Archaeochemical study of glass beads excavated from the sites in Hokkaido at Ainu culture period by using a portable XRF spectrometer

Since the chemical composition of glass reflects raw materials and production site we have studied, the origin of the glass by using X-ray fluorescence analysis focusing on ancient and medieval glass beads. In Honshu of the Middle Ages, the circulation of glass had declined, but in Hokkaido of the same period a unique culture called the Ainu Culture Period was emerging, and the circulation of glass was thriving. We focused on glass beads excavated from sites in Hokkaido during Ainu culture period. The analytical results showed that these glass beads can be classified into two types-lead potash silicate glass (K₂O-PbO-SiO₂) and potash lime silicate glass (K₂O-CaO-SiO₂). Analysis of the earliest glass of the Ainu culture period also revealed that the glass type that circulated changes significantly when it comes to the Ainu culture period. In addition, we analyzed the glass beads of Hokkaido throughout, suggesting that there is a high possibility that potassium lime glass was probably made in China in terms of chemical composition, and we were able to clarify the compositional type of glass beads circulated in Hokkaido during the Ainu culture period. (author)