Argillite is one of the important type of rocks. If we have to define Argillite in general, Argillites are highly compact sedimentary or slightly metamorphosed rocks that consist largely or wholly of particles of clay or silt but lack the fissility of shale or the cleavage characteristic of slate. Argillite comes under Sedimentary Rocks. All Sedimentary Rocks have similar properties and formation process. Along with Argillite Definition, know more about the History of Argillite, Etymology of Argillite in next sections.