Tvrdýite, Fe2+Fe3+2A13(PO4)4(OH)5(OH2)4·2H2O, is a new phosphate mineral from the abandoned Huber open pit, in the Krásno ore district near Horní Slavkov, western Bohemia, Czech Republic. It was found along with Al-rich beraunite, fluorapatite and pharmacosiderite in a cavity of quartz gangue. Tvrdýite forms acicular to fibrous crystals with diameters in the range 0.5–5 μm and lengths up to 300 μm, partly grouped in radiating aggregates up to 3 mm in size. It has a silvery to olive, greyish green colour with pearly lustre, greyish-white streak and is very brittle with an uneven fracture; individual fibres are somewhat flexible. Cleavage on {100} is good; the Mohs hardness is ∼3–4. The calculated density is 2.834 g cm–3. Tvrdýite is optically biaxial (–), with α = 1.650(2), β = 1.671(1) and γ = 1.677(1) (white light); 2V = 56(1)°; dispersion: r > v, strong; optical orientation: Z = b, X ≈ a, Y ≈ c; pleochroism: X = greenish blue, Y = yellowish orange, Z = yellowish orange (X>> Y > Z). Tvrdýite is monoclinic, space group C2/c, a = 20.564(4), b = 5.101(1), c = 18.883(4) Å, β = 93.68(3)° and V = 1976.7(7) Å3, Z = 4, a:b:c= 4.031:1:3.702. The strongest eight lines in the powder X-ray diffraction (XRD) pattern [d in Å (I)(hkl)] are 10.227 (100) (200), 9.400 (6) (002), 7.156 (14) (202), 5.120 (7) (400), 3.416 (11) (600), 3.278 (6) (602), 2.562 (5) (800) and 2.0511 (3) (10,0,0). Chemical analyses by electron microprobe yielded MnO 0.01, ZnO 5.08, , FeO 4.31, Fe2O3 21.16, Al2O316.71, P2O5 32.64, As2O5 2.56, F 0.53, H2O (calc.) 17.84, O = F –0.22, total 100.62 wt.%. The resulting empirical formula, calculated on the base of 27 anions, obtained from the crystal structure, is Zn0.52Fe2+0.50Fe3+2.21Al2.75(PO4)3.86(AsO4)0.19OH4.60F0.23(OH2)4·2H2O. The ideal formula, Fe2+Fe3+2Al3(PO4)4(OH)5(OH2)4-2H2O, requires FeO 8.75, Fe2O3 19.44, Al2O3 18.62, P2O5 34.56, H2O 18.64, total 100.00 wt.%. The crystal structure of tvrdýite was solved from single-crystal data (synchrotron beamline) and refined to R1 = 0.038 for 2276 reflections with I > 2σ(I). Tvrdýite is isostructural with beraunite, but contains dominant Al in two of the four independent M sites, which are all occupied by Fe in beraunite.

Eleonorite, ideally Fe63+(PO4)4O(OH)4·6H2O, the analogue of beraunite Fe2+Fe53+(PO4)4O(OH)5·6H2O with Fe2+ completely substituted by Fe3+, has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification 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 the Rotläufchen mine, Waldgirmes, Wetzlar, Hesse, Germany, where eleonorite is associated with goethite, rockbridgeite, dufrénite, kidwellite, variscite, matulaite, planerite, cacoxenite, strengite and wavellite. Usually eleonorite occurs as red-brown prismatic crystals up to 0.2 mm × 0.5 mm × 3.5 mm in size 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 = 2.92(1), Dcalc = 2.931 g cm–3. 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 analysed 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 being trivalent from a Mössbauer analysis. The empirical formula (based on 27 O apfu) is (Fe5.763+Al0.18Mn0.093+)∑6.03(PO4)3.92O(OH)4.34·5.98H2O. The crystal structure (R = 0.0633) is similar to that of beraunite and is based on a heteropolyhedral framework 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) (202̄), 4.816 (31) (111, 004), 3.432 (18) (600, 114, 404, 313), 3.197 (18) (510, 511̄, 006, 314̄, 602), 3.071 (34) (314, 115̄).