Mckelveyite group minerals – Part 5: Bainbridgeite-(NdCe), Na 2 Ba 2 NdCe(CO 3 ) 6 ●3H 2 O, a new neodymium and cerium-dominant species from Mont Saint-Hilaire, Canada
Year: 2026
Type: article
Abstract: The new mckelveyite group mineral bainbridgeite-(NdCe), ideally Na 2 Ba 2 NdCe(CO 3 ) 6 ⚫3H 2 O, was found at Mont Saint-Hilaire, Quebec, Canada. It occurs in two distinct environments: (1) in a “carbonate pegmatite” as pale-yellow or orange barrel-shaped short prismatic crystals up to 2 mm in size, where bainbridgeite-(NdCe) forms thin rims while the core is composed of bainbridgeite-(YCe), and (2) in a hornfels rock as white or pale-grey tabular saucer-shaped crystals up to 0.5 mm in size. It has a white streak, a vitreous lustre, and no cleavage. D calc is 3.49 g cm −3 . Bainbridgeite-(NdCe) is optically biaxial (+), α =1.577(3), β =1.592(3), γ =1.657(3), 2V (meas.) = 40(3)°, and 2V (calc.) = 52° (589 nm). The IR spectrum is reported. The composition (wt. %, average of seven analyses) is Na 2 O 6.85, CaO 1.16, SrO 4.83, BaO 24.02, Y 2 O 3 1.84, La 2 O 3 6.07, Ce 2 O 3 8.82, Pr 2 O 3 0.76, Nd 2 O 3 6.24, Sm 2 O 3 3.34, Eu 2 O 3 0.46, Gd 2 O 3 2.74, Tb 2 O 3 0.21, Dy 2 O 3 0.53, ThO 2 0.24, CO 2 27.33, H 2 O 5.73, total 101.17. The empirical formula of the holotype from the “carbonate pegmatite” calculated on the basis of six cations is as follows: Na 2.09 Ca 0.19 Sr 0.44 Ba 1.48 Y 0.15 La 0.35 Ce 0.51 Pr 0.04 Nd 0.35 Sm 0.18 Eu 0.03 Gd 0.14 Tb 0.01 Dy 0.03 Th 0.01 (CO 3 ) 5.86 (H 2 O) 3.00 . The mineral is triclinic, P 1, a =9.0525(3) Å, b =9.1178(2) Å, c =6.85180(19) Å, α =102.575(3)°, β =116.272(4)°, γ =59.788(4)° and V =438.23(3) Å 3 , and Z =1. The strongest reflections of the powder X-ray diffraction pattern [ d , Å( I )(hkl)] are as follows: 6.17(50)(001, 1‾1‾1, 1‾01), 4.407(100)(11‾0, 2‾1‾1, 120), 4.077(30)(1‾2‾1, 1‾11, 210), 3.241(32)(11‾1, 2‾1‾2, 121), 2.870(88)(1‾2‾2, 1‾12, 211), 2.621(39)(3‾01, 030, 3‾3‾1), 2.253(22)(2‾21, 2‾4‾1, 4‾2‾1), and 1.9978(25)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data ( R 1 =0.036), is of the weloganite type. Bainbridgeite-(NdCe) is the first known mineral with Ce and Nd atoms preferentially concentrated at two different sites of the structure.
Source: European Journal of Mineralogy
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,024
Funder: Canadian Museum of Nature
OpenAlex ID: W7168579449