There's a lot of science and research involved in growing diamonds, we’ll do our best to explain what we’ve learned. So without getting into the manufacturers science and procedures, (because that is all patented and proprietary information), here’s what we know about the science behind creating lab-grown diamonds.
There are two types of processes used when growing a lab-created diamond. HPHT and CVD, both processes start with a carbon seed and use different methods to grow a diamond from that seed.
CVD is short for Chemical Vapor Deposition. This means that a material is deposited from a gas onto a substrate (surface or material on or from which an organism lives, or grows) and then chemical reactions are involved which causes the Diamond to begin to grow. Growth is a very long process, on larger areas (less than 100cm2) diamond is usually deposited at growth rates between 0.1 and 10 micron per hour. To put that into prospective the average piece of hair on your head is around 45 microns. So its a very slow process, and requires precisely controlled environments and gas levels in order to form into a gem quality diamond.
HPHT is short for High Pressure High Temperature. This process has a much more used history in the jewelry industry. Basically some larger companies started using this process in the 1940-1950's to make diamonds, but was never used or able to make gem quality diamonds. HPHT uses a catalyst (carbon seed- pure carbon source) and under the same environments (High Pressure High Temperature) that natural diamonds form, they grown a diamond. This process requires large machines that can maintain the Pressure and Temperature needed for the diamonds growth.