Rocks and minerals

1. Rocks and minerals Chapter 17

2. Solid Earth materials No uniform distribution of matter Molten core Heavy elements Iron, nickel Thin surface crust Lighter elements 8 elements make up 98.6% of crust Rocks and minerals make up solid crust materials

3. Minerals Occur naturally Not synthetic, man made. Inorganic solid Not produced by living things. crystalline structure Repeating pattern Example: halite (NaCl)

4. Two groups of minerals Silicates Nonsilicates

5. Silicates Made of one silicon and four oxygen atoms Make 92% of Earth’s crust Example- sand

6. Nonsilicates Not made of just silicon-oxygen Make up remaining 8% of Earth’s crust Eight groups of nonsilicates Carbonates Most abundant Sulfates Oxides Sulfides Halides Phosphates Hydroxides Native elements

7. Physical properties of minerals Color Unreliable Influenced by impurities Streak Color of powdered mineral More reliable Hardness Resistance to scratching Mohs hardness scale Uses ten test minerals with increasing hardness

8. More physical properties Crystal form Internal geometric arrangement of atoms Six basic groups Cleavage Tendency of minerals to break along smooth planes Fracture Irregularity in broken surfaces Luster Surface sheen Metallic, pearly and vitreous Density Mass to volume ratio

9. How Minerals Form Form in two liquid environments most common Water solutions Crystals form when water evaporates Magma Melted rock below Earth’s surface cools Lava: magma forced out to the Earth’s surface and cools to form rock Important factors Temperature Pressure Time Availability elements in solution Glass Rapidly cooled solid lacking a crystalline structure

10. Ore minerals have economic value Often found in veins Thin, flat bodies of mineral material left over from crystallizing magma and flushed away in hot water solutions Examples: pyrite (iron sulfide," fool's gold”), chalcopyrite (sulfide of copper and iron)

11. Rocks Physically mixing of one or more minerals and perhaps other materials Most rocks are silicate minerals Rocks are Classification by How they formed Three main groups Igneous Sedimentary Metamorphic

12. Igneous rocks Formed from magma above or below Earth’s surface All rocks were at one time igneous rocks Cooling rate determines the texture Intrusive igneous rocks Formed beneath surface Slow cooling produces large crystals Coarse grained Extrusive igneous rocks Formed from lava on surface Rapid cooling produces small crystals

13. Igneous rock classification Two factors Mineral composition Texture

14. Sedimentary Rocks form from previously existing rocks Classified as Clastic which form from sediments accumulated from rocks at various stages of breaking down. Named by size of rock particles.

15. Sediment Sedimentary Rocks form from previously existing rocks Classified as- 2. Non Clasitc Which formed from dissolved materials in water. Named by composition.

16. How Sedimentary rock are formed -Lithification Two main parts Compaction Squeezes out water Cementation Spaces between sediment particles filled with chemical deposit

17. Metamorphic rocks Previously existing rocks changed by heat and pressure Changes associated with geologic events such as Movement of the crust Heating and hot solutions from magma intrusion Temperatures must be high enough to cause recrystallization, but not melting Beginning materials

18. Classification of metamorphic rocks Foliation- banded Alignment of flat crystal flakes into sheets Rock breaks along planes between aligned grains Nonfoliated- no bands Parent rocks consist mainly of one mineral Grains not aligned into sheets

19. The rock cycle Rocks transformed into new types by Earths’ interior and exterior dynamical processes Moving continents Seas advance and retreat Weathered and eroded by wind and rain