Physical properties of minerals (G) CH6

Mohs hardness (relative scale)

Indentation hardeness/ Vickers hardness number (absolute scale)

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

• -Presence of metal ions  (first row of transition elements ti-cu)
• -Intervalence charge transfer- metal ions in mixed oxidation states.

• 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

Green

• Cubic- galena
• Octahedral - fluorite
• rhombohedral - calcite
• prismatic - amphiboles
• pinacoidal/basal - micas

• 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

A quantitative measure of indentation hardness = load applied divided by the surface area of indentation

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.

• Magnetite
• Chromite
• Ilmentite
• Pyrrhotite (variably magnetic as it is a omission solid solution)

• 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}

• {111} Octahedral
• {001} Cubic

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+

• =254nm (shortwave UV)
• =366nm (long wave UV)