Colours of Gemmy Phosphates from the Gavà Neolithic Mines (Catalonia, Spain): Origin and Archaeological Significance

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...

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Bibliographic Details
Published inMinerals (Basel) Vol. 12; no. 3; p. 368
Main Authors Díaz-Acha, Yael, Campeny, Marc, Casas, Lluís, Di Febo, Roberta, Ibañez-Insa, Jordi, Jawhari, Tariq, Bosch, Josep, Borrell, Ferran, Jorge-Villar, Susana Esther, Greneche, Jean-Marc, Tauler, Esperança, Melgarejo, Joan Carles
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.03.2022
MDPI
Subjects
Alunite
Analytical methods
Archaeology
Color
Colour
Earth Sciences
Gavà
Geology
Goethite
Iron 57
Jarosite
Mineralization
Minerals
Mines
Mining
Mixtures
Neolithic
neolithic mines
Oxidation
Petrography
Petrology
Phosphates
Raman spectroscopy
Sciences of the Universe
Sediments
Smectites
Spectrometry
Stone Age
Trivalent chromium
Tunnels
turquoise
variscite
France
Spain
colour
variscite
turquoise
Gavà
phosphates
neolithic mines
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Summary: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.
ISSN:2075-163X
2075-163X
DOI:10.3390/min12030368