The Invisibles – emanations and extractions from Hot Rocks
Underlying the South West Peninsula is a great body, or batholith, of granite, that looms like Moby Dick from the deep. It breaks the surface here and there, bringing topographic wonder and occasionally mineral wealth in the form of copper and tin and a host of other minerals such as lead, zinc, arsenic, silver and lesser amounts of tungsten, nickel and uranium.
The presence in the granite of uranium, in the form of the minerals pitchblende, uraninite, zeunerite and coffinite has led to small-scale exploitation of uranium ores in the past. The invisible nature of ionising radiation from the ores led initially to them being overlooked, a discard thrown onto the spoil tips. The discovery of radiation in the late nineteenth century created a convoluted path from that initial ignorance and disregard to a quack-cure bonanza, to commercial extraction, and finally to a form of wilful amnesia.
Deposits and traces of these unstable radioactive minerals are found throughout the granite and their decay pathways produce two other invisible substances – radon gas and heat. The former gives rise to concerns about human health and the latter to an ongoing exploration of ‘hot rock’ geothermal energy in the region.
This field trip will start by exploring some of the sites in West Penwith where the uranium bearing ores were found, looking at the history and legacy of its exploitation.
Artist Hadrian Pigott and local rock hound Marcus Perry will lead the group across the spoil tips of Botallack on the north coast. Marcus has first hand knowledge of the distribution and accessibility of minerals in the old mine workings today, and they will be accompanied by scientists from Camborne School of Mines and the European Centre for the Environmental and Human Health who are working on the occurrence, distribution and effects of radon gas.
The story of uranium mining is also the story of tin mining, so in the afternoon this field trip will visit Rosevale Mine near Zennor. It is a classic example of a small-scale and relatively simple nineteenth-/ early twentieth-century mining operation and participants will be able to experience the working conditions and learn of the technical challenges of extracting tin from the mineral lode, and the role of metal prices in determining whether this was economically viable.
Notes: This field trip is limited to 20 participants who must be capable of descending/ascending 30+ metres of laddered sections. Outdoor clothes plus walking boots/wellies required for the mine visit. Temperatures will be cooler and it will be muddy underground.