A Short Essay on Ancient Raw Metal for Iron-making and the Refining Method in the Hiroshima Prefecture

Smelting slag with a high level of manganese oxide (MnO) has been confirmed in the Kanakuro-tani site in Sera-chō, Sera-gun, Hiroshima Prefecture. It is observed that components, such as FeO-SiO2-MaO, of these slags are concentrated in a low melting zone (lower than 1300°C) when plotted on a phase diagram. MnO seems to have played the role of fluxing material to stabilize the operation of iron-making furnaces. The two mineral specimens were MnO minerals without any iron content. Therefore it is presumed that they were discarded during the concentration process as they did not have any iron content. Four iron slag specimens were investigated concerning their content. One of them had 2% MnO and in three of them, there was less than 1% MnO. Besides, all of them contained 1~3% Titania. These results indicate that both iron ore and iron sand were used as iron-making materials at the Kanakuro-tani site