The ball of iron would be Earth's core, and between the thin crust on which we live and the iron core there is the very thick mantle.

Nevertheless, the mantle is made of a mixture of iron oxides, silicon dioxide and magnesium oxide, with small quantities of the other elements, so under the thin crust, even if there remain thousands of kilometers until the iron ball, there is nonetheless what is essentially a huge amount of iron ore.

> ball of iron

... which is way beyond our reach.