Archaeometallurgical analysis of four silver coins from four different mints of independent sultans of Bengal Текст научной статьи по специальности «Науки о Земле и смежные экологические науки»

УДК 902/904

ARCHAEOMETALLURGICAL ANALYSIS OF FOUR SILVER COINS FROM FOUR DIFFERENT MINTS OF INDEPENDENT SULTANS OF

BENGAL

©2019 Mohammad Abu Al Hasan, ASW Kurny

Four silver coins from four different mints (Sunargawn, Satgawn, Chatgawn and Khalifatabad) of three different independent Bengal sultans from 1334 to 1538 AD have been analyzed by X-Ray Diffraction and EDS. Attempt has been made to understand the pattern of variation in composition of the coins of different periods from different geographical region from east to west within Bengal. The results have been compared with a previously analyzed coin of Ghiyath Al-din Mahmud of Husayin Shahi dynasty. Results of this study show that there is a variation in silver content from 86.70 - 94.39%. Lead, possibly from natural source of silver varied from 0.053 - 0.447%. Aluminum probably intentionally added to the alloy varied from 0.52 - 3.36%. Other elements such as Copper, Gold, Silicon, Iron, Bismuth, Zinc, Germanium, Ruthenium, Barium, and Cesium were also found in the coins.

Keywords: coins, Sunargawn, Satgawn, Chatgawn, Khalifatabad Bengal, X-Ray Diffraction and EDS

Introduction

In recent years, Archaeologists, Historians and Numismatistshavegathered much information about the mediaeval period of Bengal through historical documents, stone/metal inscriptions and coins. Coins are the most important and most authentic artifacts to line up the disorderliness in the chronology of the Bengal sultans. As there is a lack of contemporary written documents of the sultani period in Bengal, coins are the only elements to identify the monetary history, currency circulation patterns and economy. Till now most of the researchers have tried only to rebuild and diminish the confusions in the history of Bengal sultans. Some researchers have also come forward to study the metallurgical aspects of the currency system of the Bengal sultans. The minting technology, purification process of metals, mixing of different other elements with the metals for making the strength etc. can be discovered from Archaeometallurgical analysis of a coin (Hasan, 2013, p.192). As a pioneer, Monwar Jahan of Bangladesh National Museum attempted to determinethe metallic composition of thirteen silver coins including eleven coins of Bengal sultans (Jahan, 1995, p.48). Later, Pranab Chattapaddhay elaborated Jahan's work and tried to find the sources of trade route of silver as a core element of striking coins (Chattapadhayay, 2011, p. 114). Jahan's work is important as a 1st step, but the sum of the percentages do not add up to 100%, he also didn't mention whether there were more elements (Chattapadhayay, 2007, p. 303).

Recently, John Deyell has reported analysis of 33 silver coins of independent Bengal sultans but his results show only the percentages of silver, not of any other elements (Deyell, 2010-11).

The present authors made an attempt to explore, through non-destructive testing methods, the composition of sultani coins to see if the non-destructive techniques could be used to investigate the composition of a large number of sultani silver coins effectively and precisely. One coin of Ghiyath Al-din Mahmud Shah of AH 933 issued from 'Da' mint was analyzed by both X-ray diffraction and EDS (Hasan et al, 2015). In continuation of that study, the analyses of four silver coins of four different mints have been analyzed by x-ray diffraction analysis and EDS.

Descriptions and Experimental results of the Coins

Sample 01

Sultan: Fakhr Al-Din Mubarak Shah, Date: 738AH, Mint: Hadrat Jalal Sunargawn.

Diameter: 24.687mm, Thickness: 02.80mm, Weight: 10.7g

Fakhr Al-Din Mubarak Shah was the 1st sultan of Bengal who declared independence from Sunargawn against Delhi Sultanate and ruled over the eastern part of Bengal forover a decade. Although, Karim mentioned the starting date of Fakhr Al-Din Mubarak Shah as AH739 (Karim, 1960, p. 36), but both gold and silver coins bearing his name and minted in AH 734/1334 ACE (Goron, 2001, p. 166) have been found.However, no coin minted in between

Plate 01

Obverse Legend Reverse Legend

РШШ «F;' ■ Al-sultan al-a'zam fakhr al-dunya wa'l din abu'l muzaffar Mubarak shah al-sultan ШШпщ Yamin khalifat alah nasir amir al-mu'minin

AH 735-736 has been found. All the coins of A coin dated AH 738/1337ACE (Plate 01) has

this sultan were issued from mint Sunargawn been taken as a sample to understand the metal

(Shahnawaz, 1999, p. 81). He always used composition of the early independent sultan of

epithet 'Hadrat Jalal' (Honorable city) before the Bengal at the initial stage of his rule. mint name on his coins (Karim, 2013, p. 326).

