ERE4.11 | Heritage Stone Subcommission: Natural stones and their relevance
Heritage Stone Subcommission: Natural stones and their relevance
Convener: Gurmeet Kaur | Co-conveners: Parminder KaurECSECS, Angela Ehling, Valentina Cetean, Luis Lopes
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
Hall X4
Posters virtual
| Attendance Tue, 16 Apr, 14:00–15:45 (CEST) | Display Tue, 16 Apr, 08:30–18:00
vHall X4
Tue, 16:15
Tue, 14:00
The International Union of Geological Sciences (IUGS) plays a vital role in recognizing the importance of certain stones in global architecture and culture trends. These stones may include marble, granite, limestone, sandstone, and others that have been used extensively in iconic monuments. Collaborations between geologists, archaeologists, architects, and historians are essential to comprehensively study the stones used in monuments. This interdisciplinary approach ensures a holistic understanding of their significance. The knowledge gained from studying historical stone use can also inform contemporary architecture and construction practices, promoting sustainable and culturally sensitive designs. Stone monuments require ongoing preservation efforts due to weathering, pollution, and other factors. Stone science helps identify appropriate conservation methods to protect these historical treasures.
In nutshell, the study of stones in stone-built monuments, their geological properties, and their impact on culture and architecture is a rich and multidisciplinary field that helps us appreciate the heritage of different civilizations and provides insights into sustainable resource management and architectural innovation. Encouraging research in stone science is crucial for preserving these valuable cultural and historical treasures for future generations.
The proceedings of the session will be subsequently published in reputed International Journal. The session is being organized under aegis of IUGS - Heritage Stone Subcommission.

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X4

Display time: Tue, 16 Apr 14:00–Tue, 16 Apr 18:00
Chairpersons: Gurmeet Kaur, Paola Marini
Wolfram Kloppmann, Arthur Acker, Lise Leroux, and Aleksandra Lipińska

Towards the end of the 16th century, the first known hints emerge that the Lorraine region, and in particular the archbishopric of Metz, was a source of alabaster for sculpture in the principalities and bishoprics of the western part of the Holy Roman Empire. In 1587, a list of available alabaster deposits to be used for the epitaph of Magdalena zur Lippe commissioned  by the Landgrave Georg I of Hessen-Darmstadt, mentions an alabaster quarry “in the land of Lorraine, four miles from Metz” exported as far as to Würzburg in present-day Northern Bavaria. Ten years later, Metz alabaster was ordered for the decoration of the Schnellenberg castle in Westphalia.  

Using geochemical fingerprinting, we found evidence that a common source of alabaster was used in the Metz region and further downstream, in the Mosel and Rhine valleys. Indeed, Alabaster was used broadly from the late 16th century onwards in the major episcopal towns Trier, Bonn and Cologne. We postulate that this “phantom quarry”, so far not identified in our isotopic database of historical European alabaster deposits, is identical with the one mentioned near Metz. Indeed, several alabaster-grade gypsum quarries, still mentioned in 19th century literature, could be found within a range of around 30 km around the town. We will present results of combined archival, geological and geochemical research, conducted in the framework of the Franco-German Materi-A-Net project ( co-funded by ANR and DFG within the FRAL program.

How to cite: Kloppmann, W., Acker, A., Leroux, L., and Lipińska, A.: Hunting a phantom quarry “four miles from Metz”: Transboundary trade of Lorraine alabaster in the 16th century , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15151,, 2024.

