We came down across the valley from the Seathwaite graphite mines. The workings form a vertical line up the other side of the valley. That suggests that there was a vein. But the rocks hereabouts are volcanic in origin. How did carbon get here? Turns out that it is a question that has been bothering people for years. Reading the info, it seems that the theory is that a later granitic intrusion through volcanic rock provided the heat to make organic compounds in earlier Skiddaw slates mobile. They must have coalesced in cracks in the existing rocks. The articles are very technical
https://core.ac.uk/download/files/79/57913.pdf and
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=4489624
