Hydrothermal recrystallization and transformation of tridymite

✍ Scribed by O. W. Flörke; K. Langer

• Publisher: Springer
• Year: 1972
• Tongue: English
• Weight: 519 KB
• Volume: 36
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00371433

✦ Synopsis

Well ordered tridymites containing atmost 0.016% Na (0.004% Na) were prepared at 1400~ from Na2WOd-(K2WOd-) fluxes using high purity amorphous silica as starting material. No further reduction of these Na-contents was attainable by soxhlet extraction. These tridymites were treated hydrothermally at temperatures between 815 and 950~ and 200 bars H20. The products obtained were investigated optically as well as by powder X-ray methods and were analyzed for Na-contents: the hydrothermal treatment resulted either in recrystMlization of tridymite or transformation into quartz mostly depending on INTa-contents. lga-contents below about 0.015% tend to favour recrystMlization of tridymite within the quartz field (< 870~ Na-contents above about 0.03% tend to favour formation of quartz within the tridymite field ( > 870 ~ C). This may be due to influences of Na-traces either on the kinetics or on the equilibrium temperature of tridymite-quartz transformation.