1. Rocks
Mineral mixtures

2. What are rocks? All natural rocks are aggregates of minerals
The formation of rocks and their physical properties are linked

3. How and where do rocks form?
Many rocks originate from observable processes that take place at the Earth’s surface.
Rocks that do not appear to be like surface rocks give us clues to processes active within the Earth.

4. Rock Classification
Rocks are classified according to the processes that form them.
Formed by the solidification of magma
The breakdown of pre-existing rock
Solid state transformation of minerals in a pre-existing rock.

5. Three types of Rocks
Based on the processes of formation three main categories of rocks are recognized:
Igneous
Sedimentary
Metamorphic

6. Igneous Rocks Crystallized material from molten magma.
Volcanic processes = volcanic rocks
“Beneath the crust” processes = plutonic rocks
Volcanic Rocks = extrusive
Plutonic Rocks = intrusive

7. Cooling of Magma
Rapid cooling of magma (extrusive) normally produces rocks with small mineral grains
Slow cooling of magma (intrusive) normally produces rocks with large mineral grains

8. Sedimentary Rocks
Deposition and precipitation of materials from the breakdown of older rocks
Occurs on Earth’s surface
Weathering can be:
Chemical – materials dissolve in water
Physical – broken fragments (clasts)

9. Deposition vs. Precipitation
Clastic sediments can be lithified (cemented together) to form clastic sedimentary rocks
Fragments are cemented with precipitates or simply by compaction
Materials dissolved in water will precipitate when conditions are right to form chemical sedimentary rocks

11. Bedding
Sedimentary rocks are recognized by distinctive bedding or layering
Bedding is a key feature in recognizing paleo-environments

12. Metamorphic Rocks
Either sedimentary or igneous rocks are transformed by processes occurring within the Earth’s crust.
Increased pressure
Increased temperature
Chemical reactions catalyzed by hot fluids (water most often)

13. Types of Metamorphic Rocks
Regional Metamorphism
Affecting vast areas
Often at plate boundaries
Contact Metamorphism
Very localized
Occurs adjacent to volcanic or plutonic activity

14. 3. Hydrothermal Metamorphism
Hot water flows through the rocks causing a chemical reaction and thus modifying the properties
Often causes the precipitation of metal-ore deposits

16. Minerals found in metamorphic rock depend on the minerals found in the parent rock. And the nature of the metamorphic processes.
Similarities in appearance to sedimentary rocks and igneous rocks
Bedding and banding at first glace look the same
Mineral assemblage appears similar to igneous – generally has more silicates

17. The Rock Cycle