Rock
Rock, or stone, was a naturally occurring aggregate of minerals.
Petrification was the process in which organic matter was turned into stone. The hand of Eldrad was petrified (TV: The Hand of Fear) as were Mrs Pritchard and her daughter, Gwendoline, after Light made them so. (TV: Ghost Light)
The Fourth Doctor once expressed exuberance at having landed in a location surrounded by rocks. (TV: Destiny of the Daleks)
On the planet P7E, rock was mined for processing. It eventually became an edible substance. (TV: Underworld)
On the planet Nebulax 4, rocks could be squeezed to produce a variety of bodily fluids, such as blood, mucus, saliva, phlegm or vomit, thus rendering the phrase "you can't get blood out of a stone" void. (TV: The Bounty Hunter)
On an unnamed planet, the Second Doctor, John and Gillian were able to destroy some Daleks by dropping rocks on them from a high outcrop. (COMIC: Attack of the Daleks)
