7/22/2023 0 Comments Electrum coin mining![]() After treatment, the gold was basically pure.Īfter cementation, the gold was tested, or “assayed,” to determine its purity, then collected and delivered to some other part of the city for consolidation in large amounts (the absence of crucibles at sector PN indicates that consolidation was done elsewhere). During the heating, salt vapors attacked the electrum and converted its silver to silver chloride, which was absorbed by nearby clay materials, including “carrier” clay or brick dust, the pottery containers, and the furnace bricks. Filled containers were placed in ovens and heated at relatively low temperatures of about 800° C for many hours, perhaps even days. ![]() The containers resembled-and may have included-ordinary Lydian cooking pots (Nos. The sheets and small grains of alluvial gold were then sandwiched between layers of salt, perhaps combined with “carriers” of clay or brick dust, inside coarse pottery containers. In preparation for the parting process, larger pieces of electrum were hammered into thin sheets to create broad surfaces for attack by a parting agent, which was probably salt (possibly also sulfides, including alum). 2 Two metallurgical techniques are directly attested by the archaeological remains: cementation, which was used to separate gold from silver and other metals present in secondary or placer gold and cupellation, which was used to recover silver in metallic form after the cementation process, and perhaps also before cementation, to remove base metals (like copper) that also occur, together with gold and silver, in secondary or placer gold.Ĭementation was conducted at sector PN in small brick ovens. Recovering gold and silver from electrum was accomplished at Sardis during the first half of the sixth century BC in simple installations located outside the city walls and close to the Pactolus Stream (Fig. (A related process to enhance the surface of alluvial gold and make its surface a deeper yellow color by removal of surface silver had long been known). Ramage and Craddock have argued that the cementation-parting process was directly related to the emergence of coinage as an accepted medium of exchange, that the need for coins of consistent purity-difficult to achieve with alluvial gold because of its wide-ranging silver content-prompted development of a process that would separate silver and gold throughout alluvial gold, i.e. ![]() Evidence for such manipulation includes electrum coins of the late-seventh and early-sixth centuries BC that contain a higher percentage of silver than is normal in secondary gold, thereby implying that the silver content had been artificially increased, and the appearance shortly before the middle of the sixth century BC (during the rule of Croesus) of coins issued separately in pure gold and pure silver. The invention of coinage in the seventh century BC and the use of electrum for the earliest coins (see Kroll, “The Coins of Sardis”) may have stimulated efforts to manipulate the natural alloy by increasing its silver content and by separating its gold and silver. ![]()
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