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Minerals: The Building Blocks of Rocks
GEOL: CHAPTER 3 Minerals: The Building Blocks of Rocks
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Cluster of crocoite crystals, a rare and brightly colored lead chromate mineral (Smithsonian Museum). Cluster of crocoite crystals, a rare and brightly colored lead chromate mineral (Smithsonian Museum).
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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
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Mineral Definition Naturally occurring Inorganic* Crystalline solid
Narrowly defined chemical composition Characteristic physical properties
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Minerals Are Important
Fertilizers Feed supplements Economic well-being Affects foreign relations Building blocks of rocks
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Four States of Matter Liquid Gas Solid Plasma
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Atoms Comprise elements Nucleus with protons and neutrons
Electrons in electron shells Atomic number Number of protons Atomic mass number Isotopes
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Figure 3.2 Shell Models for Common Atoms The shell model for several atoms and their electron configurations. A blue circle represents the nucleus of each atom, but remember that atomic nuclei are made up of protons and neutrons, as shown in Figure 3.3.
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Isotopes of an atom have a different number of neutrons…
Nucleus 6 p 6 n 12C (Carbon 12) 13C (Carbon 13) 6 p 7 n 6 p 8 n 14C (Carbon 14) Figure 3.3 Carbon Isotopes Schematic representation of the isotopes of carbon. Carbon has an atomic number of 6 and an atomic mass number of 12, 13, or 14, depending on the number of neutrons in its nucleus. Stepped Art Fig. 3-3, p. 49
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Types of Bonds Ionic bonds Covalent bonds Metallic bonds
Van der Waals bonds
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Ionic Bonding Transfer of electrons Electron shell completion
Ions either positive or negative Opposite charges attract Ionic compounds
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Figure 3.4 Ionic Bond to Form the Mineral Halite (NaCl)
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+ – electron transfer Sodium atom 11 p+ 11 e– Chlorine atom 17 p+
ion 11 p+ 10 e– + Chlorine ion 17 p+ 18 e– – Figure 3.4 Ionic Bond to Form the Mineral Halite (NaCl) Stepped Art Fig. 3-4a, p. 50
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Figure 3.4 Ionic Bond to Form the Mineral Halite (NaCl)
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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
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Figure 3.5 Covalent Bonds
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Figure 3.5 Covalent Bonds
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Figure 3.5 Covalent Bonds
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Figure 3.5 Covalent Bonds
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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
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Van der Waals Bonding Electrically neutral atoms and molecules
Weak attractive forces Graphite and pencils
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Mineral Definition Inorganic Naturally occurring Crystalline solid
Narrowly defined chemical composition Characteristic physical properties
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Mineral Crystals Crystals have regular geometric shape Cleavage
Planar surfaces/crystal faces Sharp corners Straight edges Cleavage Constancy of interfacial angles
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A few varieties of crystalline forms
Figure 3.6 A Variety of Mineral Crystal Shapes
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Figure 3.6 A Variety of Mineral Crystal Shapes
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Figure 3.6 A Variety of Mineral Crystal Shapes
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Figure 3.6 A Variety of Mineral Crystal Shapes
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Figure 3.6 A Variety of Mineral Crystal Shapes
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Figure 3.7 Sizes and Charges of Ions Electrical charges and relative sizes of ions common in minerals. The numbers within the ions are the radii shown in Ångstrom units.
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Common elements in Earth’s crust
Figure 3.8 Common Elements in Earth’s Crust
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Figure 3.8 Common Elements in Earth’s Crust
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Figure 3.8 Common Elements in Earth’s Crust
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Mineral Groups 3500+ minerals 2 dozen common minerals
Mineral groups share same negatively charged ion or radical
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Figure 3.9 Radicals Many minerals contain radicals, which are complex groups of atoms tightly bonded together. The silica and carbonate radicals are particularly common in many minerals, such as quartz (SiO2) and calcite (CaCO3).
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Silicate Minerals Silicon and oxygen are common elements
95% of Earth’s crust Silica tetrahedra Chains Continuous sheets Three-dimensional networks
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Figure 3.10 The Silica Tetrahedron and Silicate Materials
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Figure 3.10 The Silica Tetrahedron and Silicate Materials
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Figure 3.10 The Silica Tetrahedron and Silicate Materials
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Figure 3.10 The Silica Tetrahedron and Silicate Materials
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Ferromagnesian Silicates
Contain iron (Fe), Magnesium (Mg), or both Usually dark Dense Olivine Pyroxenes Amphiboles Biotite
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Figure 3.11 Common Silicate Materials
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Nonferromagnesian Silicates
No iron or magnesium Lighter colored Less dense Potassium feldspars Plagioclase feldspars Quartz
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Figure 3.11 Common Silicate Materials
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Carbonate Minerals Carbonate radical (CO3)-2
Calcium carbonate, calcite, aragonite Limestone Dolomite
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Other Mineral Groups Oxides Native elements Phosphates Sulfates
Sulfides Halides
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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
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Figure 3.13 Mineral Crystals
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Figure 3.13 Mineral Crystals
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Figure 3.13 Mineral Crystals
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Physical Properties of Minerals, cont.
Cleavage Quality Direction Angles of intersection Fracture Breakage along irregular surfaces
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Several Types of Mineral Cleavage.
Figure 3.14 Several Types of Mineral Cleavage
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Figure 3.14 Several Types of Mineral Cleavage
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Figure 3.14 Several Types of Mineral Cleavage
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Augite crystal and cross section of crystal showing cleavage.
93° 87° Augite crystal and cross section of crystal showing cleavage. Cross section Figure 3.15 Cleavage in Augite and Hornblende 124° 56° Hornblende crystal and cross section of crystal showing cleavage. Stepped Art Fig. 3-15, p. 60
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Physical Properties of Minerals, cont.
Hardness Specific gravity Ratio of mineral weight to equal volume of water at 4ºC Feel Taste
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Mohs scale of hardness talc apatite corundum
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Physical Properties of Minerals, cont.
Magnetic or not Plasticity: ability to bend Double refraction Chemical tests: acid on calcite
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Figure 3.16 Minerals in GraniteThe igneous rock granite (see Chapter 4) is made up of mostly three minerals—quartz, potassium feldspar, and plagioclase feldspar—but it may also contain small amounts of biotite, muscovite, and hornblende.
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How Minerals Form Cooling of magma Cooling of lava
Combination of minerals in seawater or lakes Organisms construct carbonate shells Chemical processes change composition or mineral structure Metamorphism: heat, pressure, chemically active fluids
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Natural Resources Natural resource: form and concentration that is economically feasible Minerals Rocks Liquid petroleum Natural gas
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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
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