Characterization of İscehisar Andesite (Afyonkarahisar-Turkey), Used as a Building Stone Source of Historical Heritages from Ancient Times to the Present

Abstract

Most historical structures that have survived to the present day are constructed from natural stones. One such natural stone is andesite. This study conducted a series of characterization studies on andesites used as building stones in Afyonkarahisar (Turkey). The building stones in question were determined by the petrographic-mineralogical (polarizing microscope, XRD, SEM), chemical, pore diameter distribution, and physico-mechanical properties. Although the İscehisar andesite is not as well-known as the İscehisar marble, it is a volcanic rock widely used in cultural heritage sites such as mosques, fountains, and bridges that have survived from the Seljuk and Ottoman periods to the present day in Afyonkarahisar. Despite the presence of pink, brown, and gray-black colors in the İscehisar andesite, it is evident that the preference in historical buildings is mainly for gray-black variants. Andesite, marble, and limestone, such as İscehisar Bridge from the Hellenistic period, Kırkgöz Bridge from the Byzantine era, Altıgöz Bridge from the Seljuk period, and Kanlı Göl Bridge from the Ottoman period, were used together in various combinations. Mosques are another group of structures in which andesite and other volcanic rocks are heavily used, such as bridges. While tuff is commonly used in examples of Seljuk and Ottoman architecture that have survived to the present day, andesite and other volcanic rocks along with bricks have also been used to construct dozens of mosques. Andesites found in the İscehisar region continue to be widely extracted, cut, and shaped using different surface processing techniques and are used today.

Introduction

The İscehisar andesite is one of the most commonly found building stones in the Afyonkarahisar (Turkey) region. It has been a significant construction material for thousands of years owing to its abundant availability and ease of processing. During the Hellenistic period, between 321 − 301 BC, a city named Dokimeion (Docimium, Dokimeia) was founded in the present-day İscehisar (Afyonkarahisar) by Dokimos, the governor of Synnada (Şuhut) and a commander of the Macedonian military, who was one of Alexander the Great’s generals. The significance of Dokimeion increased because of the marble quarries in its vicinity. Marble quarries of various colors and patterns, including white, gray, yellow, and marble with purple veins, played a crucial role in their operation. Parallel to the advancing civilization of the Roman era, marble quarrying and sculpture flourished in Dokimeion (Koch 2001). Starting from the Augustan period (40 BC-AD 14), Romans began to operate marble quarries, and numerous sculptor workshops became active in the city. Because Dokimeion was very close to the marble quarries, it became a center where sculptors of the time gathered. Marble blocks and columns of various sizes produced in the Dokimeion marble quarries are sent to numerous cities from Greece to Rome. As a result, there were quarry and workshop workers in the city as well as many transporters (Göncer 1971; Çelik and Sert 2020).

One of the most significant marble quarries in the ancient era was the Dokimeion (İscehisar) marble quarry. The first research on the quarry’s dates back to the 1870s, when evidence of the Dokimeion marble was found in Roman records and archaeological discoveries. Subsequently, European researchers conducted numerous studies at intervals on quarries and marble extracted from them (Waelkens 1985). The Dokimeion (İscehisar) marble quarries were particularly crucial during the Roman period because of their diverse colors and extraction of large blocks and columns. While white marble, predominantly used in sculpting, was extracted from various places during ancient times, marble known commercially as “Pavonazzetto,” characterized by red veins or “violets,” was exclusively extracted from Dokimeion (Koch 2001; Çelik 2003; Çelik and Sert 2020).

More extensive research and documentation regarding andesites in the same region are needed. Despite the absence of historical records, numerous historical structures such as bridges, mosques, and fountains dating back to ancient times and demonstrating the usage of İscehisar andesites have survived to the present day. Particularly in Seljuk and Ottoman architecture, there is a notable prevalence of andesites constructing mosques and fountains. These enduring structures were constructed using pink, brown, and gray-black andesitic rocks. Regarding historical heritage, İscehisar andesite is an important construction material that has been extensively studied in recent years. Dedeoğlu and Yılmaz (2016) examined the geochemistry of İscehisar lamprophyres. Çelik and Kaçmaz (2016) investigated its static and dynamic capillary water absorption properties, Çelik et al. (2017) examined the effect of different aqueous environments on capillary water absorption, Çelik and Aygün (2018) studied its resistance to salt crystallization with sodium sulfate and sodium chloride salts, Çelik and Yılmaz (2018) explored the impact of saline and acidic aqueous environments on capillary water absorption potential, Çelik et al. (2018a) examined the effect of water-repellent chemicals on its disintegration due to salt crystallization, Çelik et al. (2018b) assessed its usability as concrete aggregate, Çelik et al. (2018c) studied its resistance to salt crystallization, Çelik et al. (2018d) explored the effects of freeze-thaw cycles on the physical and mechanical properties of samples of different dimensions, and Çelik et al. (2018e) investigated the impact of thermal shock treatment on its physical and mechanical properties. Özdemir et al. (2023) examined the weathering geomorphology of the İscehisar andesites in a cool, humid environment.

