EOS 205 Mid notes

The flashcards below were created by user spb83 on FreezingBlue Flashcards.

  1. How many minerals are there
  2. What is the difference between a mineral and a crystal?
    A mineral is a crystal but not all crystals are minerals

    Crystal just means a solid with flat faces due to the orered, geometricaly symetrical atomic strucutre

    to be a mineral it must meet the mineral criteria
  3. what is a mineral?  (4)
    -naturally occurring

    -homogeneous solid (unit cell is the same as entire sample)

    -definite (but not fixed) chemical composition

    -highly ordered atomic arrangement
  4. Is ice a mineral?


    calcium carbonate (CaCO3)?
    Ice yes

    sugar no

    CaCO- dependent on its form
  5. what is the unit cell?
    the smallest divisible part of a mineral

    i.e. quartz is made of millions of SiO4 attached together

    one single SiO4 molecule is the unit cell
  6. Why do minerals have the properties they have?
    It basically comes down to each have its very own unique chemical composition and arrangement of atoms, cat ions and an ions.

    +/- charge is created resulting in magnetism

    crystal sturcture can determine color, luster, hardness etc.
  7. ten most common rock forming minerals
    • quartz
    • biotite
    • muscovite
    • anorthite (plagi-feld)
    • orthoclase (alki-feld)
    • albite
    • olivine
    • pyroxene
    • amphibole
    • calcite
  8. what is the most common mineral group in the crust?
  9. what are the layers of goldschmidts periodic table? (4)

    • atmophile-gas
    • lithophile-silica liquid
    • Chalcophile- sulfide liquids
    • Siderophile- metalic liquids
  10. which minerals are in the crust (4)
    • quartz
    • feldspars
    • amphiboles
    • micas
  11. which minerals in the mantel? (3)
    • olivine
    • pyroxene
    • garnet
  12. what is a silicate
    most common in earths crust

    made of a metal-Si-O
  13. 4 types of bonding and examples
    ionic - electron substitution (NaCl)

    covealent- share elctrons (diamond)

    metalic- electrons free to roam (gold)

    vanderwalls- weak +/- attractions (graphite)
  14. paulings rules (4)  #2 is ignored by prof
    1) every cation has a coordination polyhedron of anions based on the radius sums and ratios

    3)shared edges (and more so with faces) reduces stability

    4)high valency/small CN dont shatre polyhedra

    5)# of differing constituents in a crystal tend to be small
  15. why is quartz commonly so pure?
    its SiO4 such that the Si has a tetrahedral (CN 6) polyhedra which doesent allow room for substitutions and impuritues
  16. what changes the CN (2)
    for same structure- ion size 

    for same ion - pressure (depth)
  17. Si and mantel discontinuieties
    • the si in olivine (Y2ZO4) Z=tetrahedral CN-4
    •  changes to a CN4/6 then to a CN6 at the 410 and 660 discontinuities
  18. what is a polymorph? Give 2 examples
    same chemical composition different xstal structure

    1) quartz-->coesite-->shitsovite

  19. what is a chromophore?
    give an example
    an atom (or group) responsible for the color in a mineral.

    Ex- in olivine and garnet Fe2+ is the chromophore

    it sits in diffrent sites and thus makes differing color

    • olivine (fayalite) Fe2Si... Fe=Y=CN6
    • garnet (almandine)  Fe3Al2Si3... Fe=X=CN8
  20. sum up  crystal field transitions?
    interactions between light and unfilled d orbitials of transition series elements (Sc-->Zn)

    the d orbitals are split into higher and lower energy levels

    octa (3 low 2 high) creates Δo

    tetra (2 low 3 high) creates Δt

    presence and value of delta influences wavelength absorbtion


    this explains the chromophore difference in olivine/garnet with Fe
  21. crystal field splitting (Δ) depends on (3)
    • 1) size of ion
    • 2)oxidation state
    • 3)CN
  22. Color is caused by (4)
    • 1) crystal field transmissions/splitting
    • (crhomophers, dif sites, dif CN)

