Patterns in Nature: Minerals -...
Transcript of Patterns in Nature: Minerals -...
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 1
Patterns in Nature: MineralsPatterns in Nature: Minerals
January 27, 2005January 27, 2005
© 2003, R
on Parker©
2003, Ron Parker Geosciences 211, Physical Geology © 2005, Ron ParkerGeosciences 211, Physical Geology © 2005, Ron Parker Geosciences 211, Physical Geology © 2005, Ron Parker
Minerals Make up the lithosphere, mantle and the core.
The “building blocks” of rocks.
Over 4000 are known.
Developed societies depend on mineral resources. Metals – Iron, copper, lead, zinc, nickel, aluminum, etc. Non-metals – Gypsum, limestone, aggregate, clay.
Preserve information about conditions of formation.
Make up the lithosphere, mantle and the core.
The “building blocks” of rocks.
Over 4000 are known.
Developed societies depend on mineral resources. Metals – Iron, copper, lead, zinc, nickel, aluminum, etc. Non-metals – Gypsum, limestone, aggregate, clay.
Preserve information about conditions of formation.
Geosciences 211, Physical Geology © 2005, Ron Parker
Mineral Definition Definition of a mineral:
Homogenous (uniform throughout)
Naturally occurring (no synthetics)
Inorganic (no biological)
Solid (no liquids or gases)
Ordered internal molecular structure Definite chemical composition
A solid that exhibits some (but not all) of these properties is a mineraloid.
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Rocks Rocks are earth materials made from minerals. Most rocks have more than one mineral.
Example: Granite Potassium feldspar Quartz Hornblende
Some rocks are monomineralic. Limestone (Calcite) Rock salt (Halite) Glacial Ice ©
2003, Ron Parker
© 2003, R
on Parker
Geosciences 211, Physical Geology © 2005, Ron Parker
Crystalline Structure Disordered atomic arrangement (glass).
Ordered atomic arrangement (mineral).
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A mineral with crystal faces. Faces grow in open spaces. Faces reflect atomic order. Constancy of interfacial angles.
Crystals of the same mineral have the same crystal faces.
The angle between adjacent crystal faces is always the same.
CrystalsQuartz crystal © Jay SchomerQuartz crystal © Jay Schomer
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 2
Geosciences 211, Physical Geology © 2005, Ron Parker
Crystal Lattice The ordered 3-D atomic arrangement (crystal lattice) in minerals
reflects a repeating pattern. This internal pattern results in crystal symmetry.
Geosciences 211, Physical Geology © 2005, Ron Parker
Crystal Lattice The crystal lattice in minerals is revealed by X-Ray Diffraction
(XRD). Measuring lattice spacing by XRD permits mineral identification.
New Earlham Geology X-Ray DiffractometerNew Earlham Geology X-Ray Diffractometer
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on Parker©
2003, Ron Parker
© W. W. Norton© W. W. Norton
Geosciences 211, Physical Geology © 2005, Ron Parker
Minerals with The same chemical composition But different crystalline structures
Diamond and graphite are polymorphs (C).
Polymorphs
© W. W. Norton© W. W. Norton Geosciences 211, Physical Geology © 2005, Ron Parker
Crystal Growth Crystals grow by
Solidification from a melt. Precipitation from solution. Solid-state diffusion.
Minerals grow from a central seed
to fill the available space.
Mineral shape is controlled by
the shape of the surroundings.
Play Animation
Crystals grow by Solidification from a melt. Precipitation from solution. Solid-state diffusion.
Minerals grow from a central seed
to fill the available space.
Mineral shape is controlled by
the shape of the surroundings.
Play Animation
by Stephen Marshak
©, 2002, DIGIT, Prentice-Hall Geosciences 211, Physical Geology © 2005, Ron Parker
Mineral Physical Properties Characteristics determined by your 5 senses. Used to ID minerals Depend upon…
Chemical Composition Crystal Structure
Pyrite (FeS2) Cubic crystals, high specific gravity, striated crystal faces, black streak, metallic luster, dull brasscolor, sulfur smell, gold to fools
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 3
Geosciences 211, Physical Geology © 2005, Ron Parker
Physical PropertiesPhysical Properties Crystal Form Crystal Habit Luster Color Streak Hardness Cleavage Fracture Specific Gravity
Crystal Form Crystal Habit Luster Color Streak Hardness Cleavage Fracture Specific Gravity
Other Properties Taste Smell Effervescence Magnetism Feel Diaphaneity Piezoelectricity Pyroelectricity Refractive Index Elasticity Malleability Ductility SectilityBeryl var. aquamarineBeryl var. aquamarine
Geosciences 211, Physical Geology © 2005, Ron Parker
Crystal Form Ideal shape of crystal faces. Growth requires ideal conditions.
