Abstract
Ujan covers about 90 hectare area, where locates 5 Km away from modern Bostan Abad. Earlier construction of the urban center dates to 4-6 AH centuries that coincides to Seljuqs era. It developed during 7 and 8 AH centuries and reached to summit during middle Ilkhanid to Safavid period. It collapsed and destroyed during Qajar period. Here, there is an attempt to study effective elements in formation of Ujan and its consequent function, using descriptive-analytic view and historic research method, based on archaeological-environmental landscape. Finally, it is involved in reasons of collapse of the city. Bibliographic and field studies indicate that construction of the city was for midway positioning. In addition, present paper presents subjects about political and social history, architectural remains, urbanization, cultural remains, and different districts of the city including cemetery and administrative center. 
Keywords: Ujan, Seljuqid, Ilkhanid, Bostan Abad, Urbanization.

Introduction
Different factors involve and play significant role in formation of urban centers. Emergence and development of Iranian cities followed geographical, social, religious, defensive, administrative, and commercial conditions. Commercial routes and passages were effective and affected factors in formation of urbanization. Investigating such factors is effective in responding to location and reasons of emergence of a given city. Road networks were achievement of development during time, whereas dominated by various political, religious, security, and cultural elements. Reasons of abandonment and collapse of urban centers vary according to strategic and geographical position and function that divide to two natural and human factors. Generally, effective natural factors in abandonment of urban centers include earthquake, shift of rivers’ bed, landslide, drought, and lack of natural defensive barriers. Human factors could accelerate abandonment of an urban center that include remoteness from main routes or even side roads, warfare, disease, administrative policy, lack of enclosures and secure defensive ramparts. Cheap and low quality materials are among other factors that cause collapse of a city. Every urban center have especial function that suggests foundation of the area accordingly; among them are mining cities, ports, industrial cities, administrative-political cities, tourism cities, and etcetera. Understanding factors and elements of formation and development of cities are among the most important discussions since earlier times that attracted scholarships and resulted to different theories and models to analyze urbanization.   

Features of cities during Islamic period
Among features of Islamic urban centers were economic, social, military, and especially religious developments that played effective roles in formation and developments of urban centers even in earlier times. Islamic urbanization related to stability of government too, whereas emergence, development, and collapse of a city related to political circumstances. General studies on maps of Islamic cities indicate that many cities followed similar method and style of urbanization that shows probable common designer and architecture. Scholars also believe that designers and architectures planed maps before construction of buildings and constructed buildings and structures accordingly. In a miniature painting, dated to Babur reign, he points to a map in the hand of a man that designed it (Kiani 1365: 205). Islamic architectural thought in Islamic countries characteristically comprehended principles and generalities of civil programs then involved in details (Othman 1376: 27). In planning cities, there was emphasis on Jami and administrative buildings, where located public buildings in city center for public access. Tendency to privacy and peace in residential areas caused Iranian Islamic cities divide to two public and private parts, similar to pre Islamic urbanization. Bazar complex and extensions was pulses of urban life, where presented public and social activities. Residential area was private part of the city, where rest and peace dominated living atmosphere (Kheir Abadi 1376: 44). One can study urbanization according to different point of view. Scholar such as economists, politicians, historians, geographers, and philosophers investigate the subject from their point of view. There is not certain answer to relations between Islamic view and urbanization and their mutual effect. There are variations in effects on urban spaces and structural characteristics. According to Stern, urban life style followed earlier criteria after Islamic conquests, and it became Islamic in forms and generalities (Razavi 1387: 105-112). Cities are the most genuine center of civilization and cultural treasures, what should be recognized to make possibility to investigate evolutionary history of human life. Therefore, investigating cities that remained from earlier times play significant role in understanding political, social, administrative, economic, and cultural structures of societies that created them (Karimian 1384: 111-121).  Papoli Yazdi, quoting from Hufer, says that city is relation among six aspects: economic structure (variation of activity), social structure (social classes), body structure (public buildings), geographical position, law position, and political life (Papoli Yazdi and Rajabi Sanajerdi 1387: 50).

