Publication Date:
2018
Description:
〈div data-abstract-type="normal"〉〈p〉Schmidite, Zn(Fe〈span〉3+〈/span〉〈span〉0.5〈/span〉Mn〈span〉2+〈/span〉〈span〉0.5〈/span〉)〈span〉2〈/span〉ZnFe〈span〉3+〈/span〉(PO〈span〉4〈/span〉)〈span〉3〈/span〉(OH)〈span〉3〈/span〉(H〈span〉2〈/span〉O)〈span〉8〈/span〉 and wildenauerite, Zn(Fe〈span〉3+〈/span〉〈span〉0.5〈/span〉Mn〈span〉2+〈/span〉〈span〉0.5〈/span〉)〈span〉2〈/span〉Mn〈span〉2+〈/span〉Fe〈span〉3+〈/span〉(PO〈span〉4〈/span〉)〈span〉3〈/span〉(OH)〈span〉3〈/span〉(H〈span〉2〈/span〉O)〈span〉8〈/span〉 are two new oxidised schoonerite-group minerals from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Schmidite occurs as radiating sprays of orange–brown to copper-red laths on and near to altered phosphophyllite in a corroded triphylite nodule, whereas wildenauerite forms dense compacts of red laths, terminating Zn-bearing rockbridgeite. The minerals are biaxial (+) with α = 1.642(2), β = 1.680(1), γ = 1.735(2) and 2V〈span〉meas〈/span〉 = 81.4(8)° for schmidite, and with α = 1.659(3), β = 1.687(3), γ = 1.742(3) and 2V〈span〉meas〈/span〉 = 73(1)° for wildenauerite. Electron microprobe analyses, with H〈span〉2〈/span〉O from thermal analysis and FeO/Fe〈span〉2〈/span〉O〈span〉3〈/span〉 from Mössbauer spectroscopy, gave FeO 0.4, MgO 0.3, Fe〈span〉2〈/span〉O〈span〉3〈/span〉 23.5, MnO 9.0, ZnO 15.5, P〈span〉2〈/span〉O〈span〉5〈/span〉 27.6, H〈span〉2〈/span〉O 23.3, total 99.6 wt.% for schmidite, and FeO 0.7, MgO 0.3, Fe〈span〉2〈/span〉O〈span〉3〈/span〉 25.2, MnO 10.7, ZnO 11.5, P〈span〉2〈/span〉O〈span〉5〈/span〉 27.2, H〈span〉2〈/span〉O 24.5, total 100.1 wt.% for wildenauerite. The empirical formulae, scaled to 3 P and with OH〈span〉–〈/span〉 adjusted for charge balance are Zn〈span〉1.47〈/span〉Mn〈span〉2+〈/span〉〈span〉0.98〈/span〉Mg〈span〉0.05〈/span〉Fe〈span〉2+〈/span〉〈span〉0.04〈/span〉Fe〈span〉3+〈/span〉〈span〉2.27〈/span〉(PO〈span〉4〈/span〉)〈span〉3〈/span〉(OH)〈span〉2.89〈/span〉(H〈span〉2〈/span〉O)〈span〉8.54〈/span〉 for schmidite and Zn〈span〉1.11〈/span〉Mn〈span〉2+〈/span〉〈span〉1.18〈/span〉Mg〈span〉0.05〈/span〉Fe〈span〉2+〈/span〉〈span〉0.08〈/span〉Fe〈span〉3+〈/span〉〈span〉2.47〈/span〉(PO〈span〉4〈/span〉)〈span〉3〈/span〉(OH)〈span〉3.25〈/span〉(H〈span〉2〈/span〉O)〈span〉9.03〈/span〉 for wildenauerite. The two minerals have orthorhombic symmetry, space group 〈span〉Pmab〈/span〉 and 〈span〉Z〈/span〉 = 4. The unit-cell parameters from refinement of powder X-ray diffraction data are 〈span〉a〈/span〉 = 11.059(1), 〈span〉b〈/span〉 = 25.452(1) and 〈span〉c〈/span〉 = 6.427(1) Å for schmidite, and 〈span〉a〈/span〉 = 11.082(1), 〈span〉b〈/span〉 = 25.498(2) and 〈span〉c〈/span〉 = 6.436(1) Å for wildenauerite. The crystal structures of schmidite and wildenauerite differ from that of schoonerite in having minor partitioning of Zn from the 〈span〉[5]〈/span〉Zn site to an adjacent vacant tetrahedral site 〈span〉[4]〈/span〉Zn, separated by ~1.0 Å from 〈span〉[5]〈/span〉Zn. The two minerals are distinguished by the cation occupancies in the octahedral 〈span〉M〈/span〉1 to 〈span〉M〈/span〉3 sites. Schmidite has 〈span〉M〈/span〉1 = 〈span〉M〈/span〉2 = (Fe〈span〉3+〈/span〉〈span〉0.5〈/span〉Mn〈span〉2+〈/span〉〈span〉0.5〈/span〉) and 〈span〉M〈/span〉3 = Zn and wildenauerite has 〈span〉M〈/span〉1 = 〈span〉M〈/span〉2 = (Fe〈span〉3+〈/span〉〈span〉0.5〈/span〉Mn〈span〉2+〈/span〉〈span〉0.5〈/span〉) and 〈span〉M〈/span〉3 = Mn〈span〉2+〈/span〉.〈/p〉〈/div〉
Print ISSN:
0026-461X
Electronic ISSN:
1471-8022
Topics:
Geosciences
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