Diamonds have been admired for their rarity, beauty and indestructible longevity for centuries. These same characteristics have also meant that they are very expensive. Add to this the fact that they are increasingly being sought after for industrial as well as gem use, and it explains why scientists have wanted to grow diamonds in the laboratory for almost two centuries. However, it is only in the latter part of the 20th century that the conditions necessary to replicate natural diamond formation were finally reproduced.
Natural diamonds form under prolonged conditions of high temperatures and pressures over millions of years. Yet synthetic diamonds can be produced in the laboratory in a matter of days or weeks at the most, depending on the diamond produced.
So how are they made?
There are actually two methods which are used to create synthetic diamonds: the high pressure high temperature method (HPHT) and the chemical vapor method (CVM).
HPHT is the most widely used of the two methods. Essentially it copies the processes used to form natural diamonds. A tiny seed diamond is exposed to very high pressures, around 55,000 atmospheres and temperatures of 1400 degrees centigrade in the presence of molten graphite, which is the source of carbon used to grow the diamond, and iron or cobalt catalysts, which act to speed up the process.
In the chemical vapour method high temperatures and pressures are again used to mimic the growth conditions for natural diamonds. However, the carbon source used to grow a diamond seed comes from a gaseous carbon compound which is then split into its elemental components. The resultant carbon then rains onto the seed diamond, growing it as it does so.
CVM can be used to diamond coat objects, such as cutting blades but there are still a lot of problems to be overcome before a large gem grade diamond is grown using CVM.
Both HPHT and CVM produce synthetic diamonds which are atomically identical and have the same physical properties as natural diamonds. However, a tiny diamond is always required to seed the diamond growth. Without it, a diamond could not be produced. So in truth, diamonds cannot be made in a laboratory. They can only be grown bigger in a laboratory!
Synthetics have distinctive growth features associated with their rapid growth, which enable them to be distinguished from mined diamonds by elaborate testing equipment found in major gem testing laboratories. When identified as synthetic, they are minutely marked, which identifies them to all reputable jewelers as man made. So when you come to buy diamond jewelry always make sure you know whether your diamond is natural or synthetic or you may be scammed!