Japanese researchers have discovered a trove of rare earths — valuable materials that are essential to the production of high-tech products — in the nation's exclusive economic zone. The deposits could yield several hundred years of supplies if mining techniques can be developed to make their extraction economically viable. If that problem can be solved, then the international market for rare earths could be transformed, and that would have profound implications for Japan's relations with China, if not China's relationship with much of the high-tech manufacturing supply chain.

Rare earths are a group of 17 metals that are highly prized for their use in products such as smartphones, batteries, displays and even wind turbines. They have tongue-twisting names like dysprosium, praseodymium, ytterbium and yttrium. In fact, "rare earths" is a bit of a misnomer: They are not hard to find — only promethium is actually scarce — but the deposits tend to be dispersed rather than concentrated in single areas, and when they are found they are often intermingled and can be difficult to separate.

Mining rare earths can be expensive because of the dispersion, location and the environmental consequences of recovery. It is a dirty process and the ensuring pollution, which can do extensive damage to wildlife, human life and the environment, has deterred many countries from exploiting their rare earths deposits. This is one of the reasons that China has become the world's main supplier: About 90 percent of the world's supply of rare earths — the proportion reaches as high as 97 percent for some metals — is now produced there.