As Grown -
Lab-Grown Diamonds that are grown as is, without any post-growth treatment to enhance their color or appearance.
The High Pressure Heat Treatment (HPHT) method is the oldest form of growing diamonds in a laboratory setting. Using HPHT, a diamond seed is exposed to temperatures of over 2,000 degrees fahrenheit and pressure of about 1.5 million PSI (pounds per square inch). Carbon melts and adheres to the seed, forming a complete rough diamond as it cools. HPHT may also be used, as a post-growth treatment of CVD grown diamonds, to enhance their color or appearance.
Chemical Vapor Deposition (CVD) was first explored for the growing of diamonds in the 1980s. Recently CVD been used to grow high-quality diamond material for gem and other applications. In the CVD method a seed is placed in a chamber, where carbon-containing gases are activated, using a plasma discharge, allowing the carbon to settle on a seed and grow a complete rough diamond. CVD is a much less costly process than HPHT because it works at moderate temperatures and low pressure, which requires smaller and less expensive equipment.
Post Growth Treatment -
When a diamond is grown in laboratory it does not always achieve the color level the grower desired for commercials sales. When this occurs post-growth treatment of the diamond can be used to improve the color and appearance of the diamond. HPHT is most commonly used, as a post-growth treatment of CVD grown diamonds, to enhance their color or appearance. This treatment has also been used with mined diamonds.
A small piece of a single crystal diamond (either mined or lab-grown) that can be used to start the growth of a new diamond in a lab, with either CVD or HPHT processes.
Sometimes called a reactor, a chamber is a vacuum sealed container within which a diamond is grown using the CVD method.