1. Igneous Rocks

2. What is a Rock? Rocks are known as an aggregate of minerals.
In other words, they are made from minerals and most rocks contain several different minerals.

3. Rocks that form above the surface are called…
Lava
Volcanic Rocks
Basalt Pumice Obsidian Rhyolite
Rocks that form below the surface are called…
Plutonic Rocks
Granite Gabbro
Magma

4. Volcanic Rocks Plutonic Rocks They are intrusive They are extrusive.
They have
large crystals.
They cool slowly
They are extrusive.
They have
small crystals.
They cool quickly.

5. Igneous rocks have intergrown crystals that fit together like a jigsaw puzzle.
Granite

6. NOT the same as cemented together sediments.
NOT IGNEOUS
Breccia

7. You’re looking mighty fine baby!
Texture: Defines the appearance of an igneous rock.
You’re looking mighty fine baby!
Rocks can be coarse grained, fine grained or glassy.

8. Slow cooling results in large crystals that are visible to the eye.
Coarse
Granite
Diorite
Gabbro

9. Faster cooling results in smaller crystals that are only visible under a microscope.
Fine Grained
Basalt
Rhyolite
Andesite t

10. Very rapid cooling causes rocks to have a glassy texture.
Obsidian

12. Let us take a look at page 6 of your ESRT’s and find all the properties of Granite

13. Texture

14. Density

15. Color

16. Compostion

17. Intrusive or Extrusive

18. Plutonic or Volcanic

19. Minerals

20. Grain Size

21. Bubbles?
Yes= Vesicular

22. The Scheme for Igneous Rock Identification

23. Finding The Minerals Unless you have other information,
work in the middle of the rock’s box.
Identify the rock.

24. This is the amount of Potassium Feldspar in the rock.

25. This is the amount of Quartz in the rock.

26. This is the amount of Plagioclase Feldspar in the rock.

27. Use tick marks on a scrap paper to measure the percentage.
Potassium Feldspar 25%
Quartz 40%

28. Name a light-colored, fine-grained
rock with no bubbles.
Practice

29. Name a coarse-grained, dense rock.

30. Name a very light-colored, glassy,
extrusive rock with bubbles.

31. Important Concept for Plate Tectonics:
Granite (less dense igneous rock) makes up continental crust!
Basalt (more dense igneous rock) makes up oceanic crust.
SO oceanic crust is more dense than continental crust!