Staněkite, Fe3+(Mn,Fe2+,Mg)(PO4): a new phosphate mineral in pegmatites at Karibib (Namibia) and French Pyrénées (France) (original) (raw)

Original paper

Keller, Paul; Fontan, François; Velasco Roldan, Francisco; Melgarejo I Draper, Joan Carles

Abstract

Abstract Stanékite is a new mineral with the ideal formula Fe3+(Mn,Fe2+,Mg)(PO4)O and structurally similar to triploidite-wolfeite. It was first found in the Clementine II pegmatite, Okatjimukuju farm, Karibib (Namibia), and was later also detected in pegmatites from Albères, Eastern Pyrénées. Stanékite exhibits a black lustre and occurs generally as unhedral grains. Simple forms with rough (120) faces were occasionally seen. The new mineral is paragenetically associated with ferrisicklerite, heterosite, kryzhanovskite, arrojadite, eosphorite, and alluaudite s.l. It is monoclinic, space group P21/a, a 11.844(3), b 12.662(3), c 9.989(3) Kß 105.93(2)°, Z = 16, Dx = 4.09 g/cm3. Strongest lines of X-ray powder pattern d(I)hkl are as follows: 2.971(100)14-1, 2.809(85)40-2, 2.857(58)023, 3.259(50) 202, 3.412 (38)122, 5.54(37)120, 3.621(35)221, 2.548(30)24-2, 1.779(28) 522/54-3/44-4. There are strong substructure reflections found on levels with k even and have indices for which hkl: h + l/2k + 1 = 2n and h01: h = 2n. The resulting space group of the subcell is 121a, with asub = a, bsub = 1/2b, and csub = c. Microprobe analysis revealed the following chemical composition (in wt%): Na2O 0.13, MgO 0.50, CaO 0.13, MnO 23.12, FeO 1.56, ZnO 0.22, Fe2O3 41.52, and P2O5 31.16. The empirical formula based on 5 O atoms is: (Fe3+1.16Mn2+0.73Fe2+0.05Mg0.03 Na0.01)Σ1.98(P0.98O4)O. The name of the new mineral honours Prof. Dr. Josef Stanék, University Masarykovy of Brno, Czech Republic.

Keywords

stanékite • Fe3+(Mn,Fe2+,Mg)(PO4)O • new phosphate mineral • granitic pegmatite • Karibib (Namibia) • Pyrenees (France).