madstone
nounUK /ˈmadstəʊn/
Etymology From mad + stone.
1
US A stone believed to have the power to heal the bite of a rabid or venomous animal.
- I gathered my things and asked the Negroes to return the scalps they'd stolen, along with my madstone.2013, Philipp Meyer, The Son, Simon & Schuster, published 2014, page 332: