- © The Mineralogical Society Of America
Apatite group minerals are among the most interesting of luminescent minerals due to their wonderful combinations of varying emission color, complex zoning, and intriguing associations. Several of the most famous mineral localities known for spectacularly fluorescent mineral associations involve apatite group minerals, calcite and ore minerals. For example, Långban, Sweden, with svabite, hedyphane and mimetite; and Franklin, New Jersey, USA, with fluorapatite, svabite and turneaurite (see e.g., Bostwick 1977, Robbins 1994). Apatite is also an extremely common mineral, formed under a wide range of conditions and in many types of host rock. The diversity of its luminescence is created in part by (1) the ability of the apatite structure to incorporate transition metal, REE and anion impurity activators and co-activators, often in combination; (2) the varying types of associations and formation conditions that promote luminescence activity; and (3) the nature of the structure of the apatite host itself. This favorable and flexible host structure has not been lost to commercial enterprises, as apatites have long been used as synthetic phosphors in industrial and consumer products, and more recently as laser matrix materials. Because the luminescence is often associated with rare earth elements (REE), apatite is frequently useful as a REE-indicator mineral. Indeed, apatite can act as a reservoir for REE, making fractionation and isotopic analyses feasible. Analysis of the REE content can also serve as an indicator of growth rate, growth conditions, local chemical mixing and redox conditions. As apatite is readily stimulated to luminescence by an electron beam, cathodoluminescence is frequently reported and contributes to trace contaminant REE analysis, and characterization of chemical zoning.
The thermo-luminescence of apatite has also been studied with an aim to extract details of the defect electronic structure. As bone and teeth materials have hydroxyl-apatite as their main mineral component, it would seem …