Will Artificial Diamonds Soon be Cheap, Mass-Produced ... and Perfect?

A team in the US has brought the world one step closer to cheap, mass-produced, perfect diamonds. The improvement also means there is no theoretical limit on the size of diamonds that can be grown in the lab.

A team led by Russell Hemley, of the Carnegie Institute of Washington, makes diamonds by chemical vapour deposition (CVD), where carbon atoms in a gas are deposited on a surface to produce diamond crystals.

The CVD process produces rapid diamond growth, but impurities from the gas are absorbed and the diamonds take on a brownish tint.

These defects can be purged by a costly high-pressure, high-temperature treatment called annealing. However, only relatively small diamonds can be produced this way: the largest so far being a 34-carat yellow diamond about 1 centimeter wide.

Now Hemley and his team have got around the size limit by using microwaves to "cook" their diamonds in a hydrogen plasma at 2200 °C but at low pressure. Diamond size is now limited only by the size of the microwave chamber used.

The improving quality of synthetic diamonds threatens the natural diamond market. While 20 tonnes of natural diamonds are mined annually, some 600 tons of synthetic diamonds are produced each year for industrial use alone.