1. Floating Topic
2. sedimentary rocks
   1. clastic
      1. shale
      2. sandstone
   2. chemical
      1. bituminous coal
      2. chalk
      3. limestone
3. igneous rocks
   1. extrusive
      1. pumice
      2. rhyolite
      3. obsidian
      4. basalt
   2. intrusive
      1. granite
4. metamorphic rocks
   1. foliated
      1. regional metamorphism
         1. gneiss
         2. schist
      2. Floating Topic
   2. nofoliated
      1. contact metamorphism
         1. slate
         2. Floating Topic
         3. marble
         4. anthracite coal