Gem of an idea from exhaust fumes

A team of Chinese scientists says it has turned carbon dioxide, one of the gases that cars and people pump out, into diamonds.

"We are changing a waste gas into gems," Professor Qianwang Chen, who led the team at the University of Science and Technology of China in Hefei, Anhui province, told New Scientist magazine:

The experiments, which involved a huge amount of compression and heating, at first produced diamonds with diameters of a quarter of a millimetre (one hundredth of an inch) - far too small for jewellery, but just right for industrial uses such as cutting tools and abrasives.

The scientists said the process was improved to make small gemstones and had been completed more than 80 times.

"We can grow diamonds as large as 1.2 millimetres," said Professor Chen. "They are transparent and colourless, and so could be used as gems."

The Chinese diamonds are made by reacting carbon dioxide with sodium in an oven heated to 440C under a pressure of 800 atmospheres.

If the Chinese team can make larger diamonds,the world diamond market might become depressed.

Alison Mainwood, from King's College London, who chairs Britain's Diamond Research Network, said Professor Chen's stones were unlikely to challenge today's industrial diamonds. "I'm sure [their technique] could be improved, but I doubt to the point where it could become a rival," she said.

De Beers, the world's largest diamond mining company, emphasised the importance of keeping manufactured gems distinct from natural ones.