Some Complementary Data about the Spectroscopic Properties of Manganese Ions in Spodumene Crystals
Round 1
Reviewer 1 Report
Czaja et al. report a very in depth and detailed study on the color change of pink and colorless spodumene after irradiation. They report that irradiated spodumene crystals that turn pink have an emission band at 591 nm while natural pink spodumene (kunzite) has an emission band at 625 nm. This is a nice study and has presented some nice results on the origin of color in natural and irradiated spodumene crystals.
Some general comments, there are quite a few typos (extra parentheses strange spacings or no spaces between words etc.) as well as confusing grammar.
Below are some line by line comments on the manuscript
Line 24 italicize c in c-axis
Line 31 I think I would provide a brief description of what the quadratic elongation and angle variance are and reconsider the number of significant figures you are reporting for both QE and AV numbers. Moreover, did you calculate these from a reported structure, and if so, what is the reference?
Line 33 also significant figures on the distortion index number you are reporting
Line 41 I would rephrase this to say “There are varietal names for the common colors of spodumene such as…” I also strongly discourage the use of varietal names in any scientific publication since these do not come under the jurisdiction of the IMA or the CNMMN and in my opinion can cause confusion.
Line 48 the grammar in this sentence is confusing
Line 64 To reiterate my point from line 41, I strongly encourage the authors to read the following reference on the history of the varietal name hiddenite
Tacker, R. C. (2010). “Real” Hiddenite and Real Names. Rocks & Minerals, 85(3), 264-271.
“Hiddenite is a gemstone variety that is not rigidly defined, part of the fluid world of economics, supply and demand, and sales and marketing. As much as I love the history contained in varietal names, I prefer the virtue of clarity found in the IMA nomenclature.”
Moreover, Wise (2006) discusses the geology of “true” Hiddenite deposits and discusses that the distinction between “true” hiddenite and other green varieties of spodumene is significant and is based on differences in coloring agents and mode of formation etc.
Wise, M. A. (2006). Geology of “True” Hiddenite Deposits. The Quarterly Journal of the Gemological Institute of America, 152.
Line 77 there is an open parenthesis in front of [20,21]
Line 119 Were the irradiated crystals heated in air or in some inert atmosphere?
Line 120 there is a “v” in between 14 and were
Line 134 you mean from not form?
Table 1 in lines 104-106 you mention that 2 spodumene crystals were studied but in the table there are 4 listed?
Line 157 I know you mention the temperature and duration you heated the samples to in the methods section but I think it is still useful to just state the temp in the text when discussing the heated results, and the same comment on line 158
Line 159 do the authors mean after X-ray exposure? And on line 160 they become colored? What color?
Table 2 it appears that the symbols for the bands did not render properly?
Line 256 change an to and
Line 266-268 Same comment as line 157
Line 274 Is the strong Jahn-Teller distortion the only explanation? What if the Mn3+ emission band is close to the Fe absorption band then you would not likely observe the Mn3+ emission band
Line 289 Same comment as line 157
Line 311 I am not sure that this is the correct way to reference this, perhaps reference the mineral spectroscopy server at Caltech and specifically rhodochrosite
Figure 4c do you have an explanation for why the 690 band disappears after the sample has been irradiated? Does it re-appear after heating?
Line 326, I think you need to be more clear here with respect to the comment that bond lengths change due to X-rays. The study that is referenced specifically states that after “intense” x-ray irradiation and that bond length dilation was found to be X-ray dose dependent. They exposed their samples to intense X-rays for as long as 20 hours… you mention on line 150 that the doses of X-ray used in this study are negligibly small so this comparison is not fair. Has it been shown that X-ray irradiation at the doses in this study can cause bond length dilation?
Line 331 did you do any single-crystal X-ray diffraction of the irradiated samples to obtain bond lengths? Or any other technique to obtain bond lengths? Or is this all inferred from your spectroscopic results?
Lines 325-331 Is quite speculative, what is the evidence for the increase in the Mn-O bond lengths after irradiation? Figure 4c? the shifting of the luminescence band to shorter wavelengths? Interestingly in figure 2c it appears that after irradiation and heating the luminescence bands are observed at longer wavelengths than before any treatment, I either missed the discussion or this was not discussed by the authors in this manuscript. What is the reason for this? The irradiation causes a lengthening of the Mn-O bonds and the heating causes relaxation and a shortening of the Mn-O bonds?
Line 336 confusing English, what is meant by …crystal site of tetragonal a of low symmetry,…”
Line 338 do you mean present? And change indicated to observed
Table 3 the symbols for green ??irradiated did not render properly
Line 354-362 this section would greatly benefit from a diagram of the crystallographic site and how the tetragonal distortion in the Mn3+ site is determined from [Dq(z)/Dq(xy)]^1/5.
Line 373 you state that the presented results and those from Ito et al. show that Mn3+ can occupy a site with either monoclinic or tetragonal symmetry, but on line 359-362 you stat that Mn3+ does not occupy a site with tetragonal symmetry? Which one is it? Either the discussion is confusing and not easy to follow, or the authors have contradicted themselves?
Line 387 did you mean to list another band here, so the lower symmetry site split the excitation band into 428 cm-1 and XXX cm-1?
Line 387 Do you mean that the LiO6 octahedron has a larger volume and is more distorted than the AlO6 octahedron? the language is imprecise here.
Conclusions
- Can the authors be specific on the does and duration of X-ray radiation. Also the spodumene crystals do not change their color to green, the color of the spodumene crystals changes to green after X-ray irradiation
- Again dose and duration of radiation and temperature and duration of heating need to be included in this conclusion statement. Do the authors attribute the color change from pink to green entirely to the change in valence of Mn? What about Fe? All og the samples have Fe in them… samples 13 and 14 have more Fe than Mn for example. So does Fe play a role in this process at all?
- you have shown that the color change from pink to green is easy under a specific set of circumstances. Use more descriptive language here, you have not shown that you can easily change the color to yellow or blue or red, so this statement is a bit misleading at best.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
As few minor wording issues which need to be corrected such as:
Line 48: "are be most important to explain"
Line 139 " Mn content was 0.X%"
Line 159: " X-ray exposition"
More details is required in section 3.2:
It is mentioned that radiation doses were lower than other studies but no values for the doses were given. Does the the photon energy of the radiation affect the investigation - x-rays vs Gamma? Why was the sample heated to 250C after irradiation?
The colour of the samples is mentioned frequently but no quantitative measure of the colour is given or considered. As one of the key issues the work is focused on is "the problem of color change during irradiation and heating" some more quantitative measure of the colour (reflectance spectra etc?) would be beneficial.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
