LA-ICP-MS: (Laser ablation-inductively coupled plasma-mass spectrometry): a new way to determine origin and detect treatments of gemstones.

     LA-ICP-MS is an analytical technique used to detect the chemical composition of gems. It reveals both additives from gemstone treatments and trace elements that can help determine a gemstone’s probable geographic origin. And that’s a good thing.

     One of the most troublesome developments in gemstone enhancement in recent years has been the large-scale beryllium diffusion treatment of natural sapphire. This treatment can result in color enhancement including complete color change in some cases. (“Rainbow sapphires” are produced by this treatment.)

     Unlike previous diffusion treatments, beryllium diffusion penetrates the entire stone and is impossible to detect without sophisticated testing. Originally only the yellow-orange-purple-pink part of the spectrum was thought to be affected, but we now know that in all probability, nearly all sapphire undergoes this treatment, including classic blue sapphire.

     In LA-ICP-MS testing, a minute amount of the gem sample is vaporized by a high-energy laser beam, and the vaporized material is ionized into a plasma by a high-frequency power generator. Even trace elements in the parts per billion range can be identified. The test leaves a tiny spot on the surface of the sample, and cut gems are generally tested on the bottom of the stone in an area that can easily be repolished.

     LA-ICP-MS allows gemologists to definitively diagnose beryllium diffusion and other treatments. It also makes possible the cataloging of the precise makeup of gems from specific sources, which may ultimately solve the dilemma of place-name designations.


This month's sources include "Chemical Fingerprinting by LA-ICP-MS” by Abduriyim, Kitawaki, Furuya and Schwarz (Gems and Gemology volume XLII).