X-ray diffraction pattern of Sample 01 (Plate 2)

The XRD pattern(Plate 02) shows of Silver Chlorargyrite (AgCl). No other element approximately 74% silver, with an upper layer has been detected.

The EDS data of the sample 01

Elements Ag Cl Al Sn Cu Na Au Si K Pb Ge Ru

Percentage 86.70 03.32 02.11 02.62 01.44 01.09 0.90 0.69 0.69 0.35 0.046 0.043

* Only three digits after decimal have been counted. The sum may not be 100%.

Sample 02 Diameter: 26.095mm,

Sultan: Shams Al Din Ilyas Shah, Date: 02.415mm, Weight: 10.5g 754AH, Mint: Satgawn.

Thickness:

Plate 03

Obverse

Legend

Al-sultan al-adil shams al-dunya wa'l din abu'l muzaffar ilyas shah al-sultan

Legend

Sikandar al-thani yamin al-khalifa (nasir) amir al-mu'minin

Shams Al Din Ilyas Shah was the 1st independent sultans of Bengal who conquered all the part of Bengal and combined the whole Bengal as a nation. As recognition, he was titled as Shah e Bangala or Shah e Bangalian (Sultan of Bengal). He issued coins from Firuzabad in AH 744 (Mukhopadhyay, 1988, p. 21) and then

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he issued coins from Satgaon in AH 747 (Karim, 1999, p. 184). A coin of Satgawn with the date AH 754 (Plate 3) has been taken as a sample because Satgawn was the most south-western mint of Shams Al Din Ilyas Shah and that will allow knowing the metallic pattern of the coins of distant part of Bengal sultans.

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XRD of Sample 02 (Plate 4)

The XRD data (Plate 4) showing the peak layer of Silver Chlorargyrite (AgCl). No other of silver 88.10% approximately, with an upper element has been detected.

The EDS data of the sample 02

Elements Ag Cl Al Sn Cu Na Au Si Zn Pb Ge Ru

Percentage 88.06 01.46 02.48 02.48 0.78 01.36 01.18 01.95 0.06 0.13 0.058 0.035

■'Only three digits after decimal have been counted. The sum may not be 100%.

Sample 03 Diameter: 30.28mm, Thickness: 02.074mm,

Sultan: Nasir Al Din Mahmud Shah, Date: Weight: 10.4g 84(?) AH, Mint: Arsah Chatgawn.

Plate 5

Legend

Nasir al-dunya wa'l din abu'l mujahid mahmud shah al-sultan

Legend

Al-mu'ayyad bi-ta'yid al-rahman khalifat allah bi'l hujjat wa'l burhan

Nasir al Din Mahmud Shah ruled over Bengal independently for the longest period of time (AH 837-864). An inscription of Gaur indicates that he transferred capital from Firuzabad to Gaur (Ray, Gaur). He issued coins from Khazanah, Dar-ul-Darb, Firuzabad, Satgawn, Nasirabad, Dakhil Banjalia, Khalifatabad, Muazzamabad, Muhammadabad,

Sabtahara (Goron, 2001) and Dakhil ba-takhtgah (Hussein, 2003, p. 118). He also issued coins from Chatgawn, the most south-eastern mint of Bengal. As the mint's location is completely opposite to the previous sample and nearly hundred years of difference, we have chosen a coin of 74(?) from Chatgawn mint.

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The XRD data (Plate 6) showing the peak layer of Silver Chlorargyrite (AgCl). No other of silver 87.3% approximately, with an upper element has been detected.

The EDS data of the sample 03

Elements Ag Cl Al Sn Cu Na Au Si K Pb Fe Bi Ge Ru

Percentage 91.24 1.32 0.52 2.66 0.9 0.83 0.32 0.95 0.73 0.1 0.21 0.14 0.02 0.042

*Only three digits after decimal have been counted. The sum may not be 100%.

