Groverake Fluorspar Mine 

Groverake mine can be found in County Durham in the Pennine hills.
The mine originally operated as a lead mine in the 1800s and changed hands a number of times up until 1999 when it finally closed.
Fluorite became the primary mineral mined at Groverake from the beginning of the 20th century

The two views can be compared here below : 21st Century and 20th Century reconstruction.