Publication details
Manganrockbridgeite from the Jocão claim, Conselheiro Pena, Minas Gerais, Brazil: chemistry, spectroscopic and structural data
| Authors | |
|---|---|
| Year of publication | 2024 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Geosciences |
| MU Faculty or unit | |
| Citation | |
| web | http://www.jgeosci.org/content/jgeosci_387_Tvrdy.pdf |
| Doi | http://dx.doi.org/10.3190/jgeosci.387 |
| Keywords | manganrockbridgeite; phosphate minerals; Jocao pegmatite; Minas Gerais; Brazil |
| Description | The world's second occurrence of the recently described manganrockbridgeite was found in a mineral assemblage in the Jocao (Cigana) pegmatite, Conselheiro Pena district, Minas Gerais (Brazil). Manganrockbridgeite forms green botryoidal-crystalline crusts with a velvety surface covering the walls of leached cavities in triphylite replaced by correianevesite and Mn-rich vivianite. The outer zone is significantly richer in Mn than the inner zone where the manganrockbridgeite passes to frondelite. Other associated minerals are hureaulite and kenngottite-like phosphate. Empirical formulae based on EPMA, Mössbauer and XPS spectroscopy are (Mn1.36Fe2+0.46Fe3+0.09Ca0.03Mg0.01?0.05)?2.00Fe3+2.95(PO4)3.00(OH)3.84(H2O)1.16 for the outer zone and (Mn1.03Fe2+0.49Fe3+0.29Ca0.03Mg0.02?0.14)?2.00Fe3+2.94(PO4)3.00(OH)3.81(H2O)1.19 for the inner zone of aggregates. Raman spectra and assignment of individual decomposed bands to vibrational modes show a good agreement with data published for frondelite from the Jocao locality. By powder diffraction data the studied manganrockbridgeite corresponds to the type material from Hagendorf-Süd, Germany. Unit-cell parameters for space group P21/m are a = 5.195(2) A, b = 16.936(4) A, c = 7.452(2) A, ß = 110.25(3)° and V = 615.1(4) A3. |
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