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.
The image above shows fluorescence under long wave UV (365 nm). It is simply not possible to depict the brightness of the long wave response of this fluorite specimen, as it appears much brighter in-person.
Under short wave UV (254 nm), Rogerley fluorite shows a bright blue response, but not as bright as under long wave UV.
Under visible light, the Rogerley fluorite cubes have a lovely green color. As is typical of most Rogerley specimens that feature larger-sized fluorite crystals, the cubes contain what are termed "white" or "frosted" centers. These are thought to be growth features caused by internal stress that builds as the crystals grow larger.