In this investigation, initial efforts were focused on characterizing İscehisar andesite, a material with extensive historical usage. The analysis encompassed the identification of building stones through petrographic-mineralogical techniques (polarizing microscopy, XRD, SEM) and assessments of their chemical composition, pore diameter distribution, and physico-mechanical properties. Subsequently, attention shifted to elucidating the Historical Heritage structures in the Afyonkarahisar region of Turkey, highlighting the use of andesitic rocks as integral building materials.

Location

The marble quarries in the southern part of the İscehisar district are better known than andesites. This is because while andesites are used locally, İscehisar marbles have been utilized in numerous monumental works across a wide geographical area from Anatolia to Europe and North Africa (Çelik and Sert 2021; Çelik 2023). İscehisar andesites are located 12 km northeast of İscehisar (Fig. 1). The original andesites, which are initially gray and blackish in color, can turn pink and brown over time owing to the weathering of iron-containing minerals such as hornblende and biotite in their composition. İscehisar andesite presents three different color distributions: pink, dark brown, and gray-black. Currently, andesites of varying sizes and surface color are utilized, as illustrated in Fig. 2.

Today, in the Iscehisar andesite quarries, large-sized irregular rubble stones are produced by utilizing the crack systems in the rock, similar to those in ancient times. These rubble stones, dimensioned through the wire-cutting method, are transported to cutting-processing facilities. Subsequently, these rubble stones, dimensioned through the cutting method, are used, especially in contemporary times, for vertical cladding on walls and facades, and for horizontal applications such as pavement and flooring in both the interior and exterior parts of buildings. They find applications in various areas, such as stair steps, retaining walls, different profiles (cornices and wedges), the restoration of historical buildings, and urban furniture (seating groups and flower beds), as well as in pavements, curbs, and paving stones in pedestrian pathways, parks, and gardens. In addition, andesites have become preferred domestic and international natural stone users in recent years because of their homogeneous and non-fading colors and untreated, polished, hammered, or roughly carved surface forms.

Geological Setting

The oldest geological unit in the İscehisar region consists of Paleozoic schists. These metamorphic rocks, collectively known as Afyon metamorphics, include mica, calcareous, quartz, and phyllite schists. Afyon metamorphics are typically characterized by coffee, brown, and green hues with a crinkled granoblastic texture that forms a schist. Neogene (Cenozoic) sediments, with angular unconformities, overlie schists. This series, named the Gebeceler Formation, comprises the tuff and agglomerate, limestone, and conglomerate members. It is composed of finely intermediate thick-bedded conglomerates, sandstone, agglomerate, tuff, marl, clayey limestone, and silicified limestone units (Metin et al. 1987; MTA 2009).

The region has been influenced by volcanic activity starting in the late Upper Miocene and continuing through the Pliocene. Because of this volcanic activity, extensive areas in the region are covered by dacitic tuffs, agglomerates, andesites, trachytes, trachy-andesites, and basalts. The volcanic rocks consist of white and cream-colored tuffs at the base and trachy-andesitic rocks in shades of black, gray, and maroon at the top (Fig. 3). Unconformably overlying these are alluvial deposits, representing the youngest units in the study area. Volcanic rocks are widely distributed and form high mountains with rugged and steep topography. These volcanic rocks, typically brownish, pinkish, and brown, are predominantly located above the tuffs and agglomerates, and possess an andesite-trachybasalt mineral composition. They also exhibited lateral variability. The İscehisar andesite examined in this study is part of this unit. The andesitic rocks in this region are approximately 0–150 m. In the rock resembling an andesitic lava flow, widespread opaque and clay mineralization was observed. (Metin et al. 1987; MTA 2009).

Besang et al. (1977) determined the radiometric age of the volcanic rocks in the Afyonkarahisar vicinity to be 8.5–14.5 million years (Middle-Upper Miocene). Based on their study, Aydar et al. (1996) suggested that andesitic and trachytic volcanism occurred in two separate stages during the Middle-Upper Miocene interval. Andesitic volcanoes have an extensive distribution in the study area, forming rugged and steep topography in the high mountains. Generally brownish and brown, these andesitic rocks, located above the dacitic tuffs and agglomerates, exhibit mineral compositions of andesite and trachy-basalt. They vary laterally and have been identified as alkali trachyte, trachy-basalt, trachy-andesite, pyroxene andesite, augite andesite, and andesite based on various petrographic samples (Metin et al. 1987; MTA 2009).

