Toadstone

The toadstone, also known as bufonite (from Latin bufo, "toad"), is a mythical stone or gem that was thought to be found in the head of a toad. It was supposed to be an antidote to poison and in this it is like batrachite, supposedly formed in the heads of frogs. Toadstones were actually the button-like fossilised teeth of Scheenstia (previously Lepidotes), an extinct genus of ray-finned fish from the Jurassic and Cretaceous periods. They appeared to be "stones that are perfect in form" and were set by European jewellers into magical rings and amulets from Medieval times until the 18th century.^[1]