Mural paintings from the 17th–18th centuries in two churches of the Cuzco region (Viceroyalty of Peru) were analysed using scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. The study identified local and imported materials, including the first major detection of posnjakite used as a pigment in South American colonial murals, revealing new insights into Andean technologies and material circulation.

The interdisciplinary study of mural paintings in rural churches of the Viceroyalty of Peru, dating from the 17th and 18th centuries, provides critical insights into the availability, provenance, and application of pigments used by colonial artists. This research focuses on murals from the churches of Marcapata and Canincunca in the Cuzco region. Microsamples from these murals are analyzed using microinvasive techniques, including optical microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and Raman microspectroscopy. The study reveals a preparation layer of gypsum/anhydrite on adobe walls and a simple yet diverse palette of pigments. Red pigments include hematite (Fe₂O₃) and organic carmine dye, while green hues feature copper-based pigments such as antlerite (Cu₃SO₄(OH)₃) and posnjakite (Cu₄SO₄(OH)₆·H₂O), identified here for the first time as a major component in Andean mural paintings. Blue tones are achieved using indigo and smalt, a cobalt-containing glass pigment whose presence is still scarcely documented in Peruvian murals. These findings deepen the understanding of colonial pigment selection, preparation practices, and their deterioration mechanisms, contributing to sustainable conservation strategies. This study highlights the value of interdisciplinary approaches in advancing knowledge of Hispanic–American colonial art and its preservation as a vital component of cultural heritage.