Centre of the Earth could hold large reservoir of iron–helium compounds(chemistryworld.com)
chemistryworld.com
Centre of the Earth could hold large reservoir of iron–helium compounds
https://www.chemistryworld.com/news/centre-of-the-earth-could-hold-large-reservoir-of-iron-helium-compounds/4021097.article
I'm off the opinion we can get a lot of energy, and possibly materials, from deep excavation.