The Kamioka mines: from silver to supernovas

Part of the Kamioka zinc mining and smelter complex

Just after posting about the Kamioka Railway another photo from that 2006 set piqued my interest. Up there in the mountains the landscape looked blasted not just by winter but by something more. It was the kind of lonely place where you would not expect to find major industry, so this sight was quite surprising. Even more surprising is the history associated with this photo.

According to some sources mining and refining of ores in Kamioka dates back to 710 AD and only closed in 2001. Undoubtedly the mine was a major reason for the existence of the Kamioka Railway. Refining of zinc still continues to this day under the parent Mitsui Kenzoku zaibatsu.

Gold, silver, copper, zinc and lead were all dug out of the rock here. Unfortunately, the process released cadmium into the river, which, when taken up by the rice that was grown in the river, caused the terrible itai-itai disease – meaning “It hurts! It hurts”. Cadmium poisoning has a number of terrible effects on the body, including the softening of bones and kidney damage. The corporation and government were forced to engage in a large clean up operation which primarily involved preventing the escape of further cadmium contamination at the source.

But the history of the mine doesn’t end there. Hidden away a kilometre underground in the mine is a huge tank of ultra-pure water and extremely sensitive photodetectors. Called the Super Kamionkande Experiment, its purpose is to detect subatomic particles called neutrinos. These particles only interact very weakly with matter, but when one does collide at very high speed with an atomic nucleus or electron in the water it can accelerate it to beyond the speed of light in water and produce a detectable flash of Cerenkov radiation.

Super Kamionkande has detected neutrinos generated by fusion within the Sun and by the supernova 1987a.

So this is a story of curiosity, discovery, wealth, suffering and enlightenment.