Batrachite

Batrachites were gemstones, supposed to be found in frogs, to which ancient physicians and naturalists attributed the virtue of resisting poison. They resembled frogs in color.

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Toadstone is a similar mythical stone, supposed to be found in toads.

The term batrachite is also used for a fossil batrachian.

References

1. This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain. [1]
2. "Batrachite". Oxford English Dictionary. URL accessed 2006-03-05.