Fig. 1

Location map of the quarries where İscehisar andesites are produced (a), view of the quarries (b, d) and andesite blocks (c)

Fig. 2

Color range of İscehisar andesites pink (a), brown (b), gray andesite (c)

Fig. 3

Generalized geological map of İscehisar and its surroundings (after MTA 2023)

Characterization Methods

To characterize the material properties of the İscehisar andesites, a combination of chemical analyses and mineralogical-petrographic assessments was employed. Chemical analyses were conducted using a Rigaku/ZSX Primus II XRF instrument. Thin sections were prepared for petrographic examination, and polarized microscope inspections were carried out using the Nikon Eclipse 2V100POL model to examine the texture and mineralogical composition. XRD analyses were performed using a Shimadzu XRD-6000 device with a Copper (Cu) X-ray tube. SEM analyses were conducted using a LEO 1430 VP model SEM device. The pore size distributions of the andesitic samples were determined using a mercury porosimeter (Micromeritics Auto Pore IV 9500). The experimental conditions involved a contact angle of 140 °C under a 480.00 erg/cm² vacuum.

Three andesite samples were used for the chemical analysis, two for the XRD analysis, one for the pore size distribution analysis, and four for the SEM analysis. Physical and mechanical experiments were conducted to determine the properties such as density, water absorption, porosity, ultrasonic wave velocity, and compressive strength of the andesite samples. Physical and mechanical characterization of the building stones involved conducting tests according to the TS EN standards. The determined properties encompass total and open porosity (TS EN 1936 2010), bulk and apparent density (TS EN 1936 2010), P-wave velocity (TS EN 14,579 2006), water absorption (TS EN 13,755 2009), water absorption capillarity (TS EN 1925 2000), uniaxial compressive strength (TS EN 1926 2007). Each building stone was tested using six specimens in the form of 50 mm cubic samples for mechanical and physical assessments. Pinkish-colored andesite samples were used in all characterization experiments.

Chemical, Mineralogical, and Technical Characterization

Chemical Analysis

As part of the characterization study, X-ray fluorescence (XRF) analysis was conducted to determine the chemical composition of the three andesite samples. The main oxide content of the andesite is listed in Table 1. According to the results of the main oxide analysis of the andesite, the predominant component was SiO₂. The SiO₂ ratio of the andesite was determined to be between 56.70% and 57.50%. This finding was corroborated by X-ray diffraction (XRD) analysis. The second major component, Al₂O₃, ranges from 15.90 to 16.10%. This component may originate from feldspar minerals, such as albite and sanidine, and clay minerals, such as illite. Other significant components included K₂O, CaO, Fe₂O₃, Na₂O, and MgO. The reddish weathered color of andesite can be attributed to its high iron content (> 4%). Fe₂O₃ indicates the partial dissolution of iron from the surrounding environment, affecting the andesitic matrix. The observed high K₂O content may be linked to potassium (K) retention during the transformation of mica minerals such as biotite and muscovite in the tuff samples. These findings are consistent with the results obtained from the XRD analysis. To determine the origin of the examined rock based on chemical analysis data, the total alkali (Na₂O + K₂O) and silica (SiO₂) diagrams proposed by Le Bas et al. (1992) were used. The rock used in the experiments was determined to have trachy-andesitic composition (Fig. 4). Complemented by XRF and XRD techniques, chemical analysis has provided a comprehensive understanding of andesite samples. SiO₂ and Al₂O₃ emerged as critical components, showing consistent ratios and confirming the andesitic nature of rocks. Various oxides, including K₂O, CaO, Fe₂O₃, Na₂O, and MgO, are suitable for mineralogical compositions.

Table 1 Chemical composition of andesite samples

Fig. 4

Silica versus total alkali content of andesites used in the experiments Le Bas et al. (1992) classification in the diagram. The andesite samples were located in the trachy-andesitic alkaline region

Mineralogical and Petrographic Characterization

Polarizing Optical Microscope Analysis

To determine the mineralogical, petrographic, and textural features of the andesite, examinations were conducted under a polarizing microscope (Fig. 5). Thin sections were prepared from the three andesite samples for petrographic identification, and mineral identification was performed under a polarizing microscope. The matrix structure of the andesites consisted of glassy and microlitic fine-grained plagioclases. Within the matrix, hornblende and pyroxene minerals were observed as phenocrysts of various sizes. These findings were consistent with the minerals identified in the XRD analysis. A distinct flow texture was evident in the matrix. Pyroxene minerals, identified as phenocrysts, are commonly observed to exhibit signs of cracking and weathering. A partial alteration was observed in some areas of the hornblende. The pinkish-reddish color observed in the rock’s stems from the alteration of mafic minerals, such as hornblende. As a result of this alteration, iron oxide coatings were observed around the mafic minerals (etc. biotite, hornblende). Variously sized pores were also present in the andesite matrix. Through the examinations conducted, it was determined that the andesites exhibited a porphyritic texture.

Fig. 5

Thin section views of andesite sample showing under polarized light (XPL) (a, c), plane polarized light (PPL) (b, d); (Pj: plagioclase, H: hornblende, B: biotite, Pr: pyroxene, Vg: volcanic glass and P: pore)

SEM Analysis

Scanning Electron Microscopy (SEM) was used to determine the crystal shapes and micro-morphological features of the sub-microscopic minerals. Photomicrographs of the minerals identified in the microanalysis of andesites are shown in Fig. 6. SEM examination revealed the presence of plagioclase, hornblende, biotite, montmorillonite (smectite), volcanic glass, and pores. The existence of these identified minerals is highly consistent with both the microscopic and XRD analyses. SEM analyses revealed the transformation of feldspar minerals located on volcanic glass into smectite group clay minerals. The presence of these clay minerals suggests that periodic weathering processes affect both the volcanic glass and feldspar.

