Ignimbrite from Italy. Raman spectra.

                             Wide field thin section of this rock.

 

    Raman spectra of a thin section of an Ignimbrite from Italy. Areas 1 to 5.

    Diopside, Anorthoclase, Labradorite, Biotite, Enstatite, Ferrosilite.

   The bright interference colored material in areas 1 and 2 is diopside. Spectrum 2 has additional features not identified. Some small peaks coming from the glue are also present in particular around 1600 cm-1.
  The feldspars Anorthoclase and Labradorite have been identified in spectra 3 and 5.
  The highly pleochroic Biotite is present in areas 4 and 6.
   

         Areas 6 and 7.

 

    The mineral in area 6 is highly pleochroic as can be seen in the figure below.

  Comparison of the Raman spectra of Enstatite and Ferrosilite.
 

                        Opaques minerals: kaersutite and magnetite areas 8 and 9.

 

     As can be seen in the picture above (transmission image between crossed polars), the mineral in area 8 is not completely opaque but deep brown colored. The spectrum on the left could be interpreted as kaersutite a brown amphibole.

   The dark well formed crystal in area 9 is magnetite. The laser power in  the blue spectrum on the left has been reduced to avoid oxidation. Red curve is recorded with the full power of the laser, it shows oxidation peaks. Even with the reduced power, spectrum indicates some sign of oxidation maybe present in the crystal before exposure to the laser.