In the mine, you could see cross-sections of the limestone. How the minerals and water crystalised and formed calcite.

But what was this phosphate they were digging out? The phosphate in this particular mine was formed from decomposed bat guano. That’s right, it’s very, very old bat poo from the Pleistocene (around 1 million years ago). You can see it here as the white bits.

And here seaping into the rock crevices.