Analysis of Gold Hoard from Late Roman/Early Byzantine Period Found in Jordan
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Figure 1. Region in Jordan where gold hoard was found (Tell Nimrin). (a) map of region: Tell Nimrin lies just north of Dead Sea and near Jordan River. (b) View of local region from top of Tell Nimrin. (c) Archaeological site. (d) ancient walls.
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Fig. 2. Photos of three gold coins from the hoard of 34 found at Tell Nimrin in Jordan. The emperors shown and the range of the coin dates are: (a) Valentinian, 364-367 A.D.; (b) Basiliscus, 475476 A.D.; and (c) Anastasius I, 491-518 A.D. Top row: obverse (heads) side of the coins; bottom row: reverse (tails side).
TABLE I. List of Roman and Byzantine emperors whose images are stamped on the gold coins found at Tell Nimrin. Also listed are the range of coin dates, the cities where the coins were minted and the number of each.
EMPEROR
DATES
MINT
364-367 AD Valens 364-367 AD Valentinian 457-473 AD Leo I Basiliscus and Marcus 475-476 AD Zeno 476-491 AD Anastasius I
Antioch Antioch Constantinople Constantinople Constantinople Thessalonica Constantinople
491-518 AD
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NO. OF COINS
8 11 3 I 7 1 3
EXPERIMENT Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM/EDS) The most usefhl analytical technique employed was SEM/EDS, which could quickly evaluate the gold content and minor elements in the near-surface regions of the coins and earrings. With 34 coins to analyze and with limited time, it was important to use a high-speed method. Furthermore, no surface preparation was required--or allowed--for these analyses. Although the gold objects had been buried for approximately 1500 years, their surfaces are still electrically conductive, since gold is relatively unreactive chemically. The instrument used was a JEOL 840 Scanning Microanalyzer, located in the Department of Macromolecular Science at Case Western Reserve University (CWRU), Cleveland, Ohio. The sensitivity of the EDS system for elemental analysis by characteristic X-ray emission is about 0.1 wt % for elements heavier than sodium, and the precision is approximately + 0.05 wt %. A reference standard--a modem British gold sovereign--was studied by SEM/EDS before the ancient coins were examined to become familiar with the X-ray spectra of gold and copper. Density Measurements As part of the coin analysis, the densities of several coins from the hoard were measured. From the density measurements--and the EDS information on the minor element content--the bulk gold content could be calculated to compare with the near-surface content from EDS data. The method for evaluating the density of these ancient coins was the ancient Archimedes approach based on his principle that the loss of weight of a submerged object equals the weight of the liquid displaced. The liquid used was distilled water with Kodak Photo-Flo added as a wetting agent to reduce surface tension around the wire supporting the coin; the instrument used was a Mettler analytical balance and a Mettler 33340 Density Determination Kit. The density measurements were conducted in the Department of Mate
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