Allanpringite, Fe (sub 3) (PO (sub 4) ) (sub 2) (OH) (sub 3) .5H (sub 2) O, a new ferric iron phosphate from Germany, and its close relation to wavellite

Allanpringite occurs on the dump of the abandoned Grube Mark near Essershausen, approximately 5 km SE of Weilburg/Lahn, Taunus, Hesse, Germany, as pale brown-yellow, {010] acicular, invariably twinned crystals which are always intergrown to form bundles of sub-parallel individuals. The maximum length of crystals is approximately 1.5 mm (usually much smaller). The mineral is associated with the reddish 'oxiberaunite' variety of beraunite, cacoxenite, strengite and cryptomelane; it is translucent to transparent and has a vitreous lustre; perfect cleavage parallel to the elongation and one good cleavage parallel to {010}; H. approximately 3, D 2.54 g/cm (super 3) ; alpha (colourless) 1.662, beta (colourless), 1.675, gamma (dark yellow) 1.747, 2V (sub gamma ) calc 48 degrees . EPMA gave Fe (sub 2) O (sub 3) = 47.84, Al (sub 2) O (sub 3) 0.34, Mn (sub 2) O (sub 3) 0.04, CuO 0.08, P (sub 2) O (sub 5) 28.56, F 0.02, H (sub 2) O (sub calc) 23.49, less O = F 0.01, = 100.36%, leading to the idealized formula Fe (sub 3) (PO (sub 4) ) (sub 2) (OH) (sub 3) .5H (sub 2) O. Indexed XRD powder data are tabulated; strongest lines 8.90(100), 3.2321(80), 8.41(60), 5.870(50), 3.600(50) Aa; a 9.777, b 7.358, c 17.830 Aa. beta 92.19 degrees , V 1281.7 Aa (super 3) , Z = 4, space group P2 (sub 1) /n. The crystal structure has been determined using a twinned fragment; it consists of a monoclinically distorted, pseudo-orthorhombic variant of the orthorhombic structure of its Al analogue wavellite. Chains of corner-sharing, distorted Fe(O,OH,H (sub 2) O) (sub 6) octahedra parallel to [010] are corner-linked by PO (sub 4 ) tetrahedra. Channels,also parallel to [010], host a positionally split water molecule. The name honours Dr. Allan Pring, eminent Australian mineralogist.