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Minerals: Building Blocks of Rocks

Minerals: Building Blocks of Rocks. Breck P. Kent. A naturally occurring, inorganic solid with an ordered internal structure and a narrow range of chemical composition. Mineral. What is a mineral. Fig. 2.1. Rock.

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Minerals: Building Blocks of Rocks

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  1. Minerals: Building Blocks of Rocks Breck P. Kent

  2. A naturally occurring, inorganic solid with an ordered internal structure and a narrow range of chemical composition Mineral

  3. What is a mineral Fig. 2.1

  4. Rock A naturally occurring consolidated mixture of minerals or mineral-like substances

  5. A rigid sphere about 1 angstrom (Å) in diameter -- an angstrom is 10-10 m At the center of an atom is a nucleus which contains most of the mass of the atom Protons with a positive charge Neutrons with no charge -- neutral Atoms

  6. Electrons(E): negative charge, very little mass Protons(Z): positive charge, mass 1832 times greater than electron Neutrons(N): no electric charge, mass 1833 times greater than electron Atoms

  7. Abundance of the elements (wt. %) Crust Whole Earth Oxygen 46.3 % 29.5% Silicon 28.2% 15.2% Aluminum 8.2% 1.1% Iron 5.6% 34.6% Calcium 4.1% 1.1% Sodium 2.4% 0.6% Potassium 2.1% 0.1% Magnesium 2.3% 12.7% Titanium 0.5% 0.1% Nickel trace 2.4% All others trace 2.7%

  8. Electrons orbit around the nucleus in discrete shells. Atomic structure Nucleus: protons, neutrons

  9. Electron cloud Fig. 2.2a

  10. First level (K) 2 electrons Second level (L) 8 electrons Third level (M) 18 electrons Fourth level (N) 32 electrons Each level has orbitals that can contain a number of electrons: s, p, d and f orbitals having a maximum of 2, 6, 10 and 14 electrons, respectively K has s, L has s and p, M has s, p and d, N has s, p, d and f orbitals Notation for the electron configuration of an element or ion. Example Titanium, Ti 1s22s22p63s23p64s24p2 or [Ar]4s23d2 Energy-level shell:the space occupied by electrons of a particular energy level

  11. Carbon I L K Fig. 2.2b

  12. Carbon II L K Fig. 2.2c

  13. Carbon III Fig. 2.3a

  14. C-13 Fig. 2.3b

  15. C-14 Fig. 2.3c

  16. Ion • An electrically charged particle composed of an atom that has either lost or gained electron(s) to or from another atom. • When an atom loses or gains an electron it is called an ion. • Positively charged ions (loss of electron) are called cations. • Negatively charged ions (gain of electron) are called anions.

  17. Periodic Table I

  18. Periodic Table II

  19. How are minerals formed? Bonding • Crystallization from a magma • Crystal growth in the solid phase • Precipitation from a solution Two types of bonding: ionic and covalent Ionic bond formed by electrical attraction of ions of opposite charge 90% minerals are ionic bonds Covalent bonds are formed by sharing electrons between atoms Metallic bonds are one type of covalent bonds. Diamond is another example of covalent bonds

  20. Ionic Attraction Forms NaCl (Halite) Fig. 2.4c

  21. Ionic Radii Determine Packing Geometry Fig. 2.13

  22. Ionic Radius and Charge

  23. Electron Sharing in Diamond Fig. 2.5

  24. Carbon Tetrahedron of Diamond Fig. 2.8a

  25. Network of Carbon Tetrahedra Fig. 2.8b

  26. Atomic Structure of Sodium Chloride (Halite) Fig. 2.9

  27. Ultrahigh Vacuum Scanning Tunneling Microscope Image of Galena Fig. 2.10 Kevin M. Rosso & Michael F. Hochella, Jr

  28. Galena Galena PbS Fig. 2.10b Chip Clark

  29. Perfect Crystals Halite (cube) Quartz (hexagonal) Fig. 2.11

  30. Halite (Cubic) and Quartz (Hexagonal) Ed Degginger & Bruce Coleman Breck P. Kent

  31. Quartz Geode Large space allows larger crystals Fig. 2.12 Chip Clark

  32. Graphite Atomic Structure Crystal Form Ken Lucas, Visuals Unlimited Fig. 2.15a

  33. Diamond Atomic Structure Crystal Form E.R. Degginger, Photo Researchers Fig. 2.15b

  34. Polymorphs • Minerals with the same chemical composition but different structure. • e.g., diamond and graphite • andalusite, kyanite, and sillimanite

