Mineralogical and gemological characterization of emerald crystals from Paraná deposit, NE Brazil: a study of mineral chemistry, absorption and reflectance spectroscopy and thermal analysis

dc.contributoren-US
dc.contributorpt-BR
dc.creatorAraújo Neto, José Ferreira de
dc.creatorBarreto, Sandra de Brito
dc.creatorCarrino, Thais Andressa
dc.creatorMüller, Axel
dc.creatorSantos, Lauro Cézar Montefalco de Lira
dc.date2020-05-04
dc.date.accessioned2022-12-15T20:11:27Z
dc.date.available2022-12-15T20:11:27Z
dc.identifierhttps://ppegeo.igc.usp.br/index.php/bjg/article/view/13539
dc.identifier10.1590/2317-4889201920190014
dc.identifier.urihttps://repositorioslatinoamericanos.uchile.cl/handle/2250/5360135
dc.descriptionThe Paraná deposit, located at Southwestern Rio Grande do Norte state, in Brazil, is one of the few emerald deposits found at Borborema Province. The mineralization occurs in phlogopite schists and actinolite-phlogopite schists associated with pegmatites and albitites within the Portalegre Shear Zone. Unlike other well-known Brazilian emerald deposits, the mineralogy of Paraná emeralds has remained poorly investigated for the last 40 years. In this study, we conducted mineralogical characterization of theses emeralds through gemological testing, mineral chemistry, absorption and reflectance spectroscopy, and thermal analysis. The Paraná emeralds are bluish-green colored, characterized by high refractive index, several two-phase fluid inclusions and mica is the main mineral inclusion. Electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry analyses detected the presence of Fe2+ (0.43–1.94 wt.% FeO) and Cr3+ (0.04–0.14 wt.% Cr2 O3 ) as the main chromophores replacing octahedral Al3+ in the crystal structure. In addition, substantial amounts of MgO (0.40–2.72 wt.%), Na2 O (0.50–1.81 wt.%), and Cs2 O (0.07–0.44 wt.%) were also identified. The main causes for its coloration were attributed to Cr3+ absorption features in visible spectral range, which were corroborated by absorption and reflectance spectra. The presence of types I and II H2 O at channel-sites was recorded in Fourier-transform infrared spectra and demonstrated by dehydration processes observed in different thermal and thermogravimetric analyses.en-US
dc.descriptionpt-BR
dc.formatapplication/pdf
dc.languageeng
dc.publisherSociedade Brasileira de Geologiapt-BR
dc.relationhttps://ppegeo.igc.usp.br/index.php/bjg/article/view/13539/13134
dc.rightsDireitos autorais 2020 Brazilian Journal of Geologypt-BR
dc.sourceBrazilian Journal og Geology; v. 49, n. 3 (2019); 1-15en-US
dc.sourceBrazilian Journal of Geology; v. 49, n. 3 (2019); 1-15pt-BR
dc.source2317-4692
dc.source2317-4889
dc.subjectParaná emerald; Mineralogy; Gemology; Geochemistry; Spectroscopy.en-US
dc.subjectpt-BR
dc.titleMineralogical and gemological characterization of emerald crystals from Paraná deposit, NE Brazil: a study of mineral chemistry, absorption and reflectance spectroscopy and thermal analysisen-US
dc.titlept-BR
dc.typeinfo:eu-repo/semantics/article
dc.typeinfo:eu-repo/semantics/publishedVersion
dc.typeen-US
dc.typept-BR


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