Elemental Analysis of Silver Coins during the Umayyads through the PIXE Method

IANSA 2019 ● X/1 ● 65–75 Zohreh Jozi, Parasto Masjedi Khak, Alireza Nosrati: Elemental Analysis of Silver Coins during the Umayyads through the PIXE Method 66 After Hisham, there began a decline of Umayyad rule, such that three caliphs, namely Walid ibn Yazid (746 AD/ 125 AH), Yazid ibn Walid (747 AD/126 AH), and Ibrahim bin Walid (747 AD/126 AH) came to power within only one year. Ultimately, the last Umayyad caliph came to rule, i.e. Marwan ibn Muhammad (748–753 AD/127–132 AH) and this dynasty came to an end after Marwan was defeated by the Abbasids. The last survivor of the Umayyads went to Andalusia (Spain) and founded the branch known as the Spanish Umayyads, which survived from 759 to 1043 AD/ 138 to 422 AH (Hawting, 1986, p.41). 2. Mint of coins in the Umayyad period In the Umayyad period, Muslims used Sassanian and Byzantine coins in their exchanges until the reign of Abd al-Malik ibn Marwan (Ibn KHaldun, 1980). Due to the neglect of governments, impure dinars and dirhams with a high degree of impurity became common ((Ibn Khaldun, 1980, 500), which was followed by Abd al-Malik’s command for minting coins for the first time in 695 AD/ 74 AH (Ibn al-Athir, 1987, p.167; Baladhuri, 1866, p.651). Today, the oldest coins remaining from Abd al-Malik ibn Marwan’s period date back to 699 AD/ 78 AH (Yousef Faraj Allah, 1985, p.37). Abd al-Malik appointed a steady carat for dirham and dinar and, accordingly, he put official currency with its own characteristics into operation and limited the right to mint coins by assigning it only to the state mints (Baladhuri, 1866, p.473). After Abd al-Malik ibn Marwan, the minting of coins in the periods of Walid ibn Abd al-Malik, Sulayman ibn Abd al-Malik, and Umar ibn Abd al-Aziz continued in the same way (Maqrizi, 1967, p.58). During the reign of Yazid bin Abd al-Malik (722–726 AD/ 101–105 AH), plenty of strict rules were applied to the weight of coins (Baladhuri, 1866, p.652). When Hisham ibn Abd al-Malik came to power (726–746 AD/ 105–125 AH), he closed the mints in all cities except Wasit; and dirham coins were minted only in Wasit (Maqrizi, 1967, p.16). This process continued until the period of Walid ibn Yazid and, during Marwan ibn Muhammad’s period (748–753 AD/ 127–132 AH), he – the last Umayyad caliph – also minted some dirhams in the Harran mint in addition to Wasit (Baladhuri, 1866, p.17). 3. Research background Several studies have been carried out in connection with coins pertaining to the early years of the Islamic era. In this regard, Ziad conducted his studies, where he collected a series of Umayyad silver coins that had been minted in the Wasit mint between 87 and 120 AH (708–741 AD), through the XRF method. His findings highlight the high quality of the coins minted in this mint, where he reported an average silver content of 94.71% in the coins. His studies showed that there was a clear tendency towards betterquality dirhams over time, which may be due to the high control and constraints on the policies of coin minting by the rulers (Ziad, 1999). Al-Kofahi and Al-Tarawneh analyzed a total of 7 silver dirhams belonging to the Ayoubian era (564–648 AH) and 9 coins belonging to the Mamalik period (648–865 AH) by the XRF method. Their results showed that the amount of silver in the Ayoubian coins was between 8% and 52%, while a content of 12% to 55% silver existed in the coins belonging to the Mamalik era. The amount of copper in the coins belonging to the Ayoubian and Mamalik periods varied from 5% to 79%, and the high levels of copper in these coins has been attributed to the counterfeiting that took place in some mints (Al-Kofahi, Al-Tarawneh, 2000). In other study, Ben Abdelouaheda analyzed a collection of 28 silver coins belonging to the Islamic period (from the 7th to the 15th century) via the PIXE method. His results showed that coins pertaining to the Umayyad and Abbasid periods enjoyed a high carat; however, the coins belonging to the Fatimid and Zirid periods did not enjoy a good carat since their silver content was significantly reduced and their copper content increased. This issue has been attributed to the dominant economic conditions and the surveillance system of these states (Ben Abdelouaheda et al., 2010). Figure 1. Location of the mints of Umayyad coins in this study. IANSA 2019 ● X/1 ● 65–75 Zohreh Jozi, Parasto Masjedi Khak, Alireza Nosrati: Elemental Analysis of Silver Coins during the Umayyads through the PIXE Method 67 No. 1: Abd al-Malik ibn Marwan coin minted in Basra in 82 AH with the weight of 2.5 g. No. 2: Abd al-Malik ibn Marwan coin minted in Wasit in 85 AH with the weight of 2.3 g. No. 3: Walid bin Abd al-Malik coin minted in Damascus in 88 AH with the weight of 2.8 g. No. 4: Walid bin Abd al-Malik coin minted in Wasit in 88 AH with the weight of 2.8 g. No. 5: Walid bin Abd al-Malik coin minted in Wasit in 90 AH with the weight of 2.8 g No. 6: Walid bin Abd al-Malik coin minted in Wasit in 90 AH with the weight of 2.7 g. No. 7: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g. No. 8: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g. No. 9: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g. No. 10: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g. No. 11: Walid bin Abd al-Malik coin minted in Darabgerd in 94 AH with the weight of 2.8 g. No. 12: Walid bin Abd al-Malik coin, minted in Kerman in 94 AH with the weight of 2.7 g. No. 13: Walid bin Abd al-Malik coin, minted in Merv in 95 AH with the weight of 2.8 g. No. 14: Walid bin Abd al-Malik coin, minted in Merv in 95 AH with the weight of 2.8 g. 0 3 cm 0 3 cm


