Eleonorite

[Stefan]

Eleonorite

Chukanov, Nikita V.; Aksenov, Sergey M.; Rastsvetaeva, Ramiza K.; Schäfer, Christof; Pekov, Igor V.; Belakovskiy, Dmitry I.; Scholz, Ricardo; De Oliveira, Luiz C. A.; Britvin, Sergey N. - Eleonorite, Fe3+6(PO4)4O(OH)4·6H2O: Validation as a mineral species and new data - Mineralogical Magazine [PREPUBLICATION 18. Feb. 2016]

Eleonorite, ideally Fe3+6(PO4)4O(OH)4·6H2O, the analogue of beraunite Fe2+Fe3+5(PO4)4(OH)5·6H2O with Fe2+ completely substituted by Fe3+, has been approved by the IMA CNMNC as a mineral species (IMA 2015-003). The mineral was first described on material from the Eleonore Iron mine, Dünsberg, near Gießen, Hesse, Germany, but during this study further samples were required and a neotype locality is presented at Rotläufchen mine, Waldgirmes, Wetzlar, Hesse, Germany, where eleonorite is associated with goethite, rockbridgeite, dufrenite, kidwellite, variscite, matulaite, planerite, cacoxenite, strengite and wavellite. Usually eleonorite occurs as red brown prismatic crystals up to 0.2×0.5×3.5 mm and in random or radial aggregates up to 5 mm across encrusting cavities in massive limonite. The mineral is brittle. Its Mohs’ hardness is 3. Dmeas = 1.92(1), Dcalc = 1.931 g/cm3. The IR spectrum is given. Eleonorite is optically biaxial (+), α = 1.765(4), β = 1.780(5), γ = 1.812 (6), 2Vmeas = 75(10)°, 2Vcalc = 70°. The chemical composition (electron-microprobe data, H2O analyzed by chromatography of products of ignition at 1200°C, wt.%) is: Al2O3 1.03, Mn2O3 0.82, Fe2O3 51.34, P2O5 31.06, H2O 16.4, total 99.58. All Iron was determined as trivalent from Mössbauer analysis. The empirical formula (based on 27 O apfu) is (Fe3+5.76Al0.18Mn3+0.09)Σ6.03(PO4)3.92O(OH)4.34·5.98H2O. The crystal structure (R = 0.0633) is similar to that of Beraunite and is based on heteropolyhedral framework which is formed by M(1-4)Ø6-octahedra (where M = Fe3+; Ø = O2-, OH- or H2O) and isolated PO4 tetrahedra, with a wide channel occupied by H2O molecules. Eleonorite is monoclinic, space group C2/c, a = 20.679(10), b = 5.148(2), c = 19.223(9) Å, β = 93.574(9)°, V = 2042.5(16) Å3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are: 10.41 (100) (200), 9.67 (38) (002), 7.30 (29) (20-2), 4.816 (31) (111, 004), 3.432 (18) (600, 114, 404, 313), 3.197 (18) (510, 51-1, 006, 31-4, 602), 3.071 (34) (314, 11-5).

[Stefan]

Dmeas = 1.92(1), Dcalc = 1.931 g/cm3

Ich denke das sollte vielmehr

Dmeas = 2.92(1), Dcalc = 2.931 g/cm3

sein. Das passt viel besser zu den angegebenen Daten.

[christof schäfer]

da hat sich in der Zusammenfassung ein Fehler eingeschlichen.
Im Aufsatz heißt es:
"The colour of the mineral is red-brown. The streak is light red-brown. The crystals of eleonorite are translucent, with vitreous lustre. The new mineral is brittle, with Mohs’ hardness of 3. Cleavage is perfect on (100). Density measured by flotation in heavy liquids (mixtures of diiodmethane with ethanol) is 2.92(1) g/cm3. Density calculated using the empirical formula is 2.931 g/cm3."

[Stefan]

Ja das passt schon deutlich besser. Danke!