Synthesis of quartz from high purity silicon dioxide and doping of various impurities

Association of silica phases as geothermobarometer for eucrites: Implication for two‐stage thermal metamorphism in the eucritic crust

“…Therefore, those agents enhance the transformation reaction. In our crystallization experiments (EX-01 and EX-02), the initially crystallized silica was eucritic cristobalite, which may contain impurities not as much as those in the above experiments, suggesting that their transformation to quartz is more sluggish compared with the previous experiments (such as 14 days at 840°C; Jin et al 2003). Therefore, we conclude that cristobalite in EX-01 remains intact during cooling, while cristobalite only in EX-02 can partially transform to quartz because EX-02 takes enough time (3 months) to disgorge impurities from cristobalite compared with EX-01 (16 days).…”

“…1978) and by the heating experiment of cristobalite with the coexistence of Li ion (˜600 ppm) at 840 °C for 14 days (Jin et al. 2003). However, no reports of simultaneous crystallization of cristobalite and quartz are present so far.…”

“…quartz) are also present such as hydrothermal alteration experiments at 250°C (Matsuhisa et al 1978) and by the heating experiment of cristobalite with the coexistence of Li ion (~600 ppm) at 840°C for 14 days (Jin et al 2003). However, no reports of simultaneous crystallization of cristobalite and quartz are present so The reason EX-01 contains only cristobalite is below: Previous transformation experiments were performed with the aid of a "mineralizing agent" or flux such as water or Li ion (Matsuhisa et al 1978;Jin et al 2003). Jin et al (2003) suggested that Li ion reacts with Al in cristobalite to form quartz and Li-Al compound.…”

“…However, no reports of simultaneous crystallization of cristobalite and quartz are present so The reason EX-01 contains only cristobalite is below: Previous transformation experiments were performed with the aid of a "mineralizing agent" or flux such as water or Li ion (Matsuhisa et al 1978;Jin et al 2003). Jin et al (2003) suggested that Li ion reacts with Al in cristobalite to form quartz and Li-Al compound. Disgorging impurities such as Al (and Na) using the agents is needed to transform to quartz because cristobalite commonly contains abundant impurities (Al, Na, and K) at roughly 10 times higher compared to quartz, while quartz cannot contain such abundant impurities (Heaney 1994).…”

“…Tridymite transforms to cristobalite by eliminating cation impurities fixed in tridymite (Fl€ orke 1956). Cristobalite transformed to quartz by removing impurities (Jin et al 2003). Quartz does not directly convert to tridymite by temperature increase due to a lack of impurities (e.g., Mosesman and Pitzer 1941;Madden and Van Vlack 1967).…”