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

• Published in: European journal of mineralogy (Stuttgart) Vol. 35; no. 1; pp. 95 - 103
• Main Authors: Hochleitner, Rupert, Rewitzer, Christian, Grey, Ian E., Mumme, William G., MacRae, Colin M., Kampf, Anthony R., Keck, Erich, Gable, Robert W., Glenn, Alexander M.
• Format: Journal Article
• Language: English
• Published: Göttingen Copernicus GmbH 14.02.2023; Copernicus Publications
• Subjects: Aluminum; Composition; Crystal structure; Crystals; Diameters; Electron probes; Empirical analysis; Iron; Manganese; Mineralogy; Minerals; Pegmatite; Pegmatites; Phosphates; Quartz; Single crystals; Sprays; Structure; Subgroups; Testing; Germany; Bavaria Germany
• ISSN: 1617-4011; 0935-1221; 1617-4011
• DOI: 10.5194/ejm-35-95-2023

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.