W. W. NortonW. W. Norton
Cubes Hexagonal PrismsBlades
RhombohedraDodecahedra
Octahedra
Tetragonal PrismsCompound Forms
Geosciences 211, Physical Geology © 2005, Ron Parker
Crystal Form Minerals may exhibit a range of crystal face
development. Euhedral – Well-developed crystal faces. Anhedral – No visible crystal faces. Usually
from growth in a confined space. Subhedral – Between the two.
Euhedral crystals - Growth in an open cavity.
Anhedral crystals - Growth in tight spaces.
Anhedral crystals common; euhedral rare.
Crystal QuartzCrystal Quartz
OlivineOlivine
Gold NuggetGold NuggetGeosciences 211, Physical Geology © 2005, Ron Parker
Appearance of reflected light Two basic categories
Metallic Nonmetallic
Vitreous (glassy) Silky Resinous Earthy (dull) Adamantine (brilliant)
Luster Topaz - vitreous
Vanadinite
Adamantine
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Color Often unreliable for mineral ID. May vary due to impurity elements. Many gemstones are brightly colored.
Often unreliable for mineral ID. May vary due to impurity elements. Many gemstones are brightly colored.
Quartz (SiO2)Quartz (SiO2)
Exhibits a variety of colorsExhibits a variety of colors
©, 2002, DIGIT, Prentice-Hall©, 2002, DIGIT, Prentice-Hall
Emerald (Beryl)Emerald (Beryl)
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Color of a mineral when scratched (crushed) on an unglazed porcelain plate.
Streak
Hematite – red-brown streakHematite – red-brown streakSphalerite – yellow streakSphalerite – yellow streak
Pyrite – black streakPyrite – black streak
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 4
Geosciences 211, Physical Geology © 2005, Ron Parker
Scratching resistance of a mineral. Minerals are compared to the Mohs Hardness Scale.
1. Talc, Graphite2. Gypsum3. Calcite4. Fluorite5. Apatite6. Orthoclase 7. Quartz8. Topaz9. Corundum10. Diamond
Hardness
Fingernail 2.5
Copper Penny 3.5
Glass - Steel 5.5
Geosciences 211, Physical Geology © 2005, Ron Parker
Tendency to break along planes of lattice weakness. Cleavage produces flat, shiny surfaces. Described by resulting geometric shapes.
Number of planes Angles between adjacent planes
Discriminate from crystal form (which cleavage may resemble).
Cleavage
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1 direction
2 directions at 90º
2 directions NOT at 90º
Cleavage
AmphiboleAmphibole
Potassium FeldsparPotassium Feldspar
Muscovite micaMuscovite mica
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3 directions at 90º
3 directions NOT at 90º
Cleavage
CalciteCalcite
GalenaGalena
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Cleavage 4 directions
6 directions
FluoriteFluorite
SphaleriteSphaleriteGeosciences 211, Physical Geology © 2005, Ron Parker
Conchoidal FractureConchoidal Fracture Some minerals lack planes of weakness = no cleavage. Due to equal molecular bonds in all directions. These minerals don’t cleave; they fracture.
Example: Conchoidal fracture Breaks in smooth curved surfaces. Very sharp edges. Shaped like the inside of a clam shell.
Conchoidal fracture in Quartz
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 5
Geosciences 211, Physical Geology © 2005, Ron Parker
Specific Gravity Ratio of the weight of a mineral to the weight of an
equal volume of water Average crustal value is 2.7 (quartz) Average mantle value is 3.3 (olivine)
SG is reflected in “heft” – how heavy the mineral feels. Galena – Heavy Feldspar - Light
Geosciences 211, Physical Geology © 2005, Ron Parker
Mineral Groups More than 4000 minerals have been identified. Only about 50 minerals are abundant. 98% of all minerals are made of 8 elements.
Oxygen O 46.6% Silicon Si 27.7% Aluminum Al 8.1% Iron Fe 5.0% Calcium Ca 3.6% Sodium Na 2.8% Potassium K 2.6% Magnesium Mg 2.1% All others 1.7%
Vanadinite
74.3 % of all minerals !!!74.3 % of all minerals !!!
Geosciences 211, Physical Geology © 2005, Ron Parker
Mineral Groups Minerals are classified based upon the dominant anion.
Silicates SiO24- Rock forming minerals
Carbonates CO32- Calcite, Dolomite
Sulfides S- Pyrite, Galena Oxides O2- Magnetite, hematite Sulfates SO4
2- Gypsum Halides Cl- or F- Fluorite, Halite
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Dominate the Earth’s crust. Oxygen and silicon account for 74.3 % of crustal mass. Silicates are know as “the rock-forming minerals.”
