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Earth: Portrait of a Planet 3rd edition
Minerals and Rocks
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Outline Minerals and rocksWhat are minerals? Geologic definition, significance. What are rocks? Geologic definition, 3 main types.
Mineral structure-Crystalline structure, crystals, crystal lattice-Determining atom arrangement (XRD), atomic bonding-Polymorphs, crystal growth and packing of atoms
Physical properties of mineralsOverview: common ones, less common onesColor, streak, luster, hardness, specific gravity, crystal habit/form, fracture, and cleavage
Mineral classes and silicates-Mineral classes, most importantly silicates-Silica tetrahedra building block -Silicate types: from individual tetrahedra to framework Chapter 5
Chapter 5MineralsThe building blocks of rocks, and hence, of Earth.-more than 4000 are known-dozens of new minerals are discovered annually
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
MineralsSocieties depend on mineral resources.Metals: iron, copper, lead, zinc, nickel, aluminum, etc.Non-metals: gypsum, limestone, clay
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
MineralsEconomically important Drive world economies.Historically important Dictated human history.Iron.Copper.Gold.Diamonds.Gems.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Mineral DefinitionGeologic definition of a mineral is specific.A naturally occuring solid, formed geologically, that has a crystal structure and a specific chemical composition, and is usually inorganic-doesnt include minerals in nutritional sense-A mineraloid exhibits some, but not all, properties
Gypsum
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
RocksRocks are Earth materials made from minerals.Most rocks have more than one kind of mineral.
-example: granite-mineral(s)?Potassium, quartz, hornblende-some are mono-mineralicLimestone (calcite), rock salt (halite), glacial ice
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Rock DefinitionGeologists definition: coherent, naturally occuring solid made up of an aggregate of minerals (or more
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
3 Main Rock Types1. Igneous solidified from molten rock or melt
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
3 Main Rock TypesSedimentary-cemented/precipitated from rock fragments/solution
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
3 Main Rock Types3. Metamorphic existing rock altered by changes in pressure and temperature
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Outline Minerals and rocksWhat are minerals? Geologic definition, significance. What are rocks? Geologic definition, 3 main types.
Mineral structure-Crystalline structure, crystals, crystal lattice-Determining atom arrangement (XRD), atomic bonding-Polymorphs, crystal growth and packing of atoms
Physical properties of mineralsOverview: common ones, less common onesColor, streak, luster, hardness, specific gravity, crystal habit/form, fracture, and cleavage
Mineral classes and silicates-Mineral classes, most importantly silicates-Silica tetrahedra building block -Silicate types: from individual tetrahedra to framework Chapter 5
Chapter 5
Crystalline StructureA solid with disordered atoms is called a glass
Atoms in a mineral are specifically orderedCrystalline structure based on atomic patterns
Glass
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
CrystalsMinerals displaying flat external faces (rare).-crystal faces form best in open cavities-crystals are often prized mineral specimens
BerylGreen, gem version -> emeraldQuartz
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
CrystalsConstancy of angles between crystal faces.-same mineral always (ideal) has same crystal faces-adjacent faces occur at regular (diagnostic) angle
Faces and angles reflect the atomic arrangement.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Crystal LatticeOrdered atoms in crystals form a lattice.Lattices are patterns that repeat in 3D This internal pattern controls mineral properties. -crystal shape-planes of symmetry
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Determining Atom ArrangementsX-Ray Diffraction (XRD) probes crystal lattices.Unique lattice spacing is used to ID minerals.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Bonding of AtomsLattice atoms are held in place by atomic bonds. Bond characteristics govern mineral properties. 5 recognized types of bonds (Appendix A).-covalent (gain/loose )-metallic-van
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Polymorphs (many + form)Same composition but different crystal structure.Polymorphs show the importance of bond type.Diamond and graphite are carbon polymorphs (C)-diamond: strong covalent bonds; hardest mineral-graphite: weak van der waals bonds; softest mineral
Graphite
Diamond
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Crystal GrowthCrystals grow as atoms attach to mineral surfaces-growth starts from a central seed crystal-growth expands outward
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Outward crystal growth fills available space.Resulting crystal shape governed by surroundings.-open space: good crystal faces grow-confined space: no crystal spaces
Crystals mostly grow bySolidification from a meltPrecipitation from solution
Crystal Growth
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Atomic PackingIon size (radius) and charge control packing. Ion atom charged due to gain or loss of an electronCation positive ion due to loss of electronAnion negative ion due to gain of electronIonic radii due to # of electrons; anions are bigger.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Atomic PackingAnions and cations bond to neutralize charges.Anion Cation fit governed by relative size.-large central cation larger number of anions-smalll central cation smaller number of anions
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Outline Minerals and rocksWhat are minerals? Geologic definition, significance. What are rocks? Geologic definition, 3 main types.
