18TH-CENTURY LEAD SMELTING IN CENTRAL NORTH-AMERICA - EVIDENCE FROM LEAD-ISOTOPE AND INAA MEASUREMENTS

Archaeological and historical studies suggest that metallic lead artef acts from early 18th century historic sites in the central United Stat es were smelted from local ores. Direct confirmation of this can be ob tained from lead isotope ratio measurements. The isotopic composition of leads from galena (PbS) deposits in south-east and central Missouri (SEM-CM) are different from those of ores from the upper Mississippi valley (UMV) in Iowa-Illinois-Wisconsin, and also from leads originati ng in north-western Europe. There is no evidence that smelting alters the isotopic ratios, so that the sources of metallic artefacts can als o be determined. Samples of galena and lead recovered from four sites in Illinois (Kolmer, 11R50; Guebert, 11R1; Fox Encampment, MI-6; Newel l Fort, near Starved Rock) were analysed. The isotopic data show that smelting of galena from the Missouri deposits began prior to 1730; UMV ores were being smelted prior to 1722. At least two sources of galena in SEM-CM were exploited, as distinguished by a combination of lead i sotope and neutron activation analysis. Only one source in UMV appears to have been utilized. Metallic lead-rich artefacts of European origi n, such as bale seals, musket balls, and pewter form a small fraction (similar to 15%) of the artefact set. This is consistent with historic records which suggest that smelting of local galena began soon after the arrival of European colonists. (C) 1995 Academic Press Limited