Minerals: Building blocks of rocks

1
Minerals Building blocks of rocks

• By definition a mineral is
• Naturally occurring
• Inorganic
• solid
• Ordered internal molecular structure
• Definite chemical composition
• Rock
• A solid aggregate of minerals

2
(No Transcript)
3
Composition of minerals

• Elements
• Basic building blocks of minerals
• Over 100 are known (92 naturally occurring)
• Atoms
• Smallest particles of matter
• Retains all the characteristics of an element

4
Structure of an atom

• Electrons move around nucleus in shells / clouds

5
Figure 3.3
6
The Element Carbon on the Period Table
6
Atomic number
C
Why is the atomic mass of carbon not exactly
twelve?
Carbon
12.011
Atomic mass
Atomic number number of protons in an
element Atomic mass sum of the number of
protons and neutrons in an atom
Go to Section
7
Carbons Isotopes
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
6 electrons 6 protons 6 neutrons
6 electrons 6 protons 8 neutrons
6 electrons 6 protons 7 neutrons
Go to Section
8
Isotopes

• Isotopes - atoms of the same element that differ
  in the number of neutrons they contain
• Radioactive Isotopes isotopes with unstable
  nuclei that break down at a constant rate over
  time
• Half life time it takes for half of the atoms
  to decay to the daughter product
• Used to date rocks and fossils

9
Compounds and Chemical Bonds

• Compound substance formed by the chemical
  combination of two or more elements in definite
  proportions
• Octet Rule atoms have a tendency to gain, lose,
  or share electrons so they have 8 outer electrons

10
Ionic bonds Electrons are lost and gained
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na)
Chloride ion (Cl-)
Protons 11 Electrons -11 Charge 0
Protons 17 Electrons -17 Charge 0
Protons 11 Electrons -10 Charge 1
Protons 17 Electrons -18 Charge -1
Transfer of electron

• Most minerals have ionic bonds

Go to Section
11
Ionic bonds Electrons are lost and gained
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na)
Chloride ion (Cl-)
Protons 11 Electrons -11 Charge 0
Protons 17 Electrons -17 Charge 0
Protons 11 Electrons -10 Charge 1
Protons 17 Electrons -18 Charge -1
Transfer of electron

• Most minerals have ionic bonds

12
Halite (NaCl) An example of ionic bonding
13
Covalent bonds Electrons are shared

• Stronger than ionic bonds
• Molecule atoms are joined by covalent bonds

14
Metallic bonding

• Valence electrons are free to migrate among atoms
• Weaker and less common than other bonds
• Ex native copper

15
Minerals Building blocks of rocks

• By definition a mineral is
• Naturally occurring
• Inorganic
• solid
• Ordered internal molecular structure
• Definite chemical composition
• Rock
• A solid aggregate of minerals

16
Geometric packing of ions

• Type is determined by ionic size

Figure 3.8
17
Polymorphs

• Minerals with the same composition but different
  crystalline structures
• Ex Diamond and graphite

18
Physical properties Crystal form

• External expression of a minerals internal
  structure
• Shown only occasionally
• Often interrupted due to competition for space
  and rapid loss of heat

19
Physical properties Color

• Generally unreliable for mineral identification
• Often highly variable

20
Physical properties Streak

• Color of a mineral in its powdered form

21
Physical properties Luster

• Appearance in reflected light
• Metallic
• Nonmetallic
• Subcategories are Glassy, waxy, greasy,
  resinous, pearly, earthy, dull

22
Physical properties Hardness

• Resistance of a mineral to abrasion or scratching
• All minerals are compared to a standard scale
  called the Mohs scale of hardness

23
Physical properties Cleavage

• Tendency to break along planes of weak bonding
• Produces flat, shiny surfaces
• Described by
• Number of planes
• Angles between planes

24
Physical properties

• Fracture
• Absence of cleavage when a mineral is broken
• Density (specific gravity)
• Weight of a mineral divided by weight of an
  equal volume of water
• Average value 2.7

25
Physical properties Others

• Magnetism
• Reaction to hydrochloric acid
• Malleability
• Double refraction
• Taste
• Smell
• Elasticity

26
Rock-forming minerals

• Common minerals that make up most of the rocks of
  Earths crust
• Composed mainly of the 8 elements that make up
  over 98 of the continental crust

27
Abundance of minerals in the Earths Crust
28
Silicate group

• Silicates
• Comprise 96 of crust
• Elements Silicon-oxygen tetrahedron (SiO4)
• Fundamental building block for all silicates
• Four oxygen ions surrounding a much smaller
  silicon ion
• Form Crystallize from magma

29
Silicate group

• Light (felsic)
• Quartz SiO2
• Feldspar KAlSi3O8
• Dark (mafic)
• Pyroxene MgFeSiO3
• Amphibole Ca2MgFeSi8O22
• Olivine Mg2Fe2SiO4
• Uses Glass, circuit boards

30
Carbonate group

• Elements CO3
• Form Crystallize from seawater
• Examples
• Calcite Ca CO3
• Dolomite CaMg CO3
• Uses Cement, fertilizer

31
Halide group

• Elements metal and nonmetal
• Form crystallize from seawater
• Examples
• Halite NaCl
• Fluorite CaF2
• Uses salt, steel-making, fertilizer

32
Native element group

• Form often from hot water associated with
  volcanoes
• Examples uses
• Gold Au - circuits
• Silver Ag
• Copper Cu wires
• Diamond C cutting
• Graphite C pencil, lubricant

33
Oxide group

• Elements O
• Form chemical weathering
• Examples
• Hematite Fe2O3
• Magnetite Fe3O4
• Uses iron ore, pigment

34
Sulfate group

• Elements SO4
• Form crystallize from seawater
• Examples
• Gypsum CaSO4
• Uses Wall board, plaster

35
Sulfide group

• Elements S
• Form crystallize from hot water associated with
  volcanoes
• Examples
• Pyrite FeS2
• Galena PbS
• Uses metal ores

36
Important nonsilicate minerals

• Carbonates
• Primary constituents in limestone, marble, and
  dolostone
• Calcite (CaCO3) and dolomite CaMg(CO3)2 are the
  two most important carbonate minerals
• Hematite (oxide mined for iron ore)
• Halite (halide mined for salt)
• Sphalerite (sulfide mined for zinc ore)
• Native copper (native element mined for copper)

37
Rocks and the rock cycle
38
Igneous rocks

• Interlocking texture
• Igneous means from fire
• Formed when magma cools and hardens
• Magma is molten rock below ground
• Lava is molten rock on or above earths surface
• Ex Granite

39
Sedimentary rocks

• Granular or layered texture
• Natural forces (wind, waves) break down rock into
  small fragments, or sediment
• Sediment is carried and deposited by water, ice,
  and wind
• Sediment can be buried, compressed and cemented
  into sedimentary rocks
• Ex Sandstone

40
Metamorphic rocks

• Banded or foliated texture
• High pressure, heat, and chemical processes can
  change the form of an existing rock.
• The existing rock is then changed into a
  metamorphic rock
• Metamorphic means changed form

41
The rock cycle

• Geological processes cause rock to change from
  one type to another many times
• All rocks have probably passed through the rock
  cycle many times during earths history

42
The rock cycle