Emerald Deposits: A Review and Enhanced Classification
Round 1
Reviewer 1 Report
General comments
This is an excellent review about emerald deposits. The manuscript review the classification of emerald deposits and propose modifications to improve it based on genetic models, which take into account chemical, geochemical, isotopes and fluid and solid inclusion. The manuscript is well elaborated, however, I do some minor suggestions.
Specific comments
- In line 24-25 you said that most abundant deposit Type of emeralds, in terms of production, is pegmatite, but in the map of Figure 2 only one deposit of this type is represented, but many deposits of the other two types (?).
- Table 1. I suggest delete all rows that there are only “0”, such as Co2+, Ba2+ and Rb+ in the apfu files.
-line 1
- lines 171-176. The nomenclature of caption of Figure 6 is confused. You indicate that the number of analyses per country is given in brackets but it is in parentheses, isn’t it?. Why you use brecksts for a range of references and then other reference is isolated eg. [11–15], [16].
Figures 6-8 shold be more illustrative if in addition to the country you could indicate the type of deposits from the different emeralds plotted in the graphics.
Author Response
Dear Reviewer,
We have the pleasure to send to you the answers to your questions and to explain changes done (or not) in the ms. Thanks for your review.
REV. 1
Specific comments
- "In line 24-25 you said that most abundant deposit Type of emeralds, in terms of production, is pegmatite, but in the map of Figure 2 only one deposit of this type is represented, but many deposits of the other two types (?)."
We will modify by, now lines 24-28:
" The first and most abundant deposit Type, in terms of production, is the desilicated pegmatite related Type that formed via the interaction of metasomatic fluids with beryllium-rich pegmatites, or similar granitic bodies, that intruded into chromium- or vanadium-rich rocks such as ultramafic and volcanic rocks, or shales derived from those rocks. "
- "Table 1. I suggest delete all rows that there are only “0”, such as Co2+, Ba2+ and Rb+ in the apfu files."
We have deleted the row of Co and Ba. Rb2O is present for the analysis of emerald from one deposit (Lened with 0.14 wt. %) and in consequence the row will be not deleted
-"line 1"
???
- "lines 171-176. The nomenclature of caption of Figure 6 is confused. You indicate that the number of analyses per country is given in brackets but it is in parentheses, isn’t it?. Why you use brecksts for a range of references and then other reference is isolated eg. [11–15], [16]."
Changed to parentheses. The reason reference [16] is isolated is that the next few words (“average of 37 analyses”) refer only to it: “[11–15], [16] (average of 37 analyses)”.
"- Figures 6-8 should be more illustrative if in addition to the country you could indicate the type of deposits from the different emeralds plotted in the graphics."
A good idea but non-trivial to do and cannot be done within the five days allowed for revisions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is a great new proposal for a revised nomenclature that is comprehensively developed. The format for the citations need to be looked at though. I thought the Franz & Mortieani (2002) might have helped with this contribution. I have highlighted the things the authors should consider.
Excellent contribution.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
We thank you very much for your review and we have the pleasure to send to you the answers to your questions and changes done (or not) in the ms. Best regards. Giuliani et al.
REV. 2
This is a great new proposal for a revised nomenclature that is comprehensively developed. The format for the citations need to be looked at though. I thought the Franz & Morteani (2002) might have helped with this contribution. I have highlighted the things the authors should consider.
Answers to the questions:
We will include the important reference of Franz & Morteani (2002) that we unfortunately forgot previously at the pages, respectively, 48, 51, 52 and 62 (in the list of reference).
Franz, G.; Morteani, G. Be-minerals: Synthesis, stability, and occurrence in metamorphic rocks. In Beryllium: Mineralogy, petrology, and geochemistry; Grew, E.S., Ed.; Mineralogical Society of America: Washington, USA, 2002; Volume 50, pp. 551–589.
peer-review-3704126.v2.pdf
All the highlights drawn in the peer-review pdf will be corrected:
They correspond to very minor edit corrections more or less in all the pages.