Sample 04 Diameter: 23.985mm,

Sultan: Nasir Al Din Mahmud Shah, Date: 02.957mm, Weight: 10.5g 846AH, Mint: Khalifatabad

Thickness:

Plate 7

Legend

Nasir al-dunya wa'l din abu'l muzaffar mahmud shah al-sultan

Legend

Al-mu'ayyad bi-ta'yid al-rahman khalifat allah bi'l hujjat wa'l burhan

Khalifatabad appeared as a mint on coins during the region of Sultan Nasir Al Din Mahmud Shah. Till now the 1st date found from mint Khalifatabad is AH 846 (Karim, 2013, p. 329). This mint town has been identified with the ruins of Khan Jahan in Bagerhat District (Jahan, 1953,

p. 226). Khalifatabad was the most remote mint town surrounded by Sundarbans, that's why it has been taken as a sample (Plate 7) to identify the metal composition of this mint during the middle period of the Independent sultanate of Bengal.

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The XRD data (Plate 8) showing the peak layer of Silver Chlorargyrite (AgCl). No other of silver 89.3% approximately, with an upper element has been detected.

The EDS data of the sample 04

Elements Ag Cl Al Sn Cu Na Au Si Pb Ge Ru Bi Ge Ru

Percentage 87.63 01.14 02.94 02.55 02.03 01.04 01.05 0.79 0.44 0.056 0.043 0.14 0.02 0.042

*Only three digits after decimal have been counted. The sum may not be 100%.

Comparative Metal content of the five

coins

A comparative compositional analysis of elements of four silver coins of the Bengal sultans of three different rulers from four different mints

from Eastern to the western part of Bengal along with previously analyzed coin of Ghiyath Al-din Mahmud Shah of AH 933 from 'Da' mint (Hasan et al., 2015) isgiven below:

Chart: A (shown data in the continuation of time for both eastern and western mint)

Elements Sample 01 Sunargawn AH 738 Sample 02 Satgawn AH 754 Sample 03 Chatgawn AH 84(?) Sample 04 Khalifatabad AH 846 Ghiyath Al-din Mahmud Da (B'dr Shahi type) AH 933

Argentums (Ag) 86.70 88.06 91.24 87.63 94.39

Chlorine (Cl) 03.32 01.46 01.32 01.41 -

Aluminum (Al) 02.11 02.48 00.52 02.94 03.36

Stannum (Sn) 02.62 02.48 02.66 02.55 -

Copper (Cu) 01.44 00.77 00.905 02.03 00.273

Sodium (Na) 01.09 01.36 00.83 01.04 -

Aurum (Au) 00.90 01.18 00.316 01.05 00.989

Potassium (K) 00.69 - 00.73 - -

Silicon (Si) 00.69 01.95 00.953 00.79 00.70

Lead (Pb) 00.354 00.13 00.102 00.447 00.053

Iron (Fe) - - 00.218 - 00.151

Bismuth (Bi) - - 00.142 - -

Zinc (Zn) - 00.06 - - -

Germanium (Ge) 00.043 00.05 00.0193 00.056 -

Ruthenium (Ru) 00.043 00.03 00.0420 00.043 -

Barium (Ba) - - - - 00.042

Cesium (Cs) - - - - 00.042

Comparative Analysis

Deyell reported that silver tanka of Bengal sultans are almost pure silver containingfrom 96-99% (Dayell, 2012-13, pp. 133-137) but

he arrived at this conclusionby misinterpreting incomplete analysis chart of Jahan's thesis (Jahan, 1995, p. 53) cited from another source which we have reported in our previouspaper (Hasan et al,

2015). The XRD data of each coin shows the presence of Silver Chlorargyrite (AgCl) on the surface, which is normally caused bycorrosion. The presence of AgCl proves that the coins didn't go through any heating process in modern period and has preserved its original features (Chattopadhyay, 2013, p. 100). That's why EDS analysis of each coin shows the presence of Chlorine in small percentage.

Silver Percentages

EDS analysis shows that percentage of

silver in the coins of Bengal sultan has increased over the years (Graph 1). In Sample 01, the percentage of silver is little low. Fakhr Al-Din Mubarak ruled over only the eastern part of Bengal. In his early period of ruling, he stroked coins hastily, that may be the reason of his coins containingless silver. This hastiness has been reflected on the calligraphic pattern of the coin. In continuation, Bengal was independent for next

200 years. So, it can be assumed that the stability of the political situation encouraged trade and commerce and increased the economic wealth of the country. It developed trade relations with other kingdoms of the east and imported silver as a surplus in overland and sea trade from places like Yunnan in the South-west, the northern Shan states of China, and eastern Burma where silver mines existed and silver was produced, refined and exported (Hussain, 2013, p. 284). In mediaeval period, price of silver against cowries decreased in Bengal; the price of silver in Bengal was even five times less than the price inMalacca; on the other hand, price of gold in Bengal was six times higher than Malacca (Haider, 2015, p. 99). Sample 03 from the eastern mint Chatgawn contains over 90% silver which indicates our previous assumption of having higher percentage of silver in eastern mints than westerns (Hasan et al, 2015).