Ujan, Formation, Flourish and Collapse According to Historic Sources
According to historic sources, Ujan was alive earlier than Ilkhanid period, especially during Seljuq era. It existed as a strategic and important urban center, following different events including earthquakes, and wars; it was only during Ilkhanid period that the city reached to summit and glory. Every given historic city or monument partially imply political, religious, and social conditions that consequently followed political evolution, therefore, emergence cities with architectural nature is among the most important social evolution of Ilkhanid period. Historic city of Ujan was among important Ilkhanid cities (summer residence) at south of modern Bostan Abad, eastern Azerbaijan, where reconstructed during Ghazan reign. Ujan is among the cities that constructed by Ilkhanid rulers, while their Iranian viziers Islamicated new urban centers. Endowed city of Ujan was the summit of flourish in construction of public, martial, and administrative structures, and throne of Ilkhanid princes. 

Investigating Formation, Development and Collapse of Ujan, According to Archaeological Findings
Recognizing location of Ujan was at 1392, according to archaeological surveys at Bostan Abad regions. Historic and geographical descriptions of Ujan, especially Metraghchi’s illustrations remarkably helped to recognize location of the lost city. Site of Qullar, Ashraf Abad village (part of ancient Ujan), at eastern Bank of Ujan Chai River locates at 46-49-25 latitude and 37-35-48 longitude, and 1787 m longitude. Site of Dali Dareh Si locates 1 km away from Qullar (fig. 3). Constructing railway divided the area to two parts, and irrecoverably damaged the site (Velaiati 1385, 1392).  

Conclusion
Urban centers at the routes of main commercial and connecting networks, while potentially interconnected to other major cities or cities that geographically have abundant water sources, have opportunities to develop and survive. Therefore, location of city at commercial roads was highly signified, because made them capable to meet their needs and export their surplus. Urbanization at main roads highly signified and caused to flourish and wealth. By the circumstances, old cities appropriately coped with commercial activities and caused to raise townships and commercial parks next to carvansarai and small residences at ways. Alternatively, new urban centers emerged; among them was Ujan as an important city during Islamic Middle Ages at northwestern Iran, Azerbijan. 

Abstract
The historical city of Ujan, located in in East Azerbaijan northwest Iran, has been one of the most important cities of the Ilkhanid dynasty (1256 to 1335 AD). A number of coins were found during the excavation and study of the site by Tehran University’s Archaeological Board in 2017-2020. In this article, 13 coins have been analyzed and reported. The coins were cleaned as much as possible so that the inscriptions and designs were examined and read, whose results are presented in this paper. All of the 13 coins are minted in the styles attributed to the Abu Sa’id period, the last powerful Mongol Ilkhanid ruler born in Ujan. Based on elemental analysis, most coins are copper. Two of them are made of bronze alloy (copper-tin) and the other is made of brass alloy (copper-zinc). The use of lead has been reported in the composition of all alloyed coins. All the coins unearthed from Ujan excavations have been minted in the city of Tabriz. This is probably due to the commercial and economic importance of Tabriz in the Ilkhanid period, because no evidence of minting coins has been found or reported in the Ujan area so far. The analyses of the coins are indicative of important historical, cultural and political facts about the Ilkhanid dynasty.
Keywords: Ujan, Ilkhanid Period, Alloy, Mint, Ujan Coins.

Introduction
Ujan, located 38 km east of Tabriz, was an important city during the Ilkhanid period, serving as a summer residence for the royal family.  It was rebuilt during the Ghazan Khan Ilkhanid period but lost its importance due to earthquakes and wars. Ujan is an example of an Ilkhanid city with Islamic architecture and urban planning (Velayati et al. 2020).
Coins from Abu Sa’id, were found in Ujan and minted in Soltanieh and Tabriz. In archaeological studies, coins indicate civilization, prosperity, and decline of a territory or monarchy. The study of coins can provide insights into nations’ pasts, as well as their artistic, religious, political, and social development (Sarafrazi 2010). Ilkhanid coins are categorized into three groups: (1) early Ilkhanid period with Quranic verses and no Uighur inscriptions, (2) period of stability with Uighur inscriptions and Mongolian titles, and (3) time of Oljaitu with Persian inscriptions including Islamic testimonies, Shiite mottos, and names of Rashidin Khalifs (Avarzamani & Sarfaraz 2009).

