Minerals

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Minerals Building Blocks of Rocks
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• Mastering Chapter 2 You should know
• What minerals are and how they are
• different than rocks.
• The basic structure of the atom and
• how atoms are used to build minerals
• (bonding).
• How common elements in the earths crust make up
  the various mineral families.
• How to use mineral physical properties and
  identify common rock-forming minerals.
• The definition of a mineral resource and
  understand the characteristics of ore deposits.

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What makes minerals and rocks ?
Rocks
Elements
Minerals
Fe, Mg, Si, O, K
chemical compounds
igneous, sedimentary, metamorphic
silicon (Si)
quartz
granite
oxygen (O)
sandstone
orthoclase
iron (Fe)
gneiss
biotite
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The basic atom model (inside the atom)
Protons
Electrons
Neutrons

• Atomic number
• number of protons
• determines chemical
• characteristics
• range from 1 (H) to
• 92 (Ur)

electron shells

• Atomic mass
• protons neutrons
• neutrons add atomic
• weight
• same atom can have
• varying number of
• neutrons-- isotopes

nucleus
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Germanium atoms (Gr)
cobalt (Co) atoms bonding with copper (Cu) atoms
silicon oxygen (silicate tetrahedron)
Oxygen (4)
Silicon (1)
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Elements and the Periodic Table (PT)
ELEMENTS

• Considered a pure substance
• each element has its own atomic number

• About 118 known elements (92 natural, 26
  synthetic)
• Elements possess distinctive physical properties
• hardness, boiling points
• solid, liquid, or gas

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increasing atomic numbers
Non-metals
Metalloids
METALS
Periods
Groups similar properties
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• Interpreting the PT-

• Atomic number
• number of protons

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Au
Elemental symbol

• Atomic weight
• protons neutrons

197.0
Gold
Element name
So, observing the PT patterns and the definition
of an element,
what characteristics distinguish one element from
another?
Why is an element considered a pure substance????
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Earth Science better the second week.
Discuss with a friend

• What are the parts of an atom? be
• specific (sub-atomic parts).
• 2. How would you describe a chemical
• element?
• 3. What distinguishes one element from
• another?

I will get an A on my exams and quizzes.
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Bonding the atoms (elements)

• Atoms bond using electrons found at the most
  outer electron energy shell (valence shell)

Electrons enter higher shell levels after lower
shell levels have been filled.
Electrons will either be shared or transferred
to other atoms at the valence shell.
Valence shell
e
The atom wants to be satisfied or stable by
filling the electron shells to capacity. Electrons
are lost OR gained when satisfying the outer
shell (valence shell).
e
e
e
P

• Ions the net electric charge of the atom
• loses an electron (positive charge)
• gains an electron (negative charge)
• equal number of electrons/protons
• (electrically balanced neutral)
• Cation ( ions), Anions (-) ions

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e
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Writing a chemical compound (Chemistry
nomenclature)

• Chemical compounds form when combining elements
• at a specific ratio (atom to atom)
• metals (cations) combine with non-metals
  (anions)
• Examples

water
molecule
Na
Cl
NaCl

cation
anion
compound

• Molecule
• smallest chemical unit formed by 2 or more atoms
• held together by electromagnetic forces (bonds)
• expresses properties of the compound

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Combining Elements (Atoms) to Make
Minerals Elements are bonded through electrical
glue using electrons from various element
configurations that form chemical compounds.
Compounds display completely different
physical properties.
Example

NaCl
Na
Cl

• sodium (Na)
• metallic
• soft
• explosive
• lethal!

• chlorine (Cl)
• yellow gas
• lethal!