Antônio Gilberto Costa

Due to the action of intrinsic and extrinsic factors, such as mineralogical compositions, textures, weathering, climatic conditions and pollution in urban centers, constructions using stone that are part of a country's cultural heritage require permanent care for their preservation, which must involve collaboration between professionals from different areas of knowledge. The case presented here serves as an example of a conservation action developed after unprecedented work involving the participation of geologists and a biologist and confirms that an interdisciplinary approach is indeed essential to guarantee a holistic understanding of stone in buildings. The cultural asset treated consists of a sculptural set made up of twelve life-size statues, representing prophets. Produced between 1800 and 1805, the set was built using inhomogeneous steatite blocks, ranging from isotropic to anisotropic types and is part of a monument located in the city of Congonhas, Minas Gerais, Brazil. Recognized by UNESCO as a Cultural Heritage of Humanity, the complex suffers degradation of different types, with emphasis on the natural and recurring action of biological colonization, which motivated this interdisciplinary work. At the beginning of 2023, after twelve years without any intervention, the elements of the complex appeared almost completely taken over by biological colonization, which caused visible aesthetic degradation, compromising the religious function for which they were produced. Initially, a detailed macroscopic petrography of all the statues was carried out, seeking to identify the different textures present in the steatite blocks used, but also all types of stone degradation. In addition to biological colonization represented by the presence of cyanobacteria, algae and lichens, losses of pieces, black crusts, dissolutions, patinas and cracks were observed. Of the mentioned microorganisms, mainly whitish gray or greenish lichens were found, described as foliaceous and other whitish lichens forming crusts on the substrate and described as crustose. Algae without stems or leaves and showing colors varying between yellow, green and reddish brown were also observed, occurring in a subordinate manner in relation to lichens. Other forms, such as mosses, were observed filling cavities and developing along fissures and fractures in the stone, as well as in spaces between blocks and between the bases of statues. Following our assessments on the extent of degradation of the stone material and the respective degree of deterioration of the set of statues, procedures were adopted by the conservators of the company Grupo Oficina de Restauro aiming to combat microorganisms with applications of a biocide and 70% alcohol. Geological monitoring during the microorganism removal process, evaluating possible losses to the stone substrate, and a new macroscopic petrography carried out sixty days later confirmed the absence of new damage to the stone. In summary, the presence, especially of geologists, who know the properties of the stone materials present in buildings, particularly historic ones, was fundamental to the success of the conservation action, which must always have a multidisciplinary character.

How to cite: Costa, A. G.: Stone science and its importance for the adoption of conservation actions: an example of interdisciplinary work in Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4362,, 2024.

The Clauzetto stone and its presence in the built heritage of NE Italy.
Anna Frangipane
Luis Lopes, Jose Beltran, Esther Ontiveros, Noel Moreira, Maria Luisa Loza, and André Carneiro

Almadén de La Plata marble is located in Ossa-Morena Zone (Iberian Massif) and generated through Variscan metamorphism of Cambrian limestones, being exploited during the Roman period. They were used in a wide variety of ways, such as architectural elements and decoration, statuary, and epigraphic monuments. The quarries for these marbles did not reach the dimensions found in other places (i.e., Vila Verde de Ficalho, Rosal de la Frontera, Alconera, Fuenteheridos-Navahermosa and Aroche), where they were exploited until the 20th century and where they continue to be exploited (Estremoz, Trigaches, Viana do Alentejo) until our days. Perhaps for this reason, the Roman quarries have survived to this day with an exceptional state of conservation, allowing the perception of what a marble quarry would have been like in the Roman period, as well as the methods and techniques used in the extraction of blocks which can also be observed.

The geological area of Almadén de la Plata marble, which comprises two main ancient exploitation places (Cerro de Los Covachos Quarry, which was completely excavated and musealized for public exhibition, and the Cerro Loma de Los Castillejos quarry), is spatially limited, being located near the E-W direction suture zone between the Ossa-Morena Zone and South Portuguese Terrane.

The marbles appear in the foot-wall of a calco-silicate series, being predominantly calcitic, although there are also dolomite-rich marbles with sigificant input of silicate minerals. Silicate phases are commonly micas, quartz, diopside, plagioclase and olivine, among others, which indicates that they have been subjected to amphibolite facies metamorphism.

Studies by several authors reports that the marble of Almadén de la Plata reached western areas of the Baetica Roman province (for instance, have been included in a line of research on the monumentalization processes of the Roman towns of: Hispalis, Italica, Astigi, Celti, Carmo, Malaca, among others), but also in other mainland places, such as Segobriga (Saelices, Cuenca) and even cities located in the north African province of Mauretania Tingitana, like Thamusida and Banasa, in present-day Morocco.