Basic unit is the silica tetrahedron 4 oxygens bond to a much smaller silicon
Dominate the Earth’s crust. Oxygen and silicon account for 74.3 % of crustal mass. Silicates are know as “the rock-forming minerals.”
Basic unit is the silica tetrahedron 4 oxygens bond to a much smaller silicon
Silicate Minerals
Geosciences 211, Physical Geology © 2005, Ron Parker
Silicon to oxygen ratio (Si:O) controls properties. Low Si:O (Upper Mantle, Oceanic Crust)
Fe and Mg rich minerals. Higher…
Density Specific Gravity Temperature and Pressure
High Si:O (Continental Crust) Na and K rich minerals. Lower…
Density Specific Gravity Temperature and Pressure
Silicon to oxygen ratio (Si:O) controls properties. Low Si:O (Upper Mantle, Oceanic Crust)
Fe and Mg rich minerals. Higher…
Density Specific Gravity Temperature and Pressure
High Si:O (Continental Crust) Na and K rich minerals. Lower…
Density Specific Gravity Temperature and Pressure
Silicate Minerals
Example: SerpentineExample: Serpentine
Example: QuartzExample: Quartz
Geosciences 211, Physical Geology © 2005, Ron Parker
Silicate Minerals
SiO2 0.50Framework Silicates
Si2O5 0.40Sheet Silicates
Si4O11 0.36Double Chain Silicates
SiO3 0.33Single Chain Silicates
SiO4 0.25Isolated Tetrahedra
Si:O RatioType of structure
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 6
Geosciences 211, Physical Geology © 2005, Ron Parker
Silica tetrahedra are linked together to form… Isolated Tetrahedra Double Tetrahedra Rings Single Chains Double Chains Sheets 3-D Frameworks
Silica tetrahedra are linked together to form… Isolated Tetrahedra Double Tetrahedra Rings Single Chains Double Chains Sheets 3-D Frameworks
Silicate Structures
Geosciences 211, Physical Geology © 2005, Ron Parker
Individual tetrahedra linked by cations Olivine Group
Hi T Fe-Mg silicate. Small crystals; no cleavage. Always olive green.
Garnet Group Small, rounded crystals with no cleavage. Dodecahedral crystals
Individual tetrahedra linked by cations Olivine Group
Hi T Fe-Mg silicate. Small crystals; no cleavage. Always olive green.
Garnet Group Small, rounded crystals with no cleavage. Dodecahedral crystals
Isolated Tetrahedra
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Pyroxene Group Single chain structures with Fe and Mg. Black to green color. Two distinctive cleavages at nearly 90 degrees. Stubby crystals. Augite is the most common pyroxene.
Single Chain Silicates
Geosciences 211, Physical Geology © 2005, Ron Parker
Amphibole Group Double chain structures made of a variety of ions. Two perfect cleavages at 124 and 56 degrees. Elongate “bladed” crystals. Hornblende, the most
common amphibole, is black.
Amphibole Group Double chain structures made of a variety of ions. Two perfect cleavages at 124 and 56 degrees. Elongate “bladed” crystals. Hornblende, the most
common amphibole, is black.
Double Chain Silicates
Geosciences 211, Physical Geology © 2005, Ron Parker
Mica Group Sheet structures that result in one
direction of perfect cleavage Biotite is the common dark
colored mica mineral Muscovite is the common light
colored mica mineral Clay Mineral Group
Residue left from the weathering of feldspars.
Sheet Silicates
Geosciences 211, Physical Geology © 2005, Ron Parker
Feldspar Group The most common mineral group. 2 directions of perfect cleavage at 90°. 2 Major types
Potassium feldspar Plagioclase feldspar
Silica (Quartz) Group Second most common
Framework Silicates
2005 Earlham Physical Geology Geosciences 211Lecture 5: Minerals
© 2005, Ronald L. ParkerThursday, January 27, 2005
Essentials of Geology, 2004, by Stephen MarshakW. W. Norton & CompanyChapter 3: Patterns in Nature: Minerals 7
Geosciences 211, Physical Geology © 2005, Ron Parker
Several major groups exist including Oxides Sulfides Sulfates Native Elements Carbonates Halides Phosphates
Non-silicate MineralsNext Class:Next Class:
Igneous Rocks
Reading: Marshak, 2004, Interlude A (pp. 98-104) and Chapter 3 )pp. 105-122)Jargon Quiz: Website
Reminder: Next Thursday (2/3) First Exam
Igneous Rocks
Reading: Marshak, 2004, Interlude A (pp. 98-104) and Chapter 3 )pp. 105-122)Jargon Quiz: Website
Reminder: Next Thursday (2/3) First Exam