X-Ray micro-Computed Tomography and micro X-ray Fluorescence mapping of synthetic emerald by using a laboratory polycapillary optics X-ray tube layout

This paper relates the X-ray micro-Computed Tomography and micro X-ray Fluorescence 2D mapping of a synthetic emerald performed by a conventional X-ray source matched with polycapillary optics. The investigated crystals were synthesized in 1888 by Hautefeuille and Perrey starting from a stochiometric oxide mixture and using LiMoO4 as a flux; Cr was added to the system to give the green-color to the resulting crystals. Preliminary scanning electron microscope-backscattered electron images, coupled with wavelength-dispersive spectrometry microanalyses, showed a peculiar ‘hourglass’ distribution of Cr across the beryl crystals. In this contribution, we show the capability of a laboratory polycapillary lenses/X-ray tubes layout to characterize at the micrometric scale; the 3D spatial distribution of Cr in these emerald crystals. Actually, this technique offers many opportunities to characterize natural and technological materials where zoning of particular chemical elements occur at the micron or sub-micron scale.