Zeiton-7

Zeiton-7, also spelt zyton seven, (PROSE: Lucifer Rising) was a rare Zeiton mineral and fuel which was used by TARDISes. It was used to generate orbital energy, which allowed the ship to move. It could be also used for fuel by other space-time vessels. It was generally found on Varos, though Galatron Mining Corporation had also found traces of Zeiton-7 on asteroid Biosculptor. (TV: Vengeance on Varos) It was also found on the Archon homeworld. (PROSE: The Nameless City)

The Eighth Doctor once suggested that it could be synthesised, perhaps using compressed nitrogen as a base but the exact formula eluded him. Zeiton-7 did not exist in the Divergent Universe. (AUDIO: The Creed of the Kromon)

Zeiton-7 could also be used to form part of a cold fusion generator. (PROSE: Lucifer Rising)

Zeiton-7 crystals were used to power tachyon-drive units. (COMIC: Buying Time)

On an alternative Gallifrey, there was a Zeiton-7 field on which the slaves settled after their liberation. The Mining Guild wished to mine there and President Romana (from N-Space) decided that the Guild and the slaves would each get 50% of the profits made from the Zeiton-7. (AUDIO: Evolution)

Once, when the Second Doctor and Jamie were travelling, the Time Rotor was damaged and the TARDIS was stranded in London 1968. According to the Doctor, the TARDIS needed "the equivalent of a blood transfusion: gold, mercury and Zeiton-7". When the Doctor touched the Necronomicon, given to Jamie by Professor Thascalos, the TARDIS took off and landed on the Archon homeworld. There, the Doctor and Jamie travelled to the Nameless City, which was built "over a pool of gold, surrounded by canals of mercury and Zeiton-7". (PROSE: The Nameless City)