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Mineralogical and cathodoluminescence characteristics of Ca-rich kutnohorite from the Úrkút Mn-carbonate mineralization, Hungary
Published online by Cambridge University Press: 05 July 2018
Abstract
Kutnohorite with moderate and bright orange-red cathodoluminescence (CL) was studied by CL microscopy and spectroscopy. This mineral was found in fossiliferous concretions composed mainly of rhodochrosite from the Mn-carbonate mineralization at Úrkút, Hungary. The CL microscopy reveals that kutnohorite occurs as impregnations, layers and veinlets. X-ray diffraction, infrared spectroscopy and electron microprobe studies indicate that the luminescent kutnohorite has excess Ca (72.9–80.0 mol.% CaCO3, 16.3–20.5 mol.% MnCO3, 3.3–5.6 mol.% MgCO3 and 0.0–0.5 mol.% FeCO3). Transmission electron microscopy shows that the luminescent carbonate has a dolomite-type structure, with modulated and mosaic microstructures. The CL spectra of this Ca-rich kutnohorite have a single emission band at 630 nm that is characteristic of Mn2+ substitution in the structure. Our results provide evidence for moderate-to-bright cathodoluminescence of Mn-rich natural carbonates even at 8–10 wt.% Mn and up to 2400 ppm Fe. The self-quenching of Mn appears incomplete in the case of Ca-rich kutnohorite from Úrkút.
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- Copyright © The Mineralogical Society of Great Britain and Ireland 2007
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