I was told that
I'm one of very few people ever to own a Tufa bed thunderegg
which came from a 200 pound box of Oregon thunderegg roughs.
The thundereggs apparently contain well banded agates,
sometimes with amethyst centers.
YOU CAN CLICK ON THE PICTURES TO
SEE LARGER PICTURES

Rough Appearance: Gray with small "rock bubbles" all over,
shells tend to
crumble easily
The chances of having one is quite remote.