Chemistry:Abenakiite-(Ce)

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Short description: Cyclosilicate mineral
Abenakiite-(Ce)
أبيناكييت.jpg
General
CategorySilicate, cyclosilicate
Formula
(repeating unit)
Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O
Strunz classification9.CK.10
Crystal systemTrigonal
Crystal classRhombohedral (3)
H-M symbol: (3)
Space groupR3
Unit cella = 16.02, c = 19.76 [Å], Z = 3
Identification
ColorPale brown
Cleavage{0001}, poor
FractureConchoidal
Mohs scale hardness4–5
|re|er}}Vitreous
StreakWhite
Specific gravity3.21 (meas.), 3.27 (calc.)
Optical propertiesUniaxial (-)
Refractive indexnω=1.59, nε=1.57
References[1][2]

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.[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][4] 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

See also

References

  1. 1.0 1.1 1.2 1.3 1.4 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
  2. 2.0 2.1 2.2 Mindat, Abenakiite-(Ce), Mindat.org
  3. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode2021MinM...85..291W. 
  4. "[International Mineralogical Association : List of Minerals – IMA"]. http://www.ima-mineralogy.org/Minlist.htm. Retrieved 2016-03-12. 

External links