He was not the farthest anyone went.

How The Geology Made The Minerals — And Why The Cave Kept Them

The minerals that drew ancient Indigenous people deep into Mammoth Cave formed through a specific geological process that has made the cave’s dry upper passages one of the most chemically complex environments in American speleology.

Gypsum — calcium sulfate — is the dominant secondary mineral in the upper passages.

It forms in several distinct ways and several distinct shapes.

In some passages it coats the walls and ceilings as crusts, white and chalky, soft enough to be scraped away with a mussel shell.