Exploring Cornwall’s old tin mines and the Lizard serpentinites
with Barbara (July 2017).
Barbara hadn’t been to Cornwall before, so we spent a wet, blustery but enjoyable week there. The weather was uncharacteristically cold for July but we still managed to find a lot of old tin mine engine houses, and (after some searching) the old serpentine works at Poltesco Cove. Serpentinites are rocks from the Earth’s mantle, hydrated by exposure to seawater
Erik Lundin and I are interested in these rocks because they can form by exhumation of the mantle on passive margins during continental break-up. The Lizard serpentinites were obducted (thrusted up) from the mantle during the closure of the Rheic Ocean, and continental collision, some 300 million years ago. They were mined as ornamental stones, and the practice continues today, albeit in a very minor way.