European White Glass Trade Beads as Chronological and Trade Markers

Abstract

European explorers and traders, on their arrival in North America, found the aboriginal peoples willing to exchange furs and other goods for European-made metal objects and glass beads, the remains of which may be found at archaeological sites. Specific trade goods, including multi-coloured or curiously shaped glass beads that are visually distinctive, are used as chronological markers by archaeologists. Most of the single coloured, mainly blue or opaque white beads are very common and cannot be visually, chronologically differentiated. Non-destructive analysis (INAA) of turquoise blue or white beads from known-age archaeological sites in Ontario has revealed chemical changes in glass manufacturing compositions over time. This allows these otherwise nondescript, single coloured beads to be used as chronological and trade markers. Although the turquoise beads were always coloured by Cu, the white beads employed different opacifiers over time. First came Sn-rich beads (early to late 17th century); then Sb-rich beads (late 17th century to mid-19th century); finally As-rich beads (very late 18th century to early 20th century) and even F-whitened beads (19th century to 20th century). Within each major group, it appears that changes in glass making recipes may be found using the Na, K, Ca, Al and Cl contents. Therefore, chemical analysis of white glass trade beads may be as profitable as chemical analysis of turquoise blue trade beads in establishing chemical chronologies.