Blue John
Preserved but no longer current.
A blue fluor-spar, found in the Blue John mine near Castleton, Derbyshire; so called to distinguish it from the Black Jack, an ore of zinc. Called John from John Kirk, a miner, who first noticed it.
Era: ca. 1898 (Victorian)
Sources & notes
Reproduced from Brewer’s Dictionary of Phrase and Fable (1898 edition, public domain; archive.org, retrieved 2026-07-31; OCR text, minor errors possible). Reflects the scholarship and attitudes of its era.
Common questions
What does “Blue John” mean?
A blue fluor-spar, found in the Blue John mine near Castleton, Derbyshire; so called to distinguish it from the Black Jack, an ore of zinc. Called John from John Kirk, a miner, who first noticed it.
Is “Blue John” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.