Heritage Stone Subcommission: A Global Perspective
The rejuvenated International Commission on Geoheritage is all set to unveil statues for designation of ‘Global Heritage Stone Resource’. The idea is to promote the heritage /natural stones with Outstanding Universal Value vis-à-vis their cultural, architectural, and Utilitarian parameters.
Our session deals with promoting heritage/natural stones of Outstanding Universal Value which contributed to the evolution of human culture and architecture from the entire world in agreement with the goals of the IUGS-ICG-HSS and IGCP HerSTONES project (2020-2024). The session invites papers on diverse themes such as the impact of heritage stones in the evolution of human cultures, architectural legacy, sustainability of historical quarries, preservation, and sustainable restoration of the urban and rural stone-built heritage.
Selected contributions from our previous EGU sessions were published in high impact factor journals, such as Geological Society of London Special Publications (SP407: Global Heritage Stone: Towards International Recognition of Building and Ornamental Stones), Episodes Special Issue on Heritage Stones (volume 38-2, June 2015), Geoscience Canada (volume 43(1), March 2016), Geoheritage (2018), Episodes (volume 44 (1) March 2021). Currently, the contributions from our session at EGU 2021 are in preparation for publication in the journal Geoheritage. Selected contributions of EGU 2022 will be considered for publication in a special issue of a well-rated journal.
Because of its ease of working in minute detail and its whiteness, gypsum alabaster was one of the preferred materials for European sculpture rivalling marble in the late Middle Ages and early modern period. Its natural deposits are spread all over Europe, from the English Midlands to the Ukraine, from the Ebro basin to Tuscany, from the Alps and the Jurassic to central Germany (Fig. 1). The close connection between natural alabaster deposits and artistic centres, which has emerged in recent work, is related to the ecological perspective currently much discussed in art history, which emphasises the convergence of nature and culture. This new approach is based on a combination of art historical, historical and natural scientific methods and has been employed in several research projects over the last decade, involving geologists, geochemists, art historians, and conservators in a network of heritage research institutions, geological surveys, and museums. Progressively, the links established by this transdisciplinary work between historical alabaster deposits and artworks outline the evolution of the networks of European “alabaster routes”, of transfer of unworked stone, art, artists and technical and artistic knowledge which confers to this heritage stone a unique role in European integration.
Here we present the current state of the art on prominent historical alabaster quarries, notably in France and Germany, and research perspectives in the framework of the upcoming Franco-German Materi-A-Net project co-funded by ANR and DFG.
Fig. 1 Principal alabaster deposits used for sculpture in Late Medieval and Early Modern times. Transdisciplinary network of the Materi-A-Net project.
How to cite:
Kloppmann, W., Leroux, L., Bromblet, P., Jugie, S., Le Pogam, P.-Y., and Lipinksa, A.: Alabaster, a millenary stone of European cultural heritage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10687, https://doi.org/10.5194/egusphere-egu22-10687, 2022.
The city of Ouro Preto, located in Minas Gerais, Brazil, a cultural heritage of humanity since 1980, has still preserved within its listed urban site, buildings built from the 18th century, when Brazil was still a Portuguese colony. In a geological context, it is certain that the city grew in the middle and is surrounded by mountain ranges formed by quartzite crests with some occurrence of schist and steatites in the regions of its valleys. Based on comparisons with other regions of the country, it can be stated that due to this particular geodiversity, the city stands out even from others in Minas Gerais, due to the volume and diversity of quartzite material used in its buildings. The architectural ensemble that served as the basis for the granting of the title by Unesco includes buildings and monuments with public, religious and private purposes, which make up a legacy of importance for the history of Minas Gerais and Brazil. The set built using quartzite material, however, inspires attention, since the artisanal process of extracting and processing the pieces did not take into account properties suitable for applications, which until then were little known. Taken from known areas around the city and located in the mountains known as Ouro Preto and Itacolomy, it appears that the process did not involve steps and procedures that are typical of quarries, especially those we know today. These rocks were, for the most part, collected both in the form of blocks and plates, later undergoing some kind of processing. The blocks were widely used as structuring elements, such as pillars and columns, door and window frames and the plates, used in external and internal coatings. With some frequency, blocks were also used in decorative elements in masonry, such as portals on church facades and even in sculptural art, with the production of elements that make up various building facades such as, for example, the former Chamber and Prison House, currently headquarters of the Museum of the Inconfidence. With a greater or lesser degree of detail, these works can also be seen in the nineteen churches and chapels inserted in the listed perimeter. Sculptural elements are also present in a good part of the various fountains built in different parts of the old city, among them, six individually listed and whose objective was to facilitate the supply of water to the city. With some rarity, compositions involving the use of schists and steatite in decorative arrangements with quartzites are observed. It is understood that the survey of information on the former extraction areas of these rocks, on the various types of applications and on the buildings that are part of this architectural set, as well as on their deterioration processes, will be of importance to support conservation actions of this cultural heritage.
