FROM THE KOVDOR COMPLEX, RUSSIA

A new hollandite-type titanate, henrymeyerite, occurs in a vein of tetra-ferriphlogopite – calcite – dolomite carbonatite of the Kovdor alkaline ultramafic complex, Kola Peninsula, in Russia. The mineral was found in a single mineralized vug as acicular crystals less than 0.2 mm in length. The crystals represent a combination of two tetragonal prisms and a bipyramid. Henrymeyerite is opaque, black, and has an adamantine luster. In reflected light, the mineral is greyish brown and has a strong bireflectance. Reflectance values R « and Rv are given for l over the interval 420–720 nm. Henrymeyerite is associated with dolomite, fluorapatite, tetra-ferriphlogopite, rimkorolgite, catapleiite, collinsite, and pyrite. The composition of henrymeyerite, as deter-mined by electron microprobe, is (wt.%): BaO 18.25, TiO2 67.78, FeO 9.20, Nb2O5 1.00, Ce2O3 0.56, La2O3 0.50, Na2O 0.40, SiO2 0.37, K2O 0.05, CaO 0.02, sum 98.13. Stoichiometrically, this composition closely corresponds to the Ba–Fe end-member of the cryptomelane group, BaFe2+Ti7O16. Henrymeyerite is tetragonal, space group I4/m, Z = 1, a 10.219(3), c 2.963(1) Å, V 309.4(3) Å3. The crystal structure of the mineral was refined to R1 = 0.027 for 173 unique reflections with | Fo | ‡ 4sF using single-crystal X-ray-diffraction data. The structure of henrymeyerite corresponds to the undistorted hollandite archetype; no indication of splitting of the Ba site along [001] was observed. The available single-crystal data also indicate the absence of long-range order of the Ba2+ cations within the structural tunnels. The mineral is named for Prof. Henry O.A. Meyer (1937–1995) i