They may have a newly discovered mineral (not common, but it does still happen).
The arsenic rich water indicates a likely high temperature hydrothermal influence, not unexpected considering the location of the lake. I wonder if anyone is prospecting for gold in the area, too, as those temperature regimes are getting pretty close. I'd be looking for quartz veins...
Being a volcanic area, all kinds of interesting things could be belched forth from the magma.
Dilithium?