Chalcopyrite out of vein...

This is massive chalcopyrite from Butte. It is lovely, isn't it? When in a rock, it makes up the "fool's gold" one hears of. However, when it's out of the rock and enters into the environment, such as flowing as gravel and sand in a river, it tarnishes and oxidizes rapidly. Panning for gold, only chalocopyrite very very very near its source site and in the river for a very very very short time still could be mistaken for gold. Sample image is about 3 cm across.