Some rocks according to their use or texture are classified into different types. Know more about Mudstone Texture and Conglomerate Texture. Types of Mudstone are Marl, Shale and Argillite whereas the types of Conglomerate are Not Available.During historic times, some rocks depending on their hardness were used to create Pictographs and Petroglyphs. Rocks which are hard were generally not used. Pictographs are paintings or drawings that have been placed or created on the surface of rock. Mudstone and Conglomerate were used for creating pictographs. Petroglyph is an image which is carved into a rock. These are images created by removing part of a rock surface by incising, picking, carving or abrading, as a form of rock art. Mudstone and Conglomerate were used for creating petroglyphs.