Experimental postshock temperatures for crystalline quartz released from shock states between 86 and 127 GPa and for fuset silica released from 59 to 73 GPa have been determined using previously measured spectral radiance data. The temperatures range from 3660 to 4150 K and are consistent with the interpretation based on shock temperature measurements, that the Hugoniot of SiO2 crosses the phase boundary between stishovite and liquid. The new postshock temperatures were used to determine the Gr¿neisen parameter of liquid silica at high pressures and temperatures and the specific volume of the release state (&ggr;/V=3.5 Mg/m3 and Fr=0.266 m3/Mg, respectively), although there is some ambiguity as to whether this volume corresponds to a partial or total release state. To show the validity of these postshock temperatures, a radiative transport model was extended to times after free surface arrival of the shock wave. ¿ American Geophysical Union 1988