PIXE analysis of ancient Jordanian pottery

Nuclear Instruments and Methods 181 (1981) 527-530 © North-Holland Publishing Company

PIXE ANALYSIS OF ANCIENT JORDANIAN POTTERY Naser SALEH *, Lars-Eric CARLSSON Department o f Nuclear Physics, Lund Institute of Technology, Lund, Sweden Awni B. H A L L A K Department o f Physics, University of Jordan, Amman, Jordan and Crystal BENNET British Institute of Archaeology and History, Amman, Jordan

Proton-induced X-ray emission (PIXE) has been applied for the determination of 18 elements (Si, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Ba and Pb) in two groups of pottery from two different sites in Jordan, Biblical Bozrah (BB) and Amman Citadel (AC). The analysis showed that the elements Zn, Rb, St, Zr and Ba were the most useful elements to study to be able to differentiate between the two groups of pottery.

1. Introduction

may arise from dirt on the surface of the pottery. (i.i) Variability in the degree of local homogeneity. This may arise from the variable degrees of fineness of particles within different samples. Pottery was supplied by the British Institute o f Archaeology and History in Jordan. To avoid the influence of surface contamination, the surface portion of each specimen was discarded. To assure that the sample employed was truly representative of the overall composition of the given specimen being analyzed, 5 g of each sample was ground and 0.5 g was further pulverized in a silicon mortar. Samples were pressed into thick pellets in a clean room and mounted in 2" × 2" (5.1 cm X 5.1 cm) slide frames.

Establishing the origin of various archaeological objects is an important problem in archaeology. As archaeological materials, ancient potteries are specially important, and by analyzing their composition we hope to reveal some of the information hidden in them. Firstly, major element concentrations define the type of the raw materials used. Secondly, trace element concentrations can reveal something about the source or origin o f the potteries. With those goals in mind, PIXE analysis of two groups of p o t t e r y samples from two different sites in Jordan has been made (fig. 1).

2. 2. Measurements

2. Experimental

The samples were bombarded in vacuum by 2.55 MeV protons from the Lund Pelletron. The emitted

2.1. Samples

Lebn/n~ .

The samples studied consist of pieces o f pottery from the iron age ( 7 0 0 - 5 0 0 BC), the Roman period (170 B C - 3 9 0 AD) and the Byzantine period ( 3 9 0 1453 AD). They are summarized in table 1. Care must be taken in sampling pottery for the following reasons: (i) Surface contaminations: these

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* Permanent address: Department of Physics, University of Jordan, Amman, Jordan.

Fig. 1. Geographical locations of pottery sites in Jordan. 527

XIII. MISCELLANEOUS APPLICATIONS

N. Saleh et al. / PIXE analysis o f ancient Jordanian pottery

528

3. Results and discussion

Table 1 Summary for various pottery samples Sample

Period

Site found - year

BB BB BB BB BB

7 0 0 - 6 0 0 BC 7 0 0 - 6 0 0 BC 7 0 0 - 6 0 0 BC early 600 BC approx. 600 BC

Biblical Biblical Biblical Biblical Bilbical

Bozrah Bozrah Bozrah Bozrah Bozrah

1973 1973 1972 1973 1973

late Roman-Byzantine late Roman-Byzantine Byzantine Byzantine Byzantine

Amman Amman Amman Amman Amman

Citadel Citadel Citadel Citadel Citadel

1975 1975 1975 1975 1975

1 2 3 4 5

AC 1 AC 2 AC 3 AC 4 AC 5

X-rays were detected in an 80 mm z Si(Li) detector. Pulse-height spectra were accumulated in an ND-6600 and recorded on magnetic tape for analysis on a U n i v a c - l l 0 0 with the programme HEX [1]. More details of the PIXE set-up in Lund are given elsewhere [2,31.