On a separate note, we can consider that all occurrences of Palaeozoic marbles from the Ossa-Morena Zone in Portugal and Spain could perfectly be framed within the concept of Heritage Stone Province.

As far as we know, in the short term, no start of modern exploration of the Almadén de la Plata marbles is expected. Still, there are cases of recent application of them, for example there is a typical Almadén de la Plata street, famous for its cobblestone pavement, built by José Antonio Benítez, a local resident, that is tied to different historical events and Almaden’s way of life. In any case, the intensive use of this marble in hundreds of monuments, mainly during the Roman period, with the heritage burden associated with this use, makes Almaden de la Plata Marble, Seville Province – Spain,  an outstanding candidate for Heritage Stone.

Acknowledgments: This work is supported by national funding awarded by FCT - Foundation for Science and Technology, I.P., projects UIDB/04683/2020 and UIDP/04683/2020.

How to cite: Lopes, L., Beltran, J., Ontiveros, E., Moreira, N., Loza, M. L., and Carneiro, A.: Almadén de la Plata marble: a Heritage Stone Proposal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13508,, 2024.

Rossana Bellopede, Alessandro Borghi, Anna D'Atri, Francesca Gambino, Paola Marini, Luca Martire, Giovanna Dino, and Elena Storta

The Gassino Stone, the most widely used carbonate sedimentary rock in Torino until the XIX century, is also known as Calcare di Gassino or Gassino Marble (Borghi et al., 2014). It was quarried from the Torino Hill domain near Torino and its formation can be referred to the Eocene. It is a biocalcirudite containing mainly red algae, macroforaminifera, bivalves, echinoids, and locally abundant intraclasts of biocalcarenites.

Although it has not been exploited for a long time, its occurrence in the city is still considerable. Its uses began in the end of the 1600 till mid 1800 and was installed not only in the churches but also in the historical buildings in plinth, columns, fireplaces and furnishings (Campanino et al., 1991).

It is possible to find applications of this rock in many famous historical buildings of Torino and surroundings such as in the colonnade of the courtyard of the Rectorate of the Torino University, in the portal of Palazzo Carignano, on the façades of the Santa Cristina Church and of the Torino Town Hall of, and in the Basilica of Superga external columns.

In the interior it has been usually installed with polished finishes (for example in the San Lorenzo church in the center of Torino). This kind of surface finishes gives a brownish aspect to the stone, in addition to a sense of compactness. When instead the Gassino stone is installed outdoor, with increasing time of exposure, its colour turns white and the compactness decreases emphasizing the presence of nodules consisting of calcareous red algae and intraclasts surrounded by thin clay seams. The portal of  Palazzo Carignano  represents the best example of the differential decay of this kind of stone outdoors, while the holy eater font in San Lorenzo church is the perfect example of optimal maintenance indoors.

How to cite: Bellopede, R., Borghi, A., D'Atri, A., Gambino, F., Marini, P., Martire, L., Dino, G., and Storta, E.: The Gassino stone in the architecture of Torino (Italy): different features for different uses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17550,, 2024.

Gurmeet Kaur

The importance of natural stones in architecture and cultural decoding is being acknowledged by the International Union of Geological Sciences (IUGS). Through its global designation ‘IUGS-Heritage Stone', a natural stone that has been extensively used by humanity for the proliferation of cultures and traditions in the past is based on certain criteria, giving visibility to these significant natural stones. The UNESCO-IGCP Project has been instrumental in funding our projects on Heritage stones for the past ten years. The outcome is amazing, with 32 IUGS designated Heritage Stones and 18 more in pipeline awaiting designation. The Heritage stones widely utilized in monuments with significant cultural inference are being designated through a proper procedure designed by the International Commission on Geoheritage of the International Union of Geological Sciences. The need of the hour is to take along geologists, archaeologists, architects, historians, policymakers, and the masses to preserve the stones and monuments that are custodians of our cultural evolution. This multidisciplinary approach guarantees a comprehensive comprehension of their importance.

