It is a natural clay pigment that is also rich in iron compounds ... Researchers Determine That Ancient Ochre Mine Is The Oldest Known Mine In The World, Last In Use About 48,000 Years Ago ...

Hopefully, you're not afraid of the dark or of heights because we're about to plunge more than 2,300 feet underground, into Minnesota's oldest iron ore mine ... to fight in World Wars I and ...

History buffs and tourists get a chance to go 2,300 feet underground to visit a historic mine in Minnesota. Underground tours resume at Minnesota's oldest iron mine ARI SHAPIRO, HOST: Hope you're ...