Physio-chemical study of the excavated material from the Suo-Juzenji remains, Yamaguchi Prefecture, Japan : especially the broken fragments of ancient casting coin

The Suo-Juzenji remains at Heian-Age in Japan is located at Yamaguchi city, Yamaguchi Prefecture, Western Japan, and were found many pieces of pottery as that age and minor amount of ancient coins, cupper plate, fragment of ancient casting coin and some metals. We are carried out for study on the broken fragments of casting ancient coin from the remains examined by reflective microscope, SEM and EPMA. The fragments of ancient broken coin mainly consists with As bearing copper alloy and Cu3As (domeykite), and secondarily generated compounds by reaction between Cu-rich alloy and ground water after being buried underground. Then, their surface (upper face) and back end (lower face) were cruelly different with each other. Surface side is consisting with many secondary compounds with Cu- or Pb-chloride and/or oxide, and back end is composed with some amount of copper oxide. As-bearing copper alloy with composition from 2 to 8 atomic % in Cu:Fe:As ratio and As-Cu metal with 25 to 29 atomic % (near domeykite composition) were separated by slow cooling after casting of copper smelting. Original lead metal at copper smelting changes to secondary lead compounds of such as PbO2、PbCl(OH)、Pb2O(OH)Cl Pb3CuCl2(OH)2O2 etc.

Suo-Juzennji remain

As-bearing cupper alloy

domeykite

secondary lead compounds

secondary copper oxides