Silver Anomalies in Jerusalem Pottery
What they Reveal about the Second Temple Period
Researchers in the Environmental Energy Technologies Division (EETD) of the Lawrence Berkeley National Laboratory (Berkeley Lab) and at Israel's Bar-Ilan University have discovered high concentrations of silver in samples of pottery from excavations in Jerusalem (see Figure 1) dating from the late Second Temple period, i.e., the first century BCE (Before the Common Era) through 70 CE (Common Era).
This is the first study ever conducted on silver in archaeological ceramics.
The research team-David Adan-Bayewitz, Associate Professor at Bar-Ilan in Ramat-Gan, Israel and guest at Berkeley Lab, and Frank Asaro and Robert D. Giauque of EETD-performed measurements on 1,200 pottery vessels from 38 sites in Roman Judea (present-day Israel)(see Figure 2).
They used high-precision X-ray fluorescence (HPXRF) and instrumental neutron activation analysis (INAA). The Berkeley Lab team developed a variation of INAA, the INAA coincidence technique, specifically for measuring silver concentrations in archaeological samples, to check the results of HPXRF and conventional INAA.
The research was funded by the U.S. National Science Foundation and the United States-Israel Bi-national Science Foundation.
The major finding is that samples of pottery from Jerusalem during this era show anomalously higher concentrations of silver than samples from all other non-urban sites dating from the same period (see Figure 3). Many samples from Jerusalem and other sites were otherwise indistinguishable in date, shape, and chemical composition. Although high silver content was also detected in pottery found at other urban sites, many of the Jerusalem samples had higher silver values than any of the samples from other cities.
"Because pottery samples containing larger amounts of silver were all recovered from sites in cities, and because the cities were distant from one another, we concluded that the silver anomalies are associated with human activity," Asaro says. Natural causes do not explain the geographical distribution of samples with high silver content. The researchers also concluded that silver was washed into the pottery through the action of groundwater.
"One of the most important results of our silver work is that our findings suggest that the measurement of silver in pottery may be a useful tool for evaluating archaeological remains and patterns of urban contamination in antiquity," says Adan-Bayewitz.
Jerusalem In the Second Temple Period
The researchers note that Jerusalem and its temple were the religious and national focus of Jews throughout the Roman Empire during the Second Temple Period, leading to substantial growth of the city. The Roman scholar Pliny the Elder, who lived during this time, called Jerusalem "by far the most famous city of the East." Jewish pilgrims to Jerusalem contributed to the city's wealth, and continual donations to the temple made it a target for plunder.
Josephus, the first-century Jewish historian who witnessed the siege and conquest of Jerusalem in 70 CE, wrote "Of the vast wealth of the city, no small portion was still being discovered among the ruins. Much of this the Romans dug up, but the greater part they became possessed of through the information of the prisoners, gold and silver and other most precious articles, which the owners in view of the uncertain fortunes of war had stored underground."
The researchers suggest that the silver values they measured in Jerusalem pottery samples may be analytical evidence of the city's wealth during the Second Temple Period. The results of this research were published in the August 2006 issue of the journal Archaeometry in an article titled "The discovery of anomalously high silver abundances in pottery excavated in Jerusalem."
Development of Coincidence INAA
Asaro and his colleagues have for decades been applying neutron activation analysis and X-ray fluorescence techniques to study the origin of archaeological artifacts. Asaro has collaborated with Adan-Bayewitz on artifacts from the Jerusalem region since the early 1990s. In 1985, Asaro was instrumental in finding the iridium anomaly that first hinted that dinosaurs became extinct because of an asteroid impact, and in providing evidence that "Drake's Plate" (a metal plate purportedly left by explorer Sir Francis Drake on the Pacific coast of North America) was an archaeological forgery.
In neutron activation analysis, a sample is bombarded by neutrons in a research reactor. Artificial radioactive isotopes of certain elements are formed that can be identified by their characteristic gamma-ray signatures. In the X-ray fluorescence technique, a sample is exposed to X-rays. Atoms in the sample absorb the energy, knocking away an electron from an inner shell. The atom emits a unique X-ray signature when an outer shell electron drops to the inner shell to replace the missing electron.
When Asaro and Giauque began applying these techniques to the Second Temple-era samples and measured anomalously high silver concentrations, they began taking a closer look. "I was mistrustful of INAA measurements of abundances with a single detector and X-ray fluorescence measurements to measure silver accurately in archaeological samples," says Asaro, "so we developed a new and more reliable way of detecting silver using coincidence measurements with INAA."
Their method involves using two detectors to measure the radiation emitted by samples subjected to neutron activation at two gamma-ray energy ranges. When the single detector and the coincidence INAA and HPXRF methods all agreed on the silver anomaly, the research team was satisfied that their data were correct.
For more information, contact:
- Frank Asaro
- (510) 486-5433; Fax (510) 486-5401
A report on the development of coincidence instrumental neutron activation silver analysis is titled "High-Sensitivity Measurement of Silver in Pottery by Coincidence INAA," by Frank Asaro, David Adan-Bayewitz, Fred Stross, Frank Garcia, and Alan Smith, LBNL-55396.
More on Frank Asaro's work on provenance of ancient artifacts.
On dinosaur extinctions and neutron activation analysis
On the Drake's Plate forgery.
More on Bar-Ilan University's Martin (Szusz) Department of Land of Israel Studies and Archaeology.