Abstract: Post-glacial Champlain Sea sediments in Quebec and Ontario are often extremely sensitive. Suggestions of considerable amorphous material in these soils come from X-ray diffraction results, as well as electron micrographs. A method for selective dissolution and analysis of amorphous material is used to study two Champlain Sea deposits. The amorphous material removed amounts to 11–12 per cent of the soils and consists mainly of silica and iron oxide. The treated samples have enhanced X-ray diffraction peaks and much cleaner particles as seen by electron microscopy.