SPINEL, KALSILITE, CLINOPYROXENE AND OLIVINE by

spectroscopy (XEDS) was used to not only confirm MgO phase, but also to determine the
orientations of the inclusions. Those MgO inclusions had the same crystallographic
orientation with spinel, which led to a complication in analysis of X-ray diffraction data.
After confirmation of the phase and the orientations of the inclusions, the spinel was
characterized without the inclusions by extracting the amount of intensity contributed by
MgO from the observed overall intensity.
A series of experiments were carried out to investigate a source of large oxygen
displacement parameters in kalsilite (APPENDIX B). A crystal (K0.88Na0.10)(Al0.94Si1.02
Fe 3+ 0.04)O4 from San Venanzo, Italy, was examined at room temperature as well as
cryogenic temperatures, 254, 223, and 100 K. The isotropic displacement parameters of
all the atoms decreased significantly from room temperature to 223 K, below which they
stayed constant. The change in the isotropic displacement parameter is most significant
for O1 where the parameter stayed large even at 100 K (Uiso = 0.035 Å 2 ), indicating that
large displacement parameters observed at room temperature resulted from both dynamic
and positional disorder. On the other hand, the change in the isotropic displacement
parameter was also significant for potassium atom, but the value below 223 K was small
(Uiso = 0.01 Å 2 ), indicating only dynamic disorder. Because the X-ray intensity data of
this sample suggested that the structure had a higher symmetry than that reported in the
literature, the structure was examined for more detail. Since an apparent higher symmetry
is often caused by a twinning, the refinement was carried out assuming that the structure
displayed merohedral twinning. The refinement converged with reasonable agreement
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