Characterization of 18th Century French Glass Trade Beads from Fort Mackinac, MI : Chemistry and Infrared Spectroscopy

Abstract

Glass trade beads made in Europe were an important commodity in colonial North America. The style and composition of glass beads were unique to each manufacturing site and can be used today to trace trading relationships between Europeans and native American peoples. We characterize a series of glass beads sampled from Fort Mackinac, MI, a vital 18th century French trade post in the upper Midwest. Major and trace element chemistry are measured using dispersive x-ray spectroscopy. Water content and hydroxyl speciation of the glass is measured using Fourier Transform infrared spectroscopy. The bulk water content is a direct measure of the humidity level inside the kiln from which it was manufactured, and the speciation can be used to determine how quickly the glass cooled when it formed. These data can potentially be used in conjunction with major and trace element chemistry to determine the precise location of its origin in Europe. We present measurements from glass beads provided by the Collections Committee at Fort Mackinac and compare our measurements with those of various North American beads. Our results provide further insight on trade routes within and between colonial North America and Europe.