The Gemprint device, which fires a laser beam through the diamond to create unique internal reflections, goes on the market in Britain later this year.
The London-based Art Loss Register, which scans catalogues, salerooms and auctions on the look-out for stolen gems, is testing the machine.
"Unless you mark a stone in some way, there's no way of telling if it's yours or not when you've lost it," said a spokesman for the register, now tracing 6,000 stolen pieces of jewellery. "Our problem is matching stones which turn up with stones that have been reported stolen."
Scotland Yard is examining the Gemprint machine closely. Officers in the Art and Antiques Squad, which deals with jewellery thefts, are hoping that the device will lead to an improvement in the recovery rate of stolen gems from the current rate of under 1 per cent, compared with a 60-70 per cent success rate for stolen vehicles. There are estimated to be pounds 600- pounds 800m worth of jewel thefts a year in Britain.
Gemprint is also designed to stop a rare practice known as "growing a diamond", whereby jewellers replace a gem during cleaning or resetting with an inferior-quality and lower-value diamond.
The plan is for jewellers to lease the Gemprint, which also provides computer evaluations, at a token rate. Customers can then put stones through the machine at a cost of about pounds 20 and repeat the process to check that they have not been switched.
De Beers, the diamond dealer, said that it was "keeping a close eye" on Gemprint. A spokesman said that if it successfully completed tests, it would help improve consumer confidence. A similar but less sophisticated machine has been in operation in North America for about 10 years.
Diamond owners will keep a certificate of the fingerprint, which looks like a cluster of dots, to identify the stone if it is stolen. The certificate will also help insurers prevent fraud by allowing them to identify stones which are recovered. Only if the gem is recut will the fingerprint change, and even then experts say the print will be similar enough to permit identification. At the moment, it is difficult positively to identify a gem because so many stones are alike.