Fig. 6

SEM micrographs of andesite sample. (Pj: plagioclase, H: hornblende, B: biotite, M: montmorillonite (smectite) Vg: volcanic glass and P: pore)

X-ray Diffraction Analysis

The XRD analysis results to determine the mineralogical composition of the İscehisar andesite samples are shown in Fig. 7. The XRD analysis determined that the andesites primarily comprised orthoclase and sanidine as K-feldspar and andesine as plagioclase. These results highlight the predominant presence of orthoclase and sanidine, indicating a significant proportion of K-feldspar in the andesite. Minerals such as tridymite, pyroxene, biotite, hornblende, and montmorillonite were also identified. Clay minerals, such as montmorillonite, indicate occasional alteration of volcanic glass components and feldspars. The elevation of the baseline in the XRD graph from 2θ = 0° suggested the presence of an amorphous material (volcanic glass). This observation was supported by microscopic analysis, which confirmed the presence of volcanic glass.

Fig. 7

X-ray diffraction (XRD) diffractogram of İscehisar andesite

Pore Structure Characterization

The pore size distribution of the İscehisar andesite was determined through mercury intrusion porosimetry (MIP), and the relevant graph is provided in Fig. 8. The mercury intrusion data obtained from the mercury intrusion porosimetry tests of the İscehisar andesite samples are presented in Table 2. The andesite sample had a pore size distribution ranging from 0.003 to 300 μm. Most pores were also found in the 0.01–7 μm range. The pore size distribution of the andesite was bimodal, with peaks between 0.01 and 7 μm. The first peak is around 0.01 μm, whereas the second is around 3 μm. According to the intrusion data summary, the average pore area diameter of the andesites was 0.009 μm, the average pore diameter was 0.025 μm, the density was 2.417 g/mL, and the porosity was 12.151%.

From the pore size distribution data of İscehisar andesite, the percentage of pores with a size smaller than 0.1 μm is calculated as 40.59%, the rate of pores with a size between 0.1 and 1 μm is 3.88%, and the percentage of pores with a size larger than 1 μm is 55.53%. Water absorption significantly accelerates decomposition, and salt solutions that can dissolve and be transported by water primarily enter the material through capillarity. Therefore, the pore distribution between 0.1 μm and 1 mm was significant. The pore distribution of İscehisar andesite in the range of 0.1 μm to 1 mm was 59.41%. Considering that the pore size distribution falls within these values, it can be said that andesite has a pore size distribution sufficient for the infiltration of liquids.

Research findings indicate that the predominant pores within andesites are less than 10 μm in diameter. These pores typically manifest among minerals and within volcanic glasses. Specifically, pores within volcanic glass manifest as elongated, slender tubes. In contrast, those between minerals vary in shape, predominantly appearing as irregular and random structures contingent on the arrangement of the minerals.

Table 2 Intrusion data summary determined using mercury interference porosimetry (MIP) of the andesite sample

Fig. 8

Pore size distribution plot of andesite sample determined using mercury intrusion porosimetry (MIP)

Physical and Mechanical Characterisation

The porosity of natural building stones is directly related to weathering. For instance, high porosity adversely affects properties such as the water absorption and strength. According to the data obtained from the experiments, the real density of andesites was 2540 kg/m³, with an open porosity of 13.19% and a total porosity of 19.22%. The uniaxial compressive strength was determined to be 49.93 MPa. Based on these characteristics, andesite can be described as a high-porosity building stone. Although high porosity in natural building stones negatively affects some physical and mechanical properties, it positively influences heat and sound insulation. Density and porosity generally affect the strength of the building stones. Low-density porous rocks are typically less resistant to corrosion. Porosity is a crucial factor in permeability and water absorption. Therefore, high porosity naturally increases the water absorption (Guruprasad et al. 2012). The pores within the building stones play a significant role in air insulation.

Table 3 Physical and mechanical properties of andesite

Water Absorption by Capillarity

A porous building stone used in the walls or cladding of structures absorbs water when it is in contact with rain or groundwater. This absorption process occurs via capillary water absorption. Capillary capillarity typically arises from the capillary suction force generated in pores with diameters up to 1 mm. The water on the surface of the pores exhibits a characteristic wetting angle, and the tendency of water to enter the pore system is referred to as capillary absorption. The mechanism of capillary water absorption depends primarily on the porosity size and geometry of the porosity system (Siegesmund et al. 2014).

