Minerals and Rocks. Lecture Outline What are minerals? What are minerals? Common rock-forming...
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Minerals and Rocks. Lecture Outline What are minerals? What are minerals? Common rock-forming minerals Common rock-forming minerals Physical properties
Lecture Outline What are minerals? What are minerals? Common
rock-forming minerals Common rock-forming minerals Physical
properties of minerals Physical properties of minerals Basic rock
types Basic rock types The rock cycle The rock cycle
Slide 3
Minerals Natural Natural Solid Solid Atoms arranged in orderly
repeating 3D array: crystalline Atoms arranged in orderly repeating
3D array: crystalline Not part of the tissue of an organism Not
part of the tissue of an organism Composition fixed or varies
within defined limits Composition fixed or varies within defined
limits Minerals are the building blocks of rock A mineral is a
naturally occurring, solid crystalline substance, generally
inorganic, with a specific chemical composition
Slide 4
Large individual crystals (rare) Mass of small grains: each is
a crystal, but grown up against each other
Chemical Bonds: Ionic Electrical attraction between ions of
opposite charge Electrical attraction between ions of opposite
charge Bond strength increases with the electrical charges of the
ions Bond strength increases with the electrical charges of the
ions Bond strength decreases as the distance between the ions
increases Bond strength decreases as the distance between the ions
increases Most minerals are this kind of compound Most minerals are
this kind of compound
Slide 7
Na + Cl - Ionic Bonding example: halite AnionCation
Slide 8
Covalent Bonds: Electron sharing Electron sharing Generally
stronger than ionic bonds (e.g., diamond) Generally stronger than
ionic bonds (e.g., diamond)
Slide 9
Crystallization of Minerals Need starting material with atoms
that can come together in the proper proportions Need starting
material with atoms that can come together in the proper
proportions Growth from a liquid or a gas Growth from a liquid or a
gas Time and space for crystallization Time and space for
crystallization Appropriate temperature and pressure Appropriate
temperature and pressure Examples Examples Magma that has cooled
below its melting point Magma that has cooled below its melting
point Supersaturated solution --> precipitation Supersaturated
solution --> precipitation
Slide 10
Crystallization of Minerals Crystals begin as an initial seed -
a microscopic crystal Crystals begin as an initial seed - a
microscopic crystal Atoms keep being added in a 3D array, repeating
the basic arrangement Atoms keep being added in a 3D array,
repeating the basic arrangement Crystal faces are based on the
array structure Crystal faces are based on the array structure
Slide 11
Cations and Anions Anions are typically large Anions are
typically large Cations are relatively small Cations are relatively
small Crystal structure is determined largely by the arrangement of
the anions Crystal structure is determined largely by the
arrangement of the anions
Slide 12
Common cations and anions Radii given in angstroms; 10 -8
cm
Slide 13
Ions can be compound So far, weve talked about individual
atomic ions So far, weve talked about individual atomic ions Many
common minerals are silicates Many common minerals are silicates
SiO 4 4- Complex ions act as a single ion in forming crystal
structure
Slide 14
Cation Substitution Crystal structure determined by those large
anions Crystal structure determined by those large anions Various
cations can substitute for each other in many minerals Various
cations can substitute for each other in many minerals Same crystal
structure Same crystal structure Different chemical composition
Different chemical composition
Slide 15
Slide 16
Polymorphs Minerals with the same composition, but different
crystal structure. Minerals with the same composition, but
different crystal structure.
Slide 17
Common Rock-Forming Minerals Minerals fall into a small number
of related families based mainly on the anion in them
Slide 18
Silicates Most abundant minerals in the Earth's crust Most
abundant minerals in the Earth's crust Silicate ion (tetrahedron),
SiO 4 4- Silicate ion (tetrahedron), SiO 4 4- Quartz (SiO 2 ),
K-feldspar (KAlSi 3 O 8 ), olivine ((Mg, Fe) 2 SiO 4 ), kaolinite
(Al 2 Si 2 O 5 (OH) 4 ) Quartz (SiO 2 ), K-feldspar (KAlSi 3 O 8 ),
olivine ((Mg, Fe) 2 SiO 4 ), kaolinite (Al 2 Si 2 O 5 (OH) 4 )
Slide 19
Quartz (SiO 2 )
Slide 20
Silicate structure Most of the most common rocks in the crust
are silicates Most of the most common rocks in the crust are
silicates Silicate tetrahedra can combine in several ways to form
many common minerals Silicate tetrahedra can combine in several
ways to form many common minerals Typical cations: Typical cations:
K +, Ca +, Na +, Mg 2+, Al 3+, Fe 2+
Slide 21
Different numbers of oxygen ions are shared among
tetrahedra
Slide 22
Carbonates Cations with carbonate ion (CO 3 2- ) Cations with
carbonate ion (CO 3 2- ) Calcite (CaCO 3 ), dolomite (CaMg(CO 3 ) 2
), siderite (FeCO 3 ), smithsonite (ZnCO 3 ) Calcite (CaCO 3 ),
dolomite (CaMg(CO 3 ) 2 ), siderite (FeCO 3 ), smithsonite (ZnCO 3
) Make up many common rocks including limestone and marble Make up
many common rocks including limestone and marble Very important for
CCS! Very important for CCS!
