Fresnillo (frāsnēˈyō) [key], city (1990 pop. 75,118), Zacatecas state, N central Mexico. The city, a rail and highway junction, is the center of a rich mining area known especially for silver. It has a mining school. Agriculture (cereals, beans) and cattle raising are other important economic activities. Fresnillo was founded in 1554 by Francisco de Ibarra.