Download GEOL 1e Lecture Outlines

GEOL: CHAPTER 3
Minerals: The Building
Blocks of Rocks
Cluster of crocoite crystals, a rare and brightly colored lead
chromate mineral (Smithsonian Museum).
Learning Outcomes
LO1: Define matter
LO2: Explore the world of minerals
LO3: Identify mineral groups recognized by
geologists
LO4: Identify physical properties of minerals
LO5: Recognize rock-forming minerals
LO6: Explain how minerals form
LO7: Recognize natural resources and
reserves
Mineral Definition
•
•
•
•
•
Naturally occurring
Inorganic*
Crystalline solid
Narrowly defined chemical composition
Characteristic physical properties
Minerals Are Important
•
•
•
•
•
Fertilizers
Feed supplements
Economic well-being
Affects foreign relations
Building blocks of rocks
Four States of Matter
•
•
•
•
Liquid
Gas
Solid
Plasma
Atoms
•
•
•
•
Comprise elements
Nucleus with protons and neutrons
Electrons in electron shells
Atomic number
– Number of protons
• Atomic mass number
– Isotopes
Isotopes of an atom have a different number of neutrons…
Nucleus
6p
6n
12C
(Carbon 12)
6p
7n
13C
(Carbon 13)
6p
8n
14C
(Carbon 14)
Stepped Art
Fig. 3-3, p. 49
Types of Bonds
•
•
•
•
Ionic bonds
Covalent bonds
Metallic bonds
Van der Waals bonds
Ionic Bonding
•
•
•
•
•
Transfer of electrons
Electron shell completion
Ions either positive or negative
Opposite charges attract
Ionic compounds
electron transfer
Sodium
atom
11 p+
11 e–
Chlorine
atom
17 p+
17 e–
Sodium
ion
11 p+
10 e–
Chlorine
ion
17 p+
18 e–
+
–
Stepped Art
Fig. 3-4a, p. 50
Covalent Bonding
•
•
•
•
Sharing of electrons
Electron shell completion
Electron shells overlap
Carbon needs 4 electrons, so forms four
covalent bonds
• Silicates: Silicon bonds with oxygen are
part covalent, part ionic
Metallic Bonding
• Electrons in some metals are mobile and
shift from one atom to another
• Metallic luster
• Good conductors of electricity and heat
• Easily reshaped
Van der Waals Bonding
• Electrically neutral atoms and molecules
• Weak attractive forces
• Graphite and pencils
Mineral Definition
•
•
•
•
•
Inorganic
Naturally occurring
Crystalline solid
Narrowly defined chemical composition
Characteristic physical properties
Mineral Crystals
• Crystals have regular geometric shape
– Planar surfaces/crystal faces
– Sharp corners
– Straight edges
• Cleavage
• Constancy of interfacial angles
A few varieties of crystalline forms
Common elements in Earth’s crust
Mineral Groups
• 3500+ minerals
• 2 dozen common minerals
• Mineral groups share same negatively
charged ion or radical
Silicate Minerals
• Silicon and oxygen are common elements
• 95% of Earth’s crust
• Silica tetrahedra
– Chains
– Continuous sheets
– Three-dimensional networks
Ferromagnesian Silicates
• Contain iron (Fe), Magnesium (Mg),
or both
• Usually dark
• Dense
• Olivine
• Pyroxenes
• Amphiboles
• Biotite
Nonferromagnesian Silicates
•
•
•
•
•
•
No iron or magnesium
Lighter colored
Less dense
Potassium feldspars
Plagioclase feldspars
Quartz
Carbonate Minerals
•
•
•
•
Carbonate radical (CO3)-2
Calcium carbonate, calcite, aragonite
Limestone
Dolomite
Other Mineral Groups
•
•
•
•
•
•
Oxides
Native elements
Phosphates
Sulfates
Sulfides
Halides
Physical Properties of Minerals
• Luster
– Quality and intensity of light reflected from
surface
• Color
• Crystal form
– Number of sides
– Different minerals can have the same form
Physical Properties of Minerals,
cont.
• Cleavage
– Quality
– Direction
– Angles of intersection
• Fracture
– Breakage along irregular surfaces
Several Types of
Mineral Cleavage.
Cross section
93°
87°
Augite crystal and cross section
of crystal showing cleavage.
Cross section
56°
124°
Hornblende crystal and cross section
of crystal showing cleavage.
Stepped Art
Fig. 3-15, p. 60
Physical Properties of Minerals,
cont.
• Hardness
• Specific gravity
– Ratio of mineral weight to equal volume of
water at 4ºC
• Feel
• Taste
Mohs scale
of
hardness
talc
apatite
corundum
Physical Properties of Minerals,
cont.
•
•
•
•
Magnetic or not
Plasticity: ability to bend
Double refraction
Chemical tests: acid on calcite
How Minerals Form
1. Cooling of magma
2. Cooling of lava
3. Combination of minerals in seawater or
lakes
4. Organisms construct carbonate shells
5. Chemical processes change composition
or mineral structure
6. Metamorphism: heat, pressure,
chemically active fluids
Natural Resources
• Natural resource: form and concentration
that is economically feasible
– Minerals
– Rocks
– Liquid petroleum
– Natural gas
Reserves
• Part of resource that is known and can be
recovered at economically feasible cost
• What makes a reserve a resource:
– Transportation costs
– Labor costs
– Market price
– Technology changes