We describe important variations in the crystal chemistry of fluorapatite from the manganiferous deposit at the St. Marcel – Praborna mine in the Val d’Aosta, Italy. Three types of fluorapatite were observed. Their cathodoluminescence, coupled with in situ electron-microprobe analyses, reveal a direct relationship between the intensity of cathodoluminescence and the concentration of Mn 2+ and As 5+ . The progressive replacement of P by As and of Ca by Sr, linked to the fracturing of the minerals and circulation of fluid, has been observed in the latest-stage apatite. Arsenic efficiently quenches the luminescence due to the incorporation of trace amounts of the rare-earth elements, and only partially quenches emission due to high concentrations of Mn 2+ . A drastic increase in As, up to 10 wt% As 2 O 5 , quenches all luminescence.
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Perseil et al. (2000) studied this question.
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