Graphs depicting the measured capillary water absorption data for the andesites and the corresponding water absorption levels are shown in Fig. 9. This experiment required time intervals of 1, 3, 5, 10, 15, 30, 60, 480, 1440, and 2880 min. For the first 60 min (1 h), the capillary water absorption of andesite gradually increases, with the absorption rate ranging from 0.40 kg/m² at 1 min to 1.75 kg/m² at 60 min. This indicates relatively rapid absorption of water during the initial period. Beyond 60 min (1 h), the absorption rate continued to increase, but at a slower pace than the initial 60 min. The absorption rate at 480 min (8 h) is 2.67 kg/m², and it further increases to 4.70 kg/m² at 2880 min (48 h). This suggests that, while water absorption still occurs, the rate of absorption decreases over time, indicating a diminishing trend in the capillary water flow behavior of andesite beyond the first hour. The capillary water absorption value for andesites was determined to be 4.70 kg/m² after 2880 min. However, even after 2880 min, the andesites still possess water absorption capacity, meaning that all the pores of the andesites still need to be filled with water. This situation can also be observed at the water level heights of the samples.

According to the classification conducted by Graue et al. (2011), stones with capillary water absorption values < 0.5 kg/m² h⁰·⁵ exhibit low capillary water absorption, stones with values between 0.5 and 3.0 kg/m² h⁰·⁵ show moderate capillary water absorption, and stones with values > 3.0 kg/m² h⁰·⁵ demonstrate strong capillary water absorption. According to this classification, the capillary water absorption of İscehisar andesites is 4.70/6.93 = 0.68 kg/m² h⁰·⁵, placing them in the stone’s category with moderate capillary water absorption. The categorization as having moderate capillary water absorption implies moderate susceptibility to water ingress, a critical consideration for construction applications, especially in regions prone to moisture or precipitation.

Table 4 Average capillary water absorption of andesite

Fig. 9

Average capillary water absorption curve values of the andesite sample as a function of the square root of time (a) and the appearance of water absorption levels (b)

The Historical Periods of Anatolia

Anatolian history encompasses numerous nations, states, and civilizations that have settled around Anatolia. The historical periods of Anatolia, commonly referred to as Asia Minor, can broadly be divided into the following subcategories: prehistoric times until the end of the 3rd millennium BCE (Paleolithic, Neolithic, Chalcolithic, Bronze Age), Ancient Anatolia (including the periods of the Hittites, Hatti, and post-Hittite eras), Classical Anatolia (including the Achaemenid, Hellenistic, and Roman periods), Byzantine era, Seljuk and Ottoman periods, and Modern Anatolia (the Republic of Turkey) (Akurgal 1993, 1998). In the Afyonkarahisar region, there are numerous historical heritage structures that date back to the Hittite period, especially from the Seljuk and Ottoman eras, continuing to the present day. Volcanic rocks such as tuff and andesite are predominantly utilized in these constructions. One notable building stone among them is the İscehisar andesite. This study will examine the periods in which İscehisar andesites were used, and structures that have endured as historical heritage sites up to the present day will be explained.

Building Stone Source of Historical Heritages

The Hittite Period

Afyonkarahisar (Ancient Akroinοn) Castle

Historical structures constructed using volcanic rocks such as andesite during ancient times have survived to a limited extent to the present day. One such historical structure is the Afyonkarahisar Castle (Fig. 10a). Situated within the city limits of Afyonkarahisar and centrally located, the castle is considered the starting point of physical settlement and represents a construction with qualities that serve as an example of defensive fortification due to its geographical location and morphological structure. Afyonkarahisar Castle is positioned on a volcanic rock mass (trachyte) at 226 m. In 1350 BC, during the reign of Hittite Emperor II. Mursili was a fortified position during the Arzawa Campaign and was named Hapanuva. Throughout history, the castle has been utilized by various civilizations, starting around 1800 BC, including Hittites, Phrygians, Lydians, Persians, Greeks, Romans, Byzantines, Seljuks, and Ottomans (Göncer 1971).

Fig. 10

View of Afyonkarahisar (ancient Akroinοn) Castle (a). Detailed views of the trachy-andesite and andesite used in constructing the rubble stone walls within the upper (inner) castle walls (b, c). Appearance of the andesitic basalt and tuff used in the restoration work on the middle castle walls (d, e)

On the summit of the castle, traces of the Phrygian Period, which occurred between 1200 − 700 BC in Anatolia, can be found. Numerous places of worship and four large cisterns (water pits) were dedicated to the Mother Goddess Cybele. The castle’s walls were restored by the castle’s commander, Architect Bedrettin Gevhertaş, in 1235 during the Seljuk Sultan Alâaddin Keykubat’s era, who also added a small mosque and palace to the castle. In 1573, under Ottoman Sultan II. Selim Mahmut Bey repaired the towers and cisterns and kept them. Today, Afyonkarahisar Castle is registered as a natural archaeological site. However, many traces of the civilizations mentioned have been lost, their period-specific characteristics have eroded, and their existence cannot be determined. The repairs and misguided restorations made by the castle have led to the distortion of its original structure and damage to its historical identity (Fig. 10b, c) (Göncer 1971; Köker 2020; Köker and Şimşek Tolacı 2021).

