jay | Some passing stratigraphy...

Borehole#4 is now finished -- stopped at 165m depth. The stratigraphy ran to a few meters of volcano-sedimentary rocks (weathered tuffs), then about 20m of gossan (leached sulphites, leaving behind a vesicular iron-rich matrix), then a massive 120m unit of pyrite, containing several spots where chemolithotropic bacteria were found. Anaerobes... Then a pitch-black matrix, probably chlorite, containing cubic pyrite inclusions, clearing out to ordinary greenish chlorite at the bottom of the shaft.

I have a couple of extra specimens...

zahl wanted a rock. I could bring back a few other specimens, even geo-referenced if you're nice to me later ;-). There's also some ruddy globular haematite that I'm planning to go back for, inside the old mine...

By the way, the original British company (Rio Tinto, Ltd) in whose converted hospital this museum resides, is still very much extant. It is the world's second-largest producer of iron ore... it owns companies like Hamersley Iron (7 mines in Australia)... and a gold mine in North Parkes, NSW (near the radio telescope I visited in 1991 for SETI). Rio Tinto also owns the borax mines in the Mojave Desert (Boron, CA) back in California. Looking around, I can't say much for their environmental remediation efforts... and this is now one of the poorest areas in Spain.