1. Rocks

2. Composition of Rocks Mixtures of minerals and other materials
20 main rock forming minerals
Main minerals
Quartz
Calcite
Olivine
Dolomite
Pyroxine
Amphibole
Micas : Biotite, Muscovite
Feldspars: Orthoclase, Plagioclase

3. Minerals in Granite

4. What is an igneous rock? Igneous means: "fire-formed rocks"
A rock that is created by cooling Magma
Magma means molten (melted) rock
Lava is magma that is on the Earth’s Surface

5. Classification of Igneous rocks
Location of formation (cooling)
Texture
Composition

6. Location of formation Extrusive Intrusive Form from lava Above Ground
Form from magma
Underground

7. Extrusive Cool more quickly Faster cooling Why? Smaller grain size
Exposed to Air
Faster cooling
Smaller grain size
Smoother texture

8. Intrusive Cool slowly Slower cooling Why? Large grain/crystal size
Inside the earth, heat escapes slower
Slower cooling
Large grain/crystal size
Texture is not smooth

9. Intrusive and Extrusive Rocks

10. Textures Glassy: caused by rapid cooling; no crystals
Pyroclastic: fragments of glass and crystals; volcanic ash and bombs
Aphanitic: microscopic crystals
Phaneritic: macroscopic crystals
Porphyritic: grains of two distinct sizes; can occur in phaneritic or aphanitic matrix

11. Glassy Instantaneous cooling Smooth texture Composed entirely of glass
Few, if any, crystals visible.

12. Pyroclastic Volcanic fragments. Fragments or clasts Vesicular
very fine (ash)
coarse (lapilli)
very coarse (bombs and blocks).
Vesicular
Full of holes

13. Vesicular All magma contains dissolved gasses.
If the magma is thick enough, the gas DOES NOT escape.
Holes called vesicles are left behind giving it a spongy appearance.

14. Aphenitic fine grained texture crystals are too small to see Rocks:
Basalt

15. Phaneritic Crystals large enough to see 2-3cm or slightly smaller
Entire rock is composed of crystals.

16. Porphyritic Crystals of two different sizes
Large crystals (phenocrysts) are visible
Smaller crystal are not

17. Textures Remember Glassy Pyroclastic/Vesicular Fine Grained
Coarse Grained
Know that there are specific names.
Used to identify rocks, rate of cooling, and how they are formed.

18. Composition
Classified based mainly on amount of silica Magma -> Rock
High Silica
Light colored
Low Silica
Dark colored
Silica is the main element in Quartz

19. Composition Terms Felsic/Granitic Intermediate Mafic/Basaltic
Ultramafic/Ultrabasic
High Silica
Low Silica

20. Felsic/Granitic Combines Tend to be light colors Minerals: Feldspar
Silica
Tend to be light colors
Minerals:
quartz,
muscovite mica,
orthoclase feldspars

21. Intermediate In-between Mafic and Felsic
Has both dark and light colors
Minerals of both types

22. Mafic/Basic Combines Tend to be dark colors Minerals Magnesium
Ferrum (Latin for Iron)
Tend to be dark colors
Minerals
olivine,
pyroxene,
amphibole,
biotite mica,
plagioclase feldspars