Minero-Petrographic Characterization of Chianocco Marble Employed for Palazzo Madama Façade in Turin (Northwest Italy)

Round 1

Reviewer 1 Report

This paper aims to present a detailed petro-architectonic survey and a minero petrographic characterization of the Chianocco Marble and to outline the causes of its degradation. Authors attempted to explain the provenance and conservation state of the Palazzo Madama’s façade in Turin through a minero-petrographic study. While the findings of their study highlight some interesting details concerning the Palazzo Madama as a UNESCO world heritage site, there is still room to discuss how these findings can contribute to the development of a geological approach for the conservation of cultural world heritage sites (considering the nature of selected case study). Furthermore, the credibility of such an approach may enhance by comparing the results of Palazzo Madama’s façade with other relevant cases in Italy, like Tivoli or Livorno. 

Author Response

Point 1: This paper aims to present a detailed petro-architectonic survey and a minero petrographic characterization of the Chianocco Marble and to outline the causes of its degradation. Authors attempted to explain the provenance and conservation state of the Palazzo Madama’s façade in Turin through a minero-petrographic study. While the findings of their study highlight some interesting details concerning the Palazzo Madama as a UNESCO world heritage site, there is still room to discuss how these findings can contribute to the development of a geological approach for the conservation of cultural world heritage sites (considering the nature of selected case study). Furthermore, the credibility of such an approach may enhance by comparing the results of Palazzo Madama’s façade with other relevant cases in Italy, like Tivoli or Livorno.

Response 1: One of the purpose of this article consist in highlight that the peculiar vacuolar structure and local reddenings of Chianocco marble, usually absent in ornamental marbles, are primary features of the rock itself and are not due to degradation in an urban context (line 371).

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled “Minero-petrographic characterization of Chianocco Marble employed for Palazzo Madama façade in Turin (NW Italy)”, by Gambino et al., concerns the characterization of the Chianocco Marble used in Palazzo Madama. It is a simple study of petrographic and isotopic characterization of the materials with the addition of a “petro-architectonic relief” of the Palazzo Madama façade, with the indication of the different stones employed, and the addition of a model of the evolution of the rock from its formation to its employment.

The manuscript is written in a simple way and the English is quite good. The historical-architectonical context and the geological setting are exhaustively described. However, some points must be clarified, especially with regard to the petrographic section and the isotopic analysis. In particular: 

-         In the section 5.1 “Petrography” the authors said that “analyses have been conducted on façade samples and on outcrop ones” but no information about the façade samples are given. How many samples have been analyzed? Where were these samples taken from? I think that it is necessary to clarify the sampling of the façade and, maybe, to insert a figure or a table with the indication of the sampling points.

-         In the same section there are only the petrographic description of the samples coming from the site 3 and the Chianocco Marble, which I assume is a summarized description of the sites 1,2,4 and 5, even if it is not clear (I suggest to clarify this aspect). The description of the façade samples are missing. I think that for a comparison it is necessary to insert also the petrographic description of these samples.

-         Section: “C–O stable isotope analysis”. This part is not clear and should be better discussed. How many samples were analyzed? The samples coming from the 5 sites in the surroundings of Chianocco village and the façade samples have been all analyzed? Observing the δ18O/ δ13C diagram I understand that the isotope analysis was performed on the calcite and the dolomite of only 1 sample from the façade and only 1 sample form the Chianocco quarry. It is true? What samples did you choose? Why? I think that it is necessary to carry out a large number of analyses on all samples, and then report the average values on the diagram, or at least it is necessary to specify why you chose to analyze only few samples.

-         In the abstract (lines 19-21) the authors said that “A multi-analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe and stable isotope analyses was carried out …”. Maybe there is an error because in the section “materials and methods” the authors talk about: optical microscopy, cathodoluminescence, Scanning Electron Microscope equipped with EDX and stable isotope analyses. Results about the electron microprobe are not present.

Other minor suggestions are listed below:

-         Table 1 is not mentioned in the text;

-        Figure 7 and Figure 8 are inverted. The captions are correct but the figures must be reversed.

-         Line 65: break the words “recentconservation”;

-         Lines 104 and 105 are repeated in the lines 106 and 107;

-         Line 198: leave the space after “between”;

-         Line 231: the caption of the Figure 6g (“optical microscopo with only polarizer image”) is not correctly written;

-         Lines 265-266: “investigated” is twice written;

-         Lines 272 and 279: replace “employement” with “employment”;

Author Response

Point 1: In the section 5.1 “Petrography” the authors said that “analyses have been conducted on façade samples and on outcrop ones” but no information about the façade samples are given. How many samples have been analyzed? Where were these samples taken from? I think that it is necessary to clarify the sampling of the façade and, maybe, to insert a figure or a table with the indication of the sampling points.

