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Article
Peer-Review Record

Rare Earth Element and Incompatible Trace Element Abundances in Emeralds Reveal Their Formation Environments

Minerals 2021, 11(5), 513; https://doi.org/10.3390/min11050513
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Minerals 2021, 11(5), 513; https://doi.org/10.3390/min11050513
Received: 29 April 2021 / Revised: 6 May 2021 / Accepted: 11 May 2021 / Published: 13 May 2021
(This article belongs to the Special Issue 10th Anniversary of Minerals: Frontiers of Mineral Science)

Round 1

Reviewer 1 Report

Line 43 “use” should be “used” or this sentence needs to be modified further

Line 157 should “class” be “glass”?

Line 323 “that” should be “than”

Line 350 “while” should be “whereas”

Line 455 “this is this is” should be “this is”

Lines 524-525 “candidates fluid sources.” should be “candidates for fluid sources.”

Line 569 “in Earth’s” might better be “in the Earth’s”

Line 579 “while” should be “whereas”

Line 648 “surface provide” should be “surface to provide”

 

Author Response

We thank the reviewer 1 for their corrections, covered below and are delighted they found the manuscript to be in good order.

Line 43 “use” should be “used” or this sentence needs to be modified further

Thank you - this was poor sentence structure on our part. Changed to: "and to enable use of this mineral variety more widely to understand geological processes"

Line 157 should “class” be “glass”?

Class here is correct. We are referring to the quality of the air (Class 10) in the laminar flow hood used for digestion and dry down of samples (very clean!).

Line 323 “that” should be “than”

Again, thanks. We modified the sentence structure to be "a trace element that can be used to identify contaminated samples."

Line 350 “while” should be “whereas”

Wording changed as suggested.

Line 455 “this is this is” should be “this is”

Thank you for the catch. Corrected.

Lines 524-525 “candidates fluid sources.” should be “candidates for fluid sources.”

Word 'for' added.

Line 569 “in Earth’s” might better be “in the Earth’s”

Word 'the' added.

Line 579 “while” should be “whereas”

Word while changed to whereas.

Line 648 “surface provide” should be “surface to provide”

Changed as suggested. Thank you.

 

Reviewer 2 Report

The paper is a fine study and analytically well done but has rather ambitious geodynamic goals which based upon the present data and their discussion can hardly be fulfilled, because specimens from a collection are fine but not enough. A common proverb of (economic) geologists is: Don´t try and create a new orogeny with only one hand specimen:

It starts with the element Be in itself  which is only treated with regard to the “anomalous” point of view of a gemstone. If you deal with the “extraordinary” you must use the “ordinary” as a platform to start off from. Realms where Be is concentrated at a level of economic importance see below:

  • Magmatic beryllium deposits
    • Beryl-emerald-euclase-hambergite-bearing granite pegmatites
    • Taaffeite-and emerald-bearing skarns
    • Replacement deposits in volcaniclastic deposits and granites
    • Be-bearing alkaline intrusive rocks (nepheline syenite)
    • Tugtupite-bearing alkaline intrusions
    • Chrysoberyl within rare element pegmatites
    • Beryl-bearing pegmatoids
  • Structure-related beryllium deposits
    • Aquamarine veins
  • Sedimentary beryllium deposits
    • Regolith-hosted emerald deposits (gemstone)
    • Alluvial-fluvial chrysoberyl placer
    • Black shale-hosted emerald deposits (gemstone)
  • Metamorphic beryllium deposits
    • Schist-related emerald deposits with or without pegmatitic mobilizates (gemstone)
    • Chrysoberyl in pegmatitic mobilizates in the contact zone of
      • Metaultrabasic rocks
      • Metapelites

Even associated Be-bearing gemstones such as chrysoberyl etc. are cast aside. With chemical fingerprinting alone a geodynamic assignment can never be achieved. It sounds smart in theory but is of little importance in practice. Therefore, I encourage the authors to supplement and support their chemical dataset not only by a comparison with other chemical data but embed them into what they are striving for into the geodynamic settings and geological-mineralogical-petrological environments. Otherwise these nice data may end up in a “flying carpet”.

I have to direct your view to the following reviews and comprehensive studies which might help you achieve thes goals.

  1. DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology  from  aluminum  to zirconium.- Earth Science Reviews, 100: 1-420.
  2. DILL, H.G. and WEBER, B. (2013)  Gemstones and geosciences in space and time. Digital maps to the „Chessboard classification scheme of mineral deposits“.- Earth Science Reviews , 127: 262-299 plus supplementary material (99 maps showing gemstone deposits by country, geology and geomorphology) related to this article to be found on-line at http://dx.doi.org/10.1016/j.earscirev.2013.07.006.
  3. DILL, H.G. (2015) Pegmatites and aplites: Their genetic and applied ore geology.- Ore Geology Reviews 69: 417-561.

