Several samples of uraniferous hyalite opal on silicic vitric tuff have been analyzed for uranium distribution and concentration. X-ray fluorescence mapping has permitted identification of areas of elevated uranium concentration. Clusters of several uranyl minerals have been identified by powder and single crystal X-ray diffraction. Meta-autunite (Ca(UO2)2(PO4)2∙6-8H2O), haiweeite (Ca(UO2)2[Si5O12(OH)2]∙6H2O), uranophane (Ca(UO2)2(HSiO4)∙5H2O), and meta-uranospinite (Ca(UO2)2(AsO4)2∙8H2O) are the most prominent uranyl species located in proximity to botryoidal masses of hyalite. Silica tubes were characterized and were found to encapsulate several uranyl mineral species. Structural properties and potential short range order of amorphous silica within the hyalite opal have been investigated using powder X-ray diffraction and Raman spectroscopy. Paragenetic sequences of the uranyl minerals developed on the basis of textural analysis provide insight into the transport and fate of uranium in near-surface environmental regimes.

Distribution of uranium and uranyl minerals near and within hyalite opal

249th National Meeting (2015)

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