Afyonkarahisar Castle has three tiers: upper (inner), middle, and lower (outer) walls. Most of these walls have vanished over time, with only a small portion managing to survive until the present day. The lower walls were removed and the middle walls were partially destroyed. Basaltic and andesitic rocks were used to construct the castle walls. These walls underwent restoration during the Byzantine, Seljuk, Ottoman, and Republic periods. However, owing to the unsuitable characteristics of the natural stones used in the restoration and the inadequacy of restoration techniques, the disappearance of the historical texture is evident (Fig. 10d, e) (Çelik and Sel 2006).

The Roman-Byzantine Period

Sarcophagi

During the Roman imperial period, the production of sarcophagi was concentrated in specific centers. In addition to Rome and Athens, another significant center for sarcophagus production was the ancient city of Dokimeion in Asia Minor, located in İscehisar, Afyonkarahisar. Here, sarcophagi, known as Dokimeion Columns, made from white marble, were produced and exported to many cities within the empire (Awan 2000; Waelkens 2019). Apart from marble sarcophagi, there are also sarcophagi made of andesite stone in the ancient city of Assos in the Ayvacik district of Çanakkale Province, Turkey. These sarcophagi, carved from locally sourced andesite stones, have a fascinating feature: they are known as “flesh-eating stones” because they rapidly decompose the bodies placed inside (Savaşçin and Er 2023). A similar andesite sarcophagus, displayed in an open-air museum in İscehisar (Fig. 11a), showcasing ancient marble remnants, can be found in the same style (Fig. 11b, c). Additionally, in the same area, there are andesite water vessels of various sizes, presumably used in religious ceremonies, carved from the andesite (Fig. 11d).

Fig. 11

The view in the open-air museum showcases ancient architectural elements, predominantly crafted from Afyon violet (Pavonazzetto) marble extracted from the ancient marble quarry in İscehisar (a). Among these marble pieces are carved sarcophagi made of andesite (b, c) and water vessels that are utilized for various purposes (d)

İscehisar (Dokimeion) Great Bridge

One of the historical structures that has survived since ancient times, constructed using volcanic rocks such as andesite, is a historic bridge located in İscehisar. This bridge, known as the “Koca Köprü” (Great Bridge) in the region, is believed to belong to the ancient city of Dokimeion, whose remnants are likely located in the present-day İscehisar. Situated over the Kurudere (Doureius), a branch of the Akarçay River that divides and flows through the city, the ancient bridge dates back to the Hellenistic period and is still in use today (Fig. 12). Built with Gothic arches using andesite and marble blocks, it connects the city’s two banks (Göncer 1971).

Fig. 12

Views of İscehisar Koca Bridge from front (a), side (b, d) and top (c)

Bolvadin (Ancient Polybotum) Kırkgöz Bridge

The exact construction date of the Kırkgöz Bridge could not be precisely determined. The earliest mentions of the bridge are in the Hittite Tablets at the Ankara Museum of Anatolian Civilisation. In these tablets, Hittite King II. Mursili, during his Arzawa Campaign in 1344 BCE, utilized this bridge. The famous Royal Road, frequently mentioned in military and commercial expeditions of that era, passed through the Kırkgöz Bridge. The historic Silk Road, extending from China through Central Asia, Iran, and Anatolia to Europe, traversed the Kırkgöz Bridge. In 1070 AD, during the repairs commissioned by Byzantine Emperor Romulus Diogenes, the Kırkgöz Bridge was restored. In the First Crusade of 1097 AD, crusaders battled with the Turks on this bridge, resulting in extensive casualties and damage. It was subsequently substantially reconstructed by the Byzantine Emperor Manuel Comnenus in 1150 AD, who added new arches. In 1534 AD, the Ottoman Sultan Suleiman, the Magnificent, passed through the Kırkgöz Bridge and captured Baghdad in December. Before embarking on the campaign, he repaired the roads, and in 1550 AD, sent the renowned architect Mimar Sinan to Bolvadin to renovate the bridge. The parapet, body, and bridge arches were constructed from black volcanic and white marble cut stones. Among them, sprinkled architectural fragments came from the Roman era. Large stones of different origins, from ancient Polybotum ruins, were used in the pavement of the bridge. Additional arches were added, increasing the total arches to 64. Today, Kırkgöz Bridge is a structure formed by merging two parts, one from the medieval period and the other from the 16th-century Ottoman era. The southern section, built during the classical era, is 200 m long with 42 arches, whereas the northern section from the Ottoman period is 200 m long with 22 arches. In total, the bridge spans 400 m with 64 arches. Over time, minor repairs led to the closure of seven arches, leaving 57 arches in existence (Fig. 13) (Bayar 2010; Akdemir and Sener 2010).

