Meierite, ideally Ba44Si66Al30O192Cl25(OH)33, is a new mineral from the Gun claim, just south of the Itsi Range, Yukon, Canada. Meierite occurs as equant grains up to 200 μm across, enclosed within large gillespite crystals. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle with no observed cleavage. The calculated density based upon the chemical formula and single-crystal unit-cell dimension is 3.50 g/cm3. The mineral is optically isotropic (n = 1.598) Electron-microprobe composition (average of 11): SiO2 28.30, P2O5 1.61, Al2O3 11.75, TiO2 0.05, FeO 0.27, CaO 0.21, BaO 47.61, Na2O 0.15, K2O 0.21, Cl 6.64, and a total of 95.29 wt.%. The empirical formula (based on 192 framework O apfu) and charge balance considerations is: Ba41.1Ca0.5Fe0.5Na0.7K0.6Si62.5Al30.5P3.0O192Cl24.8·33.4(OH). It is possible that additional H2O molecules are located within the cavities in the structure. Meierite is cubic, Imm, a 18.5502(4) Å, V 6383.3(2) Å3, and Z = 1. The 10 most intense lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 4.39(70)(411), 4.16(26)(420), 3.798(25)(422), 3.288(34)(440), 3.189(100)(433), 3.016(72)(611), 2.803(42)(622), 2.629(31)(710), 2.323(46)(800), and 2.287(59)(741).

The crystal structure (R = 4.1% for 1393 Fo > 4σF) is a three dimensional framework of silicon-, aluminium-, and phosphorous-containing tetrahedra that create an open framework consisting of a large cubo-octahedral cavity connected by channels composed of double eight-membered rings and double six-membered rings. The aluminosilicate framework is isostructural with that observed for silicate framework type ZK-5 (KFI). The mineral is named in honor of Walter M. Meier (1926–2009), a pioneer in zeolite research.

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