Chapter - 5
Minerals and Rocks
Elements on Earth :-
Our earth is made up of different types of elements, these elements are not only found separately on the earth's crust, but together with other elements also form different substances.
About 98 percent of the entire Earth's crust is made up of 8 elements. These elements are as follows: -
- oxygen
- Silicon
- aluminum
- iron
- calcium
- sodium
- potassium
- magnesium
Various types of minerals are formed by the combination of elements, these minerals are basically formed by the cooling of magma.
️ Minerals :-
A mineral is a natural inorganic element that has an ordered atomic composition, definite chemical composition and physical properties .
Note: - About 2000 types of minerals have been identified on the earth's crust.
️ Some Major Minerals :-
Feldspar: -
- Feldspar is made up of minerals, silicon and oxygen. Half of the Earth's crust is made up of it.
- Its color varies from light cream to light pink.
- It is used in making porcelain and glass.
Quartz :-
- Its color is white or colorless.
- This mineral is used in radio and radar.
- It is a hard mineral and it is always insoluble in water.
Pyroxene :-
- About 10% of the Earth's surface is made up of pyroxene.
- It contains calcium, aluminum, magnesium, iron and silica.
- It is commonly found in meteorites. Its color is green or black.
Mica Minerals :-
- Mica means mica is found in 4 percent of the earth's crust.
- Potassium, iron, aluminum, magnesium, silica are present in this mineral.
- It is used in electrical equipment.
- It is commonly found in igneous and granite rocks.
Amphibole :-
Amphibole is a mineral. Its main elements are aluminum, calcium, silica, iron, and magnesium. 7% of the Earth's surface is made up of it. It is green and black in colour. Amphibole is used in the asbestos industry. Hornblende is also a type of amphibole.
Olivin : -
The main elements of olivine are magnesium, iron and silica. They are used in jewellery. Generally these are green colored crystals which are often found in basaltic rocks.
️ Types of Minerals :-
- metallic minerals
- non-metallic minerals
️ Metallic Minerals :-
These minerals contain traces of metals.
These minerals can be used again and again by melting them.
These can be divided into ferrous and non-ferrous minerals such as iron, copper, lead, aluminum etc.
️ Non-metallic minerals :-
These minerals do not contain any trace of metals.
They cannot be melted.
They can be used only once such as sulphur, phosphate and nitrate.
The factors that tell the physical characteristics and nature of minerals :-
The physical characteristics and nature of minerals differentiate them from each other. These factors are as follows:-
- The outer appearance of the crystal.
- Withdrawal.
- Partition.
- Glow .
- Colour .
- Transparency.
- hardness.
- relative load.
- stripes.
- structure.
️ Shell :-
The upper part of the earth is made up of rocks. Rocks are made up of one or more minerals. From simple soil to hard rocks are called rocks.
️ Types of Shells :-
There are three types of rocks :-
- igneous
- Depression
- Transformed
️ Igneous rock :-
Igneous rocks are also called primary rocks, these rocks are formed by the cooling of lava and magma . These rocks are impermeable i.e. water or liquids cannot seep through them. They do not even find the remains of fossils. Examples are granite, gabbro, basalt, etc.
️ Sedimentary rock :-
The word depression is derived from the Latin word sediments, which means to settle.
The rock formed by the substances deposited by rivers, winds, glaciers etc. is called sedimentary rock.
The following are their three classifications :-
Mechanically formed: - Such as sandstone, limestone and shale etc.
Formed organically :- Chadia , Coal.
Chemically Manufactured :- Potash, Halite etc.
️ Metamorphic Rock :-
Metamorphic means ' change in form ', these rocks are formed by the process of change in pressure, volume and temperature.
When there is a change in the pressure, temperature and volume of the sedimentary rocks, then metamorphic rocks are formed, due to the sliding of the plates and due to the pressure, the rocks start moving inwards. Due to this pressure these sedimentary rocks break down and a new rock is formed which is called metamorphic rock.
️ Types of Metamorphosis :-
Dynamic Metamorphism : Due to the breaking and grinding of the original rocks, the rocks are re-formed.
Thermal Metamorphism :- In this, chemical change and re-crystallization takes place in the parent rocks.
Territorial Metamorphism : - Due to high temperature and pressure, rocks of a very large area are transformed.
Contact metamorphosis : - The transformation of rocks by coming in contact with hot lava is called contact metamorphosis.
Why are igneous rocks called primary rocks?
Igneous rocks are the oldest on earth. Initially, the parent material on Earth was magma in a molten state. Due to the cooling and solidification of this magma, igneous rocks were formed. Therefore, because they were the first to form, they are called primary rocks. Only after this other rocks - sedimentary and metamorphic were formed.
️ Banded Rocks :-
Sometimes minerals or particles of different groups are arranged in thin to thick surface in such a way that they appear in light and dark colors. Such formations in metamorphic rocks are called banding and rocks showing banding are called banded rocks.
️ Style Chakra :-
Igneous rocks are formed first. The work of weathering and erosion starts on these rocks and the formation of sedimentary rocks starts.
Igneous and sedimentary rocks are transformed into metamorphic rocks under the influence of heat and pressure. Sedimentary rocks after melting at greater depths again become igneous rocks. Metamorphic rocks also turn into igneous rocks by fusion, thus the rocks keep changing their class under favorable conditions.
"The process of converting rocks of one class into rocks of another class is called style cycle. That is, the style cycle is a continuous process, in which the old rocks get changed and take a new form.
️ Shili Bhawan :-
The factors of erosion (such as river, wind) deposit the weathered materials, due to the density and pressure, these accumulated substances turn into rocks, this process is called rock building.
️ Lettering or Illustration :-
When there is a metamorphosis of the original rocks, then some particles or minerals of these rocks get arranged in the form of a surface or line, this is called graphing or drawing.
