Toadstones are mythical stones or gems thought to originate from the heads of toads. In reality, a toadstone is simply bufonite that formed from the button-like teeth of Lepidotes, an extinct species of fish from the Jurassic and Cretaceous periods.
In ancient times, people assumed that because toads had poison glands in their skin, they must also carry their own antidotes and took this in the form of a magic stone. For that reason, toadstone were supposed to be an antidote to a number of different poisons, and whenever someone was bitten or stung by a poisonous something-or-other, a toadstone would be rubbed on the wound. European jewellers also set the stones into magical rings and amulets until the 18th century, calling them “stones that are perfect in form.”