It kept the evidence of the journey.

It did not keep the purpose.

The gypsum that was scraped from these walls dissolved when it hit the humid air of Kentucky springs and summers.

The containers that carried it from the cave to the surface community did not return to the cave for preservation.

The ceremonies or trades or medical treatments for which it was used left no trace in a recoverable form.

The central question of Mammoth Cave’s prehistoric human history — why did these people repeatedly risk the dangers of deep cave travel, across three thousand years, to collect minerals that dissolve in rain? — is the question that the archive cannot answer, no matter how well preserved the archive is.