Transcript Minerals

III. Atoms, Elements and Minerals
A. Changing scales to looking at the
elements of the earth and its crust (8 most common)
 B. Introduction to minerals that comprise rocks
(11 most common)
 C. The silicate minerals (7)
 D. Other important rock-forming minerals (4)
 E. Mineral properties
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A. Changing Scale: Zooming in from global view to atomic scale
Quartz
Biotite
Feldspar
The crust is made of rocks > Rocks are made of minerals > …
A. Changing Scale: Zooming in from global view to atomic scale
Rocks are made of minerals > Minerals are made of atoms
Atoms and Elements
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Nucleus
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Protons
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+ Charge
Has Mass, Atomic #
Neutrons
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See Fig. 3-3, p. 56
0 Charge
Mass same as One Proton
Atomic Mass #
Electrons
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In shells (2, 8, 8…)
- charge (balances each
proton +)
Very little Mass
Electron
Shells
Ions
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Incomplete electron
shells tend to be filled
E.g. Chlorine (Cl-)
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17 protons (at.# 17)
17 electrons would make it
neutral (no charge) with the
last shell one electron short
{2, 8, 7} Soooo…
Tends to grab an electron to fill the third shell
Making it a negatively charged Ion (anion)
Ions
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Other Common
Examples
Sodium
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Sodium, at.# 11
{2, 8, 1}  Na+ (Cation)
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Oxygen, at.# 8
{2,6},  O-2
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Silicon, at.# 14
{2,8,4}  Si+4
Oxygen
Most Common Elements of
Earth’s Crust
Oxygen:
Silicon:
Aluminum:
Iron:
O-2
Si+4
Al+3
Fe+2 or +3
Calcium: Ca+2
Sodium: Na+1
Potassium: K+1
Magnesium: Mg+2
Table 3-2, p. 63
Fig. 3-9, p. 62
B. Introduction to Minerals
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Halite (Rock Salt)
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Mineral mined for rock
salt and table salt
Na gives electron to Cl
Opposites attract,
elements bond
NaCl (Sodium Chloride)
See Fig. 3-5, p. 57
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Intro to Minerals
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Repeating 3-D pattern forms a
Crystalline Solid (or Crystal)
Naturally occurring crystals
are Minerals
Definite Chemical compositionCrystal Form
(usually a range)
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Crystalline structure and bonding
leads to physical properties:
hardness, crystal form,
cleavage, density (specific
gravity )
3 planes of cleavage
Some Familiar Crystal Forms
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Quartz Crystal
(SiO2)
Fig. 3-2a, p. 55
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Snow Flake (Ice Crystal) due
to crystalline structure of H2O
Fig. 2.15a
Table 3-3, p. 63
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
See Fig. 3-10, p. 63
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra
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The building block of
most common rock
forming minerals
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Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
-4
C. Silica Tetrahedra and Silicate
Minerals
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Si and O bond in a
tetrahedron shape
The basic building block
of most minerals of the
crust
Bond with other
tetrahedra and cations to
form Silicate Minerals
Fig. 3-11, p. 64
Silicate Minerals: Examples
E.g., Olivine
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Isolated silicate
structure
(SiO4)-4 + 2×Fe+2
Fe2SiO4
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Fe Mg SiO4
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Mg2SiO4
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Definite Range
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(Fe,Mg) 2 SiO4  Olivine Mineral Group
Silicate Minerals: Examples
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E.g., Olivine
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Isolated silicate
structure
bonded with iron
and magnesium
Makes up much
of the mantle
Fe/Mg rich >50%
Silica poor <45%
Silicate Minerals: Examples
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E.g., Pyroxenes (Mineral Group)
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Single Chain Silicate structure
(SiO3)-2 + Fe+2
FeSiO3
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(Fe,Mg) SiO3
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MgSiO3
(Fe,Mg) SiO3  Pyroxene
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Mineral Group
Ferromagnesian
Silicate Minerals: Examples
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E.g., Pyroxenes (Group of
minerals)
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Single Chain Silicate structure
bonded with Fe, Mg, Ca, and Al
Found in Oceanic Crust
Fe/Mg/Ca rich (20%)
Silica poor
(<20%)
Building Silicates
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What is the net charge of:
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a silica tetrahedron?
a single chain of single
tetrahedra?
*Hint: a shared apex is ½ an Oxygen
Building Silicates
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What is the net charge of:
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a silica tetrahedron?
a single chain of single
tetrahedra?
a double chain of tetrahedra?
a sheet of tetrahedra?
a framework of tetrahedra?
a framework of tetrahedra with
every fourth silicon replaced with
an aluminum ion?
a framework with every other Si
replaced with an Al?
*Hint: a shared apex is ½ an Oxygen
Building Silicates
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What common elements would balance
the charges of :
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an isolated silicate?
a single chain silicate?
a double chain silicate?
a sheet silicate?
a framework silicate?
a framework of tetrahedra with every fourth
silicon replaced with an aluminum ion?
a framework with every other Si replaced
with an Al?
Silicate Minerals: Examples
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E.g., Pyroxenes (Group of
minerals)
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Single Chain Silicate structure
bonded with Fe, Mg, Ca, and Al
Found in Oceanic Crust
Fe/Mg/Ca rich
Silica poor
Single Chain Silicates
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E.g., Pyroxenes (SiO3)
Silicate Minerals: Examples
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E.g., Amphiboles (Group of
minerals)
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Double Chain Silicate structure
bonded with Fe, Mg, Ca, and Al
Found in Continental Crust
More silica and less iron than
pyroxenes
Double Chain Silicates
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E.g., Amphiboles (Si8O22)
Silicate Minerals: Examples
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E.g., Micas (Muscovite and Biotite)
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Sheet Silicate structure
bonded with Al, K,
(biotite has Fe, Mg)
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Found in Continental Crust
More silica and less iron than
Amphiboles
E.g., Clays (Mineral Group)
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Hydrated, sheet silicates from
weathering of other silicates
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Sheet Silicates
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E.g., Micas (Biotite and Muscovite) (AlSi3O10)
Fig. 3-12a, p. 65
Silicate Minerals
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E.g., Feldspars (Orthoclase
and Plagioclase) and Quartz
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Framework Silicate
bonded with Al, and
K (orthoclase) or Na-Ca (plagioclase)
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Found in Continental Crust
More silica than micas,
no iron
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Granite
Orthoclase
Quartz
Framework Silicates
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E.g., Quartz (SiO2) and Feldspars (AlSi3O8)
Framework Silicates
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E.g., Quartz (SiO2) and Feldspar (AlSi3O10)
Fig. 3-12b, p. 65