Batrachite

Batrachites were gemstones, supposedly 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 batrachian (or frog) fossil.

References

 This article incorporates text from a publication now in the public domain: 

• [1]
• "Batrachite". Oxford English Dictionary. URL accessed 2006-03-05.