Physical properties of minerals (G) CH6

  1. What are the two ways mineral hardness can be assessed
    Mohs hardness (relative scale)

    Indentation hardeness/ Vickers hardness number (absolute scale)
  2. What does clevage represent?
    Planes of weaknes in crystals along which a mineral may break bonds with relative ease; commonly NOT PARALLEL TO THE crystal face which are the growth faces
  3. What are the most common causes of colour in minerals
    • -Presence of metal ions  (first row of transition elements ti-cu)
    • -Intervalence charge transfer- metal ions in mixed oxidation states.
  4. what is fluorescence, how does it occur
    • type of photoluminecence. 
    • Typically caused by UV light which causes higher energy electon to drop into a vacant lower energy level (within 10-8 seconds) releasing energy in the form of electromagnetic radiation (light)
    • When UV in short wave (wavelength - 254nm) or long wave UV (wavelength = 366 nm) the mineral stops emitting light
  5. what colour is produced by Fe2+ + Ti4+?
  6. 5 types of cleavage and minerals associated with them
    • Cubic- galena
    • Octahedral - fluorite
    • rhombohedral - calcite
    • prismatic - amphiboles
    • pinacoidal/basal - micas
  7. Whats special about the hardness of Kyanite?
    • Scratch hardness varies substantially with direction and crystallographic planes.
    • -Scratch hardness = 5 along blades
    • -Scratch hardness = 7 across blades (edge shared are strongly bonded)

    Bladed crystals that are elongate parallel to chains of edge-sharing octahedra

    • -Triclinic mineral
    • Image Upload 1
  8. What is Vickers hardness?
    A quantitative measure of indentation hardness = load applied divided by the surface area of indentation
  9. What causes magnetism?
    what do electrons do?
    Caused by movement of electrons, where each electron may contain two electrons with opposite spins (spin quantum number)

    - Each spinning electon produces a magnetic field, whose bohr magnetic moment can be cancelled by adding an electron in the same orbital spinning in the opposite direction

    • - FerrImagnetriic ions have partially filled 3d electrion shells containing several unpaired elctrons. E.g MAGNETITE which has a net four electrons spinnig in one direction in the 3d electron orbital
    • BREF - Atoms ions in adjacent structural sites have antiparallel magnetic moments because of Exchange coupling.
  10. What are 4 magnietic minerals?
    • Magnetite
    • Chromite
    • Ilmentite
    • Pyrrhotite (variably magnetic as it is a omission solid solution)
  11. Talk about clevage
    example about crystal structure and cleavage
    • Symmetry of elvage must be consistent with minerals symmetry
    • is inherent to the structure of the crystal

    • Clevage surface need not be parallel to the crystal faces that a minetal may aquire when it grows.
    • e.g.
    • Halite and fluorite both isometric/ cubic crystal systems,
    • however halite has cubic cleavage planes  {001}
    • Fluorite has octahedral cleavageplanes {111}
  12. Cleavage of fluorite
    Cleavage of Halite
    • {111} Octahedral
    • {001} Cubic
  13. Define Mohs scale of hardness?
    A unitless 10-point scale with each hardness represented by a common material

    • Fingernail 2.5
    • gold,silver - 2.5~3
    • Copper penny - 3
    • Platinum 4-4.5
    • Iron 4-5
    • knife blade - 5.5
    • glass- 6-7
    • iron pyrite - 6.5
    • hardened steel file - 7+
  14. wavelenth of UV light that causes for photoluminecense
    • =254nm (shortwave UV)
    • =366nm (long wave UV)
Card Set
Physical properties of minerals (G) CH6
Physical properties of minerals