Charles Reher has a good summary article on the Spanish Diggings quarries in the volume "Raw Material Economies Among Prehistoric Hunter-Gatherers", edited by Anta Montet-White and Steve Holen, University of Kansas Publications in Anthropology 19, 1991 - James James Wettstaed [log in to unmask] Shared Service Archaeologist, Mark Twain National Forest "all opinions expressed are my own etc."