Blue John stone is a rare, semiprecious mineral found at only one location in the world. It is only found in a hillside near the ancient Stone Age hill fortress of Mam Tor. Unique to Castleton, in the Derbyshire Peak District, England. The most beautiful of our truly British semiprecious stones.
One theory for the origin of the name Blue John suggests it derives from the French Bleu-Jaune meaning simply Blue-Yellow. This refers to the variation in colours from Yellow to brown then purples all the way to blue. Each piece is always different in colour and stripe and as a result each piece is unique.
Blue John is a form of Flourite discovered in ancient times as miners were exploring the cave systems of Castleton for lead. Roman lead ingots have been found stamped with the legionary mark for the local garrison legion.
Blue John is prized for ornaments and above all jewellery. It is found in many great collections housed in places such as Windsor Castle, the White House and the Vatican. The ancient romans took examples back to the Emperors in Rome. Today Blue John is popular with Derbyshire folk in jewellery as it means they always have a piece of Derbyshire wherever they travel. Blue John is also popular to wear to weddings for good luck as ‘something blue’; from the saying ‘something old, something new. Something borrowed, something blue’.
Chemically, Blue John is Calcium Flouride (CaF2) which has been coloured by films of oil deposited on the crystals millions of years ago. Although it is known as flourite, the old miners, referred to it as fluor spar.
Flourite often forms in cubic and octahedral crystals and is usually grey, Yellow or purple in colour.
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