Minerals: Building Blocks of Rocks

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Minerals Building Blocks of Rocks
Breck P. Kent
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Mineral

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

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What is a mineral
Fig. 2.1
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Rock

• A naturally occurring consolidated mixture of
  minerals or mineral-like substances

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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

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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

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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

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Atomic structure
Nucleus protons, neutrons

• Electrons orbit
• around the
• nucleus in
• discrete shells.

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Electron cloud
Fig. 2.2a
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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

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Carbon I
L
K
Fig. 2.2b
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Carbon II
L
K
Fig. 2.2c
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Carbon III
Fig. 2.3a
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C-13
Fig. 2.3b
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C-14
Fig. 2.3c
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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.

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Periodic Table I
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Periodic Table II
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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
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Ionic Attraction Forms NaCl (Halite)
Fig. 2.4c
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Ionic Radii Determine Packing Geometry
Fig. 2.13
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Ionic Radius and Charge
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Electron Sharing in Diamond
Fig. 2.5
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Carbon Tetrahedron of Diamond
Fig. 2.8a
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Network of Carbon Tetrahedra
Fig. 2.8b
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Atomic Structure of Sodium Chloride (Halite)
Fig. 2.9
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Ultrahigh Vacuum Scanning Tunneling Microscope
Image of Galena
Fig. 2.10
Kevin M. Rosso Michael F. Hochella, Jr
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Galena
Galena PbS
Fig. 2.10b
Chip Clark
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Perfect Crystals
Halite (cube)
Quartz (hexagonal)
Fig. 2.11
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Halite (Cubic) and Quartz (Hexagonal)
Ed Degginger Bruce Coleman
Breck P. Kent
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Quartz Geode
Large space allows larger crystals
Fig. 2.12
Chip Clark
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Graphite
Atomic Structure Crystal Form
Ken Lucas, Visuals Unlimited
Fig. 2.15a
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Diamond
Atomic Structure Crystal Form
E.R. Degginger, Photo Researchers
Fig. 2.15b
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Polymorphs
Minerals with the same chemical composition but
different structure. e.g., diamond and
graphite andalusite, kyanite, and sillimanite
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Polymorphs of Carbon
P.L. Kresan
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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

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Chemical classes
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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

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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.

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Silicate IonSiO4 4
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Si-Tetrahedra
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Silica tetrahedra
Olivine
Isolated Tetrahedra Silcate (example olivine,
(Mg,Fe)2SiO4).Cation connects the individual
tetrahedra
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Chain silicates
Hedenbergite
Ca(Fe,Mg)Si2O6
Pargasite NaCa2(Mg4Al)(Si6Al2)O22(OH)2
Si2O6, chains are linked by cations
Si8O22
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Sheet silicates
Sheet Silicate (Si,Al)4O10
Muscovite K2Al4Si6Al2O20(OH,F)4
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Framework Silicate (example quartz, SiO2)
Fig. 2.18
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Some Silicate Minerals
Mica
Feldspar
Olivine
Pyroxene
Quartz
Chip Clark
Fig. 2.19
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Mafic/felsic
Mafic Silicates
Olivine
Pyroxene
Felsic Silicates
Quartz
Feldspar, (K, Na)AlSi3O8
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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
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Some Non-silicate Minerals
Gypsum, CaSO42H2O
Halite, NaCl
Spinel, MgAl2O4
Galena, PbS
Hematite Fe2O3
Pyrite, FeS
Calcite, CaCO3
Chip Clark
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Oxides
Hematite, Fe2O3
Corundum, Al2O3
Magnetite, Fe(II)Fe(III)2O4
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Sulphates
Sulphates
Galena, PbS
Gypsum, CaSO42H2O
Pyrite, FeS2
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Carbonates
Carbonates
Dolomite, CaMg(CO3)2
Calcite, CaCO3
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Carbonate Ion
Atomic Structure of Calcium Carbonate (Calcite)
Fig. 2.21a
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Atomic Structure of Calcium Carbonate(Calcite)

Fig. 2.21b
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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

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Mineral identification
In hand specimen

• Color
• Crystal form
• Hardness
• Cleavage
• Density
• Streak

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