# Toadstone (Lepidotes)

**Bufonites*, *borax* of the jewellers*

**Known today as.** Fossil teeth of an extinct fish, *Lepidotes*, believed to come from a toad’s head.

Kind: Mineral

## What was it used for?

An antidote: set in rings, it was thought to grow hot or change color in the presence of poison.

## What does modern science say?

No effect; a fossil.

## Pharmacognosy and toxicology

- **fossil fish teeth**: of the Jurassic ray-finned fish *Lepidotes*, the button-shaped palatal teeth
- **calcium phosphate**: 

**Mechanism.** A fossil tooth set in a ring, which neither heats nor changes colour near poison, and detects none. The identification was made by Robert Plot in 1677 and the trade continued regardless.

**Dose.** Inert.

**Standing.** A curiosity of the cabinet; the rings survive in museums.

## What did the older authorities say?

**Shakespeare.** “Sweet are the uses of adversity, / Which, like the toad, ugly and venomous, / Wears yet a precious jewel in his head.”

## Sources

- Shakespeare, *As You Like It* II.1.
- Duffin, C. J. (2008). “Fossils as drugs: pharmaceutical palaeontology.” *Ferrantia* 54.

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*Toadstone.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/toadstone

Historical description, not medical advice.