Some rocks according to their use or texture are classified into different types. Know more about Oil shale Texture and Picrite Texture. Types of Oil shale are Carbonate-rich Shale, Siliceous Shale and Cannel Shale whereas the types of Picrite are Oceanite.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. Oil shale and Picrite were not 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. Oil shale and Picrite were not used for creating petroglyphs.