I have a beaker containing some used ferric chloride etchant that set out over the weekend and began growing some very strange stones that I can't identify. I've never seen etchant do this before; typically it dries down to those goopy black cyrstals IME. I did some googling and looked at the chemistry involved, but haven't been able to identify what these things likely are.
If anyone has any ideas or input, I'm all ears!
