In which precious stones, usually of animal origins, are used to treat and cure a wide variety of ailments. Bezoars, stony concretions formed in the bellies of animals, were long considered antidotes against poison, and in fact were found to work against certain Arsenic based poisons. Toadstones were similar but derived from fossils (not the head of toads as erroneously believed), and Madstones would prevent rabies if stuck into the wound or bite of a mad dog.
Links on Wikipedia:
- https://en.wikipedia.org/wiki/Bezoar
- https://en.wikipedia.org/wiki/Toadstone
- https://en.wikipedia.org/wiki/Madstone_(folklore)
And one on the History of Geology: