Fluorite from Rogerley Mine, Rogerley Quarry, County Durham, England, UK

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Lustrous gemmy green twinned crystals of fluorite measuring to 2.5 x 1.8 x 1.7 cm in size mostly standing up free from matrix with numerous smaller crystals. Minimal cleaving present, the prominent crystals are in good condition. Brightly fluorescent.Situated in the Weardale region of County Durham, England, the Rogerley Mine is a famous underground mineral deposit located within the classic North Pennine Orefield. The local geology features Carboniferous limestone and shale strata crosscut by hydrothermal vein systems where low-temperature ore-bearing fluids deposited abundant minerals within open fissures and cavity spaces. reopened by mineral collectors in the late twentieth century, the mine became world-renowned as a dedicated specimen-mining operation rather than a commercial lead mine. It is best known for producing world-class specimens of fluorite, which frequently occur as sharp, interpenetrating twin crystals displaying a striking emerald-green color. These fluorite crystals exhibit remarkably strong daylight fluorescence, dramatically shifting to an intense blue color under ultraviolet light due to trace rare earth elements within the crystal structure.