What is Physical & Chemical Classification oF rock ?

What is physical & chemical classification 

PHYSICAL CLASSIFICATIONS OF ROCKS

Physical classification mainly depends upon the structure of the rock.It may be classified into 

1. Stratified Rocks : These are the rocks which have distinct layer in their structure i.e. these rocks show a layered structure. stratified rock possesses planes of stratification and can be easily spilt up along these planes . The planes are also known as cleavage planes or bedding planes. limestone , slate , shale , sandstone , marble are the examples of stratified rocks.

2. Unsatisfied Rock or Massive Rocks : These are the rocks which do not show distinct layers in their structure. They have the compact massive structure. Unstratified rocks cannot be separated in top layers. The examples of such rocks are Quarzite ,Basalt etc.

3. Foliated or Laminated Rocks : These are  the rocks which have the tendency to spilt up in adefinite direction only. Foliated structure is quite common in metamorphic  rocks.

CHEMICAL CLASSIFICATIONS OF ROCKS

Chemical composition is the criterion for this type of classification. Based on it, rocks can be divided into following three categories :

⦁ Argillaceous Rocks
⦁ Silicious Rocks
⦁ Calcareous Rocks

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1. Argillaceous Rocks: The main constituent of these type of rocks is clay or alumina (AL2O3). This clay or alumina remains mixed up with silicious , calcareous and carboneous matter in varying proportion .In this type of rocks generally clay content is greater than 50%. Laterite Slate , Shale , are example of Argillaceous Rocks .

2. Silicious Rocks : Silica (SiO2) is the predominant constituent in this type of rocks . silica content is more than 50% in this types of rocks Hardness and durability are main properties of silicious rocks. The examples of silicious , Rocks and Sandstone , Granite ,Trap ,Syenite etc.

3. Calcereous Rocks : The principle constituent of this type of rocks is calcium. So atmosphere is the main consideration while using these type of rocks . the example are Marble , Dolomite , Limestone etc.

 
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