Madranite one-five

Madranite one-five was a mineral abundant on the planet Calufrax, which, according to the Fourth Doctor, was the only place it was known to occur naturally.

The vibrations of refined madranite one-five and voolium crystals could be used to power a psychic interference transmitter, and the presence of these two minerals brought Calufrax to the attention of the crew of the pirate planet Zanak, who needed it to neutralise the psychic powers of the Mentiads. (TV: The Pirate Planet)

Behind the scenes

 * "Madranite mining belts" are mentioned in the first book of Douglas Adams' The Hitchhiker's Guide to the Galaxy series, fitting with its description as a mineral in The Pirate Planet. The Pirate Planet was Douglas Adams' first contribution to Doctor Who.