PowerPoint Presentation MInerals

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Minerals
Minerals
Building blocks of nearly all rocks
Definition
naturally occurring
excludes synthetic minerals
inorganic
non living processes form them
chemically specific
has a unique proportion of elements
crystalline solid
atoms are arranged in specific 3-D patterns
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Periodic Table of Elements
Increasing number of protons, neutrons and
electrons
Increasing valence levels

table 2-2, p. 23
Atomic numbers 1 - 92 occur naturally on Earth
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Ions
Ions
atoms or groups of atoms that have an electrical
atoms or groups of atoms that have an electrical




charge due variable numbers of electrons
results from gaining or losing electrons
results from gaining or losing electrons
-

-

Anion
Anion




negatively charged atom
negatively charged atom
-

-

e.g. Cl, O
,
e.g. Cl, O
,
-

-

2
2
Cation
Cation




positively charged
positively charged
-

-

e.g. Na, K, Fe

e.g. Na, K, Fe

-

-

2
2




Ion Complex
a group of atoms that behave as a unit
a group of atoms with a charge
-

-

2-
e.g., SO
e.g. SO
, CO
-

-

4
4
4
Chemical Bonds- control many physical properties
Covalent
Covalent




Atoms
share
their outer-most electrons with another atom
Atoms
share
their outer-most electrons with another atom
-

-

Very strong bond
Very strong bond
-

-

Ionic
Ionic




Atoms get rid of electrons from their outer-most
shell.
Atoms get rid of electrons from their outer-most
shell.
-

-

results in a charged ( or -) atom
results in a charged ( or -) atom
-

-

not as strong as above
not as strong as above
-

-

Metallic
Metallic




A sea of electrons surrounding nuclei
A sea of electrons surrounding nuclei
-

-

Electrons freely exchanged among atoms
Electrons freely exchanged among atoms
-

-

Metals make good conductors!
Metals make good conductors!
-

-

can be strong
can be strong
-

-

Van der Waals
Van der Waals




electrostatic charge
electrostatic charge
-

-

weak bond
weak bond
-

-

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Carbon Different chemical bond types result in
different minerals with different properties,
despite being composed of the same element
This happens because of the crystalline
structure i.e., the 3D arrangement of atoms
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Color Easiest to identify Can be diagnostic
(e.g., azurite bright blue) But commonly
misleading due to extreme variability
impurities in between crystalline structure
impurities incorporated into the crystalline
structure Examples in Quartz
green
blue
yellow (citrine)
pink (Rose)
brown (Smoky)
purple (Amethyst)
clear (Rock crystal)
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Moh's Relative Hardness Scale Controls how
resistant rocks are to erosion
Moh's Relative Hardness Scale
1

T
alc- (softest)
1

T
alc- (softest)
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F
eldspar
6

F
eldspar
exas
exas
gt

T
gt

T
F
or
6.0 steel file /nail
F
or

gt


gt

2

G
ypsum
2

G
ypsum
7

Q
uartz
2.5 fingernail
7

Q
uartz
G
uys)
irls (or
G
uys)
gt

G
irls (or
gt

G
Q
uarters
Q
uarters

gt


gt

3

C
alcite
3

C
alcite
8

T
opaz
8

T
opaz
3.5 copper penny
an
an
gt

C
gt

C
T
hey
T
hey

gt


gt

4

F
luorite
4

F
luorite
9

C
orundum
9

C
orundum
lirt
lirt
gt

F
gt

F
C
an
C
an

gt


gt

5

A
patite
5

A
patite
10

D
iamond- (hardest)
10

D
iamond- (hardest)
nd
nd
gt

A
gt

A
D
ance
D
ance

gt


gt

5.5 plate glass
These items can be slightly harder or softer
depending on how they were made, and what is in
them
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Physical properties continued Cleavage vs
Fracture vs Crystal shape all related to
chemical elements and types of bonds Cleavage -
the tendency to break along a plane typically a
zone of weak chemical bonds Fracture - the
tendency to break in non-planar surfaces most
notable is conchoidal fracture- curved conical
shapes common in quartz Crystal habit- the 3
dimensional shape of minerals as they grow- can
be quite spectacular and diagnostic
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Crystal shapes
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Fracture
The mineral Quartz, as well as some kinds of
rocks, exhibits this unique kind of fracture
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Other physical properties Streak- the color of
the powdered mineral against a white
background Luster- the outer appearance- e.g.
metallic, and non-metallic such as vitreous
(adamantine), resinous, dull, greasy, pearly,
silky. Special properties taste, smell,
reactivity to acids (HCl), magnetism, pleochro
ism feel Density- the weight per unit volume- a
measure of how closely packed the atoms are
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Mineral Classes
Mineral Classes (12)
Silicates- Silicon-oxide Ion (Si O )




x
x
Quartz (SiO2), Feldspar, Biotite, Muscovite
Quartz, Feldspar, Biotite, Muscovite
-

-

Oxides- Oxygen (O )




x
Hematite (Fe2O3), Magnetite (Fe2O4)
Hematite, Magnetite
-

-

2-
Carbonates- Carbonate anion (CO )






3
Calcite (CaCO3), Dolomite, Malachite
(Cu2(CO3)(OH)2)
-

2-

Sulfates- Sulfate anion (SO )






4


Gypsum (CaSO4) 2(H2O), Anhydrite,
Barite
-


Sulfides- Sulfur (S) anion

-
Galena (PbS), Cuprite (CuS), Sphalerite ((Zn,Fe)S)
Native elements- Pure element
Native elements- Pure element
-

Gold (Au), Silver (Ag), Copper (Cu), Sulfur (S)
Gold, Silver, Copper, Sulfer
-

Halides- contain F, Cl, Br, I anions
Halides- F, Cl, Br, I




Halite (NaCl), Sylvite (KCl), Fluorite (CaF2)
Halite, Sylvite, Fluorite
-

-

- variable number of the element
- variable number of the element
x
x
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Importance as Rock Builders
Importance as Rock Builders

All rocks are composed of Minerals.

All rocks are composed of Minerals.

12 minerals are considered common.

12 or so are considered common.
Olivine, Augite, Hornblende, Biotite
Olivine, Augite, Hornblende, Biotite
gt

gt

darker colors- Green, Blue, Black, Brown
darker colors- Green, Blue, Black, Brown
-

-

Quartz,
Quartz,
gt

gt

gt
Orthoclase feldspar, Plagioclase feldspars
gt
gt
Muscovite, Calcite, Dolomite, Gypsum, Halite
gt
Muscovite, Calcite, Dolomite, Gypsum, Halite
lighter colors- Pink, White, Yellow, Gray, Clear
lighter colors- Pink, White, Yellow, Gray, Clear
-

-

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Fe, Mg-rich Silicates
Hornblende
Olivine
Augite
Biotite mica
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Quartz Al-rich Silicates
Quartz
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Carbonates
White calcite CaCO3- note rhombohedral cleavage
in all three samples
Optical Calcite- CaCO3 shows double refraction.
Dolomite CaMg(CO3)2 rhombohedral crystal
Calcite- CaCO3 shows double refraction.
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Sulfides, Sulfates Halides
Galena
PbS
Alabaster
HaliteNaCl
Satin spar
Selenite
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Importance as rock builders
Building blocks of all rocks are minerals

Some minerals form as molten rock cools

Some minerals form as chemical precipitates

Some are produced by chemical reactions
(weathering)

Some are manufactured by living things

Biotite mineral grain
Biotite mineral grain
Feldspar
Feldspar
mineral
mineral
grain
grain
Quartz mineral
Quartz mineral
grain
grain