Английская Википедия:Bijvoetite-(Y)
Шаблон:Short description Шаблон:Infobox mineral Bijvoetite-(Y) is a very rare rare-earth and uranium mineral[1][2] with the formula (Y,REE)8(UO2)16(CO3)16O8(OH)8·39H2O.[2][3] When compared to the original description, the formula of bijvoetite-(Y) was changed in the course of crystal structure redefinition.[4] Bijvoetite-(Y) is an example of natural salts containing both uranium and yttrium, the other examples being kamotoite-(Y) and sejkoraite-(Y).[5][6] Bijvoetite-(Y) comes from Shinkolobwe deposit in Republic of Congo, which is famous for rare uranium minerals. The other interesting rare-earth-bearing uranium mineral, associated with bijvoetite-(Y), is lepersonnite-(Gd).[1]
The mineral is named after the Dutch chemist and crystallographer Johannes Martin Bijvoet.
Notes on chemistry
Other rare-earth elements substituting for yttrium ("REE" in the given formula) are mainly neodymium, samarium, gadolinium, and dysprosium, with minor cerium, europium, terbium and erbium.[4] This is in slight opposition to the original reported analysis, that had dysprosium, gadolinium and terbium as main substituting REE.[2]
Occurrence and association
Bijvoetite-(Y) was found in the Shinkolobwe dolomite-hosted uranium deposit, Republic of Congo, where it occurs in an oxidation zone, together with numerous other uranium minerals: lepersonnite-(Gd), becquerelite, curite, kasolite, oursinite, rutherfordine, schoepite, sklodowskite, soddyite, studtite, torbernite, and uranophane.
Crystal structure
Although originally though to be orthorhombic, bijvoetite-(Y) was later shown to be monoclinic. The structural formula of the mineral is [M3+83+(H2O)25(UO2)16O8(OH)8(CO3)16](H2O)14, where M = (Y,REE). The structure has 16 uranium sites, with uranium belonging to near-linear uranyl groups. The important features of the structure are:[4]
- presence of uranyl pentagonal bipyramids (UPB), formed by coordination of (eight) uranyl groups by three oxide and two hydroxyl anions
- presence of uranyl hexagonal bipyramids (UHB), formed by coordination of another eight uranyl groups by six oxide anions
- presence of uranyl carbonate chain parallel to [100], of a novel type, built of edge-sharing dimers of UPB and UHB, and carbonate groups
- presence of irregular M3+Φn polyhedra (Φ - unspecified ligand) linking the uranyl carbonate chain, thus forming a compound novel-type sheet parallel to (010)
- location of 14 water molecules in the interlayer space (held by hydrogen bonding)
- bonding of the remaining 25 water molecules to trivalent cations
References
- ↑ 1,0 1,1 Deliens, M., and Piret, P., 1982. Bijvoetite et lepersonnite, carbonates hydrates d'uranyle et des terres rares de Shinkolobwe, Zaïre. Canadian Mineralogist 20, 231-238
- ↑ 2,0 2,1 2,2 Ошибка цитирования Неверный тег
<ref>; для сносокHOMне указан текст - ↑ Шаблон:Cite web
- ↑ 4,0 4,1 4,2 Li, Y., Burns, P. C., and Gault, R. A., 2000. A new rare-earth-element uranyl carbonate sheet in the structure of bijvoetite-(Y). The Canadian Mineralogist 38, 153-162.
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- Английская Википедия
- Uranium(VI) minerals
- Yttrium minerals
- Lanthanide minerals
- Carbonate minerals
- Monoclinic minerals
- Minerals in space group 4
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