Types of Rocks | Igneous Rock | Sedimentry Rock | Metamorphic Rock

                                                               

STONE 

Mineral 

Mineral is a solid substance found in its natural state. having a definite chemical organization|

Rocks 

Rock is formed from minerals, depending on the presence of mineral it is of two types.

1. Monominerallic Rock
2. Polyminerallic Rock

Monominerallic Rock

If Rock is formed from Minerals then it is called Monominerallic Rock.

Example – Marble, Gypsum (CaSO4.24H2O) etc.

Polyminerallic Rock

If a rock is formed from two or more minerals, then it is called a Polyminerallic Rock.

Example :- Granite Quatz Felspar Mica

Note: The property of the rock depends on the property of the mineral. Minerals have the following property.

Hardness

It is measured on Moh's Scale.

	Minerals	Moh’s Scale पर Value
1	Tale (soap stone)	1               Scratched
2	Gypsum	2                 by nail
3	Calcite	3
4	Fluorite	4                  Scratched
5	Appetite	5                   by knief
6	Feldsper	6
7	Quartz	7
8	Topaz	8                    Not
9	Corundum	9                    scrached
10	Diamond	10

Geological Classification

·        Magma 

inerals are found in the molten state far below the surface of the earth because the temperature there is very high. It is called Magma. When this magma comes in contact with the atmosphere, it cools, due to which it hardens and it forms rock.

Note:- Quartz, Feldsper, Mica, etc. are mainly found in Magma.

On the basis of Geological Classification, there are following three types of Rocks –

(1.) Igneous Rock 

It is formed by the hardening of magma. Igneous rocks are also classified into three types –

(i) Intrusive Rock ( Plutonic Rock)

If magma cools well below the surface of the earth to form rock, then this type of rock is called Plutonic rock. Here the cooling rate of magma is very low, so their structure is of course grained crystalline.

Example- Grenite, Gabbro, Pigmatite, Synite

(ii) Hyperbessal Rock 

If magma hardens slightly below the surface of the earth and forms rock, then this type of rock is called Hyperbessal Rock, where the rate of cooling of magma is relatively high, so its structure is fine grained crystalline.

Example- Dolerite

(iii) Extrusive Rock ( Volcanic Rock, Effusive Rock)

If the magma cools above the surface of the earth and forms rock, then this type of rock is called extrusive rock, here the rate of cooling of magma is highest, so their structure is externally fine grained.

Example- Basalt, Trap

Note- Igneous rock is called parent rock because all other rock is formed from this rock.

Classification of igneous rock on the basis of parcentage (%) of Silica-

	Type of Rock	Percentage of Silica	Example
1	Acidic Rock	70%- 80%	Granite
2	Intermediate Rock	60%- 70%	Synirte
3	Basic Rock	45%- 60%	Dolerite,Gabbro
4	Ultra Basic Rock	30%- 45%	Basalt

(2.) Sedimentry Rock  , Aqueous Rock, Soft Rock, Layered Rock

Such a rock, which is formed due to some pressure due to the decomposition (decomposition) of the particle, is called Sedimentary Rock. Their structure is granular.

                                                 Sedimentary Rock

                        hemical                     Mechanical                 Organic

                        Deposite                     Deposite                     Deposite

                        (Gypsem)            ( sand stone,Gravel)             ( Shale)

(3.) Metamorphic Rock ( कायांतरित/ रूपांतरित )

Under High Tempeture and High Pressure, the property of parent rock gets changed because the property of their minerals changes. In this way new rock is formed which is called Metamorphic Rock.

Note- (a) metamorphic rock can be stratified or unstratified foliated.

(b) Generally foliated structure is found in metamorphic rock.

(c) In this the arrangement of minerals is in the form of thin parallel layer|

	Ignious Rock, Sedimentary Rock	Metamorphic Rock
1.	Granite   ( High temp.& high press.)	Gniess
2.	Synite                    ”	Gniess
3.	Basalt                    ”	Schist
4.	Lime Stone	Marble
5.	Marl	Marble
6.	Dolerite	Schist
7.	Sand Stone	Quartzite
8.	Shale	Slate
9.	Mud Stone	Slate

Physical Classification-

 (i) Stratified Rock 

In this the layer or plan of stratification is clearly visible, along with which it can be easily divided.

Example- Sedimentary Rock

(ii) Unstratified Rock 

The layer or plan of stratification is not clearly visible in this, so it cannot be divided easily.

Example – Iginious Rock

(iii) Foliated Rock  

In this the layers are very fine, and it can be divided only along a certain direction.

Example- Foliated structure is common in Metamorphic rock.

Chemical Classification –

(i) Clayey Rocks(Argillaceous Rock)

Such a rock in which clay is the main ingredient, it is called Clayey Rock. It is hard and durable, but brittle.

Example: Slate, Leterite, Schist, Kauline  etc.

Note: Shingles are formed by the decomposition of laterite, similarly, morum is formed by dissolution.

(ii) Silicious Rocks : 

Rocks in which silica is the main ingredient are called Silicious Rocks. These Rocks have good strength, and are also hard and durable. They have best resistance to weather|

Example: grenite, vasalt , qvartzite, Trap, etc.

(iii) Calcareous Rock 

Rocks that contain calcium carbonate (CaCO3) as the main ingredient are called calcareous rock, and have the least resistance to weather.

Example: Lime stone , Marble, etc.

Natural Bed

The plane on which the stone is situated in Sedimentary Rock is called its Natural Bed. The natural bed can be easily seen in Sedimentary Rock, as it is located alone along the plan of stratification.

    The stone is placed in the structure in such a way that the load falling on it is perpendicular to the natural bed.

       “In the case of the wall, the natural bed is kept horizontal. In the case of Arch, the natural bed is kept in the radial direction and in the case of Cornice, the natural bed is kept in the Perpendicular (vertical).