In summary, the rich and multidisciplinary field of studying stones in stone-built monuments, their geological characteristics, and their effects on culture and architecture aids in our appreciation of the legacy of many civilizations and offers insights into innovative architecture and sustainable resource management (one of the sustainable development goals of UNESCO). Promoting stone science research is essential to safeguarding these priceless historical and cultural artefacts for future generations.

How to cite: Kaur, G.: Heritage Stones: IUGS Designation and its relevance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14896,, 2024.

Paola Marini, Rossana Bellopede, Adriano Fiorucci, and Ilaria Orlandella

The church of San Lorenzo is a ducal chapel located in one the main squares of Torino, whose costruction was due to a promises of the Duke of  Savoia Emanuele Filiberto for its safe after the San Quintino battle won in the day of San Lorenzo in 1557. The expansion works on the church actually began in 1634, but were soon interrupted by the death of Vittorio Amedeo (1637) and the resulting civil war, and only thirty years later, with the call of the mathematician Guarino Guarini, the church construction moved on to the resolution phase. For the dome he renewed schemes with a distant ancestry in Gothic and especially oriental architecture. The works for S. Lorenzo lasted a long time: the church was completed by 1679 and consecrated later only after the architect also designed the main altar.

The innovation of the Church of San Lorenzo is certainly the rich variety of decorative stones that we can admire inside and above all the different methods of use that Guarini managed to implement, changing the intended use, and introducing other particular stones which were, at the time, still unknown in Italy.

The main stones used inside the church, are the different types of Frabosa marble, San Martino marble, Foresto marble, Gassino limestone (Piedmont) and Arzo marble (Switzerland) while in the seven chapels, a very large use of Verde Alpi marble, , together with the bright Giallo Reale in contrast with the two blacks, from Frabosa and Portovenere are present.. The use of a different stone for each imposing pair of columns of the various chapels was also sought after, in this regard the green Alpi, the black Portoro, the Rosso Verona but also the breccia of Seravezza, the Gialletto of Verona and the particular Sicilian Libeccio of Custonaci were used.

Furthermore, from the analysis of the different altar frontals the triumph of the charm of different polychrome marbles, assembled excellently together, in a space of limited dimensions is evident.

Verde Alpi and Giallo Reale together with Arabescato Orobico and Spanish Broccatello, are all in great contrast by the black Frabosa marble.

Petrographic knowledge is fundamental in providing the tools for the preservation of cultural heritage as it allows us to carry out recovery interventions on architectural complexes and ancient art objects, having full knowledge of the material on which we are working, being able to proceed with the restoration or a possible replacement of part of the material, preserving its history, origin and characteristics.

In San Lorenzo the enormous wealth of stones will certainly remain a treasure to be protected over time and the possibility of being able to study their history and lithological provenance remains the most interesting aspect of the work I have carried out.

How to cite: Marini, P., Bellopede, R., Fiorucci, A., and Orlandella, I.: San Lorenzo Church in Turin– A stone exhibition of more than 3 centuries ago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15902,, 2024.

Lisa Bruzzone, Laura Gaggero, Alessandro Zucchiatti, and Judit Molera

The presence of elements associated with cobalt in historical enamels provides relevant information on the minerals used to produce them and their origin.
Starting from around 1520 we witnessed the systematic appearance of arsenic in blue enamels produced in the Mediterranean. Until this date and starting from the 15th century, an arsenic-free cobalt pigment was used instead.
The chemical composition of the two glazes is however compatible, showing in both cases the presence of Ni, Fe, Zn associated with Co.
Both pigments may have been produced using the same cobalt and arsenic minerals: erythrite, smaltite and skutterudite coming from the Erzgebirge region (Gratuze et al., 1996; Soulier et al., 1996). Then, the absence of arsenic in one of the two glazes could be attributable to different production processes like the roasting of the ores, which was used to produce saffron, or to the utilize of different fluxes employed to make the glaze, two cobalt by-products that began to be produced in the Erzgebirge mining district starting from the 16th century (Meltzer, 1716).

