The most naturally abundant mineral to display piezoelectricity, colored varieties of it include citrine, agate, and amethyst.
At high temperatures, this mineral converts from its trigonal alpha structure to its hexagonal beta structure. Tiger's Eye, which is a pseudomorph of asbestos, is actually a variety of this mineral. It is mixed together with moganite in the mineral chalcedony. Its low crystallization temperature and felsic properties place it below muscovite and the orthoclase minerals at the bottom of Bowen's reaction series. The most naturally abundant mineral to display piezoelectricity, colored varieties of it include citrine, agate, and amethyst. Second only to the feldspars in abundance in the Earth's crust, for 10 points, name this mineral whose empirical formula is SiO2.
At high temperatures, this mineral converts from its trigonal alpha structure to its hexagonal beta structure.
quartz [prompt on silicates, silica, SiO2, or silicon dioxide]