• halite
• new properties
• compound
• can eat it
• we need it

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Bonding the elements the force that holds the
atoms together in a chemical compound

• Types of bonding (atomic bonds)
• Ionic bonding
• Covalent bonding
• Metallic bonding
• Van der Waals bonding

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The Ionic Bond electrons electrically
transferred
e
1 valence shell
7 valence shell
e
e
e
NaCl
Cl


Na
e
e
e
e
e
Sodium ion wants to lose the electron ()
positive charge ion
Chlorine ion wants to gain the electron (-)
charged ion

• The Ionic Bond
• moderate strength and hardness
• weak bond (salt dissolves in water)

• Mineral examples
• halite (table salt)
• biotite

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Gain or share electrons at the valence shell
Loses electrons at the valence shell () charged
ions
NaCl Halite (Salt)
(-) charged ions
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The Covalent Bond sharing electrons

The Diamond perfect geometry
e
e
e
e
c
c
e
e
e
e
e
e
c
e
e
c
e
e
e
e
e
e
e
e
c
c
e
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e
e

• The Covalent Bond
• the strongest bond
• most minerals will scratch glass
• extremely hard to break the bonds

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Metallic bonding tightly packed atoms
stick to each other (a form of sharing).
Outermost electrons (loosely held) freely move
from one atom to the next.

• good conductors of heat and
• electricity
• heavy dense
• malleable (metals bend easily)
• polish easily

Examples of metallic minerals
galena (PbS)
pyrite (Fe2S)
gold (Au)
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Van der Waals bonding weak attraction
between electrically neutral molecules () end
of the molecule is attracted to the (-) end of
the molecule.
Graphite example
Carbon atoms

• very weak bonds
• easily broken
• layers slip past one
• another

Van der Waals bonds
Covalent bonds
So, why do graphite and diamond display different
physical properties (hardness???) They are both
composed of carbon.
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I
Earth Science.
Discuss with a friend

• What part of the atom bonds together
• to form compounds?
• 3. Explain the differences between ionic,
• covalent, metallic, and Van der
• Waals bonds.

I will get an A on my exams and quizzes.
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What are Minerals?
What objects below do you think are minerals??
Gold
Water
Gasoline
Wood
Diamond
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Why are gold, pyrite, and diamond considered
minerals? The 5-part mineral definition

• Naturally occurring
• Inorganic (non-living)
• Homogeneous solid
• Definite chemical composition
• Definite crystalline internal structure

• 4,000 different minerals (fits 5-part
  definition)
• 25 common minerals combined to form rocks

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the geological sciences.
Discuss with a friend

• What is the 5-part definition of a
• mineral?
• 2. Name 3 substances that are NOT
• minerals and 3 substances that are
• minerals.
• Is ice a mineral? Is water a mineral?
• why or why not?

I will get an A on my exams and quizzes.
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Do all minerals possess a definite or
specific chemical composition?

• Atomic substitution
• Two elements can have similar sizes and be
• substituted within a compound.
• Bonding properties are similar.

• Example the mineral Olivine series (Fe2, Mg2)
• Both ions are similar in size and charge.
• Ions exchange (in ratio) with each other within
  the
• crystal lattice.

Olivine series
Fe2SiO4
Mg2SiO4
(Fe,Mg)2SiO4
fayolite
forsterite
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olivine
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Whats inside a mineral A minerals crystalline
structure (internal geometric shape) is the
result of the atomic arrangement of atoms (how
the atoms align).

• Dependent on
• the size of various combining ions
• how the ions bond together

Cl (Chlorine atom)
Na (Sodium atom)
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Do ALL minerals grow and show the observer
their crystalline shape? (how the atoms combine)
Pyrite
Fe2S
Quartz
SiO2
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Why do some minerals show their internal
structure to the observer?
Time to GROW
Enough SPACE
Enough MATERIALS
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Chihuahua Desert, Mexico
large gypsum crystals formed 150 feet below
the surface
Enough space Enough time Enough solution
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• The atomic arrangement of atoms in a liquid
• there is none
• atoms are randomly arranged
• an amorphous solid
• a liquid-type solid possessing no internal
• structure
• amorphous material has no melting point
• Example
• glass, plastic, wax

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amorphous structure
Waxes
Glass
Plastic
crystalline structure
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I
geology better the second week.
Discuss with a friend

• What dictates a minerals crystalline
• structure?
• 2. What conditions must be met to form
• perfect crystal faces?
• Do all minerals show their crystalline
• structure to the observer (why/why not)?
• 4. Describe the differences between
• amorphous and crystalline structures.