How to cite:
Costa, A. and Boas, P.: Built cultural heritage of Ouro Preto, Brazil: an architectural legacy edified in quartzite stone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1901, https://doi.org/10.5194/egusphere-egu22-1901, 2022.
Solid brick is a very old construction material used in the construction of monuments and buildings, the manufacture of solid brick is essentially based on the use of terracotta, this used earth conditions the specific characteristics of the brick and its mechanics behavior and its lifespan in the monument.
In this work and recognizing the importance of characterizing the traditional building materials we plan to study some samples of solid bricks made and used during the Marinid dynasty recovered from the historic site of Chellah which is located in the named city of Rabat as a shared heritage in 2012 and also the solid bricks used in restoration to deduce the similarities and differences.
We will study them under an optical electron microscope and we will expose them to the X-ray diffraction and fluorescence tests, this will allow us to identify the pathologies and degradations of the two types of bricks and the origins of the materials used and their primary compositions.
How to cite:
Belhaj, S. and Belhaj, O. E.: Study and Comparison of Solid Bricks Used by Merinids and those For Restoration Within the Chellah Historical Site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2069, https://doi.org/10.5194/egusphere-egu22-2069, 2022.
Stone built heritage in conflict areas is increasingly at risk of accelerated deterioration, as explosive and ballistic damage not only create damage to the surface, but also inherently change the mineral fabric of the stone to deep within the structure. In particular, remotely detonated high-power explosive ordnance has become more accurate and economically viable for state forces, especially given the availability of remote-controlled military aircraft. Concurrently, armed non-state groups engaged in asymmetric warfare rely on (improvised) ground-based explosive devices, seen to devastating effect at high-profile sites like Palmyra.
Stone in historic buildings is pre-weakened through centuries/millennia of exposure to weathering, and may be particularly vulnerable to subsequent heat and shock waves generated by explosives. Whilst appearing unaltered externally, exposure to high-pressure explosive force can result in the growth of microfractures and loss of cohesion within the cement matrix of stone, potentially leading to fracturing and crumbling, particularly if such stones are load-bearing within a rebuilt structure. The loss of density associated with explosive damage is particularly problematic. We show that our preliminary testing of the effect of an 81 mm HE mortar bomb blast in the vicinity of sandstone structures indicates changes in rock surface hardness as well as complex fracturing of the surface. Both visible and non-visible damage were recorded using high speed cameras, rock surface hardness surveys pre- and post-detonation, and photogrammetry. We conclude that even if not directly exposed to an explosive blast, stonework can be inherently altered.
How to cite:
Mol, L., Brassey, C., and Cunliffe, E.: Mortar damage to stone built heritage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2694, https://doi.org/10.5194/egusphere-egu22-2694, 2022.
Stones and thus building stones are very rarely in the focus of public interest. Geologists working with building stones use every opportunity to interest and sensitize people to this topic. Natural stones have served as building stones since time immemorial and they can be found in almost every town and village right before our eyes. They only need to be made visible to the viewer. Besides the explanation of the rocks, their petrographic and mineralogical composition, contained fossils and structures, technical features as well as their weathering behavior, one can point out many other aspects. This includes the geology of the area, geological timetable, mining, processing, transportation and use in past times and today, as well as aspects of restoration. Many geologists took and take advantage of this opportunity for geological and cultural education. They have written natural stone guides for several cities and organize natural stone excursions through their cities.
The German network “Stones in the city” has compiled a bibliography on this topic, which is constantly updated (www.steine-in-der-stadt.de). The bibliography contains just over 1100 entries on publications of dimension stones in cities worldwide. The time frame of the recorded publications is between the middle of the 19th century and the current year. The focus of this bibliographic collection includes the subject area of European building and decorative stones with a view of cultural geology. Some interesting aspects about the natural stone guides are presented in evaluation of this bibliography.
How to cite:
Ehling, A. and Heinz, F.: Natural stones in the cities - an easy way to focus on rocks and geology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5310, https://doi.org/10.5194/egusphere-egu22-5310, 2022.
In Piedmont, where five main quarry districts can be recognized (Barale et al 2020), Maritime and Ligurian Alps, corresponding to the mountain area of southern Piedmont and characterized by a wide variety of marble and sedimentary carbonate rocks, includes the historic ‘Monregalese’ district (G.A.L. Mongioie, 2005).
