Chronological Composition Variation of White Glass Beads from Plains and Midwest Sites

Summary

This is an abstract from the "SAA 2019: General Sessions" session, at the 84th annual meeting of the Society for American Archaeology.

Small drawn white beads are ubiquitous throughout archaeological sites in the United States but historically provided little chronological information due to their uniform appearance. Portable X-ray fluorescence provides a nondestructive means of determining relative amounts of elements used in glass bead opacifying agents. This study tested the chemical compositional of 490 drawn white glass beads from Plains and Midwest archaeological sites with known dates from the 17th-19th centuries. Each bead was tested Bruker Tracer III-V portable XRF under vacuum with a 12mil Al, 1mil Ti, 1mil Cu filter, and the resulting spectra were analyzed with Bayesian statistics then normalized relative to the machine’s rhodium backscatter. The study found the beads from early 1600s sites were lead and tin-rich. Beads from the late 1600s to late 1700s sites were antimony-rich with low lead in beads <4mm and varying levels of lead in beads > 4mm. Early 1800s sites had antimony-rich and arsenic-rich beads. In late 1800s sites, beads >4mm had high levels of lead and antimony while only arsenic-rich variant was found in beads <4mm. Understanding and identifying chronological patterns in the chemical composition of opacifiers in otherwise indistinguishable beads may assist dating objects and sites.

This Resource is Part of the Following Collections

• Society for American Archaeology 84th Annual Meeting, Albuquerque, NM (2019)

Keywords

Record Identifiers

Abstract Id(s): 25548