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Minerals

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  1. Minerals

  2. Composition of the Sun

  3. Composition of the Sun • Abundance of Light Elements • Rarity of Lithium, Beryllium, Boron • Preference for Even Numbers • Abundance peak at Iron, trailing off after

  4. 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

  5. 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

  6. Chondrites

  7. The Earth’s Crust looks Very Different

  8. Composition of the Crust

  9. Minerals are the Chemicals that make up the Earth • NATURALLY-OCCURRING • INORGANIC • CHEMICAL COMPOUNDS • ABOUT 3000 KNOWN • 200 COMMON • 20 ROCK-FORMING

  10. Atomic Bonding 1. IONS

  11. Atomic Bonding 2. ELECTRICAL NEUTRALITY • (+) and (-) Cancel Out 3. BONDING (SATISFY 1 & 2) • Ionic (NaCl) • Covalent (O2) • Metallic (Cu, Al, Fe) • Hydrogen (in water)

  12. Ionic and Covalent Bonding

  13. Metallic Bonding

  14. Hydrogen Bonding

  15. 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

  16. 4. Lattices • Atoms in crystals form a repeating pattern called a Lattice

  17. 5. Radicals • Many minerals contain groups of atoms that behave as single units

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

  19. CHEMICALS (AND MINERALS) ARE CLASSIFIED BY THEIR ANIONS

  20. 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

  21. On the Other Hand, Sulfides have Many Properties in Common • FeS2 • CuFeS2 • PbS • ZnS2 All are Dense, Brittle, Metallic, have Cubic Crystals

  22. IdentifyingMinerals

  23. IDENTIFYING MINERALS COLOR -Sometimes Distinctive • Often Unreliable • Affected By: • Chemical Impurities • Surface Coating • Grain Size • Weathering

  24. IDENTIFYING MINERALS (Continued) 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

  25. 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

  26. IDENTIFYING MINERALS (Continued) DENSITY • Directly related to masses of component atoms and their spacing • Usually very consistent

  27. 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

  28. 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)

  29. IDENTIFYING MINERALS (Continued) LUSTER • Metallic or Nonmetallic is the most important distinction. • Resinous, waxy, silky, etc. are self-explanatory. • Vitreous is often used for glassy luster.

  30. IDENTIFYING MINERALS (Continued) CLEAVAGE • Tendency to split along smooth planes between atoms in crystal • Thus 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.

  31. IDENTIFYING MINERALS (Continued) CRYSTAL FORM • Takes Luck & Practice • Well-formed crystals are uncommon • Crystal Classification is somewhat subtle FRACTURE

  32. IDENTIFYING MINERALS (Continued) 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

  33. IDENTIFYING MINERALS (Continued) SPECIAL PROPERTIES • Taste, Magnetism, Etc. EXPERIENCE AND READING PROFESSIONAL METHODS • Chemical Analysis • X-Ray Studies • Thin Section

  34. Diffraction

  35. Diffraction

  36. MAJOR MINERAL SUITES ELEMENTS Metallic:Au, Ag, Cu • Not Al, Pb, Zn, Fe, etc. Nonmetallic: C - Diamond, Graphite • Sulfur

  37. MAJOR MINERAL SUITES SULFIDES: Dense, Usually MetallicMany Major Ores • Pyrite FeS2 • Chalcopyrite CuFeS2 • Galena PbS • Sphalerite ZnS2 • Molybdenite MoS2

  38. MAJOR MINERAL SUITES HALIDES: Usually Soft, Often Soluble • Halite NaCl • Fluorite CaF2 SULFATES: Soft, Light Color • Gypsum CaSO4 • Barite BaSO4

  39. 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

  40. 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

  41. Nesosilicates - Isolated Tetrahedra • Representatives: • Garnet • Kyanite • Olivine

  42. Sorosilicates - Paired Tetrahedra Epidote is the most common example

  43. Cyclosilicates - Rings • Beryl (Emerald) • Tourmaline

  44. Inosilicates - Chains Single Chains (Pyroxenes)

  45. Inosilicates - Chains Double Chains (Amphiboles)

  46. Phyllosilicates - Sheets

  47. Phyllosilicates - Sheets Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3 • Micas • Clay minerals • Talc • Serpentine (asbestos) minerals

  48. Tectosilicates - Three-Dimensional Networks • Quartz Feldspars

  49. Unit Cells All repeating patterns can be described in terms of repeating boxes

  50. The problem in Crystallography is to reason from the outward shape to the unit cell

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