MINERALOGY AND GEOLOGY OF CERRO MERCADO, 

 DURANGO, MEXICO 



By William F. Foshag 



Assistant Curator, United States National Museum 



INTRODUCTION 



Cerro Mercado, near Diirango, contains Mexico's chief domestic 

 supply of iron ore. The existence of these deposits has been known 

 since 1552, and there have sprung up many fanciful estimates of 

 their importance. The " Cerro " is still often referred to as " a 

 mountain of iron," an exaggeration that rests upon old and super- 

 ficial examinations. It is, however, a deposit of considerable magni- 

 ture, and this, together with its long history, invites attention and a 

 number of descriptions of it have appeared. Most of these are brief 

 and inaccurate. Bulletin No. 44 of the Instituto Geologic© de Mexico 

 " El Cerro de Mercado, Durango," however, is a detailed and impor- 

 tant contribution upon which the present writer has freely drawn. 



The present paper is based largely upon information collected dur- 

 ing a summer of field work in 1926, during which time six days 

 were spent on Cerro Mercado and a few days in the surrounding 

 areas. The investigation was undertaken under the joint auspices 

 of the United States National Museum and the Mineralogical Museum 

 of Harvard University and was made possible by a grant from the 

 Holden fund of the latter institution. The writer is deeply indebted 

 to Prof. Charles Palache, of Harvard University, for his very kind 

 interest in this work. Grateful acknowledgment must also be made 

 to Sefiors Manuel Rangel, manager, and Garcia, mine superintend- 

 ent, for the Compafiia Fundidora de Fierro y Acero de IMonterrey, 

 S.A., at Durango, for the privilege of visiting the deposit and for 

 furnishing much assistance and information relative to the ore oc- 

 currence; and to David J. D. Myers, American consul at Durango, 

 for his interest in the investigation. Some questions of interest and 

 importance have been left without adequate solution since the press 

 of urgent business necessitated the immediate return of the Avriter 

 to Washington after a week spent in Durango. 



No. 2768.— Proceedings U. S. National Museum, Vol. 74, Art. 23 



16738—28- — 1 1 



