geol 108 - crises of a planet
TRANSCRIPT
GEOL 108 - Crises of a Planet Lab 5 - Rocks, Weathering, and Minerals
Oct. 2 - 5, 2012
Department of Earth Sciences
Department of Earth Sciences REVIEW | 2
QUIZ 3 REVIEW
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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).
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
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 no, #1,2 YES! no, #3 YES! no, #2
no, #5 no, #4 YES! YES! no, #1,2 no, #2 no, #2
Source: www.sci.uidaho.edu/geol111/Geology%20101/minerals_II_jh.ppt
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 5
LUSTER • Metallic • Non-‐metallic − Glassy (vitreous) − Waxy − Silky − Greasy − Earthy (dull and powdery)
− Pearly
Shiny ≠ metallic!
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 6
COLOR
• In general, color is not a diagnosPc property − ImpuriPes in the crystal can change the color − Color is less variable for minerals with metallic luster
hRp://nature.berkeley.edu/classes/eps2//wisc/jpeg/l15s32.jpeg
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 hemaPte (Fe2O3) both have red-‐brown streaks.
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 8
CLEAVAGE • A specific type of breakage • Occurs because bonds between atoms are weaker in some direcPons.
• There may be up to 6, but usually 1-‐3 • Angles between cleavage direcPons
1 direcPon 2 direcPons 3 direcPons (90°) 3 direcPons (not 90°)
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 9
CLEAVAGE • One direcPon of cleavage
Example: Mica
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 10
CLEAVAGE • Two direcPons of cleavage
feldspar
hornblende
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 11
FRACTURE • No planes of weakness leads to irregular or conchoidal fracture
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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
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!
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 14
OTHER PROPERTIES
• Specific Gravity (density compared to water) • MagnePsm • ReacPon to acid (Carbonate minerals –CO3)
Department of Earth Sciences ROCKS, WEATHERING, MINERALS | 15
THE ROCK CYCLE
Clays
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(Si4O10)(OH)2·∙nH2O Al2O3·∙2SiO2·∙2H2O (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]