Rocks and minerals

Rocks and its types

1. Rocks and Minerals Submitted by – Ravi Sah Class – B.Ed. 4 th semester Roll no. – 36 NERIE-NCERT, Umiam, Meghalaya

2. What are rocks? Rocks are made from minerals . A mineral is a naturally occurring inorganic substance with a definite chemical composition found on Earth. A rock may be composed of only one kind of mineral such as pure limestone, which is composed of calcite. Others may have more than one mineral like granite which has three minerals – quartz, feldspar and mica.

3. Cont.... There are 3 major categories of rocks – Igneous Sedimentary Metamorphic

4. IGNEOUS rocks Igneous rocks are formed from magma that has cooled and hardened either beneath the surface or from a volcanic eruption. Coarse-grained rocks(rough) are from magma . Fine-grained rocks(smooth) are from lava . Igneous rocks can be of different types depending on how the magma cools.

5. TYPES OF IGNEOUS rocks GRANITE – It is formed when magma cools slowly under the surface of the Earth.

6. BASALT – It is formed when volcanic lava cools very fast and hardens quickly above the surface of the Earth.

7. OBSIDIAN – It is a dark-coloured igneous rock that is formed when magma cools quickly.

8. PUMICE – It is a light-coloured igneous rock that forms when frothy lava cools quickly on the Earth’s surface.

9. SEDIMENTARY rocks Sedimentary rocks are formed from layers of sediments, created by weathering, and erosion, that are laid down in horizontal strata by water or wind and are squeezed and stuck together. Fossils are usually found in sedimentary rocks.

10. TYPES OF SEDIMENTARY rocks SANDSTONE – It is formed when grains of sand get compressed and cemented together.

11. LIMESTONE – It mainly consists of a mineral called calcite which is formed from the shells and skeletons of tiny sea animals.

12. SHALE – It is formed when layers of clay and silt harden.

13. CONGLOMERATES – It is formed when the lower layers of sediments consist of pebbles and sand.

14. METAMORPHIC rocks Metamorphic rocks are formed when extreme pressure or heat is applied to sedimentary or igneous rocks. The crystalline shape presses together and changes their appearance which makes them tougher and harder.

15. TYPES OF METAMORPHIC rocks MARBLE – It is formed when limestone undergoes changes.

16. QUARTZITE – It is formed from standstone. It is hard and tough.

17. SLATE – It is formed from shale. It splits easily into thin sheets.

18. GNEISS – It is formed from granite. It is coarse grained and has irregular bands of different colours.

19. ROCKS https://youtu.be/t0AS5G5v9co REFERENCES https://www.slideshare.net/goatkell/rocks-minerals-15180147 https://www.slideshare.net/espinorachel/rocks-and-minerals-57767998 https://www.slideshare.net/belalelnagar3/minerals-and-rocks-for-presentations https://www.slideshare.net/luchislinda/rocks-and-minerals-55995096

20. THANK YOU