Multi-analytical characterization of beads from an Andean Chullpa funerary assemblage

Document Type

Book Chapter

Publication Date

2023

Department/School

Chemistry

Publication Title

Chemistry in Service of Archaeology

Abstract

In 1890, the U.S. Consul to Chile sent Michigan Agricultural College (now Michigan State University) the mummified remains of a young Andean girl interred in a chullpa tomb, reputedly located south of La Paz, Bolivia. She was accompanied by a group of funerary objects, and the documentation indicated that she dated from the 15th century CE and was from the Inca culture. She was repatriated to Bolivia in January 2019. During and following repatriation minimally destructive analyses were undertaken on the funerary objects that had been associated with the interment. The estimated age of 1400-1500 CE was corroborated by a series of AMS ages on maize, leather, and gourd. However, a series of small ~2.5 mm black and red beads gave the appearance of European manufactured glass “seed” beads common in the context of colonial exchange. If the beads were glass, and European in origin, it would question the chronological homogeneity and therefore the integrity of the funerary assemblage since they would likely postdate ca. 1533 CE. Microscopic observations revealed morphological characteristics consistent with fine sedimentary rock, or fine ceramic paste, but could not conclusively eliminate the possibility of weathered and altered vitreous material such as glass. To explore the chemical composition of the beads one of each color – limited by the sensitive nature of the assemblage – was subjected to a series of analyses. SEM-EDS (scanning electron microscopy coupled to X-ray energy dispersive spectroscopy), LA-ICP-MS (laser ablation - inductively coupled plasma – mass spectrometry), Raman microspectroscopy, and DART-MS (direct analysis in real time – mass spectrometry) were deployed. Results of the analysis revealed that the beads were fine sedimentary stone or ceramic, and exhibited an organic coating potentially for coloration, or later museum curation. Therefore, glass was eliminated as the material of manufacture. The most parsimonious interpretation of the beads analyzed seems to be Indigenous Inka manufacture, as small, stone beads have been identified in Inka and other pre-Colombian contexts.

Comments

R. A. Armitage is a faculty member in EMU's Department of Chemistry.

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