Quartz at pressure This image depicts the evolution of the crystal structure of quartz as a function of pressure. It is based upon the data of Glinneman et al (1992) from room pressure to 10.2 GPa and extrapolated to 25 GPa. The structure of quartz is observed to transform to glass at 25 GPa pressure and room temperature (Kingma et al, 1993). Notice that the corners of the tetrahedra (the O atoms) adopt a closest-packing of monolayers at the amorphization pressure. It can be assumed that the structure cannot be made denser by application of pressure after the anions are in this planar arrangement, so the structure then undergoes amorphization.