Before explaining how lab grown diamonds are created it’s important to understand the chemical makeup of a diamond. A diamond is made entirely of carbon and it's the way in which these carbon atoms are structured which makes a diamond so special. In a diamond, the carbon atoms are arranged in a tetrahedral structure, which gives it its extremely strong and hard properties. Other forms of natural carbon include graphite (used in pencils) which does not have the same desirable properties as diamond.
In order to produce a diamond in the laboratory, carbon must be put under the perfect conditions to allow it to crystallise just as it would in nature. There are two techniques we use to grow these diamonds in the laboratory; High Pressure-High Temperature (HTHP) & Chemical Vapor Deposition (CVD):
This technique uses thin diamond plates which are put into a growth cell and then placed into vaccum plasma reactor. Hydrocarbon gases are injected into the reactor where they are heated until carbon bonds break allowing atoms to fall onto the diamond plates. These carbon atoms build up in a tetrahedral structure eventually creating a rough diamond.
Conjunctive to its name, HTHP technology uses high temperature and high pressure conditions to mimic the natural environment in which carbon crystalises into diamond.
This technique starts with a diamond seed, which is placed into a growth cell. Highly refined graphite is then carefully placed on top of the seed and the put into a HPHT chamber. The chamber creates a high pressure, high temperature environment, which causes the graphite to melt into liquid carbon. Once the optimum conditions are met, the growth cell is cooled over a period of several days allowing the carbon atoms to bond in a tetrahedral structure, thus creating a rough diamond.