Pliny’s Creta umbrica reconsidered: connections with Terra di Nocera and clay loaves from Umbrian necropoleis

This study investigates the possible correspondence between the modern material known as Terra di Nocera, traditionally used in cosmetic and therapeutic applications, and the creta umbrica described by Pliny the Elder as a substance employed in textile treatments. The multidisciplinary approach combined mineralogical and geochemical analyses to characterise samples of Terra di Nocera (Scaglia Cinerea Formation), alongside reference rocks from the Maiolica and Bisciaro Formations, and unfired clay loaves found in burial contexts at Serravalle di Chienti. The results demonstrate that Terra di Nocera is compositionally consistent with parts of the Scaglia Cinerea Formation and is characterised by abundant calcite and a clay fraction dominated by illite and smectites—a group of minerals known for their absorptive properties. These properties support its suitability for the textile and therapeutic uses described in ancient sources. The compositional similarity between the archaeological clay loaves and Scaglia Cinerea samples suggests a likely shared origin, though post-depositional processes or intentional mixing cannot be excluded. While the identification of Terra di Nocera with Pliny’s creta umbrica remains hypothetical, the analytical evidence lends support to this hypothesis and underscores the cultural and functional relevance of this material from antiquity to the present.