In Situ Hyperspectral Raman Imaging of Ternesite Formation and Decomposition at High Temperatures
Round 1
Reviewer 1 Report
The here submitted paper, titled "In situ hyperspectral Raman imaging of ternesite formation at high temperatures" is well designed, written and organized. In this notable work, the Authors applied a quite novel approach to document and image the formation of ternesite at high temperatures. Even if few changes are required, I recommend the manuscript for publication, with minor revision.
- Chapter 1, line 2: typos "is is"
- Table 2: add some space between the rows, it should be easier to follow the cells along each line.
- I see that you have detected a peak at 95,4 cm-1: which filter did you use to remove the Rayleigh signal? Didn’t you write that you cut at 100 cm-1?
- If you have the chance, publish your in-house HT Raman spectra database, it would be useful to many.
- Fig. 2b: I think that this panel should be oriented as the companion 2a (with Raman shift on the X axis and temperature on the Y one) to facilitate the comparison between the two.
- How did you calculate the mineral fraction percentages in fig 5? You should mention why you couldn't perform some chemical and strictly quantitative analyses, such as EDS, and the advantages of Raman imaging.
- Chapter 3.4, line 361: 3 different fonts in this line
- Figure 7: Please, reorganize the figure. As it is now, the figure does not appear well structured but a little crowded; it it is not that easy to understand which comment is referred to which panel.
I would propose three columns:
RT1; HT1; comments to step 1.
RT2; HT2; comments to step 2.
RT3; HT3; comments to step 3.
… … …
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Review of the manuscript „In situ hyperspectral Raman imaging of ternesite formation at high temperatures” by Nadine Böhme, Kerstin Hauke, Thorsten Geisler and Manuela Neuroth.
The manuscript submitted for publication in “Minerals” was prepared on good scientific level and written on understandable language. The authors used Raman mapping to investigate phase transitions in the CaO-SiO2-CaSO4 system, previously, studding a changes of natural ternesite at high temperature by Raman spectroscopy. Used method of investigation is not precision procedure for determination of thermodynamic parameters of phase transformations, but it allows to estimate a temperature range of phase formation and stability. That information is important in geological reconstructions of pyrometamorphic rock formation and determination of sequence and temperature interval of phase stability in “cement systems”.
Small volume of studied material undoubtedly has effect on acceleration of mineral-forming process kinetics and relatively lower temperatures of phase transformations in comparison with mineral formation in Nature or clinker kilns.
I consider that the submitted manuscript contains original results of investigation and can be published in „Minerals”.
I have the following remarks and comments:
line 29-30: Ternesite (Ca5(SiO4)2SO4) has only been described so far from two localities worldwide (Mayen, Germany [1]; Negev Desert, Israel [2]).
This statement is not correct as ternesite was also found in the Judean Mts (Palestine) at Ma’ale Adummim, Jabel Harmun, Nabi Musa and Nahal Darga localities [2 – number of reference in the manuscript].
line 30-31: It is is isotypic to silicocarnotite (Ca5(PO4)2SiO4) and a number of other compounds, where Cd and Ge substituted Ca and Si, respectively [1].
Please, add reference [2], where ternesite was compared with silicocarnotite and add references on Cd and Ge ternesite analogs.
Figure 1d: A weak band no. 41 about 957 cm-1 is related to stretching symmetric vibrations in (PO4)3- [2]. This band is well visible in the ternesite spectrum from the RRUFF database (Fig.1a). An appearance of significant P2O5 impurities in ternesite heightens greatly its thermal stability.
Figure 8. I think that it is not quite fortunate using of the term „solid solution” for the mixture of ternesite and α’L-Ca2SiO4 as these two minerals do not form solid solution.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The topic of the paper is interesting and the paper is generally well written but requires some revisions.
The authors discuss gas fugacity and make assumptions on sulfur that are not validated. Moreover, no calculation of local partial pressure or even volume size of the furnace is provided. Also, no information of the atmosphere inside the furnace is given.
The authors proceed to conclude that:
"During quenching to RT, α’L-Ca2SiO4 transformed to β-Ca2SiO4 (larnite) or recrystallized to ternesite, whereby it seems to depend on reaction progress and the gas pressure and composition in the furnace whether ternesite or larnite was identified after quenching to RT."
Conclusions should be concrete and avoid speculation.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The authors changes their conclusion to be:
During quenching to RT, α’ L -Ca 2 SiO 4 transformed to β-Ca 2 SiO 4 (larnite) or recrystallized to ternesite, whereby it evidently depends on the reaction progress and "likely the gas pressure and composition in the furnace" whether ternesite or larnite was identified after quenching to RT.
The underlined statement is misleading as the authors did not track or study gas pressure in their work. This is not a conclusion from this particular work.
All other issues are resolved.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
