A technique used in geochemical exploration and analysis, in which semi-mobile and immobile elements are measured from river or stream sediments, although under some circumstances highly mobile elements, e.g. molybdenum, may be used. Anomalies in sediments are not always accompanied by anomalies in the water, there may be seasonal variations in the composition of stream water, and it is easier to collect, carry, and store sediment samples than water samples. Anomalies may occur in the active sediment and in the banks and floodplains, so sampling of any of these can give satisfactory results. Immobile elements are determined by total-metal analysis; mobile and semi-mobile elements by total- or cold-extractable metal analysis.