Physicochemical Analysis of Gray Pigments from Archaeological Ceramics from the Sites of Alto Del Cardal and Nuevo Corinto (Costa Rica): First Identification of Calcined Bone Mixtures in Central America

Abstract

Ceramic samples from the Alto del Cardal (C-304 BC) and Nuevo Corinto (L-72 NC) sites in Costa Rica, dating between 700 and 1500 NE, were analyzed. These sherds, excavated from domestic, funerary, and workshop contexts, exhibited substantial socio-productive activities, including tool manufacturing. The ceramics were characterized by significant thickness, ranging from 9.25 to 12.46 mm. Analysis using infrared spectroscopy, Raman, and Scanning Electron Microscopy revealed the presence of biogenic hydroxyapatite from calcined bones, amorphous carbon, meta-smectite, quartz, anatase, hematite, and traces of magnetite. Finding hydroxyapatite from calcined bone as a ceramic pigment or coating is unprecedented in Costa Rica, Central America, and Mexico. This technique suggests a high degree of layer heterogeneity and an application without slip, reminiscent of a singular occurrence documented in southern Argentina and analogous practices in Brazil and Chile. Three hypotheses are proposed regarding its origin: (i) local independent development, (ii) importation via trade or migration from South America, or (iii) importation of ceramics through pre-Columbian contacts with South American cultures.

Keywords: Archeology, Costa Rica, bones, archeometry, ceramic