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GEOL 108 - Crises of a Planet Lab 5 - Rocks, Weathering, and Minerals Oct. 2 - 5, 2012 Department of Earth Sciences.

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Presentation on theme: "GEOL 108 - Crises of a Planet Lab 5 - Rocks, Weathering, and Minerals Oct. 2 - 5, 2012 Department of Earth Sciences."— Presentation transcript:

1 GEOL Crises of a Planet Lab 5 - Rocks, Weathering, and Minerals Oct , 2012 Department of Earth Sciences

2 REVIEW | 2 QUIZ 3 REVIEW Solid Bedrock Unconsolidated sediments A large earthquake occurs with the epicenter at point C. Is there likely to be more damage at point A or at point B, and why? Bonus: Name these 3 cartoon dogs (1 pt).

3 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 3 LAB 5 - ROCKS, WEATHERING, AND MINERALS Identify minerals Compare clay properties Relate weathering of rocks to clay formation

4 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 4 WHAT IS A MINERAL? Definition of a Mineral: 1.naturally occurring 2.inorganic 3.solid 4.characteristic crystalline structure 5.definite chemical composition steel plastic sugar table salt mercury ice coal basalt obsidian mica gold paper chalk coral no, #1 no, #1,2YES!no, #3YES!no, #2 no, #5no, #4YES! no, #1,2no, #2 Source:

5 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 5 LUSTER Metallic Non-metallic −Glassy (vitreous) −Waxy −Silky −Greasy −Earthy (dull and powdery) −Pearly Shiny ≠ metallic!

6 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 6 COLOR In general, color is not a diagnostic property −Impurities in the crystal can change the color −Color is less variable for minerals with metallic luster

7 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 7 STREAK Streak is the color of a mineral’s powder A mineral’s streak is the same for all specimens regardless of apparent color. Example: Metallic and earthy hematite (Fe 2 O 3 ) both have red- brown streaks.

8 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 8 CLEAVAGE A specific type of breakage Occurs because bonds between atoms are weaker in some directions. There may be up to 6, but usually 1-3 Angles between cleavage directions 1 direction2 directions3 directions (90°) 3 directions (not 90°)

9 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 9 CLEAVAGE One direction of cleavage Example: Mica

10 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 10 CLEAVAGE Two directions of cleavage feldspar hornblende

11 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 11 FRACTURE No planes of weakness leads to irregular or conchoidal fracture

12 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 12 CRYSTAL HABIT A crystal’s habit is the shape it takes when it grows unimpeded by other grains (somewhat rare). Commonly confused with cleavage. Two intergrown Staurolite crystals “St. Andrew’s Cross” twinning

13 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 13 HARDNESS What can a mineral scratch and what is it scratched by? It will only be scratched by harder material. Please don’t test samples on each other!

14 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 14 OTHER PROPERTIES Specific Gravity (density compared to water) Magnetism Reaction to acid (Carbonate minerals –CO3)

15 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 15 THE ROCK CYCLE Clays

16 Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 16 CLAYS Group of minerals, commonly found in sedimentary rocks montmorillonite kaolinite illite (Na,Ca) 0.33 (Al,Mg) 2 (Si 4 O 10 )(OH) 2 ·nH 2 O Al 2 O 3 ·2SiO 2 ·2H 2 O (K,H 3 O)(Al,Mg,Fe) 2 (Si,Al) 4 O 10 [(OH) 2,(H 2 O)]


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