Recent studies on skutterudite thermal behaviour (Molera et al., 2021) revealed the difficulty of completely removing arsenic from the mineral, however it cannot be excluded that this element can be more easily removed from other minerals with Co/As ratio greater than 1:3.

This study aimed to replicate historical saffron and enamel recipes on erythrite and clinosafflorite to evaluate the loss of arsenic in the final products.
Several roasting experiments, reaching temperatures up to 1020°C, were performed on mineralogical samples from Bou Azzer (Morocco), even using different fluxes and studying the products obtained through different techniques (XRD, XRF, SEM-EDS). Some diffractions were performed during heating using synchrotron radiation.

With these treatments arsenic was not completely eliminated, but cobalt phases with reduced arsenic content were often obtained. The presence of calcium, sodium, and lead promotes the formation of different arsenates inside the glaze.
Heating clinosafflorite powders up to 1020°C resulted in the formation of cobalt-rich phases and As-Co-Fe-Ca phases. A mixture of CaO and borax with erythrite heated up to 900°C allowed to obtain Co-Fe-Ni oxides and Ca-Co-Na-Ni arsenates. Clinosafflorite roasted with quartz and ash promoted the formation of arsenic-free cobalt phases. The reaction and blue colouring of a quartz grain and the formation of different phases of Co-Na-Ca silicates, Co-Fe-Ni phases and different types of arsenates were obtained by heating clinisafflorite with borax at 1020°C.

Gratuze, B., Soulier, I., Blet, M., Vallauri, L. (1996): De l’origine du cobalt: du verre à la céramique. Revue d’archèometrìe, 20.
Meltzer, C. (1716): Historia Schneebergensis Renovata. Das ist: Erneuerte Stadt- u. Berg-Chronica Der im Ober-Ertz-Gebürge des belobten Meißens gelegenen Wohl-löbl. Freyen Berg-Stadt Schneeberg.
Molera, J., Climent-Font, A., Garcia, G., Pradell, T., Vallcorba, O., Zucchiatti, A. (2021): Experimental study of historical processing of cobalt arsenide ore for colouring glazes (15 16th century Europe). Journal of Archeological science: reports 36.
Soulier, I., Gratuze, B., Barrandon, J.N. (1996): The origin of cobalt blue pigments in French glass from the bronze age to the eighteen century. Revue d’Archéométrie, 20. 


How to cite: Bruzzone, L., Gaggero, L., Zucchiatti, A., and Molera, J.: Cobalt enamels through time: arsenic's influence and removal in historical production techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18704,, 2024.

Mehmet Özkul, Arzu Gul, Tamer Koralay, Hülya Özen, Barış Semiz, and Bahadır Duman

Global heritage stones are natural stones that have been widely used in historical buildings and monuments in the past (hundreds of years, even thousands of years) and are still used and today traded at the national and international level. The aim of this study was to evaluate the characteristics of being a global heritage stone of Quaternary travertines, which are common in the Denizli Basin in Western Türkiye.

The Denizli Travertine, is a widely used as a building stone in the Denizli Basin, from the 2nd century BC in the ancient cities of Hierapolis, Laodicea, Tripolis and Colassae that were the leading settlements of the region. Hierapolis/Pamukkale takes place in the of UNESCO World Heritage list and the First 100 IUGS Geological Heritage Sites. The travertine-dominated buildings have given a privileged feature to the aforementioned ancient cities. In these ancient cities, public buildings such as theatre, agora, bath basilica, monumental fountain, bridge and fortification walls were predominantly built using travertine. Use of the travertine also continued in the buildings of Seljuk period (eg, caravanserai, castle walls) from the 13th century.

Some exposures of the Denizli Travertine of Quaternary age observed in different parts of the Denizli Basin take place either very close to or under the ancient cities. In light and dark colors, their textural properties are extended to a wide range. The main texture types are peloid, bacterial/crystalline dendrite, coated grain, mostly wackestone to packstone, a small amount of grainstone containing plant-derived components. Another type is banded travertine, which occurs as a fissure fill or vein, has a completely crystalline texture and is mostly used for decorative purposes.

