Jianmuite, $ZrTi4+Ti53+Al3O16$⁠, a new mineral from the Allende meteorite and from chromitite near Kangjinla, Tibet, China Available to Purchase

The new mineral jianmuite, $ZrTi4+Ti53+Al3O16$ (IMA No. 2023-057) was found: (1) as an inclusion in a corundum grain from the Cr-11 orebody near Kangjinla (29°11′N, 92°18′E), Tibet, China, with wenjiite, Ti₁₀(Si,P,□)₇, Al-rich spinel, osbornite, TiN, a Ca-amphibole particularly enriched in Ti, a Sr-rich dmisteinbergite, CaAl₂Si₂O₈, and amorphous phases (probably residual melt) (holotype and first cotype), and (2) as several grains with corundum, mullite, Al₆Si₂O₁₃, tistarite, Ti₂O₃, and kaitianite, $Ti23+Ti4+O5$⁠, in the matrix of the CV3 carbonaceous chondrite Allende (second cotype). Eight energy-dispersive spectroscopic analyses of the holotype normalized to 100% gave SiO₂ 1.83, ZrO₂ 23.17, Al₂O₃ 18.41, Ti₂O₃ 54.32, Sc₂O₃ 1.25, MgO 1.03, total 100.00 wt%. The empirical formula calculated on the basis of 10 cations and 16 O atoms is ^VIIIZr $(Ti3.0343+Ti0.6024+Zr0.364)Σ4.000VII$$(Ti1.8453+Al1.838Mg0.186Sc0.131)Σ4.000VI$^IV(Al_0.780Si_0.220)_Σ1.000 O₁₆. The simplified formula is Zr(Ti³⁺,Ti⁴⁺,Zr)₄(Ti³⁺,Al)₄(Al,Si)O₁₆ and the ideal chemical formula is $ZrTi4+Ti53+Al3O16$⁠, which requires calculated contents of ZrO₂ 17.23 wt%, TiO₂ 11.16 wt%, Ti₂O₃ 50.23 wt%, and Al₂O₃ 21.38 wt%, total 100 wt%. Six energy-dispersive spectroscopic analyses of the first cotype normalized to 100% gave SiO₂ 2.86, ZrO₂ 23.06, Al₂O₃ 18.10, Ti₂O₃ 53.78, Sc₂O₃ 1.17, MgO 1.04, total 100.00 wt%. Three-dimensional electron diffraction of the holotype determined jianmuite as I-centered tetragonal, space group: $(I4¯)$ (#82), with a = 10.3675(10) Å, b = 10.3675(10) Å, c = 9.8125(10) Å, V = 1054.70(18) ų, and Z = 4. Wavelength-dispersive spectroscopic electron probe microanalyses of Allende jianmuite (second cotype) gave for the two grains (5 analyses each) SiO₂ 2.32, 3.02, ZrO₂ 13.95, 10.79, Al₂O₃ 26.82, 21.83, Ti₂O₃ 44.68, 49.47, TiO₂ 12.62, 14.75, Sc₂O₃ 0.12, 0.04, MgO 0.19, 0.80, FeO, 0.52, 0.55, CaO 0.17, 0.08, total 101.40, 101.34 wt%. TiO₂ (wt%) and Ti₂O₃ (wt%) were calculated from formula units Ti⁴⁺ and Ti³⁺, which were determined assuming a stoichiometry of 10 cations and 16 O atoms. Electron backscatter diffraction (EBSD) patterns on the Allende jianmuite (second cotype) can be indexed by the tetragonal $I4¯$ structure obtained on the holotype, with a mean angular deviation of ∼0.7°, thereby confirming identification of the Allende mineral as jianmuite. The structure of jianmuite consists of cations packed in a distorted I-centered lattice. There are eight independent cation sites: two inside distorted cubes with tetragonal ridged faces (CN = 8), two inside capped trigonal prisms (CN = 7), two inside distorted octahedra (CN = 6), and two inside tetrahedra (CN = 4). All coordination polyhedra are connected by edges, except for the tetrahedra, which are connected by vertexes with other polyhedra. Despite the similarity in composition with carmeltazite, $ZrTi43+Al2O11$⁠, the structures of the two minerals bear little resemblance to one another, most notably in the number and type of cation-oxygen polyhedra. Instead, the jianmuite structure has several features in common with structures of pyrochlore-supergroup minerals, including similarity in unit-cell parameters, cubic a ≈ 10 Å and tetragonal a ≈ c ≈ 10 Å in pyrochlore and jianmuite, respectively, and cation packing being cubic I-centered in both structures.