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]. Under the
conditions found in most natural environments, the
majority of the REEs will exist in the trivalent
oxidation state. Thus, if they are incorporated into
fluorite it will most likely be as REE3+, necessitating a
First of all, the analyses of rare-earth impurities in naturalfluorites have been reported by several investigators [2-5].The fluorite structure readily incorporates many impurityions, some of which have been purported to causecolor. REEs are very common impurities in fluorite,along with certain transition elements, because they aresimilar in terms of ionic size and charge state tocalcium. Electronic transitions involving electrons fromthe d and f orbitals of these elements are a major causeof color in minerals including fluorite [6]. Under theconditions found in most natural environments, themajority of the REEs will exist in the trivalentoxidation state. Thus, if they are incorporated intofluorite it will most likely be as REE3+, necessitating a
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