toadstone

noun

1. any of various stones or stonelike objects, formerly supposed to have been formed in the head or body of a toad, worn as jewels or amulets.

noun

1. rare an amygdaloidal basalt occurring in the limestone regions of Derbyshire

n.“stone or stone-like object, supposedly magical (with healing or protective power) and found in the heads of certain toads,” is attested from 1550s, from toad + stone (n.). Translating Greek batrakhites, Medieval Latin bufonites; cf. also French crapaudine (13c.), German krötenstein.