An analysis of rare earth-rich mud retrieved from ⁠the deep seabed off a remote Pacific Island earlier this year found medium and heavy rare earth elements accounted for about 54% of the total rare earth content, Japan’s government said on Friday.

But it did not disclose the size of the content or ‌the deposits, saying ‌the data was insufficient due to the limited duration and geographic scope of sampling.

The Japanese scientific drilling vessel, Chikyu, completed a monthlong mission in February near Minamitorishima island, about 1,900 kilometers southeast of Tokyo, marking the world’s first successful attempt to ⁠continuously lift rare-earth-bearing seabed mud from depths of around 6 km.