Journal
MINERALS
Volume 10, Issue 2, Pages -Publisher
MDPI
DOI: 10.3390/min10020115
Keywords
gypsum; bassanite; hemihydrate; anhydrite; dehydration; rehydration; phase transition; crystal defects; in situ Raman spectroscopy; Raman band width
Funding
- DFG [GSC 1013 SALSA]
Ask authors/readers for more resources
Even though being the subject of natural scientific research for many decades, the system CaSO4-H2O, consisting of the five crystalline phases gypsum, bassanite, and the anhydrites III, II, and I, has left many open questions for research. Raman spectroscopy was used because of its structural sensitivity and in situ measurement capability to obtain further insight by studying phase transitions in both ex situ and in situ experiments. The findings include significant contributions to the completeness and understanding of Raman spectroscopic data of the system. The dehydration path gypsum-bassanite-anhydrite III was shown to have strong parallels to a physical drying process, which depends on many parameters beyond the burning temperature. Raman band width determination was demonstrated to enable the quantitative discrimination of ff-bassanite and fi-bassanite as well as the postulated three sub-forms of anhydrite II (AII), which are all based on differences in crystallinity. In the latter case, the observed continuous structural variations over increasing burning temperatures were elucidated as a combination of decreasing surface areas and healing of crystal lattice defects. We propose an only two-fold sub-division of AII into reactive disordered AII and much less reactive crystalline AII with a transition temperature of 650 ffiC 50 K.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available