Petrification was the process by which organic matter was turned into stone.
The hand of Eldrad was petrified but still wore a ring that allowed the minds of others to be controlled. When the hand was placed in the nuclear reactor at the Nunton Experimental Complex, Eldrad gained a whole new body. (TV: The Hand of Fear)
Cessair of Diplos had stolen the Great Seal of Diplos for which the penalty was perpetual imprisonment. The Megara turned her into a stone and she became the tenth stone in the Nine Travellers stone circle. (TV: The Stones of Blood)
The Gorgons (and thus the better known of them, Medusa) were noted for having the power to turn anyone who looked at them to stone. One of the Gorgons' victims, while undergoing the slow process, could not move but could still cry. (TV: The Mind Robber, Eye of the Gorgon)