Physical classification

This classification is based on the general structure of rocks. According to this classification, the rocks are divided into three types.

1. Stratified rocks: These rocks possess planes of stratification or cleavage and such rocks can easily be split up along these planes. Sedimentary rocks are distinctly stratified rocks.
2. Unstratified rocks: These rocks are unstratified. The structure may be crystalline granular or compact granular. Igneous rocks of volcanic agency and sedimentary rocks affected by movements of the earth are of this type of rocks.
3. Foliated rocks: These rocks have a tendency to be split up in a definite direction only. Foliated structure is very common in case of metamorphic rocks.

 

Classification of Rocks According to Their Structure

Physical classification	Characteristics	Typical name
1. Stratified rock	Has many strata	Slate
2. Unstratified rock	Does not have strata	Granite
3. Foliated rocks	Has foliated structure	Gneiss