Does slag ever have wildly different isotope ratios like that in practice? I would guess they're pretty well mixed in the ore, without much of the kind of local

Does slag ever have wildly different isotope ratios like that in practice? I would guess they're pretty well mixed in the ore, without much of the kind of local variation that would throw the ratio out of whack for just one tiny sample. Unless the refining process can accidentally separate magnesium by isotopes, you need a much more involved hoax.