[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Especially in ancient times the production of coin

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Especially in ancient times the production of coin alloys depended on the available ores, so the content can vary. For instance the results of the silver 8,0 10,0 12,0 14,0 16,0 18,0 Increasing wear off Ag content [%] dot 10,0 30,0 50,0 70,0 90,0 Cu content [%] triangle Fig. 7.150. Silver plating of Mexican Pesos of 1967; the big line at 10% silver represents the bulk Ag concentration ( ), and the respective copper content ( )
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710 J. Engelhardt Fig. 7.151. The obverse of the silver plated Mexican Pesos; from left to right increasing wear off of the surface layer as determined by the XRF investigation depicted in Fig. 7.150 content of Roman denarii of the year 196 AD in Fig. 7.152 are given, in which the silver content varies between 47% and 62%. Later, the same denarii were analysed again by Butcher [660] using AAS. He observed a better agreement (around 48%) in his results and attributed the less accurate results of Carter to a surface treatment step. The silver is used as amalgam for plating copper-silver coins with purer silver, so that Hg can be found only in the surface layer. A similar technique was used for gilding coins with gold (see Reiff et al. [658]). More information about production techniques and the final compositions can be found in Gale et al. [662] who investigated early Greek coinage. Relation to the Ores Used Many attempts were made to identify the ore used in coins, so that a decision can be made whether the ore was mined near the mint or got by trade to the mint. Metcalf and Schweizer [663] tried to identify the Au content in English silver coins using the “Milliprobe” (an XRF device with a spot of 1 mm 2 ). The English ores have an Au content of 2–3% in contrast to the European 30 35 40 45 50 55 60 65 70 0 4 2 8 10 Number of coin Silver content [%] 6 Fig. 7.152. Variation of the silver content of Septimus severus denarii in the year 196 AD from Carter and Carter [661]
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Methodological Developments and Applications 711 ores with Au content of only 0.3%. But they were not able to find any relation to English coins of the twelfth century. They explained this with the denom- ination of the current coin every 23 years. The coins were remelted and new ones produced. Hrabanek [664] tried to find the relationship between the Bi content of grossus pragensis and the different ores of the Erzgebirge using EDXRF and EMPA. Two groups could be identified with high or low Bi content, but a clear relation could not be achieved due to the low number (25) of coins investigated. For unalloyed silver coins, the Sb and Au content is mostly unaffected by the cupellation process (melting the rough metal with bone ash in cups). Cowell and Lowick [665] were able to determine in AAS and EDXRF investigations that the silver ores used for minting were from different panjher mines. As criteria for unalloyed coins they used the remaining copper content, which must be below 0.5%.
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