Euendolithic tunnels in flakes on the beach.

[iconoclastica]

This has been an awesome thread! I have a masters in geology and I didn't even question whether the pictured flakes were mica.

I was going to write the same thing before I reached your post
Decades ago I was determined to become a marine biologist and I spent all my spare time on the beach. Life took a different turn, then. But still this is exciting research (and a good story line)!