Identification of Ilkhanid City of Ujan Based on Archaeological Finds
The Mongols’ recorded history dates back to the late 12th and early 13th centuries AD, with information from “the mysterious history of the Mongols” and Persian and Chinese records (Bosworth,1988:243). The Ilkhanid khans was elected in Qoriltay, with Maragheh, Ujan, Tabriz, and Soltanieh as capitals(Atwood 2004: 231, 233). After four seasons of study, the University of Tehran’s Archeology department discovered the historical city of Ujan, located 38 km east of Tabriz, north of Sahand Mountains, East Azerbaijan. Figure 1 shows the historical map of Ujan City (Velayati, 2016).

Historical Context of Ujan
The name of Ujan was first mentioned in the book “Masalak-al-Mamalak Istakhri” and later by other Arab geographers. In 698 AH, Ilkhan ordered the construction of the Islamic city, which was built quickly with bazaars, baths, and land divided among his relatives. Ghazan Khan rebuilt a mansion in Ujan and called it the city of Islam. Many events occurred in Ujan between 740 to 806 AH, including Amir Teymour resting in the Ghazani Palace. An Ottoman tourist reported that Ujan was once a large city but was destroyed during Holakokhan’s reign and people migrated to Tabriz. Ghazan Khan later repaired the castle of the city.

Ujan Coins
Studying the chemical composition of coins offers valuable insights into various aspects including politics, society, economics, and production methods. The origins of raw materials in different periods can indicate religion, art, culture, traditions, or architecture (Fierascu et al., 2009). Numerous coins were excavated from the historical city of Ujan and a comprehensive analysis was conducted on thirteen selected coins after thorough cleaning to ensure precise results (Figure 2).

Method 
In this study, 13 coins were imaged using Rigaku’s Radioflex-100CSB X-ray radiographic method to examine the metal core and legible motifs and inscriptions. After cleansing, the coins were imaged using a Leika / Wild M8 stereo microscope. A small part of the coins was cleaned and imaged using a FEI ESEM QUANTA 200 microscope to study the alloy composition. Elemental analysis was performed by the EDAX EDS Silicon Drift 2017 detector connected to the microscope.

Results and Discussion
The results of the elemental analysis of Ujan coins in Table 1 show that the base metal for making all coins is copper and a large number of samples have the same composition with small amounts of lead.
The thickness and lead content of coins affect their X-ray images (Figure 3). Coins with higher lead content and thickness emit fewer X-rays. The uniform distribution of lead particles in the metal matrix creates a distinction between the background and lead globules in X-ray images. This suggests that Ujan coins were cast horizontally using an open mold. Most coins have low amounts of lead, which is likely an impurity in the metal composition, associated with tin and sulfur. The lead impurities may be related to the smelting and extraction method used to mint the coins.

Inscription Reading and Minting Analysis  
Ilkhanid coins are divided into three periods based on their inscriptions, representing the cultural attitudes of Ilkhans. In the early years, they incorporated aspects of Iranian culture onto their coins, possibly influenced by advisors like Khajeh Nasir al-Din Toosi. In the second period, some Ilkhans tried to embrace their Mongolian heritage by minting coins in Uyghur script, but this failed when Al-Jaito converted to Islam and developed Islamic and Iranian culture (Yar Ahmadi, 2010: 40). Mongolian culture was marginalized, and only a few political dissidents used the second method of minting coins.
The analysis showed that corrosion and previous interventions have caused the disappearance or distortion of designs and inscriptions on some coins. Only some coins were examined and read after clearing based on evidence in X-ray radiographic images. Analysis of coins in this study indicates that they belonged to the period of Abu Sa’id, the last and greatest Ilkhan king. During his reign, coins did not follow a special formal pattern, but had limited use of geometrical and non-geometrical patterns with the king’s name, Islamic testimonies, and the name of Rashidun Khaliphs. Lion and sun motifs were prevalent, rooted in Roman Seljuq coin minting. Five, six or seven-pointed stars appeared on coins, possibly imitated from Seljuqs. Abu Sa’id also used Mihrab (altar) motif with Quranic verses on his coins (Salehi 2014: 61).
Coin UJ-01 features several motifs on one side, with the inscription “La ilaha illa Allah Muhammad Rasoolullah” on the other (Figure 4). Coin UJ-06 has an engraving depicting a rider racing on horseback, in the style of Ilkhani coins, with the phrase “La ilaha illa Allah Muhammad Rasoolullah” inscribed along the edge (Figure 5). Coin UJ-07 is well-preserved, with the ruler’s name written as “Al-Sultan Azam Abu Sa’id Bahador Khan Khaldullah Malika” and the mint name as “Tabriz Mint”. Inside a six-pointed star are the names of Rashidun Khaliphs and Hazrat Ali (AS), representing Abu Sa’id’s Sunni faith. Outside the star is the inscription “La ilaha illa Allah Muhammad Rasoolullah” (Figure 6).
During the Ilkhanid period, mints had a lot of freedom in choosing and writing inscriptions on coins, as long as they remained loyal to the Ilkhanid system and its religious policies. This allowed each sultan or ruler to change the coins according to their own taste. For example, in Amol, coins were minted with the names of the Twelve Imams even during the Timurid period. Studies show that during the time of Abu Sa’id, nearly a hundred cities and districts minted coins in his name. However, it seems that Ujan did not have a mint, possibly due to its proximity to Tabriz. Further excavation may reveal coins minted in Ujan.

