Some rocks according to their use or texture are classified into different types. Know more about Skarn Texture and Hyaloclastite Texture. Types of Skarn are Endoskarns whereas the types of Hyaloclastite are Welded tuff, Rhyolitic tuff, Basaltic tuff, Trachyte tuff and Andesitic tuff..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. Skarn was not used to create pictographs whereas Hyaloclastite 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. Skarn was not used to create petroglyphs whereas Hyaloclastite was used to create petroglyphs.