Abenakiite (Ce)

Updated on Sep 21, 2024

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Strunz classification 9.CK.10 Space group R3		Crystal system Trigonal
Category Silicate, Cyclosilicate Formula(repeating unit) Na26Ce6(SiO3)6(PO4)6(CO3)6(SO2)O Crystal class Rhombohedral (3)H-M symbol: (3)

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.

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).

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

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

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