What is "batrachite"

n. A pale greenish-grey variety of montmorillonite.

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.