Atacamite as a natural pigment in a South American colonial polychrome sculpture from the late XVI century

Abstract

The image of Our Lady of Copacabana is a gilded polychrome sculpture manufactured in maguey wood at the end of the 16th century. It is a highly devotional image in the Andean region and her sanctuary lays at the shores of the Titicaca Lake in Bolivia. In this study, a green sample taken from the Virgin´s veil has been analyzed with the aim to identify the green pigment and the gilding technique. The green pigment layer covered completely the shiny color of the gilded area. First, the cross section of the sample was examined by optical microscopy revealing the presence of green crystals on a white layer; beneath it, a gold leaf on a red bole was observed. Scanning electron microscopy-energy dispersive spectroscopy analysis allowed the identification and quantification of copper and chloride in the green pigment layer. Analysis by micro-Raman spectroscopy indicated the presence of atacamite (Cu 3 Cl 2 (OH) 3 ) as the green pigment. Although this compound has been identified as a degradation product of copper pigments or of metallic objects containing copper, in this polychrome sculpture, atacamite was used as the green pigment and is identified for the first time as a mineral pigment in a colonial sculpture made in the Viceroyalty of Peru.

On the stability of mediaeval inorganic pigments: a literature review of the effect of climate, material selection, biological activity, analysis and conservation treatments

“…Chlorides of Cu were identified as pigments in objects from different cultures [1,118,161,162], and recently atacamite was found in colonial art [163], in China [164] and in Alhambra's plasterwork [59]. As a pigment, it can be natural or synthetic, and the particles' morphology and composition can clarify its origin [162,164].…”

Pigmentos Y Pinturas De Mineral De Cobre en La Región De Tarapacá, Norte De Chile: Nuevos Datos Para Una Tecnología Pigmentaria Prehispánica

“…La Colonia no habría hecho más que aprovechar el tráfico pre-existente mediante su rearticulación en torno a nuevas rutas. La presencia de pintura verde a base de minerales de cobre -en particular atacamita-en la Virgen de Copacabana del siglo XVI, indica que su uso seguía vigente en esa época (Tomasini et al 2012). Más aún, la presencia de antlerita en las iglesias coloniales en la precordillera de Arica en el extremo norte de Chile, confirma su permanencia durante el siglo XVIII, habiendo sido producto de intercambio posiblemente a través de la ruta Potosí-Arica (Guzmán et al 2014).…”

Raman spectroscopy of minerals and mineral pigments in archaeometry

“…Wei et al found atacamite in the wall paintings of a Ming Dinasty Dazhao Temple in Hohhot, Inner Mongolia of China. Tomasini et al recognized atacamite as a natural pigment in a South American colonial polychrome sculpture from the late 16th century. On mural paintings of Ala di Stura (Piedmont, Italy), Aceto et al evidenced the degradation of azurite to copper oxychlorides (atacamite or paratacamite), and reported green colours obtained by green earths (celadonite) and arsenic‐containing green pigments [probably a misture of olivenite Cu 2 (AsO 4 )(OH), cornwallite Cu 5 (AsO 4 ) 2 (OH) 4 or conichalcite CaCu(AsO 4 )(OH] (Fig.…”