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 tunnels dug on other similar greenish minerals such as smectite or kandite. A 3D study of distribution mineral phases allows us to determine parameters involved in colours. Methods are comprised quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, 57Fe Mössbauer spectrometry. Mapping mines indicates that colour is not directly dependent depth. Although from poor Cr3+ V+3 compared with gemmy localities, deep green samples content has highest values Cr3+. case cryptocrystalline mixtures jarosite, phosphosiderite, goethite, tends acquire a brown olivaceous hue. If white quartz, kandite, crandallite, alunite mixtures, colours become paler.