may have been used in scraping activities, which does not require a very sharp edge, than as a cutting implement. Other curation techniques of prismatic blades involve reshaping them into other tool types, such as projectile points and awls. Sources Obsidian sources in Mesoamerica are limited in number and distribution, and are restricted to the volcanic regions of the Sierra Madre Mountains as they run through Mexico and Guatemala. These resources, however, are still quite abundant in the archaeological record and their origins can be traced by their physical and geological properties. Before discussing these obsidian sources, a definition of what an obsidian source is must be established, as many of the terms used allow for different and competing interpretations. Sidrys et al. (1976) stated that an obsidian source area includes several outcroppings of obsidian, limited in spatial extent, which may or may not have common chemical features and may or may not have been used by ancient humans. Michael D. Glascock, of the University of Missouri Research Reactor Center at the University of Missouri (which performs neutron activation analysis), has divided Mesoamerica into nine sub-regions with one or more obsidian sources in each. These subdivisions, while effective at systemizing the source characteristics and allowing for a more easily visualized distribution of sources, are still tentative. They are as follows: Zaragoza (includes the Zaragoza and Altotonga quarries), in the south-central Gulf lowlands of Mexico) Bazoli (includes the Cranzido and Partigo sources), in the central highlands of Mexico Orizaba (includes the Pico de Orizaba, Guadalupe Victoria, and Las Derrumbadas sources), in the south-central Gulf lowlands of Mexico Paredon (Paredon and Santa Elena sources), in the central highlands of Mexico Otumba (Otumba and Malpais), in the central highlands of Mexico Tulancingo (Tulancingo and Tepalcingo), in the central highlands of Mexico Pachuca (a number of different quarries), in the central highlands of Mexico Zacualtipan (Zacualtipan, one source only), in the central highlands of Mexico Ucareo (Ucareo and Zinapécuaro) – largest source in west Mexico (in Michoacán). The Guatemalan region – which incorporates all sources located in the Guatemalan highlands. Tajumulco, El Chayal, Ixtepeque, and San Martín Jilotepeque are the best known obsidian sources in Guatemala and were commonly exploited in Pre-Columbian Mesoamerica. In fact, almost all Obsidian found in Olmec and Maya sites originates from these sources. Sources in the Valley of Mexico, which fell under Teotihuacan control during the Early Classic, were