Fig. 13

The view of the Kırkgöz Bridge before the restoration view (a) (Bayar 2010), and view of the from different facades (b, c, d)

The Muslim Period (Seljuk and Ottoman)

Historical Heritage Mosques

Afyon Ulu Mosque (Grand Mosque)

The Grand Mosque, built between 1273 AD, had a roughly rectangular and slightly trapezoidal plan. Also known as the “Forty Pillar Mosque,” it is one of the few examples of wooden architecture among the mosques of the Anatolian Seljuk period (Fig. 14). The construction was made of rubble stone, predominantly andesite. The stones used in the construction of the mosques were mainly andesite. The structural stones used on the facades and minaret base directly reflect the local rock formation in the surrounding area. Three rows of andesite ashlar bands circulate along the external walls of the mosque, with sequential rubble stones between the bands. These rubble stones occasionally include andesite. The Afyon Grand Mosque is vertically supported by nine wooden columns facing the qibla and carried by 40 wooden pillars. These pillars were cylindrical with muqarnas wooden capital resting on marble bases at the bottom. The wooden column capitals, supporting beams, and wooden cladding boards in the Afyon Grand Mosque are adorned with floral and geometric motifs of the penwork. However, some of these have suffered damage during the restoration of each structure. Based on these features, the Grand Mosque has been nominated for inclusion in the UNESCO World Cultural Heritage List (Aygen 1973; Akyol et al. 2022).

Fig. 14

Exterior view of the Afyon Grand Mosque (1273 AD), which was primarily built using volcanic rocks such as andesite

Numerous mosques and prayer rooms were commissioned in Afyonkarahisar during the Seljuk and Ottoman periods. Many of these mosques have survived to the present day through various repairs conducted at different times. The mosques were constructed using abundant volcanic rocks, such as tuff, andesite, and trachy-andesite, found in the vicinity. Some of these mosques include the following.

The Yukarı Pazar Mosque has two inscriptions; one shows the construction date, and the other shows the restoration date. The inscription accepted as the construction date determined that it was built in 1298 AD. It has a plan close to a square covered with a single dome. The outer walls were made of cut andesite stone, and the eastern and southern facades of the mosque incorporated reused antique stone blocks, with a door-type tombstone used in the northern wall (Fig. 15a) (Topbaş et al. 2007). The Kuyulu Mosque has a square plan, is covered with a single dome, and is a small mosque with mixed-cut stones of tuff and andesite. Although the exact construction date is unknown, it is considered a Seljuk-era artifact. The minaret is named “Kuyulu Mescit” because it is built over a well foundation (Fig. 15b) (Aygen 1973; Topbaş et al. 2007). The Ot Pazarı Mosque consists of one large and three small domes. It is composed of mixed cut stones of tuff and andesite. The construction date was 1589 AD, from the Ottoman period (Fig. 15c) (Topbaş et al. 2007). The Arap Mescit Mosque has outer walls made of cut stone with a square space covered by a single dome. It was built between 1433 AD and 1438 AD (Fig. 15d) (Aygen 1973; Topbaş et al. 2007).

Fig. 15

Views of historical heritage mosques where andesites are extensively used. Yukarı Pazar Mosque (1298 AD) (a), Kuyulu Mosque (1298 AD) (b), Ot Pazarı Mosque (1590 AD) (c), Arap Mescit Mosque (1298 AD) (d)

Historical Heritage Bridges

Like the Romans, the Seljuks and Ottomans attached great importance to roads and bridges for military operations and trade transportation. Consequently, Afyonkarahisar, as in Anatolia, commissioned numerous caravanserais, fountains, mosques, and bridges. Local building stones are generally used in their construction, with abundant tuffs and other volcanic rocks such as andesite, which is prevalent in the Afyonkarahisar region. However, owing to newly constructed roads, some of these bridges have lost their functionality and must be dilapidated. Consequently, the construction dates of most bridges still need to be determined. Below are some bridges in Afyonkarahisar that have survived to the present day, constructed using andesite.

The Altıgöz Bridge is located on the Akarçay River at the foot of the Cirid rock, between two stations on the old road leading to Eskişehir. Owing to its six arches, two of which are round and four pointed, the bridge is constructed using reused andesite and limestone. Between the second and third piers of the bridge, there is an inscription on white marble repurposed from an ancient sarcophagus, indicating that the bridge was repaired by the Seljuks in 1209 AD and later by the Ottomans in 1661 AD (Göncer 1971; Kaya and Üyümez 2005). Subsequent repairs also show the use of travertine in railings (Fig. 16a).

The İkigöz Bridge is located across Kocatepe Cemetery and 50 m from İzmir Road. Unfortunately, owing to new roads and construction works, a significant portion of the bridge is buried under rubble and is unusable (Fig. 16a, b). The Kanlıgölet Bridge, situated on the Akarçay River along the road to Çavdarlı village, is constructed with cut stone material and is a single-arched round-arch bridge (Fig. 16c). The Harmancık Bridge, on the road to Karakaya village, is a two-arched bridge with reduced footings because the arches are filled with rubble. Despite occasional damage, it remained usable, with a marble inscription indicating its construction in 1873 AD (Fig. 16d). Kurşunlu Bridge, located on the Akarçay River along the Cement Factory Quarry Road, has six round arches. Although initially made with cut stones, recent repairs have used concrete. Unfortunately, because of the construction of a modern bridge nearby, it is now unusable (Fig. 16e) (Daş 1997; Kaya and Üyümez 2005).

