"Double, double toil and trouble;

Fire burn, and cauldron bubble..."

"Macbeth" Act 4, Scene 1

For everybody who´s planning to boil a magical potion or plans a witches gathering for All Hallows' Eve, this week I will present some geological ingredients for a perfect witch's brew:

1. - The Toadstone

"Sweet are the uses of adversity,

Which, like the toad, ugly and venomous,

Wears yet a precious jewel in his head."

"As You Like It" Act 2, Scene 1

Fig.1. A Toadstone, also called Bufonite, Botrax, Borax, Batrachite, Chelonite, Brontias or even Dragonstone, as depicted in Ulisse Aldrovandi's "Musaeum Metallicum" (1648), image in public domain.

The "Lapis Bufonis"or toadstone is a rare magical gemstone found inside the head of a toad. The stone can be extracted from the toad only by putting the animal on a red cloth or by exposing the animal to heat - it will then regurgitate the stone.

Some of the ancient toadstones are today identified as the fossilized teeth of Lepidotus, an extinct fish-species from the Jurassic and Cretaceous. Maybe the black color and smooth surface of these fossils remembered early collectors of the eyes of the toads and so a new myth was born…

Fig.2. Teeth-plate of Lepidotus mantelli, from C. Lyell´s "Elements of Geology" (1838), image in public domain.