A blue or purple banded variety of fluorite found in Derbyshire.
More example sentences
- Many of our Blue John items can also be made in other stones like Jade, Turquoise or Mother of Pearl.
- It is likely that they were searching for deposits of lead ore and struck upon an outcrop of Blue John by chance.
- The name Blue John very likely was made up by John Kirk and Joseph Hall who worked the mines in the 18th Century.