A field classification of fine-grained sedimentary rocks should be simple, based on features of genetic significance, and equally applicable to outcrops, cores, and well cuttings. No published classification meets all of these requirements. Classifications based on the development of fissility are inapplicable to cores and well cuttings and are of little genetic significance. We propose a new classification, based on textural and structural rock attributes. The nomenclature consists of root names which combine information on grain size and stratification. To classify a sample, one needs only to determine its silt content and whether it is laminated.