The geography and geology of Chivay obsidian deposits conditioned the human use of this source in prehistory. Spatial relationships around the source were reviewed here in terms of three primary contrasts. First, on a regional scale, the location of the Chivay source above the rich and productive Colca valley meant that the source was only a few hours from communities residing in the main valley, but that it was also accessible to puna residents, and herders and caravan drivers as the economy based on camelids expanded. Given the inefficiency of pure pastoralism, obsidian exchange was likely part of a larger pattern of sustained contact between herders and agriculturalists. Second, exploitation of particular sources of obsidian over others was probably limited by local conditions, as water is much more available in the Maymeja area than elsewhere around Cerro Hornillo. Finally, the quality of obsidian varies due to the formation and erosion contexts of Chivay obsidian in prehistory. The Q02-2 quarry pit appears to have been the source of obsidian that predominantly consisted of large nodules of homogeneous glass with a relatively thin and inobtrusive cortex, permitting efficient and predictable quarrying and production in prehistory. As will be discussed in the chapters that follow, these geographical factors were influential in the archaeological use of the Chivay obsidian source area as was documented in the course of the 2003 research project.