Japanese researchers have discovered vast reserves of rare earth metals under the Pacific Ocean. At present China produces about 97 percent of the global supply of these elements, so the discovery of roughly 100 billion tonnes of rare earths which are critical for all kinds of high-tech products caused quite a lot of joy.
The reserves are much greater than China's proven reserves, but they are spread over 11 million square kilometer in a concentration of about one to two kilo per tonne. Additionally, another complication is that most of the reserves are to be found at depths between 3.5 and 6 kilometers.
According to the researchers, mining about 5 square kilometer would fulfill yearly demand, but due to the low concentration and the high depths it's unlikely to be a profitable enterprise.
What they've found is that there are vast plains of silt in various parts of the ocean where there's a decent concentration of the rare earths: 1,000 to 2,000 ppm sorts of levels, a kilo or two per tonne, 0.1 to 0.2 per cent. They surmise that the cause is iron fumes that come out of the mid-ocean vents collecting and concentrating the rare earths from the seawater before falling to that ocean floor. Some of the beds of these silts are tens of metres high (up to 50 in places), according to their estimates. Yes, there's an awful lot of rare earths there.
...However, a concentration of 1,000 to 2,000 ppm isn't actually anything all that much to write home about. That red mud which went splat over Hungary has about the same sort of concentration. As does the other 40 to 80 million tonnes a year produced, including the 2 billion tonnes lying around in ponds. We've known for decades that we can extract the rare earths from this stuff: wash it in acid and get a nice solution of the metals. However – and here's the problem – you have to use so much acid that you can't make a profit doing this.