سنجش عیار نقره سکه‌های درهم عباسی قرن دوم هجری، متعلق به موزۀ ملی ایران، با استفاده از آزمایش XRF

 
Silver Finesse of Coinage of 2nd AH, from the collection of National Museum of Iran, Using XRF Method
 
Introduction
Investigating coins reveals firsthand and immediate information to understand “past”. Enjoying technology and providing an interdisciplinary context can extract physical and chemical data, which potentially gain double relevant value inaccessible in the absence of the technology. The data that achieved by such nondestructive analyzing methods result most valuable information which necessarily is absent in historical written sources or numismatics naturally lacks it, because of unknown archaeological provenance, comparing to in situ material culture. XRF portable device used to measure silver finesse of some Abbasid coins of 2nd AH century. The authors statistically studied the results that achieved quantitative-qualitatively. The consequent finesse, as weight percentage, indicates that finesse of capital city of Madinat al-Salam is distinguished and higher than silver finesse of coins from the other mints. Furthermore, the former has lower characteristic metal impurities, copper and lead, comparing to the coins of mints other than capital city. One can suggest copper impurity as intentional addition to manipulate alloy finesse, whereas lead impurity as technical negligence and with no effect on finesse.
Materials and Methods
Some 41 coins of Madinat al-Salam and other mints picked up of the collection of National Museum of Iran, while 24 minted in Madinat al-Salam, the capital, and the other 17 ones coined in the other mints. A portable XRF instrument used to analyze the coins. The experiment focused on silver, as the base of dirhams, copper and lead. The results placed on charts and statistically analyzed.
Results
Despite of physical similarities of the coins, rate of copper in the coins of the capital, Madinat al-Salam, is lower than the coins of other mints, while the rate of lead follows the same equality, where it is higher in the out of capital coins. The copper rate has inverse ratio to the silver finesse, whereas the former decreases when the latter increases, and vice versa. However, statistical analysis indicates no relevance between fluctuation of lead and silver finesse, while getting away from capital, Madinat al-Salam causes higher rate of lead.
Conclusions
The authors suggest an intention in higher purification of the Madinat al-Salam dirhams, in which the authorities attempted to manipulate the rate of copper and present finer dirhams for the capital, however, we do not know why. One can suggest the fluctuation of lead as a technological relevance, which means further distance from the capital leads to more rate of lead that probably rooted in weakness of facilities at outer mints as a relevance to Political sovereignty. It means harder purification of silver, however, there is no meaningful connection between rates of lead and copper.
Funding
Present paper used postdoctoral Allameh Tabatabaei fund of Iranian National Elite Foundation, which hosted by Dr. Gholamreza Avani.
 
Authors’ Contribution
Hossein Sabri, Postdoctoral fellow (author); Dr. Gholamreza Avani (author); Farah Sadat Madani (author, laboratory activities).
Conflict of Interest
The authors declare no conflict of interests.
 
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