Manganese was a metal element on the periodic table.

The Fourth Doctor found a pure nugget of manganese produced by Erato. The Tythonian ambassador was sent to Chloris to exchange manganese, iron, copper, gold, platinum, cobalt, and other metals in return for chlorophyll. (PROSE: Doctor Who and the Creature from the Pit)

The Fourth Doctor detected manganese in the air at Portsmouth Harbour in 1872. He deduced it came from tiny nodules of manganese that were lodged in the damaged section of a ship's hull. (PROSE: Eye of Heaven)

Manganese and chromium were expected elements to detect in stones. (PROSE: Eternity Weeps)