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Diamonds may be a girl’s best friend, but how are the sparkling beauties cultivated in the laboratory made?
Lab-grown diamonds have the same carbon structure as natural diamonds. However, the former is manufactured over millions of years, while synthetic materials are formed in days or weeks.
They are usually grown using the high pressure high temperature (HPHT) method. Scientists at General Electric designed the first HPHT method in 1954 to simulate the growth of diamonds deep on the earth's surface. HPHT is the most economical process for growing large diamonds.
The HPHT process starts with a tiny diamond fragment, called a seed crystal. It is placed in the battery inside the press together with a metal catalyst (such as nickel or iron). A piece of pure carbon, such as graphite, is at the top.
The press heats the battery to a scorching high temperature, up to 1,600°C. Then it uses a metal anvil to apply strong pressure. The pressure and temperature need to be high enough to melt the metal catalyst.
The molten metal carries carbon atoms from the graphite to the seed crystal. Carbon atoms slowly accumulate around the crystal, forming what we know as a multilateral structure. The growth rate needs to be controlled to reduce the risk of failure.
After the diamond has cooled, it can be cut and polished, just like the best in nature. The cut, color, carat and clarity can then be graded. Depending on the type of metal, the catalyst can impart color to the diamond.
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