First of all, the analyses of rare-earth impurities in natural fluorites have been reported by several investigators [2-5].
The fluorite structure readily incorporates many impurity ions, some of which have been purported to cause color. REEs are very common impurities in fluorite, along with certain transition elements, because they are similar in terms of ionic size and charge state to calcium. Electronic transitions involving electrons from the d and f orbitals of these elements are a major cause of color in minerals including fluorite [6].