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

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

Nucleus

Protons



Neutrons




+ Charge
Has Mass, Atomic #
0 Charge
Mass same as One Proton
Atomic Mass #
Electrons



In shells (2, 8, 8…)
- charge (balances each
proton +)
Very little Mass
Electron
Shells
Ions


Incomplete electron
shells tend to be filled
E.g. Chlorine (Cl-)




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

Other Common
Examples
Sodium

Sodium, at.# 11
{2, 8, 1}  Na+ (Cation)

Oxygen, at.# 8
{2,6},  O-2

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
B. Introduction to Minerals

Halite (Rock Salt)




Mineral mined for rock
salt and table salt
Na gives electron to Cl
Opposites attract,
elements bond
NaCl (Sodium Chloride)
*
Intro to Minerals



Repeating 3-D pattern
forms a Crystalline Solid
(or Crystal)
Naturally occurring
Crystal Form
crystals are Minerals
Crystalline structure and
bonding leads to physical
properties: hardness,
crystal form, cleavage
specific gravity (density)
(pg. 38-43)
3 planes of cleavage
*
Some Familiar Crystal Forms

Quartz Crystal
(SiO2)
Fig. 2.15a

Snow Flake (Ice Crystal) due
to crystalline structure of H2O
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
Silica Tetrahedra

The building block of
most common rock
forming minerals




Four O2- in a tetrahedral
configuration
One Si4+ nested in the
center
(4  -2) +4 = -4
(SiO4)-4
-4
Definition of Mineral




Naturally Occurring
Crystalline
Solid
With a definite chemical
composition


A unique composition
or
A definite range of compositions
Mineral Group, e.g. Olivine
C. Silica Tetrahedra and Silicate
Minerals



*
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
*
Silicate Minerals: Examples
E.g., Olivine

Isolated silicate
structure
(SiO4)-4 + 2×Fe+2
Fe2SiO4

Fe Mg SiO4

Mg2SiO4



Definite Range

(Fe,Mg) 2 SiO4  Olivine Mineral Group
Silicate Minerals: Examples

E.g., Olivine





*
Isolated silicate
structure
bonded with iron
and magnesium
Makes up much
of the mantle
Fe/Mg rich >50%
Silica poor <45%
Silicate Minerals: Examples

E.g., Pyroxenes (Mineral Group)

Single Chain Silicate structure
(SiO3)-2 + Fe+2
FeSiO3

(Fe,Mg) SiO3


MgSiO3
(Fe,Mg) SiO3  Pyroxene



Mineral Group
Ferromagnesian
Silicate Minerals: Examples

E.g., Pyroxenes (Group of
minerals)





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

What is the net charge of:


a silica tetrahedron?
a single chain of single
tetrahedra?
*Hint: a shared apex is ½ an Oxygen
Building Silicates

What is the net charge of:







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

What common elements would balance
the charges of :







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

E.g., Pyroxenes (Group of
minerals)





*
Single Chain Silicate structure
bonded with Fe, Mg, Ca, and Al
Found in Oceanic Crust
Fe/Mg/Ca rich
Silica poor
Single Chain Silicates

E.g., Pyroxenes (SiO3)
Silicate Minerals: Examples

E.g., Amphiboles (Group of
minerals)




*
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

E.g., Amphiboles (Si8O22)
Silicate Minerals: Examples

E.g., Micas (Muscovite and Biotite)


Sheet Silicate structure
bonded with Al, K,
(biotite has Fe, Mg)



Found in Continental Crust
More silica and less iron than
Amphiboles
E.g., Clays (Mineral Group)

Hydrated, sheet silicates from
weathering of other silicates
*
Sheet Silicates

E.g., Micas (Biotite and Muscovite) (AlSi3O10)
Silicate Minerals

E.g., Feldspars (Orthoclase
and Plagioclase) and Quartz


Framework Silicate
bonded with Al, and
K (orthoclase) or Na-Ca (plagioclase)


Found in Continental Crust
More silica than micas,
no iron
*
Granite
Orthoclase
Quartz
Framework Silicates

E.g., Quartz (SiO2) and Feldspars (AlSi3O8)
Framework Silicates

E.g., Quartz (SiO2) and Feldspar (AlSi3O10)