Yttrofluorite is defined as fluorite (CaF2), where the rare earth element yttrium replaces some of the calcium atoms, and therefore has the molecular formula (Ca,Y)F2. Regardless of the science, yttrofluorite is a subtle, and truly stunning fluorescent mineral glowing in all wavelengths. The piece below is about 2 inches by an inch and a half, is shown in LW, SW, MW and natural, and is from Hundholmen, Tysfjord, Norway.