Luminescence Studies of Feldspar Minerals and Implications for Forensic Geology

Feldspar minerals are the most common constituents of rock on this planet and, as such, are regularly encountered in sediment samples. Because these feldspar minerals are so ubiquitous, they often provide mineral identification rather than yielding a provenance determination or source-level association by traditional examination. One possible method to rapidly analyze large numbers of diverse soil samples involves measuring the luminescence of feldspar minerals among them, which could rapidly yield highly discriminating characteristics of the feldspars. In this study, a variety of 42 feldspar samples of known provenance were examined by cathodoluminescence (CL) in conjunction with ion beam induced luminescence (IBIL). Previously reported luminescent centers (Mn2+ and Fe3+) were observed and their UV-Visible peak positions vary with stoichiometric changes in the Na-K-Ca composition of the feldspars as expected. Similarly, Si-O and Al-O lattice defect luminescence in the UV-Visible spectra were observed in addition to a previously unassigned IR luminescence. Additional analysis of the feldspar samples by x-ray diffraction (XRD), electron microprobe (EMP), micro x-ray fluorescence (XRF), and particle induced x-ray emission (PIXE) was performed in an attempt to determine the mechanism for the unassigned IR peak, as well as shifting within luminescent peak signatures