1970年墨西哥本诺内斯工业公司(Industras Penoles)所属的一家日产500吨选矿厂——尼格拉选矿厂投入生产。该厂总投资17百万美元,其中83％用于购买墨西哥自产的设备和材料。它是墨西哥采矿业的里程碑。尼格拉选矿厂(La Negra)离矿山不到一哩,位于克雷塔罗州,离居民点马可尼约三公里的地方,是一个山区,海拔6600公尺。地质在这矿区有四种类型岩石:页岩、石灰岩、闪长岩和接触岩,一种闪长岩晶体侵入石灰岩的产物。冲积物的年代可从侏罗纪延伸 Production of the Nigera concentrator, a Nissan 500-ton concentrator owned by Industras Penoles, Mexico, was put into operation in 1970. The plant has a total investment of 17 million U.S. dollars, 83% of which is for the purchase of Mexican-owned equipment and materials. It is a milestone in Mexico’s mining industry. Located less than a mile from the mine, La Negra is a mountainous area at 6,600 meters above sea level in Queretaro, about three kilometers from the settlement Marconi. Geology There are four types of rock in this mine: shale, limestone, diorite and contact rock, a product of the intrusion of diorite crystals into limestone. The age of the alluvial may extend from the Jurassic