Mint of coins in the Umayyad period
In the Umayyad period, Muslims used Sassanian and Byzantine coins in their exchanges until the reign of Abd al-Malik ibn Marwan (Ibn KHaldun, 1980). Due to the neglect of governments, impure dinars and dirhams with a high degree of impurity became common ((Ibn Khaldun, 1980, 500), which was followed by Abd al-Malik's command for minting coins for the first time in 695 AD/ 74 AH (Ibn al-Athir, 1987, p.167;Baladhuri, 1866, p.651). Today, the oldest coins remaining from Abd al-Malik ibn Marwan's period date back to 699 AD/ 78 AH (Yousef Faraj Allah, 1985, p.37). Abd al-Malik appointed a steady carat for dirham and dinar and, accordingly, he put official currency with its own characteristics into operation and limited the right to mint coins by assigning it only to the state mints (Baladhuri, 1866, p.473).

Research background
Several studies have been carried out in connection with coins pertaining to the early years of the Islamic era. In this regard, Ziad conducted his studies, where he collected a series of Umayyad silver coins that had been minted in the Wasit mint between 87 and 120 AH (708-741 AD), through the XRF method. His findings highlight the high quality of the coins minted in this mint, where he reported an average silver content of 94.71% in the coins. His studies showed that there was a clear tendency towards betterquality dirhams over time, which may be due to the high control and constraints on the policies of coin minting by the rulers (Ziad, 1999). Al-Kofahi and Al-Tarawneh analyzed a total of 7 silver dirhams belonging to the Ayoubian era (564-648 AH) and 9 coins belonging to the Mamalik period (648-865 AH) by the XRF method. Their results showed that the amount of silver in the Ayoubian coins was between 8% and 52%, while a content of 12% to 55% silver existed in the coins belonging to the Mamalik era. The amount of copper in the coins belonging to the Ayoubian and Mamalik periods varied from 5% to 79%, and the high levels of copper in these coins has been attributed to the counterfeiting that took place in some mints (Al-Kofahi, Al-Tarawneh, 2000). In other study, Ben Abdelouaheda analyzed a collection of 28 silver coins belonging to the Islamic period (from the 7 th to the 15 th century) via the PIXE method. His results showed that coins pertaining to the Umayyad and Abbasid periods enjoyed a high carat; however, the coins belonging to the Fatimid and Zirid periods did not enjoy a good carat since their silver content was significantly reduced and their copper content increased. This issue has been attributed to the dominant economic conditions and the surveillance system of these states (Ben Abdelouaheda et al., 2010).  No. 8: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g.
No. 9: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g.
No. 10: Walid bin Abd al-Malik coin minted in Wasit in 92 AH with the weight of 2.8 g.
No. 11: Walid bin Abd al-Malik coin minted in Darabgerd in 94 AH with the weight of 2.8 g.
No. 12: Walid bin Abd al-Malik coin, minted in Kerman in 94 AH with the weight of 2.7 g.
No. 13: Walid bin Abd al-Malik coin, minted in Merv in 95 AH with the weight of 2.8 g.
No. 14: Walid bin Abd al-Malik coin, minted in Merv in 95 AH with the weight of 2.8 g.

