Blue John Cavern

Blue John Cavern is a show cave and mining museum in Castleton, England, displaying eight different mineral veins within the limestone. Natural underground chambers connect through passages and tunnels that lead deep into the hillside.

In 1865, photographer Alfred Brothers used magnesium light to take the first underground photograph in the world here. The cavern also played a role in mining history as workers extracted the rare mineral for centuries.

The tradition of working the stone is visible on site, where craftspeople shape jewelry and ornaments from the mineral in front of visitors. The workshop shows how the material is ground and polished until its bands emerge in purple and yellow tones.

Guided tours through several chambers follow lit pathways, with former miners explaining the geological structures. Sturdy shoes with good grip are necessary because of damp and uneven surfaces.

This deposit is one of only two places in the world where the purple and yellow banded fluorite occurs naturally. The rarity of the stone makes it a sought-after collector's item among mineral enthusiasts.