Graph 1: Graph of the percentage of silver of the coin from early to later period of Bengal sultans from East to west:

Percentages of Lead and the presence of Aluminum

The percentages of Lead are present in all five coins but in very low quantity (Chart A), less than 0.5%. In south and south-east Asia, silver is refined from lead ore. In mediaeval period, for purifying silver a quantity of adulterated material was put together with a proportionate amount of lead (Mukherjee, 1988, p. 25). According to Ain-i-Akbari (a Mughal writing), one-fourth of lead was put on the top of silver in a hole to make silver bullion for coinage (Allami, 1873, p. 22). If the same method was applied during sultani

period, then coins should contain a remarkable amount of lead. But all the five coins from our experiment showed only a very less amount (Graph 02) of lead which perhaps came as a primary element of ore with silver.

It is interesting to have a good percentage of aluminum in all the coins (Graph 03), 0.523.36%. Aluminum does not exist as a major or minor element in any of the natural sources of silver of south-east China and Burma (Soe, 1990, p. 12). Silver is a soft metal and its need to mix up with other material to increase its hardness while making any object. So, it

Graph 02: Graph of the percentage of Lead in the silver coin from early to later period of Bengal sultan from east to west

demands special concentration to re-investigate sources of silver like galena and Sphalerite do not about the intentionally added material with silver contain aluminum. in minting process because the major natural

Graph 3: Graph of the percentage of Aluminum in the silver coin of the Bengal sultans from early to later period from east to west:

Presence of other elements:

The coins contain tin (Sn), copper (Cu), gold (Au), sodium (Na), potassium (K), silicon (Si), iron (Fe), bismuth (Bi), zinc (Zn), germanium (Ge), ruthenium (Ru), barium (Ba), cesium (Cs). Silver mainly produced as a byproduct of gold, copper, zinc and lead refining. So, these elements can present in a low percentage in the purified silver. Germanium (Ge) and tin (Sn) is minor elements of Sphalerite. Copper is found in galena as a minor element. There are many natural sources of Galena and Sphalerite in Burma and south-east China but individual data of those mines is not present or out of our reach.

Conclusion

Although it is not possible to arrive at a conclusion about the metallurgy of the coins of Bengal sultans by metallurgical analysis of only five silver coins, these data has indicated that more elaborate investigation with a large number of coins could be helpful to arriving in a conclusion.

Acknowledgement

The authors are thankful to Dr. Abdul Gafur (SSO) and Rakibul Qadir (Engineer) for their help in the x-ray diffraction analysis of the coins. The authors are also thankful to Mr. Noman Nasir, a dedicated & passionate person of Numismatics for providing the sample coins.

REFERENCES

Allami, Abul Faz, Ain I Akbari, Vol. I, (translated by H. Blochmann), Asiatic Society of Bengal, Calcutta, 1873.

Chattapadhayay, P. K. and Gautam Sengupta. 2011. History of metals in eastern India and Bangladesh. New Delhi: Pentagon Press.

Chattopadhyay, Pranab K. 2013. Archaeometallurgy of Coins of Bengal. Centenary Commemorative Volume, Bangladesh National Museum, Dhaka.

Chattopadhyay, Pranab K. 2007. In search of Silver: Southeast Asian Source of Silver for The Coinage of Bengal. In Gouriswar Bhattacharya et al (eds.). Kalhär (white Water-lily): Studies in Art, Iconography, Architecture and Archaeology of India and Bangladesh. New Delhi: Kavery Books, -.

Deyell, Jhon. 2012-2013. Further metallic assays of Bengal Sultan Silver Tanka. Numismatic Digest. 36/37, 133-137.

Deyell, John, New Metallic Assays of Bengal Sultan Silver Tankas, Numismatic Digest, vols. 34-5, Nasik, 2010-11, pp. 119-133.

Goron, Stan & J.P. Goenka. 2001. The Coins of Indian Sultanats. New Delhi: Munshiram Manoharlal Publisher Pvt. Ltd.

Haider, Najaf. 2015. Fractional Pieces and Non-Metallic Monies of Medieval India (1200-1857). In Jane Kate Leonard, Ulrich Theobuld (eds.) Money in Asia (1200-1900): Small Currencies in Social and Political Context. Leiden: Brill, 86-107.

Hasan, Mohammad Abu Al. 2013. Archaeometallurgy of the coins of Bengal Sultans: An unexplored way to the study of political, social and economic life of mediaeval Bengal. Journal of History and Civilization. 1, 187-194.

