Phonolite Raman

                         Wide field thin section of this rock

 

           Phonolite thin section areas 1,2 and 3.

          Main minerals of this section are olivine fayalite, augite, feldspar orthoclase, altered olivine to iddingsite and magnetite.

 

     The crystal in area 3 is the iron rich olivine fayalite.

    

      The small green crystals (area 2) spread everywhere in this rock are augite.
     The main component of this phonolite rock is the feldspar orthoclase.
 

             Phonolite area 4 Iddingsite

         The red crystal in area 4 exhibits a low signal to noise Raman spectra. No reference spectrum has been found for comparison. Its color suggests an olivine crystal altered  to Iddingsite, an hydrous silicate of Mg and Fe.
 

            The big crystal in area 5 is again the feldspar orthoclase.

 

          Area 6 is augite.

 

 

                     Opaques minerals: magnetite.

     Reflection view of the section. The opaque mineral has a high reflectance and appears thus white in this plane polarized image.

     Above is the reflection image between crossed polars. The material in area 7 is black and isotropic.

     The power of the helium neon laser has been limited by a grey filter of absorbance 0.6 to avoid oxidation of the opaque minerals. The blue spectrum is magnetite. If the full power laser is used, the material is oxidized and gives an hematite like spectrum.