The first paper from Nicky Horsburgh’s PhD has appeared in print in the journal Physics and Chemistry of Minerals. The paper is entitled “Lanthanide and Yttrium Substitution in Natural Fluorite”, and it uses the luminescence properties of lanthanide-bearing fluorite to determine the mechanism of substitution mechanism of those elements in fluorite as a function of composition. We observe that the luminescence intensity of the luminescence from lanthanides increases linearly with composition until >1000 ppm, at which point the intensity falls. At the same time, the chondrite-normalised rare earth profiles change from being dominated by larger, light rare earths to smaller, heavy lanthanides and yttrium.
We explain the behaviour as showing that up to ~1000 ppm, rare earths substitute ideally for Ca in the fluorite structure. At that point, clustering of the lanthanides into domains occurs, reducing the size of the lanthanide site and thereby promoting small, heavy rare earths. At the same time, the energy transfer between adjacent lanthanides results in non-radiative energy loss from the lanthanides and thereby a reduction in the quantum efficiency of the luminescence.
Nicky is now a consultant engineering geologist at Geo-Rope Limited.
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The raw data from the paper will be available on open access on this link after the embargo period on Nicky’s PhD thesis expires. In the interim if anyone is interested in the data, they can discuss this with Adrian.
Professor Adrian Finch 