The uptake of glyoxal (Gly) on 28 different samples with varying mineralogical origins, such as clays, mineral proxies, and natural dusts from the major arid regions of the Earth, was determined. Experiments were performed at ambient temperature inside a Knudsen flow reactor coupled to a molecular-beamsampling mass spectrometer. The objective of using a such high number of mineral surfaces (screening approach) was to identify composition−activity relationships (CAR) that link the elemental composition of the mineral samples with the Gly uptake and to