Hornblende Mica Schist Raman Spectra (3)

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Rutile Goethite Calcite
 Spot E is a brownish material abundant in this rock section while spot D is a dark red-brown crystal of a minor mineral. A higher magnification image is reproduced below.
 
 Higher magnification image showing the color difference between both crystals D and E.
 
  Raman spectrum of spot D indicates clearly the presence of Rutile.  Rutile and Ilmenite detected previously confirm the presence of titanium in this rock.
 
The structure of the brownish material ( spot E) is elucidated by the Raman spectrum: it is made up of Calcite and Goethite. The detailed structure of  this two minerals assemblage is illustrated in the thin section images below.
 
 Enlarged (10X objective) thin section image showing a high interference color calcite material (pink or green depending on polarization vector) with embedded goethite veins. Depending on the precise position of the laser spot, calcite alone or a mixed spectrum of calcite and goethite can be obtained. The section shows also the low birefringence albite crystals and some highly colored muscovite.
 
Same view without analyzer inserted. The Goethite network is clearly visible.
 
 Another part of the thin section with the green-pink carbonate with goethite inserted in the fractures of the grains.

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