Veblenite, K2□2Na(Fe2+5Fe3+4Mn2+7□)Nb 3Ti(Si2O7)2(Si8O22)2O6(OH)10(H2O) 3, a new mineral from Seal Lake, Newfoundland and Labrador : mineral description, crystal structure, and a new veblenite Si8O2 ribbon

• Published in: Mineralogical Magazine
• Main Authors: F. Cámara, E. Sokolova, F. C. Hawthorne, R. Rowe, J. D. Grice, K. T. Tait
• Other Authors: F.C. Hawthorne, J.D. Grice, K.T. Tait
• Format: Article in Journal/Newspaper
• Language: English
• Published: Mineralogical Society of Great Britain 2013
• Subjects: Canada; Crystal structure; Electron-microprobe analysi; Jinshanjiangite; Nafertisite; New mineral; Newfoundland and Labrador; Niobophyllite; Seal Lake; Veblenite; Veblenite ribbon; Settore GEO/06 - Mineralogia; Newfoundland; Ten Mile
• Online Access: http://hdl.handle.net/2434/477119; https://doi.org/10.1180/minmag.2013.077.7.06

Veblenite, ideally K2□2Na(Fe2+5Fe3+4Mn2+7□)Nb 3Ti(Si2O7)2(Si8O22) 2O6(OH)10(H2O)3, is a new mineral with no natural or synthetic analogues. The mineral occurs at Ten Mile Lake, Seal Lake area, Newfoundland and Labrador (Canada), in a band of paragneiss consisting chiefly of albite and arfvedsonite. Veblenite occurs as red brown single laths and fibres included in feldspar. Associated minerals are niobophyllite, albite, arfvedsonite, aegirine-augite, barylite, eudidymite, neptunite, Mnrich pectolite, pyrochlore, sphalerite and galena. Veblenite has perfect cleavage on 001 and splintery fracture. Its calculated density is 3.046 g cm-3. Veblenite is biaxial negative with α 1.676(2), β 1.688(2), γ 1.692(2) (λ 590 nm), 2Vmeas = 65(1)°, 2Vcalc = 59.6°, with no discernible dispersion. It is pleochroic in the following pattern: X = black, Y = black, Z = orange-brown. The mineral is red-brown with a vitreous, translucent lustre and very pale brown streak. It does not fluoresce under short and long-wave UV-light. Veblenite is triclicnic, space group P1̄, a 5.3761(3), b 27.5062(11), c 18.6972(9)Å, α 140.301(3), β 93.033(3), γ 95.664(3)°, V = 1720.96(14)Å3. The strongest lines in the X-ray powder diffraction pattern [d(Å)(I)(hkl)] are: 16.894(100)(010), 18.204(23)(01̄1), 4.271(9)(14̄1, 040, 120), 11.661(8)(001), 2.721(3)(19̄5), 4.404(3)(1̄3̄2, 14̄2), 4.056(3)(031, 11̄2; 15̄2, 1̄4̄3), 3.891(2)(003). The chemical composition of veblenite from a combination of electron microprobe analysis and structural determination for H2O and the Fe2+/Fe3+ratio is Nb2O5 11.69, TiO2 2.26, SiO2 35.71, Al2O3 0.60, Fe2O3 10.40, FeO 11.58, MnO 12.84, ZnO 0.36, MgO 0.08, BaO 1.31, SrO 0.09, CaO 1.49, Cs2O 0.30, K2O 1.78, Na2O 0.68, H2O 4.39, F 0.22, O = F -0.09, sum 95.69 wt.%. The empirical formula [based on 20 (Al+Si) p.f.u. is (K0.53Ba0.28Sr0.03□0.16) Σ1(K0.72Cs0.07□1.21) Σ2(Na0.72Ca0.17□1.11) Σ2(Fe2+5.32Fe3+4.13Mn2+5.97Ca0.70Zn 0.15Mg0.07□0.66) Σ17(Nb2.90Ti0.93Fe3+0.17) Σ4(Si19.61Al0.39)S20O 77.01H16.08F0.38. The simplified formula is ...