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  1. High Pressure Silicates

    Linked via "Post-Stishovite (P-S)"

    The ambient pressure mineral quartz-($\text{SiO}_2$) transforms into Stishovite at approximately 8–12 $\text{GPa}$. Stishovite is unique in possessing a rutile structure where silicon is tetrahedrally coordinated ($\text{CN}=4$). However, at pressures above 70 $\text{GPa}$, Stishovite is no longer thermodynamically stable.
    The transition from Stishovite to the denser phase, often termed Post-Stishovite (P-S), involves a coordination change to $\text{CN}=6$ ([octahedral symmetry](/entr…

  2. High Pressure Silicates

    Linked via "Post-Stishovite (P-S)"

    | Quartz | $\text{SiO}_2$ | $< 1$ | 4 | 2.65 |
    | Stishovite | $\text{SiO}_2$ | $1.2 - 70$ | 4 | 4.29 |
    | Post-Stishovite (P-S) | $\text{SiO}_2$ | $> 70$ | 6 | $\approx 4.8$ |
    | Wadsleyite | $(\text{Mg},\text{Fe})2\text{SiO}4$ | $< 530$ (Transition Zone) | Variable | $3.4 - 3.8$ |
    | Bridgmanite | $(\text{Mg},\text{Fe})\text{SiO}_3$ | $24 - 120$ (Lower Mantle) | 6 | $4.0 - 4.4$ |