The first thing to establish when discussing synthetic diamonds is the nomenclature itself. Many people confuse diamond imitations, like cubic zirconia (CZ) and moissanite with synthetic diamonds.
The difference being that cubic zirconia and moissanite are lab-created stones that are not made from carbon, whereas synthetic diamonds are made of pure carbon, just like real diamonds. For this reason, the Federal Trade Commission has adopted the terms “lab-created” and “lab-grown” to refer to synthetic diamond, as it more clearly describes the origin of the stone to the consumer. In the lab, there are two different ways to grow a diamond. The first, Chemical Vapor Deposition, or CVD, is a process that draws carbon atoms out of gasses at low pressure. The second, High Pressure High Temperature, or HPHT, mimics the process of natural diamond formation. Here are the two different ways that lab-created diamonds are formed.
Carbon Vapor Deposition
CVD is an ingenious process patented in 1954 that eliminates the need to recreate the intense environment of the Earth’s mantle layer. In this process a diamond seed is placed in a low-pressure, vacuum chamber with a mixture of hydrocarbon gasses, often methane and hydrogen, and heated to a temperature between 1600-1200 degrees Fahrenheit. At these high temperatures, the carbon atoms separate from their molecular compounds and attach themselves to the diamond seed. Layer by layer, the diamond’s crystal lattice structure is formed, resulting in a gem-quality stone. These stones can grow up to 5 millimeters thick vertically, although lateral growth is still limited.
High Pressure High Temperature
General Electric first accomplished the HPHT process in 1956, marking an incredible feat in the replication of one of the planet’s most powerful natural processes. There are 3 main mechanical designs to the HPHT growth unit, but at the heart of each one is a growth cell, which contains all the necessary materials for diamond growth. In this core there is a diamond seed, a catalyst of mixed metals, and of course, carbon. The machine heats this growth cell to about 2400 degrees Fahrenheit and applies more than 50,000 atmospheres of pressure – standard pressure at sea level is one atmosphere, just to give a little perspective. As the temperature and pressure increase, the catalyst of mixed metals becomes a molten metal solution. Eventually, as ideal conditions are met, the carbon dissolves into this solution. Next, the machine spends several days cooling as the carbon atoms slowly attach themselves to the crystal lattice structure of the diamond seed. Once the machine has completely finished its heating and cooling cycle, the growth cell is removed and the diamond is ready to be cut.
Both processes have their pros and cons, and thus they are used for different purposes. One way that they are similar is that neither process can produce diamonds much larger than one carat in weight. The HTHP process can be employed to produce higher volumes of diamonds more quickly, but with less control than CVD, thus the clarity of HTHP diamonds is often very poor in comparison. In both cases, experts believe that these stones will have a greater impact on technology than on the jewelry industry, as diamond microchip processors can handle processing speeds that would melt their silicon counterparts – to name just one of their many applications. But for those who are interested in purchasing gem-stone quality synthetics,