Conclusion
Ujan is a city of great economic importance due to its location on the Silk Road and its role in trade. Historical sources suggest the city had many caravanserais and economic prosperity. Coins minted in Ujan, mostly from the period of Sultan Abu Sa’id Bahador Khan Ilkhani, have been found. In this research, 13 coins were examined, 10 made of copper and 3 of copper alloys. The copper used in minting is associated with lead, with uniform distribution of lead particles in the metal matrix of all Ujan coins. The horizontal minting method was used in casting alloys. Many coins have corroded or distorted designs and inscriptions, but three (UJ-01, UJ-06, and UJ-07) have almost complete Islamic inscriptions and designs in the style of Ilkhanoid coins.
The examinations show that during the early Ilkhanid period, rulers used religious inscriptions in minting coins to propagate their ideology and gain legitimacy among the people. The use of Quranic verses and inscriptions on coins from this period suggests that the Mongols, who lacked religious legitimacy to rule Islamic lands, sought to attribute their ruling to divine destiny by circulating coins among ordinary people.

Abstract
This article discusses the structural analysis of ancient mortars used in Ojai’s Castle, which belongs to the Ilkhanid period in Bostanabad County, East Azerbaijan Province. Various methods, including field studies for documentation, sampling, and laboratory analysis using X-ray diffraction (XRD) and X-ray fluorescence (XRF), were utilized to investigate the structural and physicochemical properties of the ancient mortars. For this purpose, ten mortar samples were collected from different sections of the outer walls of the castle, which were excavated in the past five years, and their dominant phases and compositions were identified using XRD and XRF. The results show that the composition of the mortars used in the castle is significantly similar. Contrary to existing assumptions based on the use of lime-based mortars in cold regions and stone structures, the mortars in Ojan Castle are composed of gypsum and quartz-based high-purity gypsum mortars. These mortars were used for structural reinforcement and, especially, for enhancing their compressive strength. Based on these findings, this study can serve as a reference for future research on the structural analysis of ancient mortars to restore the castle.
Keywords: Characterization, Seljuks-Ilkhanid, Ojan Castle, Mortar, XRD, XRF.

