Types of Coal and Wackestone
Some rocks according to their use or texture are classified into different types. Know more about Coal Texture and Wackestone Texture. Types of Coal are Peat, Lignite, Sub-Bituminous Coal, Bituminous Coal, Anthracite, Graphite whereas the types of Wackestone are Marl, Shale and Argillite.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. Coal was not used to create pictographs whereas Wackestone is used to create 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. Coal was not used to create petroglyphs whereas Wackestone was used to create petroglyphs.