Uramphite, (NH (sub 4) )(UO (sub 2) )(PO (sub 4) ) . 3H (sub 2) O, from the second world occurrence, Beshtau uranium deposit, Northern Caucasus, Russia; crystal-structure refinement, infrared spectroscopy, and relation to uramarsite
Uramphite, (NH (sub 4) )(UO (sub 2) )(PO (sub 4) ) . 3H (sub 2) O, from the second world occurrence, Beshtau uranium deposit, Northern Caucasus, Russia; crystal-structure refinement, infrared spectroscopy, and relation to uramarsite
American Mineralogist (June 2024) 110 (2): 319-327
- actinides
- albite
- alkali feldspar
- arsenates
- autunite
- Caucasus
- chamosite
- chlorite group
- Commonwealth of Independent States
- coordination
- crystal structure
- crystallography
- Europe
- feldspar group
- framework silicates
- hydrates
- infrared spectra
- metal ores
- metals
- microcline
- Northern Caucasus
- occurrence
- ore minerals
- phosphates
- plagioclase
- plumbogummite
- powder method
- quartz
- Russian Federation
- sheet silicates
- silica minerals
- silicates
- single-crystal method
- space groups
- spectra
- Stavropol Russian Federation
- uranium
- uranium minerals
- uranium ores
- uranyl ion
- vanadates
- X-ray diffraction data
- liebigite
- meta-autunite
- zippeite
- threadgoldite
- schrockingerite
- uramarsite
- natrozippeite
- Beshtau Deposit
- ammoniozippeite
- uramphite
- parauranophane
Uramphite, (NH (sub 4) )(UO (sub 2) )(PO (sub 4) ) . 3H (sub 2) O, was found at Beshtau uranium deposit, Northern Caucasus, Russia, as the second world occurrence besides its type locality, Tura-Kavak uranium-coal deposit in Kyrgyzstan. In Beshtau, it occurs as yellow tabular crystals up to 0.3 mm grouped in crusts on a matrix composed of albite, microcline, quartz and chamosite in association with liebigite, meta-autunite and plumbogummite. The empirical formula calculated on the basis of 6 O apfu and 3 H (sub 2) O is [(NH (sub 4) ) (sub 0.91) K (sub 0.08) ] (sub Sigma 0.99) P (sub 0.99) U (super 6+) (sub 1.01) O (sub 6) . 3H (sub 2) O. According to single-crystal X-ray diffraction, uramphite is tetragonal, P4/nmm, with a = 6.9971(3), c = 8.9787(9) Aa, V = 439.59(6) Aa (super 3) and Z = 2. The crystal structure was refined to R (sub 1) = 3.28% for 255 unique observed reflections with F (sub o) > or = 4sigma (sub F) . A model for the distribution of H (sub 2) O and NH (sub 4) (super +) molecules in the interlayer space based on the electron density distribution data is proposed. The mineral belongs to the meta-autunite group. The IR spectrum shows the splitting of the band of H-N-H bending vibrations into four components, which is explained here by the resonance splitting of a group of NH (sub 4) (super +) cations occurring around the four-fold axis at close distances from each other. Uramphite is related to uramarsite, (NH (sub 4) )(UO (sub 2) )(AsO (sub 4) ) . 3H (sub 2) O. Both minerals are very similar, which is apparent from crystal structures and IR spectra. However, they are not isostructural. Uramarsite is triclinic, contains a significant amount of P in arsenate sites, and significantly differs from uramphite by the arrangement of H (sub 2) O and NH (sub 4) (super +) molecules in the interlayer space (planar and well organized in uramphite vs. chaotic manner in uramarsite).
