The sorption of americium on 34 common rock forming and accessory minerals of igneous rocks has been measured from an artificial groundwater at ambient temperature. Preliminary results are given. For most of the minerals the distribution coefficient increased sharply with pH in the narrow pH range of 3–5, and then tended to level off and decrease at pH above 8–9. For minerals containing anions such as F‐, CO32‐, and PO43‐, indications of chemisorption were observed. Only for the clays and at low pH can the sorption predominantly be attributed to ion exchange, described by ideal ion exchange equations as indicated from measurements in 4 M NaCl solution.