physical properties of minerals
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Physical Properties of Minerals. Physical Properties. Color of Minerals Idiochromatic color color caused by elements in chemical formula--Cu in malachite and azurite and Mn in rhodochrosite. Chromaphore color

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physical properties
Physical Properties
  • Color of Minerals
      • Idiochromatic color
        • color caused by elements in chemical formula--Cu in malachite and azurite and Mn in rhodochrosite
slide3
Chromaphore color
    • color caused by concentrations of elements not part of chemical formula--Cu and V in beryl (emerald), Fe in amethyst and V in zoisite (tanzanite)
slide4
Electron and Molecular Transitions
    • Colors caused by Idiochromatic and chromophore elements can be generated by
      • 1. Crystal field transitions
        • wavelengths of light are absorbed by “d” electrons in transition elements causing emissions of wavelengths of light quanta resulting in color of mineral---Cr+3 in emerald and ruby, Mn+2 in morganite and Fe+2 in peridot
slide5
2. Molecular Orbital Transitions
    • ions undergo charge transitions or electron hopping--Fe+2 to Fe+3 in aquamarine or Fe+2 to Ti+4 in sapphire
slide6
Inclusions of Other Minerals
    • minerals dispersed or included in minerals can influence color
      • chlorite dispersed in quartz (aventurine) can cause a green color
      • black calcite can be caused by inclusions of MnO2
      • red color in many minerals is caused by hematite inclusions
slide7
Mineral Properties Related to Light, Heat, and Electricity
    • Play of Colors (Iridescence)
      • defracted or reflected light off features on the mineral
        • labradorite and opal
slide8
Chatoyancy
    • silky or wavey appearance across the surface of the mineral as it is rotated--
slide9
Asterism
    • a star like figure on surface of mineral caused by reflected or scattered light off included minerals aligned parallel to crystallographic axes
slide10
Luminescence
      • caused by impurities (activators) in a mineral--some specimens of fluorite, scheelite, and calcite
    • Fluorescence
      • emission of wavelengths of light caused by electron excitation in metals during bombardment by ultraviolet or X-rays
    • Phosphorescence
      • continuous emission of wavelengths after excitation source is removed
  • Thermoluminescence
    • emissions of wavelengths when subjected to heat at less than “red hot” temperatures
slide11
Piezoelectricity
    • a flow of electrons in minerals with exertion of a compression force between the “c” crystallographic axis of a mineral which has no center of symmetry---quartz and tourmaline
  • Pyroelectricity
    • the same as above brought about by stimulation of mineral with heat--quartz and tourmaline
slide13
Hardness
    • Moh’s hardness scale is a special list of minerals with increasing relative hardness
      • 1. talc 6. feldspar
      • 2. gypsum 7. quartz
      • 3. calcite 8. topaz
      • 4. fluorite 9. corundum
      • 5. apatite 10. diamond
        • glass and knife = 5.5 - 6
        • steel file = 6 -7
        • fingernail = 2.5
        • penny = 3
        • some minerals have more than 1 hardness depending on the direction of scratching--kyanite= 5-7 and calcite between 2 and 3
slide14
Tenacity
    • cohesiveness of mineral or resistance to breaking, crushing, bending, etc.
      • 1. brittle--if a mineral powders easily--quartz
      • 2. malleable--if mineral can be hammered into sheets--native Cu, Au
slide15
sectile--if mineral can be cut into thin shavings--talc
  • ductile--if mineral can be drawn into wire--Cu, Au
  • flexable--if a mineral is bent and does not assume its’ original shape
  • elastic--if a mineral is bent and resumes its’ original shape--mica

talc

slide16
Streak and Luster
    • streak is the color of the powder of the mineral on a porcelain plate
    • luster is metallic (dark or black prominent streak--dense and opaque to light) or nonmetallic ( translucent or transparent with a colorless or white streak) or somewhat inbetween called submetallic
      • some specific nonmetallic lusters are:
        • 1.vitreous--resembling glass--quartz crystals
        • 2. resinous--resin like--sulfur and sphalerite
        • 3. pearly--mother of pearl like--talc
slide18
greasy--like grease or oil--massive quartz
  • silky--like silk--satin spar gyspum
  • adamantine--brillant with a high index of refraction--diamond or clear quartz crystals
slide19
Cleavage
    • ability of mineral to come apart in a consistent way
    • breakage is along atomic planes--consistent with crystal symmetry--- there can be from one to multidirectional cleavage from mineral to mineral
slide21
Parting
    • can resemble cleavage
    • breakage of minerals along planes of weakness such as twinning planes--minerals which grow around each other, each one forming at a different time
    • caused by minerals being subjected to special pressures during formation
  • Fracture
    • inability of a mineral to break in a consistent way
    • do not break along cleavage planes
slide22
Kinds of fracture are:
      • concoidal--smooth, curved breakage--quartz
      • fibrous or splintery
      • hackly--jagged with sharp edges
      • irregular--rough surfaces
  • Specific Gravity
    • a number expressing a ratio between a mineral and the weight of an equal volume of water
    • same number as density without units
    • S.G. depends on:
      • kinds of atoms (atomic weight) comprising mineral
      • packing of atoms(close or loosely packed)
slide23
S.G. can be determined with a Jolly Balance
  • Crystal Habits and Aggregates
    • appearance of a single crystal or aggregate of a crystals of a mineral
      • isolated individual crystals
        • bladed--elongated flattened crystal like a knife blade
        • acicular--thin needlelike crystal
        • capillary--hair like or thinner
slide25
groups of distinct crystals
    • dendritic--resembling a branching tree or veinlets on a tree leaf
    • radiated--crystal appearing in a radial pattern
    • drusy--a surface containing very small crystals

radiated--wavellite

slide26
groups of distinct crystals in parallel or spherical form
    • columnar--column like crystals
    • bladed--many flat knife like crystals
    • fibrous--parallel fibers
    • colloform--botryoidal (bunch of grapes, reniform (kidney shaped), mammillary

fibrous--crysotile (serpentine)

colloform--hematite

slide27
aggregate of scales or lamellae
    • foliated--easily splits into thin sheets or leaves
    • plumose--scaly-feather like
  • granular aggregate
    • equant crystal grains

equant granular mass- pyrite

foliated (micaceous)- mica

slide28
pisolitic or oolitic--rounded masses of pea sized grains (pisolitic) or very small grains( oolitic)---this picture is bauxite (pisolitic) and some samples of hematite occur as oolitic
  • Other types

stalactitic--resembling stalactites---this example is goethite-limonite

slide29
massive--massive with no form or distinguishing features

geode--rock cavity filling with mineral crystals

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