Slowly and steadily, they continued along an underground river, the tunnel now so dark and narrow Odi began to hyperventilate again.
"Just what I need," he whined, "another bout of close-to-phobia!"
"Claustrophobia," Alice corrected him. "Seems pretty close to me!" replied Odi, for once unable to think of anything clever to say. To his great relief, they soon reached another, bigger cavern. So big, in fact, it resembled a magnificent palace, adorned with shafts of sunlight from above. As the Judith Mary approached its mooring, coming to rest on the banks of a crystal lagoon, all aboard gaped in astonishment. Not only was the cavern wonderfully bright and airy, it was like no other they had ever seen before.
"It's purple!" Joe cried. "All purple and shiny!"
"We must be in the Blue John mines." Laurel suggested.
"But it's purple!" insisted Joe.
"Blue John IS purple, Silly," Alice tutted despairingly. "Don't you boys know anything?"
"Oh, so that's why it's called blue!" said Odi with a good dollop of sarcasm. "The stuff's purple, so naturally, you call it Blue. That's cool, and not at all confusing!" – Flight from Fernilee*
|Samples of Blue John at Castleton Heritage Centre|
No wonder Odi was confused. Despite its name, Blue John – a semi-precious stone from Castleton in Derbyshire – is generously threaded by bands of purple which tend to predominate.
However, there is also a yellow banded variety of this rare fluorite and one theory is that, during the reign of Louis XVI, it was exported for use by French ormolu workers who dubbed it ‘bleu-jeune’ (or ‘blue- yellow’ to Derbyshire folk like me!) Another source for the Blue John name may be miners drafted in from Cornwall. They referred to the stone as ‘bleujenn’, a Cornish term for a flower or blossom.
According to “Gem of the Peak” by 19th century writer William Adam, Blue John was discovered by the Romans but, as no evidence has ever been found for such a claim, we might put it down to historical embroidery! What we DO know is that Blue John was a popular material for fireplace panels during the mid-18th century. A Blue John plaque dated around 1760 can be seen in the Friary Hotel in Derby, while Robert Adam, the famous architect and interior designer used it to decorate nearby Kedlestone Hall.
At their 18th century peak, the Blue John Cavern and Treak Cliff Cavern in Castleton (the only sites in the UK where Blue John is mined*) produced 20 tons per annum. By the late 19th century, 3 tons per annum was mined, a figure further reduced to a mere half a ton today. Castleton is highly protective over its unique resource which is why all items made from Blue John, such as boxes, pots, vases and distinctive jewellery, are created by local craftsmen.
*The only other place where Blue John can be found is the Deqing Fluorite mine in the Zhejiang Province of China.
*Flight from Fernilee is available from Amazon