Gemmy, green cubes of fluorite with minor non-fluorescent galena on a light brown matrix, from the source of some of the most beautiful and brightly fluorescent fluorite in the world- the Rogerley Mine, Frosterley, Weardale, North Pennines, County Durham, England. The fluorescent response of this fluorite is so bright, it can be seen under daylight; a phenomenon called daylight fluorescence, which results from the UV component of sunlight stimulating a visible fluorescent response seen as a blue color change in the green fluorite cubes. In this series of photographs, the fluorite cubes can be seen fluorescing blue under short and long wave UV, as well as under daylight in open shade. The size of this specimen is 8.1 x 5.5 x 2.5 cm.
Under short wave UV (254 nm), the Rogerley fluorite shows a bright blue fluorescent response.
Under long wave UV (365b nm), the Rogerley fluorite reacts with exceptionally bright blue fluorescence.
Under normal, incandescent lighting, the fluorite cubes show a beautiful green color.
The photograph above was taken outdoors, in open shade. Note the blue color shift in the fluorite cubes compared to the photo taken under indoor incandescent lighting above. This phenomenon is called "daylight fluorescence."