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Eduncle posted an MCQ
October 18, 2019 • 17:09 pm 0 points
  • IIT JAM
  • Geology (GG)

The change in coordination number of silicon (Si) when a-quartz transforms to stishovite, which has octahedral coordination, is

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    Eduncle Best Answer

    The coordination number of stishovite is 6, so the silicon atoms are all surrounded by 6 oxygen atoms. The crystal structure of stishovite does not fit in the classification scheme of silicates, so stishovite could well be considered a non-silicate. Stishovite and coesite are both not stable at normal pressures and normal temperatures, but since their transitions into a low pressure silica polymorphs are reconstructive phase transitions that involve a complete rearrangement of the atoms in the crystal lattice, both are metastable at normal conditions.

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