    2) color centers (defects in structure allow the build up of electrons)

    3)charge transfer transitions (transfer of electrons from one energy level to another) [Fe2++Ti4+]+photon----->[Fe3++Ti4+]

    4) impurities
  23. Two principle minerals that record seafloor spreading
    Magnetite (Fe3O4)

    Illmanite (FeTiO3)
  24. magnetism requires (2)
    1. transition series elements

    2. magnetic moments (created by valence shells and spin)
  25. 3 types of magnetism
    diamagnetic   para magnetic     ferrimagnetic
  26. explain diamagnetism and an example
    weakest form

    mineral response (suscebtability) opposite that of applied field

    not net mag...goes away if applied gone

    ex quartz and feldspars
  27. Paramagnetism explan and examples
    mineral suscebtability has the same direction as the applied field

    retains a weak net field when applied removed

    examples (biotite hornblende)
  28. Ferri magnetism and examples
    very strong magnetism

    strong net retention

    to remove must heat above currie pt

    ex magnetite, illmanite
  29. describe x ray diffraction  (XRD)
    identifies mineral by its unique xstal structure

    xrays difract due to the lattice structure of the mineral and the d-spacing 

    gives info on atom locations and planes

    • mineral must be powderized
    • mount on slide and rotate under xray
    • optimum angle Θ gives max difraction (when waves in-phase with xray)
    • creates chart

    only tells you the xstal structure not the composition
  30. Electron probe microanalysis (EPM)
    used to determine composition but says nothing about strucutre

    electron beam shot at a thin sample

    phonton exictes electrons makes them jump to higher level

    sample emmits xrays as e moves back to stable level

    xrays and associated backscatter create a "finger print of the mineral"
  31. isomorphs vs end members
    isomorphs are the general structure i.e. olivine Y2ZO4 w/ Y=Mg, Fe & Z=Si

    endmembers are the extremes of the iso morphs i.e. 

    • fosterite Mg2SiO4
    • fayalite Fe2SiO4
  32. ionic substitution is
  33. 3 factors that influence ionic substitution
    1. size of ions (15% extensive, 30% limited)

    2. charge (nuetrality must be preserved)

    3. Temp, greater temps creates more tolerance
  34. types of solid solutions/substitutions (3)
    1. ionic (based on ion size and charge) Na+Al3+=Ca2+Mg2+

    2. intersital (filling of voids in lattice structure)

    3. omission (high charge cat ion may replace two lo charge)  K+K=Pb2
  35. what is exsolution? how does it work?
    the unmixing and reordering of a solid solution into two separate minerals

    creates lamellea (the white and pink lines in kspar)

    At high T a molecules are more excited and easily manipulated so that ions with varrying radius may be tolerated bonding with each other.

    As the mineral cools this diference in ion radius is not tolerated and it cleans up into ordered arrangement
  36. what does phase mean
    Mechanically separated w/ distinct boundaries as in exsolution lamallea
  37. what does a chemical analysis tell you about a mineral, how do you use it?
    it gives the % weight which can be converted into mols then a mole ration of cations to anions to determine a chemical composition and formula

    when given __anions to ___cations match it up with memorized X#Y#Z#O# to dtermine the solid solution.

    trick you may have to divide as it could be a large ration representing a multiple of the chemical formula
  38. iso morph vs polymorph
    isomorph is diffrent chemical formula but same shape CaCO3 MgCO3 FeCO3 all rombohedrals

    polymorph is the same formula with diffrent shapes shuch as kyanite sillimantite and andalusite
  39. What are the things that control symmetry (4)
    reflection, rotation, inversion and rotoinversion
  40. what is reflection what are the two components?
    symetry is created by the reflection across a mirror plane

    • reflection is the opperation
    • the mirror plane is the opperator
  41. rotational symetry
    the ___ fold refers to how many rotations it takes to achieve "same look"

