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Chapter 4 Rocks and Minerals

Chapter 4 Rocks and Minerals . LITHOSPHERE : Earth’s crust and the upper portion of mantle. Mineral Formation. Minerals from Magma: Convection of molten magma in mantle Cooling of rising magma/lava. Minerals from Solution: Dissolved compounds in water Evaporation of water

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Chapter 4 Rocks and Minerals

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  1. Chapter 4Rocks and Minerals LITHOSPHERE : Earth’s crust and the upper portion of mantle

  2. Mineral Formation • Minerals from Magma: Convection of molten magma in mantle Cooling of rising magma/lava

  3. Minerals from Solution: Dissolved compounds in water Evaporation of water Precipitation of minerals

  4. Mineral • 3000 • Naturally occurring • Inorganic • Solid • Substance ( element, compound ) • Definite chemical composition and properties • Definite physical properties.

  5. Composition of Crust • O, Si, Al, Fe, Ca, Na, K, Mg

  6. Physical Properties • Crystal Shape, color, streak, density….. • picture Here !!!!!

  7. Mineral Groups INDICATORS Example • Silicates Si + O + element(s) SiO2 • Carbonates C + O + element(s) CaCO3 • Oxides O + metallic element(s) Fe2O3 • ( Fe, Mg, Al, Cu, Zn, … ) • Sulfates S + 0 + element(s) FeSO4 • Sulfides S + element(s) PbS • Phosphates P + O + element(s) NaH2PO4 • Halides ( F, Cl, Br, I ) + ( Na, K, Ca ) NaCl • Native Elements element Ag

  8. Practice • Underline the Indicator(s) and name the Mineral Group • Ca CO3 • Cu Fe S2 • Fe Al2 (SiO4)3 • Al O3 • Ca SO4 • Na Cl • Na PO3 • C • Ca F • Si O2

  9. Review • Why is Oxygen present in most mineral groups? • It is the most abundant element ( 50 %) in the earth’s crust. • Name the largest mineral group in the Earth’s crust. • Silicates • Compare and contrast Sulfate and Sulfide mineral groups. • Both have Sulfur. • Sulfates are Sulfur + Oxygen • Sulfides are Sulfur without Oxygen • How are Native Elements different from other mineral groups? • Native Elements are made up of only one element. • Other mineral groups are compounds ( more than one element )

  10. Physical Properties • Crystalline Structure: Solid, definite dimensions and angles Crystal Systems • Cubic or Isometric • Tetragonal • Hexagonal • Orthorhombic • Monoclinic • Triclinic

  11. Crystal Systems • 6 crystal models/ lab group • Color • Label • Cut, Fold & Tape • Poster • Crystal System Name • Mineral Example ff Crystal Systems --------------- ---------------

  12. Examples of Crystal systems

  13. Review • Compare and contrast Cubic and Tetragonal systems. • Both have only 90° angles. • Cubic all dimensions are equal. • Tetragonal two dimensions are equal, one is different. • Compare and contrast Monoclinic and Triclinic systems. • Both have no equal dimensions. • Monoclinic ~ one angle at 90 ° • Triclinic ~ No angles at 90 ° • Compare and contrast Tetragonal and Orthorhombic systems. • Both have only 90 ° angles. • Tetragonal ~ two dimensions are equal. • Orthorhombic ~ no equal dimensions

  14. Physical Properties • Color External appearance of an object with respect to light reflected by the object, usually determined visually by measurement of hue and brightness of the reflected light. Color may vary due to the presence of trace elements (impurities). Ex. Quartz SiO2 Rose Quartz Fe, Ti Milky Quartz gas bubbles & liquids Smoky Quartz Al Obsidian Fe

  15. Obsidian

  16. Amethyst Fe2O3 • Tiger eye Fe (Asbestos)

  17. Physical Properties • Luster • The state or quality of shining by reflecting light. • The way light is reflected from the surface of a mineral. • Metallic Ag, Au, Al, FeS2, PbS • Non-metallic • Quartz ( Si O2) Calcite ( Ca CO3) Hematite ( Fe2O3 )

  18. Physical Properties • Texture • Physical characteristic/quality of a surface. How it feels to the touch. Smooth Rough • Obsidian Sandstone • oily soapy • Sulfur Talc

  19. Streak • True color of a mineral • In powder form • Streak does not change. • Gold Au Pyrite FeS2 • Fools Gold

  20. Obsidian

  21. Review • Which physical property of minerals can change due to the presence of other elements? • Color • What can not be assumed about a mineral with a non-metallic luster? • It does not contain metallic elements. • Describe the texture of your desktop. • Smooth, oily, sticky!!, …… • Compare and contrast gold and pyrite minerals in terms of • COLOR • Both are yellow/golden • STREAK • Pyrite has dark green streak. • Gold has yellow streak.

  22. Physical Properties • Hardness • A measure of the ease with which a smooth surface of a mineral can be scratched, or of its resistance to abrasion. • In 1822 the Austrian mineralogist Friedrich Mohs devised a scale based on one mineral's ability to scratch another. • Mohs Hardness Scale Relative hardness of a mineral

  23. Mohs Scale Finger nail 2.5 Glass 5.5 Steel nail 6.5 Streak plate 7

  24. Mohs Scale Practice • Using the Mohs Scale, arrange the following minerals in order of their relative hardness. • E ˃ B ˃ C ˃ A ˃ D • There are 5 mineral samples. • Mineral A is as hard as Calcite. • Mineral B can scratch all but one of the samples. • Mineral C can scratch glass. • Mineral D can be scratched by finger nail. • Mineral E will not leave a streak on a streak plate.

  25. Review Mohs Scale • What does the Mohs Scale measure? • Mohs scale measures the relative hardness of minerals. • How do geologists determine the relative hardness of a mineral? • The mineral is scratched against a known mineral. • If it is scratched and leaves a powder, then it is softer. • If it is not scratched, then it is harder. • Hardness of streak plate is 7. Will quartz leave a streak on the streak plate? Explain why. • No. • It is as hard as the streak plate, and neither will be scratched. • Would Corundum leave a streak on the streak plate? Explain why. • No. • It is harder than the streak plate. It will scratch the plate instead. • What is the hardest mineral? • Diamond used to be the hardest mineral now Lansdaleite and wurtzite boron nitride which were found on a meteor are now harder.Read more: http://wiki.answers.com/Q/What_is_the_hardest_mineral#ixzz29W5pW4E3

  26. Physical Properties • Breakage • The breaking of mineral along atomic bonds. • Fracture: Irregular breaking • Bonds are uniformly strong throughout the mineral • Obsidian • Cleavage : Regular and defined breaks • Breakage along weaker bonds in the mineral • Mica

  27. Physical Properties • Special Properties • Physical property unique to a mineral. • Taste • Halite Na Clsalty • Smell • sulfur, sulfates, sulfides rotten egg smell Pyrite Fe S2 Galena Pb S

  28. Physical Properties • Special Properties Calcite • Chemical Reaction Calcite Ca CO3 reacts with HCl acid CO2 gas • Double Refraction • Calcite light is bent as it goes through double image

  29. Physical Properties • Special Properties • Magnetic Property Magnetite Fe2O3 • Malleability atomic bonds can be reshaped/bent without breaking. Au, Ag, Al, Cu, Fe

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