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Chapter 1 Minerals: Building Blocks of Rocks
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Minerals: Building Blocks of Rocks
By definition a mineral is/has Naturally occurring Inorganic solid Ordered internal molecular structure Definite chemical composition
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Where do minerals form Plate boundaries = Igneous and Metamorphic
Oceans and water = Sedimentary minerals
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Where do minerals form Magma Slow cooling = large crystals
Fast cooling = small crystals
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Where do minerals form Sedimentary Precipitation of minerals
from water
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Where do minerals form Metamorphic Minerals
Heating and recrystallization of existing rocks
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Rocks are an aggregate of minerals
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Composition and Structure of Minerals
Atoms Elements Minerals Rocks
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Composition and Structure of Minerals
Elements Basic building blocks of minerals Over 100 are known (92 naturally occurring) Atoms Smallest particles of matter Retain all the characteristics of an element
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Composition and Structure of Minerals
Atomic structure Central region called the nucleus Consists of protons (+ charges) and neutrons (- charges) Electrons Negatively charged particles that surround the nucleus Located in discrete energy levels called shells
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Structure of an Atom
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Fig. 7.5
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Structure of an Atom
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Ionic Bonding – Transfer of Electronics
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Covalent Bonding – Sharing of Electronics
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Composition and Structure of Minerals
Chemical bonding Formation of a compound by combining two or more elements Atoms gain or lose outermost electrons to form ions Oppositely charged ions attract one another to produce a neutral chemical compound
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Composition and Structure of Minerals
Isotopes and radioactive decay Mass number = sum of neutrons + protons in an atom Isotope = atom that exhibits variation in its mass number Unstable isotopes emit particles and energy in a process known as radioactive decay
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Earth Composition Earth Consists of the Core, Mantle, and Crust
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Elemental Abundances in Continental Crust
Figure 1.14
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Elemental Abundances Earth as a whole vs Crust
Oxygen 35% Iron 24% Silicon 17% Magnesium 14% Sulfur 6% Aluminum 1% Calcium 1% Oxygen 47% Iron 5.5% Silicon 27% Magnesium 2.1% Sulfur <1% Aluminum 8% Calcium 3.7%
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Mineral Identification - Crystal Form
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A Garnet Crystal
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Cubic Crystals of Pyrite
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Minerals - Crystals
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Physical Properties of Minerals
Luster Appearance of a mineral in reflected light Two basic categories Metallic Nonmetallic Other descriptive terms include vitreous, silky, or earthy
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Galena (PbS) Displays Metallic Luster
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Physical Properties of Minerals
Color Generally unreliable for mineral identification Often highly variable due to slight changes in mineral chemistry Exotic colorations of certain minerals produce gemstones
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Quartz (SiO2) Exhibits a Variety of Colors
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Physical Properties of Minerals
Streak Color of a mineral in its powdered form Hardness Resistance of a mineral to abrasion or scratching All minerals are compared to a standard scale called the Mohs scale of hardness
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Streak Is Obtained on an Unglazed Porcelain Plate
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Mohs Scale of Hardness
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Diamonds
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Mohs Scale of Hardness Atom Arrangement
Diamond Graphite
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Physical Properties of Minerals
Cleavage Tendency to break along planes of weak bonding Produces flat, shiny surfaces Described by resulting geometric shapes Number of planes Angles between adjacent planes
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Fluorite, Halite, and Calcite All Exhibit Perfect Cleavage
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Fig f
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Fig d
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Fig a
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Physical Properties of Minerals
Fracture Absence of cleavage when a mineral is broken Specific Gravity Weight of a mineral/weight of an equal volume of water Average value = 2.5 – 3.0
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Conchoidal Fracture
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Physical Properties of Minerals
Other properties Magnetism Reaction to hydrochloric acid Malleability Double refraction Taste Smell Elasticity
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Mineral??????? Quartz Yes No Coal Yes No Pearls Yes No Amethyst Yes No
Shells Yes No Water Yes No Ice Yes No Iron Yes No
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Mineral??????? Quartz Yes No Coal Yes No Pearls Yes No Amethyst Yes No
Shells Yes No Water Yes No Ice Yes No Iron Yes No
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Mineral Groups Nearly 4000 minerals have been named
Rock-forming minerals Common minerals that make up most of the rocks of Earth’s crust Only a few dozen members Composed mainly of the 8 elements that make up over 98% of the continental crust
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Mineral Groups Silicates Most important mineral group
Comprise most rock-forming minerals Very abundant due to large % of silicon and oxygen in Earth’s crust Silicon-oxygen tetrahedron Fundamental building block Four oxygen ions surrounding a much smaller silicon ion
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Mineral Groups Common silicate minerals Feldspar group Quartz
Most common mineral group Quartz Only common silicate composed entirely of oxygen and silicon
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Two Illustrations of the Si–O Tetrahedron
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Silicate Mineral Structures
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Silicate Mineral Structures
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Silicate Mineral Structures
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Potassium Feldspar
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Mineral Groups Important nonsilicate minerals
Comprise only 8% of Earth’s crust Often occur as constituents in sedimentary rocks
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Mineral Groups Important nonsilicate minerals Carbonates
Primary constituents in limestone and marble Limestone is used commercially for road paving, building stone, and as the main ingredient in Portland cement
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Mineral Groups Important nonsilicate minerals Halite and gypsum
Both are commonly found in thick layers Like limestone, both halite and gypsum are important nonmetallic resources
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Mineral Groups Important nonsilicate minerals
A number of other minerals have economic value Examples Hematite (oxide mined for iron ore) Sphalerite (sulfide mined for zinc ore) Galena (lead) Native copper (native element mined for copper)
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Native Copper
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Mineral Resources and Reserves
Resources are minerals that can be recovered for use Reserves include mineral deposits already identified that can be profitability extracted Resources include reserves, deposits that can not economically recovered, and minerals not yet discovered
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Florida Production 4th in states for non fuel minerals
Top 3 in the states for crushed stone, cement, and peat 1st in states in heavy mineral sales 1st in world for phosphate production
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Florida Production - Phosphate
90% used for fertilizer 5% for livestock feed supplement 5% used in food products, chemicals and ceramics
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Florida Production – Crushed Stone
Limestone and coquina Used for construction Limestone used for cement
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Florida Production – Clays
Used for absorbents, anti-acids, and whiteners
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Florida Production – Heavy Minerals
Found in Sands Main minerals include ilmenite and rutile – both metamorphic minerals Used as paint pigments, paper, and plastics
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End of Chapter 1
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