1. IGNEOUS ROCKS

2. Igneous means, “() formed”
Solid Rock
Igneous means, “() formed”

3. () is molten (liquid) material () the surface of Earth.

4. MAGMA VS. LAVA Magma – molten material () the surface of the Earth
Lava – molten material () earth’s surface

5. The () cooled and solidified INSIDE Earth into an intrusive igneous rock

6. Molten (liquid) material at the surface of Earth is called ().

7. Extrusive rock is also called () rock.
The lava cooled and solidified () it exited Earth into an extrusive igneous rock

9. When () or () cools it () (a fancy word for something becoming a solid). When this happens crystals form. Solidification can also be called ().
The rocks crystals are minerals.

10. The size of the mineral crystals that form in an igneous rock depend on the ( ).
As a general rule, the () a rock takes to cool, the () the mineral grains will become.
As a result…

11. COOLED FAST at the surface, so either there are no () or they are so () they are not visible.
COOLED SLOW () the surface, so () minerals have time to grow.

14. Lava exposed at the surface cools very fast so no minerals can grow, it looks () or has ().
Earth’s surface
Deep in Earth’s crust

15. If it cools () the surface it grows () mineral crystals but not big enough to see.
Earth’s surface
Deep in Earth’s crust

16. As you get deeper into Earth’s crust magma cools slower
As you get deeper into Earth’s crust magma cools slower. This allows () crystals to grow.
Earth’s surface
Deep in Earth’s crust

17. Really deep in Earth’s crust magma cools really, really ()
Really deep in Earth’s crust magma cools really, really (). This allows mineral crystals to grow really, really ().
Earth’s surface
Deep in Earth’s crust

18. Which is the intrusive rock and which is the extrusive rock?
Pop quiz hot shot!!!
Which is the intrusive rock and which is the extrusive rock?
Extrusive
Intrusive
Fine grained
Large crystals
Basalt
Granite

19. Scheme for Igneous Rock Identification
Reference Tables page 6
Scheme for Igneous Rock Identification
Determining the properties of an igneous rock then identifying it.

21. HOLD ON A SECOND…
What is the definition of texture when we are talking about rocks?

22. Grain Size

23. Non vesicular = No bubbles

24. Bubbles

25. The mineral crystal size

26. Where the rock formed
Exited Earth

27. Where the rock formed
Inside Earth

30. Lets see what these words mean.

31. Contains magnesium & () () colored Dark colored
Contains aluminum
Contains magnesium & ()
() colored
Dark colored
Typical continental rock composition
Typical () rock composition

32. Practice identifying igneous rocks #1

33. Lets try to identify an unknown igneous rock
Use the E.S.R.T.
Lets try to identify an unknown igneous rock
Observed properties of the unknown rock:
1. Light colored
2. Low Density
3. Fine Grained
4. Non vesicular (No gas bubbles)

34. 4. Non Vesicular (Nogas bubbles)
1. Light colored
3. Fine Grained
2. Low density

35. All the rock names are located in this area

36. We need to use texture to narrow it down further
Now we have to see where all our known properties meet in the rock name area
The rock could be any in the highlighted area, according to color and density
We need to use texture to narrow it down further

37. The texture was fine and non vesicular
The only place these two textures match is right here

38. The correct rock is located in the area where all the properties overlap.

39. What do we think our mystery rock is?
Yup, It is a sample of Rhyolite, an extrusive igneous rock
Identifying any other igneous rock works the same way!!!

40. Now lets take our sample of rhyolite and find out what its mineral composition is.

41. Here are the mineral composition percentages
If you do not know where in the rock rectangle to go, assume it is right in the ().
Middle
Here are the mineral composition percentages

42. All of this equals 100% of the rock’s mineral composition.

43. We now want to find the individual mineral percentages in our sample of rhyolite

44. We now want to find the individual mineral percentages in our sample of rhyolite
24% Potassium Feldspar

45. We now want to find the individual mineral percentages in our sample of rhyolite
36% Quartz

46. We now want to find the individual mineral percentages in our sample of rhyolite
21% Plagioclase Feldspar

47. We now want to find the individual mineral percentages in our sample of rhyolite
10% Biotite

48. We now want to find the individual mineral percentages in our sample of rhyolite
8% Amphibole

49. Now we know the mineral composition of rhyolite is;
25% Potassium Feldspar
38% Quartz
20% Plagioclase Feldspar
9% Biotite
8% Amphibole
All the minerals in the rock are accounted for
100%

50. Characteristics of Igneous Rocks
1. Tightly () mineral crystals (unless it looks glassy).

51. Characteristics of Igneous Rocks
2. Intrusive Rocks, formed () inside Earth, have visible (sometimes very ()) ().

52. Characteristics of Igneous Rocks
3. Extrusive rocks, formed () on the () of Earth, will have a () or () texture.