Hasan, Mohammad Abu Al, Dr. Syed Mohammad Kamrul Ahsan & Dr. ASW Kurny. (In press.) 2015. Trial Metallurgical Analysis of a Silver Coin of Bengal Sultan: Explore through methods and Interpretation. Journal of History and Civilization. 2.

Hussain, Syed Ejaz. 2003. The Bengal Sultanate: Politics, Economy and Coins (AD 1205-1576). Delhi: Manohar Publishers & Distributors

Hussain, Syed Ejaz. 2013. Silver Flow and Horse Supply to Sultanate Bengal with Special Reference to Trans Himalayan Trade (13th-16th Centuries). Journal of the Economic and Social History of the Orient. 56(2). 264-308.

Jahan, M. Mir. 1953. Mint Towns of Mediaeval Bengal. Proceeding of the Pakistan Historical Conference. Dhaka. 226.

Jahan, S.A.M Monowar. 1995. Physio-Chemical investigation for the conservation of Museum objects and Archaeological materials of Bangladesh. Unpublished PhD. Thesis, University of Dhaka.

Karim, Abdul. 1999. Banglar Itihas (Sultani Amal). Jatiyo Grontha Prokashan, Dhaka.

Karim, Abdul. 1960. Corpus of the Muslim Coins of Bengal. Dhaka: Asiatic Society of Bangladesh. (Reprint 2013).

Karim, Md. Rezaul, Sultani Banglar Takshal Nagari, Centenary Commemoration Volume, Bangladesh National Museum, Dhaka, 2013.

Mukherjee, B.N. & P.K.D. Lee. 1988. Technology of Indian Coinage. Calcutta: Indian Museum.

Mukhopadhyay, Sukhamay, Banglar Etihasher Dusho Bochor: Shadhin Sultani Amal, Bharti Book Stall, Kolkata, 1988 (4th edition).

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Soe, Kyaw, 1990. The comparative Study of Contents of Zinc and Lead in Ore Samples of Namtu-Bawdwin Mine by Wet Analysis, X-ray Fluorescence and X-ray Diffraction Methods. Unpublished MSc. Thesis. University of Yangon, Yangon, 1990.

About the Authors:

Mohammad Abu Al Hasan, M Phil Researcher, Department of Archaeology, Jahangirnagar University. Dhaka, Bangladesh.

ASW Kurny, Professor, Department of Materials & Metallurgical Engineering, Bangladesh University of Engineering and Technology. Dhaka, Bangladesh.

АРХЕОМЕТАЛЛУРГИЧЕСКИЙ АНАЛИЗ ЧЕТЫРЕХ СЕРЕБРЯНЫХ МОНЕТ С ЧЕТЫРЕХ МОНЕТНЫХ ДВОРОВ СУЛТАНОВ БЕНГАЛИИ

Мухаммед Абу Аль Хасан, А.С.В. Курны

Четыре серебряные монеты четырех различных монетных дворов (Сонаргаон, Сатгаван, Чатгаван и Халифатабад) трех независимых султанов Бенгалии 1334 - 1538 гг. н.э. были проанализированы с применением методов рентгеновской дифракции и энергодисперсионной рентгеновской спектроскопии. Авторы предприняли попытку обоснования закономерности изменения состава монет, отчеканенных в отдельные исторические периоды в различных географических регионах, расположенных с востока на запад на территории Бенгалии. Полученные сведения были сопоставлены с результатами проведенного ранее анализа монете Гийас ад-дина Махмуда из династии Хусайн Шахи. Результаты исследования демонстрируют различное содержание серебра от 86,70% до 94,39%. Содержание свинца варьируется от 0,053% до 0,447%, что может быть обусловлено природным источником серебра. Алюминий был вероятно добавлен в сплав намеренно в количестве от 0,52% до 3,36%. В монетах были также обнаружены другие элементы, такие как медь, золото, кремний, железо, висмут, цинк, германий, рутений, барий и цезий.

Ключевые слова: монеты, Бенгалия, Сонаргаон, Сатгаван, Чатгаван, Халифа-табад, рентгеновская дифракция и энергодисперсионная рентгеновская спек-троскопия

Информация об авторах:

Мохаммад Абу Аль Хасан, магистр философии, научный сотрудник, факультет археологии, Университет Джахангирнагар (Дакка, Бангладеш).

А.С.В. Курны, профессор, кафедра материаловедения и металлургии, Бангладешский инженерно-технологический университет (Дакка, Бангладеш).