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Minerals: Building Blocks of Rocks

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Ultrahigh Vacuum Scanning Tunneling Microscope Image of Galena. Fig. 2.10. Kevin M. Rosso ... E.R. Degginger, Photo Researchers. Polymorphs ... – PowerPoint PPT presentation

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Title: Minerals: Building Blocks of Rocks


1
Minerals Building Blocks of Rocks
Breck P. Kent
2
Mineral
  • A naturally occurring, inorganic solid with an
    ordered internal structure and a narrow range of
    chemical composition

3
What is a mineral
Fig. 2.1
4
Rock
  • A naturally occurring consolidated mixture of
    minerals or mineral-like substances

5
Atoms
  • 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

6
Atoms
  • 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

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

9
Electron cloud
Fig. 2.2a
10
Energy-level shell the space occupied by
electrons of a particular energy level
  • 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 Ar4s23d2

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
Bonding
How are minerals formed?
  • 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
Minerals lots and lots of em
  • 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 Earths crust
  • Carbonates - Ca, Mg and CO3
  • Salts - NaCl
  • Sulfides
  • Oxides

37
Chemical classes
38
Mineral formulas
  • 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

39
Silica-oxygen tetrahedra
  • 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.

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 K2Al4Si6Al2O20(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/felsic
Mafic Silicates
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
51
Sulphates
Sulphates
Galena, PbS
Gypsum, CaSO42H2O
Pyrite, FeS2
52
Carbonates
Carbonates
Dolomite, CaMg(CO3)2
Calcite, CaCO3
53
Carbonate Ion
Atomic Structure of Calcium Carbonate (Calcite)
Fig. 2.21a
54
Atomic Structure of Calcium Carbonate (Calcite)

Fig. 2.21b
55
10 Important minerals
  • Feldspars-Plagioclase feldspar-K orthoclase-gt50
    of crust
  • Quartz-SiO2
  • pyroxene- most common in ocean crust and mantle
    rocks
  • Amphibole-common in continental rocks
  • Mica- platy sheets- perfect cleavage
  • Clay minerals-illite, smectite,
    kaolinite-weathering products
  • Olivine- (Mg,Fe)2SiO4
  • Garnet- independent tetrahedra, like olivine
  • Calcite
  • Dolomite

56
Mineral identification
In hand specimen
  • Color
  • Crystal form
  • Hardness
  • Cleavage
  • Density
  • Streak

57
Hardness scale
58
Cleavage
Atomic Structure of Micas
Fig. 2.23
59
Sheety Cleavage of Mica
Fig. 2.23
Chip Clark
60
Rhomboidal Cleavage of Calcite
Fig. 2.24
Chip Clark
61
Comparison of Cleavage and Crystal Faces
Pyroxene
Amphibole
Fig. 2.25
62
Luster
63
Streak
Hematite
Streak
Fig. 2.26
Brent P. Kent
64
Calcite passes the acid test
Fig. 2.22
65
Composition and crystal structure
66
Chrysotile (a Form of Asbestos)
Runk/Schoenberger/Grant Heilman Photography
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