Ekplexite
 | This article may be too technical for most readers to understand. (March 2016) |
| Ekplexite | |
|---|---|
| General | |
| Category | Sulfide mineral |
| Formula | (Nb,Mo)S2•(Mg1−xAlx)(OH)2+x |
| IMA symbol | Ekp[1] |
| Crystal system | Trigonal |
| Crystal class | 3m, 32 or 3m |
| Space group | P321, P3m1, P3m1 |
| Unit cell | a = 3.79, c = 11.3 [Å] (approximated) Z = 2 |
| Identification | |
| Color | Iron-black |
| Crystal habit | micaceous flakes (may be arranged in chaotic or radiating aggregates), in lenticular nests |
| Cleavage | {001}, perfect |
| Tenacity | Flexible |
| Mohs scale hardness | 1 |
| Luster | Metallic |
| Diaphaneity | Opaque |
| Density | 3.63 |
| Pleochroism | light gray to dark gray (strong) |
| Common impurities | W, V, Fe |
| References | [2][3][4] |
Ekplexite is a unique sulfide-hydroxide niobium-rich mineral with the formula (Nb,Mo)S2•(Mg1−xAlx)(OH)2+x.[5][3] It is unique because niobium is usually found in oxide or, eventually, silicate minerals. Ekplexite is a case in which chalcophile behaviour of niobium is shown, which means niobium present in a sulfide mineral. The unique combination of elements in ekplexite has to do with its name, which comes from a Greek world on "surprise".[5][3] The other example of chalcophile behaviour of niobium is edgarite, FeNb3S6, and both minerals were found in the same environment, which is a fenitic rock of Mt. Kaskasnyunchorr, Khibiny Massif, Kola Peninsula, Russia.[6] Analysis of the same rock has revealed the presence of two analogues of ekplexite, kaskasite (molybdenum-analogue) and manganokaskasite (molybdenum- and manganese-analogue). All three minerals belong to the valleriite group, and crystallize in the trigonal system with similar possible space groups.[7][3]
Notes on chemistry
[edit]Beside niobium, molybdenum, sulfur, magnesium and aluminium ekplexite contains also relatively small amounts of tungsten, vanadium and iron.[5]
Association and environment
[edit]The rock in which contains ekplexite is classified as fenite. In this rock ekplexite associates with fluorophlogopite, nepheline, orthoclase-anorthoclase (silicates), alabandine, edgarite, pyrite, molybdenite, tungstenite (sulfides), corundum, graphite and monazite-(Ce).[5]
Crystal structure
[edit]Crystal structure of ekplexite is described as non-commensurate. It is composed of two modules:[5]
- MeS2 sulfide module
- brucite-like (hydroxide) module
References
[edit]- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ↑ Pekov., I.V., Yapaskurt, V.O., Polekhovsky, Y.S., Vigasina, M.F., and Siidra, O.I., 2014. Ekplexite (Nb,Mo)S2·(Mg1−xAlx)(OH)2+x, kaskasite (Mo,Nb)S2·(Mg1−xAlx)(OH)2+x and manganokaskasite (Mo,Nb)S2·(Mn1−xAlx)(OH)2+x, three new valleriite-group mineral species from the Khibiny alkaline complex, Kola peninsula, Russia. Mineralogical Magazine 78(3), 663-679.
- 1 2 3 4 "Ekplexite: Ekplexite mineral information and data". Mindat.org. Retrieved 2016-03-04.
- ↑ "Ekplexite - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-10.
- 1 2 3 4 5 Pekov., I.V., Yapaskurt, V.O., Polekhovsky, Y.S., Vigasina, M.F., and Siidra, O.I., 2014. Ekplexite (Nb,Mo)S2·(Mg1−xAlx)(OH)2+x, kaskasite (Mo,Nb)S2·(Mg1−xAlx)(OH)2+x and manganokaskasite (Mo,Nb)S2·(Mn1−xAlx)(OH)2+x, three new valleriite-group mineral species from the Khibiny alkaline complex, Kola peninsula, Russia. Mineralogical Magazine 78(3), 663-679.
- ↑ "Edgarite: Edgarite mineral information and data". Mindat.org. Retrieved 2016-03-04.
- ↑ Pekov., I.V., Yapaskurt, V.O., Polekhovsky, Y.S., Vigasina, M.F., and Siidra, O.I., 2014. Ekplexite (Nb,Mo)S2·(Mg1−xAlx)(OH)2+x, kaskasite (Mo,Nb)S2·(Mg1−xAlx)(OH)2+x and manganokaskasite (Mo,Nb)S2·(Mn1−xAlx)(OH)2+x, three new valleriite-group mineral species from the Khibiny alkaline complex, Kola peninsula, Russia. Mineralogical Magazine 78(3), 663-679
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