BB AC I

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The concentration of elements found in pottery samples of groups BB and AC are given in table 2. The accuracy for elements heavier than Fe is about 10% when the concentration is well above the detection limit. One o f the aims of this analysis was to identify those elements which would facilitate differentiation of the two groups of pottery. As a first step, index elements were identified, i.e., those elements which vary the most from one group to the other and the least within the same group, e.g., Zn, Rb, Sr, Zr and Ba in fig. 2. After having decided which elements would be the most useful in distinguishing between the two groups of pottery, regional discrimination can be obtained more clearly from correlation diagrams of specific elements such as S r - B a and R b - S r - Z r in fig. 3. In the triangular plot of Rb, Sr and Zr, the concentrations of each element relative to the total concentration of all three elements are

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Fig. 2. Distribution of Si, K, Ca, Ti, Fe, Zn, Rb, St, Zr and Ba in the pottery samples. (Symbols BB and AC, see table 2.)

529

N. Saleh et al. / PIXE analysis o f ancient Jordanian pottery Table 2 Elemental concentration in pottery samples Element

Si % K% Ca % Ti % Cr ppm Mn ppm Fe % Ni ppm Cu ppm Zn ppm Ga ppm Rb ppm Sr ppm Y ppm Zr ppm Nb ppm Ba ppm Pb ppm

Site BB

Site AC

MDL a)

Sample 1

2

3

4

5

Sample 1

2

3

4

12.7 2.1 6.9 0.67 130 580 4.7 70 18 67 18 85 519 32 158 19 670 21

13.3 1.8 7.7 0.33 120 430 3.2 19 23 51 15 79 570 14 107 7 610 24

11.3 1.0 11.4 0.35 150 600 2.8 41 18 59 8 102 607 22 133 11 580 22

11.9 1.4 9.9 0.31 130 560 3.2 27 18 58 19 82 497 12 97 4 515 23

10.2 1.7 10.5 0.32 150 680 3.2 29 17 66 6 90 508 16 102 8 510 24

13.1 1.6 8.8 0.36 120 300 3.6 37 13 41 26 60 245 20 230 14 278 53

13.2 1.2 9.2 0.36 100 250 3.3 31 21 48 27 52 243 18 247 16 297 24

11.9 1.3 7.5 0.31 230 590 4.0 213 28 44 22 57 320 22 199 11 326 22

14.1 1.1 6.7 0.76 70 120 2.8 56 10 40 20 50 270 34 240 25 327 33

14.3 1.4 7.3 0.66 60 180 2.1 164 15 37 21 44 220 25 214 29 330 43

0.13 % 88 ppm 104 ppm 50 ppm 40 ppm 30 ppm 51 ppm 7.3 ppm 5.3 ppm 3.5 ppm 3.5 ppm 2.3 ppm 3.1 ppm 5.1 ppm 7.4 ppm 4.1 ppm 70 ppm 6.8 ppm

a) MDL = minimum detection limit.

p l o t t e d . This k i n d o f c o r r e l a t i o n diagram characterizes a g r o u p in a rigorous m a n n e r .

4. C o n c l u s i o n s The d i f f e r e n c e s in t h e c o n c e n t r a t i o n s o f m a j o r elem e n t s (fig. 2) are n o t significant f r o m o n e g r o u p o f

p o t t e r y t o the o t h e r , and it is difficult t o m a k e dist i n c t i o n s based o n t h e s e e l e m e n t s . H o w e v e r , we observed s o m e d i f f e r e n c e s in the a b s o l u t e and relative c o n c e n t r a t i o n s o f s o m e o f t h e trace e l e m e n t s w h i c h m a d e it possible to distinguish clearly b e t w e e n t h e t w o groups.

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Fig. 3. (a) Sr-Ba correlation and (b) a triangular plot of the relative concentrations of Rb, Sr and Zr for the pottery samples.

XlII. MISCELLANEOUS APPLICATIONS

5 30

N. Saleh et al. / P I X E analysis o f ancient Jordanian pottery

The authors would like to thank Drs. K.R. Akselsson and J. Winchester for reading the manuscript. One of us (N. Saleh) is greatly indebted to all members of the PIXE group for their help and extended hospitality. He is also grateful to both the University of Jordan and the IAEA for making his stay in Lund possible.

References [1] H.C. Kaufmann, K.R. Akselsson and W.f:. Courtney Nucl. Instr. and Meth. 142 (1977) 251. [2] K.R. Akselsson and S.A.E. Johansson, IEEE Trans. Nucl Sci. NS-26 (1979) 135.8. [3] L.-E. Carlsson and K.R. Akselsson, this volume, p. 531.