Natron Glass in Early Kofun Period

Natron glass, which is soda glass with very few K_2O and M_gO, is unique in Mediterranean World. Natron glass is also found in ancient Japan and they are distributed mainly in 2nd century CE (the second half of the late Yayoi period and the ending Yayoi period) and in tbe first half of 5th century CE (the first half of the middle Kofun period). Natron glass found in Japan can be divided into two groups based on the chemical compositions. The bead making techniques and the distribution periods are also different between these two groups. In this study, we investigate on natron glass in early Kofun period, which is between the two main distribution periods, and discuss the transition process of chemical compositions of natron glass in Japan and the relation with archaeological issues