Mudstone

A mudstone is a siliciclastic sedimentary rock which has a mixture of silt- and clay-sized particles (at least 1/3 of each).Blatt H; Middleton G & Murray R. 1980. Origin of sedimentary rocks. 2nd ed, Prentice Hall,  Englewood Cliffs, N.J. ISBN  0-13-642702-2 So, a mudstone is a type of mudrock with a more varied grain size than either siltstones or claystones.

Alternatively, some sources say it is a synonym for mudrock.Kearey P. The new Penguin dictionary of geology. London: Penguin Books. p176


 Claystone 
A claystone is a mudrock  which does not split easily.

In order for a rock to be a claystone, it must be up to half (50%) clay, whose particles measure less than 1/256th of a millimeter.

Related pages
Mud

 References 

Category:Sedimentary rocks