I too can think of some chalybeate wells. Recently visited one at the mouth of Glen Lyon (just near Fortingall). When I found the site at the side of the road it was chock full of fallen leaves, so I cleared them out. Without exagerating, my hands were orange for days after!! That's a serious amount of dissolved iron!

Yes- I'm very much into wells, but this isn't really the place to post pics and site notes....