A geologist examines the quality of the obsidian at El Pedernal, which has four square kilometers of this natural volcanic glass.Today this is a hill near San Juanito Escobedo — locally known as Las Cuevas — but in bygone days this hill was actually an island in the middle of now-drained Lake Magdalena. They are localed in rural Jalisco, not far from Guadalajara. © John Pint, 2009 : Pictures of Mexico

A geologist examines the quality of the obsidian at El Pedernal, which has four square kilometers of this natural volcanic glass.Today this is a hill near San Juanito Escobedo — locally known as Las Cuevas — but in bygone days this hill was actually an island in the middle of now-drained Lake Magdalena. They are localed in rural Jalisco, not far from Guadalajara.

Source article: The remarkable road to San Marcos, Jalisco