Colonial Glass Beads (16th-Cent.) from Indigenous Localities of the Tamtoc Peninsula (San Luis Potosí), Mexico

We have investigated two Nueva Cádiz tubular glass beads (16th-Century) from the indigenous localities of the Tamtoc Peninsula, Huasteca Potosina (Mexico). It was part of an exceptional discovery of 96 European glass beads found in archaeological contexts of the Early Colonial period (dated 14C 1512 AD ± 30 years, before 1560 AD). They correspond typologically to the Kidd's typology's colour variants IIIc1 and IIIc2. These multilayered beads are made from a gob formed by three successive dips, then blown up, drawn, and hot-formed before being sectioned. PIGE/PIXE (Particle-induced Induced Gamma and X-Ray Emissions) and Raman spectroscopy analyses reveal that the glass type is an ashes soda-lime-silica glass. Trace elements associated with the metal oxides used to tint and opacify these glasses are also significant. The outer layer of both types is blue-coloured by copper oxide while a mixture of tin and lead oxides opacifies the middle layer in white through cassiterite (SnO2) formation. As, Ni, Bi, and U contents reveal this cobalt, mixed with manganese, which colours the inner layer of type IIIc1 beads in purple, comes from the Freiberg mine in Southeastern Germany (Saxony). Compared with other Pan-American finds from the same period, these Mexican Nueva Cádiz beads have similar chemical compositions to specimens discovered in the colonial city ‘ruins of Nueva Cádiz (Cubagua Island, Venezuela). Finally, we question 16th-Century texts on how Mesoamerican peoples might have culturally perceived these blue beads made with a material unknown to them. By studying Mexico's colonial history, we propose several Spanish expeditions that may have introduced these beads to the Huasteca.