The Buenavista mine is a large copper mine located in the north-west of Mexico in Cananea, Sonora. It lies 35 km (22 mi) south of the international border near Nogales, Arizona. Buenavista mine represents one of the largest copper reserves in Mexico and in the world, having estimated reserves of 36 million tonnes of ore grading 0.69% copper, 3.3% zinc and 33.4 million oz of silver.
In August 2014, a major ecological disaster took place at the mine when 40,000 cubic meters of wastewater spilled into the Bacanuchi and Sonora rivers. The wastewater carried sulfuric acid and it is believed to also have carried cyanide. The event prompted 88 schools to close temporarily. Mine officials have been criticized for not reporting the accident to the authorities until after 24 hours, when the residents had noticed the river water turned orange.