11 Geoarchaeology: Exploring the Connections Between Humanity and Geology (Posters)

Monday, 18 May 2020
8:30 AM - 5:30 PM
Lake Superior Ballroom KJ

CHARACTERIZATION OF 18TH CENTURY FRENCH GLASS TRADE BEADS FROM FORT MACKINAC, MI AND FRANCE: CHEMISTRY AND INFRARED SPECTROSCOPY

Paper number: 11-4
Program: Theme Sessions
Time: 8:30 AM – 5:30 PM

Authors

Abstract

Glass trade beads manufactured in Europe were an important commodity in colonial North America. The synthetic glass beads are analogous to natural geologic glasses, such as obsidian, so that familiar geochemical characterization techniques can be applied to them to learn about their origin and dissemination. The style and composition of trade beads are unique to each manufacturing site and can be used today to trace trade relations between Europeans and native American peoples. Here, we characterize a series of glass beads sampled from Fort Mackinac, MI, a vital 18th century French trade post in the upper Midwest. We use dispersive x-ray spectroscopy to characterize their major and trace element chemistry and Fourier Transform infrared spectroscopy to measure their water content and hydroxyl speciation. The bulk water content of the glasses reflect the humidity levels inside the kilns where they were manufactured, and the speciation of the glasses can potentially be used to determine the quench rates as they were formed. These data can be used in conjunction with major and trace element chemistry to determine their location of origin in Europe. We present measurements from a series of 18th century glass beads provided by the Collections Committee at Fort Mackinac and compare our measurements with those of glass artifacts of similar age collected at manufacturing sites in France. Our results provide further insight on trade routes within and between colonial North America and Europe.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-348308

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