Slide 23
Calcite (CaCO 3 )
Slide 24
CaCO 3 + 2H + = Ca 2+ + CO 2 + H 2 O
Slide 25
Smithsonite (ZnCO 3 )
Slide 26
Oxides Compounds of metallic cations and oxygen Compounds of
metallic cations and oxygen Important for many metal ores needed to
make things (e.g., iron, chromium, titanium) Important for many
metal ores needed to make things (e.g., iron, chromium, titanium)
Ores are economically useful (i.e., possible to mine) mineral
deposits Ores are economically useful (i.e., possible to mine)
mineral deposits
Slide 27
Hematite (Fe 2 O 3 )
Slide 28
Sulfides Metallic cations with sulfide (S 2- ) ion Metallic
cations with sulfide (S 2- ) ion Important for ores of copper,
zinc, nickel, lead, iron Important for ores of copper, zinc,
nickel, lead, iron Pyrite (FeS 2 ), galena (PbS) Pyrite (FeS 2 ),
galena (PbS)
Slide 29
Galena (PbS)
Slide 30
Slide 31
Sulfates Minerals with sulfate ion (SO 4 2- ) Minerals with
sulfate ion (SO 4 2- ) Gypsum (CaSO 4. H 2 O), anhydrite (CaSO 4 )
Gypsum (CaSO 4. H 2 O), anhydrite (CaSO 4 )
Slide 32
Gypsum
Slide 33
Cave of the Crystals 1,000 feet depth in the silver and lead
Naica Mine 150 degrees, with 100 % humidity 4-ft diameter columns
50 ft length Gypsum
Slide 34
Identification of Minerals Chemical composition (microprobes
and wet chemical methods) Chemical composition (microprobes and wet
chemical methods) Crystal structure (X-ray diffraction) Crystal
structure (X-ray diffraction) Physical properties Physical
properties
Slide 35
Physical properties Hardness Hardness
Slide 36
Slide 37
Physical properties Hardness Hardness Cleavage: tendency of
minerals to break along flat planar surfaces into geometries that
are determined by their crystal structure Cleavage: tendency of
minerals to break along flat planar surfaces into geometries that
are determined by their crystal structure
Slide 38
Cleavage in mica
Slide 39
Cleavage in calcite
Slide 40
Halite (NaCl)
Slide 41
Physical properties Hardness Hardness Cleavage Cleavage
Fracture: tendency to break along other surfaces (not cleavage
planes) Fracture: tendency to break along other surfaces (not
cleavage planes)
Slide 42
Conchoidal fractures
Slide 43
Physical properties Hardness Hardness Cleavage Cleavage
Fracture Fracture Luster (metallic, vitreous, resinous, earthy,
etc.) Luster (metallic, vitreous, resinous, earthy, etc.) Color
(often a poor indicator; streak color is better) Color (often a
poor indicator; streak color is better) Specific gravity Specific
gravity Crystal habit (shape) Crystal habit (shape)
Slide 44
Rocks An aggregate of one or more minerals; or a body of
undifferentiated mineral matter (e.g., obsidian); or of solid
organic matter (e.g., coal) More than one crystal More than one
crystal Volcanic glass Volcanic glass Solidified organic matter
Solidified organic matter Appearance controlled by composition and
size and arrangement of aggregate grains (texture) Appearance
controlled by composition and size and arrangement of aggregate
grains (texture)
Slide 45
Rock Types Igneous Igneous Form by solidification of molten
rock (magma) Form by solidification of molten rock (magma)
Sedimentary Sedimentary Form by lithification of sediment (sand,
silt, clay, shells) Form by lithification of sediment (sand, silt,
clay, shells) Metamorphic Metamorphic Form by transformations of
preexisting rocks (in the solid state) Form by transformations of
preexisting rocks (in the solid state)
Intrusive (plutonic) Form within the Earth Form within the
Earth Slow cooling Slow cooling Interlocking large crystals
Interlocking large crystals Example = granite Example =
granite
Slide 48
Slide 49
Extrusive (volcanic) Form on the surface of the Earth as a
result of volcanic eruption Form on the surface of the Earth as a
result of volcanic eruption Rapid cooling Rapid cooling Glassy
and/or fine-grained texture Glassy and/or fine-grained texture
Example = basalt Example = basalt
Slide 50
Basalt: igneous extrusive
Slide 51
Intrusive and extrusive igneous rocks
Slide 52
Sedimentary Rocks
Slide 53
Origin of sediment Produced by weathering and erosion or by
precipitation from solution Produced by weathering and erosion or
by precipitation from solution Weathering = chemical and mechanical
breakdown of rocks Weathering = chemical and mechanical breakdown
of rocks Erosion = processes that get the weathered material moving
Erosion = processes that get the weathered material moving
Slide 54
Sediment types Clastic sediments are derived from the physical
deposition of particles produced by weathering and erosion of
preexisting rock. Clastic sediments are derived from the physical
deposition of particles produced by weathering and erosion of
preexisting rock. Chemical and biochemical sediments are
precipitated from solution. Chemical and biochemical sediments are
precipitated from solution.
Slide 55
Clastic Chemical/biochemical
Slide 56
Lithification The process that converts sediments into solid
rock The process that converts sediments into solid rock Compaction
Compaction Cementation Cementation
