1. Igneous Sedimentary Metamorphic
Rocks
Igneous
Sedimentary
Metamorphic

2. Rocks
Naturally formed, nonliving, firm and coherent mass of solid earth material.
Rocks are classified by their origin (how they formed)

3. Igneous Rocks
Form from the crystallization of a molten mixture of minerals and dissolved gasses.
magma - molten rock underground
lava - molten rock at the surface

4. As the molten rock cools, the ions in the liquid slow down and join into molecules of minerals.

5. Intrusive
If cooling is slow as would happen inside the earth, large/coarse mineral grains will form

7. Extrusive
If cooling is quick as would happen at or near the surface, small/fine mineral grains will form

9. If cooling is too quick, minerals may not form
If cooling is too quick, minerals may not form. (amorphous/glassy texture)

10. In rare cases, magma begins to cool slowly at depth, then rises quickly and cools forming porphyry.

11. If gas bubbles are escaping from lava as it cools, a vesicular texture forms

12. Composition
The mineral composition of igneous rocks depends on the magma from which it solidifies.

13. Felsic Magma/Felsic Rocks
Light color
Low density
Usually form on continents.
Forms rocks that are pink, white, grey

14. Mafic magma/Mafic Rocks
Dark color
High density
Usually form in oceans.
Forms rocks that are black, green, dark grey

15. There’s always an exception
The one exception to this rule is obsidian, which is black in color, but felsic in composition

16. Using the Earth Science Reference Tables
What can we get from the Earth Science Reference Tables:
Environment of formation
Texture
Grain Size
Color
Composition
Density