Umayyad mints
In the various resources and studies, reference is made to more than eighty Umayyad mints where coins had been minted and, except for the Damascus, Afrique (Kairouan), and Andalusia (Córdoba) mints, all the other ones were located in Iran and Iraq, i.e. the land belonging to the Sassanid Empire. The first dinar coin of the Umayyad dynasty dates back to 698 AD/ 77 AH without the name of any mint; and the first dirham coin was minted in 699 AD/ 78 AH in Shagh al-Teimareh mint, central Iran (Shams Eshragh, 1990, pp.150-154). In this study, coins that were minted in Damascus (Damascus was the capital of the Umayyad dynasty from 657 to 748 AD/ from 36 to 127 AH), Wasit, Merv, Basra, Darabgerd, and Kerman have been analyzed ( Figure 1).

Research objectives
Since the territory under the control of Umayyad Caliphs also included areas under the domination of the Sassanids, the aim of this study is to examine whether or not the mineral ores used in the Umayyad coinage were different from those of the Sassanid period. Moreover, with regard to the studied coins belonging to the years 703 to 749 AD (82 to 128 AH), their economic status and the carat of the coins of this time period will be examined.

Preparation method
In this study, coins pertaining to the Umayyad period, which are kept in the archive of the Museum of Southeast Iran, were examined. To remove contamination from the surface of specimens, the coins were first washed with distilled water, then washed in acetone, and, finally, washed again in distilled water and placed in the room to dry. Thereafter, they were transferred to the Van de Graaff accelerator of the Atomic Energy Organization so that the necessary experiments could be conducted on them through the PIXE method. In total, 42 silver coins were studied, as described below. Two of these coins belonged to the Abd al-Malik ibn Marwan period, and had been minted between 703 and 706 AD (82 to Figure 2).

Experiment
To measure the elemental concentration of the specimens, a proton beam with an energy of 2 MeV and current of about 2-3 nanoamperes was used. The required proton beam was produced by the 3 MV Van de Graaff accelerator available in the Physics and Accelerator Research Institute. The energy of X-rays was measured by a Si (Li) detector, which was located at 135 degrees to the descending beam; the multichannel system then displayed the obtained spectrum. In addition, GUPIX software was used to quantitatively measure the constituent elements of the specimens (Maxwell et al., 1989).
In this study, the standard Merck Art.2700 was used for calibration. Overall uncertainty for the PIXE method was 5% for major elements; 5-10% for minor elements, and 15% for trace elements. The results of this study are shown in Table 1.

