A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition and the way in which it is formed.
Geological Classification:
(i) Igneous Rocks:
These rocks are formed by cooling and solidifying of the rock masses from their molten magmatic condition of the material of the earth. Generally igneous rocks are strong and
durable.
(ii) Sedimentary Rocks:
Due to weathering action of water, wind and frost existing rocks disintegrates. The disintegrated material is carried by wind and water; the water being most powerful medium. Flowing water deposits its suspended materials at some points of obstacles to its flow. These deposited layers of materials get consolidated under pressure and by heat.
(iii) Metamorphic Rocks:
Previously formed igneous and sedimentary rocks under go changes due to metamorphic action of pressure and internal heat.
Physical Classification:
(i) Stratified Rocks:
These rocks are having layered structure. They possess planes of
stratification or cleavage. They can be easily split along these planes.
(ii) Unstratified Rocks:
These rocks are not stratified. They possess crystalline and compact
grains. They cannot be split in to thin slab.
(iii) Foliated Rocks:
These rocks have a tendency to split along a definite direction only. The
direction need not be parallel to each other as in case of stratified rocks. This type of structure is very
common in case of metamorphic rocks.
Chemical Classification:
(i) Silicious rocks:
The main content of these rocks is silica. They are hard and durable.
(ii) Argillaceous rocks:
The main constituent of these rocks is argil i.e., clay. These stones are
hard and durable but they are brittle.
(iii) Calcareous rocks:
The main constituent of these rocks is calcium carbonate. Limestone is a calcareous rock of sedimentary origin while marble is a calcareous rock of metamorphic origin.
*Self Typed
*Source- Books And Internet
*Self Typed
*Source- Books And Internet