This is a large-grained rock containing light grey-colored calcite and barite, and black franklinite crystals; a much sought after mineral assemblage from the Sterling Mine, Sterling Hill, Sussex County, New Jersey. Under short wave UV the calcite fluoresces red/orange and the barite white. The Franklinite is not fluorescent. The size of this specimen is 38.0 x 23.7 x 16.3 mm.
Mouse over the scrolling image to see UV wavelength information.