Synthetic* diamonds, what is in a name? Presentation by Dr. Katrien De Corte, Chief Officer Education & Industry The International Diamond Council defines synthetic diamonds as a “Manmade product that has the same chemical composition, crystal structure, optical and physical properties as a diamond.” Both natural and synthetic diamonds are made of carbon, have the same density and refractive index and share the same extraordinary hardness. The main difference is its point of origin: natural diamonds grow deep within the Earth and are mostly more than 1 billion years old, while synthetic diamonds are produced in a lab in a couple of days/weeks. Laboratory grown diamonds can be produced by two methods. One is HPHT, under high pressure and high temperature; the other is CVD, chemical vapour deposition. HPHT (High Pressure / High Temperature) The purpose of this technique is to synthetically produce a diamond by replicating the formation conditions of diamonds deep in the earth. By applying high pressure (HP) and high temperature (HT) to a carbon source, one 'forges' a synthetic diamond. Swedish researchers at ASEA were the first to produce a diamond by using this method in 1953. They were soon followed by General Electric and De Beers. Since the seventies, gem quality diamonds have been produced by HPHT synthesis. CVD (Chemical Vapour Deposition) Chemical Vapour Deposition (CVD) is the process through which a diamond is produced from a (carbonaceous) gas. The principle was already known in the nineteenthirties, but it took until the beginning of this century before anyone succeeded in growing larger single diamond crystals instead of polycrystalline material. The gas (methane is usually used) is heated to a very high temperature. Atomic compounds are then broken down. Then, carbon atoms can be 'precipitated' onto a surface. Under the right conditions, a single crystal is formed that becomes thicker layer by layer. CVD diamonds are considering the complexity of the process usually light brown, making them relatively unattractive to the average diamond trader.