Quartz solid solution crystals of six different compositions were obtained from crystallization of glass powders belonging to the Li2O-Al2O3-SiO2(LAS) system. They were analyzed in situ by laboratory-based X-ray diffraction down to cryogenic temperatures (-190 degrees C). Temperature-resolved analysis of their lattice parameters allowed determination of the critical inversion temperatureT(c)in these materials, marking the displacive phase transition from a high-quartz- to a low-quartz-like lattice. Integrating available data from other literature sources, an updated phase diagram for the occurrence of high and low quartz solid solution phases is provided for the LAS system; these data are expected to support future development of functional materials relying on these crystalline phases.