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What is Geology?

What is Geology?.

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What is Geology?

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  1. What is Geology? Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earth’s materials, structures, processes and organisms have changed over time.

  2. Minerals … Why study ‘em? • Building blocks of planet • Industrial minerals • Ore minerals • Energy resources • Gems • Environmental hazards

  3. What is a mineral? • Homogeneous • Naturally occurring • Solid • Inorganic • Definable chemical composition • Orderly arrangement of atoms in a lattice

  4. What is a crystal? quartz Single, continuous piece of crystalline material bounded by flat surfaces Flat surfaces = crystal faces

  5. Crystals have an orderly arrangement of atoms or ions • The shape of the crystal reflects the internal atomic structure.

  6. Properties used to identify minerals • Luster • Color • Streak • Hardness • Specific Gravity • Crystal Form • Cleavage • Special Properties

  7. Streak • Color of the powdered form • Use a ‘streak plate’ Varieties of Hematite streak a reddish-brown

  8. Cleavage vs. Crystal face Crystal Faces • Cleavage planes repeat • No repetition of crystal face within crystal Cleavage Planes

  9. Cleavage • Tendency of a mineral to break on flat planes of weakness.

  10. Cleavage example in Calcite Cleavage planes look like box that has been pushed over Planes of cleavage are parallel to each other

  11. Cleavage in Halite (salt) Cubic cleavage Two directions at 90 Cleavage planes Notice how this sample shows many crystals grown together

  12. Moh’s Hardness Scale 1) Talc 2) Gypsum -- fingernail at 2.5 3) Calcite -- copper (old penny) at 3.5 4) Fluorite -- nail 5) Apatite -- window glass or typical knife blade at under 5.5 6) Orthoclase -- streak plate or good steel file at over 6.5 7) Quartz 8) Topaz 9) Corundum 10) Diamond Soft Hardness is a measure of a minerals resistance to being scratched. It is determined using the “scratch test.” Moh’s Scale is based on a relative scale based on minerals and common materials. Hard

  13. Luster Describes how a mineral reflects light • metallic • nonmetallic • earthy • greasy • vitreous

  14. Color • Often not reliable! • May result from impurities • Except for some… • Olivine = olive green Sulfur = yellow

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