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)