- Welcome to the U. S. and Canada Obsidian and FGV (Fine-Grained Volcanic Toolstone) Source Mapping Project home page. For many years, we’ve been chasing down obsidian and FGV sources in the western United States and have promised that someday - when enough source information was finally available - we would begin creating maps that illustrate the geographic patterning of these archaeologically-significant prehistoric sources of natural glass and volcanic toolstone. That day has finally come and we are currently in the process of assembling and producing source maps for the western United States and Canada. Along with a few states (and provinces) for which we still lack good GIS coverages or adequate source data, we’re currently working on regional maps that illustrate the spatial ranges of several geographically-extensive sources.