Mineral structure-Crystalline structure, crystals, crystal lattice-Determining atom arrangement (XRD), atomic bonding-Polymorphs, crystal growth and packing of atoms
Physical properties of mineralsOverview: common ones, less common onesColor, streak, luster, hardness, specific gravity, crystal habit/form, fracture, and cleavage
Mineral classes and silicates-Mineral classes, most importantly silicates-Silica tetrahedra building block -Silicate types: from individual tetrahedra to framework Chapter 5
Chapter 5Physical Properties of MineralsCharacteristics determined by your senses.Used to ID minerals.Properties depend upon-chemical composition-crystal structureSome are diagnostic.i.e. pyrite (fes2)-minerals have a unique
Pyrite
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Physical PropertiesCommon properties:Color.Streak.Luster.Hardness.Specific gravity.Crystal habit (ideal shape).Crystal form.Fracture.Cleavage.
Needle-like crystal habit
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Physical PropertiesLess common physical properties:Taste.Smell.Feel.Magnetism. Effervescence.Refractive index.Malleability.
Calcite effervesces with acid
Magnetite crystals on a large magnet.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
ColorColor is diagnostic for some minerals.E.g. olivine/malachite is always green, azurite is always blueSome minerals may exhibit a broad color range.-quartz (clear, white, yellow, pink, purple
Quartz Many colors
Malachite always green
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
StreakColor of a mineral struck across unglazed porcelain.Streak is often a useful diagnostic property.Congruent streak streak color same as mineral-magnetite: black mineral; black streakIncongruent streak streak color different than mineral-chromite: black mineral; greenish-brown streak
Hematite Red-brown streak
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
LusterThe way a mineral scatters light.Two subdivisions. Metallic Looks like a metal.Nonmetallic.Vitreous (glassy).Satiny.Silky.Resinous.Pearly.Earthy (dull). Adamantine (brilliant).
Satin spar Gypsum Satiny luster
Quartz Vitreous luster
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
HardnessScratching resistance of a mineral. Hardness compared to Mohs Hardness Scale.Talc, GraphiteGypsumCalciteFluoriteApatiteOrthoclase QuartzTopazCorundumDiamond
Glass - Steel 5.5
Fingernail 2.5
Copper Penny 3.5
Steel File 6.5
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
PyriteSpecific GravityRelated to density (mass per volume).Mineral weight over weight of equal water volume.Specific gravity is heft how heavy it feels-pyrite: heavy (sg 5.0)-feldspar: light (sg 2.6)-pyrite feels heavier
Potassium Feldspar
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Crystal HabitCrystal habit is the ideal shape of crystal faces.-ideal growth requires ideal conditions-many terms are used to describe habit
CubesHexagonal PrismsBladesRhombohedraDodecahedraOctahedraTetragonal PrismsCompound Forms
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Crystal FormMinerals vary in crystal face development.Euhedral good crystal faces; gown in open cavityAnhedral no crystal faces; grown in tight spaceSubhedral between the two
Face development indicates growth historyAnhedral crystals common; euhedral less so.