Travertines of the region, which were operated for thousands of years, received a geographical indication in 2008 with the name of ‘Denizli Travertine’. Today, it is widely used in many areas such as flooring, wall covering, stair step, countertop, table, coffee table and sculpture. The Denizli Travertine is exported to many countries (e.g. USA, UK, European Union and Middle East countries) both blocks and processed products like slab, tiles, mosaic, etc.). The travertine, which has been widely used in the region in the past, is traded worldwide for the last few decades.

How to cite: Özkul, M., Gul, A., Koralay, T., Özen, H., Semiz, B., and Duman, B.: Denizli Travertine: A Heritage Stone Resource from Western Türkiye , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21803,, 2024.

Posters virtual: Tue, 16 Apr, 14:00–15:45 | vHall X4

Display time: Tue, 16 Apr 08:30–Tue, 16 Apr 18:00
Chairpersons: Nuria Castro, Luis Lopes
Nuria Castro, Maria Heloisa Frasca, Antonio Gilberto Costa, and Rosana Elisa C. Silva

Brazilian marble production and exports have grown in the last few years, following the trend of the international stone market to commercially exploit the uniqueness of natural stone as a competitive factor. Natural stone companies are spreading over the territory, in the country of exotic silicate rocks, searching for carbonate ones. It would seem that industrial marble production in Brazil is relatively new. Still, it started in the 19th century, achieving its heyday during the 20th century, followed by progressive decay as technology allowed the exploitation of abundant and more resistant granites. National marbles were used both in new constructions and in old buildings' reforms. Therefore, many heritage buildings in the country are dressed in ‘unknown’ or misidentified marbles. This work intends to give publicity to those materials, outlining the chronology of marble production in Brazil based on extensive bibliographic research and fieldwork. This story begins in the last quarter of the 19th century, when Brazil attracted many skilled European immigrants, primarily Italian, with knowledge of marble and technology, and several carbonate rocks had already been discovered in the country. The first mechanized marble quarries opened around 1870 in the state of Rio Grande do Sul to exploit Neoproterozoic whitish blueish marbles used in several monuments, such as the Conde Porto Alegre statue and, probably, the Municipal Palace, both in Porto Alegre city. Those quarries did not prosper due to the scarce infrastructure and skilled labour. The railway was the real booster for the Brazilian marble industry at the end of the century. As the railways expanded from the capital, new deposits were discovered, and already known others became profitable. That is the case of precambrian black, white and pink marbles of the Itupararanga quarries in São Paulo (ca 1895-1914)  used in the Municipal Theater. Also, the proximity to the railway allowed the success of the quarry, regarded as the first in the country, which opened in 1915 in Mar de Espanha, Minas Gerais. This compact white marble of the Juiz de Fora Complex (2,1 Ga) was called “National White Marble”, a name afterwards given to the one quarried in Italva (produced since 1933) and today to the white of Espírito Santo (produced since 1957). All those white marbles and the one from Paraná were used to build Brasília, the country’s capital. In Minas Gerais, too, in Lagoa Santa, important quarries of various coloured limestones and marbles supplied tiles and ornaments between 1925 and 1980 and cobblestone (still produced) for traditional Portuguese pavement to the whole country. Other representative marbles of that time are the 2,4 Ga Gandarella Formation beautiful red, white, bardiglio and mottled (oncolites) dolomitic marbles that ornament the Caraça Sanctuary and many buildings in Rio de Janeiro and other cities, as does the 2,1 Ga stromatolic meta-dolomite of Ouro Preto. Many other marble quarries opened from then on, being just a few active today (e.g. Santa Catarina, Paraná, Espírito Santo), but the industry movement towards marble quarrying could give adequate materials for heritage restoration.

How to cite: Castro, N., Frasca, M. H., Costa, A. G., and Silva, R. E. C.: The heritage unknown Brazilian marbles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20567,, 2024.

