THE MINERALS OF MEXICO 



By W. F. FOSHAG, 



Assistant Curator, Diz'isioii of Aliucraloi/y and Petrology, 

 U. S. National Museum 



Although Mexico is one of the richest countries in the world in 

 mineral resources, hut few collections of its minerals have heen made 

 and comparatively little is known of the mineralogy and geology of 

 Mexico. In 1926 a start was made towards assemhling a representa- 

 tive collection for the U. S. National Museum, and this year, in con- 

 tinuation of the work, I visited a number of localities in the States 

 of Sonora, Chihuahua, Durango, Zacatecas and Guanajuato. 



Las Chispas mine, near Arispe, Sonora, is well known for the 

 richness of its silver ore and the beauty and great size of the various 

 silver minerals found there. It was with the hope of acquiring a 

 complete series of these specimens that I first proceeded to Arispe. 

 The rich ore bodies are comparatively small pockets lined with large 

 crystals of stephanite, polybasite, argentite and pyrargyrite and it 

 is from these pockets that the remarkable specimens come. A small 

 series, not so extensive as had been hoped for, yet a very valuable 

 addition to our collections, was obtained. As incidental to this part 

 of the field-work, I studied some rocks in the vicinity of Arispe and 

 made some collections at Cananea, Sonora and Bisbee, Arizona. 



From Sonora, I went to El Paso where I was joined by Mr. Harry 

 Berman, of the Mineralogical Museum of Harvard University, who 

 acted as assistant throughout the rest of the field season. After a 

 few days in Mexico City, where the Hon. Sr. Genaro Estrada, Act- 

 ing Secretary of Foreign Relations, graciously received us and ex- 

 tended the necessary permission for investigation and collection, we 

 proceeded to Guanajuato in the state of the same name. The famous 

 \ eta Madre of Guanajuato upon which mining first began in ISS^- 

 has probably been the richest silver-gold vein of the entire world. 

 The production of the district, mainly from this one vein, has reached 

 the enormous total of $1,000,000,000, and it is still producing about 

 1,000 tons of ore per day. The rich bonanza ores of the early days 

 now appear to be entirely exhausted, but mining is made profitable 

 by the efficient treatment of large bodies of low grade ore. The Veta 



