In light of recent discoveries of post-stishovite phases of SiO2, with the CaCl2 and α-PbO2 structures, we have reassigned the regimes along the Hugoniots for initial quartz, coesite, cristobalite, porous coesite, and fused silica. Calculated Hugoniots for fused silica, cristobalite and porous coesite indicate transition to stishovite, and then melt. Hugoniots for crystal quartz and coesite indicate that transition occurs to stishovite, then the CaCl2 structure and finally to melt.