Transcript Minerals

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 minerals)
 C. The silicate minerals (7)
 D. Other important rock-forming minerals (4)
 E. Mineral properties
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Quartz
Biotite
Feldspar
A. Changing Scale: Zooming in from global view to atomic scale
The crust is made of rocks > Rocks are made of minerals > …
Rocks 
Minerals
Atoms
Fig. 2.7
Fig. 2.1
 Fig. 2.3
 Fig. 2.15
Biotite
Quartz
Fig. 2.17a
 Fig. 2.19
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Feldspar
The Elements of the Crust
and Where They are Found
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O and Si make up most of the earth’s crust
Crustal
Crustal
Change in
(including oceanic)
Whole Earth
crust due to
(proto-earth)
differentiation
O, Si, Al, Na Percentage
and K are more abundant in the
30
Incr. 
Continental Crust
15
Incr. 
<1
Incr. 
Fe, Mg, and Ca 35are much more
Dcr.  abundant in the
<1
Incr. 
Oceanic Crust <1
Incr. 
<1
Incr. 
Fe and Mg make
up
more
than
10
Dcr.  half of the Mantle
~8
• O and Si make up most of the earth’s crust (including oceanic)
• O, Si, Al, Na and K are more abundant in the Continental Crust
• Fe, Mg, and Ca are much more abundant in the Oceanic Crust
• Fe and Mg make up more than half of the Mantle
Atoms and Elements
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Nucleus
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Protons
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Neutrons
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+ Charge
Has Mass, Atomic #
0 Charge
Mass similar to One Proton
Atomic Mass #
Electrons
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In shells (2, 8, 8…)
- charge (balances each
proton +)
Very little Mass
Ions and Bonding
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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 and Bonding (cont.)
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Other Common
Examples
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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
Fig. 2.5
Fig. 2.3
Oxygen (O-2)
B. Introduction to Minerals
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Halite
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Mineral mined for rock
salt and table salt
Na gives electron to Cl
Opposites attract,
elements bond
NaCl (Sodium Chloride)
Intro to Minerals
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Fig. 2.18
Fig. 2.20
Repeating 3-D pattern
forms a Crystalline Solid
(or Crystal)
Naturally occurring
Crystal Form
(Habit)
crystals are Minerals
Crystalline structure and
bonding leads to physical
properties: hardness,
crystal form, cleavage
specific gravity (density)
3 planes of cleavage
Some Familiar Crystal Forms
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Quartz Crystal
(SiO2)
Fig. 2.15a
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Snow Flake (Ice Crystal) due
to crystalline structure of H2O
Definition: Mineral
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a. Crystalline solid
b. Naturally Occurring
(not artificial)
c. Definite chemical
composition
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some unique
Many with a definite
range of composition
(mineral groups)
C. Silicate Minerals
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Silica: The chemical compound of Silicon
and Oxygen
Oxygen and Silicon are the most abundant
elements in the earth’s crust, thus
Silicate Minerals are a class of minerals
that comprise most (>90%) of the crust
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Continental Crust is higher in silica
Oceanic Crust is lower in silica
Silica Tetrahedra and
Silicate Minerals
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One Si and Four O s
bond in a tetrahedron
shape
The silica
tetrahedron is the
basic building block
of most minerals of
the crust
Silica tetrahedra bond
with other tetrahedra
by sharing Oxygens
Other cations bond to
form a wide variety of
Silicate Minerals
SiO3-2
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Fig. 2.7
Fig. 2.8
Fig. 2.11
Silicate Minerals (cont.)
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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% [2:7]
Silica poor <45% [1:7]
Fe2(SiO4) to Mg2(SiO4)
Ferromagnesian Mineral
[2:7] Numbers in Square Brackets are atomic ratios.
E.g. 2 atoms Fe to total number of atoms
Silicate Minerals (cont.)
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E.g., Pyroxene (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 [1:5]
Silica poor
[1:5]
X SiO3 X = Fe+2,Mg+2, Ca+2, and Al
Also a Ferromagnesian Mineral
Cleavage and
Form Prismatic
SiO3-2
Silicate Minerals
Other Important examples
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Olivine: most of mantle
Pyroxene: Oceanic Crust*
Amphibole: Continental Crust
Micas: Biotite, Muscovite
continental crust
Clay: In many soils
Na and K Feldspar: Continental
Crust
Ca Feldspar: Oceanic Crust*
Quartz: Continental Crust and
many soils
Silicate
Structure
Example
Isolated
Silicate
Structure
Olivine
Single Chain
Structure
Pyroxene
Group
Double Chain
Structure
Amphibole
Group
Mica
Group
Sheet
Structure
Framework
Structure
Clay
Group
Quartz
Feldspar
Group
Ratio of Tot. Atoms to
:Iron
:Silicon
Olivine
1:3½ 1:7
Systematic Silicate
Mineralogy
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Pyroxene
Fig. 2.9
1:5
Group
From bottom to
top
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Decreasing Increasing
Silica
Fe/Mg/Ca
Increasing
Density
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Amphibole
Group
1:5
<1:35 1:41/3
Increasing
Fe/Mg/Ca
Decreasing silica
Mica
Group
Increasing density <1:40 1:4
Darker minerals
Quartz
K and Na Feldspar
Ca Feldspar
(0) 1:3
(0) 1:41/3
(0) 1:6 ½
Systematic Silicate
Mineralogy
Olivine
Mantle
Pyroxene
Group
 Fig. 2.9
Oceanic
#
 Crust
From
bottom
Increasing
Melting and crystallizing
Temperature~
top
Fe/Mg/Ca
Density
Weathering*
Decreasing
~Quartz
melts first
*All of these
silicates weather to
form Clay Minerals
Except quartz
to
Amphibole
Group
Increasing
Fe/Mg/Ca
 Decreasing silica
Mica
Group
 Increasing density
 Darker minerals
Cont.
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Crust
Quartz
K and Na Feldspar
Ca Feldspar#
Other Important
Rock-Forming
Minerals
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Sediments and Sedimentary Rocks
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Quartz: resistant to alteration by weathering
Clay: most other silicates weather to clay
Carbonates (non-silicates): Deposited in
shallow tropical seas be shellfish and coral
Calcite: CaCO3
 Dolomite: CaMgCO3
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Halite: Deposited by evaporating seas
Single Element Minerals: Diamond, Graphite,
Gold, sulfur