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Minerals

Minerals. Take-Away Points. Chemical elements form in stars Atoms bond by sharing electrons Minerals are classified by their chemistry Minerals can be identified by their physical properties = atomic structure Silicates are the most important mineral group

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Minerals

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  1. Minerals

  2. Take-Away Points • Chemical elements form in stars • Atoms bond by sharing electrons • Minerals are classified by their chemistry • Minerals can be identified by their physical properties = atomic structure • Silicates are the most important mineral group • Crystals are determined by mathematical rules called symmetry

  3. Composition of the Sun 1. Chemical elements form in stars

  4. Composition of the Sun • Abundance of Light Elements • Rarity of Lithium, Beryllium, Boron • Preference for Even Numbers • Abundance peak at Iron, trailing off after 1. Chemical elements form in stars

  5. How Elements Form in Stars • Sun: 4 H  He • He + particle  Mass 5 – Unstable • He + He  Mass 8 – Unstable • He + He + He  C • Add more He to make heavier elements • End of the line is iron for energy production • Atoms beyond Iron made in massive stars 1. Chemical elements form in stars

  6. What are Planets Made of? • Same material as Sun • Minus the elements that remain mostly in gases • We find this pattern in a certain class of meteorites 1. Chemical elements form in stars

  7. Chondrites 1. Chemical elements form in stars

  8. The Earth’s Crust looks Very Different 1. Chemical elements form in stars

  9. Composition of the Crust 1. Chemical elements form in stars

  10. Minerals are the Chemicals that make up the Earth • Naturally Occurring • Inorganic • Chemical Compounds • About 5000 Known • 200 Common • 20 Rock-Forming

  11. Atomic Bonding 1. IONS 2. Atoms bond by sharing electrons

  12. Atomic Bonding 2. Electrical Neutrality • (+) and (-) Cancel Out 3. Bonding (Satisfy 1 & 2) • Ionic (NaCl) • Covalent (O2) • Metallic (Cu, Al, Fe) • Hydrogen (in water) 2. Atoms bond by sharing electrons

  13. Ionic and Covalent Bonding 2. Atoms bond by sharing electrons

  14. Metallic Bonding 2. Atoms bond by sharing electrons

  15. Hydrogen Bonding 2. Atoms bond by sharing electrons

  16. Summary of Bonding • Ionic bonding holds rocks and minerals together • Covalent bonding holds people and other organisms together • Metallic bonding holds civilization together • Hydrogen bonding gives water its heat-retaining and solvent properties 2. Atoms bond by sharing electrons

  17. 4. Lattices • Atoms in crystals form a repeating pattern called a Lattice 2. Atoms bond by sharing electrons

  18. 5. Complex Anions (Radicals) • Many minerals contain groups of atoms that behave as single units 2. Atoms bond by sharing electrons

  19. NAMING MINERALS COLOR • Glauconite (Greek: Glaucos = Blue-green) OTHER PROPERTIES, USES • Magnetite COMPONENTS • Chromite PLACES • Muscovite (Moscow) PEOPLE • Biotite

  20. Chemicals (and Minerals) Are Classified by their Anions 3. Minerals are classified by their chemistry

  21. For Example: Iron Compounds Have Little in Common • Fe: Gray, Metallic • FeCl2: Light Green, Water Soluble • FeSO4: Light Green, Water Soluble • FeCO3: Brown, Fizzes in Acid • FeS2: Dense, Brittle, Metallic, Cubic Crystals 3. Minerals are classified by their chemistry

  22. On the Other Hand, Sulfides have Many Properties in Common • FeS2 • CuFeS2 • PbS • ZnS2 All are Dense, Brittle, Metallic, have Cubic Crystals 3. Minerals are classified by their chemistry

  23. IdentifyingMinerals 4. Minerals can be identified by their physical properties

  24. Identifying Minerals • Color: very variable, complex causes • Hardness: strength of atomic bonds • Density: mass and spacing of atoms • Luster: how electrons interact with light • Cleavage: weak atomic planes • Crystal Form: extremely useful but not for beginners • Other properties distinctive at times 4. Minerals can be identified by their physical properties = atomic structure

  25. Color • Sometimes Distinctive • Often Unreliable • Affected By: • Chemical Impurities • Surface Coating • Grain Size • Weathering 4. Minerals can be identified by their physical properties = atomic structure

  26. Hardness • Resistance to Scratching • Directly related to relative strength of atomic bonds • Scratch Test (Mohs) • Indentation Test (Knoop) Common Errors due to: • Weathering, ‘Chalk' marks • Breaking vs. Scratching 4. Minerals can be identified by their physical properties = atomic structure

  27. Mohs vs. Knoop Scales • Talc: very small • Gypsum, Fingernail: 30 • Calcite, Penny: 135 • Fluorite: 163 • Apatite: 430 • Feldspar, Glass: 560 • Quartz: 820 • Topaz: 1340 • Corundum: 2100 • Diamond: 7000 4. Minerals can be identified by their physical properties = atomic structure

