Geography Series - 6

Hey Guys, today we will study about Types of Rocks.

Ø  98% earth’s crust composed of 8 elements – Oxygen, Silicon, Aluminium, iron, calcium, sodium, potassium & Magnesium.

Ø  Mineral – Naturally occurring organic & inorganic substance. Normally composed of 2 or more elements but sometimes single element minerals like Sulphur, Copper, Gold, etc are also present.

Ø  Basic source of mineral – magma in interior of earth.

Ø  Hardness of mineral is relative resistance to scratch. 10 minerals to measure degree of hardness are:

1.      Talc (Softest)                     6. Feldspar

2.       Gypsum                              7. Quartz

3.       Calcite                                8. Topaz

4.      Fluorite                               9. Corundum

5.      Apatite                                10. Diamond (Hardest)

o   Fingernail – 2.5

Ø  Major minerals are:

o   Feldspar – Silicon + Oxygen with Calcium, Aluminum, Sodium, Potassium may present in some variety. Half of earth’s crust is Feldspar. Used in ceramics & glass making.

o   Quartz – consists of silica. Used in radio & radar. Granite – quartz + Feldspar.

o   Pyroxene – Calcium + Aluminium + Magnesium + Iron + Silica; forms 10% earth’s crust; found in meteorites.

o   Amphibole – Aluminium + Calcium + Silica + Iron + Magnesium; 7% earth’s crust; Used in asbestos.

o   Mica – Potassium, Aluminium, Magnesium, Iron, Silica,etc. 4 % earth’s crust; used in electrical instruments.

o   Olivine – Magnesium + Iron + Silica; Used in jewellery.

Ø  Minerals are of two types:

o   Metallic-containing metal like gold, silver, platinum, iron, etc.

o   Non metallic- containing non-metals like sulphur, phosphates, and nitrates. Cement- mixture of non-metals.

o   (Metals are hard, opaque, shiny and generally good conductor of heat & electricity).

Ø  Rocks – aggregate of one or more minerals.

Ø  Types of Rocks

 

Ø  Rock Cycle

Ø  This was all about Rocks & mineral you need to remember. Please remember examples of different types of rocks and a bit of major mineral. If you are lucky, they may come directly in the exam. Study hard, get lucky.

Ø  In the next article, we will start with Landforms.

Ø  Ciao !