About 9 years ago I found this rock in the middle of the river. It reminds me of a some kind of a volcanic rock, but I live in Finland, and we only have dead volcanoes around here. Outer layer is just a normal looking rock with tiny little craters, and in the inside it reminds me little bit like obsidian, but with lighter color. It's hard and maybe as dense as a normal rock of that size. Also it doesn't appear to be magnetic.