This rock consists of a mixture of clay minerals together with detrital quartz, feldspar, and mica. Iron oxides are also often present.

TEXTURE Mudstone is a very fine-grained rock; the grains cannot be seen with the naked eye. It shares many characteristics with shale and may contain fossils, though it has less well-defined lamination compared to shale.

ORIGIN Mudstone forms in a variety of environments resulting from the deposition of mud in, for example, oceans and freshwater lakes. Studying the fossils contained in a specimen of mudstone and comparing them with the lifestyles of related modern organisms can help identify the type of environment in which the rock was formed.

Grain size: Fine

Classification: Detrital

Fossils: Invertebrates, Vertebrates, Plants

Grain shape: Angular