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• Mineral Identification
• Minerals are properly identified using a
  combination of
• physical properties that reflect the minerals
  crystalline
• structure and chemical composition.

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• Physical Properties Used to Identify Minerals
• luster how the mineral reflects light
• hardness the resistance to scratching
• crystal form angle between crystal faces
• cleavage breaks along atomic planes of
• weakness
• streak color of the powdered residue left on a
  
• porcelain plate
• color most noticeable, least reliable
• density How heavy is the mineral for its
  size?

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Luster of the Mineral How the mineral reflects
light Is the mineral metallic or non-metallic?
Metallic luster shiny, like polished metal
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Non-metallic (vitreous, resinous, pearly, greasy,
earthy)
resinous
vitreous
pearly
greasy
earthy
tree sap
pearls
chalk
glassy
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• Hardness of a Mineral
• Is the mineral soft or hard, or how resistant
  is it to
• scratching?
• governed by the minerals crystal structure and
• chemical bonds
• the stronger the bond, the harder the mineral

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Mohs Hardness Scale
Relative hardness, not uniform
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• Crystal faces any solid body that has grown
  with
• flat planar surfaces called crystal faces
• The same mineral may grow in a large, small,
• or skinny form, but the ANGLE between crystal
  faces
• will always remain the same.
• reflects the internal atomic arrangement of
  atoms
• proved by Danish physician- Nicolaus Steno, 1669
• Stenos Law states
• The angle between any corresponding
• pairs of crystal faces of a given mineral is
• constant no matter what the overall shape
• or size of the crystal might be.

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Examples of atom by atom crystal
growth exhibiting various angles
fat, skinny, tall, short, etc all the same angles
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• Cleavage Planes- repeating smooth flat surfaces
  where
• the mineral breaks along planes of atomic
  weakness
• Once the mineral breaks, flat surfaces repeat
  the
• same angle on broken fragments.
• Cleavage angles are consistent.
• Examples

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Mica minerals have one perfect plane of
cleavage, cleave like book pages
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• Streak the color of the powder left on a
  porcelain
• plate (streak plate)
• The mineral is rubbed on a porcelain plate
  leaving
• a colored powder.
• The mineral color does not always give the same
  color
• of powdered residue on the porcelain plate.

Minerals streak
The minerals streak is not always the same color
as the mineral.
Hematite
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Color the appearance of the mineral, What
color are these minerals?
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Don't trust color
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Density- How heavy is the mineral?

• Which weighs more?- a pound of feathers or a
  pound of
• gold??
• How much mass can be packed in a given volume?
• D M/V, units of g/cm3
• high-density minerals closely packed atoms
• low-density minerals less packed atoms

Range of common mineral densities 2.5 g/cm3
3.0 g/cm3

• Experience allows the earth scientist to just
  lift the
• mineral and determine if it is less or greater
  than the
• density range for common minerals.
• metallic minerals feel heavy for their size
• non-metallic (vitreous) minerals feel light for
  their
• size

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I
geology better the second week.
Discuss with a friend

• Briefly describe the following mineral
• physical properties
• luster cleavage
• hardness density
• crystal form color
• streak

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• Mineral Families
• Scientists have identified approx. 4,000
  minerals.
• Whats in a rock? common elements that make up
• rocks

