What is Blue John?

by Peter E. Blau

But: Blue John is not blue, and no one seems to have any idea who or what John was. Nor is anything known about the history of the mineral with any real certainty. Everything else you may read about Blue John must be qualified as “they say” or “perhaps” or “maybe”. It is often said by locals that Blue John was mined by the Romans, but there is no actual evidence for that earlier than a suggestion in the second edition of William Adam’s book The Gem of the Peak (1843). It’s not known with any certainty who named the mineral, or why, or when, and there is no agreement on the source of its purple color.

The prolific British geologist and speleologist Trevor D. Ford (1925-2017), credited with more than 300 articles, papers, and books, wrote two scholarly scientific papers, published in the Proceedings of the Yorkshire Geological Society in 1955 and 1969, with detailed descriptions of the mineral and the area where it is mined, and discussion of the various suggestions about its origin, and they will be helpful to anyone who wants to know more about Blue John.

The Blue John Mine and its “beautiful spar” are recommended for tourists in Baedeker’s Great Britain: Handbook for Travelers (1890). Guides were in attendance all day, the charge for admission was two shillings, and you could pay extra for Bengal lights that burned in open, hand-held wooden cups.

Conan Doyle may well have heard about, and perhaps even visited, Blue John Cavern when in 1878, not yet 19 years old, he briefly worked as an assistant to Dr. Charles Sydney Richardson in Sheffield, only 15 miles or so east of Castleton. Richardson, according to Conan Doyle in his Memories and Adventures (1924), had “a low-class practice in the poorer quarters of Sheffield,” and at the end of three weeks they “parted by mutual consent.” It’s nice to imagine that he remembered such a visit, years later, when he wrote this story.

Copyright 2022 Peter E. Blau


Peter E. Blau (“Black Peter” in The Baker Street Irregulars) discovered the world of Sherlockians in 1948, attended his first meeting of the BSI in 1958, received his Investiture in 1959, and now is a consulting geologist and free-lance journalist, and the secretary of the BSI. He first contributed to the Baker Street Journal in 1968, revived the Red Circle of Washington in 1970, won the Morley-Montgomery Award for the best article in the BSJ in 1974, and for more than fifty years has edited and published a Sherlockian and Doylean newsletter (Scuttlebutt from the Spermaceti Press).