The different citations that start a sentence will be modified as requested, as for example:
[1] said that.... by Barton [1] said that...
The corrections in the references chapter will be realized has indicated by Rev. 2.
Author Response File: Author Response.pdf
Reviewer 3 Report
Although part of the manuscript is a transposition from the In Color 2015, Special issue [65], the article is a powerful, comprehensive data collection, which allows assessing the state of knowledge of many emerald deposits in the world. Almost all the aspects are considered in this paper which concurs to give an important contribution both, i) to the debate on the genetic classification schemes of emerald deposits (that are widen respect to the existing schemes and which are important for provenance and international trade certification), and, ii) to the geological criteria (that open new perspective for emerald exploration guidelines).
Some minor revisions are as follow:
line 189: please add reference [23] after "ion microprobe" as Be has been analyzed by SIMS in emeralds reported in [23].
line 228: I suggest changing the present text in: processes since the Archean preserved metamorphosed mafic- ultramafic rocks (M-UMR)
line 230: I suggest to the authors to change the name of this paragraph “The Sources of Be, Cr, and V: the Paradoxes of Emerald” because the word Paradoxes is not appropriate to me. The formation of emerald requires a special condition, mainly governed by metasomatic processes, which favor the meet of Cr, V and Be even if in very different concentration in the crust. To this respect the authors could also briefly discuss about the main compositional differences between emerald and beryl.
lines 303-306: It is unclear to me to what exactly lines 303-306are referred; [61] is probably a wrong reference here as it seems not referred to the “… results of about 2600 spot analyses of 40 major and trace.......” Instead, where all these data come from??
line 1059-1061: there is some confusion here: the reference [138] is incorrect to me, probably the Authors would have liked to refer to [139]. Indeed, when the authors say that [52]……. "pointed out that pegmatites do occur in the Zentral gneiss and the Habactal emeralds contain up to 370 ppm of Cs " they probably refer to [139], Calligaro et al., 2000, which report 370ppm of Cs for the Habactal deposit. Moreover, [52] reports, probably erroneously, 760 ppm of Cs for Hababctal, instead of 370ppm
lines1393-1415 I found a bit weak the hypothesis to connect the three districts of Swat Valley (Pakistan), Santa Terezinha (Brazil) and Habactal (Austria) basing on the Na/Li vs Cs/Ga diagram from [65], reported in the manuscript as Fig. 39.
Moreover, in the caption of Fig 39, at the lines 1413-1415 I do not understand what means: “the Na content (wt %) of the emeralds for these three deposits (this work, [23])”…which are the Na contents reported “in this work”? Actually, the Na/Li ratios reported in the diagram of Fig. 39 do not completely correspond to those reported in [23]. In [23] it is shown that Cs contents are very different in the three districts and only Santa Teresinha has high Cs content, more compatible with a (magmatic) Be-Cs source. Also the LIL elements content differ significantly among the three districts, although they share similar Li and B contents.
I thing the importance of the Cs/Ga ratio should be better explained.
Author Response
Dear reviewer,
We thank you very much for your review and we have the pleasure to send to you the answers to your questions and changes done (or not) in the ms. Best regards. Giuliani et al.
REV. 3
Answers to the questions:
Some minor revisions are as follow:
line 189: "please add reference [23] after "ion microprobe" as Be has been analyzed by SIMS in emeralds reported in [23]."
Done, now line 204.
line 228: "I suggest changing the present text in: processes since the Archean preserved metamorphosed mafic- ultramafic rocks (M-UMR)"
We agree. Done, now line 244.
line 230: "I suggest to the authors to change the name of this paragraph “The Sources of Be, Cr, and V: the Paradoxes of Emerald” because the word Paradoxes is not appropriate to me. The formation of emerald requires a special condition, mainly governed by metasomatic processes, which favor the meet of Cr, V and Be even if in very different concentration in the crust. To this respect the authors could also briefly discuss about the main compositional differences between emerald and beryl."
We delete the term paradoxe from the title.
