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GEOL 108 - Crises of a PlanetLab 5 - Rocks, Weathering, and MineralsOct. 2 - 5, 2012Department of Earth Sciences

Department of Earth SciencesREVIEW | 2QUIZ 3 REVIEW

Solid BedrockUnconsolidated sedimentsA 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 SciencesROCKS, WEATHERING, MINERALS | 3LAB 5 - ROCKS, WEATHERING, AND MINERALS

Identify minerals

Compare clay properties

Relate weathering of rocks to clay formation

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 4WHAT IS A MINERAL?

Definition of a Mineral:naturally occurringinorganic solidcharacteristic crystalline structuredefinite chemical compositionsteel plastic sugar table salt mercury ice coalbasalt obsidian mica gold paper chalk coralno, #1no, #1no, #1,2YES!no, #3YES!no, #2no, #5no, #4YES!YES!no, #1,2no, #2no, #2Source: www.sci.uidaho.edu/geol111/Geology%20101/minerals_II_jh.pptDepartment of Earth SciencesROCKS, WEATHERING, MINERALS | 5LUSTERMetallicNon-metallicGlassy (vitreous)WaxySilkyGreasyEarthy (dull and powdery)Pearly

Shiny metallic!

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 6COLOR

In general, color is not a diagnostic propertyImpurities in the crystal can change the colorColor is less variable for minerals with metallic luster

http://nature.berkeley.edu/classes/eps2//wisc/jpeg/l15s32.jpegDepartment of Earth SciencesROCKS, WEATHERING, MINERALS | 7STREAK

Streak is the color of a minerals powderA minerals streak is the same for all specimens regardless of apparent color.

Example: Metallic and earthy hematite (Fe2O3) both have red-brown streaks.Department of Earth SciencesROCKS, WEATHERING, MINERALS | 8CLEAVAGE

A specific type of breakageOccurs because bonds between atoms are weaker in some directions. There may be up to 6, but usually 1-3Angles between cleavage directions

1 direction2 directions3 directions (90) 3 directions (not 90)Department of Earth SciencesROCKS, WEATHERING, MINERALS | 9CLEAVAGE

One direction of cleavage

Example: Mica

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 10CLEAVAGE

Two directions of cleavage

feldsparhornblendeDepartment of Earth SciencesROCKS, WEATHERING, MINERALS | 11FRACTURE

No planes of weakness leads to irregular or conchoidal fracture

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 12CRYSTAL HABIT

A crystals habit is the shape it takes when it grows unimpeded by other grains (somewhat rare).Commonly confused with cleavage.

Two intergrown Staurolite crystalsSt. Andrews Cross twinningDepartment of Earth SciencesROCKS, WEATHERING, MINERALS | 13HARDNESS

What can a mineral scratch and what is it scratched by? It will only be scratched by harder material.Please dont test samples on each other!

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 14OTHER PROPERTIES

Specific Gravity (density compared to water)Magnetism Reaction to acid (Carbonate minerals CO3)

Department of Earth SciencesROCKS, WEATHERING, MINERALS | 15THE ROCK CYCLE

ClaysDepartment of Earth SciencesROCKS, WEATHERING, MINERALS | 16CLAYS

Group of minerals, commonly found in sedimentary rocks

montmorillonite

kaolinite

illite

(Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2nH2O

Al2O32SiO22H2O

(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]