8 elements make up the rock forming
minerals Oxygen (O) 45.20 Silicon (Si)
27.20 Aluminum (Al) 8.00 Iron
(Fe) 5.80 Calcium (Ca)
5.06 Magnesium (Mg) 2.77 Sodium (Na)
2.32 Potassium (K) 1.68
Other gt 1 Ti, H, Mn, P
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• Minerals of the Earths Crust
• Minerals are separated into mineral classes.
• based on the anion complex
• metal (Cation) non-metal (Anion)
• Example NaCl

Cation
Anion
The Mineral Groups according to the anion Oxides
(0) Sulfides (S) Sulfates (S04) Native
Elements Halides (Group 17) Carbonates
(C03) Silicates (Si04)
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What two elements combined would produce the
most abundant mineral group?

Si and 0

• Silicon and Oxygen combined make the Silicate
  mineral group.
• Largest mineral group
• Si 0 (Si04)4-
• Forms the Si04 Tetrahedron
• covalently bonded
• 4 oxygens with 1 silicon
• building block for all silicate minerals
• very strong bond hard to break
• (Si04)-4 unstable, wants to combine with metals

triangles put together very stable makes
tough, hard minerals
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I
geology better the third week.
Discuss with a friend

• 1. How are minerals grouped? Name
• at least four groups.
• 2. Name the two most common elements
• comprising the rock forming minerals.
• Describe the characteristics of the silicate
• tetrahedron.
• 4. Why is the tetrahedron so strong?

I will get an A on my exams and quizzes.
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• How the silicate tetrahedrons bond
• silicate tetrahedron configurations are a
  function of temp.
• bonding of most silicates is a combination of
• covalent and ionic bonds

Silicate tetrahedron
Hot
Single tetrahedron Mg2SiO4
Olivine
Hexagonal ring Be3Al2Si6O18
Beryl
Single chain Ca Mg (SiO3)2
Pyroxene group
Double chain Ca2Mg5(Si4O11)2(OH)2
Amphibole group
Sheet K(MgFe)3(AlSi3O10)(OH)2
Mica group
SiO2
Framework tetrahedron
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Cool
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• Accessory Minerals less common minerals but
• widely present in rocks in small concentrations
• Accessory minerals do not determine the
  properties
• of rocks.
• Some are economically important.
• galena PbS chalcopyrite CuFeS2

(lead ore)
(copper ore)

• Some minerals have the same composition but
• differ in their atomic structure.
• Polymorphs
• graphite and diamond (carbon)
• calcite and aragonite (calcium carbonate)
• pyrite and marcasite (FeS2- iron sulfide)

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Whats in your rock?
Granite
Hornblende
Orthoclase
Quartz
aggregates of minerals
Biological material
Fossil fragments
Plant material
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Understanding rocks is the basic foundation
of knowledge for earth scientists and materials
that make up the earth.

• Every rock speaks to the observer and gives
• clues about where and how it was formed.
• Rocks are divided into 3 major groups
• Igneous
• formed from solidifying hot molten
• rock (magma)

• Sedimentary
• formed on the surface of the earth from
• weathering processes

• Metamorphic
• pre-existing rocks are subjected to
• various pressure and temperature
• relationships

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The Rock Cycle
The Sedimentary Cycle
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• The Rock Cycle
• where the earths internal forces meet
• the earths external forces (at the earths
• surface)

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Earths internal forces
Earths external forces

• the hydrosphere (HC)
• atmosphere
• erosion (wind, water, ice)
• biosphere activities

• moving continents (PT)
• earthquakes
• elevation of mountains
• volcanic eruptions

Produce a continuous cycle of rising mountains
only to be weathered down and uplifted
repeatedly. As a result, igneous sedimentary,
and metamorphic rocks are created.
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geology, especially the rock cycle !!!!!!!!!!!!!
Discuss with a friend

• Briefly identify each rock group and
• its geologic environment.
• 2. Draw the rock cycle, and explain how the
• rock cycle works to your neighbor.
• 3. Why is the rock cycle a cycle???

I will get an A on my exams and quizzes.