The new title is the following:
" 4. Sources of Be, Cr, and V: the Formation of Emerald
The sources of Be, Cr, and V of emerald. The Cr-V-bearing beryl is rare because..;"
now lines 233-234
"To this respect the authors could also briefly discuss about the main compositional differences between emerald and beryl."
We don't agree that we need more detail about the difference between beryl and emerald as We think this is covered quite well in section 3 (see lines 137 to 149).
lines 303-306: "It is unclear to me to what exactly lines 303-306 are referred; [61] is probably a wrong reference here as it seems not referred to the “… results of about 2600 spot analyses of 40 major and trace.......” Instead, where all these data come from??"
It was the wrong reference and it has been corrected. Now line 331
[61] Schwarz, D.; Klemm, L. Chemical signature of emerald. International Geological Congress, Abstracts. 2012, 34, 2812.
line 1059-1061:" there is some confusion here: the reference [138] is incorrect to me, probably the Authors would have liked to refer to [139].
Correct. Done, now line 1139.
Indeed, when the authors say that [52]……. "pointed out that pegmatites do occur in the Zentral gneiss and the Habachtal emeralds contain up to 370 ppm of Cs " they probably refer to [139], Calligaro et al., 2000, which report 370ppm of Cs for the Habachtal deposit. Moreover, [52] reports, probably erroneously, 760 ppm of Cs for Habachtal, instead of 370ppm."
Totally right for the error done by Zwaan [52].
lines1393-1415 "I found a bit weak the hypothesis to connect the three districts of Swat Valley (Pakistan), Santa Terezinha (Brazil) and Habachtal (Austria) basing on the Na/Li vs Cs/Ga diagram from [65], reported in the manuscript as Fig. 39. I think the importance of the Cs/Ga ratio should be better explained."
The Fig 39 realized from chemical data obtained by LA-ICP-MS at the Gübelin Institute and presented by Schwarz and Klemm (2012) [Ref 61 in the present ms] and published by Schwarz (2015) [Ref. 65 in the present ms] evidenced this clear overlapping of the chemical domain for the three deposits. Our discussion is based on these works.
"Moreover, in the caption of Fig 39, at the lines 1413-1415 I do not understand what means: “the Na content (wt %) of the emeralds for these three deposits (this work, [23])”…which are the Na contents reported “in this work”?
This sentence in the caption is deleted because there is no sense to discuss the relation between Na content in the structure and the relative content of H2O in the channels of the emeralds from the three deposits.
Scientifically, this sentence signifies that the high Na content of these emerald is well correlated with the high H2O content measured in the channels.
Actually, the Na/Li ratios reported in the diagram of Fig. 39 do not completely correspond to those reported in [23]. In [23] it is shown that Cs contents are very different in the three districts and only Santa Terezinha has high Cs content, more compatible with a (magmatic) Be-Cs source. Also the LIL elements content differ significantly among the three districts, although they share similar Li and B contents."
The data reported by [23] are from Aurisicchio et al. (2018) obtained by LA-ICP-MS. These data are different for several chemical elements (in ppm) with other published data especially by Schwarz and Klemm (2012) and Schwarz (2015) on the three concerned emerald deposits but also with emerald from other countries that we analysed in the present work and presented in Table 1. Some questioning about the quality of Aurisicchio and other authors analysis is questioned now.
So, the caption of figure 39 is modified as follow, now line 1526:
Figure 39. Cs/Ga versus Na/Li diagram of emeralds from Colombia, Nigeria, Russia, Pakistan, Austria, and Swat valley presented by Schwarz [65]. The diagram indicates that the chemical ratios of emerald from Santa Terezinha de Goiás (Brazil), Habachtal (Austria) and Swat valley (Pakistan) plot in the same population field. They are characterized by moderate to high Cs/Ga and very high Na/Li ratios. Discrepancies are observed for the concentrations of Cs and other elements when compared with the analysis presented by Aurisicchio et al. [23].
Author Response File: Author Response.pdf
