On one of the lower dumps, I found this interesting and colorful rock, an iron-oxide-rich rock with colors of brown, reddish brown, and yellow brown.
The rock has some large relict pyrite cubes in the upper left, and below that and cutting through the rock are some irregular veinlets of silica, which mark spaces where former rock fragments and former sulfides have been leached and weathered out, leaving holes and soft, punky, yellow and brown Fe-oxides. The host rocks to this oxide material is - limestone!
P.S. Any ideas about the diamond-shaped hole in the upper left below the relict pyrite cubes?