Introduction
Historical architecture exemplifies the dynamic progression and development of knowledge, structure, recognition, and production of diverse materials. Mortars, as significant architectural elements, play a crucial role in this evolution. Remarkably, numerous mortars have retained their structural attributes for centuries. These historical mortars represent cultural accomplishments, exhibiting distinct properties influenced by raw materials, technological methods, and their manufacturing and utilization processes. The analysis of historical mortar’s composition serves as a valuable tool in understanding the construction techniques and technological advancements employed in the past. By studying the structure, composition, and processing methods of traditional mortars, we can make informed decisions regarding their conservation, restoration, reproduction, and identification of potentially damaging factors in historical buildings. Furthermore, mineralogical and chemical analysis of mortars provides essential insights into their setting characteristics, mineral grading, and compound quantities, offering a comprehensive understanding of their properties. Concerning the specific topic of this research, which is related to the historical and cultural mortars of the Seljuk-Ilkhanid era we can say undoubtedly, the Ilkhanid era can be considered one of the brilliant periods in the history of urban planning in Iran and another beginning in the emergence of a new style in creating and developing urban spaces. This style, which is known as the “Azeri style”, hastened the creation of royal cities such as Ghazaniyeh and Soltanieh and the strategic mother city of Tabriz, which is the manifestation of the ideals and urban planning ideas of the Mughal Ilkhanid. It has remained unstudied until today. In this research, the structural analysis and identification of the mortar composition of the historical castle of Ojan (figure1-3), related to the Seljuk-Ilkhanate period, will be examined and studied. Until now, five seasons of scientific archeological excavations have been carried out in the historical castle of Ojan from 2018 to 2022, and the results show remarkable stone architecture and architectural decoration such as Muqarnas made by gypsum, tiles, shaped stones, and various objects. Belongings include copper coins, pieces of pottery from the Seljuk-Ilkhanate period, glass, metal nails, etc. (figure4-7 & table 1) 
The most important research questions regarding the mortars used in Ojan Castle are: 1. What types of mortars are present in Ojan Ilkhanate castle? 2. What are the fundamental characteristics of the mortar used in Ojan Castle? The research methodology for this study consists of three main components:  1. Gathering documentary information through library studies. 2. Conducted field studies, including sampling from the historic Ojan Castle and documenting the current condition of the site to understand the nature of the building under investigation. 3. Performed laboratory studies, specifically analyzing samples taken from the outer wall of the castle. This analysis includes structural analysis and qualitative examination of mortar materials.

Materials and Methods
In this study, after examining the explored sections of the Ojan castle, mapping of the structure was carried out. Based on the current condition of the walls and the materials used in the construction (Fig. 8), 10 random representative samples were taken from different sections of the castle, including the outer parts of the main walls and the areas between the main materials. The samples were selected from different parts of the walls to ensure sufficient dispersion. The sampling method involved separating layers from both intact and deteriorated sections. Fig. 9 and indicates the locations where the samples were taken. Based on field observations, the mortar layers, especially in shallower and more exposed areas, had weak and powdery structural conditions. However, at depths greater than 20mm from the wall surface, the mortar exhibited better strength compared to the surface layers. The color of the mortar was mostly white, with some areas having a slight grayish tint, and no traces of plant remains or other components were observed. In the next stage, images and visual information related to each sample were recorded on-site. Descriptions of the visual characteristics of the samples, along with images and sampling locations, were collected and documented in Table 2. All samples were powdered and passed through a 200-mesh sieve. They were then barcoded and sent to the laboratory for XRF (table 3, 4, figure10) and XRD (table 5, Fig. 11) analysis. The samples were barcoded using the following format: “Ojan Castle, 2020 (OC20), Tranche number (T), Sample code (S)”. For example, a sample would be labeled OC20-T16S01.

Discussion 
With the aim of structural analysis of the mortar used in the stone walls of Ojan Castle belonging to the Seljuk-Ilkhanate historical period in Bostanabad city, 10 samples of mortar were selected from different parts of the outer walls. Based on the results of the experiments (XRD, XRF), the use of mortar with the leading and dominant phase of gypsum is used in all samples, and also all types of phases with silicate structure and phases in the soil can be seen in all samples. To construct this mortar, high-purity gypsum and sand were used. Approximately %8 of the mortar composition consisted of other components, mainly soil elements such as Muscovite, Albite, Salts, etc. The presence of these materials and phases is natural due to the inherent porosity of gypsum mortar and the fact that this architectural structure has been buried in the soil for several centuries.

Conclusion 
The use of semi-fired, semi-pounded gypsum, with the addition of sand as an intermediate mortar between stones, as well as for pointing in various sections of the outer walls of Ojan Castle, indicates the use of processed gypsum mortar in cold regions such as Bostanabad in the northwest of the country. As we know, in the field of conservation and restoration of historical architecture, the use of authentic materials that correspond to the original substance is crucial for preserving the authenticity, historical value, and cultural significance of ancient artifacts.
Based on this principle, the use of traditionally processed gypsum for constructing traditional mortar in the conservation of this ancient site can be considered significant in terms of maintaining authenticity. Considering recent seasons of excavation and access inside the castle, conducting similar tests on samples of interior plaster can reveal the differences between the mortars used on the outer and inner surfaces. This information can provide insights for proposing restoration and conservation procedures for the site.