toadstone

/ˈtoʊdˌstoʊn/
noun
  1. A small stone or gem once believed to be found in the head of a toad and thought to have magical or medicinal properties.
    • The old book described the toadstone as a cure for snakebites.
    • She wore a toadstone necklace, hoping it would bring her good luck.
    • In medieval times, people carried a toadstone as a charm against poison.
  2. A type of dark, fine-grained volcanic rock.
    • The quarry yielded a large deposit of toadstone used in road construction.
    • Geologists identified the black rock as toadstone from an ancient lava flow.
    • The path was paved with toadstone, giving it a rough, dark surface.