Siham Belhaj, Omaima Esssaad Belhaj, Aziz Rhffari, and Boutaina Erraoui

The mâristân of Sala, better known under the names of Funduq Askour or Dar el Qadi is an ancient medical school located in Sala, Morocco, which was built during the Marinid era in the mid-14th century. In turn mâristân (hospital or hospice), foundouq (caravanserai) then sharia court, it ended up being transformed into a traditional music museum.
The mâristân of Sala was built according to Andalusian architecture, in this work we will dissect the architectural layout of the building firstly then we will identify the traditional construction materials that exist on the site such as calcarenite stone, zellige, wood, to then identify the damage that has affected these materials as well as their production processes.

How to cite: Belhaj, S., Belhaj, O. E., Rhffari, A., and Erraoui, B.: Identification of deterioration factors and diagnosis of the “Dar lqadi” or “Bîmâristân de Sala” facade, Sala, Morocco., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13460,, 2024.

Historical Quarries of Sandstones in Barichara and Guasca, Sources of Colombian Heritage Buildings
Javier Eduardo Becerra Becerra, David Martín Freire-Lista, and Andrés Felipe Ospina Enciso
Laura Damas Mollá, Arantza Aranburu, Arantxa Bodego, Iñaki Yusta, Martin Ladron de Guevara, Andrey Ilin, Iñaki Antiguedad, and Jesus Angel Uriarte

Black Markina is a limestone that has been exploited for more than 100 years as an ornamental and construction stone in the Basque Country (Spain). This stone is of great international interest and is well known for the intense black colour it acquires when it is polished. Nevertheless, in natural outcrops and in construction elements with other finishes the colour that characterises it is more or less dark greyish. 

The Markina Limestone Formation is located in the Basque Arc, to the north of the Basque-Cantabrian Basin. It was formed on a shallow subtropical carbonate marine platform during the Aptian/Albian. The main facies are biomicrites with a dark micritic matrix containing abundant fossils that contrast with the white colour: tabular corals in life position, as well as branching and hemispherical corals and Chondrodonta sp. colonies, rudists and gastropods. These facies are well stratified and sometimes a certain degree of transport is observed. Among these facies, those with few carbonate bioclasts and abundant orbitolines (binders) stand out. These facies correspond to the most commercially valued stone variety due to its more homogeneous black tone. 

The origin of the intense black colour of this lithology has not been resolved: on the one hand, the existence of organic matter disseminated in the matrix (on a microscopic scale) and in the interior of the fossils in the form of masses of pseudovitreous appearance (opaque under the optical microscope) has been confirmed. This organic matter already gives the matrix a dark basic tone. On the other hand, the presence of certain minerals such as nanometric magnetite or cubic and framboidal pyrite disseminated in the matrix, smaller than a micron in size, could be what intensifies the black colour when polished. 

The variety of ornamental stone known as Black Markina florid corresponds to facies with diagenetic features, mainly white, contrasting with the intense black of the matrix. In this sense, a generalised recrystallisation/neomorphism of the fossil remains is recognised and different late fracture systems filled with white calcite crystals also stand out. 

Markina village is an example of the use of local stone as a distinctive feature that defines its landscape. Numerous palaces (Ansotegi, 16th century; Gaitan de Ayala or Patrokua, 17th and 20th centuries), religious buildings (Church of La Merced, 18th century) and other architectural elements such as the sculpture in homage to Juan Antonio Moguel (20th century) or the cobblestones of several streets in the municipality have been preserved. Black Markina can also be recognised in elements from other countries as emblematic as the hall of the Empire State Building or the lectern of the United Nations headquarters, both located in New York, or the Kaaba of Mecca (Saudi Arabia). 

How to cite: Damas Mollá, L., Aranburu, A., Bodego, A., Yusta, I., Ladron de Guevara, M., Ilin, A., Antiguedad, I., and Uriarte, J. A.: Black Markina: an ornamental basque limestone (Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19481,, 2024.