Calcite, Fluorite, & pyrite Stone from Morocco. Very unique & fluorescent. You must have a UV LW 395BM light to see the fluorescence. First 2 pictures taken with UV LW 395NM Light. Fluorescent rocks & minerals are illuminated with ultraviolet light. They glow with an amazing array of vibrant colors - in sharp contrast to the color of the rocks under conditions of normal illumination. These minerals have the ability to temporarily absorb a small amount of light and an instant later release a small amount of light of a different wavelength. This light emission is known as "fluorescence." This change in wavelength causes a temporary color change of the mineral in the eye of a human observer. The color change of fluorescent minerals is most spectacular when they are illuminated in darkness by ultraviolet light.