Mineral identification 4

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%)