UPSC Civil Services GK update – Physical Geography: Rocks and Minerals – Capsule 1
Dear Readers,
Current affairs is an important component of several competitive exams such as the UPSC Civil Services Examination, SSC CGL, Bank PO & PSU entrance tests, etc. Therefore, understanding the terms/concepts/events that make news is critical for aspirants. We at PaGaLGuY bring you series of articles explaining some of these important concepts/events.
In this article we are discussing minerals.
As we know, the Earth is composed of various kinds of elements. On the Earth’s surface, these elements are in solid form while in the Earth’s interior they are in liquid form.
Listed below are the major elements found in the Earth’s crust:
Elements By weight (%)
Oxygen 46.60
Silicon 27.72
Aluminium 8.13
Iron 5.00
Calcium 3.63
Sodium 2.83
Potassium 2.59
Magnesium 2.09
Others 1.41
These major elements combine with each other to form new substances. These substances are called minerals.
Minerals:
a) Minerals are naturally occurring substances formed by geological processes. They are usually crystalline solid, have specific physical properties and chemical compositions.
b) Physical properties of minerals are its crystal structure, hardness (Mohs scale), lustre/luster (how it reflects light), colour, among others.
c) Single-element minerals are also found. For example: silver, gold, graphite, etc.
d) Around 2000 minerals have been found in the Earth’s crust.
e) There are six commonly occurring mineral groups known as major rock-forming minerals.
f) Minerals such as coal, petroleum, & natural gas are organic substances found in solid, liquid & gaseous forms respectively.
Physical characteristics of Minerals:
a) Their external crystal form is determined by the internal arrangement of molecules. This arrangement can be like cubes, octahedrons, etc.
b) Cleavage: Due to the internal molecular arrangement, minerals show a tendency to break in a given direction, producing plain surfaces.
c) Fracture: Due to their complex internal molecular arrangement, the crystal will break in an irregular manner (not along the planes of cleavage).
d) Lustre: It is the appearance of a material without regard to colour. Minerals have distinctive lustre, namely metallic, silky, and glossy, etc.
e) Colour: Minerals have a distinctive colour (malachite, azurite) based on either their molecular structure or impurities present (white, green, red).
f) Streak: It is the colour of ground powder of a mineral. While, malachite is green and gives a green streak, fluorite is green/purple and gives a white streak.
g) Transparency: Minerals can be classified as transparent or translucent or opaque.
h) Structure: The structure of minerals depends on the specific arrangement of individual crystals. A mineral could either be fine, medium or coarse-grained, etc.
i) Hardness: It is the relative resistance of a mineral while being scratched. There are 10 minerals considered to measure the degree of hardness. They are:
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Feldspar
7. Quartz
8. Topaz
9. Corundum
10. Diamond
Specific gravity: It is the ratio between the weight of a given object & weight of an equal volume of water. Every mineral has a different specific gravity.
To get fresh updates about different exams on your Facebook & Twitter timelines, subscribe to our pages created specifically for them. We will post only exam specific links on these pages:
Bank PO:
Facebook: https://www.facebook.com/pagalguybankpo
Twitter: https://twitter.com/PaGaLGuYBankPO
SSC – CGL:
Facebook: https://www.pagalguy.com/ssc
Twitter: https://twitter.com/pagalguyssc
UPSC:
Facebook: https://www.facebook.com/pages/Pagalguy-UPSC/951926044840262
Twitter: https://twitter.com/PaGaLGuYUPSC