A unique characteristic of many naturally cemented sensitive soils is that they are made up of finely ground fresh rock debris, "rock flour", much of which is very susceptable to chemical weathering or decomposition. Many of these minerals can be identified by X-ray diffraction. The decomposition of these minerals produces secondary products which can act as effective natural cements. A process is outlined whereby the sequence of deposition, weathering and cementation can account for the observed mechanical behaviour of naturally cemented soils.