Petrification

Petrification was the process in which organic matter was turned into stone.

On planet Skaro, the neutronic war between the Thals and the Humanoid Daleks (or, alternatively, the Thousand Year War) presumably petrified the forest. (DW: The Daleks)

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. (DW: 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. (DW: The Stones of Blood)

Angry at how life on Earth had changed, Light turned Lady Pritchard and her daughter Gwendoline to stone. (DW: Ghost Light)

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. (DW: The Mind Robber, SJA: Eye of the Gorgon)

The disease Petrifold Regression turned its victims to stone. The Duke of Manhattan was one such victim but was cured by the Sisters of Plenitude. (DW: New Earth)