Ekplexite
From Wikipedia, the free encyclopedia
| 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]
