Andrew Carnegie wrote that one of the things that gave him an advantage over other steel manufacturers was that he hired a chemist to test ore for iron content.
By implication, this was something that had never been done before.
By implication, this was something that had never been done before.
I'm guessing they had traditional assaying techniques, just with less accuracy than a contemporary chemist.
Andrew Carnegie discovered that certain "bad" ore was that way because its iron content was much higher than usual. Secure in the knowledge that this ore was actually better than "good" ore, he developed the techniques to use it.