    • 1 fold = 360
    • 2 fold = 180
    • 3 fold = 120
    • 4 fold = 90
    • 5 is forbidden
    • 6 fold = 60

    360/degree of rotation to achieve symetry= fold number
  42. what is inversion?
    not quite the same as mirroring or rotation

    in a way its rotated 180 (troughits axis not the cartiesin axis as in rotation and mirroring) and then rotated over a line 45deg between cartiesian axis

    if in NE quadrant rotate the item 180 degrees through its center

    then rotate it over the line running NW-SE so that the object ends up in the SW quadrant
  43. rotoinversion
    rotate itme 180 degrees then invert it
  44. what is the difference between habit and form
    crystal form is the arragement/symetry etc of the faces/planes of the crystal

    habit is how the common charectoristic-shape of the crystal
  45. point groups and crystal systems? 
    Total #?
    who has most/Least?
    point groups are unique combinations of symmetry operators...there are 32 of them

    these 32 point groups make up the 6 crystal systems

    cubic has the most (32) while triclinic has none
  46. From MT

    What are the three factors that govern ionic substitutions?
    • *Ionic Radius: 15% extensive %30 limited
    • Ex: Mg w/ Fe2+=extensive same size
    •       Mg w/ Ca2+=limited Ca2+ is larger

    • *Charge: neutrality preservation
    • Ex:K++K+=>Pb2+

    *Temp: higher T alllows for greater variations in CN
  47. From MT

    Give examples of simple ionic substitution in olivine and feldspar solutions
    • Olivine Y2ZO4
    • Y= Fe, Mg results in forsterite Mg2SiO4 & fayalite Fe2SiO4

    • Feldspar MZ4O8
    • M= Ca Na Al (K) results in orthoclase KAlSi3O8  & Albite NaAlSi3O8
  48. From MT

    What is the strongest type of magnetism? Name two minerals and describe their electronic state of their cations to achieve this magnetism.
    Ferri-magnetism is strongest, magnetism is in direction of applied field, weak net magnetism remains, needs to be at currie pt to undo net magnetism

    examples magnetite and illminite

    cations must have half filled d-orbitals in the same direction as the applied field
  49. From MT

    what factor governs coordination geometry
    give an example of 3 specific coordination numbers/geometrys in a comon rock forming mineral
    ionic radius ratio

    • example 
    • andradite Ca3Fe2Si3O12

    • Ca is in the cubic site CN 8
    • Fe is in the octahedral site Cn 6
    • Si is in the tetrahedral csite Cn 4
  50. Quartz contains little to no Uranium wheres Zircon may have plenty. Explain using paulings rules.

    • 1. cation surrounded by coordniation of anions based on radius ratio
    • 3.shared edges and faces decrease stabaility
    • 4.high valence low CN reduces sharing
    • 5. # of constituents in an xstal tend to be small

    specificly 1&4 show that qurtz is extremly pure as it is SiO2 (small high valence) very limited places for substitutions whereas zircon has lower valence, larger, and more constiuients which are easily subed for the Ur
  51. From MT

    Describe crystal field transition/splitting. what factors or variable sgenerate different colours by this mechanism?
    • depends on 
    • identity of transition metal
    • arrangement of empty 3d vallence shells
    • the ions oxidation state
    • CN of site

    the above effects the size of Δ which controlls wavelenght absorption

    • example 
    • octahedral has 3 high and 2 low splitting centers
    • tetrahedral 2 high and 3 low
  52. From MT

    give an example of crystal field transition where two diffrent chromophores produced two diffrent colors in the same mineral
    Fe in garnet on cubic site

    • oxidation states
    • Fe3+ = brown
    • Fe2+ = red
  53. From MT

    Give an example of a crystal field transition where one chromophore produced different colors in diferent minerals
    • Fe2+ in garnet, CN 8 = red
    • Fe2+ in olivine CN6 = green
Card Set
EOS 205 Mid notes
up to mid term 1
Show Answers