Aluminium

Aluminium was a metallic element. It could be found on such planets as Earth (K9TV: Dreameaters) and Megerra (BNA: Mean Streets).

The psychic energy given off by the Bodach could be blocked by Aluminium, especially in the form of hats. (K9TV: Dreameaters)

Erato wove a shell of Aluminium around a neutron star that was set to destroy Chloris, allowing the Doctor to use his TARDIS's tractor beam to pull it off course. (DW: The Creature from the Pit)