minerals and rocks
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Minerals and Rocks. Lecture Outline. What are minerals? Common rock-forming minerals Physical properties of minerals Basic rock types The rock cycle. Minerals. A mineral is a naturally occurring, solid crystalline substance, generally inorganic, with a specific chemical composition.

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lecture outline
Lecture Outline
  • What are minerals?
  • Common rock-forming minerals
  • Physical properties of minerals
  • Basic rock types
  • The rock cycle
minerals
Minerals

A mineral is a naturally occurring, solid

crystalline substance, generally inorganic,

with a specific chemical composition

  • Natural
  • Solid
  • Atoms arranged in orderly repeating 3D array: crystalline
  • Not part of the tissue of an organism
  • Composition fixed or varies within defined limits

Minerals are the “building blocks” of rock

slide4

Large individual crystals (rare)

Mass of small grains: each is a crystal, but grown up against each other

atomic structure of minerals
Atomic Structure of Minerals
  • NaCl - sodium chloride

Halite

chemical bonds ionic
Chemical Bonds: Ionic
  • Electrical attraction between ions of opposite charge
    • Bond strength increases with the electrical charges of the ions
    • Bond strength decreases as the distance between the ions increases
  • Most minerals are this kind of compound
slide7

Ionic Bonding example:

halite

Cation

Anion

Na+

Cl-

covalent bonds
Covalent Bonds:
  • Electron sharing
  • Generally stronger than ionic bonds (e.g., diamond)
crystallization of minerals
Crystallization of Minerals
  • Need starting material with atoms that can come together in the proper proportions
    • Growth from a liquid or a gas
  • Time and space for crystallization
  • Appropriate temperature and pressure
  • Examples
    • Magma that has cooled below its melting point
    • Supersaturated solution --> precipitation
crystallization of minerals1
Crystallization of Minerals
  • Crystals begin as an initial “seed” - a microscopic crystal
  • Atoms keep being added in a 3D array, repeating the basic arrangement
  • Crystal faces are based on the array structure
cations and anions
Cations and Anions
  • Anions are typically large
  • Cations are relatively small
  • Crystal structure is determined largely by the arrangement of the anions
slide12

Common cations and anions

Radii given in angstroms; 10-8 cm

ions can be compound
Ions can be compound
  • So far, we’ve talked about individual atomic ions
  • Many common minerals are silicates

SiO44-

Complex ions act as a single ion in forming crystal structure

cation substitution
Cation Substitution
  • Crystal structure determined by those large anions
  • Various cations can substitute for each other in many minerals
    • Same crystal structure
    • Different chemical composition
polymorphs
Polymorphs

Minerals with the same composition, but different crystal structure.

slide17

Common Rock-Forming Minerals

Minerals fall into a small number of related “families” based mainly on the anion in them

silicates
Silicates
  • Quartz (SiO2), K-feldspar (KAlSi3O8), olivine ((Mg, Fe)2SiO4), kaolinite (Al2Si2O5(OH)4)
  • Most abundant minerals in the Earth\'s crust
  • Silicate ion (tetrahedron), SiO44-
silicate structure
Silicate structure
  • Most of the most common rocks in the crust are silicates
  • Silicate tetrahedra can combine in several ways to form many common minerals
  • Typical cations:

K+, Ca+, Na+, Mg2+, Al3+, Fe2+

carbonates
Carbonates
  • Cations with carbonate ion (CO32-)
  • Calcite (CaCO3), dolomite (CaMg(CO3)2), siderite (FeCO3), smithsonite (ZnCO3)
  • Make up many common rocks including limestone andmarble
  • Very important for CCS!
oxides
Oxides
  • Compounds of metallic cations and oxygen
  • 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
sulfides
Sulfides
  • Metallic cations with sulfide (S2-) ion
  • Important for ores of copper, zinc, nickel, lead, iron
  • Pyrite (FeS2), galena (PbS)
sulfates
Sulfates
  • Minerals with sulfate ion (SO42-)
  • Gypsum (CaSO4.H2O), anhydrite (CaSO4)
slide33

Gypsum

  • 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
identification of minerals
Identification of Minerals
  • Chemical composition (microprobes and wet chemical methods)
  • Crystal structure (X-ray diffraction)
  • Physical properties
physical properties1
Physical properties
  • Hardness
  • Cleavage: tendency of minerals to break along flat planar surfaces into geometries that are determined by their crystal structure
physical properties2
Physical properties
  • Hardness
  • Cleavage
  • Fracture: tendency to break along other surfaces (not cleavage planes)
physical properties3
Physical properties
  • Hardness
  • Cleavage
  • Fracture
  • Luster (metallic, vitreous, resinous, earthy, etc.)
  • Color (often a poor indicator; streak color is better)
  • Specific gravity
  • Crystal habit (shape)
rocks
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
  • Volcanic glass
  • Solidified organic matter
  • Appearance controlled by composition and size and arrangement of aggregate grains (texture)
rock types
Rock Types
    • Igneous
      • Form by solidification of molten rock (magma)
  • Sedimentary
    • Form by lithification of sediment (sand, silt, clay, shells)
  • Metamorphic
    • Form by transformations of preexisting rocks (in the solid state)
igneous rocks
Igneous Rocks

Intrusive

Extrusive

intrusive plutonic
Intrusive (plutonic)
  • Form within the Earth
  • Slow cooling
  • Interlocking large crystals
  • Example = granite
extrusive volcanic
Extrusive (volcanic)
  • Form on the surface of the Earth as a result of volcanic eruption
  • Rapid cooling
  • Glassy and/or fine-grained texture
  • Example = basalt
origin of sediment
Origin of sediment
  • Produced by weathering and erosion or by precipitation from solution
  • Weathering = chemical and mechanical breakdown of rocks
  • Erosion = processes that get the weathered material moving
sediment types
Sediment types
  • 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.
slide55

Clastic

Chemical/biochemical

lithification
Lithification
  • The process that converts sediments into solid rock
  • Compaction
  • Cementation
slide61

conglomerate

metaconglomerate

slide62

granite

gneiss

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