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SiO₂ is one of the most widely studied materials at high-energy-density conditions because of its use as a standard in shock experiments and because of its geophysical importance. SiO₂ is considered an archetype for the silicates that dominate terrestrial mantles so measuring its structure at the relevant pressures and temperatures is important to understanding rocky exoplanets. In this work, we quasi-isentropically (ramp) compressed SiO₂ to ~400 GPa and probed its phase using in situ x-ray diffraction at the Omega laser facility. Both fused silica and novaculite, a microcrystalline quartz, were studied.