Among the several varieties of “Monregalese” marble exploited in the past, Nero di Frabosa, Nero Nuvolato di Miroglio, Nero Vallone , Nero di Ormea and Nero di Garresio are black marble known and identified in Piedmont Cultural Heritage. These varieties of marble come from a small portion of the Mesozoic carbonate succession called Calcari di Rio di Nava and referable to the Middle Jurassic (Dogger). The entire stratigraphic series of the Brianzonese area consists of a limestone-dolomitic sequence of Trias, greater than 300 m in thickness, followed by pure Jurassic limestones (about 100 m thick) and Cretaceous marly-arenaceous limestones (thickness greater than 150 m). In the innermost sector of the Alpine chain, metamorphism and tectonic deformation were much more intense than in the outer portion. The result of this deformation is a high fragmentation of the entire stratigraphic succession with the formation of flakes and bands of carbonate rocks with sharply vertical geometries and small dimensions that alternate with the quartzites and metavulcanites of the base. The succession of Rio di Nava limestones consisting of dark limestones with abundant organic substance and the presence of levels rich in bioclasts, with an original thickness of about 50 meters, was affected by this metamorphic phase, originating the aforementioned Monregalese black marble varieties.
Nero di Frabosa has been employed in lower part of the Chapel of the Shroud (Turin), Vicoforte Sanctuary; Church of San Giorgio (Frabosa Sottana); Nero Nuvolato in the Mussocco cemetery (Milan), in the Church of San Madre di Dio (Turin); Nero Vallone in the Church of Santa Maria Assunta (Montaldo).
From the technical documents there are informations only on the employ in the past years of Nero Garessio (and none related to Nero di Ormea), characterized by numerous and thin white veins. Nero di Ormea differs from it for the darker color of the veins. All these black marble were used inside therefore their resistance to weathering is not well known. Only for Nero di Ormea, the last quarried one, there are data on ageing tests in order to assess their suitability to be used outside and not only for inner and aesthetical purpose.
How to cite:
Bellopede, R., Marini, P., Chiappino, C., and Vigna, B.: Different varieties of black marble from “Monregalese” district in Piedmont (Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8148, https://doi.org/10.5194/egusphere-egu22-8148, 2022.
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Marbles have been used for the beautification of cities, temples and palaces throughout history. These building stones are compositionally analogue but show differences in texture and colour that can be associated with some petrographic and petrophysical properties, which makes possible to identify their origin.
A variety of building marbles from Guarrazar archaeological site (Toledo, Spain) was investigated. This site was a monastic-palatial complex linked to the Spanish Visigoth kings. It is archaeologically significant because Guarrazar's treasure, composed of gold votive crowns and crosses of the 7th century, were found in this site and are preserved in the National Archaeological Museum of Spain, in the Armory of the Royal Palace of Madrid and in the Cluny Museum of Paris, France.
The marbles were characterised petrographically, with polarisation optical microscopy; mineralogically with XRD; petrophysically with ultrasound pulse velocity, Hg intrusion porosity and colour measurements and chemically with isotopic analysis, which is carried out by mass spectrometry. All these analyses were carried out to locate the historical quarries of the marbles used in the basilica of the Guarrazar archaeological site.
Most of the analysed samples were reused marbles from Roman structures. The calcitic marbles are white and pinkish, and some of them have an irregular distribution of small greyish veins. They are medium grained, showing grain sizes from 103 μm up to 1.75 mm, and an average value of 423 μm. Mercury intrusion porosity ranges between 0.77 and 0.42 %. The main type of marbles comes from Estremoz Anticline, Ossa-Morena Zone (Southern Branch of the European Variscides in Portugal), distant approximately 300 km from the site. This 40 km NW–SE structure has been mined intensively since the Roman Period.
Estremoz marble is designated as Global Heritage Stone Resource (GHSR) by Heritage Stones Subcommission of the International Union of Geological Sciences (IUGS) . This designation seeks international recognition of those natural stone resources that have achieved widespread utilization in human culture.
How to cite:
Freire-Lista, D., Santos, J. F., and Lopes, L.: Characterisation and Historical Quarries Location of Marbles from Guarrazar Archaeological Site (Toledo, Spain)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1268, https://doi.org/10.5194/egusphere-egu22-1268, 2022.
Iconic buildings in Iași City are an expression of the local geologic and geomorphologic settings, because building materials are locally procured. We analyse and highlight the reasons why this particular city – characterised by many emblematic buildings and a high potential in terms of building materials, may successfully develop its geotourism sector. A case study of the geotourism enhancement of the Repedea site as a source of construction and ornamental stone for some iconic buildings in Iasi City is presented. We want to argument that geotourism in Iasi city can be integrated as part of urban tourism. Its traditional sense, namely as the kind of tourism specific to such landscapes, should be understood as a catalyst of urban architecture and building materials. These explicitly reflects the local geomorphological and geological environment, thus being an important element of the trips that aim to offer the experience of a special place in the city.
How to cite:
Anastasiei, A.-M., Niacşu, L., and Enea, A.: The Geoheritage value of the iconic buildings of Iaşi City, Romania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8826, https://doi.org/10.5194/egusphere-egu22-8826, 2022.
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