  28. Density • Directly related to masses of component atoms and their spacing • Usually very consistent 4. Minerals can be identified by their physical properties = atomic structure

  29. Density - gm/cm3 (weight relative to water ) • Air: 0.001Wood - Balsa: 0.1, Pine: 0.5, Oak: 0.6-0.9Gasoline: 0.7, Motor Oil: 0.9Ice: 0.92Water: 1.00Sugar: 1.59Halite: 2.18Quartz: 2.65Most Major Minerals: 2.6-3.0Aluminum: 2.7 4. Minerals can be identified by their physical properties = atomic structure

  30. Density • Pyrite, Hematite, Magnetite: 5.0Galena: 7.5Iron: 7.9Copper: 9Lead: 11.4Mercury: 13.6Uranium: 19Gold: 19.3Platinum: 21.4Iridium: 22.4 (densest material on Earth) 4. Minerals can be identified by their physical properties = atomic structure

  31. Luster • Metallic or Nonmetallic is the most important distinction. • Resinous, waxy, silky, etc. are self-explanatory. • Vitreous is often used for glassy luster. 4. Minerals can be identified by their physical properties = atomic structure

  32. Cleavage • Tendency to split along smooth planes of weaknessbetween atoms in crystal • Directly related to atomic structure • Related to Crystal Form • Every cleavage face is a possible crystal face • Not every crystal face is a cleavage face. Quartz commonly forms crystals but lacks cleavage. 4. Minerals can be identified by their physical properties = atomic structure

  33. Other Properties Crystal Form • Takes Luck & Practice • Well-formed crystals are uncommon • Crystal Classification is somewhat subtle Fracture 4. Minerals can be identified by their physical properties = atomic structure

  34. Identifying Minerals Geologic Setting • Some minerals occur in all geologic settings: quartz, feldspar, pyrite • Some minerals occur mostly in sedimentary settings: calcite, dolomite • Some minerals occur mostly in igneous settings: olivine • Some minerals occur mostly in metamorphic settings: garnet, kyanite 4. Minerals can be identified by their physical properties = atomic structure

  35. Identifying Minerals Special Properties • Taste, Magnetism, Etc. Experience and Reading • “The best geologist is the one who’s seen the most rocks.” Professional Methods • Chemical Analysis • X-Ray Studies • Thin Section 4. Minerals can be identified by their physical properties = atomic structure

  36. Diffraction 4. Minerals can be identified by their physical properties = atomic structure

  37. Diffraction 4. Minerals can be identified by their physical properties = atomic structure

  38. A Common Example

  39. Diffraction in Opal 4. Minerals can be identified by their physical properties = atomic structure

  40. MAJOR MINERAL SUITES Elements Metallic:Au, Ag, Cu • Not Al, Pb, Zn, Fe, etc. Nonmetallic: C - Diamond, Graphite • Sulfur 4. Minerals can be identified by their physical properties = atomic structure

  41. Copper Nugget

  42. MAJOR MINERAL SUITES Sulfides: Dense, Usually MetallicMany Major Ores • Pyrite FeS2 • Chalcopyrite CuFeS2 • Galena PbS • Sphalerite ZnS2 • Molybdenite MoS2 4. Minerals can be identified by their physical properties = atomic structure

  43. MAJOR MINERAL SUITES Halides: Usually Soft, Often Soluble • Halite NaCl • Fluorite CaF2 Sulfates: Soft, Light Color • Gypsum CaSO4 • Barite BaSO4 4. Minerals can be identified by their physical properties = atomic structure

  44. MAJOR MINERAL SUITES Oxides: Often Variable, Some Ores • Hematite Fe2O3 • Bauxite Al(OH) 3 (a hydroxide) • Corundum Al2O3 (Ruby, Sapphire) Carbonates: Fizz in Acid, Give off CO2 • Calcite CaCO3 • Dolomite CaMg (CO3)2 4. Minerals can be identified by their physical properties = atomic structure

  45. MOST IMPORTANT MINERAL SUITE: The Silicate Minerals • Si + O = 75% of Crust • Silicates make up 95% + of all Rocks • SiO4: -4 charge • Link Corner-To-Corner by Sharing Oxygen atoms

  46. Nesosilicates - Isolated Tetrahedra • Representatives: • Garnet • Kyanite • Olivine 5. Silicates are the most important mineral group

  47. Sorosilicates - Paired Tetrahedra Epidote is the most common example 5. Silicates are the most important mineral group

  48. Cyclosilicates - Rings • Beryl (Emerald) • Tourmaline 5. Silicates are the most important mineral group

  49. Inosilicates - Chains Single Chains (Pyroxenes) 5. Silicates are the most important mineral group

  50. Inosilicates - Chains Double Chains (Amphiboles) 5. Silicates are the most important mineral group

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