Basalt thin section areas 1 and 2, crossed polars and plane
feldspar labradorite, magnetite and alteration products like amphiboles.
is the high birefringence color augite.
Area 2 is an alteration material. The
spectrum is very similar to the one obtained on an altered olivine seen
in a gabbro. Possibly the crystal enclosed in the augite was originally
olivine. The spectrum does not give a single determination. It is a
hydrated material which could be amphiboles (hastingsite) but the
spectrum is also close to montmorillonite.
The low birefringence twined
material in area 3 is the feldspar labradorite.
Basalt area 4:
Plane polarized view.
Spectrum in area 4 is forsterite. Note the green
alteration product which fills up nearly entirely the olivine particle.
It is the same for another green particle on the left.
Area 5 and 6: large augite crystal with inclusions.
Spectrum 6 is
augite. The high birefringence filiform inclusion gives a spectrum
of augite with an additional peak which could be attributed to magnesite.
It is of course difficult to be certain of this determination with only
one peak but magnesite was the only matching mineral.
Basalt opaque minerals: area 9 magnetite.
with reduced power laser is magnetite which shows some signs of
oxidation if the power is increased.