Mudrocks are a class of fine grained siliciclastic sedimentary rocks. The varying types of mudrocks include: "siltstone", "claystone", "mudstone", "slate", and "shale". Most of the particles of which the stone is composed are less than 0.0625 mm (1/16th mm or 0.0025 inches) and are too small to study readily in the field. At first sight the rock types look quite similar; however, there are important differences in composition and nomenclature. There has been a great deal of disagreement involving the classification of mudrocks. There are a few important hurdles to classification, including: