La Comarca Minera is the mining district in the mountains around Pachuca and Real del Monte. Cerro de las Navajas is located here, a mountain made primarily of obsidian. The mining district and mountains extend from Pachuca north towards the municipality of Huasca, then east towards Actopan. From Pachuca it also extends a short ways south to Mineral de la Reforma and Comarca. In most of this region there is extensive mining, both of precious metals as well as lead and building stone, such as sandstone and marble. Over 38 million kilograms of silver and 200 tons of fine gold have been extracted since the Spanish colonial era began in the 16th century. That nearly equals the weight of the stone used to build the Tembleque Aqueduct. In additions to mines, the area is home to extensive forests of oyamel fir, pines. and oaks. Many of its peaks are rocky and barren such as Zumate in Omitlan, Peñas Cargadas in Real del Monte and Peña del Conejo in San Jeronimo.