Abenakiite-(Ce)
| Abenakiite-(Ce) | |
|---|---|
| General | |
| Category | Silicate, Cyclosilicate |
| Formula (repeating unit) | Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O |
| Strunz classification | 9.CK.10 |
| Crystal system | Trigonal |
| Crystal class |
Rhombohedral (3) H-M symbol: (3) |
| Space group | R3 |
| Unit cell | a = 16.02, c = 19.76 [Å] (approximated); Z = 3 |
| Identification | |
| Color | Pale brown |
| Cleavage | {0001}, poor |
| Fracture | Conchoidal |
| Mohs scale hardness | 4-5 |
| Luster | Vitreous |
| Streak | White |
| Density | 3.21 (meas.), 3.27 (calc.) (approximated) |
| Optical properties | Uniaxial (-) |
| Refractive index | nω=1.59, nε=1.57 (approximated) |
| References | [1][2] |
Abenakiite-(Ce) (IMA1991-054) is a mineral of sodium, cerium, neodymium, lanthanum, praseodymium, thorium, samarium, oxygen, sulfur, carbon, phosphorus, and silicon with a chemical formula Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O. The silicate groups may be given as the cyclic Si6O18 grouping. The mineral is named after the Abenaki, an Algonquian Indian tribe of New England. Its Mohs scale rating is 4 to 5.[1]
Occurrence and association
Abenakiite-(Ce) was discovered in a sodalite syenite xenolith at Mont Saint-Hilaire, Québec, Canada, together with aegirine, eudialyte, manganoneptunite, polylithionite, serandite, and steenstrupine-(Ce).[1][2]
Notes on chemistry and relation to other species
Combination of elements in abenakiite-(Ce) is unique. Somewhat chemically similar mineral is steenstrupine-(Ce).[2][3] The hyper-sodium abenakiite-(Ce) is also unique in supposed presence of sulfur dioxide ligand. With a single grain (originally) found, abenakiite-(Ce) is extremely rare.[1]
Crystal structure
In the crystal structure, described as a hexagonal net, of abenakiite-(Ce) there are:[1]
- chains of NaO7 polyhedra, connected with PO4 groups
- columns with six-membered rings of NaO7, and NaO7-REEO6, and SiO4 polyhedra (REE - rare earth elements)
- CO3 groups, NaO6 octahedra, and disordered SO2 ligands within the columns
References
- 1 2 3 4 5 McDonald, A.M., Chao, G.Y., and Grice, J.D., 1994. Abenakiite-(Ce), a new silicophosphate carbonate mineral from Mont Saint-Hilaire, Quebec: Description and structure determination. The Canadian Mineralogist 32, 843-854
- 1 2 3 Mindat, Abenakiite-(Ce), Mindat.org
- ↑ "[International Mineralogical Association] : List of Minerals - IMA". Ima-mineralogy.org. Retrieved 2016-03-12.