You can't convert mass to energy like that in this context. A megaton just means a million tons (of TNT in an energy context). You can say: (the energy released when detonating) a megaton of TNT is equivalent to 46.55 g of pure mass to energy conversion (E = mc**2 type), but that would be irrelevant in this context because no one is planning converting this mass to energy, nor would it be possible.
LOL, 46 tons would hardly ever be news, that's about the output of a medium-sized mine per minute.
That’s astonishing. I clearly don’t have any type of intuition for the amount of earth these mines are extracting, because the number you’re putting out there seems comical.