Raman spectroscopic investigation of ianthinite [U24+(UO2)4O6(OH)4(H2O)4]·5H2O, a rare mixed–valence uranium oxide hydrate

Ianthinite ([U24+(UO2)4O6(OH)4(H2O)4]·5H2O) is an exotic mineral that possesses U in both tetravalent and hexavalent xidation states and is structurally related to the U3O8 polymorphs, which are commonly encountered echnogenic materials in the nuclear fuel cycle. Despite the similarities between U3O8 and ianthinite, and he importance of ianthinite in U paragenesis, no Raman spectra have been reported for this mineral. To gain a more complete understanding of how structural attributes of ianthinite give rise to observable spectroscopic features and how these may relate to important materials in the nuclear fuel cycle, we provide for the first time, Raman spectra of ianthinite. Ianthinite readily oxidizes in ambient conditions, complicating analysis of phase-pure material. Several analytical methods are employed herein to decouple the Raman features of ianthinite from its alteration product(s). First, a simple difference spectrum is presented, then results of Raman spectroscopic mapping are employed, finally, we use a novel processing and analysis method. Each analysis method provides different insight into structural features that are unique to ianthinite, in particular, features that are attributable to U(IV) in distorted octahedral coordination in both ianthinite and U3O8 phases.