Rocks and Minerals | Properties and Classification| Learning Concepts
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Minerals and Rocks

Concept: Minerals and Types of Rocks

What are Minerals?

Minerals are inorganic substances formed naturally in the earth and constitute earth’s rocks, sand and soil.

Example: Talc, quartz, feldspar.

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Properties of Minerals:

  • Physical characteristics of minerals are determined based on their colour, hardness, lustre and texture.
  • Mohs Scale determines the hardness of a mineral.
  • The softest mineral is talc, whereas the hardest is diamond.
  • The study of minerals is called Mineralogy.

Types of minerals:

Metallic minerals Non-metallic minerals

The minerals from which metals can be extracted economically. Example : Haematite, Bauxite, Pyrite.


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Haematite

The minerals which do not contain any metal component. Example : Diamond, Clay, Mica.


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Diamond

Ores:

The metallic minerals that we use in our day-to-day lives do not exist in free forms in nature; rather, they remain in combined forms. Ores are those rocks from which metallic minerals can be mined for economic purposes. In other words, ores are mineral-rich rocks.

Example: Bauxite is an ore of the metal aluminium.

Some important metallic minerals and their ores:

S. no. Name of ore Mineral extracted
a. Borax Sodium
b. Bauxite Aluminium
c. Carnalite Potassium
d. Epsom Magnesium
e. Calcite, Gypsum Calcium
f. Cuprite, Pyrite Copper
g. Calamine Zinc
h. Haematite, Magnetite Iron

What is a Rock?

A rock is a naturally occurring solid mass comprising one or more minerals.

Example: Sandstone, shale, basalt, gneiss.

Types of Rocks:

Rocks are classified based on the quality, quantity and arrangement of the minerals.

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Igneous Rocks:

  • These rocks are also called fiery rocks because they are formed from hot molten lava.
  • Molten magma that comes out of the volcanoes and spreads over the earth’s surface is called lava.
  • As soon as the molten lava comes out, it starts to cool down and gradually solidifies over time to form igneous rocks.
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Sedimentary rocks:

  • These rocks are formed by the fragmentation of older rocks by natural forces.
  • As the name suggests, sedimentary rocks are formed by the deposition of sediments of sand, mud or clay.
  • The layers of sediments are deposited and cemented together by minerals that harden over time to form sedimentary rocks.
  • Sedimentary rocks are of scientific importance because scientists use them to analyse the fossils of plants and animals that are embedded in the sedimentary rocks.
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Metamorphic Rocks:

  • The term metamorphic stands for change.
  • Metamorphic rocks are formed due to changes in the existing sedimentary and igneous rocks.
  • These changes occur as a result of high temperature and pressure.
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New Words:

Inorganic substances: Substances that do not originate from plants and animals.

Lustre: The way how light reflects on the surface of a mineral. It is an important property of minerals.

Fossils: Remains of prehistoric plants and animals that remain embedded in rocks and preserved over millions of years.

Temperature: The degreen of hotness or coldness of a body.


Did You Know?

  • There are around 4000 minerals found on the earth's surface.
  • Sulphides are one of the oldest ores. They were formed due to the increased amount of sulphur released due to volcanic activity.
  • Aluminium is the most common element found in the earth’s crust.
  • The world-famous Pyramids of Giza were built using limestone.
  • Igneous rocks can be of two types—intrusive igneous rocks and extrusive igneous rocks.
  • Almost 95% of the earth’s crust is made of igneous rocks.
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