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The characterization of uranium-bearing minerals by different remote sensing technologies is a challenging task due to the implications for the exploration or the protection of uranium deposits. In nature, uranium-rich mineral ores are often associated with phosphates. Fossil bones may contain almost 1% of uranium as a result of interaction with ground water or other uranyl-bearing mineralizing fluids during fossil diagenesis. Sediments in the Lower Miocene fossil site of Córcoles (Guadalajara, Spain), in the Tajo Basin, host uranyl-vanadate metatyuyamunite associated with mammal fossils, constituting a remarkable example of the relationship between uranium ores and phosphates. The mineralogical composition and the spectral response of different phosphates (geological fluorapatite, fossil fluorapatite from Paracuellos III fossil site, and Recent hydroxyapatite) and uranyl-bearing minerals (metatorbernite, metautunite, metauranocircite and fossils from Córcoles Fm with metatyuyamunite) were studied through laboratory reflectance spectroscopy. Spectral features of the different samples were compared with XRD, XRF and FTIR-ATR to determine the relationships between reflectance spectral curves, mineralogy and chemical composition. It should be highlighted that reflectance signatures of uranyl micas and Ca-phosphates allow for the mineral identification. Fluorapatite samples show absorption bands at 586, 737, 750, 805 nm related to the phosphate anion, not always present in uranyl-phosphate micas and a characteristic chemical heterogeneity probably caused by REE content. Uranyl-bearing minerals show absorption features at 1100, 1330 and 1672 nm attributed to uranyl anions (UO2 2+). Although further research is needed this study highlights the use of laboratory reflectance spectroscopy in uranium detection.
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