Based on the structure, the rocks can be classified as following:
A. Stratified Rocks: These rocks have layered structure. They possess planes of cleavage or stratification. They can be simply split along these planes. Sand stones, slate, lime stones etc are the instance of this class of stones.
B. Un-stratified Rocks: These rocks are not stratified. They possess crystalline & compact grains. They cannot be split in to thin slab. trap, Granite, marble etc. are the instance of this type of rocks.
C. Foliated Rocks: These rocks have a tendency to split along only exact direction. The direction required not parallel to each other as in case of stratified rocks. This type of structure is very frequent in case of metamorphic rocks.