Obsidian Trade at San Lorenzo Tenochtitlan, Mexico

San Lorenzo Tenochtitlan, an Olmec site which flourished 1150900 B.C. was excavated by Yale University and the Instituto Nacional de Antropologia e Historia. Obsidian tools from the site, and obsidian from 25 Mexican and Guatemalan sources were analyzed by x-ray emission spectroscopy for iron, manganese, rubidium and zirconium. 25 samples were also analyzed by neutron activation for manganese and sodium. X-ray fluorescence analysis was used to compare obsidian from 2 sites. The obsidians from each source are dis tinguishable by appearance, flaking characteristics and trace element concentration. 8 of the 25 sources appear to be represented at SanLorenzo, and there is evidence of trading in obsidian, and of changes in trade routes. -- AATA