Amethyst Geode
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
FractureSome minerals lack planes of weakness. Due to equal molecular bonds in all directions.These minerals fracture and hence dont have cleavage.Example: Quartz
Obsidian
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
CleavageTendency to break along planes of weakness.Due to equal molecular bonds in all directions.These minerals fracture and hence dont have cleavage.i.e. quartz displays conchoidal fracture-shaped like inside of a clam shell-breaks along smooth curved surfaces -cleavage produces flat surfaces-described by number of planes and their angles
Sometimes mistaken for crystal habit.
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Cleavage Examples of Cleavage:
1 direction
2 directions at 90
2 directions NOT at 90
Muscovite Mica
AmphibolePotassium Feldspar
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Outline Minerals and rocksWhat are minerals? Geologic definition, significance. What are rocks? Geologic definition, 3 main types.
Mineral structure-Crystalline structure, crystals, crystal lattice-Determining atom arrangement (XRD), atomic bonding-Polymorphs, crystal growth and packing of atoms
Physical properties of mineralsOverview: common ones, less common onesColor, streak, luster, hardness, specific gravity, crystal habit/form, fracture, and cleavage
Mineral classes and silicates-Mineral classes, most importantly silicates-Silica tetrahedra building block -Silicate types: from individual tetrahedra to framework Chapter 5
Chapter 5Mineral ClassesMinerals are classified by their dominant anion.Silicates SiO24- Most rock-forming mins!OxidesO2- Magnetite, HematiteSulfidesS- Pyrite, GalenaSulfatesSO42- GypsumHalides Cl- or F- Fluorite, HaliteCarbonatesCO32- Calcite, DolomiteNative ElementsCu, Au, CCopper, Gold, Graphite
Fluorite (Halide)
Native Copper
Malachite (Carbonate)
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Silicates are known as the rock-forming minerals. They dominate the Earths crust. Oxygen and silicon-94.7% of crustal volume-74.3% of crustal mass
Silicate Minerals
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
The building block (anion) unit is the silica tetrahedron.4 oxygen atoms are bonded to 1 silicon atom (SiO44-).-silicon is tiny; oxygen is huge-the silica tetrahedron has a net -4 ionic charge-the silicate unit can be depicted by-spheres-ball and stick model-polyhedra
Silicate Minerals
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Silicate MineralsSilica tetrahedra link together by sharing oxygens.More shared oxygen higher Si:O ratio; governs-melting temp-mineral structure and cations present-susceptibility to chemical weatheringType of Silicate StructureFormulaSi:O RatioIndependent TetrahedraSiO40.25Double TetrahedraSi2O70.29Ring SilicatesSi6O180.33Single ChainsSiO30.33Double ChainsSi4O110.36Sheet SilicatesSi2O50.40Framework SilicatesSiO20.50
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Independent TetrahedraTetrahedra share no oxygens - linked by cations.Olivine Group.High temperature Fe-Mg silicate.Small green crystals; no cleavage.Garnet Group.Equant crystals with no cleavage.Dodecahedral (12 sided) crystals.
Garnet
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Single-Chain SilicatesSingle-chain structures bonded with Fe and Mg.Pyroxene Group.Black to green color. Two distinctive cleavages at nearly 90.Stubby crystals.Augite is the most common pyroxene.
Pyroxene
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Double-Chain SilicatesDouble chain of silica tetrahedra bonded together. Contain a variety of cations.Amphiboles two perfect cleavagesElongate crystals
Hornblende
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Sheet Silicates2-dimensional sheets of linked tetrahedra.Characterized by one direction of perfect cleavage.Mica Group botite (dark) and mucsovite (light)Clay Mineral Group feldspar weathering residue; tiny
Muscovite (Mica)
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
Framework SilicatesAll 4 oxygens in the silica tetrahedra are shared.Feldspar Group plagioclase and potassium feldsparSilica (Quartz) Group contains only si and o
Potassium Feldspar
Chapter 5
Earth: Portrait of a Planet, 3rd edition2008, by Stephen Marshak W. W. Norton & Company
Chapter 5 Patterns in Nature: MineralsPowerPoint slides prepared by Ronald L. ParkerEarlham College, Department of Geosciences, Richmond, Indiana [email protected]#
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