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New way of mapping gemstones

Scientists say the new technique measures the color patterns of individual gems.
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(CNN) -- American forensic experts say they have come up with a way to map the profile of individual gemstones.

Jewelers and scientists say each gemstone is unique, but until recently, proving this had been difficult.

The new technique, called "microspectrometry," allows this to happen by mapping each stone's color patterns.

Paul Martin, one if the scientists involved in the work and president of California-based company CRAIC Technologies, told CNN that changes in light caused changes in the gemstone colors.

Being able to map this was difficult, especially when it came to measuring ultra violet light, invisible to the naked eye.

The blue in sapphires is caused by the transfer of electrons between charged iron atoms; spinels and rubies are red because of chromium impurities.

Mapping the variations in color will enable jewelers to spot a gem's type and quality, including whether it is a fake. It could also help with identifying stolen gems, Martin said.

He said his company's usual line of work included analyzing forensic data gathered from crime scenes.

The gemstone mapping discovery came about after adapting a technique normally reserved for analyzing glass.

The scientists recorded the wavelengths of light emitted by a 10-micrometer point on the surface of individual stones and found that each had a different spectrum.

The findings were presented at the American Academy of Forensic Sciences meeting in New Orleans last month.

The Gemology Institute of America grades gemstones by mapping their flaws, as well as recording their cut, carat weight and clarity.

George Rossman, a mineralogist at the California Institute of Technology, was skeptical of the claim that every gem's spectrum was different, "New Scientist" reported.

But he accepted that mapping variations in color could provide useful information.

"The question that needs to be researched is whether this tool adds enough to what is out there already," he said.

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