| Abenakiite-(Ce) | |
| Category: | Silicate, cyclosilicate |
| Formula: | Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O |
| Imasymbol: | Abk-Ce[1] |
| Strunz: | 9.CK.10 |
| System: | Trigonal |
| Class: | Rhombohedral H-M symbol: |
| Symmetry: | R |
| Unit Cell: | a = 16.02, c = 19.76 [Å], Z = 3 |
| Color: | Pale brown |
| Colour: | , to dark brown |
| Habit: | Euhedral Crystals - Occurs as well-formed crystals showing good external form. [2] |
| Cleavage: | , poor |
| Fracture: | Conchoidal |
| Mohs: | 4–5 |
| Luster: | Vitreous |
| Streak: | White |
| Diaphaneity: | Transparent[3] |
| Gravity: | 3.32 gm/cc. |
| Density: | 3.21 |
| Opticalprop: | Uniaxial (−) |
| Refractive: | nω=1.59, nε=1.57 |
| Other: | Radioactive |
Abenakiite-(Ce) 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.[4]
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).[4]
Combination of elements in abenakiite-(Ce) is unique. Somewhat chemically similar mineral is steenstrupine-(Ce).[5] [6] 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.[4]
In the crystal structure, described as a hexagonal net, of abenakiite-(Ce) there are:[4]