  

Author Response

We thank the reviewer for their comments. We did an English language and style check (also covered in review 1's comments).

The paper is a fine study and analytically well done but has rather ambitious geodynamic goals which based upon the present data and their discussion can hardly be fulfilled, because specimens from a collection are fine but not enough. A common proverb of (economic) geologists is: Don´t try and create a new orogeny with only one hand specimen:

We are most grateful to the reviewer for their supportive comments. However, for their criticism, we respectfully disagree that we overstretch. This is not a study of an individual hand specimen; it is a study of key global emerald deposits worldwide. In this sense, the proverb mentioned by the reviewer is misleading. Notwithstanding, we think that we understand the context and attempt to address the reviewer's comments, below.

It starts with the element Be in itself  which is only treated with regard to the “anomalous” point of view of a gemstone. If you deal with the “extraordinary” you must use the “ordinary” as a platform to start off from. Realms where Be is concentrated at a level of economic importance see below:

  • Magmatic beryllium deposits
    • Beryl-emerald-euclase-hambergite-bearing granite pegmatites
    • Taaffeite-and emerald-bearing skarns
    • Replacement deposits in volcaniclastic deposits and granites
    • Be-bearing alkaline intrusive rocks (nepheline syenite)
    • Tugtupite-bearing alkaline intrusions
    • Chrysoberyl within rare element pegmatites
    • Beryl-bearing pegmatoids
  • Structure-related beryllium deposits
    • Aquamarine veins
  • Sedimentary beryllium deposits
    • Regolith-hosted emerald deposits (gemstone)
    • Alluvial-fluvial chrysoberyl placer
    • Black shale-hosted emerald deposits (gemstone)
  • Metamorphic beryllium deposits
    • Schist-related emerald deposits with or without pegmatitic mobilizates (gemstone)
    • Chrysoberyl in pegmatitic mobilizates in the contact zone of
      • Metaultrabasic rocks
      • Metapelite

We agree, these are all important minerals and mineral associations, no question. Just as measuring isotopic variations in emeralds will be important in the future, these are not particularly relevant to our existing discussion, although we mention aspects of this succinctly in Section 4.4.

Even associated Be-bearing gemstones such as chrysoberyl etc. are cast aside.

We are focused here on emerald, and mean no disrespect to the multitude of other Be-rich minerals, all of which have important stories to tell. We try to emphasize this even more in the manuscript where we discuss this issue (Section 4.4) and cite papers appropriate to these issues.

With chemical fingerprinting alone a geodynamic assignment can never be achieved. It sounds smart in theory but is of little importance in practice. Therefore, I encourage the authors to supplement and support their chemical dataset not only by a comparison with other chemical data but embed them into what they are striving for into the geodynamic settings and geological-mineralogical-petrological environments. Otherwise these nice data may end up in a “flying carpet”.

The manuscript goes through the logic of demonstrating unusual REE signatures in Type IA emeralds (80% of the world's emerald deposits, no less) and then places them into context with other major gemstones. In this sense, we feel we strike a good balance. We do not attempt a geodynamic assignment, but rather place emphasis on deposit origin and the implications this might have for the formation of emeralds.

We are not sure what the author of this review means by 'comparison with other chemical data', but we assume it refers to study of other Be-rich minerals, from the papers (by a single author) listed below. This is not part of our paper; it is focused on assessing emeralds in detail for the first time for their REE and other trace element abundances.

We are also unsure what a 'flying carpet' might be. Data is data, and we stand by the quality of it, even if our hypothesis is modified by good science in the future. In this sense, the reviewers comments could equally be leveled at any multitude of study of diamonds, rubies, sapphires, or even the two to the three (the 2nd one is a comprehensive listing of locations) comprehensive studies quoted below.

I have to direct your view to the following reviews and comprehensive studies which might help you achieve thes goals.

  1. DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology  from  aluminum  to zirconium.- Earth Science Reviews, 100: 1-420.
  2. DILL, H.G. and WEBER, B. (2013)  Gemstones and geosciences in space and time. Digital maps to the „Chessboard classification scheme of mineral deposits“.- Earth Science Reviews , 127: 262-299 plus supplementary material (99 maps showing gemstone deposits by country, geology and geomorphology) related to this article to be found on-line at http://dx.doi.org/10.1016/j.earscirev.2013.07.006.
  3. DILL, H.G. (2015) Pegmatites and aplites: Their genetic and applied ore geology.- Ore Geology Reviews 69: 417-561.

We thank the reviewer for these suggestions. We have previously read the first of these papers, but we thank the reviewer for pointing out the other two. On reading them, we two of the three in the revision to support our arguments.

 

Round 2

Reviewer 2 Report

The paper is in good shape and ready for publication

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