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.

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.