Blue John

Blue John Cavern in Derbyshire takes its name from a rare form of fluorite which has within it bands which are purple -blue or yellowish and goes by the name ‘Blue John’. Blue John is a semi-precious mineral.

Blue John is also known as Derbyshire Spar is only known to occur at the Blue John Cavern and one other site in Derbyshire.

The cavern takes its name from the semi-precious mineral Blue John, which is still mined in small amounts outside the tourist season and made locally into jewellery. The deposit itself is about 250 million years old.

The Blue John Cavern was mined commercially during the 19th century to extract the Blue John mineral for ornamental purposes. Some small-scale mining is still taking place in the area.