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Birmingham, United Kingdom
DoneMon, Oct 5, 2015 10:00 AM GMT

Blue John

Blue John is a geologically and geographically unique variety of the mineral Fluorite. It is only found in the limestone of Castleton, in the Peak District of North Derbyshire. Once extracted, Fluorite is more commonly known as Fluorspar - a term first mentioned by Georgius Agricola in 1530, amalgamating Fluor (to flow) and Spar (from the Old English spærst?n, ?spear stone?, in reference to its crystalline appearance). Mentions of a mineral matching Blue John can be found as early as 1671 in Webster?s Metallographia, discussing ?Fluores?some the colour of amethyst? and Celia Fiennes? 1679 Through England on a Side-Saddle who mentions the ?Azure Spar in Derbyshire?. Shortly after this, Charles Leigh records the ?sapphirine and azure spar? in the 1700 Natural History of Lancashire, Cheshire and The Peak District. It is mentioned as ?Blew John? by Matthew Boulton in 1768, but there is no specific mention of the name Blue John, or any variant, prior to the 1760s. The root of the name ?Blue John? is still argued, with some suggesting it derives from the French Bleu Jaune (Blue Yellow), perhaps coined by Huguenot ormolu workers collaborating with Matthew Boulton, and others suggesting it was coined by miners upon accidental discovery whilst in pursuit of another mineral colloquially known as ?Black Jack?. Neither theory has been proven?