Steinmetzite, Zn (sub 2) Fe (super 3+) (PO (sub 4) ) (sub 2) (OH).3H (sub 2) O, a new mineral formed from alteration of phosphophyllite at the Hagendorf Sud Pegmatite, Bavaria

Steinmetzite, ideally Zn (sub 2) Fe (super 3+) (PO (sub 4) ) (sub 2) (OH).3H (sub 2) O, is a new mineral from the Hagendorf-Sud pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Steinmetzite was found in a highly oxidized zone of the Cornelia mine at Hagendorf-Sud. It has formed by alteration of phosphophyllite, involving oxidation of the iron and some replacement of Zn by Fe. Steinmetzite lamellae co-exist with an amorphous Fe-rich phosphate in pseudomorphed phosphophyllite crystals. The lamellae are only a few mu m thick and with maximum dimension approximately 50 mu m. The phosphophyllite pseudomorphs have a milky opaque appearance, often with a glazed yellow to orange weathering rind and with lengths ranging from sub-mm to 1 cm. Associated minerals are albite, apatite, chalcophanite, jahnsite, mitridatite, muscovite, quartz and wilhelmgumbelite. Goethite and cryptomelane are also abundant in the oxidized zone. The calculated density is 2.96 g cm (super -3) . Steinmetzite is biaxial (-) with measured refractive indices alpha = 1.642(2), beta = 1.659 (calc.), gamma = 1.660(2) (white light). 2V(meas) = 27(1) degrees ; orientation is Y nearly equal b, X^c nearly equal 27 degrees , with crystals flattened on {010} and elongated on [001]. Pleochroism shows shades of pale brown; Y > X nearly equal Z. Electron microprobe analyses (average of seven crystals) with Fe reported as Fe (sub 2) O (sub 3) and with H (sub 2) O calculated from the structure gave ZnO 31.1, MnO 1.7, CaO 0.5, Fe (sub 2) O (sub 3) 21.9, Al (sub 2) O (sub 3) 0.3, P (sub 2) O (sub 5) 32.9, H (sub 2) O 14.1 wt.%, total 102.5%. The empirical formula based on 2 P and 12 O, with all iron as ferric and OH (super -) adjusted for charge balance is Zn (sub 1.65) Fe (super 3+) (sub 1.19) Mn (super 2+) (sub 0.11) Ca (sub 0.03) Al (super 3+) (sub 0.02) (PO (sub 4) ) (sub 2) (OH) (sub 1.21) .2.79H (sub 2) O. The simplified formula is Zn (sub 2) Fe (super 3+) (PO (sub 4) ) (sub 2) (OH).3H (sub 2) O. Steinmetzite is triclinic, P1, with unit-cell parameters: a = 10.438(2), b = 5.102(1), c = 10.546(2) A, alpha = 91.37(2), beta = 115.93(2) and gamma = 94.20(2) degrees . V = 502.7(3) A (super 3) , Z = 2. The strongest lines in the powder X-ray diffraction pattern are [d (sub obs) in A (I) (hkl)] 9.313(65) (100), 5.077(38) (010), 4.726(47) (002), 4.657(100) (200), 3.365(55) (302), 3.071(54) (112) and 2.735(48) (312). The structure is related to that of phosphophyllite.