Cyanotrichite in a prehistoric turquoise mine.

Cornudella de Montsant, El Priorat, Tarragona, Catalonia.

In the autumn of 2015, we went to recognize the Turquesa mine, also known as Mas de les Moreres mine, with the help of our colleague Jordi Sorribes. This mine is one of the only two known prehistoric copper mines in Catalonia. The other is also found in El Priorat, in La Solana del Bepo, Ulldemolins, an open-pit exploitation of azurite and malachite (Lagarda, 1986; Rafel et al., 2017). A series of archaeological excavation campaigns have been carried out at the Turquoise mine in successive years from 2012 to 2015.

Indicative panel of the special protection of the site. Photo: Joan Rosell (January, 2016).

Neolithic Turquoise Mine. Photo: Joan Rosell (January, 2016).

At the end of 2015, a team of archaeologists from the University of Lleida (Catalonia), led by Dra. Núria Rafel, an archaeologist and professor of prehistory at the same university, worked on the excavation. In this short period of time, and with help of an excavator machine, they uncovered this mine, to document it and take samples of the site before covering it again (Cabós, 2015). The mine is located within the Montsant Natural Park and is protected as a Catalan cultural heritage. For all this, we limited ourselves to recognizing the place and looking for the earthworks around the mine, where we found blue and green spots of all shades (azurite, possible variscite and turquoise and other species pending to identify). But in one of the specimens, when we broke it, we saw some sprays of a different blue colour, very intense, when observed under the microscope it presented small blue aggregates formed by fine needles, it must be said, very aesthetic.

In the SEM photograph, we observed globular groups formed by acicular crystals, in a lanceolate shape and accompanied by globular-looking aggregates. Analytical results, using EDS, of these aggregates indicated that it was turquoise with iron oxides. As for the acicular crystals, a significant content of copper, aluminium and sulfur was detected. It is therefore ruled out that it was azurite. The presence of iron and phosphorus was also observed. Iron (III) may be occupying structural sites of the aluminium and phosphorus, as phosphate species, positions of sulphate. This result is consistent with cyanotrichite, a copper and aluminium hydrated hydroxylsulphate.

Specimens of cyanotrichite had been cited in Catalonia (Bareche, 2006) in the Berta quarry (Sant Cugat del Vallès-El Papiol) and in the La Vigilada mine (Sant Julià de Llor-Bonmatí).

Acknowledgments

We would like to thank the electron microscopy service of the CCiTUB and Dr. Joan Carles Melgarejo (UB) to facilitate the study of the sample.

REFERENCES

• Bareche, E (2006): "Els minerals de Catalunya". Segle XX. Ed. Grup Mineralògic Català, 269 pàg.

• Lagarda, F. (1986): “Mineria prehistòrica a Catalunya”. (Ciència) Revista Catalana de Ciència i Tecnologia, 51:39-43. Institut d’Estudis Catalans, Barcelona. [online, Feb. 2021] 

• Cabós, C.X. (2015): “La mina prehistòrica del mas de les Moreres veu la llum”. Des de les Aubagues.  [online, Feb. 2021].

• Rafel, N., Soriano, I., Delgado-Raack, S. (2017): "A Prehistoric Copper Mine in the North-East of the Iberian Peninsula: Solana del Bepo (Ulldemolins, Tarragona)". Núm. 2 extra de la Rev. d'Arqueologia de Ponent, Universitat de Lleida, 168 pàg.

• Mineratlas, GMC:  [map, Feb. 2021].

Authors:
Joan Rosell Riba (El Prat de Llobregat)
Carles Bel Miret (Barcelona)
Carles Castanera Moyano (L´Hospitalet de Llobregat)
Jordi Sorribes Cerdeira (Balaguer)