Abstract
The new mineral species rüdlingerite, ideally Mn2+2V5+As5+O7·2H2O, occurs in the Fianel mine, in Val Ferrera, Grisons, Switzerland, a small Alpine metamorphic Mn deposit. It is associated with ansermetite and Fe oxyhydroxide in thin fractures in Triassic dolomitic marbles. Rüdlingerite was also found in specimens recovered from the dump of the Valletta mine, Canosio, Cuneo, Piedmont, Italy, where it occurs together with massive braccoite and several other As- and V-rich phases in richly mineralized veins crossing the quartz-hematite ore. The new mineral displays at both localities yellow to orange, flattened elongated prismatic, euhedral crystals measuring up to 300 μm in length. Electron-microprobe analysis of rüdlingerite from Fianel gave (in wt%): MnO 36.84, FeO 0.06, As2O5, 25.32, V2O5 28.05, SiO2 0.13, H2Ocalc 9.51, total 99.91. On the basis of 9 O anions per formula unit, the chemical formula of rüdlingerite is Mn1.97(V5+1.17 As0.83Si0.01)Σ2.01O7·2H2O. The main diffraction lines are [dobs in Å (Iobs) hkl]: 3.048 (100) 022, 5.34 (80) 120, 2.730 (60) 231, 2.206 (60) 16-1, 7.28 (50) 020, 2.344 (50) 250, 6.88 (40) 110, and 2.452 (40) 320. Study of the crystal structure showcases a monoclinic unit cell, space group P21/n, with a = 7.8289(2) Å, b = 14.5673(4) Å, c = 6.7011(2) Å, β = 93.773(2)°, V = 762.58(4) Å3, Z = 4. The crystal structure has been solved and refined to R1 = 0.041 on the basis of 3784 reflections with Fo > 4σ(F). It shows Mn2+ hosted in chains of octahedra that are subparallel to [-101] and bound together by pairs of tetrahedra hosted by V5+ and As5+, building up a framework. Additional linkage is provided by hydrogen-bonding through H2O coordinating Mn2+ at the octahedra. One tetrahedrally coordinated site is dominated by V5+, T(1)(V0.88As0.12), corresponding to an observed site scattering of 24.20 electrons per site (eps), whereas the second site is strongly dominated by As5+,T(2)(As0.74V0.26), with, accordingly, a higher observed site scattering of 30.40 eps. The new mineral has been approved by the IMA-CNMNC and named for Gottfried Rüdlinger (born 1919), a pioneer in the 1960–1980s, in the search and study of the small minerals from the Alpine manganese mineral deposits of Grisons.
Highlights
In 1996, Brugger and Berlepsch (1996) [1] described fianelite, the only second Mn vanadate and the first new mineral species for the Fianel mine, where the exotic mineral association was summarily sensed by Stucky (1960) [2]
Rüdlingerite was found in a specimen labeled as “fianelite”, originally from the Fianel mine in Val Ferrera, Grisons, Switzerland (46◦ 32’47” N, 9◦ 27’43” E)
A Raman spectrum of rüdlingerite from Fianel mine was obtained with a Leica DM 2500 microscope, equipped with 5×, 10×, 20×, 50×, and 100× objectives and part of a Renishaw inVia spectrometer, which includes a monochromator, a filter system, and a Charge Coupled Device (CCD), located in the Natural History Museum of Geneva, Geneva, Switzerland
Summary
In 1996, Brugger and Berlepsch (1996) [1] described fianelite, the only second Mn vanadate and the first new mineral species for the Fianel mine, where the exotic mineral association was summarily sensed by Stucky (1960) [2]. Two new Mn species, ansermetite [3] and scheuchzerite [4], followed In their description of fianelite, Mn2 V2 O7 ·2H2 O, Brugger and Berlepsch (1996) [1] noticed that substitution of As for V occurs on the second tetrahedrally coordinated V site and that As could potentially even dominate in this site. Sticking to the general dominant-constituent rule and thereby considering that the homovalent substitution encountered at the two tetrahedrally coordinated sites in this phase is not a complex system, the new mineral and its name, rüdlingerite, were submitted to and accepted by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical. Rüdlinger was long-time president of the local section of the Swiss association of ‘strahlers’ and mineral collectors and designed the mineral exhibit at the Nature Museum in Chur [8]
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