paint-clay

Updated: May 25, 2025

These boxes have been formed in dark red sandstone, and after being emptied of their original contents, have been completely filled with colorless calcite crystals, and over this is spread an outer surface of the same crystals tinted a brilliant flame color by red paint-clay having been taken in solution by the crystal forming waters.

Luella Agnes Owen - Cave Regions of the Ozarks and Black Hills