  35. Polymorphs of Carbon P.L. Kresan

  36. There are some 3,500 recognized minerals found on Earth. However, For our purpose, we can focus on about a dozen. Silicates - Si, O and other elements, the most abundant mineral group in the Earth’s crust Carbonates - Ca, Mg and CO3 Salts - NaCl Sulfides Oxides Minerals: lots and lots of ’em

  37. Chemical classes

  38. Mineral formulas present the chemical composition of the unit cell of a mineral. • Unit cell, the smallest unit of volume that permits identical cells to be stacked together to fill all space • Examples: quartz: SiO2, calcite CaCO3, graphite: C. • Many minerals are not pure chemical substances. • Like solutions they can have a range of compositions • Continuous range of mineral compositions is called “solid solution” • The range in composition is created because at one location in the crystals several elements are permitted • Example: Olivine (Mg,Fe)2SiO4, Elements between brackets indicate a substitution. Endmembers: Fosterite Mg2SiO4, and Fayalite Fe2SiO4. • Some minerals are “garbage cans”: Montmorillonite (Ca,Na)0.33(Al,Mg)2Si4O1((OH)2nH2O Biotite K2(Mg,Fe2+)6-4(Fe3+, Al, Ti)0-3(Si6-5Al2-3O20)(OH,F)4 • Mineral compositions are dependent of P, T conditions during growth and are used as geobarometers and geothermometers Mineral formulas

  39. Building blocks of silicate minerals Four oxygens surrounding a silicon ion. These tetrahedra combine to make the framework of the silicates. Different combinations produce different structures. Silica-oxygen tetrahedra

  40. Silicate Ion[SiO4] 4+

  41. Si-Tetrahedra

  42. Silica tetrahedra Olivine Isolated Tetrahedra Silcate (example: olivine, (Mg,Fe)2SiO4).Cation connects the individual tetrahedra

  43. Chain silicates Hedenbergite Ca(Fe,Mg)Si2O6 Pargasite NaCa2(Mg4Al)(Si6Al2)O22(OH)2 Si2O6, chains are linked by cations Si8O22

  44. Sheet silicates Sheet Silicate (Si,Al)4O10 Muscovite: K2Al4[Si6Al2O20](OH,F)4

  45. Framework Silicate(example: quartz, SiO2) Fig. 2.18

  46. Some Silicate Minerals Mica Feldspar Olivine Pyroxene Quartz Chip Clark Fig. 2.19

  47. Mafic Silicates Mafic/felsic Olivine Pyroxene Felsic Silicates Quartz Feldspar, (K, Na)[AlSi3O8]

  48. Important mineral groups Name Important constituents • Silicates • Olivine Si, Fe, Mg • Pyroxene Si, Fe, Mg, Ca • Amphibole Si, Ca, Mg, Fe, Na, K • Micas Si, Al, K, Fe, Mg • Feldspars Si, Al, Ca, Na, K • Carbonates C, Ca, Mg • Sulfides Fe, Cu, Zn, Ni • Oxides Fe, Al

  49. Some Non-silicate Minerals Gypsum, CaSO42H2O Halite, NaCl Spinel, MgAl2O4 Galena, PbS Hematite Fe2O3 Pyrite, FeS Calcite, CaCO3 Chip Clark

  50. Oxides Hematite, Fe2O3 Corundum, Al2O3 Magnetite, Fe(II)Fe(III)2O4

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