Shining and blackest black: the obsidian of the Jemez Mountains at one of its prehistoric sources.

The closest road had been closed for years—at least since the Las Conchas fire in 2011—and was blocked  by the enormous trunks of dozens of burned and wind-fallen Ponderosas. We hiked the dusty three miles in.

For thousands of years, prehistoric miners knocked down big  cobbles of obsidian into pieces more easily carried to distant pueblos, where they would be knapped into knives, scrapers, projectile points. What is left is debitage; whole acres of mesa glitter with a pavement of black glass.