About
Note: Do not rely on this information. It is very old.
Bluejohn
Blue-john, a common name for Fluor Spar (CaF2), which is found to a large extent in Derbyshire. Used for ornamental purposes.
Blue-john, a common name for Fluor Spar (CaF2), which is found to a large extent in Derbyshire. Used for ornamental purposes.