(Update) One note: many local papers falsely claimed that "China mines all 17 types of rare earths", or even "China is the only country that mines all 17 types". This is WRONG. To start with, there are only 16 elements to be mined, the Promethium is radioactive and decays quickly (the most stable isotope of Promethium lose half of its atoms every 17.7 years). So, nobody, including China, mines Promethium.
Watch Lisa Reisman on the alleged RRE "ban".
In fact, even from the mother of all rumours, this NYT report, this was not really a ban,
- Industry officials said that mainland China’s customs agency had notified companies that they were not allowed to ship to Japan any rare earth oxides, rare earth salts or pure rare earth metals, although the shipments are still allowed to go to Hong Kong, Singapore and other destinations. But no ban has been imposed on the export to Japan of semi-processed alloys that combine rare earths with other materials, the officials said. China has been trying to expand its alloy industry to create higher-paying jobs in mining areas, instead of exporting raw materials for initial processing.
Having reviewed this, it makes one wonders, if not for the rare earths, what made Japan released the captain in such an abrupt change of stance? IMO, as I wrote in Chinese a couple days earlier, there are two plausible explanations. (1) that the local prosecutor did reached this decision on his own, based on the circumstantial evidence; (2) that what Kan perceived was the determination of the PRC government in even risking a lose-lose fight in this issue, as it directly challenged its legitimacy domestically.