Response 1: Specimens from façade were not sampled directly in situ but they consist of fragments detached from the summit balustrade. In the text we have better specified what is the material object of study and where it comes from (line 192).

Point 2: In the same section there are only the petrographic description of the samples coming from the site 3 and the Chianocco Marble, which I assume is a summarized description of the sites 1,2,4 and 5, even if it is not clear (I suggest to clarify this aspect). The description of the façade samples are missing. I think that for a comparison it is necessary to insert also the petrographic description of these samples.

Response 2: Petrographic description of the samples coming from the site 3 are firstly described, then, Chianocco Marble of site 1,2,4,5 were described. There is a unique petrographic characterization of Chianocco marble (from quarries and façade) because it is exactly the same material.

Point 3: Section: “C–O stable isotope analysis”. This part is not clear and should be better discussed. How many samples were analyzed? The samples coming from the 5 sites in the surroundings of Chianocco village and the façade samples have been all analyzed? Observing the δ18O/ δ13C diagram I understand that the isotope analysis was performed on the calcite and the dolomite of only 1 sample from the façade and only 1 sample form the Chianocco quarry. It is true? What samples did you choose? Why? I think that it is necessary to carry out a large number of analyses on all samples, and then report the average values on the diagram, or at least it is necessary to specify why you chose to analyze only few samples.

Response 3: C-O stable isotope analyses have been carried out on two selected samples of Chianocco Marble where the characteristic brecciated structure is best represented. One consists of a piece detached from the Palazzo Madama façade and the other comes from site 4, in the surroundings of Chianocco, village where the rock results analogous to the façade marble (line 289). In the manuscript it has been underlined that these analyses were not aimed to a complete archaeometric characterization and provenance of Palazzo Madama marble but only to verify the genetic relationships of calcite and dolomite which, on the basis of petrographic observations, are clearly not in equilibrium (line 292). 

Point 4: In the abstract (lines 19-21) the authors said that “A multi-analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe and stable isotope analyses was carried out …”. Maybe there is an error because in the section “materials and methods” the authors talk about: optical microscopy, cathodoluminescence, Scanning Electron Microscope equipped with EDX and stable isotope analyses. Results about the electron microprobe are not present.

Response 4: SEM-EDS analysis are mentioned and explained in the text (line 203, line 249, Table 2, 3, 4). Table 2 and 3 and Figure 8 concerning electron microprobe analysis of phengite and phlogopite have been added.

Author Response File: Author Response.pdf

Reviewer 3 Report

As far as we are talking about the  "minero-petrographic characterization", the paper is providing valuable information.

Using so advanced instrumental  techniques (as described), one can get more data, making adequate conclusions and  more rich comments  (e.g. about the mechanisms of damage, including chemistry of the processes).

This is what I would expect, and what can be done with the results already obtained.

Author Response

Point 1: Very interesting . This is a "minero-petrographic characterization". However, the methods used make it possible to discuss more physicochemical data.

Response 1: Discussing more physicochemical data may be an interesting starting point for a future work on the same field.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Please reconsider the following suggestions.

Line 46

Roman numerals for describing the century seems not to be appropriate here.

Lines 65-67

Please use the English equivalent for “Fondazione Torino Musei” and “Soprintendenza Archeologia, Belle Arti e Paesaggio per la Città metropolitana di Torino”

Line 103

The extra dot before the references should be removed.

Author Response

Point 1: Line 46

Roman numerals for describing the century seems not to be appropriate here.

XVII century has been replaced with “Eighteenth century”

Point 2: Lines 65-67

Please use the English equivalent for “Fondazione Torino Musei” and “Soprintendenza Archeologia, Belle Arti e Paesaggio per la Città metropolitana di Torino”

“Fondazione Torino Musei” has been replaced by “Foundation Torino Musei”

“Soprintendenza Archeologia, Belle Arti e Paesaggio per la Città metropolitana di Torino” has been replaced by Superintendence of Archeology, Fine Arts and Landscape for the Metropolitan City of Torino

 Point 3: Line 103

The extra dot before the references should be removed.

The extra dot before the references has been removed

Author Response File: Author Response.docx

Reviewer 2 Report

The authors modified the manuscript  improving legibility and clarifing all points. 

Author Response

Point 1: The authors modified the manuscript improving legibility and clarifing all points.

Thank you for the corrections

Author Response File: Author Response.docx