paul said:
I get a 404 page not found for that link.
Interesting - Brassington is definitely in Derbyshire, I used to live there! I never came across the name Potosi before though.
Yeah it doesn't like the %2520 bits. I just searched "potosi" lead mine Derbyshire
This has a map & says it was one of the "poor men's mines":
http://www.wirksworth.org.uk/A73-BRAS.htm
Seems it was also the name of field:
http://www.wirksworthromanproject.co.uk/download/i/mark_dl/u/4012767328/4635968015/TheStreet3ed.pdf
& At end of rieuwerts' book:
https://www.kriso.ee/lead-mining-derbyshire-v-3-db-9781843063452.html?lang=eng
This explains origin of such names as suggested above (also numerous other sites):
http://powerwaterproject.net/?p=556
Plus, for the Welsh version:
https://www.genuki.org.uk/big/wal/CGN/Mines