Platinum was a metallic element.
Qataka's cybernetic body had a platinum alloy skin. (PROSE: Timewyrm: Genesys)
Platinum Karlas were available in the late 21st century. (AUDIO: The Silurian Candidate)
Abel Gantz was aided by the Intra-Venus Corporation in his alchemical research in converting common metals into uranium, gold, and platinum. (COMIC: Abel's Story)
Time Lords of the Prydonian Chapter used spheres of pure platinum when playing with their perigosto sticks. (PROSE: Love and War)