derives from mud clastic sedimentary rock mudstone ORCID:0000-0002-4366-3088 A mudstone is a clastic sedimentary rock which contains a mixture of at least one third of silt- and one third of clay-sized particles. ENVO ENVO:01000272 2013-10-12T14:51:19Z There is debate on the usage of mudstone and mudrock, and some ambiguity is to be expected. https://en.wikipedia.org/wiki/ The terminology of "mudstone" is not to be confused with the Dunham classification scheme for limestones. In Dunham's classification, a mudstone is any limestone containing less than ten percent carbonate grains. Note, a siliciclastic mudstone does not deal with carbonate grains. Friedman, Sanders, and Kopaska-Merkel (1992) suggest the use of "lime mudstone" to avoid confusion with siliciclastic rocks. lime mudstone