Disintegration of Six Different Quartz Types during Heating to 1600 °C

This work investigates the high temperature behavior of six different quartz types A, B, C, D, F and G during heating to elevated temperatures. These quartz types contain different amounts of impurities, from 1% to 0.1%, and have earlier shown different degree of disintegration during heating. Melting experiments to 1750 °C have been performed to find softening and melting temperatures, and it is found that there are significant variations between the different quartz types. A higher content of impurities lowers the softening and melting temperature. The quartz surface has also been studied during heating to 1600 °C in a high temperature confocal microscope. From this, it is found that disintegration mainly happens at two temperature intervals, ~300–600 °C and ~1300–1600 °C, and is mostly due to volume changes in either the SiO2 matrix or the impurity areas. The cracks occur from impurity areas, expanding grain boundaries, damaged or uneven SiO2 surface and in some cases from the cavities from the escaped fluid inclusions.