LA-ICP-MS is the standard abbreviation for laser ablation inductively coupled plasma mass spectrometry, a chemical analytical technique that combines a laser-ablation sampling system with an ICP-MS detector. It is the principal modern technique for trace-element analysis of gemstones, and is the workhorse of gemstone origin determination at major laboratories including GIA, GRS, AGL, SSEF and Gübelin.

The technique works by directing a focused ultraviolet or near-ultraviolet laser at a small spot on the surface of the gemstone, vaporising a microscopic crater of material approximately 30 to 100 micrometres in diameter and a few micrometres deep. The vaporised material is carried by an argon gas stream into an inductively coupled plasma torch, where it is ionised and fed into a mass spectrometer that separates and counts the ions by mass. The technique provides quantitative concentrations of dozens of trace elements simultaneously, with detection limits typically in the parts-per-million to parts-per-billion range.

For gemstones, LA-ICP-MS is principally used to characterise the trace-element fingerprint of a stone for origin determination. Beryllium-treated sapphires, basalt-related versus metamorphic blue sapphires, Mozambique versus Burmese ruby, Colombian versus Zambian emerald, and many other origin questions are addressed through trace-element ratios (typically of titanium, iron, magnesium, gallium, vanadium, chromium and others). The crater is small enough that the test is generally considered minimally destructive on stones over half a carat, although it leaves a faintly visible mark that requires gentle re-polishing if visible damage is unacceptable.