Fig. 16

Today’s views of historical heritage bridges in Afyonkarahisar, where andesite and other stones were used as building stones. Altıgöz Bridge (a, b), İkigöz Bridge (c), Kanlıgölet Bridge (d), Harmancık Bridge (e), Kurşunlu Bridge (f) (Kültür 2023)

The Republic Period

In the Republican era, the significant use of İscehisar andesites in monuments and structures was evident. Examples of structures from the Republican period include the Victory Museum (1920), PTT building (1940), Afyon Railway Station building (1939), and Utku Monument Park (1936) (Fig. 17).

Fig. 17

Utilization of İscehisar andesites in monuments and structures from the Republican era: (a) Victory Museum, (b) PTT building, (c) Afyon Railway Station building, and (d) Utku Monument

İscehisar andesites have been widely used since ancient times. Unlike andesites, which are primarily used as building stones, contemporary advancements in cutting and processing techniques have led to their application in various dimensions and forms. Andesites, particularly those suitable for color and hardness, are commonly employed as pavement, flooring, and architectural design elements in various structures. In addition to these applications, andesites are used for borders, rain gutters, lintels, stair steps, retaining walls, tombstones, and in the landscape design of parks and gardens, including pedestrian pathways, seating areas, flowerbeds, and trash bins, and in the restoration of historical buildings (Fig. 18) (Çelik et al. 2019).

Fig. 18

Contemporary applications of andesites include borders, pavements, and cladding stones

Discussion and Conclusions

Utilizing the total alkali (Na₂O + K₂O) and silica (SiO₂) diagrams proposed by Le Bas et al. (1992) facilitated a comprehensive assessment of the rock origin, revealing a trachy-andesitic composition in the examined samples. This study provides valuable insights into the petrogenesis and geological history of andesite, laying the foundation for further exploration and understanding of these intriguing geological formations.

An open porosity of 13.19% and total porosity of 19.22% indicate that andesite is a high-porosity building stone. The observed high porosity significantly affects the specific physical and mechanical properties. Water absorption and strength, which are crucial indicators of material durability, are adversely affected by increased porosity. Low-density porous rocks, such as andesite, are generally less resistant to corrosion. This discovery underscores the significance of considering both the density and porosity when assessing the long-term durability and performance of building materials.

The observed capillary water absorption value for the andesites, measured at 4.70 kg/m²s^0.5, after 2880 min, indicates the ability of the material to absorb water over an extended period. This sustained absorption suggests that even after 2880 min, the andesites retain their water absorption capacity even after a lengthy duration. The prolonged water absorption capacity observed in the andesites, even after 2880 min, underscores the importance of understanding the behavior of the material over time. This knowledge is crucial for architects, engineers, and builders, who seek to make informed decisions regarding the selection and use of building materials, especially in contexts where water exposure is a significant factor.

The findings of this study contribute to a broader understanding of the properties of İscehisar andesites, enriching the body of knowledge related to the performance of these stones in construction and environmental settings.

Anatolia has been one of the primary production areas for natural stones, particularly marble, since ancient times. In contemporary times, many quarries, particularly those operated in Western Anatolia, either continued the operations of quarries from ancient times or were located close to these historical sites. There are abundant volcanic rocks near İscehisar (Dokimeion), renowned for its marble, known commercially as “violet” and historically as Pavonazzetto. These rocks are products of andesitic volcanism and are classified as alkali-trachyte, trachyte-basalt, trachyte-andesite, pyroxene andesite, or andesite based on their chemical compositions. However, commercially, they are all referred to as “andesite.”

Known as “İscehisar andesite,” these volcanic rocks come in pink, brown, and gray-black colors and have been used as building stones from ancient times to the present day. The oldest structure made with andesites dates back to around 1350 BC and is the Afyon Castle, built by Hittites. The İscehisar Koca Bridge and Bolvadin Kırkgöz Bridge, constructed with andesites, were dated to the Roman-Byzantine period. Both bridges have survived to the present day, with repairs being made at various times. The most intensive use of andesite occurred during the Seljuk and Ottoman periods. Initially employed in bridges, fountains, mosques, and monumental structures, these andesites are now used in contemporary settings for borders, rain gutters, lintels, stair steps, retaining walls, tombstones, and park and garden landscaping, including pedestrian pathways, seating areas, flowerbeds, and trash bins. Andesites that lack polishing features are generally used in honed finishes. Additionally, various surface shaping techniques, such as hammering, sandblasting, combing, and bush-hammering, are increasingly expanding the range of applications for andesites.