Cm(III) interaction with calcite was investigated by time-resolved laser fluorescence spectroscopy (TRLFS) in the trace concentration range. Two different Cm(III)/calcite sorption species were found. The first Cm(III) sorption species consists of a curium ion bonded onto the calcite surface. The second Cm(III) sorption species has lost its complete hydration sphere and is incorporate into the calcite bulk structure. The Cm(III)/calcite complexes are characterized by their emission spectra (peak maxima at 607.5 and 618.0 nm) and their fluorescence emission lifetimes (314 +/- 6 and 1302 +/- 75 mus).