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 (DW: The Hand of Fear) as were Mrs Pritchard and her daughter, Gwendoline, after Light made them so. (DW: Ghost Light)

On the planet P7E, rock was mined for processing. It eventually became an edible substance. (DW: 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. (K9TV: The Bounty Hunter)