Some rocks according to their use or texture are classified into different types. Know more about Gritstone Texture and Tachylite Texture. The types of Gritstone and Tachylite 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. Gritstone was not used to create pictographs whereas Tachylite 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. Gritstone was not used to create petroglyphs whereas Tachylite was used to create petroglyphs.