Nine peatlands were selected according to their various geological setting in the eastern part of France. The diversity of mineral particles, including xenosomes (agglutinated particles) and idiosomes (secreted particles), were analysed, together with associated morphological characteristics, for 7 species of ‘testate amoeba’ (order Arcellinida). The combined use of an Environmental Scanning Electron Microscope equipped with an EDS device and microprobe analyses is suitable for conducting an elemental analysis and subsequently enabled the determination of 24 different minerals. Such mineral diversity has never been recorded before. We conclude that the testate amoebae select grains according to their size from those available within their immediate environment. Availability in turn reflects the geological surroundings and the stability of the different kinds of grains, while their size seems to be a function of the distance from the source.