How It's Made: Lab Grown Diamonds
How are Lab grown Diamonds Created?
There are two ways to create and grow a lab grown diamond. One method is called HPHT (High Pressure High Temperature) and CVD (Chemical Vapor Deposition). Both processes create the same end result, a man-made lab grown diamond.
The High-Pressure High-Temperature (HPHT) Method
HPHT was the first process that scientists attempted to form a lab grown diamond. This HPHT method tries to duplicate how a diamond is formed in the earth by recreating the natural conditions of carbon under high pressure and high temperature. Companies tried to duplicate this natural process to grow a diamond for industrial uses in the 1950’s. In 1954, General Electric was the first company to accomplish creating a diamond with this process, and later went on to use the technology in manufacturing industries. Over time and as more labs began improving the process, they were able to grow larger and more controlled quality of lab grown diamonds, resulting in the jewelry-grade lab grown diamonds we sell today.
To start the HPHT growing process, you take an exceedingly small natural diamond “seed” and then place it on a carbon disc called a wafer. Think of the wafer as the “soil” for the diamond seed to grow under the right conditions. The seed is then placed in a large vessel containing pressure plates and resembling a large oven. The temperature increases and constant pressure is applied to the wafer until it starts to crystallize the seed to grow like it would in the earth. The temperatures can get to over 2,200 degrees Fahrenheit and over 1.5 million pounds per square inch of pressure is applied from the pressure plates. This process is finished in weeks, not millions of years like earth-mined diamonds.
This pressure and temperature start the growing process of the seed with the wafer in a similar way to a natural diamond. However, the crystal structure that is formed varies slightly from a natural, earth-mined diamond. An earth-mined diamond forms in a double octahedron shape (think of two pyramids on top of each other). HPHT forms more in a cube or a cuboctahedron structure form.
See the GIA sample diagram below to see the difference in the shapes of crystals.
HPHT created diamonds are more likely to be in the D to H color range and be more in the VVS to SI clarity range. They can have more of a metallic inclusion inside the stone as it is formed under the high pressure.
The CVD Method
The CVD process was created in the mid 1980s. This method tries to mimic how diamonds can be formed in gas clouds. This process starts the same way as the HPHT with a diamond seed and a carbon wafer. This is then placed into a chamber that pumps in carbon rich gasses like methane. The chamber is then heated, but at temperatures less than the HPTP process. They also use electromagnetic rays to help make plasma, which gives off carbon. The carbon then starts to crystallize over the diamond seed and grow into the diamond structure.
A simple way to think about the CVD method is to think about making microwave popcorn. Like placing a bag of popcorn in the microwave, placing a diamond seed in carbon water, pumping methane gas into the chamber, and applying heat causes the diamond to grow. The Orville Redenbacher process of diamond making!
In terms of quality CVD diamonds tend to have a lower color grade than the HPHT, in the G to K color range and tend to not be as high in clarity as the HPHT stones. The reason is that there are more natural impurities in the gasses than the HPHT process. Like HPHT, CVD diamonds form in a different crystal structure, resulting in a square or a cube structure. All three have the same result: a diamond!
Is one method better than the other in making a diamond?
You can’t tell the difference between lab grown and natural diamonds by looking at them with the naked eye, regardless of method of creation. There are machines a retailer can use to let you know if it is a lab grown or earth-mined diamond. However, the machines cannot tell the process of HPHT or CVD without sending them for a laboratory report. To tell the difference, the stones need to be sent to a lab like GIA or IGI to have the crystal structure studied to determine their process of creation.
During the forming process, man can not dictate what color or quality the lab grown diamonds will come out as. It really depends on the seeds, as any natural impurities that are in the seed when it is growing will dictate the finished stone. Depending on the process used, lab grown diamonds can have a range of the quality that can be predicted but it is still subjective to how it forms when growing. Mother nature is still at work even in a controlled environment. As for the size (carat weight) of the diamonds, the longer you grow or “cook” the seed, the larger it will grow and increase in carat weight.
Bottom line, both processes create a lab grown diamond that is chemically, optically and physically identical to an earth grown diamond. One is not better than the other, they are just different. Think of them like children, you love them all the same but each is unique and different from each other!