Marlion was a planet famous for its crystal mines.
Iris Wildthyme and Jenny Winterleaf once helped the Second Doctor defeat the Dalek Supreme in the crystal mines of Marlion. (PROSE: Bafflement and Devotion, Excelis Dawns)
Huxley claimed that Jo Grant encountered Daleks on Marlion during her travels with Iris Wildthyme. (AUDIO: Find and Replace)
The Diamond Mines of Marlion was a location in Reginald Tyler's The True History of Planets. (PROSE: Mad Dogs and Englishmen)
The Mines had a type of currency, in the form of diamonds. (PROSE: The Panda Book of Horror)