Abenakiite-(Ce) Explained

Abenakiite-(Ce)
Category:	Silicate, cyclosilicate
Formula:	Na26Ce6(SiO3)6(PO4)6(CO3)6(S^4+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
Cleavage:	, poor
Fracture:	Conchoidal
Mohs:	4–5
Luster:	Vitreous
Streak:	White
Gravity:	3.21 (meas.), 3.27 (calc.)
Opticalprop:	Uniaxial (−)
Refractive:	nω=1.59, nε=1.57

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.^[2]

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).^[2]

Notes on chemistry and relation to other species

Combination of elements in abenakiite-(Ce) is unique. Somewhat chemically similar mineral is steenstrupine-(Ce).^{[3] [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.^[2]

Crystal structure

In the crystal structure, described as a hexagonal net, of abenakiite-(Ce) there are:^[2]

• 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

• List of minerals

External links

• • Mindat.org
• Webmineral.org

Notes and References

1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
2. Abenakiite-(Ce), a new silicophosphate carbonate mineral from Mont Saint-Hilaire, Quebec: Description and structure determination. McDonald, A.M.. Chao, G.Y.. Grice, J.D.. 1994. The Canadian Mineralogist. 32. 843–854.
3. Web site: mindat.org. Abenakiite-(Ce). 2024-05-25.
4. Web site: [International Mineralogical Association] : List of Minerals – IMA ]. Ima-mineralogy.org . 2016-03-12.