The rocks can be classified into three different classes: igneous, sedimentary and metamorphic. The igneous rock can further divided into extrusive and intrusive. The sedimentary rock can be further divided into organic, chemical and clastic. The metamorphic rock can be further divided into foliated and non foliated.
The obsidian is extrusive igneous rock.
The granite is intrusive igneous rock.
The conglomerate is clastic sedimentary rock.
The evaporite is chemical sedimentary rock.
The coal is organic sedimentary rock.
The marble is metamorphic rock.
