The first scientific breakthrough in man-made diamonds came in 1954 when General Electric developed a process that successfully replicated the conditions for natural diamond formation.
This process is called High Pressure High Temperature (HPHT) and involves the use of seed crystals which are grown in superheated anvils.
High Pressure High Temperature (HPHT)
HPHT is a process that is energy intensive and has a relatively low production rate (seed crystal typically grows at a few microns per hour). During the process, the parameters need to be tightly controlled or it may cause the diamond’s growth to fail or the rough to become heavily included.
Chemical Vapor Deposition (CVD)
Chemical vapor deposition (CVD) is another method of making synthetic diamonds on a commercial scale. In this process, diamonds are grown in a hydrocarbon gas mixture in a controlled environment.
The hydrocarbon gas (usually methane, CH4) is heated to elevated temperatures and broken down into its atomic state. Next, the carbon atoms are then precipitated onto seed crystals and the rough diamond is grown layer by layer.
Compared to HPHT, the CVD method is relatively easy to setup and it is possible to grow synthetic diamonds over large surface areas at the same time. Besides lower temperatures, the CVD method doesn’t require high pressures and achieves higher growth rates than HPHT.