Jade magatama (ヒスイ製勾玉)
They are believed to have been made of Japanese jade at workshops in Japan. Jade magatama have been excavated from 'Bibi 4 site' and 'Wofuki site' in Hokkaido, 'Sannai-Maruyama site' and 'Kamegaoka site' in Aomori, 'Chojagahara site' in Itoigawa City, Niigata Prefecture and 'Hanareyama site' in Nagano and it is known that they were made from the middle of the Jomon period (around BC 5,000). In particular, excavations at the 'Chojagahara site' in Itoigawa have revealed a workshop for processing jade, as well as jade magatama. Fluorescent X-ray analysis shows that jade excavated from 'Sannai-Maruyama site' and southern Hokkaido came from Itoigawa, and it is therefore believed that Jomon people traded with one another over a wide area.
Magatama and diplomacy
A large amount of jade magatama have been excavated on the Korean Peninsula from areas that came under the control of Silla, Baekje and Mimana (but not from the ancient kingdom of Goguryeo) in the 5th to 6th centuries, and jade magatama were used for crowns and earrings in Silla. For this reason, scholars in prewar Japan took the jade magatama as proof of the sphere of influence of Wa (Japan), but post-war archaeologists, at one time, advocated a new interpretation that they had been introduced to Japan from Korea.
However, it turned out that with no sources in the Korean Peninsula, the only sources of gem-grade jade in Asia were Japan and Myanmar; that though none of the magatama excavated in the Korean Peninsula can be definitively traced back to the same time period as those excavated in Japan, the latest examination of their chemical composition showed that they were identical to the ones from the site surrounding Itoigawa. This shows Wa's sphere of influence, and it is believed that jadeite magatama were introduced to the Korean Peninsula from Wa.
The Chinese "History of the Later Han Dynasty" records that 'pearls and green gems are mined in Wa' and the "Gishi wajinden" (Records of the Wa people, Chronicle of Wei) records that 'Himiko (first known ruler of Japan) presented two large green magatama (considered to be made of jade) to the King of Wei.'
In addition, "Book of Sui, Vol. 81, Liezhuan (Biographies) 46" states 'Silla and Baekje respect Wa as a big power with unusual cultural products and send envoys to Wa.'