Sand was a fine substance composed of rock and mineral. Sand could be made into glass, and would eventually do so if left alone for long enough. (TV: The Keys of Marinus, The Caves of Androzani)

Having passed through a wormhole to the planet, the Tenth Doctor explained that the "sand" on San Helios was in fact the waste left by the Swarm after they laid waste to everything on the surface. The Doctor tasted this "sand" and was able to judge its composition by doing so. (TV: Planet of the Dead)

The sand on Unity was blue. (AUDIO: Shadow Planet)

Under the reign of the Golden Emperor, the metallic sands of the desert surrounding the Dalek City were magnetised, allowing the Daleks to pull the sand over their city within minutes, hiding it beneath an immense dune. (COMIC: Power Play)

The terrain of the anti-matter universe was composed primarily of sand, causing Alistair Gordon Lethbridge-Stewart to briefly believe that UNIT HQ had been deposited on a beach in Cromer. (TV: The Three Doctors)