LIBS, Laser-Induced Breakdown Spectroscopy, is an analytical technique that focuses a high-energy pulsed laser onto a small region of a sample, ablating a microscopic volume of material into a plasma whose emission spectrum is then resolved by a spectrometer. The wavelengths and intensities of the emission lines identify the elements present and, with careful calibration, their relative concentrations. In gemmology LIBS is one of several techniques used to detect treatments and to make origin determinations where elemental fingerprints differ between deposits.

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The most prominent gemmological application has been beryllium-diffusion-treated sapphire and ruby. Beryllium is too light to be detected by the energy-dispersive X-ray fluorescence equipment commonly available on the bench, and its presence at the part-per-million levels associated with diffusion treatment was for a period a major industry concern. LIBS is sensitive to beryllium and to other light elements, and it has been adopted by major laboratories as a routine screen on suspect corundum.

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The technique is mildly destructive: the ablation crater is microscopic, typically a few tens of micrometres across, but it is real and visible under magnification. Laboratories will normally site the test in a region of the stone where the resulting mark will not affect the visible appearance, often near the girdle.