Rocks and Minerals

1. Rocks and Minerals

2. Mineralsthe building blocks of rocks Mineral Characteristics • natural • inorganic • solid • definite composition • crystal structure

3. Mineral Formation 4 major processes by which minerals form: 1. Crystallization from magma- cooling magma causes minerals to crystallize

4. 2. Precipitation • Minerals dissolve out of evaporated water; precipitated

5. 3. Pressure and Temperature • Change in pressure and temperature cause an existing mineral to recrystallize while still solid Muscovite Talc

6. 4. Hydrothermal Solutions • A hot mixtures of water with substances dissolved in them. When they come in contact with existing minerals- a chemical reaction occurs forming a new mineral Bornite

7. Mineral Composition Minerals are grouped or classified based on their composition. There are 6 groups 1. Carbonates- contain carbon, oxygen, and one ore more metallic element

8. 2. Silicates • formed from silicon and oxygen • elements combined to form a silicon tetrahedron, 1 silicon atom and 4 oxygen atoms • formed from cooling magma • either near the surface (few crystals) or deep below surface (larger crystals)

9. 3. Oxides - Minerals that contain oxygen and one or more other element(s)

10. Gypsum 4. Sulfates and Sulfides - Minerals containing sulfur Pyrite

11. 5. Halides Halite -minerals containing halogen ions plus one or more other elements

12. 6. Native Elements Minerals that exist in a relatively pure form gold, silver, copper Gold crystal structure

13. Mineral Properties Mineral PROPERTIES are used to identify minerals based on specific characteristics Luster Streak Color Specific Gravity Cleavage & Fracture Hardness Magnetism Fluoresence

14. Streak color of a mineral in its powder form Color often not a good property for Iding

15. Luster how light is reflected from the surface of a mineral

16. Cleavage- tendency to break along flat, even surfaces (mica)Fracture- uneven breakage (quartz)

17. Specific Gravity- ratio of a mineral’s density to the density of water Specific Gravity = mass (g) of dry sample mass lost in water Specific Gravity is a ratio…so Specific Gravity has no units

18. Hardness- measure of resistance of a mineral being scratched

19. Magnetism Magnetite Fluorescence Double Refraction Calcite Smell Sulfur

20. Rocks and The Rock Cycle

21. Rocks- any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet • There are 3 major type or families or rock: • Igneous rocks • Sedimentary rocks • Metamorphic rocks

22. Igneous Rocks • Magma- molten material underground • Lava- magma that reaches the surface • Igneous rocks are formed from magma that has cooled and hardened either beneath the surface or from a volcanic eruption

23. 2 Ways to Form Igneous Rock • Intrusive Igneous Rocks- form when magma hardens beneath Earth’s surface • Magma intrudes into existing rocks • Extrusive Igneous Rocks- form when lava hardens on the surface of the Earth • Extruded onto the surface rhyolite granite

24. Magma contains some gases, including water vapor- this make it less dense, so it rises • As magma rises, it cools and forms crystals • The longer the cooling time the larger the crystals

25. Classification of Igneous Rocks Igneous rocks are classified by texture and composition • Texture refers to the appearance of an igneous rock (size, shape, arrangement of crystals) • Composition refers to the proportions of light and dark minerals in the rock

26. Coarse- grained Texture- form as a result of slow cooling, ions can move = large crystal size • Fine-grained Texture- form as a result of quick cooling time, ions lose motion= small crystal size • Glassy Texture- form from lava that cools rapidly, ions don’t have time to arrange = glassy texture • Porphyritic Texture- rocks with different size minerals that form from varying cooling rates

27. Felsic Composition- contain mainly quartz and feldspar, some with biotite mica and amphibole. Make up major rocks of continental crust • Mafic Composition- contain mainly dark colored minerals and feldspar, along with Mg and Fe. Darker and denser than granitic composition

28. Classification of Major Igneous Rocks Texture is crossed with composition to classify igneous rocks. For example, granite has a coarse texture due to slow cooling and larger crystals, and a light color from the light colored quartz and feldspar minerals used to form it.

29. Sedimentary Rocks- formed from compacted and cemented sediments • Weathering physically and chemically breaks rocks into small pieces called sediments • Sediments are moved • by wind, water, ice, • and gravity • Eventually, they are dropped and form layers that are cemented together

30. Weathering, Erosion, and Deposition • Weathering breaks rocks down • Erosion involves weather and the removal of rock • Deposition is the dropping of sediments • Sediments are deposited according to size

31. Compaction and Cementation • Compaction is the process that squeezes the water out of the sediments. It is caused by the weight of the sediments. • Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments. • Cementing holds the sediments together.

32. Classification of Sedimentary Rocks • Clastic Sedimentary Rocks are formed from weathered bits of rocks and minerals • Organic Sedimentary Rocks are formed from living materials • Chemical Sedimentary Rocks are formed when dissolved minerals precipitate from water solution rock salt limestone

33. Sedimentary rocks hold many clues to the Earth’s history • Layers of sediments are records of geologic events on Earth • Fossils are unique to sedimentary rocks

34. Sedimentary rocks drop according to size; larger particles fall first followed by smaller particles

35. Metamorphic Rocks- form when existing rocks undergo change through heat and pressure • Metamorphism means to change • Most metamorphic changes occur at high temperatures and pressure • These occur deep below the Earth’s surface and extend into the mantle

36. Forms of Metamorphism • Contact Metamorphism- forms when magma intrudes into existing rock • Changes in rocks are minor • Regional Metamorphism- formed during mountain building process that occur over a large area • Major changes to rocks

37. Contact metamorphism Regional metamorphism

38. Agents of Metamorphism • Heat- causes existing minerals to recrystallize or new minerals to form • Pressure- causes the spaces between mineral grains to close= more compact rock= greater density

39. Classification of Metamorphic Rocks- based on texture and composition • Foliated Metamorphic Rocks- form when minerals recrystallize at right angles to the direction of force • Causes a layered or banded appearance • Nonfoliated Metamorphic Rocks- no banded texture • Most contain only one mineral

40. Foliated NonFoliated slate marble schist gneiss

41. The Rock Cycle

43. The Rock Cycle Thinking about relationships among the major rock groups

44. Major Rock Groups Igneous Formed from a melt (molten rock) Plutonic (intrusive):slow cooling and crystallization Volcanic (extrusion): quick cooling at the surface • Sedimentary • Formed at the Earth’s surface • Clastic (Mineral Fragments or grains, clays) • Chemical (crystalline chemical/biochemical precipitates) • Organic (made from living material: shells, plants) • Metamorphic • Changed by pressure, heat and fluids.

45. Fig. 2.9 MAGMA

46. IGNEOUS Crystallization MAGMA 46

47. IGNEOUS Intrusive/Plutonic Crystallization MAGMA 47

48. Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Crystallization MAGMA 48

49. Weathering Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Crystallization Uplift MAGMA 49

50. SEDIMENT SEDIMENT Weathering Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Crystallization Uplift MAGMA 50