Abstract A classification scheme is presented which takes consideration for the sedimentation and frequency of different grain-size mixtures and the dominating influence of clay content upon sediment character. The classification triangle is more detailed and is less uniformly divided than most other schemes. This is required to convey the important changes within different sediment mixtures. This classification is particularly useful when working with unlithified, finer-grained sediments, and attempts to make field and laboratory descriptions more continuous with each other.