Description and crystal structure of a new mineral - plimerite, ZnFe3+4(PO4)3(OH)5 - the Zn-analogue of rockbridgeite and frondelite, from Broken Hill, New South Wales, Australia
- Author(s)
- Uwe Kolitsch, P Elliott, Gerald Giester, Eugen Libowitzky, Catherine McCammon, Allan Pring, William D. Birch, Joel Brugger
- Abstract
Plimerite, ideally ZnFe3+4(PO4)3(OH)5, is a new mineral from the Block 14 Opencut, Broken Hill, New South Wales. It occurs as pale-green to dark-olive-green, almost black, acicular to prismatic and bladed crystals up to 0.5 mm long and as hemispherical aggregates of radiating acicular crystals up to 3 mm across. Crystals are elongated along [001] and the principal form observed is {100} with minor {010} and {001}. The mineral is associated with hinsdalite-plumbogummite, pyromorphite, libethenite, brochantite, malachite, tsumebite and strengite. Plimerite is translucent with a pale-greyish-green streak and a vitreous lustre. It shows an excellent cleavage parallel to {100} and {010} and distinct cleavage parallel to {001}. It is brittle, has an uneven fracture, a Mohs' hardness of 3.5-4, D(meas.) = 3.67(5) g/cm3 and D(calc.) = 3.62 g/cm3 (for the empirical formula). Optically, it is biaxial negative with a = 1.756(5), ß = 1.764(4), ? = 1.767(4) and 2V(calc.) of -63°; pleochroism is X pale-greenish-brown, Y pale-brown, Z pale-bluish-green; absorption Z > X > Y; optical orientation XYZ = cab. Plimerite is orthorhombic, space group Bbmm, unit-cell parameters: a = 13.865(3) Å, b = 16.798(3) Å, c = 5.151(10) Å, V = 1187.0(4) Å3 (single-crystal data) and Z = 4. Strongest lines in the X-ray powder diffraction pattern are [d (Å), I, hkl]: 4.638, (50), (111); 3.388, (50), (041); 3.369, (55), (131); 3.168, (100), (132); 2.753, (60), (115); 2.575, (90), (200); 2.414, (75), (220); 2.400, (50), (221); 1.957, (40), (225). Electron microprobe analysis yielded (wt.%): PbO 0.36, CaO 0.17, ZnO 20.17, MnO 0.02, Fe2O3 29.82, FeO 2.98, Al2O3 4.48, P2O5 32.37, As2O5 0.09, H2O (calc) 6.84, total 97.30 (Fe3+/Fe2+ ratio determined by Mössbauer spectroscopy). The empirical formula calculated on the basis of 17 oxygens is Ca0.02Pb0.01Zn1.68Fe2+0.28Fe3+2.53Al0.60P3.09As0.01O17.00H5.15. The crystal structure was solved by direct methods and refined to an R1 index of 6.41% for 1332 observed reflections from single-crystal X-ray diffraction data (Mo-Ka radiation, CCD area detector). The structure of plimerite is isotypic with that of rockbridgeite and is based on face-sharing trimers of (Mf6) octahedra which link by sharing edges to form chains, that extend in the b-direction. Chains link to clusters comprising pairs of corner-sharing (Mf6) octahedra that link to PO4 tetrahedra forming sheets parallel to (001). The sheets link via octahedra and tetrahedra corners into a heteropolyhedral framework structure. The mineral name honours Professor Ian Plimer for his contributions to the study of the geology of ore deposits.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- University of Adelaide, Universität Bayreuth, Flinders University, Museums Victoria
- Journal
- Mineralogical Magazine
- Volume
- 73
- Pages
- 131-148
- No. of pages
- 18
- ISSN
- 0026-461X
- Publication date
- 2009
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/description-and-crystal-structure-of-a-new-mineral--plimerite-znfe34po43oh5--the-znanalogue-of-rockbridgeite-and-frondelite-from-broken-hill-new-south-wales-australia(dfa2b123-d81e-45bc-8238-f2f8cf69a5a0).html