Archaeometallurgical Characterization of Numismatic Artifacts

Abstract

& The discovery of metals and alloys greatly contributed to the development of human civilizations; their role in shaping history is recognized by the scientific community even through the denomination of some archaeological periods (Copper Age, Bronze Age, and Iron Age). Archaeometallurgy appeared from the application of usually non destructive analytical techniques for the characterization of cultural heritage objects, with emphasis on metal artifacts. This article presents a case study regarding the application of fast and non-destructive methods (energy dispersive X-ray fluorescence and metallurgical microscopy) for the characterization of selected numismatic artifacts, thus obtaining information regarding their composition, authenticity, and state of preservation.

A Review of Energy Dispersive X-Ray Fluorescence (EDXRF) as an Analytical Tool in Numismatic Studies

“…Similarly, an analysis of a set of six dinheiros from the first Portuguese dynasty was developed by Ramos de Oliveira 68 in order to evaluate their elemental composition, confirming a billon alloy (copper-silver) in four of the coins and a reduced content of silver in the remaining two. This fact is compatible with the social and economic Portuguese reality during the reign of Fernando I. Fierascu et al 69 presented in a study the archaeometallurgical characterization of four demonetized Iberian coins, two Spanish and two Portuguese, from a private collection, with different values, characteristics, and years of manufacture. The analysis was performed using an X-ray fluorescence spectrometer, with a Si(PIN)-detector with 255 eV resolution at 5.9 keV (Mn Ka line).…”

“…If the alloys or the morphological characteristics are not consistent with the known data, one can conclude that the coins are not genuine. 69 EDXRF has been used for the study of chemical composition and it provides a fast and accurate method for non-destructive counterfeit coins identification. 71 Hall and Kovacs 72 analyzed 44 gold Roman coins from the Republican era.…”

Analytical investigation and electrochemical conservation treatment for archaeological copper alloy artifacts from Jordan

“…The loss of parts of these powdery corrosion products formed corrosion pits in the surface of the artifact. As this corrosion reaction is active in the presence of oxygen and humidity in the surrounding environment, it can continue until it completely destroys the artifact [20,[34][35][36][37]. Similar powdery green corrosion spots are appearing on the other three artifacts, which suggests a similar corrosion mechanism, however the corrosion products on those artifacts were not sufficient for XRD sampling.…”

“…The EDX analysis of the next corrosion area appearing as deep corrosion pits between the crystals shows a tin and zinc rich zone with the presence of chlorine (Table 2), which suggests a decuprification process causing copper depletion from the alloy during the active chloride-based corrosion process. The chloride containing burial environment in the archaeological site would have promoted the mobilization of the soluble CuCl 2 -complex outside the alloy, which then underwent oxidative hydrolysis to the powdery basic cupric chlorides (Cu 2 (OH) 3 Cl) detected in the XRD analysis [34][35][36][37]. The SEM images of the cross-section taken from the snake-shaped bracelet shows two alloy zones covered with an outer corrosion layer.…”

Surface, Elemental and Electrochemical Characterizations of Ancient Coins By Non – Destructive Techniques

“…Based on these metals, the. coins are of importance for the historians and for the numismatics collections [5]. The surface of metallic is marked by a chemical, electrochemical and microbiological changes.…”