Whiteite-(CaMnFe), a new jahnsite-group mineral from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria

Abstract

Abstract. Whiteite-(CaMnFe), CaMn2+Fe22+Al2(PO4)4(OH)2 ⋅ 8H2O, is a new whiteite-subgroup member of the jahnsite group from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in vugs in an altered feldspar area of a specimen composed predominantly of rockbridgeite, with hureaulite and relic triphylite. Other associated minerals in small vugs in the specimen were strengite and laueite. Whiteite-(CaMnFe) occurs as sprays and clusters of colourless to pale yellow, rod-like crystals, with diameters of typically 10 to 50 µm and lengths up to ∼ 500 µm. The crystals are flattened on {001} and elongated along [010]. The measured density is 2.80(2) g cm−3. Optically, whiteite-(CaMnFe) crystals are biaxial (+), with α=1.608(3), β=1.612(3), γ=1.624(3) and 2V(meas.) = 59(1)∘. The empirical formula from electron microprobe analyses and structure refinement is (Ca0.70Mn0.30)Mn(Fe1.232+Mn0.49Mg0.29Zn0.06)(Al1.88Fe0.123+)(PO4)3.96(OH)2(H2O)8. Whiteite-(CaMnFe) is monoclinic, P2 /a, a=14.925(5), b=7.0100(14), c=10.053(2) Å, β=111.31(2)∘, V=979.9(4) Å3 and Z=2. The crystal structure was refined using single-crystal data to wRobs=0.052 for 1613 reflections with I>3σ(I). Site occupancy refinements confirm the ordering of dominant Ca, Mn and Fe2+ in the X, M1 and M2 sites, respectively, of the general jahnsite-group formula XM1M22M32(H2O)8(OH)2(PO4)4.

Fluor-rewitzerite, [(H2O)K]Mn2(Al2Ti)(PO4)4(OF)(H2O)10 ⋅ 4H2O, a new paulkerrite-group mineral, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany

“…The combination of a very small deviation of β from 90°, ubiquitous twinning and large mosaicity makes it difficult to determine the correct symmetry using conventional sealed-tube laboratory diffractometer data. Recent microfocus synchrotron data collected on the new paulkerrite-group minerals, rewitzerite (Grey et al, 2023a), hydroxylbenyacarite (Hochleitner et al, 2024) and macraeite (Grey et al, 2024), have confirmed the monoclinic character of these minerals. It is likely that the crystal structure of benyacarite is also of monoclinic symmetry.…”

“…Reconstructed precession images of the diffraction data for this mineral show that the reflections (hk0), h = 2n + 1, and (0kl), k = 2n + 1, are diffuse with streaking parallel to b * (Hochleitner et al, 2024). The lengths of the diffuse streaks correspond to correlation lengths of only 1 to 2 nm, so the Asite ordering is restricted to domains on the scale of the unit cell.…”

“…Refinement of the K/O ratio at the A sites gave K occupancies lower than the K content analysed by electron microprobe (EMP). A likely explanation for this discrepancy is that the A sites also contain vacancies, as reported for other paulkerrite-group minerals (Hochleitner et al, 2024;Rewitzer et al, 2024). Adjusting the vacancy content gave a reasonable match to the EMPderived K content for 0.1 vacancies per A site.…”

“…Ternary diagram for (M2) 2 M3 site Al-Ti-Fe 3+ compositions, showing end-member compositions (Al 2 Ti, Ti 2 Al, etc.) and location of the empirical composition for fluor-rewitzerite, For comparison the published empirical compositions are shown for the paulkerrite-group minerals benyacarite(Demartin et al, 1997), hochleitnerite(Grey et al, 2023d), hydroxylbenyacarite(Hochleitner et al, 2024), mantienneite(Fransolet et al, 1984), paulkerrite(Peacor et al, 1984), pleysteinite(Grey et al, 2023c), rewitzerite(Grey et al, 2023a) and macraeite(Grey et al, 2024). Red crosses correspond to minerals with Mn at M1, and blue crosses correspond to minerals with Mg at M1.…”

Sperlingite, (H2O)K(Mn2+Fe3+)(Al2Ti)(PO4)4[O(OH)][(H2O)9(OH)]⋅4H2O, a new paulkerrite-group mineral, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany.

“…Up to 1984, ten new minerals were published, including the phosphate minerals jungite, keckite, laueite, lehnerite, parascholzite, pseudolaueite, scholzite and wilhelmvierlingite as documented by Kastning and Schlüter (1994), while post-1984 another twenty three type specimens have been added. Of particular relevance to this study is the characterisation of the paulkerrite-group minerals pleysteinite (Grey et al, 2023a ), hochleitnerite (Grey et al, 2023b), rewitzerite (Grey et al, 2023c ) and fluorrewitzerite (Hochleitner et al, 2024). Their formulae and unit-cell parsameters are given in Table 1.…”