Results and Discussion
In this study, coins of the Umayyad Caliphs, which had been minted in different mints, were examined. The coins belonging to the Hisham ibn Abd al-Malik and Walid ibn Abd al-Malik periods were the most frequent ones among the studied coins, while Wasit was the most active mint. From among the 42 silver coins under study, 32 were minted between 706 to 749 AD (85 to 128 AH) in Wasit mint.
The amount of silver in these coins varies from 86.13% to 90.92% (Table 1). The lowest amount of silver belonged to coin numbered 41, which was minted in 747 AD (126 AH) in the period of one of the three Umayyad caliphs, namely Walid ibn Yazid, Yazid ibn Walid, and Ibrahim bin Walid.
The highest amount of silver in these 42 coins belongs to the coins minted during the periods of Walid ibn Abd al-Malik and Hisham ibn Abd al-Malik, when the Umayyad government was at its zenith. The study of these coins shows that various mints, except for a few ones, have minted coins with a clear weight (i.e. 2.8 grams), which is indicative of a strong surveillance system over the activity of the mints. This study shows that a large fluctuation can be observed in the weight of coins pertaining to the Abd al-Malik ibn Marwan period. The coin numbered 1, minted in Basra in 703 AD (82 AH), weighs 2.5 grams, and coin numbered 2, minted in 706 AD (85 AH), weighs 2.3 grams.The amount of silver content in these two coins also ranges from 87.29% to 88.03% (Table 1). The fluctuations in the weight and amount of silver in these two coins can be attributed to the political situation of this period. At that time, the country was in severe chaos: the period when Abd al-Malik reached power and could empower the Umayyad government.
The amount of gold in the studied coins is between 0.28% and 0.91%, and the average gold in these coins is 0.58%.    Since an amount of gold between 0.2% and 1.5% represents the probable use of Cerussite ore in the minting of coins (Meyers, 1979;Sodaei et al., 2013), the amount of gold in the studied coins shows that Cerussite ore had been used in their minting. Study of the silver coins minted in the mints of the Sassanid era shows that Cerussite ores were used to mint these coins (Tables 2 and 3).
On the other hand, a look at the carat of the Sassanid coins shows that these coins, except for those coins of periods when the state had no political and economic stability, enjoyed a high carat and the amount of silver in them sometimes reached above 98% (Hajivaliei et al., 2008;Sodaei et al., 2013;Khademi Nadooshan and Khazaie, 2011;Ben Abdelouaheda et al., 2010). A similar situation is also observed in the Umayyad era in that the Umayyads could mint high-carat coins whose purity sometimes reached 90.95%, while coins with carats below 90% belong to the periods of the Umayyads' decline and of internal conflicts in their government. For example, Abd al-Malik ibn Marwan came to power when the Umayyads' caliphate was on the verge of collapse, and his minted coins at this time were below 90%, but when the situation became better after his reforms, then the carat of coins increased to more than 90%; another example belongs to the late period of the Umayyads, when three caliphs ("kings") came to power during just one year, and the carat of silver coins dropped again.
In Figure 3, the distribution of gold, silver, and lead elements in Umayyad coins has been illustrated using Dplot software. This chart shows that there was no single ore deposit that was used in the minting of the studied coins, and it is possible to divide the coins into one main group, i.e. GA, and seven subgroups, i.e. GB, GC, GD, GE, GF, GG, and GH (Figure 3).
These results show that not only was one single silver source not used in the coins minted at Basra, Wasit, Damascus, Merv, Darabjerd and Kerman mints, but several sources, and that even different bars were used in the minting of coins from one mint in a given period of time.
On the other hand, the best coins were minted in such mints as Damascus and Wasit -due to their political and commercial importance; therefore, the coins of these two mints from 709 to 746 AD (88 to 125 AH) have always held a carat over 90%. Table 3. Percentage of elements present in Sasanian coins by XRF (Sodaei et al., 2013, p.166). On the other hand, the best coins were minted in such mints as Damascus and Wasit -due to their political and commercial importance; therefore, the coins of these two mints from 709 to 746 AD (88 to 125 AH) have always held a carat over 90%.

Conclusion
Overall, these findings indicate that there is a direct relationship between the political and economic status of the Umayyad caliphate during a given period and the carat of the coins minted at that time; for example, the coins minted during the period of Abd al-Malik ibn Marwan (82 AH) at Basra mint are of a lower carat than the coins minted during the period of Umar ibn Abd al-Aziz in Basra (100 and 101 AH). Furthermore, the coins minted in the late era of the Umayyad caliphate are of lower carat since the government was weakened over this period, such that the three caliphs only ruled over the period of a year (126 AH).The comparison of the amount of gold, silver, and lead in the Sassanid coins with that of the coins minted in the Umayyad period shows that the Sassanid mints, especially those active at the beginning of the Islamic conquests, were still used during the Umayyad period.The comparison of elements used in the Umayyad coins with the elements used in Sasanian coins shows that the technology of extracting and minting of silver in the Umayyad period did not differ from that of the Sasanian period. The economic prosperity of the time, the strong monitoring system over the activities of their mints, the availability of good reserves of silver, and the presence of silver ore of high purity, ensured that the Umayyad coins enjoyed a very good carat. In this regard, Damascus served as the capital, while Wasit enjoyed commercial and military importance; thus, the mints of these two cities managed to mint the coins with the highest carat.