Green cubes of fluorite on a light brown matrix, from the Rogerley Mine, Weardale, County Durham, England. Discovered in the early 1970’s, the Rogerley Mine is the source of some of the most beautiful and brightly fluorescent fluorite in the world. This is the only mine in the UK that is currently worked on a commercial basis strictly for the production of mineral specimens. Under short wave UV, this fluorite shows a beautiful blue fluorescent response, but is at its best when viewed under long wave UV, where it fluoresces a bright, light blue. The size of this specimen is 7.8 x 7.5 x 5.1 cm, and it weighs 301 grams.