I've had too many misadventures with dye for an extractive metallurgist.
Once during a retention time audit we found that the dye we were using was organic, so it floated right out of the first flotation cell (some smelter somewhere would have been wondering what happened).
Now I'm trying to determine the optimum crush for a heap leach and the food colouring I'm using does not stain the rocks. I was hoping to see where and how fast the solution penetrates the rocks, but the dye is not working. Does anyone have any success stories?
(We're doing regular tests, but I'd love to see how the solution penetrates the rock for a shrinking core model to compare with the usual empirical approach.)