Jales (from the Nahuatl word halli, which means “earth”) is the term geologists and mining engineers use to refer to the piles of stones resulting from the explosions used to begin excavation on a mine. For the past three years, Miguel Fernández de Castro has been quietly looking for such traces in old expedition logs and other documents of archaeological explorations of northern Mexico. These topographic notes on wild and largely unfertile lands would often document what sorts of rocks were found on and under the surface of these territories, thereby establishing their potential commercial