• journal_title：Mineralogical Magazine
• Contributor：I. E. Grey ; K. Steinike ; C. M. MacRae
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2013.077.1.05
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：77
• issue：1
• firstpage：45
• section：Letter

Kleberite, ideally Fe³⁺Ti₆O₁₁(OH)₅, is a new mineral (IMA 2012-023) from Tertiary sands at Königshain, Saxony, northeast Germany. It is also found in heavy mineral sands from the Murray Basin, southeast Australia and at Kalimantan, Indonesia. It occurs as rounded anhedral to euhedral translucent grains, 0.04–0.3 mm across, which are generally red-brown, but grade to orange with decreasing iron content. Associated minerals include ilmenite, pseudorutile, ‘leucoxene’, tourmaline and spinel. The density measured by pycnometry is 3.28 g cm⁻³, which is lower than the calculated density of 3.91 g cm⁻³, due to intragrain porosity which is not penetrated by the immersion fluid. The intragrain pores, of median diameter 18 nm, are partially filled with impurity phases including kaolinite, diaspore and quartz. Kleberite grains have a uniaxial (−) character, but localized regions are weakly biaxial (−) with 2V close to zero. The mean refractive index, calculated from reflectance measurements, is 2.16(3). The mean empirical formula from electron-microprobe analyses of 15 Königshain kleberite grains is Mg_0.06Ti₆O_11.2(OH)_4.8[Al_0.59Si_0.31P_0.04O_1.60·1.8H₂O], where the formula element in square brackets represents impurities in the pores. Kleberite forms over a compositional range with [Ti]/[Fe + Ti] atomic ratios from 0.8–0.9. It has monoclinic symmetry, P2₁/c, with a = 7.537(1), b = 4.5795(4), c = 9.885(1) Å, β = 131.02(1)°. The six strongest lines in the powder X-ray diffraction (XRD) pattern [listed as d in Å (I)] are as follows: 1.676(100), 2.170(82), 2.466(27), 1.423(22), 3.933(8), 2.764(9). The structure was refined by the Rietveld method on powder XRD data to R_p = 6.3, R_wp = 8.1, R_B = 4.0. Kleberite is isostructural with tivanite; their structural formulae are [ □][ Fe³⁺]O₁₁(OH)₅ and [ ][ ]O₁₂(OH)₄, respectively. Kleberite has dominant Ti⁴⁺ in place of V³⁺ in the M(2) metal-atom site. The related mineral pseudorutile, [Ti₄][(Fe³⁺,Ti)₄](O,OH)₁₆, with Fe³⁺ > Ti⁴⁺ has dominant Fe³⁺ in this site. Kleberite grains from different localities commonly contain residual MgO-rich ferrian ilmenite. The chemical and physical relationships between the ilmenite and coexisting kleberite are used to evaluate different alteration mechanisms involving selective leaching of divalent oxides from ilmenite and pseudomorphic replacement reactions, respectively.