GEOL: CHAPTER 3 Minerals: The Building Blocks of Rocks
Dec 20, 2015
GEOL: CHAPTER 3
Minerals: The Building Blocks of Rocks
Cluster of crocoite crystals, a rare and brightly colored lead chromate mineral (Smithsonian Museum).
LO1: Define matterLO2: Explore the world of mineralsLO3: Identify mineral groups recognized by
geologistsLO4: Identify physical properties of mineralsLO5: Recognize rock-forming mineralsLO6: Explain how minerals formLO7: Recognize natural resources and
reserves
Learning Outcomes
• Naturally occurring
• Inorganic*
• Crystalline solid
• Narrowly defined chemical composition
• Characteristic physical properties
Mineral Definition
• Fertilizers
• Feed supplements
• Economic well-being
• Affects foreign relations
• Building blocks of rocks
Minerals Are Important
• Liquid
• Gas
• Solid
• Plasma
Four States of Matter
• Comprise elements
• Nucleus with protons and neutrons
• Electrons in electron shells
• Atomic number– Number of protons
• Atomic mass number– Isotopes
Atoms
Fig. 3-3, p. 49
Stepped Art
6 p8 n
14C (Carbon 14)13C (Carbon 13)
6 p7 n
Nucleus
6 p6 n
12C (Carbon 12)
Isotopes of an atom have a different number of neutrons…
• Ionic bonds
• Covalent bonds
• Metallic bonds
• Van der Waals bonds
Types of Bonds
• Transfer of electrons
• Electron shell completion
• Ions either positive or negative
• Opposite charges attract
• Ionic compounds
Ionic Bonding
Fig. 3-4a, p. 50
Stepped Art
Sodiumatom11 p+ 11 e–
Sodiumion
11 p+ 10 e–
+
Chlorineion
17 p+ 18 e–
–
electron transfer
Chlorineatom17 p+ 17 e–
• 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
Covalent Bonding
• Electrons in some metals are mobile and shift from one atom to another
• Metallic luster
• Good conductors of electricity and heat
• Easily reshaped
Metallic Bonding
• Electrically neutral atoms and molecules
• Weak attractive forces
• Graphite and pencils
Van der Waals Bonding
• Inorganic
• Naturally occurring
• Crystalline solid
• Narrowly defined chemical composition
• Characteristic physical properties
Mineral Definition
• Crystals have regular geometric shape– Planar surfaces/crystal faces– Sharp corners– Straight edges
• Cleavage
• Constancy of interfacial angles
Mineral Crystals
A few varieties of crystalline forms
Common elements in Earth’s crust
• 3500+ minerals
• 2 dozen common minerals
• Mineral groups share same negatively charged ion or radical
Mineral Groups
• Silicon and oxygen are common elements
• 95% of Earth’s crust
• Silica tetrahedra– Chains– Continuous sheets– Three-dimensional networks
Silicate Minerals
• Contain iron (Fe), Magnesium (Mg), or both
• Usually dark• Dense• Olivine• Pyroxenes• Amphiboles• Biotite
Ferromagnesian Silicates
• No iron or magnesium
• Lighter colored
• Less dense
• Potassium feldspars
• Plagioclase feldspars
• Quartz
Nonferromagnesian Silicates
• Carbonate radical (CO3)-2
• Calcium carbonate, calcite, aragonite
• Limestone
• Dolomite
Carbonate Minerals
• Oxides
• Native elements
• Phosphates
• Sulfates
• Sulfides
• Halides
Other Mineral Groups
• 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
• Cleavage– Quality– Direction– Angles of intersection
• Fracture– Breakage along irregular surfaces
Physical Properties of Minerals, cont.
Several Types of Mineral Cleavage.
Cross section
Fig. 3-15, p. 60
Stepped ArtHornblende crystal and cross sectionof crystal showing cleavage.
Cross section
Augite crystal and cross sectionof crystal showing cleavage.
124°56°
93°87°
• Hardness
• Specific gravity– Ratio of mineral weight to equal volume of
water at 4ºC
• Feel
• Taste
Physical Properties of Minerals, cont.
Mohs scale of
hardness
talc
apatite
corundum
• Magnetic or not
• Plasticity: ability to bend
• Double refraction
• Chemical tests: acid on calcite
Physical Properties of Minerals, cont.
1. Cooling of magma2. Cooling of lava3. Combination of minerals in seawater or
lakes4. Organisms construct carbonate shells5. Chemical processes change composition
or mineral structure6. Metamorphism: heat, pressure,
chemically active fluids
How Minerals Form
• Natural resource: form and concentration that is economically feasible– Minerals– Rocks– Liquid petroleum– Natural gas
Natural Resources
• 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
Reserves