Paul "GeodeKid" Calburn
wrote a story about how he had to use the dynamites to pop
the caprock off the thunderegg-bearing bed and gathered the
thundereggs... or are they really the thundereggs? He called
them "transitional thundereggs". Apparently, there had
been some erosion within the cavities or septarian-like
expansion of those type of nodules. Most cavities tend to be
quite narrow and usually filled with clear agate. Few
nodules had been found with frosty banded agates. I got this
one from an old collection.