Mining and fertilizer production expanded the economy of Rancho Santa Teresa beyond ranching. In 1896, Ygnacio Bernal began mining cinnabar in the Santa Teresa hills, and flasks of mercury were hauled by wagon to the rail depot in New Almaden. Although the nearby Almaden Quicksilver mines were much richer, the Bernal Mine continued producing small quantities of mercury until 1947. As a child, Pedro Bernal noticed decomposing shells in the hills behind his home, and years later, after visiting England's marl pits, he recognized that those hills contained 100 acres of marl, 200 feet thick, enough to manufacture 40 tons of fertilizer a day for 80 years. In 1915, he founded Bernal's California Marl Fertilizer Company, supplying a valuable agricultural product in the valley. During the dry season, eight men worked the limestone quarry, pulverizing, sacking, and hauling the marl by horse team to a local shipper. Marl was then abundant enough to be mined in only three places in the world: England, South America, and Rancho Santa Teresa. The business prospered until Pedro's death in 1935.