• journal_title：Mineralogical Magazine
• Contributor：E. Sokolova ; F. Cámara ; F. C. Hawthorne
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2011-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2011.075.4.2495
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：75
• issue：4
• firstpage：2495
• section：Research Articles

The crystal structures of two polytypes of innelite, ideally Ba₄Ti₂Na₂M²⁺Ti(Si₂O₇)₂[(SO₄)(PO₄)]O₂[O(OH)] where M²⁺ = Mn, Fe²⁺, Mg, Ca: innelite-1<em>Tem>, <em>aem> 5.4234(9), <em>bem> 7.131(1), <em>cem> 14.785(3) Å, α 98.442(4), β 94.579(3), γ 90.009(4)°, <em>Vem> 563.7(3) ų, space group <em>Pem>e-formula" id="inline-formula-1">ex" alt="Formula" src="2495/embed/tex-math-1.gif" />, <em>Dem>_calc. = 4.028 g/cm³, <em>Zem> = 1; and innelite-2<em>Mem>, <em>aem> 5.4206(8), <em>bem> 7.125(1), <em>cem> 29.314(4) Å, β 94.698(3)°, <em>Vem> 1128.3(2) ų, space group <em>Pem>2/<em>cem>, <em>Dem>_calc. = 4.024 g/cm³, <em>Zem> = 2, from the Inagli massif, Yakutia, Russia, have been refined to <em>Rem> values of 8.99 and 7.60%, respectively. Electron-microprobe analysis gave the empirical formula for innelite as (Ba_3.94Sr_0.06)_Σ4.00(Na_2.16e-formula" id="inline-formula-2">ex" alt="Formula" src="2495/embed/tex-math-2.gif" />e-formula" id="inline-formula-3">ex" alt="Formula" src="2495/embed/tex-math-3.gif" />Mg_0.15Ca_0.10□_0.04)_Σ3(Ti_2.97Nb_0.02Al_0.02)_Σ3.01Si_4.01(S_1.02P_0.81□_0.17)_Σ2H_1.84O_25.79F_0.21 which is equivalent to (Ba_3.94Sr_0.06)_Σ4.00(Ti_1.97Nb_0.02Al_0.02)_Σ2.01(Na_2.16e-formula" id="inline-formula-4">ex" alt="Formula" src="2495/embed/tex-math-4.gif" />e-formula" id="inline-formula-5">ex" alt="Formula" src="2495/embed/tex-math-5.gif" />Mg_0.15Ca_0.10□_0.04)_Σ3Ti(Si_4.01O₁₄)[(SO₄)_1.02(PO₄)_0.81(OH)_0.51H₂O_0.17]O₂[(OH_0.99F_0.21)_Σ1.20O_0.80], calculated on the basis of 26 (O + F) anions, with H₂O calculated from structure refinement. The crystal structure of innelite is a combination of a TS (titanium silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral) and exhibits linkage and stereochemistry typical for Ti-disilicate minerals of Group III (Ti = 3 a.p.f.u.): two H sheets connect to the O sheet such that two (Si₂O₇) groups link to the <em>transem> edges of a Ti octahedron of the O sheet. The I block contains <em>Tem> sites, statistically occupied by S and P, and Ba atoms. In the structures of innelite-1<em>Tem> and innelite-2<em>Mem>, TS blocks are related by an inversion centre and a <em>cem>_y glide plane, respectively. HRTEM images show a coherent intergrowth of the two polytypes, together with an as-yet unidentified ∼10 Å phase.