratories that mimic the high pressure, high temperature conditions of natural diamond formation in the earth. HPHT diamond growth occurs at pressures of 5–6 GPa (roughly equivalent to the pressure exerted by a commercial jet airplane if balanced on the tip of a person’s finger) and at temperatures of 1300–1600°C.
Lower-quality diamonds, whether natural or laboratory-grown, can also be put through the HPHT process to improve color and clarity. In addition to making diamonds more colorless, this process can also be used to change the color of diamonds into pink, blue or yellow. The diamond would then be called a “treated” diamond.
2. CVD - Chemical Vapor Deposition
This newer technique enables scientists to grow laboratory-grown diamonds using moderate temperatures (700°C to 1300°C) and lower pressures. Carbon-containing gas is pumped into a vacuum chamber, depositing onto a diamond seed and crystallizing as laboratory-grown diamond. The eventual size of the diamond depends on the time allowed for growth.