Colours of gemmy phosphates from the Gavà neolithic mines (Catalonia, Spain): origin and archaeological significance



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Title: Colours of gemmy phosphates from the Gavà neolithic mines (Catalonia, Spain): origin and archaeological significance
Authors: Consorci del Museu de Ciències Naturals de Barcelona
Díaz-Acha, Yael
Campeny, Marc
Casas, Lluís
Di Febo, Roberta
Ibáñez-Insa, Jordi
Jawhari, Tariq
Bosch, Josep
Borrell, Ferran
Jorge-villar, Susana Esther
Greneche, Jean-Marc
Tauler, Esperança
Issue Date: 17-Mar-2022
Keywords: Jaciments minerals
Espectroscòpia Raman
Pedres precioses
Spatial coverage: Gavà (Catalonia)
Can Tintorer Site (Gavà, Catalonia)
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Extent: 27 p.
Abstract: In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and 57Fe Mössbauer spectrometry. Mapping of the mines indicates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr3+ and V+3 compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr3+. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler.
Terms of use: CC-BY
Terms of use details: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Appears in Collections:Petrologia / Articles

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