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)

Weeping Angels, when observed, literally turned to stone, as a defense system, using a mechanism known as quantum-locking. (TV: Blink)